Aim: To quantify the organ motion and set up errors in carcinoma cervix patients to individualized PTV margins.
Material and methods: Seven Carcinoma cervix patients who opted for treatment with Image Guided Radiotherapy were taken for quantification of interfraction set up errors and organ motion. 10 pre treatment Cone beams Computed Tomographic (CBCT) scans were evaluated per patient. Values for inter-fraction set up errors were registered for three principal axes in left-right (X-axis), supero-inferior (Y-axis) and antero posterior (Z-axis). Mid-rectum motion was evaluated in anterior, posterior, right and left directions. Antero-posterior (AP) and transverse diameter of mid-rectum in CBCT was compared with Planning CT scan (PCT). Interfraction bladder motion was assessed by comparing bladder volume and translation of the bladder wall in three dimensions in CBCT scans to the baseline PCT.
Results: Mean bone shifts noted were 0.32±0.24cm, 0.29±0.21cm and 0.13±0.12cm along X, Y and Z axis respectively. Mean mid-rectum movement was maximum in anterior direction. Mean PCT AP and transverse diameter of rectum were 2.49±0.72cm and 3.01±0.54cm and CBCT AP and transverse diameter were 2.61±0.83 cm and 3.10±0.42cm respectively. Maximum movements were seen along anterior followed by superior bladder wall and minimum movements were seen along right bladder wall. Mean PCT and CBCT (±standard deviation) bladder volume noted was 177.93±80.51cc and 183.33±25.14cc respectively.
Conclusion: Set up errors and organ motions were within our prescribed PTV margins. Close patient follow-up during treatment is mandatory to assess patients’ dietary, bowel and bladder habits and weight loss.
IGRT, CERVIX, cone beam CT, set-up errors, organ motion, target volume, mortality, technical issues, patient outcome, patient selection, carcinoma cervix, daily set up, ischial tuberosity, cranio-caudal direction, posterior (z) axes