WO2012051499A2

WO2012051499A2 - System and method for active radiation dose control

Info

Publication number: WO2012051499A2
Application number: PCT/US2011/056294
Authority: WO
Inventors: Terrance A. Harms; Kevin P. Mccollough
Original assignee: Mayo Foundation For Medical Education And Research
Priority date: 2010-10-15
Filing date: 2011-10-14
Publication date: 2012-04-19
Also published as: WO2012051499A3

Abstract

A system includes radiation detectors coupled to a carrier that is removably attachable to the region of interest (ROI) to ensure a predetermined spatial distribution of the detectors across ROI and, optionally, a processor integrating the system with radiation-delivery equipment. The detectors are adapted to generate data describing the radiation dosage delivered to ROI, while the processor compares the delivered dosage with radiation protocol, according to a method for irradiation of ROI, which method may further include triggering the radiation-delivery equipment to cause interruption of irradiation when delivered dosage exceeds a threshold.

Description

SYSTEM AND METHOD FOR ACTIVE RADIATION DOSE CONTROL

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims benefit of and priority from the U.S. Provisional

Patent Application No. 61/393,405 filed on October 15, 2010 and titled "System and method for active radiation dose control." The disclosure of the above-mentioned application is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present invention relates to a method and apparatus for real-time dosimetry, and fixed-geometry monitoring of the radiation dose received by a patient during a procedure involving radiation dose delivery.

BACKGROUND ART

[0003] Devices for monitoring of cumulative exposure to radiation have been used in the context of medical imaging systems and radiation therapy systems. Monitoring devices and techniques used for determining the cumulative exposure to radiation are often complex, include a relatively large number of different components and materials, or possess shortcomings that prevent them from being utilized adaptably. For example, thermoluminescent detectors (TLD), otherwise routinely employed in determining dose inhomogeneities in matching of X-ray and electron fields during radiotherapy, are generally unsuitable for online in vivo dosimetry and generally do not allow for separate measurements of dosages delivered by the contributing fields. Another popular monitoring technique utilizes a semiconductor radiation sensor such as a solid-state diode as a dosimeter probe that is attached to a patient undergoing the radiation exposure. To obtain information about the spatial distribution of the radiation over the patient's body, this technique may be expanded to include several diodes that are individually affixed to the skin of the patient, with the diodes' flexible leads connecting the individual diodes to a signal meter collecting the data representing the exposure dosage from each of the detectors. While such an approach may perform satisfactorily in many situations, the irreproducible positioning of the individual diodes limits its usefulness with new treatment measurement techniques such as computed tomography (CT), intensity modulated radiation therapy (IMRT), modulated arc delivery (such as, for example, VMAT or RapidArc), or conformal radiation therapy. The two latter techniques, for example, are known to direct the radiation onto the region of interest (ROI) and the radiation sensor at angles that can vary over a wide range during the treatment of the patient. For instance, RapidArc employs rotation of the radiation source through an angular range of up to 360 degrees while radiation beams are directed at the ROI. RapidArc is a trademark of Varian Medical Systems Technologies, Inc. of Palo Alto, CA. A multi-diode-based measurement in such cases cannot be carried out accurately in view of changes in orientation and mutual positioning of the diode sensors from measurement to measurement. This problem persists even with other forms of radiation exposure or treatment that use a single, fixed radiation angle, where it might be desirable to monitor the radiation dosages received by regions adjacent to the ROI in comparison with that received by the ROI itself.

[0004] There exists a need, therefore, in configuring the radiation-dosage measuring systems in such a way as to enable the reproducibility of the results from measurement to measurement and the ability of the measuring system and/or the user to impute the measurement data to a common reference. Moreover, with the change of position of either the radiation source or a patient being irradiated comes a requirement for a temporal capability to precisely define the delivered dose because the mutual positioning of the source and the ROI is time-dependent and such positioning is a factor in defining the require dose distribution. Measurement systems of the related art appear to be lacking such a temporal operational flexibility and a corresponding automated feedback mechanism. For example, the operation of the currently-existing CT equipment includes a choice of a functional protocol determined, in part, based on the size of the patient, patient's age, and patient's location inside the machine. Once the CT equipment has been engaged, the operational protocol runs to completion and, generally, provides few if any opportunities to halt and restart the operation, even if the operational protocol has been chosen incorrectly. In fact, the ability to interrupt the radiation procedure carried out with currently existing linear-accelerator-based equipment is limited.

