Establishment of diagnostic reference levels for dentomaxillofacial radiography in Japan

本研究的目的是建立诊断参考水平（DRLs）在日本牙颌面x线摄影，以促进患者放射防护的优化和管理患者的剂量在常规x线检查。为了评价这些DRLs，我们研究了辐射量和辐射测量方法，然后调查了大学牙科医院和牙科诊所的辐射量和患者剂量。便携式剂量计与x射线胶片结合用于区域调查，电离室用于局部调查，由日本质量保证组织校准。将电离室与可移动放射剂量计进行了比较，可移动放射剂量计由用于口腔内放射照相的光刺激发光剂量计和用于全景放射照相的热释光剂量计阵列组成。根据调查结果，drl被确定为标准成人剂量分布的第三个四分之一，如下：(1)口内放射照相：患者入口剂量，PED=2.1 mGy，剂量面积积，DAP=59 mGy cm^2；但对于d速薄膜，需用两倍的PED或DAP，其DAP应由PED与矩形场面积的乘积计算；(2)全景放射照相：剂量宽度积，DWP=65 mGy mm， DAP=113 mGy cm^2；(3)头颅x线摄影：入口表面空气角，ESAK=0.4 mGy，但由于使用楔形滤光片和楔形辐射场，未提出DAP；(4)计算机断层扫描（CT）用于规划双颌种植牙手术：加权CT剂量指数CTDI_w=35 mGy，剂量长度积DLP=360 mGy cm，但每颌DLP各占一半。这些drl几乎与欧洲提出的drl相同，日本应该在牙科放射检查中保持足够的管电位，光束过滤和高灵敏度图像受体系统。

The objectives of this research were to establish diagnostic reference levels (DRLs) for dentomaxillofacial radiography in Japan in order to promote optimization of radiological protection for patients and to manage patient doses in routine X-ray examinations. For evaluation of these DRLs we studied the radiation quantities and methods of radiation measurement, and then surveyed the quantities and patient doses in university dental hospitals and in dental clinics.Transportable dosimeters coupled with X-ray films were used for the regional area survey and ionization chambers were used for the local area survey, which were calibrated by the Japanese Quality Assurance Organization. The ionization chambers were compared with the transportable dosimeters which were composed by an optically stimulate luminescence dosimeter for intraoral radiography and a thermoluminescent dosimeter array for panoramic radiography.From the results of the survey the DRLs were determined as a third quartile of the dose distributions for standard adults as follows : (1)intraoral radiography : patient entrance dose, PED=2.1 mGy and dose-area product, DAP=59 mGy cm^2 ; but a double of PED or DAP for D-speed films and the DAP should be calculated from the product of PED by the area of a rectangular field ; (2)panoramic radiography : dose-width product, DWP=65 mGy mm and DAP=113 mGy cm^2 ; (3)cephalometric radiography : entrance surface air kerma, ESAK=0.4 mGy, but DAP was not proposed because of the usage of wedge filters and radiation fields of wedge shapes ; (4)computed tomography (CT) for planning of dental implantation surgery of both jaws : weighted CT dose index, CTDI_w=35 mGy and dose-length product, DLP=360 mGy cm, but a half of DLP for each jaw.These DRLs, which are almost the same as those proposed in Europe, should be achieved in Japan to maintain adequate tube potentials, beam filtrations, and high sensitivity image receptor systems in dental radiographic examinations.