Evaluation on dose distribution of longitudinal profile on helical tomotherapy Gha-Jung Kim Kim Gha-jung* Professor, Department of Radiological Science, Far East University, Eumseong-gun, Chungbuk, Korea *Corresponding author: Gha-jung Kim Professor, Department of Radiological Science, Far East University, Eumseong-gun, Chungbuk, Korea Email: gjms1225@hanmail.net
Online published on 16 October, 2018. Abstract In this study is aimed to evaluate the accuracy of longitudinal dose distribution during helical tomotherapy slice treatment using ion chamber and EBT film, and measure the flatness in the longitudinal profile for each radiation field width. As the experiment condition, the radiation field widths were set to 10 mm, 25 mm, and 50 mm, respectively, to acquire and evaluate a longitudinal beam profile. A slab phantom and A1SL ion chamber was used to evaluate the accuracy of longitudinal dose distribution in helical tomotherapy. Also, solid phantom and EBT film was used to measurement of dose flatness in the longitudinal axis (Y axis). The difference between reference and measured data values of FWHM at the radiation field width of 10 mm was 0.546 ± 0.186% on average, and the maximum γ-index was 0.522 ± 0.056. The difference between reference and measured data values of FWHM at the radiation field width of 25 mm was 0.133 ± 0.113% on average, and the maximum γ-index was 0.417 ± 0.102. The difference between reference and measured data values of FWHM at the radiation field width of 50 mm was 0.120 ± 0.072% on average, and the maximum γ-index was 0.467 ± 0.077. The dose flatness within a range of 250 mm longitudinal axis (Y axis) for each radiation field width was 1.71 ± 0.46% on average, which was a value within 3%. The results exhibited that the dose flatness became more even as the radiation field width became wider. The above study results will contribute to clarifying the accuracy of radiation dose delivered to real patients, or the DQA, which is an important QA item in the IMRT using tomotherapy. Top Keywords Tomotherapy, Full Width at Half Maximum (FWHM), Delivery Quality Assurance(DQA), longitudinal dose distribution, γ-index. Top |