WO2021211941A1

WO2021211941A1 - Mobile configurable pet for in-room bedside imaging

Info

Publication number: WO2021211941A1
Application number: PCT/US2021/027638
Authority: WO
Inventors: Julie Brefczynski-Lewis; Nanda SIVA; Thorsten WUEST; James W. Lewis; Swarna RAJAGOPALAN
Original assignee: West Virginia University
Priority date: 2020-04-16
Filing date: 2021-04-16
Publication date: 2021-10-21

Abstract

A small profile, mobile imaging device includes a plurality of scanning modules for obtaining brain images of a neurological or mental health patient. The device includes a frame which includes a central aperture surrounded by the scanning modules in a ring pattern. A support is coupled to the frame and is configured to move the frame with one or more degrees of freedom, in order to allow the head of a patient to be inserted into the central aperture where scanning can take place. The device also includes a mobile cart which is coupled to the support and which moves the imaging device to a patient location, which, for example, may be a bedside location in a hospital room. The scanning modules may include positron-emission tomography (PET) detectors.

Description

MOBILE CONFIGURABLE PET FOR IN-ROOM BEDSIDE IMAGING

GOVERNMENT LICENSE RIGHTS

[0001] This invention was made with government support under grant IIP-1929529 awarded by National Science Foundation. The government has certain rights in the invention.

TECHNICAL FIELD

[0002] This disclosure relates to an apparatus and method for systems and methods for controlling the acquisition and processing of medical imaging information from neurological patients.

BACKGROUND

[0003] Brain injury and associated secondary injuries can be difficult to diagnose and monitor. Electroencephalogram (EEG) tests can be performed bedside, but such tests are spatially imprecise, have a tendency to miss metabolic changes, and are unable to detect seizure activity with sufficient accuracy when sedatives are used.

[0004] Currently, neurologists and neurointensivists rely on snapshot imaging to determine the condition of a patient. Examples of snapshot imaging include computed tomography (CT) and magnetic resonance imaging (MRI). While these forms of imaging are useful, they also have significant drawbacks. For example, CT and MRI imaging reveal only structural damage. They do not provide any indication of the physiological damage a patient may have experienced.

[0005] Other forms of patient assessment include intracranial pressure monitoring and oxygen monitoring. These monitoring techniques also have drawbacks. For example, intracranial pressure monitoring and oxygen monitoring may be performed in only a limited number of cases. More significantly, these monitoring techniques are dangerously intrusive in that they require drilling a burr- hole into the skull and inserting a monitor deep into the brain. As a result, the patient is exposed to a significant risk of infection. These monitoring techniques have also proven unreliable in many cases and are confined to assessing only small areas of the brain. Consequently, intracranial pressure monitoring is only able to provide information indicating local (rather than global) injury.

[0006] Another imaging technology for the brain is positron-emission tomography (PET). Like MRI and CT scanners, known PET scanners are large machines located at specialized imaging centers or at special rooms in hospitals. Because of their great weight, PET scanners presently available are not mobile. Consequently, patients to be scanned must be transported to PET facilities. Once there, each patient must lie in a specialized posture (e.g., flat on a table in a lying position) while the scan is performed. This is very difficult for patients with brain injuries because lying flat introduces intracranial hypertension risk. In an attempt to compensate, patients with brain injuries are kept in beds with their heads elevated during the PET scan.

[0007] The need to be transported to an imaging facility in order to be scanned by large, stationary machines presents significant challenges for other types of patients, including those that are critically ill with aspiration or oxygenation risks. Patient transport can also expose patients in critical condition to risks that include hemodynamic instability and intracranial hypertension. Transporting patients to an imaging facility also requires the use of a skilled nursing staff, often requiring such staff to travel with the patient.

SUMMARY

[0008] In accordance with one or more embodiments, a small profile, mobile imaging device is provided which can be moved with ease and convenience into the room of a neurological patient to perform a quality brain scan, all while the patient remains in his bed or other familiar surroundings. The imaging device includes a positron-emission tomography (PET) scanner that is accompanied by a support system that allows brain scans to be performed without requiring the patient to move into a specialized position or posture. The imaging system, therefore, satisfies the need for a bedside brain scanner without exposing the patient to any of the risks associated with the large imaging equipment that has been conventionally used in specialized scanning facilities. Moreover, not only does the patient does not have to be transported to the equipment but lower radioisotope dosages may be used compared with imaging using large stationary scanning equipment due to closer proximity of detectors which do not have to accommodate the whole body. The lower radioisotope dosages inures to the benefit of both the patient and care personnel. The imaging system also satisfies a need for a bedside brain scanner which allows scanning a desired body part of a patient in isolation due to an infections disease. The imaging system may be used to image the patient, without transporting the patient out of isolation, or exposing medical personnel or other patients to an infected patient in a specialized scanning facility. The mobile imaging device thus reduces the spread of infection from a patient carrying a pathogen, i.e., a bacterial or viral pathogen.

[0009] The frame may have a substantially hemispherical shape with a flat bottom surface, and the flat bottom surface mauy be arranged at a substantially a horizontal position when the scanning modules are activated to obtain a brain image. The support may include a first section that is connected in a fixed position to the mobile cart and at least a second section that moves relative to the first section to allow the frame to be moved into a scanning position relative to a patient. The scanning modules may be electrically connected in a daisy chain. The mobile cart may include a controller configured to control operation of the scanning modules.

