Author Of 1 Presentation
FLASH-ENABLED PROTON SBRT/SRS WITH IMPROVED HIGH-DOSE SPARING VIA SIMULTANEOUS DOSE AND DOSE RATE OPTIMIZATION (SDDRO)
Abstract
Background and Aims
To investigate the clinical potential of FLASH-RT for improving high-dose sparing of OAR, to enable SBRT/SRS that could otherwise fail to meet dose constraints with CONV-RT.
Methods
CONV-RT (via Bragg peaks (BP)) and FLASH-RT (via transmission beams (TB)) are compared with PBS proton therapy, i.e., CONV-RT planned with IMPT-BP, and FLASH-RT planned respectively with IMPT and SDDRO of TB. While IMPT only optimizes the dose distribution, SDDRO also optimizes the FLASH effect, i.e., to maximize the normal tissue volume receiving dose rate and dose thresholds pertinent to the FLASH effect, which was set to be 40Gy/s and 8Gy. The plan evaluation is based on the effective dose (de), i.e., the product of the physical dose (d) and FLASH dose modifying factor, which was set to be 0.7 when normal tissues meet both dose rate and dose thresholds.
Results
CONV-RT (IMPT-BP) was compared with FLASH-RT (IMPT and SDDRO). In terms of effective dose, (1) conformal index (CI) values show that SDDRO had the best target dose conformality; (2) mean doses at PTV-10mm (10mm expansion of PTV) suggest that SDDRO had the fastest high-dose falloff for normal tissues adjacent to the target.
Conclusions
Compared to CONV-RT (IMPT-BP), FLASH-RT via SDDRO improved high-dose sparing of OAR, which can potentially enable proton SBRT/SRS that could otherwise fail to meet dose constraints, e.g., the reduction of V12Gy from 44cc to 14cc to meet V12Gy≤15cc for this case to be eligible for brain SRS.