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Concurrent geometry and dose reconstruction in image guided radiation therapy
Proceedings of the 44th Annual ASTRO Meeting
207
In Vivo Dosimetry During External Beam Radiotherapy Utilizing an Implantable Telemetric and Dosimetric Device
C.W. Scarantino1, C. Rini1, N. Bolick1, D. Ruslander2, G. Mann1, T. Carrea1, T. Nagle3, R. Black1 1 Sicel Technologies Inc, Morrisville, NC, 2Department of Radiation Oncology, NC State School of Veterinary Medicine, Raleigh, NC, 3Electrical and Computer Engineering, NC State University, Raleigh, NC Purpose/Objective: A reliable method for measuring the dose of radiation delivered at depth does not exist. An implantable telemetric device has been developed to monitor, in real time, the dose delivered at the target site. In addition, this study was designed to determine the degree of migration associated with implantation. Materials/Methods: The implantable device is a product of Sicel Technologies Inc (STI, Morrisville, NC). It consists of a radiation dosimeter (MOSFET), microchip, and antenna enclosed in a glass capsule and measuring 3mm ⫻ 25mm. STI in conjunction with the Dept. of Radiation Oncology at the North Carolina State Univ. School of Veterinary Medicine developed a protocol to implant the device in privately owned dogs with spontaneous malignancies that were candidates for radiation therapy. Six dogs were entered on study as of 2/20/02. Four dogs were implanted post resection (in the tumor bed) and 2 in periphery of the tumor (gross tumor volume -GTV). Following insertion and planning CT scans, isodose plans were obtained and the isodose line most closely associated with the device was identified. Daily radiation dose measurements were obtained with the STI reader. The reader provides inductive power to obtain the radiation dose, in real time, from the implanted device. Serial CT scans or diagnostic films were obtained to determine migration. Clinical evaluations of the site of injection were done weekly. Results: We did not observe any migration of the device in 5 dogs and only a 2mm migration in one dog. Serial CT and diagnostic films were used to determine migration. The devices have been in place from 1 to 6 months with no adverse effects. One dog received pre-op RT and at the time of resection the device was retrieved and significant encapsulation was noted around the device. Histologically, a thick fibrous capsule lined the implant site. In 4 dogs the devices were located within 1 cm of the surface and the variation between the expected and observed dose of radiation was 1-3%. In one dog the device was located ⬎ 1.5cm below the surface and the variation between expected and observed dose was 8.9%. Dosimetry was not done in one dog. Conclusions: The implantable telemetric device developed by STI is the first dosimetry system with the capability to provide accurate in vivo measurements of radiation dose. The information can be obtained daily and in real time. The device does not appear to create any adverse side effects or migrate within the body. It has the potential to provide the clinician with information on the variations of the daily delivered radiation dose.
208
Concurrent Geometry and Dose Reconstruction in Image Guided Radiation Therapy
K. Sheng1, R. Jeraj1, T.R. Mackie1, B.R. Paliwal2, R.K. Das2, W. Tome2 1 Department of Medical Physics, University of Wisconsin, Madison, WI, 2Department of Human Oncology, University of Wisconsin, Madison, WI Purpose/Objective: Monitoring the patient set up and target position during radiation therapy and especially in IMRT is becoming very important. On board MVCT has been investigated for years and proven to be an effevtive solution. However, MVCT causes extra dose to the patient and prolongs the treatment time. Our study is a computer simulation analysis focusing on overcoming these problems. Materials/Methods: A cylindrical water equivalent phantom with a C-shaped target and a square critical tissue inside it has been used. The detector, which is a slab of water equivalent material, is presented as a part of an extended phantom (Fig 1). The dose from 6 MV photon beams are computed by convolution and superposition code through the phantom and detector (Fig 3). A 360-degree rotation (Fig 2 shows the detail of the rotation) of the phantom gives full sets of projection data (i.e. sinogram) available for image reconstruction (Fig 4).Optimization (Fig 6 shows the optimized dose distribution.) gives the output beam intensity profile (Fig 5), which projects an incomplete set of sinogram data on the detector. This set of data is normalized and inserted back to a previous background data set and then back projected to get the image, which is a rough estimate of the position and shape of phantom. We proposed two methods to improve the image quality. a. Iteratively put the resultant image back into the imaging process. Since, this process is done by computer simulation, there is no extra dose to patient. b. Retain some of the imaging views with all MLC leaf opened but reduce the total number. These views will provide data to fill in the missing information left by sparse treatment beams and improve image quality but at the same time keeping the dose to the normal tissue reasonably low. Results: The quality of image from treatment beams is flawed because too much information was dropped using only the optimized MLC output (Fig 7). However, this quality can be improved by Iteration algorithm, which gives a better definition of the target shape. (Fig 8). With additional views from MVCT, image with better quality is acquired. (Fig 9) Conclusions: Our study shows that IGRT by photon beams is an effective method to reduce the cost of dose and time to patient. It is realistic to find a better balance between imaging dose and imaging quality. With the refinement of imaging algorithms, an optimized solution is expected. This study was partially supported by NIH/NCI Grant # 1PO1 CA88960.