[0005] Therefore, it would be desirable to have a system and method for accurately determining patient dose across a variety of environments and clinical operations. With such systems and methods, currently-employed measurement systems and processes would benefit from an added ability not to expose the patient to a radiation overdose by shutting-off the delivered radiation once the dosage received by a particular ROI and/or an aggregate dosage has exceeded a pre-determined threshold level.

SUMMARY OF THE INVENTION

[0006] Embodiments of the present invention provide a system and method for measuring a dosage of radiation delivered, according to a radiation protocol, by a medical system to a region of interest (ROI). The medical radiation-delivery system may include, but not limited to, a computed tomography (CT) system, a linear-accelerator-based system, a panoramic X-ray dental imaging system, or a system including a C-arm.

[0007] One embodiment of a system includes a carrier having an attachment system configured to removably affix the carrier to the ROI and radiation detectors coupled to the carrier so as to form an array having a predetermined spatial distribution across the ROI. Preferably, the radiation detectors are configured to generate dosage data characterizing a dosage of delivered radiation and, in a specific embodiment, the dosage data represents spatial distribution of radiation dosage across the ROI. The system may further include a processor that is coupled to radiation detectors to receive the generated dosage data and is configured to compare, for example, in realtime, the generated dosage data with parameters of the radiation protocol. In a specific

embodiment, the processor may be integrated with the medical radiation-delivery system. Based on the comparison of data, the processor generates triggering data and feeds-back these triggering data to the medical system so as to cause an interruption of the delivery of radiation when the dosage data exceed a threshold. The processor may be configured to receive the generated feedback data according to a predetermined time schedule. [0008] Another embodiment provides a method for irradiating a region of interest (ROI) by a medical system delivering radiation to the ROI according to the radiation protocol that includes radiation parameters. The method includes delivering radiation from the medical system, which may be a system forming an image of the ROI, to a measuring device that is removably attached to the ROI and that generates data characterizing a dosage of the delivered radiation. The method further includes comparing, for example, in real-time, the generated data with the parameters of the radiation protocol and generating triggering data based on the comparison. In addition, the method includes feeding-back the triggering data to the medical system thereby so as to cause an interruption of the delivery of radiation to the ROI when the dosage of delivered radiation exceeds a threshold. According to the method of the invention, comparison between the dosage data and the threshold may be done according to a predetermined time schedule.

[0009] Embodiments of the invention further offer a computer program product for providing an electronic input to a medical system delivering radiation, according to a radiation protocol, to a measuring device removably affixed to an irradiated region of interest (ROI). The computer program product includes a computer usable tangible medium having a computer readable program code thereon, the computer readable program including program code for determining a threshold radiation dosage based on the radiation protocol; program code for comparing a radiation dosage output generated by the measuring device with the threshold radiation dosage; and program code for generating triggering data when the radiation dosage output exceed the threshold radiation dosage. The measuring device includes radiation detectors placed, in a predetermined spatial arrangement, in a carrier of the measuring device. The program code causes the comparing of a radiation dosage output with a threshold dosage as a function of the spatial arrangement.

[0010] In addition, the computer readable program code may include program code for causing the medical system to interrupt the delivery of radiation to the ROI when the triggering data is delivered to the electronic input.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will be more fully understood by referring to the following Detailed

Description of Specific Embodiments in conjunction with the Drawings, of which: [0012] Fig. 1 is a perspective view of a radiation-measuring device in accordance with the present invention.

[0013] Fig. 2A is a perspective view of a radiation delivering medical system for use with the present invention.

[0014] Fig. 2B is a schematic block diagram of the system of Fig. 2A.

[0015] Fig. 2C is a schematic block diagram illustrating an operational interconnection between a dosimetry system of the invention and a radiation-delivery system.

[0016] Fig. 3 is a flow-chart setting forth exemplary steps of the method in accordance with the invention.

DETAILED DESCRIPTION

[0017] Embodiments of the present invention provide method and device for delivering radiation to a patient in a predictive fashion that includes verification of the delivered dosage against a reference, threshold dosage and provides feedback to the irradiating system to shut-off the irradiation process when such a threshold is exceeded.

[0018] References throughout this specification to "one embodiment," "an embodiment," "a related embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with the referred to "embodiment" is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. It is to be understood that no portion of disclosure, taken on its own and/or in reference to a figure, is intended to provide a complete description of all features of the invention.

