Correlation between local instantaneous dose rate and oxygen pressure reduction during proton pencil beam scanning irradiation.
Phys Imaging Radiat Oncol
; 31: 100614, 2024 Jul.
Article
em En
| MEDLINE
| ID: mdl-39157294
ABSTRACT
Background and purpose:
Oxygen dynamics may be important for the tissue-sparing effect observed at ultra-high dose rates (FLASH sparing effect). This study investigated the correlation between local instantaneous dose rate and radiation-induced oxygen pressure reduction during proton pencil beam scanning (PBS) irradiations of a sample and quantified the oxygen consumption g-value. Materials andmethods:
A 0.2 ml phosphorescent sample (1 µM PtG4 Oxyphor probe in saline) was irradiated with a 244 MeV proton PBS beam. Four irradiations were performed with variations of a PBS spot pattern with 5 × 7 spots. During irradiation, the partial oxygen pressure (pO2) was measured with 4.5 Hz temporal resolution with a phosphorometer (Oxyled) that optically excited the probe and recorded the subsequently emitted light. A calibration was performed to calculate the pO2 level from the measured phosphorescence lifetime. A fiber-coupled scintillator simultaneously measured the instantaneous dose rate in the sample with 50 kHz sampling rate. The oxygen consumption g-value was determined on a spot-by-spot level and using the total pO2 change for full spot pattern irradiation.Results:
A high correlation was found between the local instantaneous dose rate and pO2 reduction rate, with a correlation coefficient of 0.96-0.99. The g-vales were 0.18 ± 0.01 mmHg/Gy on a spot-by-spot level and 0.17 ± 0.01 mmHg/Gy for full spot pattern irradiation.Conclusions:
The pO2 reduction rate was directly related to the local instantaneous dose rate per delivered spot in PBS deliveries. The methodology presented here can be applied to irradiation at ultra-high dose rates with modifications in the experimental setup.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Phys Imaging Radiat Oncol
Ano de publicação:
2024
Tipo de documento:
Article