Active and Passive Respiratory Motion Management for Radiation Therapy

Date(s) - 12/13/2012
10:00 am

Ashley Smith, BME-Medical Physics PhD Student

PhD Oral Proposal

Respiratory motion management is important in radiotherapy to accurately deliver a high radiation dose to the target while limiting dose to normal tissue when respiration causes tumor motion.  This project aims to improve both active and passive approaches to respiratory motion management.  An active approach is to use respiratory gating to synchronize imaging and delivery with respiration.  However, existing respiration monitoring devices are compromised when forced shallow breathing is employed or a thermoplastic body mask is used for immobilization.  In Aim 1 of this project a respiratory motion management process will be established based on a non-invasive temperature based respiration sensor.  In addition to compatibility in a radiotherapy and computed tomography simulation environment, the sensor will also be magnetic resonance compatible to be consistent with the future direction of radiation therapy.  It will be used with a biofeedback system to address the limitation of a temperature sensor only allowing for phase based gating.

A passive approach to respiratory motion management for radiotherapy is to reduce the time the radiation beam is on.  One way this is done is with the use of flattening filter free (FFF) beams which employ a high dose rate by removing the flattening filter from the path of the beam.  FFF beams are currently being used with dynamic conformal arc therapy (DCAT) and volumetric modulated arc therapy (VMAT), which use a multileaf collimator (MLC) to shape the radiation field.  However, the interplay effect of MLC leaf motion with tumor motion as well as accuracy when treating with off-axis geometry has not been investigated for FFF beams.  Aim 2 of this project will establish clinical implementation procedures when FFF beams are used with DCAT and VMAT.