WO2012171009A1

WO2012171009A1 - Compact endocavity diagnostic probes with rotatable detector for enhanced nuclear radiation detection and 3d image reconstruction

Info

Publication number: WO2012171009A1
Application number: PCT/US2012/041909
Authority: WO
Inventors: Yonggang Cui; Aleksey Bolotnikov; Ralph James
Original assignee: Brookhaven Science Associates, Llc
Priority date: 2011-06-10
Filing date: 2012-06-11
Publication date: 2012-12-13

Abstract

The invention relates to an apparatus and a method for imaging tissue or an inanimate object using the novel probe with a rotatable solid-state semiconductor detector and a complete readout electronics circuitry. More particularly, the present rotatable radiation imaging probe is configured in a manner that allows the probe to be placed in close proximity to an object or tissue of interest to be imaged even if the boundaries of the object exceed the field of view of the detector. By precisely rotating and/or linearly translating the detector within the probe in one of the desired directions along x-, y- or z-axis, a plurality of images can be generated and co-registered into one or more image(s). In addition, the image series obtained during the rotation process can be used in three-dimensional image reconstruction.

Description

COMPACT ENDOCAVITY DIAGNOSTIC PROBES WITH ROTATABLE DETECTOR FOR ENHANCED NUCLEAR RADIATION DETECTION AND 3D IMAGE

RECONSTRUCTION CROSS-REFERENCE TO A RELATED APPLICATION

[0001] This application claims the benefit under 35 U.S. C. 119(e) of U.S. Provisional

Application No. 61/495,695 filed on June 10, 2011, the content of which is incorporated herein in its entirety.

STATEMENT OF GOVERNMENT LICENSE RIGHTS

[0002] The present invention was made with government support under contract number DE-AC02-98CH10886 awarded by the U.S. Department of Energy. The United States government has certain rights in this invention.

FIELD OF THE INVENTION

[0003] This invention relates to the field of radiation imaging. In particular, the invention relates to an apparatus and a method for imaging tissue, such as the colon or prostate, or an inanimate object using a rotatable probe that has an integrated detector(s) and a complete readout electronics circuitry.

BACKGROUND

[0004] In medical imaging applications, two competing technologies are generally used: ultrasound and nuclear medical imaging. The benefits of the ultrasound technology are that it enables a very compact design of a probe and is powerful in revealing the anatomical structures of the organs. However, the ultrasound technology is not an ideal tool in cancer detection and diagnosis because the ultrasound technology can only generate anatomical images, whereas functional images are needed, especially for the detection and localization of cancerous tumors at an early stage. For example, in prostate cancer diagnosis, the ultrasound probe produces and subsequently records high-frequency sound waves that bounce off the prostate's surface, and transforms the recorded sound waves into video- or photographic- images of the prostate gland. The probe generates images at different angles to help the physician estimate the size of the prostate and detect abnormal growths. However, benign and cancerous tumors cannot easily be distinguished by ultrasound. In addition, if the patient had radiation treatment in or around the prostate before, the fibrous tissues can be mistakenly identified as tumors during the interpretation of the sonograms. Hence, while the ultrasound probes can be designed to be very compact and easy to carry, handle and operate, their inability to distinguish benign and cancerous tumors makes them unsuitable for functional imaging required in diagnosis, cancer imaging, and image-guided treatments.

[0005] By contrast, the traditional diagnostic nuclear medical imaging techniques have the capacity to provide the desirable functional images. Such methods use radioactive tracers, i.e., short-lived isotopes, which emit gamma rays from within the body and are linked to chemical compounds, permitting the characterization of specific physiological processes. The isotopes can be given by injection, inhalation, or by mouth. Traditionally, an imaging device, such as an Anger gamma camera, which is described in U.S. Patent No. 3,011,057 and incorporated herein by reference, is used to image single photons emitted from an organ. The camera builds up an image of the points where radiation is emitted. This image is then enhanced by a computer, projected on a monitor, and viewed by a physician for indications of cancer. Exemplary commercial nuclear imaging systems that are capable of producing functional images include PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computerized Tomography). Some of these systems are based on scintillator detectors, such as Nal, Csl and BGO, plus photon sensing devices, such as photomultipliers or photodiodes (see, e.g., U.S. Patent No. 5,732,704, incorporated herein by reference). Other systems are based on high-purity germanium (HPGe) crystals, which may itself be fairly small, but require a complex cooling system to work at cryogenic temperatures (e.g., - 180 °C). Hence, all of these systems, either based on scintillator detectors or HPGe crystals, are bulky and can only be integrated into an external detection system. However, since the detectors of such external systems are located far away from the imaged organs, they have a poor detection efficiency and low spatial resolution, which limit such detector's ability to pinpoint the exact positions of cancerous tissues in a small organ. All these drawbacks limit the usefulness of such radiation detection systems in diagnosing cancer in small organs, e.g., prostate glands, particularly for small tumors.

[0006] In view of the foregoing problems and drawbacks encountered in the conventional diagnostic techniques, a compact endocavity diagnostic probe was developed for nuclear radiation detection shown in FIG. 1 and disclosed in the U.S. Provisional Patent Application No. 61/320,157 filed on April 1, 2010, which is incorporated herein by reference in its entirety. Although this probe can generate images with high spatial resolution, it has a limited field-of-view (FOV). As illustrated in FIG. 2A, if the object of interest 100 is smaller than the FOV 110 of the probe 200, a single image can cover the whole object 100, e.g., cancerous tissue. However, as illustrated in FIG. 2B, if the object 100 is greater than the FOV 110 of the probe 200, a single image can only cover a portion of the object 100. Therefore, an operator would need to manually rotate the entire probe 200, including a detector 220 and a collimator 210 enclosed within a sleeve 230, to get the full scan of the object of interest including its edges. This technique, however, generates imprecise measurements and does not produce accurate depth information of the object. Hence, it is highly desirable to develop an improved endocavity diagnostic probe that would offer not only compact size, higher spatial resolution, and higher detection efficiency, but also would allow for precise imaging of tissue that is larger than the field-of-view (FOV) of the probe and would provide an operator with an ability to reconstruct a 3D image of the tissue to obtain the desired depth information.

SUMMARY

[0007] A novel rotatable radiation imaging probe is disclosed comprising a detector, a collimator, a signal processing circuitry, a module for rotating and/or a module for translating the detector within a cylindrical sheath. More particularly, the present rotatable radiation imaging probe is configured in a manner that allows for an object to be imaged even if the boundaries of the object exceed the field of view of the detector, when the detector is positioned at a predetermined distance from the object. By precisely rotating or linearly translating the detector within the probe in one of the desired directions along x-, y- or z-axis, a plurality of images can be generated and co-registered into one or more images. The generated image can ideally cover a larger field of view sufficient to fully display the object of interest, while still maintaining the spatial resolution of each of the superimposed images. In addition, the image series obtained in the rotation process can be used in 3 -dimension image reconstruction, providing depth information about the imaged object. As applicable to all embodiments, the detector within the present radiation imaging probe is preferably based on solid state semiconductor(s) capable of operating as a photon-to-charge direct conversion device arranged as a radiation imaging camera that can localize the distribution variations of radiation sources in tissues or other objects. However, the detector in all embodiments can also use scintillation detector(s) coupled to photon sensing devices as a replacement for the semiconductor detector elements, or in combination with the semiconductor detector elements.

[0008] The rotatable radiation imaging probe includes (i) a sheath that has a distal end and a proximal end; (ii) a rotational module positioned within the sheath; (iii) a detector affixed to the rotational module, preferably at or near the distal end of the sheath; and (iv) signal processing circuitry attached to the detector, which processes the signal produced by the detector due to an absorption of radiation. The rotational module is configured to rotate the detector about the longitudinal axis of the probe. Preferably, the sheath has a cylindrical cross-section with the distal end of the sheath being sealed and the proximal end of the sheath being open to allow for signal connections between the probe and a computer for further processing and visualization.

[0009] In one embodiment, the rotatable radiation imaging probe includes a rotational module that has a rotatable holder, at least one rotation element for rotating the holder about the longitudinal axis of the probe, and one or more support elements for radially guiding the rotatable holder along the inner surface of the sheath. In this embodiment, the rotation element can be an electric motor attached to the rotatable holder. The electric motor is connected to a power source and a rotation controller (e.g., computer) to regulate the rotation of the rotatable holder. Data defining the position of the rotatable holder(s) can be recorded for each setting. In another embodiment, the rotation element is an exposed knob for mechanical rotation of the rotatable holder. Other similar devices for rotating the rotatable holder with the detector affixed to it may be substituted for the knob without detracting from the scope of the invention.

