TY - JOUR
T1 - Impact of magnetic field regulation in conjunction with the volumetric repainting technique on the spot positions and beam range in pencil beam scanning proton therapy
AU - Rana, Suresh
AU - Bennouna, Jaafar
AU - Gutierrez, Alonso N.
AU - Rosenfeld, Anatoly B.
N1 - Funding Information:
The authors thank Eric Jensen and Hassan Imrane (IBA Particle Therapy Team at the Miami Cancer Institute) for the discussions on the magnetic field regulation on an IBA ProteusPLUS PBS machine. The authors also wish to thank Fernando Escobar for his assistance with the data processing in this report.
PY - 2020/11
Y1 - 2020/11
N2 - Purpose: The objective of this study was to evaluate the impact of the magnetic field regulation in conjunction with the volumetric repainting technique on the spot positions and range in pencil beam scanning proton therapy. Methods: “Field regulation” — a feature to reduce the switching time between layers by applying a magnetic field setpoint (instead of a current setpoint) has been implemented on the proton beam delivery system at the Miami Cancer Institute. To investigate the impact of field regulation for the volumetric repainting technique, several spot maps were generated with beam delivery sequence in both directions, that is, irradiating from the deepest layer to the most proximal layer (“down” direction) as well as irradiating from the most proximal layer to the deepest layer (“up” direction). Range measurements were performed using a multi-layer ionization chamber array. Spot positions were measured using two-dimensional and three-dimensional scintillation detectors. For range and central-axis spot position, spot maps were delivered for energies ranging from 70–225 MeV. For off-axis spot positions, the maps were delivered for high-, medium, and low-energies at eight different gantry angles. The results were then compared between the “up” and “down” directions. Results: The average difference in range for given energy between “up” and “down” directions was 0.0 ± 0.1 mm. The off-axis spot position results showed that 846/864 of the spots were within ±1 mm, and all off-axis spot positions were within ±1.2 mm. For spots (n = 126) at the isocenter, the evaluation between “up” and “down” directions for given energy showed the spot position difference within ±0.25 mm. At the nozzle entrance, the average differences in X and Y positions for given energy were 0.0 ± 0.2 mm and −0.0 ± 0.4 mm, respectively. At the nozzle exit, the average differences in X and Y positions for given energy were 0.0 ± 0.1 mm and −0.1 ± 0.1 mm, respectively. Conclusion: The volumetric repainting technique in magnetic field regulation mode resulted in acceptable spot position and range differences for our beam delivery system. The range differences were found to be within ±1 mm (TG224). For the spot positions (TG224: ±1 mm), the central axis measurements were within ±1 mm, whereas for the off-axis measurements, 97.9% of the spots were within ±1 mm, and all spots were within ±1.2 mm.
AB - Purpose: The objective of this study was to evaluate the impact of the magnetic field regulation in conjunction with the volumetric repainting technique on the spot positions and range in pencil beam scanning proton therapy. Methods: “Field regulation” — a feature to reduce the switching time between layers by applying a magnetic field setpoint (instead of a current setpoint) has been implemented on the proton beam delivery system at the Miami Cancer Institute. To investigate the impact of field regulation for the volumetric repainting technique, several spot maps were generated with beam delivery sequence in both directions, that is, irradiating from the deepest layer to the most proximal layer (“down” direction) as well as irradiating from the most proximal layer to the deepest layer (“up” direction). Range measurements were performed using a multi-layer ionization chamber array. Spot positions were measured using two-dimensional and three-dimensional scintillation detectors. For range and central-axis spot position, spot maps were delivered for energies ranging from 70–225 MeV. For off-axis spot positions, the maps were delivered for high-, medium, and low-energies at eight different gantry angles. The results were then compared between the “up” and “down” directions. Results: The average difference in range for given energy between “up” and “down” directions was 0.0 ± 0.1 mm. The off-axis spot position results showed that 846/864 of the spots were within ±1 mm, and all off-axis spot positions were within ±1.2 mm. For spots (n = 126) at the isocenter, the evaluation between “up” and “down” directions for given energy showed the spot position difference within ±0.25 mm. At the nozzle entrance, the average differences in X and Y positions for given energy were 0.0 ± 0.2 mm and −0.0 ± 0.4 mm, respectively. At the nozzle exit, the average differences in X and Y positions for given energy were 0.0 ± 0.1 mm and −0.1 ± 0.1 mm, respectively. Conclusion: The volumetric repainting technique in magnetic field regulation mode resulted in acceptable spot position and range differences for our beam delivery system. The range differences were found to be within ±1 mm (TG224). For the spot positions (TG224: ±1 mm), the central axis measurements were within ±1 mm, whereas for the off-axis measurements, 97.9% of the spots were within ±1 mm, and all spots were within ±1.2 mm.
KW - magnetic field regulation
KW - pencil beam scanning
KW - proton energy
KW - proton therapy
KW - spot position
KW - volumetric repainting
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U2 - 10.1002/acm2.13045
DO - 10.1002/acm2.13045
M3 - Article
AN - SCOPUS:85092632226
VL - 21
SP - 124
EP - 131
JO - Journal of Applied Clinical Medical Physics
JF - Journal of Applied Clinical Medical Physics
SN - 1526-9914
IS - 11
ER -