[0019] In addition, in drawings, with reference to which the following disclosure may describe features of the invention, like numbers represent the same or similar elements wherever possible. In the drawings, the depicted structural elements are generally not to scale, and certain components are enlarged relative to the other components for purposes of emphasis and

understanding. It is to be understood that no single drawing is intended to support a complete description of all features of the invention. In other words, a given drawing is generally descriptive of only some, and generally not all, features of the invention. A given drawing and an associated portion of the disclosure containing a description referencing such drawing do not, generally, contain all elements of a particular view or all features that can be presented in this view in order to simplify the given drawing and the discussion, and to direct the discussion to particular elements that are featured in this drawing.

[0020] A skilled artisan will recognize that the invention may possibly be practiced without one or more of the specific features, elements, components, structures, details, or characteristics, or with the use of other methods, components, materials, and so forth. Therefore, although a particular detail of an embodiment of the invention may not be necessarily be shown in each and every drawing describing such embodiment, the presence of this detail in the drawing may be implied unless the context of the description requires otherwise. In other instances, well known structures, details, materials, or operations may be not be shown in a given drawing or described in detail to avoid obscuring aspects of an embodiment of the invention that are being discussed.

[0021] Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. Moreover, if the schematic flow chart diagram is included, it is generally set forth as a logical flow-chart diagram. As such, the depicted order and labeled steps of the logical flow are indicative of one embodiment of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Although various arrow types and line types may be employed in the flow-chart diagrams, they are understood not to limit the scope of the corresponding method. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted method. Without loss of generality, the order in which processing steps or particular methods occur may or may not strictly adhere to the order of the corresponding steps shown.

[0022] Consequently, the invention as recited in claims appended to this disclosure is intended to be assessed in light of the disclosure as a whole.

[0023] As shown in Fig. 1 , the present invention includes a radiation dose measuring system 100 that is designed to provide a desired reproducibility of the measurements across a region of interest (ROI) on the patient's body. Specifically, the system 100 includes a carrier 120 having arranged thereon, in a mutually fixed relationship, and multiple radiation detector devices 110 so as to form an array of devices. The radiation detector devices 110 may take on different forms depending upon the radiation being utilized. For example, the detector devices 110 may be MOSFET's, diodes, scintillation devices (such as fiber optics, crystals, and the like). The carrier 120, as illustrated, may be formed as a belt or a ribbon or an array structure. The carrier 120 is adapted to be removably attached to a chosen region of the patients body with an adjustable attachment system 130. The attachment system 130 may include a buckle, a belt, Velcro, or any other appropriate component facilitating an adjustable, removable, and reliable interconnection between the carrier 120 and to the patient's body. The spatial distribution of the plurality of detector devices 110 along or within the carrier 120 may be pre-set. In a related implementation, if required, such spatial distribution may be reconfigurable. The carrier 120 forms a support or, in a specific case, an envelope for a diode array. The carrier 120 may contain auxiliary electronics (not shown) for measuring the response of the detector devices 110 to incident radiation and a recorder for recording such a response at timed intervals. Depending upon the cost for the carrier 120 and detector devices 110, the system 100 may be disposable and/or reusable (for example, used multiple times for multiple patients). In addition, a data recorder (not shown) may also be configured separately from the carrier 120 and fitted within an external electronic block. In this case, appropriate electronic connectors or wireless technology may be employed to deliver the feedback data from the detector devices 110 to the external electronic block.

[0024] In practice, the measurement system 100 of the invention is removably attached to a medical patient and is operably connected with a medical system delivering radiation to a ROI associated with a patient. In one embodiment, such a medical system is a computed tomography (CT) system. In another embodiment, such a medical system is a system employing an accelerator, such as a linear accelerator or a cyclotron, or a system for photon based treatments. In another embodiment, such a medical system is a system employing particle based treatments, such as protons, ions, electrons, neutrons, and the like. With initial reference to Figs. 2A and 2B, schematically illustrating an exemplary X-ray CT-system, a CT imaging system 210 includes a gantry 212 representative of a "third generation" CT scanner. Gantry 212 has an X-ray source 213 that projects a fan-beam, or cone-beam, of X-rays 214 towards a detector array 216 on the opposite side of the gantry. The detector array 216 is formed by a number of detector elements 218 that together sense the projected x-rays that pass through a medical patient 215. Each detector element 218 produces an electrical signal that represents the intensity of an impinging X-ray beam and is, therefore, representative of the attenuation of the beam as it passes through the patient. During a scan to acquire X-ray projection data, the gantry 212 and the components mounted thereon rotate about a center of rotation 219 located within the patient 215.