[0010] In another embodiment, instead of the rotational module, the rotatable radiation imaging probe includes a translational module that has a translational holder to which the detector and front-end electronics are affixed, at least one translational element for shifting the translational holder along the longitudinal axis of the probe and optionally one or more support elements for linearly guiding the translational holder along the longitudinal axis of the probe. In one embodiment, the translational element may include a rotational (moving) screw passing through the translational holder that functions as a linear actuator of the translational holder location along the longitudinal axis of the probe. In such embodiment, the translational holder is preferably positioned at or near the distal end of the probe. The moving screw is connected to an electric motor affixed near the proximal end of the probe. The electric motor can be connected to a power source and a translational controller to regulate and, in some instances, record the movement of the translational holder along the longitudinal axis of the probe within the sheath. Alternatively, in another embodiment, the electric motor can be substituted by a knob, a crank or other means for mechanical movement of the translational holder within the sheath. In yet another embodiment, the moving screw can be replaced by a pulley system attached to the translational holder along the longitudinal axis of the probe.

[0011] In yet another embodiment, the rotatable radiation imaging probe can include both a rotational module and a translational module. In this embodiment, the translational holder with the affixed detector can be adapted to slide along the longitudinal axis of the rotational holder. In such embodiment, the translational holder can be positioned within a cavity of the rotational holder near the distal end of the probe. The length of the cavity as measured along the longitudinal axis of the probe can be about the same or greater than the outer length of the translational holder. In one embodiment, the length of the cavity in the rotational holder can range between about 10 and about 1 times the length of the translational holder to allow the translational holder to move along the length of the probe near the distal end.

[0012] The present detector can include a plurality of semiconductor detectors or a plurality of semiconductor detector modules positioned directly on the rotational holder or translational holder, depending on the configuration of the probe with a specific electrode configuration. One such configuration is a pixilated detector; it has one common cathode on one side, and an array of anodes on the other side. Each anode is read out separately to provide spatial information. Another configuration is an array of individual detectors. Each individual detector can be a planar detector, hemispheric detector, virtual Frisch-grid detector, or other similar bar-shaped detectors. Each element can be fabricated separately, and all the elements are integrated into an array. Similarly to the pixilated detector, each anode in the array is read out separately to provide spatial information. Finally, a further configuration may include a cross-strip detector array. A cross-strip detector array has one set of a linear array of electrodes on one side, and another set of a linear array of electrodes on the other side, orienting perpendicular to the direction of the former array. In this configuration, signals are read out from both sides. Coincidence of signals from these two sets of arrays indicates the interaction position of the gamma-ray photon inside the detector, thus providing desired spatial information.

[0013] The semiconductor radiation detector within the rotatable radiation imaging probe is preferably constructed from a solid state semiconductor capable of operating as a photon-to-charge direct conversion device. In particular, such semiconductors may be derived from, but not limited to, elements of groups III and V (e.g. GaAs), groups II and VI (e.g. CdTe), and group of IV (e.g. Si) of the periodic table. Among these semiconductors and their alloys, cadmium telluride (CdTe), cadmium zinc telluride (CdZnTe), cadmium manganese telluride (CdMnTe), thallium bromide (TIBr), mercury iodide (Hgl₂), germanium (Ge), or silicon (Si) may be used, while cadmium zinc telluride (CdZnTe) is the most preferred.

[0014] The present detector can include a plurality of scintillation detectors coupled to photon sensing devices. Scintillator detectors include a sensitive volume of a luminescent material (liquid or solid) that is viewed by a device that detects the gamma ray-induced light emissions (usually a photomultiplier (PMT) or photodiode). The scintillation material may be organic or inorganic. Examples of organic scintillators are anthracene and p-terphenyl, but it is not limited thereto. Some common inorganic scintillation materials are sodium iodide (Nal), cesium iodide (Csl), zinc sulfide (ZnS), cerium-activated lutetium oxyorthosilicate (Lu₂Si0₅:Ce3 or LSO), and lithium iodide (Lil), but it is not limited thereto. Bismuth germanate (Bi₄Ge30i₂), commonly referred to BGO, has become very popular in applications with high gamma counting efficiency and/or low neutron sensitivity requirements.

[0015] The rotatable radiation imaging probe further includes a collimator positioned on the detector near the distal end of the probe. The collimator has a plurality of apertures with each of their axes perpendicular to the surface of the collimator. While the collimator can have all parallel apertures, it can also have a special pattern of apertures for specific applications. For example, the collimator can have a fan-beam pattern of apertures, which brings a larger field-of-view to the system, or a focused pattern of apertures, which gives higher spatial resolution allowing the collimator to magnify the object, or interwoven multi- aperture configuration, which allows 3-D radiation imaging of the object of interest at a very close distance from the probe. A coded aperture can also be used as a replacement to a parallel-hole collimator. Alternatively, the collimator can be eliminated, and gamma images can be produced by tracking multiple Compton scattered events in coincidence within the detector, then using a Compton reconstruction scheme to produce the final image.

[0016] The collimator can be constructed from a radiation-absorbing material selected to provide efficient absorption of the incident radiation. The selection of the radiation- absorbing material would normally depend on the type of incident radiation and the energy level of the radiation when it strikes the surface plane of the collimator designed for a particular imaging application, e.g., medical or industrial, or may be designed to be used in any of several different applications by using a general purpose radiation-absorbing material. The collimator within the rotatable radiation imaging probe is preferably fabricated from a radiation-absorbing material known as the "high-Z" material that has a high density and a moderate-to-high atomic mass. Examples of such materials include, but are not limited to, lead (Pb), tungsten (W), gold (Au), molybdenum (Mo), copper (Cu), and various composites thereof.

[0017] The present detector can preferably have a shielding surrounding the detector and the collimator. While it is also envisioned in some embodiments that the detector module may be left unshielded, preferably a side shielding surrounds the four side surfaces of the detector and the collimator. More preferably, in addition to the side shielding, a back shielding is also implemented to fully cover the detector from all directions. The composition of the shielding is not limited to any particular compound and may be made in accordance with what is known in the art. The shape of the shield may be rectangular, circular or other suitable shapes. In one embodiment, the rotational holder, the translational holder or both can be constructed from a material that can function as the shielding.

[0018] The radiation imaging probe further includes front-end electronics (also referred to as signal processing circuits) that can be implemented, for example, in an Application-Specific-Integrated-Circuit (ASIC) or using commercially available circuits plus discrete components, such as FPGA, Microcontroller / Microprocessor, or a combination of such circuits and components. In addition to the front-end electronics, there are also readout control logic circuits to readout data from the front-end electronics and power supplies (both low voltage for the signal processing circuits and high voltage for the semiconductor radiation detector biasing), which are integrated into the probe. The front-end electronics can be mounted side-by-side with the detectors on the same side of the PCB board, or underneath the semiconductor radiation detectors on the other side of the PCB board. Alternatively, the system integration can have all the circuits on different boards as long as all of these boards are integrated together into one probe sheath. In yet another alternative, the system integration can have all the circuits on different boards in multiple interconnected units, where the detector module and the signal processing circuits are integrated on one PCB board in one probe sheath, while the rest of the circuitry, e.g., power circuitry, are integrated in a separate unit connected to the probe. If the front-end electronics are implemented in ASIC, the plurality of radiation detectors can be mounted directly on the ASIC instead of on the PCB board. Connections between the detector and ASIC can use indium bump-bonding, conductive epoxy, or similar technology while the connections between ASIC and PCB board can use for example wire-bonding.

[0019] A method is also provided for radiation imaging of an object or tissue of interest. The method includes locating an object of interest, for instance, a cancerous tissue; positioning a radiation imaging probe near the object of interest; and detecting the x-ray or gamma ray radiation emitted by the absorbed tracers within the object utilizing the present rotatable probe. In particular, detecting the emitted radiation includes collimating the radiation from the object of interest; detecting the radiation passing through the collimator by detector(s); recording the information about the radiation detected by the detector(s); rotating or translating the detector(s) along the x- , y- or z-axis; repeating the collimating, detecting, recording, rotating or translating to sufficiently scan the object of interest in its entirety or a desired portion thereof; recording the new coordinates of the probe after its rotation and/or translation for co-registration of different images, and processing the information recorded by the detector into one or more image(s) (for example, ID, 2D or 3D). In a preferred embodiment, the object of interest is a prostate gland. In another embodiment, the object of interest is a nuclear material within a container or other body.

[0020] Numerous medical-, industrial-, scientific-, environmental cleanup-, and national security-applications exist for the present probe. Some of the most prominent applications are imaging systems for detecting and localizing tumors and other abnormalities in the body, hand-held instruments to detect the trafficking of nuclear materials, portable instruments for safeguarding and verification of declared nuclear materials, and portable field instruments for environmental monitoring and remediation.

