Abstract ID: 17217 Title: Respiratory motion mitigation during radiation treatment delivery
This presentation reviews methods to manage respiratory motion during radiation delivery.
Technological advances have made available new capabilities for measuring and reducing
respiratory motion. Optical and spirometry devices, external to the patient, provide monitoring of
patient voluntary motion and respiration. Radiographic detection of implanted fiducial markers
has enabled internal motion monitoring at treatment.
Methods that are currently used clinically or under investigation to actively mitigate respiratory
motion include abdominal compression, breath hold, respiratory gating, breathing-synchronized
treatment, and real-time motion tracking. Abdominal compression is the most commonly used
technique with stereotactic body radiotherapy to reduce target respiratory motion. The organ
deformations induced by the compression and residual target motion generally will vary with
each patient setup, thus requiring image-based evaluation and adjustment. Most widely used
gating and breath-hold systems infer tumor position from respiration monitors external to the
patient. A large source of uncertainty stems from changes in the positional relationship between
tumor and external signal, both between and within treatment fractions, thus requiring at least
daily image guidance and recalibration. Real-time motion tracking, involving image-guided
treatment delivery with automated motion correction, is challenging owing to temporal variations
in breathing patterns. One such clinical system is based on a motion model that correlates realtime external motion monitors with periodic x-ray images of implanted fiducial markers. The
accuracy of motion corrections depend on the x-ray imaging system, tracking algorithm, and
motion correlation model. Accuracy of implanted markers depends on their proximity and
motion relative to the tumor.
Learning Objectives:
1) Understand various radiation delivery practices to mitigate respiratory motion.
2) Understand the limitations, current expectations, and possible further improvements of
motion mitigation systems