Patent ID: 12186116

DETAILED DESCRIPTION

Brachytherapy is commonly used as an effective treatment for cervical, prostate, breast, esophageal and skin cancer, and can also be used to treat tumors in many other body sites. Interstitial brachytherapy is a cancer treatment in which radioactive material is placed closely to the target tissue of the affected site, such as in the prostate or breast.

The dose rate of brachytherapy refers to the level or intensity with which the radiation is delivered to the surrounding medium and is expressed in Grays per hour (Gy/h). In low-dose rate (LDR) brachytherapy, the rate of dose delivery typically less than 2 Gy/h. Pulsed-dose rate (PDR) brachytherapy involves short pulses of radiation, typically once an hour, to simulate the overall rate and effectiveness of LDR treatment. In high-dose rate (HDR) brachytherapy, the rate of dose delivery typically exceeds 12 Gy/h. During HDR brachytherapy, radiation sources are placed for a set duration (usually a number of seconds or minutes) before being withdrawn. The specific treatment duration will depend on many different factors, including the required isotope rate of dose delivery and the type, size and location of the cancer.

A range of imaging technologies (e.g., x-ray radiography, ultrasound, computed axial tomography (CT or CAT) scans and magnetic resonance imaging (MRI)) can be used to visualize the shape and size of the tumor and its relation to surrounding tissues and organs. The data from many of these sources can be used to create a3D map of the tumor and the surrounding tissues. Using this information, a plan of the optimal distribution of the radiation sources can be developed. This includes consideration of how the radiation should be placed and positioned. Errors or poor treatment setup might present a safety risk to the patient. Too little irradiation or too much irradiation must be avoided during treatment, as these can result in treatment failure and severe side-effects.

FIG.1illustrates an example interstitial brachytherapy treatment100of a tumor101in a patient's prostate gland103in accordance with aspects of this disclosure. The size and location of the tumor101relative to the patient's urethra105, bladder107and rectum109as shown is for illustration purposes. The tumor101may be any size and located anywhere in the prostate103.

As shown inFIG.1, an afterloader111is a radiotherapy machine being used to radiate the tumor101. The afterloader111comprises a retractable steel cable113. The afterloader111connects to a plastic or metallic catheter117by means of a radiation transfer tube115. A radiation source119encapsulated in metal travels inside the transfer tube115to the catheter117inserted into the patient's body, close to the tumor101. The radioactive source119is attached to the extremity of the steel cable113that is controlled by the afterloader111. The catheter117receives the radiation source119, and the afterloader111controls the movement, positioning and dwell time of the radiation source119within the tumor101as specified by a doctor's treatment plan.

Interstitial brachytherapy requires the precise placement of short-range radiation sources119(e.g., radioisotopes Cobalt-60, Iodine-125, Cesium-131, Iridium-192, etc.) directly at the site of a cancerous tumor101. Radiation treatment is intended to kill cancerous tissue while reducing exposure to healthy tissues. The radiation source119may travel throughout the catheter117length, while stopping at pre-determined periods in specific positions, thus providing irradiation of the surrounding tissues of the tumor101in an isotropic way. However, if the afterloader is not properly calibrated, healthy (e.g., non-cancerous) tissues may be irradiated in error.

Aspects of the present disclosure provide a tool for calibration of an afterloader radiotherapy machine to provide accurate radiation source position calibration and activity and dose calibration.FIG.2Aillustrates a top view of an exemplary embodiment of a system200for calibrating an afterloader in accordance with aspects of this disclosure.FIG.2Billustrates a top view of another exemplary embodiment of a system250for calibrating an afterloader in accordance with aspects of this disclosure.

The calibration systems200and250include a water-equivalent housing203on a printed circuit board (PCB)205. A proximity sensor207is located at one end of the housing203, and three radiation sensors209,211and213are placed within the housing203. To calibrate the afterloader and identify the optimal spatial and temporal distribution of radiation provided by an afterloader111, an afterloader catheter117is inserted into the calibration system housing203at insertion point201and a radiation source119is directed through the calibration system200while radiation is measured by radiation sensors209,211and213. The proximity sensor207may also measure the distance to the radiation source119that is encapsulated in metal. The embodiment 250 inFIG.2Billustrates that the three radiation sensors209,211and213may be placed at various locations. Additionally,FIG.2Bshows that a calibration system may use a thermostat215to measure the temperature of the system250during calibration.