[0021] Thus, in one embodiment, a method for tumor localization encompasses the use of the rotatable radiation imaging probe with a semiconductor detector, e.g., fabricated array(s) of cadmium zinc telluride detectors. In another embodiment, a method encompasses the imaging of a prostate tumor especially for cancer detection. In yet another embodiment, a method for diagnosing a heart disease encompasses the use of the rotatable and/or translatable radiation imaging probe with a semiconductor detector. In still another embodiment, a method for monitoring, safeguarding and imaging nuclear materials and weapons encompasses the use of the rotatable radiation imaging probe. In some applications multiple rotatable and/or translatable probes are envisioned to expand the field of view and provide depth information based on stereoscopic imaging. In a further embodiment, a method for characterizing and defining cleanup methods for radioactive and mixed waste or a method for characterizing radiological hazards encompass the use of the rotatable radiation imaging probe. In still further embodiment, a method for element characterization in oil exploration or a method for material sorting based on X-ray fluorescence encompass the use of the rotatable radiation imaging probe. In yet another embodiment, the rotatable radiation imaging probe can be used as an X-ray radiographer to provide high-spatial-resolution X-ray transmission images.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1A illustrates a radiation imaging probe with one printed circuit board hosting all the circuits disclosed in the U.S. Prov. Pat. App. No. 61/320,157 and incorporated herein by reference. [0023] FIG. IB illustrates a radiation imaging probe with two separate printed circuit boards hosting the circuits disclosed in the U.S. Prov. Pat. App. No. 61/320,157 and incorporated herein by reference.

[0024] FIGs. 2 A and 2B illustrate a difference between the size of the object of interest (e.g., cancerous tissue) and the field-of-view (FOV) of the stationary radiation imaging probe.

[0025] FIG. 3A illustrates an embodiment of the rotatable endocavity imaging probe with an implemented rotational module having an electric motor as a rotation element.

[0026] FIG. 3B illustrates an embodiment of the rotatable endocavity imaging probe with an implemented rotational module and a translational module having an electric motor as a rotation element.

[0027] FIGs. 4A and 4B illustrate embodiments of the rotatable endocavity imaging probe of FIG. 3A and 3B, respectively, where the detector is attached to a PCB board and other circuitry.

[0028] FIGs. 5A and 5B illustrate a cross-sectional view of a rotatable endocavity imaging probe.

[0029] FIG. 6 illustrates an imaging range of the rotatable endocavity imaging probe.

[0030] FIGs. 7A-7B illustrate exemplary embodiments of the mechanical rotation mechanism in the rotatable endocavity imaging probe with an exposed knob.

[0031] FIG. 8 illustrates a scanning procedure to determine the dimensions (e.g., size) of the imaged object or tissue of interest.

[0032] FIG. 9 illustrates the rotatable endocavity imaging probe and available directions to pivot the probe and linearly translate the detector module inside the holder.

[0033] FIGs. 10A and 10B illustrate the rotatable endocavity imaging probe with (A) convergent collimator and (B) divergent collimator. [0034] FIG. 11 illustrates an embodiment of the rotatable endocavity imaging probe with implemented three (3) translational modules having three (3) separate detectors.

[0035] FIG. 12 illustrates the rotatable endocavity imaging probe with an implemented rotational module, a translational module, and a tilt module.

[0036] FIG. 13 illustrates an embodiment of the rotatable endocavity imaging probe with implemented three (3) separate detectors with parallel pinhole collimators having three orientations.

[0037] FIG. 14A illustrates an embodiment of the rotatable endocavity imaging probe with implemented three (3) separate detectors with collimators (A, B, C).

[0038] FIG. 14B illustrates an embodiment of the rotatable endocavity imaging probe of FIG. 14A where collimator (A) has a divergent field-of-view, collimator (B) has parallel a field-of-view, and collimator (C) has a convergent field-of-view.

DETAILED DESCRIPTION

[0039] A rotatable radiation imaging probe is described herein that (1) offers a compact size that is easy to carry, handle and operate, (2) provides higher spatial resolution and higher detection efficiency, (3) allows for precise imaging of an object that is larger than the field-of-view of the detector, (4) allows for detection of the edges of the object, and (5) provides the ability to reconstruct 3D images (i.e., depth information) of the object of interest.

[0040] With reference to FIGs. 3A and 3B, the rotatable radiation imaging probe 200 has (i) a sheath (or sleeve) 230; (ii) a detector 220; (iii) a rotation module (240-242); and/or (iv) a translation module (260-261); and (v) signal processing circuitry (see FIGs. 4A and 4B). The rotatable radiation imaging probe is configured in a manner that allows for an object to be imaged even if the boundaries of the object exceed the field-of-view (FOV) of the detector, when the detector is positioned at a predetermined distance from the object. By precisely rotating or linearly translating the detector within the probe in one of the desired directions along x-, y- or z-axis, a plurality of images can be generated. The generated images can be co-registered into one or more image(s) that ideally covers a larger field-of-view sufficient to completely display the object of interest, while still maintaining the spatial resolution of the superimposed image, e.g., about 1-2 mm intrinsic spatial resolution.

[0041] As illustrated in FIG. 3 A, the rotational module has a rotatable holder 240 and, at least one rotation element 242 for rotating the holder 240 about the longitudinal axis z of the probe 200. The rotational module also includes one or more support elements 241 for radially guiding the rotatable holder 240 along the inner surface of the sheath 230. In the embodiments that include the translational module, as illustrated in FIG. 3B, the probe 200 has a translational holder 260 to which the detector 220 and optionally a collimator 210 can be affixed. The translational module has at least one translational element 261 for shifting the translational holder 260 along the longitudinal axis of the probe 200 and optionally one or more support elements for linearly guiding the translational holder 260 along the longitudinal axis of the probe 200. While both a rotational and translational modules are illustrated in FIG. 3B, it is also envisioned that the rotatable radiation imaging probe may have only a translational module.

[0042] As applicable to all embodiments, the detector 220 is affixed to the rotational holder 240 (see FIG. 3A), the translational holder 260 (see FIG. 3B), or both, and by means of the rotation and translation modules is allowed to either rotate around or linearly shift along the longitudinal axis of the probe. The configuration and each component or subcomponent of the rotatable radiation imaging probe are discussed in detail below. It is to be understood, however, that those skilled in the art may develop other structural and functional modifications without significantly departing from the scope of the instant disclosure.

I. SHEATH AND GENERAL PARAMETERS OF THE PROBE [0043] As illustrated in FIGs. 3A and 3B or FIGs. 4A and 4B, the overall size of the probe 200 and the material used for the sheath 230 depends on the particular imaging application, e.g., medical, industrial, or security. The sheath 230 includes one sealed end and one open end. The open end has an opening 250 to allow for connection between the probe 200 and a computer (not shown) for further processing and visualization. In such embodiment, the probe 200 can have a detector and a power module within the sheath 230. Alternatively, a probe, which includes only the detector without the power module, can be connected to another processing unit that has the power module and a computer.

[0044] The outer cross-sectional shape of the probe may be cylindrical, rectangular with or without soft edges, or any other suitable shape for application of the probe. In medical applications, for example in the prostate cancer detection, for comfort in application of the probe, a smooth external surface is preferred coupled with an elongated shape and range of translation suitable for imaging the gland from its apex to base. The probe should typically avoid having sharp edges, unless the probe is also used as a cutting tool, e.g., for surgery. The probe further should be sufficiently small, e.g., 0 ~ 5 to 25 mm, to allow for the site insertion, for example, in the case of an endocavity probe. For easy operation, the probe may have different sizes (different diameters in case of cylindrical shape) for the sealed end and the open end. For example, the proximal end of the probe can be used as a handle and, therefore, may be larger than the distal end, which is designed for insertion into a body cavity. The probe may have various lengths depending on the depth of the cavity where the probe will be inserted. Typically, the diameter of the probe is between about 5 mm to about 30 mm. In a more preferred embodiment, the diameter of the probe is between about 6 mm to about 20 mm. In the most preferred embodiment, the diameter of the probe is about 12 mm. In the most preferred embodiment, the volume of the probe is about 30(L)x2.5(W)x2.5(H) cm . The weight of the probe is preferably minimized for ease of manual handling, or articulating arms may be provided for counterbalance. In one embodiment, the probe weighs less than 2 kg, however, in a preferred embodiment, the probe weight is less than about 500 g. In order to minimize the weight of the probe, it is important that the material used to construct the sheath is lightweight and does not interfere with the detection and imaging of radiation by the detector in the probe. Hence, the sheath can be fabricated from a non-radiation-absorbing or low-radiation-absorbing material that has low density and/or low atomic mass. Examples of such materials include, but are not limited to, carbon (e.g., plastics and other polycarbonates), aluminum (Al), stainless steel and other similar materials. The selection of the radiation-non- absorbing or low-absorbing material and the thickness of this material should be determined so as to provide efficient transmission of the incident radiation. Accordingly, selection of the material depends on the type of incident radiation and the energy of the radiation to be detected. Alternatively, the sheath may be constructed or fabricated in sections. While the overall body of the sheath can be made from one preferably lightweight material, the section of the sheath in the field-of-view of the detector can be made from a different more desirable non-radiation-absorbing material. II. DETECTOR

[0045] The detector is composed of a plurality of semiconductor based radiation detectors. In this embodiment, the plurality of radiation detectors provide a direct conversion of detected radiation energy into electronic signals. The plurality of radiation detectors are arranged in a one- or two-dimensional array, preferably in a two-dimensional array, affixed to a mounting frame (e.g., PCB) or to an application-specific-integrated-circuit (ASIC).