[0010] Various embodiments disclosed herein relate to a mobile imaging device, including a plurality of scanning modules arranged in a ring pattern, a frame coupled to the scanning modules and including a central aperture surrounded by the scanning modules in the ring pattern, a support coupled to the frame and configured to move the frame at a position to allow a desired body part of a patient to be inserted into the central aperture, and a mobile cart coupled to the support to move the imaging device to a patient location, wherein the plurality of scanning modules include positron-emission tomography detectors. The desired body part of the patient is a head, an arm, a leg, a foot, a hand, or a torso. The support may include a first section that is connected in a fixed position to the mobile cart; and at least a second section that moves relative to the first section to allow the frame to be moved into a scanning position relative to a patient. The scanning modules may be electrically connected in a daisy chain. The mobile cart may include a controller configured to control operation of the scanning modules. [0011] In various embodiments, the desired body part of the patient is a head, and the frame has a substantially hemispherical shape with a flat bottom surface. The flat bottom surface may be arranged at a substantially horizontal position when the scanning modules are activated to obtain a brain image. [0012] In various embodiments, the desired body part of the patient is an arm, a leg, a foot, a hand, or a torso, and the frame is substantially ring shaped. The frame may be configured to receive the desired body part when the scanning modules are activated to obtain an image.

[0013] Various embodiments disclosed herein relate to a mobile imaging device, including a plurality of scanning modules arranged in a ring pattern, a frame coupled to the scanning modules and including a central aperture surrounded by the scanning modules in the ring pattern, a support coupled to the frame and configured to move the frame at a position to allow a desired body part of a patient to be inserted into the central aperture, and a mobile cart coupled to the support to move the imaging device to a patient location, wherein the plurality of scanning modules include positron-emission tomography detectors. The frame may have a substantially hemispherical shape with a flat bottom surface. The flat bottom surface may be arranged at a substantially horizontal position when the scanning modules are activated to obtain an image.

[0014] In various embodiments, the mobile imaging device includes a plurality of scanning modules arranged in at least two stacked ring patterns. The mobile imaging device may include a plurality of scanning modules, including positron-emission tomography detectors, in combination with at least one one additional type of scanner or detector. Suitable additional types of scanner or detector include electrode sensors for use in recording an EEG; an MRI scanner; an optical sensor for use in recording near-infrared or ultraviolet light transmission or reflection; and combinations thereof.

[0015] The present disclosure describes a method of imaging a desired body part of a patient with a mobile imaging device, by moving a mobile cart carrying the mobile imaging device to a patient location, wherein the mobile imaging device comprises a frame including a central aperture, and the central aperture is surrounded by a plurality of scanning modules arranged in a ring pattern. The frame may be moved into a position allowing the desired body part of the patient to be inserted into the central aperture. The desired body part is inserted into the central aperture, and the plurality of scanning modules are sequentially activated to obtain an image of the desired body part, wherein the plurality of scanning modules include positron-emission tomography detectors. The scanning modules may be electrically connected in a daisy chain. In the disclosed method, the desired body part of the patient may be a head, an arm, a leg, a foot, a hand, or a torso.

[0016] In various embodiments of the disclosed method, the desired body part of the patient is a head, and the frame has a substantially hemispherical shape with a flat bottom surface. The flat bottom surface may be arranged at a substantially horizontal position when the scanning modules are activated to obtain a brain image.

[0017] In various embodiments of the disclosed method, the desired body part of the patient is an arm, a leg, a foot, a hand, or a torso, and the frame is substantially ring shaped. The frame may be configured to receive the desired body part when the scanning modules are activated to obtain an image.

[0018] A brief summary of various embodiments is presented below. Some simplifications and omissions may be made in the following summary, which is intended to highlight and introduce some aspects of the various example embodiments, but not to limit the scope of the invention. Detailed descriptions of example embodiments adequate to allow those of ordinary skill in the art to make and use the inventive concepts will follow in later sections.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to illustrate example embodiments of concepts found in the claims and explain various principles and advantages of those embodiments. [0020] These and other more detailed and specific features are more fully disclosed in the following specification, reference being had to the accompanying drawings, in which:

[0021] FIG. 1 illustrates an embodiment of a mobile imaging system;

[0022] FIG. 2 illustrates an embodiment of a scanner of the mobile imaging system;

[0023] FIG. 3 illustrates an embodiment of a frame of the scanner;

[0024] FIG. 4 illustrates an example of the scanner in use;

[0025] FIG. 5 illustrates an example of processing circuits for scanning modules;

[0026] FIG. 6 illustrates an example of a ring of scanning modules;

[0027] FIG. 7 illustrates an example of a single-energy spectrum;

[0028] FIG. 8 illustrates an example of spatial resolution performance of the imaging system;

[0029] FIG. 9 illustrates an example of detection sensitivity of the imaging system;

[0030] FIG. 10 illustrates an example of count rate capability of the imaging system;

[0031] FIG. 11 illustrates an example of single slices of non-TOF-corrected images;

[0032] FIG. 12 illustrates an example of slices of reconstructed volumes of mini-hot-rod cases; [0033] FIG. 13 illustrates an example of slices of reconstructed volumes of Hoffman brain phantoms; [0034] FIG. 14 illustrates an embodiment of a support for a scanner of a mobile imaging device; [0035] FIG. 15 illustrates another embodiment of a support for a scanner of a mobile imaging device’ and

[0036] FIG. 16 illustrates an embodiment of an arrangement of scanning modules of a mobile imaging device.

[0037] FIGS. 17 and 18A to 18D illustrate an additional example of a mobile cart

DETAILED DESCRIPTION

[0038] The descriptions and drawings illustrate the principles of various example embodiments. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Additionally, the term, “or,” as used herein, refers to a non-exclusive or (i.e., and/or), unless otherwise indicated (e.g., “or else” or “or in the alternative”). Also, the various example embodiments described herein are not necessarily mutually exclusive, as some example embodiments can be combined with one or more other example embodiments to form new example embodiments. Descriptors such as “first,” “second,” “third,” etc., are not meant to limit the order of elements discussed, are used to distinguish one element from the next, and are generally interchangeable. Values such as maximum or minimum may be predetermined and set to different values based on the application.

