skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: MO-F-CAMPUS-T-04: Utilization of Optical Dosimeter for Modulated Spot-Scanning Particle Beam

Abstract

Purpose: To present the utilization of an optical dosimeter for modulated spot-scanning carbon-ion and proton beams during the acceptance test of Siemens IONTRIS system. Method and Materials: An optical dosimeter using phosphor scintillation was developed to map and interactively analyze the shapes and sizes of spots over 190 energies for ProTom modulated-scanning system. The dose response to proton had been characterized with proper pixel calibration at ProTom system. The dose response was further studied at 0.7 cm depths by uniform 8cm in-diameter fields of 424.89 MeV/u (E290) carbon-ions and 215.18MeV (E282) protons at IONTRIS system. The virtual source axial distances (vSAD) of carbonions and protons of IONTRIS system was investigated by measuring either variations of spot position or field size at five different locations to Isocenter. By measuring lateral profiles of uniform doses with varied thin-thicknesses of chest-board pattern and placing the scintillation plate at near to the distal edge, range variations at different off-axis-distances (rOAD) were examined. Relative accuracy and reproducibility of beam range were measured for three beam ranges with a ramping block at front of scintillation plate. Results: Similar dose response was observed for high energies of carbon ions and protons. Mean vSAD at X and Ymore » axes were 744.1 cm and 807.4cm with deviation of 7.4cm and 7.7cm, respectively. Variation of rOAD was within 0.35 mm over 10cm for both protons and carbon ions. Accuracy of measuring relative distal range using the ramping block was 0.2mm. Measured range over repeated three times for each range were within 0.25mm at same room, and within 1.0mm between four rooms. Conclusions: The optical dosimeter could efficiently measure the virtual source distance. And, to measure small range variation at different off-axial locations, and for the relative beam range between rooms during acceptance test of a modulated spot-scanning particle system.« less

Authors:
; ; ; ; ; ; ; ;  [1]
  1. Shanghai Proton and Heavy Ion Center, Pudong, Shangai (China)
Publication Date:
OSTI Identifier:
22562960
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 42; Journal Issue: 6; Other Information: (c) 2015 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; CALIBRATION; CARBON IONS; CHEST; DOSEMETERS; PARTICLES; PHOSPHORS; PROTON BEAMS; RADIATION DOSES; THICKNESS