[0046] The radiation detector elements may have either a rectangular or circular cross-section with a sensitive thickness selected on the basis of the radiation energy region relevant to the application of interest. The semiconductors that may be employed herein are generally derived from, but not limited to, elements of groups III and V (e.g. GaAs), groups II and VI (e.g. CdTe), and group IV (e.g. Si) of the periodic table. Instead of binary compounds or single element semiconductors (e.g. Si), ternary materials also may be used as the compound semiconductors capable of operating as photon-to-charge direct conversion devices, e.g., Cdi__xZn_xTe and Cdi__xMn_xTe, where 0<x<l . It is common practice to omit the fractional subscripts when referring to the alloy families; such practice is followed throughout the present description. Among these semiconductors and their alloys, in one embodiment, cadmium telluride (CdTe), cadmium zinc telluride (CdZnTe), cadmium manganese telluride (CdMnTe), thallium bromide (TIBr), silicon crystal (Si) or mercuric iodide (Hgl₂) is used. However, it will be appreciated and understood by those skilled in the art that any compound or element may be used as the semiconductor for the present probe as long as it is capable of operating as a photon-to-charge direct conversion device. In one particular embodiment, the compound semiconductor crystal used for the plurality of radiation detector elements is made from cadmium zinc telluride (CdZnTe or CZT) crystals. One skilled in the art will appreciate that the semiconductor detector may be larger or smaller and vary in shape depending upon the design specifications.

[0047] In order to localize the positions of radiation sources, for example, in an organ

(e.g. prostate), different configurations of detector's electrodes can be used, such as, but not limited to, pixilated detectors, bar-shaped detectors in an array, and orthogonal (cross-) strip detectors. In one embodiment, a pixilated detector with a common electrode on one side (e.g., cathode) and an array of sensing electrodes on the other side (e.g., a plurality of anodes) is used. Alternatively, an array of individual detectors is used. In this embodiment, the detector includes an array of single detection elements. Radiation beams substantially parallel to the axis of apertures traverse the collimator and are detected by individual detection elements. Here, the single detection element is based on a semiconductor detector with various configurations including but not limited to planar detector or the so-called Frisch-grid detector design, as proposed by A. E. Bolotnikov et al. in "Optimization of virtual Frisch- grid CdZnTe detector designs for imaging and spectroscopy of gamma rays^'", Proc. SPIE, 6706, 670603 (2007) and U.S. Patent Publication Serial No. 2009/0026371 Al, which are each incorporated by reference herein in their entirety. Yet in another alternative, an orthogonal cross-strip detector is used. A cross-strip detector has one set of a linear array of electrodes on one side of the detector, and another set of a linear array of electrodes on the other side of the detector, orienting perpendicular to the direction of the former array. In this configuration, signals are read out from both sides and the coincidence of signals from these two sets of arrays indicates the interaction position of the gamma-ray photon inside the detector. An orthogonal strip detector may be double-sided, as proposed by J.C. Lund et al. in "Miniature Gamma-Ray Camera for Tumor Localization", issued by Sandia National Laboratories (August 1997), which is incorporated by reference herein in its entirety. In a preferred embodiment, a pixilated detector is used. Although the semiconductor detector can preferably detect gamma radiation, it is also envisioned that the same principle of rotatable and translatable radiation imaging probe can be used with other modalities, e.g., an ultrasound probe.

[0048] In another embodiment, the detector is composed of a plurality of scintillation detectors coupled to photon sensing devices, and to the readout electronic circuits. Scintillator detectors include a sensitive volume of a luminescent material (liquid or solid) that is viewed by a device that detects the gamma ray-induced light emissions (usually a photomultiplier (PMT) or photodiode). The scintillation material may be organic or inorganic. Examples of organic scintillators are anthracene and p-terphenyl. Examples of inorganic scintillation materials are sodium iodide (Nal), cesium iodide (Csl), zinc sulfide (ZnS), and lithium iodide (Lil). The scintillation detector(s) can be monolithic, covering an area of several adjacent pixels used for measuring the light output, or it can be an array of individual elements with each element corresponding to one pixel used to measure the light output from the respective scintillator element.

[0049] In one embodiment, the detector further has a collimator that is adapted to be positioned substantially parallel to the detector. The collimator is fabricated of a radiation absorbing material but has a plurality of closely arranged apertures, e.g., holes or pin-holes. The apertures on the collimator allow only the radiation of interest to pass to the detector. Specifically, the radiation beams emitting from the object, if not absorbed or scattered by body tissue, exit the object along a straight- line trajectory. The collimator blocks or absorbs radiation beams that are not parallel to the axes of the apertures (openings in the collimator). Radiation beams traveling parallel to the apertures are detected by the radiation detector elements of the radiation detector. In one embodiment, the apertures of the collimator are uniform and may be perpendicular or skewed to the plurality of radiation detectors. In another embodiment, the apertures in the collimator are not uniform. Preferably, the nonuniform collimator has a fan-beam pattern of the apertures, which brings a wider field-of- view to the detector (see FIG. 10B) that may be useful for edge detection. Alternatively, the fan-beam pattern of the apertures can be used to obtain initial low resolution images. The low resolution information can be used to define the range of control parameters for subsequent high-resolution imaging. Since a wider FOV allows for faster imaging, it can be useful at the start of the imaging process. In some embodiments, the lower resolution system can serve as a guide for adaptation of a higher-resolution system to the specific application and object of interest. In contrast, the non-uniform collimator can also have a focus pattern of the apertures (see FIG. 10A), which gives higher spatial resolution as the collimator magnifies the imaged object. For example, by using a convergent collimator, it is possible to reduce the spatial resolution of rotatable radiation imaging probe to 100 microns or less. In yet another alternative, a collimator can have an interwoven multi-aperture configuration for 3 -dimensional radiation imaging applications, which is disclosed in an International Patent Application No. PCT/US2010/029409 assigned to Brookhaven Science Associates, which is incorporated by reference herein in its entirety.

[0050] In a preferred embodiment, the collimator may be constructed from a radiation-absorbing material known as the "high-Z" materials that have high densities and/or high atomic masses. Examples of such materials include, but are not limited to, lead (Pb), tungsten (W), gold (Au), molybdenum (Mo), copper (Cu) and the composites thereof, such as a composite containing 50-99% of tungsten, including but not limited to tungsten carbide (WC), tungsten semicarbide (W₂C), copper/silver tungsten alloys, and nickel/iron tungsten alloys. The selection of the radiation-absorbing material and the thickness of the radiation- absorbent material should be determined so as to provide efficient absorption of the incident radiation, and would normally depend on the type of incident radiation and the energy level of the radiation when it strikes the surface plane of the collimator. The type of incident radiation and the energy level of the radiation depends on the particular imaging application, e.g., medical or industrial, or may be designed to be used in any of several different applications by using a general purpose radiation-absorbing material. In medical applications, for instance, in one embodiment, Indium-I l l (^luIn; 171 keV and 245 keV) keV), Iodine-123 (¹²³I; 159 keV) and Technetium-99m (^99mTc; 140 keV) are commonly used in radioactive tracers for imaging of the prostate and other organs. In such applications, it is envisioned that the collimator may comprise copper, molybdenum, tungsten, lead, or gold.

103

[0051] In another embodiment for medical applications, Palladium- 103 ( Pd; 21 keV) is used as a radioactive implant seed for treatment of the early stage prostate cancer. In such applications, it is envisioned that the collimator may be fabricated from copper, molybdenum, tungsten, lead, or gold. In one preferred embodiment, the collimator is fabricated from copper. In another preferred embodiment, the collimator is fabricated from tungsten. In yet another preferred embodiment, the collimator is fabricated from gold. The collimator body defining the surface plane may be fabricated of a solid layer of radiation- absorbing material of a predetermined thickness, in which the plurality of apertures may be machined in any known manner according to optimized specifications. For example, a solid layer of radiation-absorbing material of a predetermined thickness may be machined or fabricated in a known manner, e.g., using precision lasers, to achieve a collimator with the appropriate aperture parameters and aperture distribution pattern.

[0052] The collimator body containing the plurality of apertures may also be fabricated by laterally arranging septa of radiation-absorbing material so as to form predetermined patterns of radiation-guiding conduits or channels. In addition, the collimator body having a plurality of apertures may be manufactured by vertically stacking multiple layers of radiation-absorbing material with each layer having predetermined aperture cross- sections and distribution patterns so as to collectively form radiation-guiding conduits or channels. For example, multiple layers of lead, gold, tungsten, or the like may be vertically stacked to provide enhanced absorption of stray and scattered radiation to thereby ensure that only radiation with predetermined wavelengths is detected. In the case of vertically stacking multiple layers, the collimator may be formed by stacking repeating layers of the same radiation-absorbing material, or by stacking layers of different radiation-absorbing materials.

