การหาระยะขอบของปริมาตรเป้าหมายสำหรับวางแผนรังสีปรับความเข้มเชิงปริมาตรในโรคมะเร็งปากมดลูกที่ใช้แนวปฏิบัติให้ผู้ป่วยปัสสาวะก่อนฉายรังสี

Abstract

This study is a prospective study. Patient set-up error and daily Cone-Beam Computed Tomography (CBCT) images data of 10 cervix cancer patients who had indicated receiving whole pelvic radiotherapy. All patients were designed to receive whole pelvic irradiation with the dose of 46 Gy or a simultaneous integrated boost (SIB) of 55.2 Gy in 23 fractions planned by VMAT. The empty bladder protocol was designed for all patients before simulation and irradiation. The ‘all fraction’ set-up error in lateral (X), longitudinal (Y), and vertical (Z) axis from CBCT image registration were recorded and interpreted to be error margins by van Herk formula. The bladder volume variations of patients were evaluated. The results showed that from 215 CBCT image data sets, the set-up errors of cervical cancer patients were calculated. The systematic errors were 0.207, 0.255, and 0.301 cm. The random errors were 0.327, 0.298, and 0.318 cm. Calculated PTV margins were 0.746, 0.845, and 0.975 cm on the X, Y, and Z-axis, respectively. The distribution frequency of set-up error deviations within each range was analyzed separately for each cut-off range. At the 1.0 cm interval, the percentages of the error frequency beyond the boundary were 2.79, 2.33, and 2.33 in the X, Y, and Z-axis, respectively. The bladder volume assessment, the mean and standard deviation were 49.19 ±. 26.93 cc. The percentage change in bladder volume from the planning volume was +23.56. In all patients, none experienced a Grade 3 or greater side effect. This study suggested that the appropriate PTV margin in the empty bladder - cervical cancer patient is 1.0 cm for the Division of Radiation Oncology, Faculty of Medicine, Chiang Mai University. Due to it can cover daily patient positioning error at the calculated PTV margin of 0.975 cm at the vertical (Z) axis, which has the highest error. The frequency of the error data exceeding the margin is less than 3 percent on all axes. So, the empty bladder protocol is a method to reduce target placement error without causing serious side effects to the patient excretory system. This protocol can be used for people who have urinary incontinence problems. Choosing a pre-radiation practice guideline for patients should calculate a PTV margin that is appropriate for the lesion site and that guideline based on the information of each institution. To provide patients with the best treatment accuracy and quality of life.