required number of CT to cover interfractional stomach movement during radiotherapy of MALT lymphoma
PO-1173
Abstract
required number of CT to cover interfractional stomach movement during radiotherapy of MALT lymphoma
Authors: Tatsuya Toyoda1, Atsuro Terahara2
1NTT Medical Center Tokyo, Radiology, Tokyo, Japan; 2Toho University Omori Medical Center, Radiology, Tokyo, Japan
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Purpose or Objective
Stomach moves day by day, so several number of CT may be necessary to cover stomach movement during radiotherapy of MALT lymphoma. We evaluated necessary number of CT to cover stomach movement with conventional CT and 4DCT.
Material and Methods
We contoured stomach of MALT lymphoma patients on 1st CT (1stCTV) and add the contour of stomach on 2nd CT of another day to 1stCTV. We continued this process until new contour of stomach is included in the total sum of stomach contours (totalCTV). Twelve patients were with conventional CT from Jan. 2012 to Feb. 2017, and five patients were with 4DCT from May 2018 to March 2020.
Results
Necessary number of conventional CT and 4DCT to cover whole range of stomach movement was 4 to 9 (mean 6.5, median 6), 4 to 9 (mean 5.8, median 5.5) respectively. Percentage of 1stCTV/totalCTV was 35.4 to 73.6 (mean 57.0) (conventional CT), 57.8 to 88.6 (mean 69.0) (4DCT). Mean coverage percentage of until 1stCT/2ndCT/3rdCT/4thCT/5thCT/6thCT/7thCT/8thCT/9thCT was 57.0/73.7/84.0/90.8/94.9/97.2/98.7/100/100 (conventional CT), 69.0/83.1/88.4/95.9/97.5/99.0/99.1/99.5/100 (4DCT).
Conclusion
Necessary number of CT to cover mean 95% of whole range of stomach movement in MALT lymphoma radiotherapy was at least five with conventional CT and four with 4DCT. Mean stomach coverage with 1st CT was 57.0% (conventional CT) and 69.0% (4DCT) and was not considered to be sufficient.