[0053] In the collimator, the aperture parameters such as aperture diameter and shape, aperture material, aperture arrangement, number of apertures, focal length, and acceptance angle(s) are not limited to specific values, but are to be determined subject to optimization based on required system performance specifications for the particular system being designed, as will be understood by those skilled in the art. Extensive patent and non-patent literature providing optimal configurations for apertures such as pinholes and parallel holes is readily available. Examples of such documentation are U.S. Patent No. 5,245,191 to Barber et al., entitled Semiconductor Sensor for Gamma-Ray Tomographic Imaging System, and non-patent literature article entitled "Investigation of Spatial Resolution and Efficiency Using Pinholes with Small Pinhole Angle," by M. B. Williams, A. V. Stolin and B. K. Kundu, IEEE TNS/MIC 2002, each of which is incorporated herein by reference in its entirety.

[0054] In a further embodiment, the collimator and the plurality of radiation detectors can have a side shielding surrounding the four (4) side surfaces of the collimator and detector combination. In a further preferred embodiment, back shielding can also be added so that the detectors are covered fully from all directions. In these embodiments, it is envisioned that the shielding has a uniform rectangular shape. However, in other embodiments, other shapes are also envisioned. In yet another embodiment, the shielding has the shape of the holder. In this embodiment, instead of fabricating a separate shielding, the holder can be fabricated out of a shielding material, thus, serving a dual function of a shield and the holder at the same time. In a preferable embodiment, if the probe has the rotatable and translational holders, the translational holder can be fabricated out of a shielding material so that the separate shielding can be reduced or eliminated completely, contributing to the compact design of the endocavity probe.

III. ROTATIONAL MODULE

[0055] As illustrated in FIG. 3A and FIG. 4A, the rotational module has a rotatable holder 240 to which the detector 220 is secured. The rotational module also has at least one rotation element 242 for rotating the rotatable holder 240 about the longitudinal axis of the probe 200, and one or more support elements 241 for axially guiding the rotatable holder 240 along the inner surface of the sheath 230. Typically, the detector 220 is arranged in a one- or two-dimensional array affixed to a mounting frame or an ASIC (see e.g., FIG 4A) and secured to the rotatable holder 240, for example, by welds, glue or screws. As illustrated in FIG. 3A, in one embodiment, the detector 220 is secured in a cavity of the rotatable holder 240.

[0056] The rotatable holder 240 can typically be made from any suitable material known in the art as long it does not interfere with the detection function of the probe. For instance, in one embodiment, the holder is made from carbon (e.g., plastics, polycarbonates, and composites such as carbon fiber), aluminum (Al), stainless steel and other similar materials. In another embodiment, the holder is made from a shielding material such as lead (Pb), tungsten (W), gold (Au), molybdenum (Mo), copper (Cu) or the composites thereof. In yet another embodiment, a portion of the holder is made from one material, such as polycarbonate, aluminum, stainless steel, etc., providing the window between the collimator and the object of interest for imaging, while the remainder of the holder is made from another material useful for shielding the radiation, such as lead or tungsten. The dimensions of the holder depend on the plurality of factors such as the size of the sheath 230, the size of the collimator 210, the size of the detector 220, the size of the rotation element 242, the size and configuration of the support elements 241, and whether all or some signal and power processing circuitry are included within the probe 200. In one exemplary embodiment, the rotatable holder 240 is cylindrical in shape and is positioned near the distal end of the probe 200. The rotatable holder can have a cross-sectional diameter of about 5 to about 25 mm and a length of about 20 cm as shown in FIG. 3A. Although, other cross-sectional shapes of the rotatable holder 230 are also envisioned such as triangular, rectangular, oval, polygonal, and others as long as the rotatable holder 240 is able to rotate within the sheath 230 of the probe 200. In one embodiment, the rotatable holder can have a cavity near the distal end of the probe. The size of the cavity is about the size of the detector 220 or the detector 220 and the collimator 210 combination. [0057] The rotational module further includes a rotation element 242 that can be an electric motor. The motor can be any type compact DC or AC motor that allows for precise and controlled rotation of the rotatable holder within the sheath of the probe and recording of the angular position of the probe. In one embodiment, as illustrated in FIG. 3A, the motor can be positioned within the sheath 230 at the proximal end of the probe 200. The motor can be controlled by the same computer that is used for image acquisition or by a different/separate computer than the computer that is used for image acquisition. In yet another embodiment, the motor can be controlled by an external device such as, for example, a joystick.

[0058] In another embodiment, the rotation element is a moveable mechanical device, such as an exposed knob, attached to the rotatable holder 240 for mechanical rotation by an operator. Other similar devices such as a handle, a crank, a screw or a grip for rotating the detector module can be envisioned. In this embodiment, as shown in FIG 7A, the sheath can have two parts, a rotating part 242 and a fixed part 230. The rotating part 242 is located at the proximal end of the probe 200 with a feed-through 250 for communication cables. The rotatable holder 240 is connected to the rotating part 242. On the edge between these two parts, there can be scales or rotation markings to help identify and record the rotation angle, as shown in FIG. 7B.

[0059] The rotational module further includes support elements 241. FIG. 3A illustrates an example where the support elements 241 are placed at the opposite end of the rotation element motor near the distal end of the probe 200. It should be understood that precise position of the support elements 241 are not constrained and can be located at one or multiple locations of the rotatable holder. The support elements 241 are not limited to any particular design. For example, the support elements 241 can include ball-bearings, Teflon pads, or other support elements. IV. TRANSLATIONAL MODULE

[0060] In another embodiment, instead of, or in conjunction with, the rotational module, the present radiation imaging probe can include a translational module. In some embodiments, there may be applications (e.g., imaging of an enlarged prostate or interception of nuclear material) where the length of the field of view of the detector is less than the length of the object of interest. For these applications the translational module allows the detector to be moved within the probe and positioned deeper into or withdrawn from the body cavity without moving the probe itself. The translation module has a translational holder 260 to which the detector 220 can be affixed and placed on a linear track along the axis (z) of the probe 200 or, as illustrated in FIGs. 3B and 4B, along the axis (z) of the rotatable module 240 in the probe 200. The translational module further includes at least one translational element 261 for shifting the translational holder 260 along the longitudinal axis (z) of the probe 200, and optionally one or more support elements (not shown) for linearly guiding the translational holder 260 along the longitudinal axis of the probe 200.

[0061] In one embodiment, the translational element is a rotational (moving) screw as shown in FIG. 3B (translational element 261) passing through the translational holder that functions as a linear actuator of the translational holder location along the longitudinal axis of the probe. The translational element further includes an electric motor for regulating the movement of the translational holder along the longitudinal axis (z) of the probe within the sheath. The translational holder is preferably positioned at or near the distal end of the probe. The movable screw can be connected to an electric motor or other mechanical device affixed near the proximal end of the probe. Alternatively, in another embodiment, the electric motor can be substituted by an exposed knob or other means for mechanical movement of the translational holder within the sheath. In yet another embodiment, the rotational (moving) screw can be replaced with a pulley system. [0062] In yet another embodiment, the rotatable radiation imaging probe can include both a rotational module and a translational module as shown in FIG. 3B. In this embodiment, the translational holder 260 with the affixed detector 220 can be adapted to slide along the longitudinal axis of the rotational holder 240. The translational holder 260 is preferably positioned within a cavity of the rotational holder 240 near the distal end of the probe 200. The length of the cavity as measured along the longitudinal axis of the probe can be about the same or greater than the outer length of the translational holder. In one embodiment, the length of the cavity in the rotational holder 240 can range between a multiple of about 10 and 1 of the length of the translational holder 260 to allow the translational holder to move along the length of the probe 200 near the distal end.

[0063] FIG. 11 illustrates another embodiment with two or more detectors 220 secured independently on separate translational modules 260 (for example, three are shown in FIG. 11). Each module 260 has its own readout circuits with the detectors 220 and the output connections 280 from the detectors 220 can be, for example, a regular cable or a flexible PCB. The output connections 280 from all the detectors 220 can go directly out of the probe 200 via the feedthrough 250 (not shown; see e.g., FIGs. 4A or 4B), or are merged together on another PCB board that resides inside the probe 200 apparatus (see e.g., FIG. IB).

[0064] In yet another embodiment illustrated in FIG. 12, each individual detector shown in FIG. 11 can have a tilt module 290, which is a rotation stage(s) secured on top of the translational module 260. In this embodiment, the detectors 220 can rotate independently about a pre-defined axis. For example, as shown in FIG. 12, the tilt module 290 can rotate the detector 220 about an axis perpendicular to longitudinal axis of the probe 200.

