From the Department of Radiology Technology, College of Applied Medical Sciences, Taibah University, Al Madinah Al Munawwarah, Kingdom of Saudi Arabia.
Saudi Med J. 2024 Mar;45(3):235-240. doi: 10.15537/smj.2024.45.3.20230520.
To assess the impact of changes in sinus aeration on dose variation in nasopharyngeal cases using a single beam with various field sizes and real patient computed tomography (CT) images.
The calculations were carried out on a computer equipped with an Intel Xeon (R) Gold 5118 processor operating at 2.30 GHz in 2022 at Taibah University, Al Madinah Al Munawwarah for a retrospective nasopharyngeal case. At the patient level, the impact on dose distribution was examined for different field sizes by comparing the percentage depth dose. The dose discrepancy was evaluated by comparing the dose delivered without considering the anatomical changes observed in the initial fraction to the dose adjusted to account for these changes using a 2D gamma analysis. With a criterion of 1% dose difference and 1 mm distance to agreement, the gamma level for analysis was set at 95%.
The study findings indicated that the observed effect diminished by approximately 50% for both 5 cm x 5 cm and 10 cm x 10 cm field sizes compared to the 3 cm x 3 cm size, where there was an overlap between the planning target volume and sinusitis.
The study concluded that the impact of dose discrepancy was more pronounced in smaller field sizes.
使用单束不同射野大小和真实患者 CT 图像，评估鼻窦通气变化对鼻咽病例剂量变化的影响。
2022 年，在塔伊巴大学（Al Madinah Al Munawwarah）的一台配备 Intel Xeon(R) Gold 5118 处理器（运行频率 2.30GHz）的计算机上对回顾性鼻咽病例进行计算。在患者水平上，通过比较百分深度剂量来检查不同射野大小对剂量分布的影响。通过比较不考虑初始分次中观察到的解剖变化而给予的剂量与根据这些变化进行调整的剂量，使用二维伽马分析评估剂量差异。伽马分析的伽马水平设定为 95%，标准为 1%剂量差异和 1mm 一致距离。
研究结果表明，与 3cm×3cm 大小相比，5cm×5cm 和 10cm×10cm 射野大小的观察到的影响分别减少了约 50%，在计划靶区和鼻窦炎之间存在重叠。
研究得出结论，剂量差异的影响在较小射野大小更为明显。