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207
In Vivo Dosimetry During External Beam Radiotherapy Utilizing an Implantable Telemetric and Dosimetric Device
C.W. Scarantino1, C. Rini1, N. Bolick1, D. Ruslander2, G. Mann1, T. Carrea1, T. Nagle3, R. Black1 1 Sicel Technologies Inc, Morrisville, NC, 2Department of Radiation Oncology, NC State School of Veterinary Medicine, Raleigh, NC, 3Electrical and Computer Engineering, NC State University, Raleigh, NC Purpose/Objective: A reliable method for measuring the dose of radiation delivered at depth does not exist. An implantable telemetric device has been developed to monitor, in real time, the dose delivered at the target site. In addition, this study was designed to determine the degree of migration associated with implantation. Materials/Methods: The implantable device is a product of Sicel Technologies Inc (STI, Morrisville, NC). It consists of a radiation dosimeter (MOSFET), microchip, and antenna enclosed in a glass capsule and measuring 3mm ⫻ 25mm. STI in conjunction with the Dept. of Radiation Oncology at the North Carolina State Univ. School of Veterinary Medicine developed a protocol to implant the device in privately owned dogs with spontaneous malignancies that were candidates for radiation therapy. Six dogs were entered on study as of 2/20/02. Four dogs were implanted post resection (in the tumor bed) and 2 in periphery of the tumor (gross tumor volume -GTV). Following insertion and planning CT scans, isodose plans were obtained and the isodose line most closely associated with the device was identified. Daily radiation dose measurements were obtained with the STI reader. The reader provides inductive power to obtain the radiation dose, in real time, from the implanted device. Serial CT scans or diagnostic films were obtained to determine migration. Clinical evaluations of the site of injection were done weekly. Results: We did not observe any migration of the device in 5 dogs and only a 2mm migration in one dog. Serial CT and diagnostic films were used to determine migration. The devices have been in place from 1 to 6 months with no adverse effects. One dog received pre-op RT and at the time of resection the device was retrieved and significant encapsulation was noted around the device. Histologically, a thick fibrous capsule lined the implant site. In 4 dogs the devices were located within 1 cm of the surface and the variation between the expected and observed dose of radiation was 1-3%. In one dog the device was located ⬎ 1.5cm below the surface and the variation between expected and observed dose was 8.9%. Dosimetry was not done in one dog. Conclusions: The implantable telemetric device developed by STI is the first dosimetry system with the capability to provide accurate in vivo measurements of radiation dose. The information can be obtained daily and in real time. The device does not appear to create any adverse side effects or migrate within the body. It has the potential to provide the clinician with information on the variations of the daily delivered radiation dose.
208
Concurrent Geometry and Dose Reconstruction in Image Guided Radiation Therapy
K. Sheng1, R. Jeraj1, T.R. Mackie1, B.R. Paliwal2, R.K. Das2, W. Tome2 1 Department of Medical Physics, University of Wisconsin, Madison, WI, 2Department of Human Oncology, University of Wisconsin, Madison, WI Purpose/Objective: Monitoring the patient set up and target position during radiation therapy and especially in IMRT is becoming very important. On board MVCT has been investigated for years and proven to be an effevtive solution. However, MVCT causes extra dose to the patient and prolongs the treatment time. Our study is a computer simulation analysis focusing on overcoming these problems. Materials/Methods: A cylindrical water equivalent phantom with a C-shaped target and a square critical tissue inside it has been used. The detector, which is a slab of water equivalent material, is presented as a part of an extended phantom (Fig 1). The dose from 6 MV photon beams are computed by convolution and superposition code through the phantom and detector (Fig 3). A 360-degree rotation (Fig 2 shows the detail of the rotation) of the phantom gives full sets of projection data (i.e. sinogram) available for image reconstruction (Fig 4).Optimization (Fig 6 shows the optimized dose distribution.) gives the output beam intensity profile (Fig 5), which projects an incomplete set of sinogram data on the detector. This set of data is normalized and inserted back to a previous background data set and then back projected to get the image, which is a rough estimate of the position and shape of phantom. We proposed two methods to improve the image quality. a. Iteratively put the resultant image back into the imaging process. Since, this process is done by computer simulation, there is no extra dose to patient. b. Retain some of the imaging views with all MLC leaf opened but reduce the total number. These views will provide data to fill in the missing information left by sparse treatment beams and improve image quality but at the same time keeping the dose to the normal tissue reasonably low. Results: The quality of image from treatment beams is flawed because too much information was dropped using only the optimized MLC output (Fig 7). However, this quality can be improved by Iteration algorithm, which gives a better definition of the target shape. (Fig 8). With additional views from MVCT, image with better quality is acquired. (Fig 9) Conclusions: Our study shows that IGRT by photon beams is an effective method to reduce the cost of dose and time to patient. It is realistic to find a better balance between imaging dose and imaging quality. With the refinement of imaging algorithms, an optimized solution is expected. This study was partially supported by NIH/NCI Grant # 1PO1 CA88960.
123