[0025] The rotation of the gantry and the operation of the X-ray source 213 are governed by a control mechanism 220 of the CT system 210. The control mechanism 220 includes an X-ray controller 222 that provides power and timing signals to the X-ray source 213 and a gantry motor controller 223 that controls the rotational speed and position of the gantry 212. A data acquisition system ("DAS") 224 in the control mechanism 220 samples analog data from detector elements 218 and converts the data to digital signals for subsequent processing. An image reconstructor 225 receives sampled and digitized x-ray data from the DAS 224 and performs high- speed image reconstruction. The reconstructed image is received as an input by a computer 226, which stores the image in a mass storage device 229.

[0026] The computer 226 also receives commands and scanning parameters from an operator via console 230 that has a keyboard. An associated display 232, operably connected to the computer 226, allows the operator to observe the reconstructed image and other data from the computer 226. The commands and parameters submitted by an operator with the use of the console 230 are used by the computer 226 to provide control signals and information to the DAS 224, the x- ray controller 222 and the gantry motor controller 223. In addition, the computer 226 controls a table motor controller 234 that controls the operation of a motorized table 236 to position the patient 215 in the gantry 212.

[0027] In further reference to Figs. 2A through 2C, a medical radiation system 240 (such as the CT-system 210 or a photon-based or a particle-based treatment system) is shown that delivers radiation to the patient 215 according to a radiation protocol. The system 240 is in operational communication with a dosimetry system 250, which includes a radiation dosage measurement system 100 of Fig. 1. The dosimetry system 250 is configured as a peripheral, add-on system that externally provides the radiation system 240 with triggering data 252, as described below. Both the timed measurement of radiation, delivered from the medical radiation system 240 to the patient 215 wearing the radiation dose detecting system 100, and the generation of the triggering data 252 are judiciously controlled by a processor 254 through an electronic block 256. The block 256 collects dosage data 258, generated by and representing dose of radiation measured by the radiation detector array 110 of Fig. 1, and passes these data to the processor 256. The processor 256 compares these generated dosage data 258 in real-time with threshold parameters included in the radiation protocol according to which the medical system 240 operates. For the purposes of this disclosure and accompanying claims, a real-time act performed by a system is understood as an act that is subject to operational deadlines from a given event to the system's response to that event. For example, comparison of data in real time may be one triggered by the system and executed simultaneously with and without interruption of operation of the system during which such comparison is being performed. In a specific case, the radiation protocol includes spatial distribution of acceptable threshold parameters across the ROI, in which case the processor 256 compares the spatial distribution of radiation dose delivered to the ROI with the spatial distribution of threshold values. When the radiation system 240 is a CT-system, the threshold value or values may be predefined based on a CT-protocol estimate of what an entrance dose should be for a patient of a particular size. In a related embodiment, when the radiation system 240 is an accelerator-based system, the threshold value(s)may be determined based at least in part on a custom radiation plan, which is prescribed for a particular patient depending on the actual ROIs (for example, patient's organs) to be irradiated, so as to minimize the radiation delivered to surrounding normal, non-targeted tissue.

[0028] Based on the comparison between the generated dosage data 258 and a threshold, the processor 256 generates the triggering data 252 that is further passed to an internal operational sub-system of the medical system 240 (for example, to the computer 216) to effectuate either a shut- off of the system 240 or to block the radiation beam 214 delivered to the patient 215 when the delivered dosage exceeds a pre-defined threshold. It is appreciated that, in an alternative embodiment, the processor 256 may be not a part of the dosimetry system 250 but be integrated instead with the existing medical radiation system 240, in which case a shut-off of the radiation beam is effectuated internally to the system 240 .

