Abstract
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.
Highlights
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
The primary purpose of the comparison is to investigate the characteristics of the FFF beams, where low-dose regions occur when moving from the center to the edges, and what the benefits of large and small target volume plans will be
The mean ± standard deviation and significance values of the data obtained from intensity-modulated RT (IMRT)-FF and IMRT-FFF plans for groups A and B are shown in Tables 2 and 3, respectively
Summary
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. The out-of-field dose was decreased because of reduced head leakage[6] Advanced treatment techniques such as stereotactic RT or intensity-modulated RT (IMRT) have increased interest in the operation of linear accelerators in FFF mode. The differences of the beams with non-uniform dose distribution were compared with the beams with uniform dose distribution as standard These differences were compared in the treatment plans of 20 lung patients with different target volumes (PTV). The patients were divided into two groups according to PTV volumes as A (PTV < 500 cc) and B group (PTV > 1000 cc) This comparison was based on statistical differences of monitor unit (MU) values, critical organ doses, and PTV evaluation criteria in treatment plans
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