FIG.3illustrates a partially opened side view of an exemplary embodiment of a system for calibrating an afterloader in accordance with aspects of this disclosure.FIG.3shows that a calibration system may use a metal plate335. Additionally,FIG.3shows that each of the three radiation sensors (209,211,213inFIGS.2A and2B) may comprise a scintillator309,319,329and a photodetector313,323,333respectively.

Aspects of the present disclosure provide systems (e.g., systems200,250and300illustrated inFIGS.2A,2B and3) for detecting radiation produced by a radiation source that is controlled by an afterloader. The intensity, position and velocity of the detected radiation can be used as feedback to calibrate the afterloader.

As shown inFIG.3, each of the plurality of scintillators309,319,329are positioned near each of the plurality of light detection units313,323,333. Each scintillator309,319,329is configured to produce light in a presence of radiation from a radioactive source of radiation119. The level of the light produced by each scintillator309,319,329is proportional to the level of the radiation incident to each scintillator309,319,329. The characteristics (or nature) of the scintillators signal produced is dependent on the type of radiation. For example, gamma, x-rays and protons will produce different signals. Light signals produced according one type of radioactive material may have a spectrum that differs from the spectrum of light signals produced according another type of radioactive material. Each light detection unit313,323,333is configured to produce an electrical signal in a presence of the light from one scintillator of the plurality of scintillators309,319,329. The level of the electrical signal produced by each light detection unit313,323,333is proportional to the light incident to each light detection unit313,323,333. Thus the level of the electrical signal produced by each light detection unit313,323,333is proportional to the level of the radiation incident to each scintillator309,319,329. Each light detection unit of the plurality of light detection units313,323,333may be located near coupled to one scintillator of the plurality of scintillators309,319,329via an optical fiber.

A processor337is configured to calculate a location of the radiation source according to the electrical signals from the plurality of light detection units313,323,333. The processor337may be configured to calculate the location of the radiation source by trilateration (or triangulation) according to the electrical signals from the plurality of light detection units313,323,333. The processor may also be configured to calculate a velocity of the radiation source119according to the electrical signals from the plurality of light detection units.

The plurality of scintillators309,319,329may be enclosed in a water-equivalent housing203. The radiation source119may be selectively inserted into the water-equivalent housing203via a probe (e.g., plastic or metal catheter117) of the afterloader. The water-equivalent housing203may comprise an inductive proximity detector207configured to detect a presence of the probe in the water-equivalent housing. Placement of the catheter117may be detected by the proximity sensor207. A movement of the radiation source119may be detected by the proximity sensor207. To maintain a constant temperature of the system300during radiation measurement, the temperature of the metal plate335is controlled by the thermostat215.

FIG.4Aillustrates an exemplary radiation sensor in a system for calibrating an afterloader in accordance with aspects of this disclosure. According to one embodiment, the radiation sensor209comprises a scintillator309and a photodetector313. The scintillator309collects radiation and converts this radiation into a luminous signal with an intensity that is proportional to the level of incident radiation. The scintillator309may be an organic scintillator (e.g., BC-400, BC-404, BC-412, and BCF-12 as manufactured by Saint-Gobain) or an inorganic scintillators. BCF-12, for example, is a scintillating optical fibre. The photodetector313is located near the scintillator309and converts the luminous signal into an electrical signal (e.g., voltage or current) with a magnitude that is proportional to the level of incident illumination. The photodetector313typically comprises a fast signal response to allow for identification of a scintillator309luminous signal proportional to the radiation source strength and relative position. For example, a radiation source (e.g., iridium192) will decay over time and the use of three photodetectors313,323and333and three scintillators309,319and329may be used to determine the radiation source strength and relative position.

FIG.4Billustrates another exemplary radiation sensor in a system for calibrating an afterloader in accordance with aspects of this disclosure. The photodetector313(e.g., photodiode) may be coupled to the scintillator309via an optical fiber401. The photodetector313may also comprise a built-in lens and/or optical filter window to select one or more wavelengths emitted from a particular scintillator309.

