Scanned Proton Beam Performance and Calibration of the Shanghai Advanced Proton Therapy Facility

Hu, Shu; Yin, Chongxian; Zhang, Haiyang; Liu, Ming; Zhang, Manzhou; Liu, Zhao; Chu, K; Dai, Xiaolei; Moyers, Michael F.

doi:10.1016/j.mex.2019.08.001

Cited by 14 publications

(15 citation statements)

References 7 publications

(8 reference statements)

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“…This could also be the reason why this is the first report on dose fluctuation originating from spill change, as our center has a smaller spot size compared to many proton therapy centres 20–23 . For instance, the Hitachi ProBeat system in MD Anderson Cancer Center has a spot sizes of 5.1 to 14.4 mm, 21 Mevion S250i Hyperscan has a spot sizes of 4.1 to 16.4 mm 20 , IBA Proteus ONE has a spot sizes of 3 to 8 mm, 22 and the home‐made system in Shanghai Advanced Proton Therapy facility has a spot sizes of 2.5 to 5.5 mm 23 . A larger spot size could be obtained either due to the inherent large phase space of the extracted proton beam or performing measurement at a larger depth.…”

Section: Discussionmentioning

confidence: 99%

“…It is also intuitively understandable that a smaller spot size and smaller detectors will increase the sensitivity of the detector to such relative positional shifts,and thus leads to a greater fluctuation in charge measurement.This could also be the reason why this is the first report on dose fluctuation originating from spill change, as our center has a smaller spot size compared to many proton therapy centres. [20][21][22][23] For instance, the Hitachi ProBeat system in MD Anderson Cancer Center has a spot sizes of 5.1 to 14.4 mm, 21 Mevion S250i Hyperscan has a spot sizes of 4.1 to 16.4 mm 20 , IBA Proteus ONE has a spot sizes of 3 to 8 mm, 22 and the home-made system in Shanghai Advanced Proton Therapy facility has a spot sizes of 2.5 to 5.5 mm. 23 A larger spot size could be obtained either due to the inherent large phase space of the extracted proton beam or performing measurement at a larger depth.…”

Section: Discussionmentioning

confidence: 99%

“…[20][21][22][23] For instance, the Hitachi ProBeat system in MD Anderson Cancer Center has a spot sizes of 5.1 to 14.4 mm, 21 Mevion S250i Hyperscan has a spot sizes of 4.1 to 16.4 mm 20 , IBA Proteus ONE has a spot sizes of 3 to 8 mm, 22 and the home-made system in Shanghai Advanced Proton Therapy facility has a spot sizes of 2.5 to 5.5 mm. 23 A larger spot size could be obtained either due to the inherent large phase space of the extracted proton beam or performing measurement at a larger depth. The results in Figure 5a show that increasing the depth of measurement to yield a larger spot size could decrease the dose fluctuation from 5.9% (at 2 cm depth) to 1.3% (at 20 cm depth).…”

Section: Discussionmentioning

confidence: 99%

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The effect of spill change on reliable absolute dosimetry in a synchrotron proton spot scanning system

et al. 2023

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Background Absolute dosimetry measurement is an integral part of Treatment Planning System (TPS) commissioning and it involves measuring the integrated absorbed dose to water for all energies in a pencil beam scanning delivery system. During the commissioning of Singapore's first proton therapy center, a uniform scanned field with an Advanced Markus chamber method was employed for this measurement, and a large dose fluctuation of at least 5% was observed for 10% of the energy layers during repeated measurements. Purpose This study aims to understand the root cause of this fluctuation by relating the actual delivered spot information in the log file with the charge measurement by the ion chambers. Methods A dedicated pencil beam dose algorithm was developed, taking into account the log file parameters, to calculate the dose for a single energy layer in a homogeneous water phantom. Three energies, 70.2, 182.7, and 228.7 MeV were used in this study, with the 182.7 MeV energy exhibiting large dose fluctuation. The dose fluctuation was investigated as a function of detector's sizes (pinpoint 3D, Advanced Markus, PTW 34070, and PTW 34089) and water depth (2 , 6, and 20 cm). Twelve ion chambers measurements were performed for each chamber and depth. The comparison of the theoretically predicted integrated dose and the charge measurement served as a validation of the algorithm. Results About 5.9% and 9.6% dose fluctuation were observed in Advanced Markus and pinpoint 3D measurements at 2 cm depth for 182.7 MeV, while fluctuation of 1.6% and 1.1% were observed in Advanced Markus with 228.7 and 70.2 MeV at similar depth. Fluctuation of less than 0.1% was observed for PTW34070 and PTW 34089 for all energies. The fluctuation was found to diminish with larger spot size at 20 cm depth to 1.3% for 182.7 MeV. The theoretical and measured charge comparison showed a high linear correlation of R2>0.80${R^2} > 0.80$ for all datasets, indicating the fluctuation originated from the delivered spot characteristics. The cause of fluctuation was identified to be due to the spill change occurring close to the detector, and since the spot positional deviation profiles were different between two spills, this resulted in local hot spots between columns of spots. The actual position of spill change varies randomly during measurement, which led to a random occurrence of hot spot within the detector's sensitive volume and a fluctuating dose measurement. Conclusion This is the first report of a dose fluctuation greater than 5% in absolute dosimetry measurement with a uniform scanned field and the cause of the fluctuation has been conclusively determined. It is important to choose the MU and scanning pattern carefully to avoid spill change happening when the spot delivery is near the detector.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The effect of spill change on reliable absolute dosimetry in a synchrotron proton spot scanning system