[0029] Fig. 3 schematically illustrates a process flow for controlling the radiation delivered to a subject (patient) according to the present invention. Here, upon the attachment of the measuring device system 100 of Fig 1 to the patient and appropriate positioning of the patient with respect to the radiation beam, the irradiation procedure begins at step 310. At step 312, data representing the radiation dose delivered to any in- vivo measurement device system 100 is received and compared, in real-time, with a predetermined threshold at step 314. If the comparison indicates that the delivered dose exceeds the threshold, the processor 254 of Fig. 2C (or, alternatively, a processor of the medical radiation-delivery system 240 itself) generates the feedback data. The responsible processor further delivers or feeds-back 315 these data to the radiation system 240 as a input triggering the shut-off of the radiation beam, at step 316. (When it is determined, at step 314, that the predefined irradiation threshold has not been exceeded, the radiation system 240 is not turned off and the system continues delivery of radiation to the ROI at step 328, as discussed below). Following the shut-off of the radiation beam, at step 316, the system confirms whether the radiation parameters were correctly identified. For example, at step 318, a confirmation of whether the energy of the beam is accurate or whether blocking for a specific radiation pattern has been rigorously chosen is made. Based on the confirmation or, alternatively, the invalidation of the original radiation protocol, the operator proceeds at step 320 to either modify, 321, or override, 322, the shut-off of the radiation procedure. The modification 321 of the procedure causes the initiation of a new procedure, while the override 322 causes delivery of radiation to the ROI at step 328

Prior to concluding the irradiation procedure, the system 240 of the invention may optionally record and store, 332, on computer-readable tangible storage medium the information pertaining to the dose delivered to the patient and its spatial distribution as measured by individual radiation detector devices 110.

[0030] While the invention is described through the above-described exemplary

embodiments, it will be understood by those of ordinary skill in the art that modifications to, and variations of, the illustrated embodiments may be made without departing from the inventive concepts disclosed herein.

Claims

CLAIMS What is claimed is:

1. A system for measuring a dosage of radiation delivered by a medical system to a region of interest (ROI) according to a radiation delivery protocol, the system comprising:

a carrier having an attachment system configured to removably affix the carrier to the ROI; radiation detectors coupled to the carrier and forming an array having a predetermined spatial distribution across the ROI, the radiation detectors configured to generate dosage data characterizing a dosage of radiation delivered to the ROI; and

a processor coupled to radiation detectors to receive the generated dosage data and configured to:

receive parameters of the radiation delivery protocol and a threshold;

compare, in real-time, the generated dosage data with parameters of the radiation protocol to determine a variation of the dosage data from the parameters of the radiation delivery protocol,

compare the variation of the dosage data from the parameters of the radiation delivery protocol to a threshold, and

generate triggering data and feed-back the triggering data to the medical system to prompt an interruption of the delivery of radiation when the variation of the dosage data from the parameters of the radiation delivery protocol exceed the threshold.

2. A system according to claim 1, wherein the processor is configured to compare the generated dosage data with parameters of the radiation protocol at times defined by a time schedule of the radiation delivery protocol.

3. A system according to claim 1 wherein the medical system includes at least one of a computed tomography (CT) system and a linear-accelerator-based system.

4. A system according to claim 1, wherein the threshold includes threshold values corresponding to spatial positions of the radiation detectors across the ROI.

5. A method for irradiating a region of interest (ROI) by a medical system delivering radiation to the ROI according to a radiation delivery protocol, the radiation delivery protocol including radiation parameters, the method comprising:

delivering radiation from the medical system to a measuring device removably arranged about the ROI, the measuring device having an array of radiation sensors cooperated in a predetermined spatial distribution and generating data characterizing a spatial distribution of radiation dosage delivered to the ROI;

comparing, in real-time, the generated data with the parameters of the radiation delivery protocol; and

generating triggering data based on the comparison, the triggering data being fed-back to the medical system thereby causing the medical system to interrupt the delivery of radiation when a dosage of delivered radiation to at least a portion of the array exceeds a threshold.

6. A method according to claim 5, wherein the comparing is done according to a predetermined time schedule.

7. A method according to claim 5, wherein the medical system is configured to produce an image of the ROI.

8. A computer program product for providing an electronic input to a medical system delivering radiation, according to a radiation protocol, to a measuring device removably affixed to an irradiated region of interest (ROI), the computer program product comprising a computer usable tangible medium having a computer readable program code thereon, the computer readable program including:

program code for determining a threshold radiation dosage based on the radiation protocol; program code for comparing a radiation dosage output generated by the measuring device with the threshold radiation dosage; and

program code for generating triggering data when the radiation dosage output exceed the threshold radiation dosage.

9. A computer program product according to claim 8, wherein the computer readable program code further includes

program code for causing the medical system to interrupt the delivery of radiation to the ROI when the triggering data is delivered to the electronic input.

10. A computer program product according to claim 8, wherein the measuring device includes radiation detectors placed, in a predetermined spatial arrangement, in a carrier of the measuring device, and the comparing of a radiation dosage output with a threshold dosage is performed at a function of the spatial arrangement.