FIG.5illustrates a first exemplary arrangement500of radiation sensors in a system for calibrating an afterloader in accordance with aspects of this disclosure. According to an example embodiment, the radiation source detector of a calibration system is capable to determine the position of a radiation source119by trilateration. The system can be used to calibrate afterloader radiation source positioning inside a plastic or metallic tube such as a catheter.

The exemplary arrangement500inFIG.5comprises radiation probe #1501, radiation probe #2503, and radiation probe #3505. These probes may be used in calibration systems200,250and300as described with respect toFIGS.2A,2B and3. Radiation probe #1501is illustrated with further detail. Radiation probe #1501comprises a scintillator509and a photodetector513that operate is a similar way as scintillator309and a photodetector313inFIG.4. Additionally, radiation probe #1501may also comprise a fiducial marker507and/or an optical fiber511. The fiducial marker507may comprise a gold piece that allows the radiation probe #1501to be located with an imaging scanner, such as an MRI or CT scanner. The optical fiber511allows the photodetector513to be located at a distance from the scintillator509.

When the radiation source119is in proximity, radiation probe #1501, radiation probe #2503, and radiation probe #3505produces an electrical signal that is inversely proportional to a function of the distance R1, R2, R3between the radiation source119and the scintillator of each respective radiation probe501,503,505. For example, an electrical signal thus produced may be inversely proportional to the square of the distance between radiation source119and the point509where radiation is converted to light. Each calculated distances R1, R2, R3produces a sphere541,543,545of possible locations of radiation source119. The intersection of the spheres541,543,545identify the radiation source119location.

FIG.6illustrates a second exemplary arrangement600of radiation sensors in a system for calibrating an afterloader in accordance with aspects of this disclosure. For example, the expected location of the radiation source119controlled by afterloader111ofFIG.1may be designated in Cartesian coordinates as (0, 0, 0). If the afterloader111is not calibrated, the actual location of the radiation source119may be different than the expected location. The difference between the actual location of the radiation source119and the expected location may be designated in Cartesian coordinates as (Δx, Δy, Δz) as shown inFIG.6. An embodiment with the sensors located at (0, 1, −1), (1, 1, 0) and (1, 0, 1) will be described in conjunction withFIG.7.

FIG.7illustrates an exemplary method900for detecting radioactive material and calibrating an afterloader in accordance with aspects of this disclosure. The method700comprises inserting a catheter of the afterloader into a water-equivalent housing at701. Once the catheter is received by the housing, a radiation source is moved through the catheter via the afterloader at703. The temperature of the PCB may be maintained by a thermostat connected to a temperature-controlled metal plate that extends through the housing.

A plurality of scintillators are located at different locations within the water-equivalent housing. Each scintillator is used to convert radiation from the radiation source into a light signal at705. A level of the light produced by each scintillator is proportional to a level of the radiation incident at each of the plurality of locations. The plurality of scintillators are enclosed in the water-equivalent housing.

The light produced by each scintillator is converted to an electrical signal using each of a plurality of light detection units (e.g., photodetectors) at707. A level of the electrical signal produced by each light detection unit is proportional to the light incident to each light detection unit. Each light detection unit of the plurality of light detection units is coupled to one scintillator of the plurality of scintillators. The light detection units may be located within the housing. Alternatively, each light detection unit may be coupled to one scintillator via an optical fiber, and the light detection units can be placed outside of the housing.

At709, a processor is operable to calculate a location of the radiation source according to the electrical signals from the plurality of light detection units. The location of the radiation source may be determined according to the electrical signals from the plurality of light detection units. The velocity of the radiation source may also be calculated according to the electrical signals from the plurality of light detection units and the known distances between each scintillator.

While the present method and/or system has been described with reference to certain implementations, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present method and/or system. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, it is intended that the present method and/or system not be limited to the particular implementations disclosed, but that the present method and/or system will include all implementations falling within the scope of the appended claims.

As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (i.e. hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise first “circuitry” when executing a first one or more lines of code and may comprise second “circuitry” when executing a second one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y”. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y and z”. As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “e.g.,” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, circuitry is “operable” to perform a function whenever the circuitry comprises the necessary hardware and code (if any is necessary) to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, etc.).