Analysis and application of IMRT plan based on 3D printing individualized phantom

Objective The dosimetry parameters in the radiotherapy plan of the patient image and the phantom image were compared, and the radiotherapy dose distribution in 3D printing individualized phantom under the treatment planning system (TPS) and accelerator was analyzed.

Methods CT localization images in digital imaging and communications in medicine (DICOM) format were selected from a patient (female, 78 years old) with esophageal cancer who were treated at the Xuzhou Cancer Hospital in October 2023. On the experimental basis of the 3D printing individualized phantom, the radiotherapy plans of the patient and phantom were designed, and the dosimetry parameters of the target volume and the organ at risk were compared. The ionization chamber was inserted into the target volume (high density area) and the reference point (low density area) respectively before the phantom was exposed to radiation under the accelerator. The errors between the calculated from TPS and measured values in the target volume and the reference point were analyzed.

Results In the dose volume histogram (DVH) of the radiotherapy plan of the patient image and the phantom image, the curves of the target volume and the organ at risk basically coincide. The average dose of the target volume was higher in the phantom group than in the patient group. The average dose of reference point was lower in the phantom group than in the patient group and the difference was significant. The calculated and measured values of the target volume are 210.4 cGy and 211.0±0.6 cGy respectively, the percentage dose deviation is 0.3%. The calculated and measured values of the reference point are 49.1 cGy and 49.4±0.6 cGy respectively, the percentage dose deviation is 0.68%. The dose deviation of the two places is within 3%, which meets the requirements of the "Specification for testing of quality control in medical linear accelerato".

Conclusions The combination of chamber detector and 3D printing individualized phantom can be used to verify the intensity modulated radiotherapy plan, and the experimental results provide a foundation and reference for the study of the energy deposition distribution between different tissues and the research on the quality assurance of radiotherapy.