Dosimetric evaluation of left ventricle and left anterior descending artery in left breast radiotherapy.

INTRODUCTION: We evaluated the dosimetric results of the identification of the left ventricle (LV) and left anterior descending artery (LAD) as organs at risk (OARs) in adjuvant radiotherapy (RT) after breast-conserving surgery (BCS). MATERIALS AND METHODS: Twenty-two patients who had previously received RT in our center were evaluated retrospectively. All patients had undergone BCS operation for left breast cancer. LV and LAD were contoured as OARs on the same simulation CTs for these patients whose treatment was previously completed in which LV and LAD were not defined as OARs. Complying with the initial plans, intensity-modulated RT plans with 7-9 fields were made on the computer. Planning target volume (PTV), homogeneity index (HI), conformity index (CI), monitor unit (MU) values, and doses of OARs were compared using the Wilcoxon signed-rank test (p < 0.05). RESULTS: There were no significant differences in PTV 50 (D 50% and D 98%), PTV 60 (D 2% and D 50%), HI, CI, and MU values when treatment plans and control plans were compared (p > 0.05). While it was possible to protect the heart, LAD, and LV better, LAD and LV were not contoured in the treatment plans, and they received higher doses compared to the control plans (p < 0.05). There was no significant difference in the other OARs. CONCLUSION: In conclusion, it is essential to define the lower anatomical regions of the heart as OARs. Otherwise, the doses taken by these regions are ignored and may be maintained less than possible. In our study, it was shown that LV and LAD doses were significantly reduced even in the same center and planning by the same team.

Comparison of radiotherapy techniques with flattening filter and flattening filter-free in lung radiotherapy according to the treatment volume size.

In external radiotherapy (RT), the use of flattening filter-free (FFF) radiation beams obtained by removing the flattening filter (FF) in standard linear accelerators is rapidly increasing, and the benefits of clinical use are the issue of research. Advanced treatment techniques have increased the interest in the operation of linear accelerators in FFF mode. The differences of the beams with non-uniform dose distribution created by removing FF compared to the beams with uniform dose distribution used as a standard were examined. These differences were compared in the treatment plans of lung patients who have different planning target volumes (PTV). Clinac IX linear accelerator units were used. Twenty patients with previously completed treatment were divided into two groups depending on the size of the target volume. All patients underwent two different intensity-modulated RT (IMRT) plans using FF and FFF beams. The Wilcoxon Signed-Rank test was used to compare two different techniques (Significance p < 0.05). There was no statistically significant difference between the two techniques when looking at the D2%(Gy), D98%(Gy), D50%(Gy), homogeneity (HI), and conformity index (CI) data for both groups. When the critical organ doses were evaluated, there was a statistically significant difference only in the V20(%) values of the lungs, but these differences were not very large. Monitor unit (MU) data were found to be lower in FF planning, and treatment time was lower in FFF planning. Except for shorter treatment times, and of the lungs V20(%) value, in standard fractionated RT of lung cancer, there was no significant difference between the use of FFF and FF techniques for large and small target volumes.