Citation Formats

Hsi, W, Li, Y, Huang, Z, Sheng, Y, Deng, Y, Zhao, J, Zhao, F, Sun, L, and Moyers, M. MO-F-CAMPUS-T-04: Utilization of Optical Dosimeter for Modulated Spot-Scanning Particle Beam. United States: N. p., 2015. Web. doi:10.1118/1.4925479.
Hsi, W, Li, Y, Huang, Z, Sheng, Y, Deng, Y, Zhao, J, Zhao, F, Sun, L, & Moyers, M. MO-F-CAMPUS-T-04: Utilization of Optical Dosimeter for Modulated Spot-Scanning Particle Beam. United States. doi:10.1118/1.4925479.
Hsi, W, Li, Y, Huang, Z, Sheng, Y, Deng, Y, Zhao, J, Zhao, F, Sun, L, and Moyers, M. 2015. "MO-F-CAMPUS-T-04: Utilization of Optical Dosimeter for Modulated Spot-Scanning Particle Beam". United States. doi:10.1118/1.4925479.
@article{osti_22562960,
title = {MO-F-CAMPUS-T-04: Utilization of Optical Dosimeter for Modulated Spot-Scanning Particle Beam},
author = {Hsi, W and Li, Y and Huang, Z and Sheng, Y and Deng, Y and Zhao, J and Zhao, F and Sun, L and Moyers, M},
abstractNote = {Purpose: To present the utilization of an optical dosimeter for modulated spot-scanning carbon-ion and proton beams during the acceptance test of Siemens IONTRIS system. Method and Materials: An optical dosimeter using phosphor scintillation was developed to map and interactively analyze the shapes and sizes of spots over 190 energies for ProTom modulated-scanning system. The dose response to proton had been characterized with proper pixel calibration at ProTom system. The dose response was further studied at 0.7 cm depths by uniform 8cm in-diameter fields of 424.89 MeV/u (E290) carbon-ions and 215.18MeV (E282) protons at IONTRIS system. The virtual source axial distances (vSAD) of carbonions and protons of IONTRIS system was investigated by measuring either variations of spot position or field size at five different locations to Isocenter. By measuring lateral profiles of uniform doses with varied thin-thicknesses of chest-board pattern and placing the scintillation plate at near to the distal edge, range variations at different off-axis-distances (rOAD) were examined. Relative accuracy and reproducibility of beam range were measured for three beam ranges with a ramping block at front of scintillation plate. Results: Similar dose response was observed for high energies of carbon ions and protons. Mean vSAD at X and Y axes were 744.1 cm and 807.4cm with deviation of 7.4cm and 7.7cm, respectively. Variation of rOAD was within 0.35 mm over 10cm for both protons and carbon ions. Accuracy of measuring relative distal range using the ramping block was 0.2mm. Measured range over repeated three times for each range were within 0.25mm at same room, and within 1.0mm between four rooms. Conclusions: The optical dosimeter could efficiently measure the virtual source distance. And, to measure small range variation at different off-axial locations, and for the relative beam range between rooms during acceptance test of a modulated spot-scanning particle system.},
doi = {10.1118/1.4925479},
journal = {Medical Physics},
number = 6,
volume = 42,
place = {United States},
year = 2015,
month = 6
}
  • Purpose: To present dosimetric variations due to target movements with beam-gating windows of various respiratory-phase in homogeneous phantom irradiated by modulated spot-scanning carbon-ions and protons in Siemens IONTRIS system. Methods: For the safety and efficacy of proton therapy to treat three patients with lung cancer during our clinical trial, residual motion was required within 5mm. To study dosimetric variations due to respiratory movement, a target of 4.0cmx4.0cm with 2cm thick was moved with distances of 3.5mm, 4.4mm, 6.0mm, 8.3mm, and 11.0mm with beam-gating windows between various phases of inhalation or exhalation at a sin-wave breathing pattern. The target was irritatedmore » at 110mm depth by modulated carbon-ions with focus sizes of 4.1mm to 4.6mm, and a grid size of 1mm between spots. And, by modulated protons with focus sizes of 11.4mm to 13.6mm, and a grid size of 1.9mm between spots. A 4.0cmx4.0cm field size was used for both beams. EBT3 films was placed at the center of target for measurements. Delivery dose was 5.0 Gy with >1.0% uniformity over target. The uniformity and field size of each measured 2D lateral profiles were extracted. Results: By irradiating films to a doses at linear region of dose response, the uniformity and field size were extracted by measured optical density. The measured deviations from calculated field width and dose increase with increased motion amplitude. Larger non-uniformity was observed for carbonion with smaller focus size in comparing with protons. For movements of 4.4mm and 6.0mm, Optical Density uniformity of 3.80% and 5.66%were observed for carbon beam. But, is 3.46% for protons with 11.4mm movement. Conclusion: Our investigations showed that 5% optical density uniformity for carbon-ions and protons might be acceptable for treatments with 8.3mm movements in homogeneous phantoms. Dose variation introduced in complex anatomy of real patients need further investigation.« less
  • Purpose: Proton therapy aims to deliver a high dose in a well-defined target volume while sparing the healthy surrounding tissues thanks to their inherent depth dose characteristic (Bragg peak). In proton therapy, several techniques can be used to deliver the dose into the target volume. The one that allows the best conformity with the tumor, is called PBS (Pencil Beam Scanning). The measurement of the proton pencil beam spot profile (spot size) and position is very important for the accurate delivery of dose to the target volume with a good conformity. Methods: We have developed a fine segmented detector arraymore » to monitor the PBS. A prototype beam monitor using Cherenkov radiation in clear plastic optical fibers (cPOF) has been developed for continuous display of the pencil beam status during the therapeutic proton Pencil Beam Scanning mode operation. The benefit of using Cherenkov radiation is that the optical output is linear to the dose. Pedestal substraction and the gain adjustment between channels are performed. Spot profiles of various pencil beam energies(100 MeV to 226 MeV) are measured. Two dimensional gaussian fit is used to analyze the beam width and the spot center. The results are compared with that of Lynx(Scintillator-based sensor with CCD camera) and EBT3 Film. Results: The measured gaussian widths using fiber array system changes from 13 to 5 mm for the beam energies from 100 to 226 MeV. The results agree well with Lynx and Film within the systematic error. Conclusion: The results demonstrate good monitoring capability of the system. Not only measuing the spot profile but also monitoring dose map by accumulating each spot measurement is available. The x-y monitoing system with 128 channel readout will be mounted to the snout for the in-situ real time monitoring.« less
