Dosimetric impact of esophagus motion in single fraction spine stereotactic body radiotherapy.

Dosimetric impact of esophagus motion in single fraction spine stereotactic body radiotherapy. Phys Med Biol. 2019 Apr 24;: Authors: Wang X, Yang J, Zhao Z, Luo D, Court LE, Zhang Y, Weksberg D, Brown PD, Li J, Ghia AJ Abstract Nine patients with single fraction spinal stereotactic body radiation therapy (SBRT) treatment were identified to assess both the intra fraction and daily esophageal motion and associated dosimetric deviation in spinal SBRT. We performed a chained deformable registration of 4-D CT phase images to estimate the intra fraction motion magnitude of the esophagus in a breathing cycle. The intra fraction esophageal motion mostly exhibited in the superior-inferior direction with the total motion magnitude increased from the T1 (0.7 mm) to the T11 vertebra level (6.5 mm). The actual dose received by a moving esophagus was estimated by accumulating dose from each phase of the 4-D dataset using deformable image registration. In comparison, dose recalculated on the average CT reflects the dose received by a stationary esophagus. Intra fraction motion was found to reduce the maximum dose received by a small volume of esophagus ≤ 2 cm3, with the largest absolute and relative dose difference being -80 cGy and -6.4% respectively. Its effect on the maximum dose received by 5 cm3 of esophagus can be higher or lower with a large percentage difference, but did not result in substantial absolute dose increase to violate the dose...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research