[0039] FIG. 1 illustrates a mobile imaging device 100 including a scanner 10, a frame 20 secured to the scanner, a scanner housing 30 to cover the frame, and a support 40 for supporting and/ or moving the scanner into position relative to the head of the patient. The patient location may be the patient bed 70 in a hospital room or other locations where the patient may be located. Bed 70 has a planar surface 72 for the patient to lie upon, and may provide an inclined back support 74.

[0040] As seen in FIG. 2, the scanner 10 includes a plurality of PET scanning modules (or detectors) 15i to 15_N arranged in a predetermined pattern within the frame. Returning to FIG. 1, in one embodiment, the scanning modules are arranged in at least one ring with a central aperture 55 into which the head of the patient is inserted. The ring may be sized to provide a predetermined (e.g., ~5 cm) coverage of the brain in the axial or oblique plane. After a predetermined dosage of radiotracers are administered, the scanning modules may be operated to detect and generate metabolic brain images for use in determining the condition and course of treatment for the patient.

[0041] One modification may include arranging the scanning modules in multiple rings that are concentrically located along a common central axis. The rings may be stacked directly adjacent to one another or spaced from one another at predetermined distances, for example, according to the area of the brain to be scanned. Stacking rings of scanning modules may increase the sensitivity of the imaging device due to greater gamma capture. In one experiment, the system was able to attain a spatial resolution of 2.3 mm 5 mm from the center and a peak sensitivity of 1.28%. However, different performance characteristics may be achieved in other embodiments.

[0042] The frame 20 may have a variety of shapes suitable for securing the scanning modules at predetermined distances from the head of the patient. In one embodiment, shown in FIG. 1, the frame 20 has a hemispherical shape including one or more curved stabilizing bars 22 coupled to a substantially circular collar 24. The collar supports a mounting surface 26 for holding the scanning modules into position relative to the central aperture, as well as any wires or other electronics required for operating the scanning modules.

[0043] FIG. 2 illustrates a top internal view of the scanner 10, which includes the scanning modules 15i to 15_N arranged in a circular pattern relative to the central aperture 55. In this embodiment, sixteen scanning modules (e.g., N=16) are arranged in a ring around the central aperture 55, which includes substantially the entire head of the patient P as depicted. In various embodiments, two or more stacked rows on scanning modules 15i to 15_N may be arranged in rings around the central aperture 55. Scanning modules 15i to 15_N may be PET scanning detectors. Scanning modules 15i to 15_N may include PET scanning detectors in combination with other types of signal detectors, e.g., electrode sensors for use in recording an EEG; an MRI scanner; optical sensors for use in recording infrared or ultraviolet light transmission or reflection, etc.

[0044] Power, data, and control lines 210 are coupled to respective ones of the scanning modules to allow for proper operation. A printed circuit board 225 including a processor and/or other control circuits may be coupled to the control lines for operating the scanning modules. As shown in FIG. 1, the power, data, and control lines may be coupled to equipment carried in a mobile cart 60, either directly or through the printed circuit board. The cart equipment may include, for example, a computer, monitor, software, fan controls, and/or other electrical devices that allow for proper operation of the scanner for purposes of image capture and display.

[0045] The size of the central aperture is sufficient to allow the scanning modules to be spatially separated from the head of the patient P by an amount which ensures the capturing of a quality brain scan. The separation distance may range, for example, from 0 to 20 cm. In another embodiment, the separation distance may be in a different range depending, for example, on the sensitivity and scanning properties of the scanning modules.

[0046] An optional protective pad 230 (e.g., made of foam) may be placed between the face of the patient and the scanning modules disposed along the forward surface of the scanner for safety purposes, as shown in FIG. 2. Also, in FIG. 2, a portion of the stabilizing bar 22 of the frame 20 is illustrated to be in alignment with a central axis passing through the central aperture 55, which in this case is a circular hole. A portion of the scanner housing 30 is also depicted in this figure. The housing may be made from a variety of materials. In one example embodiment, the housing is in the form of a shroud made of electrically insulative material which may be opaque or translucent. In some cases, the housing 30 may include vent holes 35 to allow air to circulate around the scanning modules for cooling purposes.

[0047] FIG. 3 illustrates an example of a bottom surface 21 of the frame 20. In this example, the bottom surface includes an annular (detector support) plate 310 that is coupled to the circular collar 24 (shown in FIG. 1) by fasteners 320. The plate may be made of metal, an insulative material (e.g., a polymer), or another type of durable material. The fasteners may be, for example, nuts-and-bolts as depicted or other types of fasteners. The interior circumferential surface 322 of the annular plate 310 may include padding 330 to protect the head and ears of the patient when inserted into the central aperture 55. At least a portion of the circular collar 24 may be coupled to a protective cover 340, and the scanner housing 350 may be coupled to an upper surface of the protective cover. The protective cover may also be made of metal or an insulative material. As shown in FIG. 3, the scanner may be moved to the bedside location of the patient. For example, the scanner may be moved to either side of the bed adjacent to the patient or the scanner may be positioned behind the bed next to the patient’s head.

[0048] In one embodiment, the annular detector support plate 310 may rotate freely within the frame 20 or with the frame to move into position on the head of a patient. Once an ideal position is found, the scanner may be secured in that position, for example, with a detent or other type of latch or lock. In one embodiment, the detent may be a bolt that slides into a slot which locks the annular plate into position within the frame.

[0049] The imaging device may be used to obtain PET images for patients in a variety of conditions, including patients with critical brain injuries, or patients in an outpatient clinic, mental health treatment facility, patients undergoing electroconvulsive therapy, rural hospitals and military hospitals located closer to the theatre or stationed region. Therefore, in addition to the forgoing features, various portions of the frame 20 and/or housing 30 may include spaces (e.g., holes, channels, spaces, etc.), supports, or other features for accommodating drainage tubes, bandages, and/ or other medical items that may be used in the care of the patient. The size of the central aperture and the surrounding inner circumferential surface of the frame are examples of areas which may accommodate the bandages and drainage tubes.