[0065] FIG. 13 illustrates a probe of FIG. 11 with a tilt module of FIG. 12, where the probe 200 has two or more independently rotatable detectors 220. For ease of understanding, FIG. 13 shows only the detectors 220 with a corresponding collimator 210 in the sheath 230 of the probe 200. In this exemplary embodiment, the left detector 220 A and the right detector 220C are rotated towards the center detector 220B. In this case, it is possible to get multiple views of an imaged object that is positioned above the center detector 220B. The multiple views can provide more detailed information about the object and may also provide depth information about the object. However, the application of multiple rotatable detectors is not limited to this exemplary embodiment since it is envisioned that each detector can be rotated independently and face as many different directions as desired.

[0066] The probe with independently rotatable detectors can also have independent configurations of each detector in terms of the detector type, e.g., scintillation and semiconductor, detector geometry, collimator configuration, and other parameters. FIG. 14A shows three detectors secured on different translational modules with three collimators, i.e., divergent, parallel and convergent. As illustrated in FIG. 14B, three cross-sectional views at different positions are shown and marked as A- A, B-B, and C-C. A-A section view shows the collimator with divergent pinhole configuration that provides a large fan-shape field-of- view, which is useful in a coarse scan to find the boundary of the imaged object during the imaging procedure. Once the object is identified by this detector, the second detector module shown in B-B or C-C section can be translated into the same position to initiate a second scan. This detector can have either a parallel pin-hole collimator with better spatial resolution, i.e., better images, or a convergent collimator that can magnify the specific area inside the imaged object, and look at the details of the object.

V. A SIGNAL PROCESSING CIRCUITRY

[0067] The signal from the plurality of radiation detector elements is acquired and transmitted to a signal processing circuit(s). The signal processing circuit(s) are connected to a control logic unit to obtain data from the signal processing circuit(s) and a power supply circuitry to obtain data from the power supply. The system integration in the probe can have all of the circuits on one PCB board 270 inside the probe (see FIGs. 4A and 4B), or have them on different PCB boards as long as all of these PCB boards are integrated together into one probe sheath (see e.g., FIG. IB). FIGs. 4A and 4B illustrate the probe 200 that include the detector readout circuits 271, e.g., ASIC, and other circuits 272, e.g. control logic, voltage generation / regulation, etc. The communication signals leave the board 270 via a regular cable or a flexible PCB 280. The signals can leave the probe directly via the feedthrough cables or go to another PCB board inside the apparatus (not shown in the FIG. 4A or 4B; see e.g., FIG. IB). For example, FIG. IB illustrates a design with one PCB board hosting the front-end ASIC and readout control logic, while the other PCB board having all the power supplies (low-voltage regulator, filters, and high-voltage generator). The readout control logic can be implemented in ASIC, field programmable gate array (FPGA), Microcontroller / Microprocessor, or a combination thereof.

[0068] Typically, when a gamma photon hits the active region of a pixel in the detector array, it generates electron-hole (e-h) pairs. The amount of e-h pairs is proportional to the energy of gamma photons. Due to the influence of the high voltage bias, negatively charged carriers (electrons) will drift to the anode (pixel) inducing a signal current. In a preferred embodiment, the signal current is collected and amplified by charge sensitive amplifier (CSA) in the ASIC. The output signal from the CSA is compared with a preset threshold and if the signal is larger than the threshold, a trigger signal is generated, causing the counter of that channel to increase by one. Depending on the applications, there can be several different thresholds, allowing the user to detect photons with different energies and produce images for each separate energy bin. Correspondingly, there are multiple energy bins to count photons with different energies. The readout control logic reads out the values of the energy bins for all pixels and sends them to the computer for imaging, reconstruction and display.

[0069] When radiopharmaceuticals are administrated into a patient's body, the radioactive tracer will concentrate in the specific tissues inside the target organ. The tracer will decay and emit gamma-ray photons in all directions with known energy (e.g. 140-keV gamma rays for Tc-99m, 27-36 keV gamma rays for 1-125, 171-keV and 245 -keV gamma rays for In-I l l, and 364-keV gamma rays for 1-131). Only the photons with trajectories parallel to the axis of the collimator apertures can reach the radiation detector, i.e., within the field of view of the probe. Alternatively, the collimator can be eliminated, and gamma images can be produced by tracking multiple Compton scattered events in coincidence within the detector and then using a Compton reconstruction scheme to produce the final image. These photons will ionize the compound semiconductor and generate electron-hole pairs that are separated and guided to the contacts by the internal electric field.

[0070] The amount of pairs generated by a photon is proportional to the photon's energy. Because the compound semiconductor detector is negatively biased, the electrons will drift to the anodes (pixels) while the holes will drift to the cathode. The amplitude of this signal is proportional to the energy of the gamma-ray photon, and can be processed and read out by the front-end electronics and the control logic. The front-end electronics counts the photon absorption events within each pixel of the detector. The region directly beneath a hot spot has the highest counts. Once the information, i.e., image, has been taken at one position of the probe, the detector module is adjusted to obtain an image at a new position until the object of interest has been completely scanned. The images are then co-registered based on the known rotation step and translation, and reconstructed into the full image using an information processing device, e.g., computer. The number of images taken in this procedure depend on the field-of-view of the detectors, the size of the object of interest, the system requirements on spatial resolution and acceptable measurement time

APPLICATIONS AND METHODS

[0071] As illustrated in FIG. 5A, the field-of-view 110 of the probe 200 is constrained by the dimensions of the detector 220 and collimator 210, as well as the orientation of the apertures 211 in the collimator 210. In this embodiment, the parallel field- of-view is attributed to parallel pin-hole geometry of the collimator, however, it is to be understood that the probe's field-of-view may be altered depending on the design of the apertures in the collimator, e.g., interwoven, fanned, convergent, or divergent apertures. Because of the limited field-of-view 110, a single image scanned by the detector 220 can only cover a portion of the imaged object 100. In embodiments, as illustrated in FIG. 2A where the object 100 is smaller than the size of the detector plane, the probe's field-of-view 110 is sufficient to scan the entire object when the detector 220 faces directly towards the object. However, even for cases when the object 100 is smaller than the size of the field-of-view 110, it is, nonetheless, desirable to look for edge effects of the object 100 and use multiple images to obtain depth information.

[0072] FIG. 5B illustrates the same probe 200 of FIG. 3 A but rotated by an angle, a, from a position (i) to an arbitrary position (i+1). At the new position, the detector 220 records another image of the object 100. The scanning range (or imaging range) of the probe 200 can be determined by the application and the desired total field of view. FIG. 6 illustrates an application with an imaging range of 180°. The step of the rotation is determined by the application, the resolution of each image, and acceptable measurement time for acquiring the full image. By taking images at different positions, a hot spot can be identified by a sequence of images, e.g., i-1, i, and i+1. By precisely controlling the interior rotation angle of the detector, a series of images can be merged into one full size picture of the imaged object.

[0073] A method is provided for radiation imaging an object or tissue of interest. In a preferred embodiment, the object of interest is a prostate gland. In one embodiment, the method has the steps of locating an object of interest, for instance, a cancerous tissue; positioning a radiation imaging probe near the object of interest; detecting the gamma ray radiation emitted by the absorbed tracers within the object as a plurality of images utilizing the rotatable probe; and processing and combining the information recorded by the detector in the plurality of images into one single image (ID, 2D or 3D). In particular, the step of detecting includes collimating radiation from the object of interest; detecting collimated radiation with a semiconductor detector; recording the information about the radiation detected by the semiconductor detector as a single image; rotating the detector about the longitudinal axis of the probe; recording the new angular positions and other coordinates to define the field of view; repeating the steps of collimating, detecting, recording, and rotating to sufficiently scan the whole object of interest.

[0074] In another embodiment, the step of detecting includes collimating radiation from the object of interest; detecting collimated radiation with a semiconductor detector; recording the information about the radiation detected by the semiconductor detector as a single image; translating the detector along the longitudinal axis of the probe; repeating the steps of collimating, detecting, recording, and translating to sufficiently scan the whole object of interest.

[0075] In yet another embodiment, the step of detecting includes collimating radiation from the object of interest; detecting collimated radiation with a semiconductor detector; recording the information about the radiation detected by the semiconductor detector as a single image; rotating the detector about the longitudinal axis of the probe; translating the detector along the longitudinal axis of the probe; repeating the steps of collimating, detecting, recording, rotating and translating to sufficiently scan the whole object of interest.

[0076] Preferably, before an image with high spatial resolution is generated, a parallel-hole collimator or other fan-beam shaped collimator may be used to perform an initial scan to define the boundaries of the imaged object. This initial scan avoids unnecessary high-resolution imaging of the areas that do not contain an object of interest. In this step, as illustrated in FIG. 9, in addition to rotating the probe around the axis of rotation (z-axis) depicted as Θ, the probe can also be pivoted around the x-axis (depicted as a), y-axis (depicted as β), or a combination thereof. By defining the boundary conditions for imaging the full object, the start and stop positions of the rotation within the probe can be specified as illustrated in FIG. 8.

