[A method of computerized evaluation of CT based treatment plants in external radiotherapy]

Selection of an optimal treatment plan requires the comparison of dose distributions and dose-volume histograms (DVH) of all plan variants calculated for the patient. Each treatment plan consists generally of 30 to 40 CT slices, making the comparison difficult and time consuming. The present study proposes an objective index that takes into account both physical and biological criteria for the evaluation of the dose distribution. The DHV-based evaluation index can be calculated according to the following four criteria: ICRU conformity (review of the differences between the dose in the planning target volume and the ICRU recommendations); mean dose and dose homogeneity of the planning target volume; the product of tumour complication probability (TCP) and normal tissue complication probability (NTCP); and finally a criterion that takes into account the dose load of non-segmented tissue portions within the CT slice. The application of the objective index is demonstrated for two different clinical cases (esophagus and breast carcinoma). During the evaluation period, the objective index showed a good correlation between the doctor's decision and the proposed objective index. Thus, the objective index is suitable for a computer-based evaluation of treatment plans.