# Impact of Patient Size and Positioning on Radiation Dose in Multiphase Liver CT Examinations
## 4 Discussion  
Radiation dose management is crucial in medical diagnostics to balance obtaining the necessary diagnostic information with minimizing the patient's exposure to radiation [16]. This study focused on analyzing the relationship between patient characteristics, radiation dose, and imaging parameters. The results show a significant positive correlation between the patient's maximum dimensions and BMI and total DLP for abdominal examinations. This correlation includes both the abdominal and pelvic abdominal examination groups. In addition, a moderately positive association was identified between patient width and DLP in the delayed phase for the liver. The above results underscore the impact of patient size on radiation dose, highlighting the need for tailored dose optimization strategies based on individual patient characteristics, which may include, for example, reducing the scope of the examination only to clinically relevant areas. It is noteworthy that a greater correlation was noted between patient BMI and total DLP than maximum patient width. Further analysis examined the relationship between patient dimensions and X-ray tube output parameters. However, in studies involving only the abdominal cavity, the relationship with X-ray tube power parameters (mA at different phases) was weak, suggesting that the effect of patient size on radiation dose has limited impact on specific X-ray tube performance parameters. In contrast, in studies involving the abdomen and pelvis, weight and BMI showed a greater effect on X-ray tube mA settings in the three phases of the study. In particular, the correlation between BMI and mA settings in the third phase (delay to the liver at 3 min after contrast administration) was statistically significant. The study also examined the effect of isocenter location on radiation dose and X-ray tube performance. Interestingly, the presence or absence of an isocenter showed no statistically significant effect on radiation dose or X-ray tube performance in either the abdominal-only or abdominal-pelvis groups. This suggests that isocenter location may not be a significant factor affecting these parameters in the study group. In contrast, for patients placed in the isocenter, the dose spread was significantly smaller, and the doses were more similar to each other. [PERSON] et al. conducted a study to evaluate the effect of patient positioning in the isocenter on radiation dose using two routine head scanning protocols: standard (120 kVp/180 mAs) and low dose (100 kVp/142 mAs). A standard cylindrical phantom made of polymethylmethacrylate (PMMA), placed at a height of 104 cm from the floor (reference isocenter), was used to measure dose. The positions of the phantom were then changed to simulate an alignment of 5 cm relative to the isocenter, in both the upward and downward directions, at heights of 109 cm, 114 cm, 119 cm, 124 cm, and 99 cm, 94 cm, 89 cm, 84 cm, respectively. The results of the effective dose measurements were as follows: the highest mean volume of the Computed Tomography Dose Index (CTDIvol) for Maximum Change in a Step (MCS) (upward change) was 105.06 mGy (at +10 cm), and for Minimum Change in a Step (MCI) (downward change) was 105.51 mGy (at \(-10\) cm), which was significantly different (\(p<0.05\)) compared to the isocenter. Significant differences (\(p<0.05\)) were observed in the mean DLP value between the isocenter and MCS (85.8 mGy.cm) and MCI (93.1 mGy.cm). The introduction of the low-dose protocol resulted in significantly increased CTDIvol values for MCS (at +10 cm) and MCI (at \(-10\) cm) compared to the isocenter [17]. In the study by [PERSON] et al. the authors focused on evaluating radiation dose in the context of CT-guided biopsies. Focused on abdominal examinations, our study analyzed a wide range of imaging studies, taking into account different procedures and body areas.