[0050] FIG. 4 illustrates an example of the scanner 10 in use with the head of a patient P inserted into the central aperture. In this example, the bed 410 has been adjusted so that the patient is in a raised or sitting position at an inclined angle, e.g., 30° or another angle. The adjustment may be made by the electronic controls of the bed. A wedge pillow may be placed under the shoulders to raise the head and shoulders of the patient. In one case, an inflatable pillow may be used to support the head and neck of the patient, as well as any monitors or other electronics.

[0051] At an inclined position, the scanner is able to be carefully lowered until the scanning modules are properly aligned with the area of the brain to be scanned. In this picture, the vent holes 420 in the scanner housing are clearly visible, along with a portion of a curved stabilizing bar 22. In this embodiment, one or more bolts 440 are used to fasten the stabilizing bar to the circular collar of the frame. Because the scanning modules of the scanner are arranged to surround the head of the patient, a complete brain scan may be performed to produce a 360° PET image that corresponds to the head level of the scanner.

[0052] Referring again to FIG. 1, the support 40 includes at least one arm with multiple degrees of freedom of movement. In this example, the support includes a mechanical coupling 41 to attach the frame of the scanner to the support. The mechanical coupling may allow the frame to move in one or more directions. For example, the mechanical coupling may allow the frame to rotate or pivot relative to the head of the patient, in order to allow his head to be introduced into the central aperture. In one embodiment, the mechanical coupling may be coupled to an extender which allows the position of the scanner frame to be raised and lowered. Arrows A1 and A2 are illustrative of the degrees of freedom with which the scanner frame may move to accommodate insertion of the head of the patient into position for scanning.

[0053] The support may also include a first attachment 42, a support arm 43, a second attachment 44, and a post 45. The first attachment 42 is fastened between the mechanical coupling 41 and the support arm 43 and may be curved in order to allow the frame to be moved into a desired position. The curvature of the first attachment may be substantially 90° or another angle. In one embodiment, the first attachment may be pivotally fastened to the mechanical coupling and/ or the support arm to allow for rotation along respective longitudinal axes. Otherwise, the first attachment may be fixed to increase stability. The first attachment may be made of a metal or insulative material.

[0054] The support arm 43 may have a length that is sufficient to allow the scanner to hang over the bed of the patient. The length may vary, for example, based on the intended application of the scanner. The support arm may be made of sufficiently rigid material to prevent the scanner from vibrating or oscillating during use, so that accurate images may be obtained.

[0055] The second attachment 44 may be fastened between the support arm and the post. Like the first attachment, the second attachment may be curved in order to allow the frame to be moved into a desired position, either for scanning or mobility to the patient location. The curvature of the second attachment may be substantially 90° or another angle. In one embodiment, the second attachment may be pivotally fastened to the support arm and/ or the mechanical coupling to allow for rotation along respective longitudinal axes. Otherwise, the second attachment may be fixed to increase stability. Also, like the first attachment, the second attachment may be made of a metal or insulative material. [0056] The post 45 provides vertical stabilization of the imaging device. The post may be made of one or more sections connected together to hold the scanner into position relative to the patient. In one embodiment, the sections may be telescoping in order to allow the height of the post extend and retract vertically, thereby adjusting the height of the scanner to move into and out of the head to be scanned. The support and its attendant feature may be moved manually by medical personnel or technicians, or servo motors may be included at select locations to move the support features relative to one another and the patient. When servo motors are included, controls for operating the servo motors (and thus for adjusting the position of the support and scanner) may be included in equipment, for example, located in the mobile cart 60. In one embodiment, the power, data, and/ or control lines may extend in hollow portions or channels of the support, to electrically connect the scanning modules, printed circuit board, and/ or other electrical features into equipment carried in the mobile cart 60. Alternatively, the power, data, and control lines may be coupled to outside surfaces of the support by fasteners.

[0057] Referring to FIG. 1, the mobile cart 60 includes wheels 62 that allow the imaging device to be moved to the patient location. The module cart may also carry equipment in a cabinet-type area 65, which, for example, may include a power source (e.g., battery) or power adapter (e.g., for converting wall outlet power) for operating the scanner. The wheels may include retractable locks or brakes 64, shown in FIG. 1, for holding the cart (and thus the scanner) in position. Flere, the cart is shown as including a cabinet-type arrangement with doors enclosing a space for storing the equipment previously discussed, along with any other medical supplies that may be used in caring for the patient being scanned.

[0058] In one embodiment, movement of the mobile cart and/or parts of the scanner and support may be performed by a robot with controls stored inside of the cart, e.g., software controls on a computing device stored in the interior compart of the cart. Such a robot may perform control of the servo motors previously discussed for making position adjustments so that the scanner may be moved into proper position relative to the patient. An artificially intelligent robot suitable for use in surgical applications may be adapted for use in controlling the mobile cart and/ or scanner. In addition to equipment, the mobile cart 60 may also include a counterweight for balancing out the torqueing forces produced by the weight of the scanner and frame and the length of the support arm. Such a counterweight may therefore increase the stability of the imaging device, at least during scanning. [0059] In one example application, time-of-flight (TOF) resolution on the order of several hundreds of picoseconds may be achieved to obtain high performance PET imaging. TOF may utilize the difference between accurately measured arrival times of annihilation photons to estimate the positions of positron annihilations. An example embodiment of such an imaging device is described below.

