Magill Dennise, Korman Sabina, Felice Marc, Mupparapu Mel
Quintessence Int. 2020;51(3):238-245. doi: 10.3290/j.qi.a43951.
Replacing conventional round intraoral collimators with rectangular collimators provides a considerable radiation dose reduction in adult patients. This study aimed to determine the radiation dose reduction via mathematical phantom when converting from round to appropriately sized rectangular collimation in children ages 5 to 15 years.
Virtual full mouth series (FMX) were simulated using a commercially available radiation dose software. This software is designed to calculate patient radiation doses from x-ray exams for various age pediatric and adult mathematical phantoms. For this pediatric study an 18-image FMX was simulated for the 15-year-old and a 12-image FMX was simulated for the 5-year-old and 10-year-old pediatric phantoms. An area of 12.0 to 16.8 cm2 represented rectangular collimation, while a 20.4 to 31.7 cm2 area represented typical round collimation.
Effective doses decreased in all ages by nearly 60% when switching from 31.7 cm2 round to 12.0 cm2 rectangular collimation. Reduction in absorbed doses to the thyroid (70% to 73%), salivary glands (62% to 78%), and active bone marrow (60% to 62%) were also noted when switching from the largest to smallest collimation.
This study suggests the use of rectangular collimators provides clinically relevant dose reduction for pediatric patients, even when altering from smaller round to rectangular collimation with equivalent beam quality, and this information can be utilized in all dental practices.
用矩形准直器取代传统的圆形口腔内准直器可使成年患者的辐射剂量大幅降低。本研究旨在确定5至15岁儿童从圆形准直转换为尺寸合适的矩形准直时，通过数学模型得出的辐射剂量降低情况。
使用市售的辐射剂量软件模拟虚拟全口系列（FMX）。该软件旨在计算各种年龄的儿科和成人数学模型在X射线检查时的患者辐射剂量。在这项儿科研究中，为15岁儿童模拟了18张图像的FMX，为5岁和10岁儿童模拟了12张图像的FMX。面积为12.0至16.8平方厘米代表矩形准直，而面积为20.4至31.7平方厘米代表典型的圆形准直。
当从31.7平方厘米的圆形准直转换为12.0平方厘米的矩形准直时，所有年龄段的有效剂量均降低了近60%。从最大准直转换为最小准直时，甲状腺（70%至73%）、唾液腺（62%至78%）和活跃骨髓（60%至62%）的吸收剂量也有所降低。
本研究表明，即使在光束质量相当的情况下从小圆形准直转换为矩形准直，使用矩形准直器也能为儿科患者提供临床相关的剂量降低，且该信息可应用于所有牙科诊所。
