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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.
Rana, Suresh; Bennouna, Jaafar; Gutierrez, Alonso N; Rosenfeld, Anatoly B.
Afiliação
  • Rana S; Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, USA.
  • Bennouna J; Department of Radiation Oncology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA.
  • Gutierrez AN; Department of Medical Physics, The Oklahoma Proton Center, Oklahoma City, Oklahoma, USA.
  • Rosenfeld AB; Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, NSW, Australia.
J Appl Clin Med Phys ; 21(11): 124-131, 2020 Nov.
Article em En | MEDLINE | ID: mdl-33058380
ABSTRACT

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.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Terapia com Prótons Limite: Humans Idioma: En Revista: J Appl Clin Med Phys Assunto da revista: BIOFISICA Ano de publicação: 2020 Tipo de documento: Article País de afiliação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Terapia com Prótons Limite: Humans Idioma: En Revista: J Appl Clin Med Phys Assunto da revista: BIOFISICA Ano de publicação: 2020 Tipo de documento: Article País de afiliação: Estados Unidos