Example Implementation

[0060] In accordance with one embodiment, the scanner 10 of the imaging device may be constructed using PET scanning detectors 15i to 15_N made by Hamamatsu Photonics (HPK), as shown in FIG. 2. These detectors may be customized with different scintillation arrays, offering pixel sizes from 1.5 to 4 mm. The scanning detectors 15i to 15_N may be arranged in one or more rings and daisy-chained with common timing and data transfer lines, allowing for the implementation of a customized, small-diameter TOF-PET scanner as previously described.

[0061] In this example implementation, each HPK module (C13500-4075LC-12) may include a 12x12 array of 4.1x4.1x20 mm LFS scintillator elements (4.205 mm pixel pitch) individually coupled to a 12x12 array of multipixel photon counters (MPPCs). The total detection area may be, for example, approximately 50x50 mm². The modules may be hermetically sealed to make them light and airtight. [0062] The scanning detectors may be arranged in a multi-pixel photon counter (MPPC) array which may be read out with one or more digital printed circuit boards. Each board may include an array of four application-specific integrated circuits (ASIC), with each ASIC digitizing 18 analog channels providing information corresponding to event position, energy, and timing. Each module may be housed in a protective (e.g., aluminum) casing to provide mechanical robustness and lightweight. In addition, individual modules may be mounted inside 3D-printed plastic holders, and fans may be included inside the housing to cool the electronics.

[0063] Each complete detector module may have a predetermined weight, e.g., approximately 0.5 kg, with the modules daisy-chained and arranged in at least one ring geometry with a diameter of 26.7 cm and axial coverage of ~5 cm. As previously indicated, stacks of multiple rings may be included in another embodiment. A Korad KA3305P multi-channel power supply may be used to provide power to the modules and control electronic boards.

[0064] The electronics in this implementation may include two power supply boards, three timing distribution boards, and a data relay board. A relay board receives data from the modules and sends it to a host PC (e.g., in the mobile cart 60) via an optical data link. A timing signal (e.g., 10 MHz) may be generated internally by the data relay board and distributed through the master timing board to one or more slave timing boards, and ultimately to the PET detector modules.

[0065] FIG. 5 illustrates an example of the processing circuits that may be used to power and control two PET modules 650 and 660 connected in a daisy-chain configuration. The processing circuits include an interface board 610, a clock distribution unit 620, a local power supply 630, and a relay board 640. The interface board includes integrated circuit chips (e.g., ASICs) for controlling, for example, the synchronization, data capture, and data pre-processing for the PET modules. In one embodiment, the interface board may receive instructions from scanning software executed by a computer in the mobile cart for generating signals that are passed through the relay board to the PET modules. The data captured by the PET detector modules 650 and 660 may be then be output to the relay board 640 through one or more first data lines (e.g., a high-speed serial cable) 25, and then from the relay board to the interface board through one or more second signal lines (e.g., a high-speed serial PCi optical fiber) 35. One or more inter-module data lines (e.g., high-speed serial lines) 45 may connect the PET modules for coupling to the one or more first data lines. The clock distribution unit 620 generates timing signals for controlling scanning operations of the PET modules. The local power supply 630 provides power (e.g., 24V DC) for the PET modules. The daisy-chain connection of PET modules 650 and 660 may be replicated for the other modules, whether those modules are disposed in one ring or multiple stacked rings.

[0066] FIG. 6 illustrates an example of one ring of sixteen daisy-chained PET scanning modules 710 that may form the scanner of the imaging device described herein. This scanning modules 710 may correspond to the scanning modules 15i to 15N arranged in the ring illustrated in FIG. 2. A scanning controller 720 (which, for example, may be located in the mobile cart) in the disassembled view of FIG. 6 may be connected to the scanning modules. The control software for the modules may be located in this controller and/ or the controller may be connected to a computer in the cart which may be used to perform additional control operations and display of the brain images acquired by the PET scanning modules.

[0067] Referring to FIGS. 5 and 6, data acquisition may be coordinated by connecting the module electronics shown in FIG. 5 to a Dell Optiplex workstation (i7 processor, 32 Gb of RAM) running Windows 7 Professional OS. Flamamatsu proprietary data acquisition software written in C# computer language may be utilized to acquire raw data from the scanner. The system in this implementation may not possess external triggering capabilities, but these capabilities may be provided in other embodiments. In operation, the imaging device software may store singles data from all the detectors to a hard drive, e.g., located in the mobile cart 60 of FIG. 1. This data may then be accessed, for example, by Java-based software that determines coincidence events and converts the data to list mode data for further processing and reconstruction. In some applications, the clock distribution unit may provide a predetermined timing step (e.g., 15.625 ps) to allow a narrow timing window to be used for better rejection of random events. The timing window may be, for example, 1 ns window but a different timing window may be used in other embodiments.

Calibration and Preliminary Measurements

[0068] Energy calibration of the imaging system may be performed with 22Na and 137Cs sources, as well as 202 and 307 keV lines of 176Lu. Timing correction may be performed by rotating a line source filled with 18F placed outside the useful field of view (12.5 cm away from the center). The source may be rotated at an angular speed of 1 degree/second and measurements may be repeated a predetermined number of times (e.g., 5 times) with source activities around 250 pCi. Timing spectra may be obtained for each line-of-response (LOR) and their centers may be calculated by fitting the timing distributions to a Gaussian function. Locations of the line source may be calculated, for example, based on angular velocity and data timestamps. Timing calibration offsets may be determined based on differences between the centers of the timing spectra and predictions for each LOR, based on the location of the radioactive line source. Assessment of the sustainable count rate may be performed, for example, by placing a 74 MBq 18F source at various distances from the detectors faces.