[0077] FIG. 6 shows how the probe works in one of the dimensions, assuming an object of interest, which may be referred to as a hot spot (e.g. cancerous tissue) is inside the imaged organ. When radiopharmaceuticals are administrated into a patient's body, the radioactive tracer will concentrate in the specific tissues inside the target organ. The tracer will decay and emit gamma-ray photons in all directions with known energy. Only the photons with trajectories parallel to the axis of the collimator apertures within the field of view of the probe can reach the radiation detector. These photons will generate a signal that can be processed and read out by the front-end electronics and the control logic. Once the information, i.e., image, has been taken at one position of the probe, the detector module is adjusted to obtain an image at a new position until the object of interest has been completely scanned. The information obtained from each image is then merged or co-registered based on the specific position of the detector module and reconstructed into a full image. In addition, the dimension(s) of the object can be calculated based on the angles between the two rotation positions (see FIG. 8 - Pos_start and Pos_st_op). Specifically, by rotating the detector within the probe, one hot spot is captured by a several consecutive images (see FIG. 6) from different positions. Since the rotation angle is known and is precisely controlled, the 3D position of the hot spot can be reconstructed from the planar images and detector positions.

[0078] The precise control and recording of the rotation angles of the present rotatable radiation imaging probe are necessary for the image reconstruction. The same quality of image and depth information cannot be obtained by manually rotating a hand-held probe because of the difficulty to precisely control the position and the angle of the probe, as well as a possibility of wobble during any manual rotation.

[0079] Numerous medical-, industrial-, scientific-, environmental cleanup-, and national and homeland security-applications exist for the present probe. Some of the most prominent are imaging systems for detecting and localizing tumors and other abnormalities in the body, hand-held instruments to detect the trafficking of nuclear materials, and portable field instruments for environmental monitoring and remediation.

Application 1: Tumor Localization:

[0080] Cancer is a major cause of mortality, second only to cardiovascular disease.

Almost all patients who are cured have localized disease at first presentation. Typically, patients are treated by surgery, radiotherapy, chemotherapy, or by some combination of these different methods. The success of the surgical intervention depends on the extent to which physicians can identify and then remove all of the viable cancerous cells. Using a radiation imaging probe, one or more images can be recorded and co-registered to generate a much higher linear dynamic range and to resolve the energies of both the unscattered and scattered gamma rays, thereby allowing easy subtraction of the scattered gamma rays from the displayed image.

Application 2: Imaging of Prostate Tumors: [0081] According to the American Cancer Society, in the United States, about one in six men will be diagnosed with prostate cancer over their lifetime. Treating prostate cancer is a balancing act, because there is no one treatment suitable for all. The main types of treatments are surgical removal of the gland, radiation, and implanting radioactive seeds. Each treatment has serious side effects, the most troublesome being sexual dysfunction, and urinary and bowel incontinence. Several studies suggest that often such treatments are overused. Unnecessary treatments usually result from the wide variability of these cancers and the difficulties in effectively diagnosing and characterizing the cancerous tissue. This is particularly true for small, non-aggressive early-stage cancers that almost always are difficult to reliably detect with conventional ultrasound techniques.

[0082] The present radiation imaging probe can be used in the earlier detection of small tumors and for the image-guided biopsy of suspect tissues. By using a trans-rectal probe with rotatable detector, the semiconductor detector array can be very close to the prostate gland, thereby greatly increasing its efficiency in detecting and imaging the gamma rays emitted from the radioactive tracer(s), e.g., Indium- 111 or other gamma emitting isotope, taken up in the gland as compared to large Anger cameras placed outside the body.

Application 3: Diagnosis of Heart Disease:

[0083] Medical systems for this application are similar to the one discussed above for cancer detection. After injecting a radiotracer containing, for example, technetium-99m into the blood flow and by examining the specific gamma emissions of the radiotracer, regions of the heart with lower than expected blood flow can be identified. Similarly, radiopharmaceuticals can be employed in bone scans, identifying regions with abnormalities and the presence of lesions.

Application 4: Safeguarding of Nuclear Materials and Weapons: [0084] Concealment and transport of special nuclear materials can be easily achieved, because conventional security measures (video surveillance, human inspection, etc.) are neither fully adequate nor reliable. One approach to solve this problem is to monitor and safeguard nuclear materials by detecting their characteristic gamma-ray emissions. Depending on the material (and its isotopic compositions), gamma rays with isotope-specific energies are emitted. To assure acceptable numbers of false alarms and identify isotopes, it is imperative to have an energy-resolving capability in the detection system. The radiation imaging probe is suitable for this applications because the system occupies much less space and is ideally suited for many portable applications, particularly those requiring both enhanced energy resolution and unattended operation.

Application 5: Spectrometers and Imagers for Cleanup of Radioactive and Mixed Waste:

[0085] The present radiation imaging probes based on the semiconductor detectors can also be used to characterize radioactive sources distributed in the environment. For example, the probe can be used to characterize 55-gallon radioactive and mixed-waste containers to ensure that the contents are not leaking, and, in some cases, to determine what is inside without undertaking detailed laboratory analyses or generating secondary wastes. The probe has the spatial resolution sufficient for imaging radioactive waste, and can be further improved based on different collimation (see for e.g., FIG. 10A). Full characterization is essential before safe, effective, and efficient remediation strategies can be planned and executed.

Application 6: Real-Time Dosimeters:

[0086] The present radiation imaging probe can provide an indicator of radiological hazards for emergency response workers, such as firemen and policemen. The size of an entire battery-operated, low-cost system has to be no larger than a beeper, and provide warnings to untrained personnel of enhanced dangerous radiation levels and doses. Other agencies (e.g., customs agents and postal workers) could use it to assist with interdiction of a wide range of radioactive materials.

Application 7: X-ray Radiography:

[0087] A linear array of semiconductor detectors can be constructed in the present radiation imaging probe to provide high-spatial-resolution X-ray transmission images. These transmission images are generated by translating a sample between a fan-shaped X-ray beam and a linear array of detectors at a controlled speed (e.g., baggage moving along a conveyor belt). The current size of the linear arrays is limited to several inches, and the systems cannot image large containers without a step-and-repeat process.

Application 8: Oil Exploration:

[0088] Oil well logging relies heavily on neutron sources to activate elements within the earth's composition and detectors to analyze the gamma-ray emissions and determine the specific elements present. For example, the characteristic gamma-ray emission of hydrogen and carbon can reveal the presence of hydrocarbons in a bore hole. In this application, since the radiation imaging probe is compact, it can easily fit in the well, yet provide a high energy- resolution for gamma-ray energies in the 2-8 MeV energy range, and good efficiency to allow rapid collection of data as a function of depth.

Application 9: X-ray Fluorescence Instruments for Materials Sorting:

[0089] The present detectors (e.g., based on CZT) can precisely identify elements based on their characteristic X-ray fluorescence emissions and provide detailed quantitative information about the composition of unknown materials. The ability to quantify most elements within the periodic table based on their X-ray fluorescence is important to a wide range of users who need to identify unknown materials. The principal advantage of the present radiation imaging probe is that it offer high-resolution X-ray spectroscopy at room temperature. Some specific field applications include the analysis of lead in paints, measurement of environmental toxins, recycling of metals (e.g., aluminum, brass-bronze- nickel, and stainless steel alloys), and environmental cleanup operations.

[0090] All publications and patents mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described probe and its components will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the disclosure has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

1. A radiation imaging probe, comprising:

(i) a sheath that has a distal end and a proximal end;

(ii) a rotational module positioned within the sheath;

(iii) a detector secured to the rotational module within the sheath that is operable to detect radiation; and

(iv) a signal processing circuitry attached to the detector to read and process a signal produced by the detector due to an absorption of the radiation;

wherein the rotational module rotates the detector about the longitudinal axis of the radiation imaging probe.

2. The radiation imaging probe of claim 1, wherein the detector comprises a single semiconductor detector or a plurality of semiconductor detectors.

3. The radiation imaging probe of claim 1, wherein the detector comprises a single scintillation detector or a plurality of scintillation detectors.

4. The radiation detector of claim 1, wherein the detector comprises a plurality of detectors, each of which is independently secured to its own rotational module.

5. The radiation imaging probe of claim 1, further comprises a collimator positioned on top of the detector.

6. The radiation imaging probe of claim 1, wherein the distal end of the sheath is sealed and the proximal end of the sheath is open.

7. The radiation imaging probe of claim 1, wherein the rotational module comprises a rotatable holder that can be rotated within the sheath, a rotational element that is attached to the rotatable holder and rotates the rotatable holder around the longitudinal axis of the probe and one or more support elements for radially guiding the rotatable holder along an inner surface of the sheath.

8. The radiation imaging probe of claim 7, wherein the detector is directly secured to the rotatable holder near the distal end of the radiation imaging probe.