  • Purpose: To present the characteristics of positron-emitting-isotope (PEI) activity distributions on homogeneous and CIRS thorax phantoms irradiated by modulated spot-scanning carbon-ions and protons in Siemens IONTRIS system. Methods and Materials: Cylindrical homogeneous wax was irradiated by carbon-ions and protons of 10cm uniform square field with single-energy-layer ranges of 7cm, 16cm and 29cm. Images of PEI distributions were acquired over a period of 30 minutes at 10 minutes after each irradiation. Optimized uniform biological-equivalent doses of carbon-ions over a 5.0cm spherical target was delivered to CIRS phantom. Doses with range shifts in depths from 1mm to 6mm were also calculated andmore » delivered to evaluate the accuracy of measuring activated PEI distributions. Results: Activated PEI distribution on homogeneous phantoms showed sharper peak near distal edge with flatter distribution toward proximal depth by carbon-ions than by protons. For depths near at Bragg-peak, penetration-depth spreading for energies from 10MeV/u to 60 MeV/u are from 0.4mm to 10.3mm, and 1.2mm to 30.4mm for projectile-fragments by carbon-ions and target-fragments by protons, respectively. For depths proximal to Bragg-peak, target-fragments for both carbon-ions and protons had minimal energy dependence in depth. For complex dose distributions delivered to CIRS thorax phantom, similar PEI peak-like distributions were still observed for carbon-ions. And, the changes at locations and edges of measured PEI peak were correlated within 0.5mm of shifted ranges. Mean activities over 5.0cm spherical target were similar for CISR phantom irradiated by doses with various range shifts. Conclusions: Peak-like PEI distributions by carbon-ions with good correlation to distal edges in both homogeneous and CIRS thorax phantoms present the potential for the in-vivo range verification while additional efforts is needed for protons. Due to flat distributions for depths at 6mm proximal to distal edges, mean activity at target might be used for in-vivo dose verification of target.« less
  • Radiation therapy for head and neck malignancies can have side effects that impede quality of life. Theoretically, proton therapy can reduce treatment-related morbidity by minimizing the dose to critical normal tissues. We evaluated the feasibility of spot-scanning proton therapy for head and neck malignancies and compared dosimetry between those plans and intensity-modulated radiation therapy (IMRT) plans. Plans from 5 patients who had undergone IMRT for primary tumors of the head and neck were used for planning proton therapy. Both sets of plans were prepared using computed tomography (CT) scans with the goals of achieving 100% of the prescribed dose tomore » the clinical target volume (CTV) and 95% to the planning TV (PTV) while maximizing conformity to the PTV. Dose-volume histograms were generated and compared, as were conformity indexes (CIs) to the PTVs and mean doses to the organs at risk (OARs). Both modalities in all cases achieved 100% of the dose to the CTV and 95% to the PTV. Mean PTV CIs were comparable (0.371 IMRT, 0.374 protons, p = 0.953). Mean doses were significantly lower in the proton plans to the contralateral submandibular (638.7 cGy IMRT, 4.3 cGy protons, p = 0.002) and parotid (533.3 cGy IMRT, 48.5 cGy protons, p = 0.003) glands; oral cavity (1760.4 cGy IMRT, 458.9 cGy protons, p = 0.003); spinal cord (2112.4 cGy IMRT, 249.2 cGy protons, p = 0.002); and brainstem (1553.52 cGy IMRT, 166.2 cGy protons, p = 0.005). Proton plans also produced lower maximum doses to the spinal cord (3692.1 cGy IMRT, 2014.8 cGy protons, p = 0.034) and brainstem (3412.1 cGy IMRT, 1387.6 cGy protons, p = 0.005). Normal tissue V{sub 10}, V{sub 30}, and V{sub 50} values were also significantly lower in the proton plans. We conclude that spot-scanning proton therapy can significantly reduce the integral dose to head and neck critical structures. Prospective studies are underway to determine if this reduced dose translates to improved quality of life.« less
  • Purpose: To develop and validate a novel delivery strategy for reducing the respiratory motion–induced dose uncertainty of spot-scanning proton therapy. Methods and Materials: The spot delivery sequence was optimized to reduce dose uncertainty. The effectiveness of the delivery sequence optimization was evaluated using measurements and patient simulation. One hundred ninety-one 2-dimensional measurements using different delivery sequences of a single-layer uniform pattern were obtained with a detector array on a 1-dimensional moving platform. Intensity modulated proton therapy plans were generated for 10 lung cancer patients, and dose uncertainties for different delivery sequences were evaluated by simulation. Results: Without delivery sequence optimization,more » the maximum absolute dose error can be up to 97.2% in a single measurement, whereas the optimized delivery sequence results in a maximum absolute dose error of ≤11.8%. In patient simulation, the optimized delivery sequence reduces the mean of fractional maximum absolute dose error compared with the regular delivery sequence by 3.3% to 10.6% (32.5-68.0% relative reduction) for different patients. Conclusions: Optimizing the delivery sequence can reduce dose uncertainty due to respiratory motion in spot-scanning proton therapy, assuming the 4-dimensional CT is a true representation of the patients' breathing patterns.« less