NEMA NU-4-based Evaluations

[0069] The basic performance characteristics of the scanner may be assessed using the NEMA NU4- 2008 protocol. Specifically, spatial resolution may be measured by stepping a point source of 22Na (50pCi) mounted in a lcm3 block of acrylic to several radial positions at two axial positions: center of the scanner and 12 mm (1/4 of the FOV) away from the center. The full width-at-half-maximum (FWHM) of intensity profiles acquired from images of the point source are reported as spatial resolution. Detection sensitivity may be measured by stepping the same point source to 28 positions along the central axis of the scanner. These data may be used to calculate detection sensitivity at each location. Noise equivalent counting rate (NECR) can be measured using the “rat-size” phantom with a starting activity of 96 MBq of 18F. Image uniformity and spillover ratios may then be measured from images of the phantom.

Timing Resolution Measurements and Phantom Imaging [0070] To measure timing resolution, a 22Na source may be placed at the center of the scanner and a data set containing a plurality (e.g., 10 million events) may be acquired. Timing calibration offsets may be applied and an overall timing spectrum fit to a Gauss function. FWHM of the fit may be reported as timing resolution. Reconstructed images of a mini-hot-rod phantom with predetermined rod diameters (e.g., 1.2, 1.6, 2.4, 3.2, 4 and 4.8 mm) and the Floffman brain phantom can be obtained (with and without timing information) for comparison. They can be filled with 18F solution with activities of 3.7 and 5.6 MBq respectively. Data can then be acquired for a predetermined amount of time, e.g., 5 minutes. An energy threshold window of 350 to 700 keV and 1 ns gate time can then be applied in post-processing and phantom were reconstructed using, for example, a maximum- likelihood expectation-maximization (MLEM) reconstruction algorithm.

[0071] The aforementioned embodiments are especially beneficial for obtaining brain images for neurosurgical and traumatic brain injury (intensive care unit) ICU patients for whom intrahospital transportation and lying on the supine position may be contraindicated. Thus, advantageously, the scanner may be positioned on the patient’s head while in bed at various inclines that are best suited for patient’s intracranial pressure stability or compatibility with other medical interventions..

[0072] In terms of clinical performance, many large, fixed-position PET machines large dosage of radiotracers (e.g., 9-12 millicuries) are required to be delivered to the patient in order to obtain a proper brain image. Bedside scanning performed in accordance with one of more embodiments described herein may substantially reduce the amount of radiotracer dosages required. For example, performing the scan at the bedside of a patient may allow a dosage of radiotracers in the 1-2 millicuries range, since the patient does not need to be moved. Moreover, the rest period may be substantially reduced in the period of time between when the radiotracers are administered and the scans are taken. The lower exposure attained by the use of lower radiotracer dosages will create a safer environment for patients and medical staff. In one embodiment, additional types of imaging equipment may be incorporated into the support, including but not limited to electroencephalography (EEG), transcranial doppler (TCD), and/or near-infrared spectroscopy (NIRS).

[0073] In one embodiment, a combination of a ring of a specific-type of PET detectors, supported in a way that makes it mobile and able to be positioned on a patient head while lying down or upright in a bed or chair. As a result, multiple dangerous conditions may be avoided. For example, there is no need to transport the patient to an imaging machine. There is no need to put the patient into a flat position, which may introduce intracranial hypertension aspiration and oxygenation risks. Also, instead of a bed, scanning may be performed while the patient is in a chair and/ or in a completely upright, including standing, position. Other scanning positions include completely supine and multiple inclined angles.

[0074] Additionally, the number of skilled staff and support team may be substantially reduced. Also, instead of imaging a small sample of the brain, scanning may be performed to obtain information from a large swath of the cortex or even the whole brain for larger models. As a result, more accurate monitoring and interventions may be performed. Additionally, metabolic (physiologic) information of the brain may be obtained, rather than just anatomic, as well as information related to neurotransmitter activity, presence of dementia related brain plaques, inflammation, genetic expression (HDACs) and other specific targets enabled by a variety of radioligand PET tracers. Use of the embodiments may also be less or even non-invasive aside after injection of a low dose of radioactive tracer compared to standard PET imaging. [0075] Through these embodiments, improved detection of metabolic changes indicative of primary or secondary brain injury or disease may be achieved, which may lead to more expeditious treatment that may prevent brain deterioration and thus prevent disability or even death. In one embodiment, the imaging device may be used for lower dose detection of epileptic foci, achieving an accuracy similar to SPECT, without the need for transport to an epilepsy unit and reduced radioactivity exposure. Additional applications include helping to monitor a patient requiring surgery, during surgery or after surgery, to ensure either that the eloquent cortex is not accidentally removed or all tumor or epileptic foci is removed as much as feasible in a brain. Also before and directly after electroconvulsive therapy to see if additional treatment is needed or if the treatment worked. Additionally, assessing traumatic brain injury of athletes, military service members or anyone engaged in activities at higher risk for head injury, such a portable device could be used as a triage, or to assess whether or not a person had an injury that requires taking them our of the game, military theatre or sent for further treatment. Those with minor injuries could be scanned seated, and those with risk of severe TBI could be scanned at an angle best to prevent ischemic events.

[0076] An imaging system with the foregoing features was built and tested. The test results showed the following.

Energy Resolution and Counting Rate

[0077] FIG. 7 illustrates a graph showing a single-pixel energy spectrum obtained with a 22Na source. After calibration, the overall energy resolution of the scanner was 17.2% FWHM, and the single detector maximum-counting rate was 968 kHz.

NEMA NU-4-based Evaluations

[0078] FIG. 8 illustrates a graph showing a plot of spatial resolution as a function of the trans-axial displacement of the source from the center of the scanner. As indicated in this plot, the radial component degrades from 2.3 mm at the center to 3 mm at the edge of the useful field-of-view, 10 cm away from the center; reduction of the tangential and axial components is less severe.

[0079] FIG. 9 illustrates a plot of detection sensitivity with a peak sensitivity is 1.27%.