9. The radiation imaging probe of claim 7, wherein the rotation element is an electric motor.

10. The radiation imaging probe of claim 9, wherein the electric motor is secured in the probe at or near the proximal end of the sheath.

11. The rotatable radiation imaging probe of claim 7, wherein the rotation element is an exposed knob for mechanically rotating the rotatable holder.

12. The radiation imaging probe of claim 1, further comprises a translational module for linearly shifting the detector along a length of a rotatable holder within the sheath.

13. The radiation imaging probe of claim 12, wherein the translational module comprises

a translational holder attached to the rotatable holder that is moveable along the longitudinal axis of the radiation imaging probe with the detector affixed thereon,

a translational element for shifting the translational holder along the longitudinal axis of the radiation imaging probe and

optionally one or more support elements for linearly guiding the translational holder

14. The radiation imaging probe of claim 13, wherein the rotatable holder has a cavity near the distal end of the probe and the translational holder is positioned within said cavity.

15. The radiation imaging probe of claim 13, wherein a length of a cavity as measured along the longitudinal axis of the radiation imaging probe is about the same size as that of the translational holder.

16. The radiation imaging probe of claim 13, wherein a length of a cavity as measured along the longitudinal axis of the radiation imaging probe is greater in size than that of a secondary holder.

17. The radiation imaging probe of claim 16, wherein the length of the cavity ranges between about 1 to 10 times the length of the translational holder.

18. The radiation imaging probe of claim 13, wherein the translation element comprises a moving screw passing through the translational holder that functions as a linear actuator of a translational holder location along the longitudinal axis of the probe.

19. The radiation imaging probe of claim 18, wherein the translation element further comprises an electric motor connected to the moving screw for rotating said screw.

20. The radiation imaging probe of claim 13, wherein the translation element comprises a pulley system attached to the translational holder for pulling the translational holder along the length of the rotatable holder.

21. The radiation imaging probe of claim 1, wherein the sheath is cylindrical.

22. The radiation imaging probe of claim 1, wherein the sheath comprises a non- radiation-absorbing or a low-radiation-absorbing material with a low density, a low atomic mass or a combination of the low density and the low atomic mass.

23. The radiation imaging probe of claim 22, wherein the non-radiation-absorbing or low-radiation-absorbing material is selected from the group consisting of carbon, aluminum, stainless steel and composites thereof.

24. The radiation imaging probe of claim 23, wherein the carbon comprises a polycarbonate.

25. The radiation imaging probe of claim 5, wherein the detector absorbs radiation that passes through apertures in the collimator.

26. The radiation imaging probe of claim 2, wherein the plurality of semiconductor detectors are configured as a pixilated detector, an orthogonal strip detector, an array of individual detectors, or a combination thereof.

27. The radiation imaging probe of claim 26, wherein the array of individual detectors is a virtual Frisch-grid detector array or a planar detector array.

28. The radiation imaging probe of claim 2, wherein each semiconductor detector in the plurality of the semiconductor detectors comprises one or more semiconductors selected from the elements of groups III and V, groups II and VI and group IV of the periodic table.

29. The radiation imaging probe of claim 28, where the semiconductor is a single element crystal, a binary compound, a ternary compound or a ternary alloy.

30. The radiation imaging probe of claim 28, wherein the semiconductor comprises CdZnTe (Cadmium Zinc Telluride), CdTe (Cadmium Telluride), CdMnTe (Cadmium Manganese Telluride), Hgl₂ (Mercuric Iodide), or TlBr (Thallium Bromide).

31. The radiation imaging probe of claim 28, wherein the semiconductor comprises CdZnTe (Cadmium Zinc Telluride).

32. The radiation imaging probe of claim 5, wherein the collimator comprises a radiation-absorbing material.

33. The radiation imaging probe of claim 32, wherein the radiation-absorbing material has a high density and moderate -to-high atomic mass.

34. The radiation imaging probe of claim 32, wherein the radiation-absorbing material is selected based on a type of incident radiation and an energy level of the radiation when it strikes a surface plane of the collimator.

35. The radiation imaging probe of claim 34, wherein the incident radiation is emitted by ¹²⁵I, ^mIn, ^99mTc, ¹³¹I, or ¹⁰³Pd.

36. The radiation imaging probe of claim 34, wherein the incident radiation is emitted by an external radiation source or device that generates X-rays.

37. The radiation imaging probe of claim 32, wherein the radiation-absorbing material is selected from the group consisting of lead (Pb), tungsten (W), gold (Au), molybdenum (Mo), copper (Cu) and composites thereof.

38. The radiation imaging probe of claim 1, wherein the detector is in fixed positions on a PCB board and secured to the rotatable holder.

39. The radiation imaging probe of claim 1, wherein the detector is independently positioned on a PCB board and independently secured to a rotational holder.

40. The radiation imaging probe of claim 12, wherein the detector is in fixed position on a PCB board and secured to the translational holder.

41. The radiation imaging probe of claim 1, wherein the detectors are

independently positioned on a PCB board and independently secured to a translational holder.

42. The radiation imaging probe of claim 38, wherein the signal processing circuitry attached to the detector includes front-end electronics.

43. The radiation imaging probe of claim 40, wherein the signal processing circuitry attached to the detector includes front-end electronics.

44. The radiation imaging probe of claim 42, wherein the front-end electronics are an Application-Specific-Integrated-Circuit (ASIC).

45. The radiation imaging probe of claim 43, wherein the front-end electronics are an Application-Specific-Integrated-Circuit (ASIC).

46. The radiation imaging probe of claim 42, wherein the front-end electronics are mounted side-by-side with the detector on the same side of the PCB board.

47. The radiation imaging probe of claim 42, wherein the front-end electronics are mounted underneath the detector on the other side of the PCB board.

48. The radiation imaging probe of claim 42, wherein the detector, the collimator, the front-end electronics and control logic are placed on the same PCB board.

49. The radiation imaging probe of claim 42, wherein the detector, the collimator, the front-end electronics and control logic are placed on different PCB boards.

50. The radiation imaging probe of claim 43, wherein the front-end electronics are mounted side-by-side with the detector on the same side of the PCB board.

51. The radiation imaging probe of claim 43, wherein the front-end electronics are mounted underneath the detector on the other side of the PCB board.

52. The radiation imaging probe of claim 43, wherein the detector, the collimator, the front-end electronics and control logic are placed on the same PCB board.

53. The radiation imaging probe of claim 43, wherein the detector, the collimator, the front-end electronics and control logic are placed on different PCB boards.

54. The radiation imaging probe of claim 46, wherein the detector is mounted directly on the ASIC.

55. The radiation imaging probe of claim 54, wherein connections between the semiconductor detector and ASIC are made by bump-bonding or flip-chip bonding.

56. The radiation imaging probe of claim 1, wherein the detected radiation is an x- ray or gamma ray radiation.

57. A radiation imaging probe, comprising:

(i) a sheath that has a distal and proximal ends;

(ii) a translational module positioned within the sheath;

(iii) a semiconductor detector secured to the translational module within the sheath that is operable to detect radiation; and

(iv) a signal processing circuitry attached to the detector to read and process the signal produced by the detector due to an absorption of the radiation; wherein the translational module moves the semiconductor detector along a longitudinal axis of the radiation imaging probe.

58. The radiation imaging probe of claim 57, further comprises a collimator positioned on a surface of the semiconductor detector.

59. The radiation imaging probe of claim 57, wherein the detected radiation is an x-ray or gamma ray radiation.

60. A method for radiation imaging an object or tissue of interest, comprising locating an object of interest that emits radiation;

positioning a radiation imaging probe near the object or tissue of interest; collimating the radiation from the object or tissue of interest; detecting collimated radiation by a semiconductor detector within the probe; recording the detected radiation as a single image;

rotating the detector about the longitudinal axis of the probe; repeating the steps of collimating, detecting, recording, and rotating to acquire a plurality of images with a field-of-view that completely covers the object or tissue of interest; and

processing and combining the plurality of images into one single image.

61. The method of claim 60, wherein the object or tissue of interest is a prostate gland.

62. The method of claim 60, further comprises translating the detector along the longitudinal axis of the radiation imaging probe and the repeating includes translating.

63. The method of claim 60, wherein the detected radiation is an x-ray or gamma ray radiation.

64. A method for radiation imaging an object or tissue of interest, comprising locating an object or tissue of interest that emits radiation; positioning a radiation imaging probe near the object or tissue of interest; collimating the radiation from the object or tissue of interest;

detecting collimated radiation by a semiconductor detector within the radiation imaging probe;

recording the detected radiation as two or more images;

translating the detector along the longitudinal axis of the radiation imaging probe;

repeating the collimating, detecting, recording, and translating to acquire a plurality of images with a field-of-view that completely covers the object or tissue of interest; and

processing and combining the plurality of images into one or more images.

65. The method of claims 64, wherein the detected radiation is an x-ray or gamma ray radiation.