## 3 Results
### Individual Anatomical Characteristics of the Patient  
After reviewing the existing literature, [PERSON] et al. indicated that in order to minimize the radiation dose to the heart, the maximum heart distance (MHD) should be as far away from the treatment area as possible, while larger ciliary contact distances (CCD ps) and axial contact distances (CCD ax) to the heart are associated with increased radiation dose to the heart [4]. A literature review of a retrospective dosimetry study by [PERSON] et al. confirmed the relevance of measuring cardiac contact distance and showed correlations between a greater difference in inspiratory volume and an increase in cardiac protection during DIBH [21]. The study by [PERSON] et al. only demonstrates the relevance of larger CCD ps and lateral heart-to-chest distance (HCD) measured during CT scans with patients breathing freely. Moreover, one unit increase in the ratio of the two measurements relative to each other results in a reduction in cardiac dose in the range of 0.93-1.15 Gy [30]. The reduction in the irradiation of organs at risk is influenced by breast size [31]. [PERSON] et al. conducted the most extensive retrospective study to date, in which 27% of prospective subjects with stage (T1/T2, N0/M1 mic, M0) left-breast cancer underwent breast-sparing surgery and received DIBH radiation therapy (40.05 Gy, 15 doses). Using Kendall's tau-B probability difference, the researchers showed that an increase in patients' breast size [clinical radiation area expressed cm\({}^{3}\) (CTV)] was associated with a decrease in planned radiation volume (PTV) for critical organs (heart, L and P lung, left anterior interventricular branch of the left coronary artery-LAD and P breast) in radiological procedures. Moreover, in contrast to intensity-modulated proton therapy (IMPT), researchers have shown a positive correlation between CTV and mean right lung dose in intensity-modulated hybrid radiotherapy (h-IMRT) [31]. In a meta-analysis, [PERSON] et al. described similar findings indicating an increase in radiation in a critical organ, such as the heart, depending on the breast size of the patient [\(<\)750 cm\({}^{3}\)--(0.4-2.1 Gy), 750-1500 cm\({}^{3}\)--(0-1.4 Gy), \(>\)1500 cm\({}^{3}\)--(0-0.8 Gy)] [17]. A study by [PERSON] et al. showed no difference in MHD dependent on breathing technique (DIBH and FB) while the use of the DIBH technique in a group of patients with large breasts (\(>\)2028.92 cm\({}^{3}\)) showed significantly lower average doses [10].  
Studies show that patients' anatomical differences have a significant impact on minimizing the radiation dose delivered to the heart during a radiotherapy session [4; 7; 10; 17; 21; 30; 31]. When selecting patients, it is important to determine MHD, CCD ps, CCD ax, HCD, sag ging, and breast size. The values of these parameters affect dose reductions for OAR. Measurement of the aforementioned values in free-breathing patients is a key predictor considered in patients qualified for DIBH. Other anatomical aspects can also affect radiation doses reaching the heart. For instance, a sagging breast can lower the lower limit of the contact area, resulting in a potential increase in radiation dose to the heart.