[0080] FIG. 10 illustrates a graph showing results from measurement of count rate capability. In this graph, peak NECR is 117.5 kcps at 75.25 MBq. The average counting rate of individual modules is 968 kcps, which agrees well with the ~1 MHz specified by the manufacturer.

[0081] FIG. 11 illustrates single slices of the non-TOF-corrected images of the NEMA quality assurance phantom. Analysis of the uniformity section of the QA phantom produced a value of 18.2+/-1.18 %. Spillover ratios were measured to be 17% and 23% for air and water filled areas of the phantom, respectively. Also, contrast recovery coefficients were measured to be 0.65, 0.42, 0.26, 0.10 and 0 for hot rod diameters of 5, 4, 3, 2, and 1 mm, respectively.

Timing Resolution

[0082] While single pixel timing resolutions were within manufacturer’s specifications of ~300 ps, system timing resolution was 462 ps FWHM. The difference in timing resolution between single pixel and system configurations was likely due to time jitter introduced by daisy-chaining the modules.

Phantom Imaging

[0083] FIGS. 12 and 13 illustrate images including slices of reconstructed volumes of mini-hot-rod and Floffman brain phantoms. The 2.4 mm-diameter rods are resolved. Incorporating time-of-flight information in the reconstruction improved the ability to resolve the smaller rods. Images of the Hoffman brain phantom also demonstrated improvement in the ability to resolve small structures. [0084] The commercial availability of TOF-capable imaging modules may make one or more embodiments of the imaging device available to a wider range of research groups. This access may enhance creation of custom PET scanners developed by smaller groups. This capability was demonstrated by constructing a relatively small diameter PET scanner that could be used as a small animal scanner or as an ambulatory brain-PET scanner.

[0085] An attractive feature of the new detector modules is the ability to utilize them to create relatively large scanners. The modules may be daisy-chained with minimal amount of wiring, which may reduce or eliminate noise-prone analog data transfer. The timing distribution board may also be arranged into a single timing source configuration, for example, supporting up to 128 detection modules in one embodiment. Multiple optical data links with rates of 10 Gbps per channel may reduce or minimize dead time associated with high data transfer rates.

[0086] The scanning modules may utilize the time-over-threshold method with a predetermined resolution (e.g., 4 ns) to estimate energy of the detected event. In some cases, this method may be prone to non-linearity and may require calibration. Application of an exponential model for the shape of the detected signal may yield a system energy resolution of 17.2%. This number may be further improved by fine adjustments of the threshold values for each MPPC.

[0087] In some example implementations, the performance of the system may achieve an energy resolution (17.2%). The results from NEMA NU4-2008-based testing demonstrated the ability to create a high-performing, small diameter PET scanners. Spatial resolution averaged approximately 2.2 mm FWHM 5cm from scanner center. These findings may seem too good for a scanner that utilizes 4.1 x 4.1 mm2 (pitch = 4.205 mm) detector elements, but it is important to note that the new modules utilize 1:1 scintillator element-to-SiPM coupling. Hence, there is much less spatial information lost due to light sharing. Spatial resolution is much closer, therefore, to the theoretical limit of one-half element width. Furthermore, in the built and tested system previously discussed, the peak sensitivity was 1.27%, which outperforms other types of scanners, and the peak NECR was 117.5 kcps. Image uniformity was 18.2+ /-1.18 %, spillover ratio for air-filled cylinder was 17%, and water-filled cylinder values were 23%. [0088] FIG. 14 illustrates another embodiment of a support 1500 for the brain imaging device. In this embodiment, the support includes a mechanism for controlling movement of the imaging device relative to the head of a patient. The mechanism includes a first pulley 1510, a second pulley 1520, and a reel 1530. The first pulley is mounted at a first position on a crossbar 1504 cantilevered above the head of the patient. The second pulley is mounted at a second position on the crossbar spaced from the first position. The reel is coupled to a post 1508 which is connected to the crossbar. A cable 1550 passes through the pulleys and includes a first end 1551 connected to and wound on the reel and a second end 1552 connected to the imaging device. In this embodiment, the second end of the cable 1550 is connected to a Y-shaped extension 1560 have ends connected to different sides of the imaging device. In operation, the imaging device is lowered onto the head of a patient when the reel is rotated in a first direction and is raised off the head of the patientwhen the reel is rotated in a second direction. [0089] FIG. 15 illustrates another embodiment of a support for the brain imaging device. A brace 1610 is shown as an L-shaped structure that supports a first frame 1605. The brace 1610 may be other structures and may be for example the cart 60, shown in FIG. 1. The first frame 1605 may be attached to the brace 1610 so that it is fixed or able to move in various directions relative to the brace 1610. A second frame 1615 is connected to the first frame via connectors 1620. The connectors 1620 allow for the second frame 1615 to move relative to the first frame 1615 in at least a vertical direction. The connectors 1620 may employ springs that allow for easy movement of the second frame 1615 but that also fix the position of the second frame 1615 once it is in the desired position. Additionally, a pin or clamps may be used to fix the position of the second frame 1615 relative to the first frame 1605 once the scanner 1625 is in the desired position. The second frame 1615 may be connected to the scanner 1625. Such a connection may allow for a swiveling motion that allows the scanner 1625 to rotate about the bottom of the second frame 1625. The first and second frames 1605 and 1615 are shown as rectangular structures, but may also be other more compact structures as well. [0090] FIG. 16 illustrates another embodiment of the scanner 10 of the imaging device. In this embodiment, the scanner includes twelve scanning modules 1710 arranged in a ring. Control, data, and power lines 1720 are coupled to connectors arranged at a central location of the scanner adjacent the central aperture that accommodates the head of the patient during scanning. The connectors are connected between the lines 1720 and respective ones of the scanning modules.

