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Jeanette Keil, MS, CMD, RT(R)(T) a, Joanne Carda, MS, CMD, RT(R)(T) b, Jade Reihart, MS, CMD, RT(T) c, Marjorie Seidel, CMD, RT(R)(T) a, Nishele Lenards, PhD, CMD, RT(R)(T), FAAMD d, Ashley Hunzeker, MS, CMD d
a Department of Radiation Oncology, MedStar RadAmerica, Baltimore, MD, 21237, USA
b Department of Radiation Oncology, Fairview Range Medical Center, Hibbing, MN, 55746, USA
c Department of Radiation Oncology, Advocate Lutheran General Hospital, Park Ridge, IL, 60068
d Medical Dosimetry Program, University of Wisconsin –La Crosse, La Crosse, WI 54601, USA
The aim of this retrospective study was to determine if the split x-jaw planning technique could be used with Varian linear accelerators to improve plan conformity and limit dose to organs at risk (OAR) for
planning target volumes that require ﬁeld sizes larger than the 15 cm extent of the multileaf collimator in the x-jaw position. Traditional planning techniques include limited and open x-jaw methods. The study population included 20 randomly selected patients with endometrial carcinoma. Treatment plans for each patient were designed using split, limited, and open x-jaw volumetric modulated arc radiotherapy for comparison purposes. Dose statistics including the PTV conformity index and dose to OAR were used to evaluate plan performance. The split x-jaw planning method had the most consistent conformity index (0.98 ± 0.02), followed by the open (01 ± 0.03), and the limited (1.04 ± 0.05) techniques. On average, the split method better spared the OAR. In comparison to the limited and open techniques, the split method reduced the dose to the bowel by 3.8%, rectum by 3.2%, sigmoid by 2.1%, right femoral head by 3.5%, and left femoral head by 3.9%. The split and open techniques showed comparable bladder results and were superior over the limited method. The monitor units were highest with the split method leading to increased treatment times. The split x-jaw planning technique should be used with Varian linear accelerators to produce superior volumetric modulated arc radiotherapy plans for planning target volumes larger than the maximum extent of the multileaf collimator in the x-jaw direction.