Thornley Peter H, Stewardson Dominic A, Rout P G John, Burke F J Trevor
Prim Dent Care. 2004 Jul;11(3):81-6. doi: 10.1308/1355761041208539.
Rectangular collimation is recommended in order to reduce radiation doses to patients. However, anecdotal reports suggest that it may result in more retakes, with a possible net increase in patient dosage.
To test this hypothesis, eight general dental practitioners were recruited to participate in a project. Each took 25 pairs of bitewing radiographs of patients before and 25 after fitting rectangular collimators to their x-ray machines. Double-pack films were used so that duplicates could be examined. These were assessed by a consultant oral radiologist according to the National Radiographic Protection Board (NRPB) grading system for positioning and general film quality.
Initially, positioning quality was above the target level for six of the eight dentists; however, for all but one, this dropped after using rectangular collimation. General film quality was of a lower overall standard initially. Using rectangular collimation had an effect on general film quality but the direction and size of this varied among the dentists.
It was concluded that amongst the participating dentists, although numbers of retakes increased by 7%, there would be a net reduction in dosage to patients following rectangular collimation.
为降低患者的辐射剂量，建议采用矩形准直。然而，有传闻称这可能会导致更多的重拍，从而可能使患者的总剂量净增加。
为验证这一假设，招募了八位普通牙科医生参与一个项目。每位医生在其X光机安装矩形准直器之前和之后，分别为患者拍摄25对咬合翼片。使用双层包装胶片以便能检查复制品。由一位口腔放射学顾问根据国家放射防护委员会（NRPB）的定位和胶片总体质量分级系统对这些胶片进行评估。
最初，八位牙医中有六位的定位质量高于目标水平；然而，除一位牙医外，其他所有牙医在使用矩形准直后，定位质量均有所下降。总体胶片质量最初的整体标准较低。使用矩形准直对总体胶片质量有影响，但不同牙医的影响方向和程度各不相同。
得出的结论是，在参与项目的牙医中，尽管重拍次数增加了7%，但采用矩形准直后患者的剂量将净减少。