[0091] FIG. 17 shows another embodiment 1800 of the mobile imaging device disclosed herein. The device 1800 includes an imaging device 1825 mounted on cart 1860, which includes wheels 1862 and cabinet 1865. Aditional views of an imaging device 1825 mounted on cart 1860 are seen in FIGS. 18A to 18C. Imaging device 1825 is mounted to strut 1870, which is connected to cart 1860 by hinge 1895. Imaging device 1825 may be mounted to stmt 1870 via a hinge, allowing adjustment of the orientation of device 1825 relative to stmt 1870. Stmt 1870 may be moved from a lower position to an upper position by rotation about hinge 1895 in the direction of arrow C. Movement in the direction of arrow C is constrained by pin 1890, which travels reversibly in groove 1885 in stmt 1880.

[0092] FG. 18D shows an additional embodiment of the mobile imaging device disclosed herein. The device includes an imaging device 1825 mounted on wheeled cart 1860. Imaging device 1825 is mounted to stmt 1870, which is connected to cart 1860 by hinge 1895. Stmt 1870 may be moved from a lower position to an upper position by rotation about hinge 1895 in the direction of arrow C. Movement in the direction of arrow C is constrained by pin 1890, which travels reversibly in groove 1885 in stmt 1880. A gas spring 1900 is mounted between a front of cart 1860 and stmt 1970, and is configured to extend to allow upward movement of stmt 1879 in the direction of arrow C. Gas spring 1900 may resist downward movement of stmt 1870 in the direction of arrow C. A gas spring 1900 is a type of spring that, unlike a typical mechanical spring that relies on elastic deformation, uses compressed gas contained within an enclosed cylinder 1905 sealed by a sliding piston 1910 to pneumatically store potential energy and withstand external force applied parallel to the direction of the piston shaft.

[0093] Although the various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other example embodiments and its details are capable of modifications in various obvious respects. As is readily apparent to those skilled in the art, variations and modifications can be affected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not in any way limit the invention, which is defined only by the claims.

Claims

WE CLAIM:

1. A mobile imaging device, comprising: a plurality of scanning modules arranged in a ring pattern; a frame coupled to the scanning modules and including a central aperture surrounded by the scanning modules in the ring pattern; a support coupled to the frame and configured to move the frame at a position to allow a desired body part of a patient to be inserted into the central aperture; and a mobile cart coupled to the support to move the imaging device to a patient location, wherein the plurality of scanning modules include positron-emission tomography detectors.

2. The mobile imaging device of claim 1, wherein the desired body part of the patient is a head, an arm, a leg, a foot, a hand, or a torso.

3. The mobile imaging device of claim 1, wherein: the desired body part of the patient is a head, the frame has a substantially hemispherical shape with a flat bottom surface, and the flat bottom surface is arranged at a substantially horizontal position when the scanning modules are activated to obtain a brain image.

4. The mobile imaging device of claim 1, wherein: the desired body part of the patient is an arm, a leg, a foot, a hand, or a torso; the frame is substantially ring shaped; and the frame is configured to receive the desired body part when the scanning modules are activated to obtain an image.

5. The mobile imaging device of claim 1, wherein the support includes: a first section that is connected in a fixed position to the mobile cart; and at least a second section that moves relative to the first section to allow the frame to be moved into a scanning position relative to a patient.

6. The mobile imaging device of claim 1, wherein the scanning modules are electrically connected in a daisy chain.

7. The mobile imaging device of claim 1, wherein the mobile cart includes a controller configured to control operation of the scanning modules.

8. The mobile imaging device of claim 1, wherein the frame has a substantially hemispherical shape with a flat bottom surface and wherein the flat bottom surface is arranged at a substantially a horizontal position when the scanning modules are activated to obtain an image.

9. The mobile imaging device of claim 1, wherein the mobile imaging device comprises a plurality of scanning modules arranged in at least two stacked ring patterns.

10. The mobile imaging device of claim 1, wherein the plurality of scanning modules includes positron-emission tomography detectors, in combination with at least one of: an electrode sensor for use in recording an EEG; an MRI scanner; an optical sensor for use in recording infrared or ultraviolet light transmission or reflection; and a combination thereof.

11. A method of imaging a desired body part of a patient with a mobile imaging device, comprising: moving a mobile cart carrying the mobile imaging device to a patient location, wherein: the mobile imaging device comprises a frame including a central aperture, and the central aperture is surrounded by a plurality of scanning modules arranged in a ring pattern; moving the frame into a position allowing the desired body part of the patient to be inserted into the central aperture; inserting the desired body part into the central aperture; and sequentially activating the plurality of scanning modules to obtain an image of the desired body part, wherein the plurality of scanning modules include positron-emission tomography detectors.

12. The method of claim 11, wherein the desired body part of the patient is a head, an arm, a leg, a foot, a hand, or a torso.

13. The method of claim 11, wherein: the desired body part of the patient is a head, the frame has a substantially hemispherical shape with a flat bottom surface, and the flat bottom surface is arranged at a substantially horizontal position when the scanning modules are activated to obtain a brain image.

14. The method of claim 11, wherein: the desired body part of the patient is an arm, a leg, a foot, a hand, or a torso; the frame is substantially ring shaped; and the frame is configured to receive the desired body part when the scanning modules are activated to obtain an image.

15. The method of claim 11, wherein the scanning modules are electrically connected in a daisy chain.

16. The method of claim 11, wherein the mobile imaging device comprises a plurality of scanning modules arranged in at least two stacked ring patterns.

17. The method of claim 11, wherein the plurality of scanning modules includes positron- emission tomography detectors, in combination with at least one of: an electrode sensor for use in recording an EEG; an MRI scanner; an optical sensor for use in recording infrared or ultraviolet light transmission or reflection; and a combination thereof.