A Quantitative Assessment of Imaging Frequency on the Treatment Setup Accuracy in TomoTherapy

Bichay TJ, Davis S, Mayville AH and Bichay NDT

Mercy Health Saint Mary’s, The Lacks Cancer Center, Grand Rapids Michigan, USA
Wayne State University School of Medicine, USA
Department of Political Science, Michigan State University, USA

^*Correspondance to: Tewfik J. Bichay 

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Abstract:

Image guided radiation therapy (IGRT) is becoming the standard of practice for many treatment sites and techniques, especially those involving high dose gradients such as stereotactic radiosurgery (SRS), stereotactic radiotherapy (SBRT) and intensity modulated radiotherapy (IMRT). The purpose of this study is to quantify the setup accuracy for various IGRT frequency protocols from tattoo-only setups with no imaging, to imaging every fifth, fourth, third, second fraction, as well as daily imaging prior to TomoTherapy IMRT treatment. Total vector shifts were calculated from the lateral, longitudinal and vertical (x,y,z) displacements and the mean shift error for the various protocols analyzed for five treatment sites: cranial, head and neck, prostate, prostate bed and lung. On a given non-imaging day the shift relative to tattoos was determined by using the most recent imaged shift values and applying these to the current setup. Imaging data from 260 patients was analyzed for a total of 8,379 treatment sessions with displacement in the lateral, longitudinal and vertical directions. Lung patients and prostate patients had the largest vector shifts with a mean daily displacement of 10.4 mm. Prostate bed patients had an average vector shift of 9.0 mm, while head and neck and cranial patients had an average shift of 6.9 mm and 5.6 mm respectively. Increasing the imaging frequency increased the accuracy of the setup. Even if imaged every second day there is still an average error of 3.8 mm in the setup of cranial patients and 11.5 mm for lung patients ten percent of the time. Our data demonstrates that for TomoTherapy treatments, daily imaging is advisable for the five treatment sites presented in this study.

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Cite the Article:

Bichay TJ, Davis S, Mayville AH, Bichay NDT. A Quantitative Assessment of Imaging Frequency on the Treatment Setup Accuracy in TomoTherapy. Clin Oncol. 2016; 1: 1064.