A study of different minimum segment area parameters on automatic IMRT plans for cervical cancer using Pinnacle3 9.10...

Based on Pinnacle39.10 treatment planning system (TPS) automatic planning module, we investigated the effect of minimum segmentation area (MSA) parameters on Auto-Plan Intensity Modulated Radiotherapy (AP-IMRT) without affecting the dose distribution of the target and the Organ at Risk (OAR). The results provided the basis for the ideal MSA parameters in the design of AP-IMRT plan. Ten patients with cervical cancer in our hospital were selected randomly for AP-IMRT design. Each patient was devised with 10 AP-IMRT plans. The prescription dose of PTV was 50 Gy/25 fractions. The radiotherapy plans of all patients were adopted with 7 field-averaged fixed fields. The MSA was set to 4 cm2, 9 cm2, 14 cm2, 20 cm2, 25 cm2, 40 cm2, 50 cm2, 60 cm2, 80 cm2, and 100 cm2. Plan quality and delivery efficiency were evaluated based on dose-volume histograms (DVHs), control points, monitor units (MUs), dosimetric measurement verification results, and plan delivery time. Except for the small difference in monitor units, the number of segmentations and target dose coverage, there were no statistically significant differences between the other dosimetric parameters in the planning target volumes. With the increase of MSA, the total number of MUs in AP-IMRT decreased from (649 ± 32) MUs to (312 ± 26) MUs, and the total number of segmentations decreased from (69 ± 1) to (28 ± 3). There was no statistical significance in the dose distribution of AP-IMRT target area with the MSA of 4-50 cm2 (P > .05). There was no significant difference in OAR dose between AP-IMRT plans with different MSA (P > .05). The calculated gamma indices using the 3% /3 mm and 2%/2 mm criteria. Both of the gamma pass rate and DTA pass rate all ≥95% under the condition of MSA are greater than 4 cm2, and the difference was no statistically significant (P > .05). The plan delivery times decreased with increasing MSA (P < .05). When using Pinnacle3 9.10 TPS to design AP-IMRT plan for cervical cancer, the parameter of MSA can be increased appropriately. Increasing the MSA allows for improved plan delivery accuracy and efficiency without significantly affecting the AP-IMRT plan quality. The MSA in the range of 14 to 50 cm2 can obtain a more reasonable dose distribution in the target area while the dose of target area and OAR had no significant changes. It is important to improve the plan quality, delivery accuracy, and efficiency for cervical AP-IMRT radiation therapy.