Treatment planning and 3D dose verification of whole brain radiation therapy with hippocampal avoidance in rats

9th International Conference on 3D Radiation Dosimetry

Yoon, S.W.^1 ; Miles, D.^1 ; Cramer, C.^2 ; Reinsvold, M.^1 ; Kirsch, D.^1 ; Oldham, M.^1

Department of Radiation Oncology, Duke University Medical Center, Durham

NC, United States^1

Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem

NC, United States^2

关键词: Cognitive decline;    Conformal treatment;    Dose verification;    Large field of views;    Stereotactic radiosurgery;    Treatment planning;    Whole brain radiation therapies;    Whole brain radiotherapy;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/847/1/012004/pdf
DOI  :  10.1088/1742-6596/847/1/012004

来源: IOP

【 摘 要 】

Despite increasing use of stereotactic radiosurgery, whole brain radiotherapy (WBRT) continues to have a therapeutic role in a selected subset of patients. Selectively avoiding the hippocampus during such treatment (HA-WBRT) emerged as a strategy to reduce the cognitive morbidity associated with WBRT and gave rise to a recently published the phase II trial (RTOG 0933) and now multiple ongoing clinical trials. While conceptually hippocampal avoidance is supported by pre-clinical evidence showing that the hippocampus plays a vital role in memory, there is minimal pre-clinic data showing that selectively avoiding the hippocampus will reduce radiation-induced cognitive decline. Largely the lack of pre-clinical evidence can be attributed to the technical hurdles associated with delivering precise conformal treatment the rat brain. In this work we develop a novel conformal HA-WBRT technique for Wistar rats, utilizing a 225kVp micro-irradiator with precise 3D-printed radiation blocks designed to spare hippocampus while delivering whole brain dose. The technique was verified on rodent-morphic Presage®3D dosimeters created from micro-CT scans of Wistar rats with Duke Large Field-of-View Optical Scanner (DLOS) at 1mm isotropic voxel resolution. A 4-field box with parallel opposed AP-PA and two lateral opposed fields was explored with conformal hippocampal sparing aided by 3D-printed radiation blocks. The measured DVH aligned reasonably well with that calculated from SmART Plan Monte Carlo simulations with simulated blocks for 4-field HA-WBRT with both demonstrating hippocampal sparing of 20% volume receiving less than 30% the prescription dose.