et al. 2023

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“…In this system proton beams are extracted from synchrotron and drifted to the nozzle, by using the paired scanning magnets in horizontal (𝑋) and vertical (𝑌 ) directions. Proton beam spot is moved around the isocenter with energies between 70-235 MeV [12]. The advantage of this technique against scattering-based technique is that a range shifter is not required to shape the beam to the tumor volume, because the synchrotron accelerate the protons slowly and conform the tumor dose in the dimension lateral to the beam [12].…”

Section: Beam Modelingmentioning

confidence: 99%

“…Proton beam spot is moved around the isocenter with energies between 70-235 MeV [12]. The advantage of this technique against scattering-based technique is that a range shifter is not required to shape the beam to the tumor volume, because the synchrotron accelerate the protons slowly and conform the tumor dose in the dimension lateral to the beam [12]. The system characteristics are listed in table 1.…”

Section: Beam Modelingmentioning

confidence: 99%

Comparative assessment of passive scattering and active scanning proton therapy techniques using Monte Carlo simulations

et al. 2022

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Background: in this study, two proton beam delivery designs, i.e. passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo (MC) particle transport code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements. Method: a water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120–235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including Bragg peak width (BP W50), peak position, range, peak-to-entrance dose ratio, penumbra(90-10)%, penumbra(80-20)%, M 95% and dose volume histogram have been analyzed under the same conditions. Furthermore, the clinical test cases introduced by AAPM TG-119 were simulated in both beam delivery modes to compare the relevant clinical values obtained from Dose Volume Histogram (DVH) analysis. Results: the parametric comparison in the water phantom between the two techniques revealed that the value of peak-to-entrance dose ratio in PSPT is considerably higher than that from PBS by a factor of 8%. In addition, the BP_W50, penumbra(90-10)%, penumbra(80-20)%, and M 95% in PSPT was increased by a factor of 7, 51, 37, and 2.7%, respectively compared to the corresponding value obtained from PBS model. TG-119 phantom simulations showed that the difference of PTV mean dose between PBS and PSPT techniques are up to 1.8% while the difference of max dose to organ at risks (OARs) exceeds 50%. Conclusion: the results of this simulation show that although the passive scattering design method has a slightly higher ability to adjust the dose in target volume, but the active scanning proton therapy systems was superior in dose painting, and lower out-of-field dose compared to passive scattering design.

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SAPT: a synchrotron-based proton therapy facility in Shanghai

Zhang,

Li,

Shen

et al. 2023

NUCL SCI TECH

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Because of its excellent dose distribution, proton therapy is becoming increasingly popular in the medical application of cancer treatment. A synchrotron-based proton therapy facility was designed and constructed in Shanghai. The synchrotron, beam delivery system, and other technical systems were commissioned and reached their expected performances. After a clinical trial of 47 patients was finished, the proton therapy facility obtained a registration certificate from the National Medical Products Administration. The characteristics of the accelerator and treatment systems are described in this article.

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Scanned Proton Beam Performance and Calibration of the Shanghai Advanced Proton Therapy Facility

Abstract: Graphical abstract

Cited by 14 publications

References 7 publications

The effect of spill change on reliable absolute dosimetry in a synchrotron proton spot scanning system

The effect of spill change on reliable absolute dosimetry in a synchrotron proton spot scanning system

Comparative assessment of passive scattering and active scanning proton therapy techniques using Monte Carlo simulations

SAPT: a synchrotron-based proton therapy facility in Shanghai

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