The effect of electron density table accuracy on radiotherapy dose calculations

In this study, the data of 15 patients with lung cancer who underwent RT in the Radiation Oncology Clinic of Ankara City Hospital were analyzed retrospectively and dosimetrically. Lung cancer was preferred because it is the region where the electron density difference is the highest. Two different EDT data were used for these patients. The first one is the correct EDT data obtained from the hospital's data set from the GE Discovery device. The second one is the wrong EDT data belonging to the Toshiba Aquillion device from another hospital. The EDTs of the two tomographs were uploaded to the system without making any changes in the plan parameter and iteration information. Using these data, treatment plans were made with the helical intensity-modulated radiotherapy (Hel-IMRT) technique in the Tomotherapy Accuray Radixact treatment planning system (TPS). Two plans, using the correct EDT and the wrong EDT, were obtained for each patient. In the plan verification section (QA=Quality Confidence); QA phantoms were obtained from planning CT images. The dosimetric data of the two calculations were uploaded to the SPSS program and it was evaluated whether there was a between the calculated doses. In the comparison of two plans in terms of the target volume, D95 (p=0.001), CI (p=0.002), HI (p=0.045) and GI (p=0.001) calculations using correct EDT than wrong EDT. There was no significant difference between the measurements made with the two EDTs in terms of the hot point (p=0.842). Maximum spinal cord dose was lower in the calculation made with correct EDT than wrong EDT (p=0.015). Additionally, Esophageal maximum (p=0.001), esophagus mean (p=0.003), mean heart (p=0.011), Lung mean(p=0.001), Lung V5(p=0.001 and Lung V20 (p=0.001) were significantly higher in calculations using correct EDT than wrong EDT. As a result, EDT causes statistically significant differences in dose analysis, and this change leads to changes in critical organ doses. The use of inappropriate EDT values causes statistically significant errors