Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway.
Br J Radiol. 2011 Jun;84(1002):566-9. doi: 10.1259/bjr/74571469.
The transition from analogue to digital radiography may have reduced the motivation to perform proper collimation, as digital techniques have made it possible to mask areas irradiated outside the area of diagnostic interest (ADI). We examined the hypothesis that collimation practices have deteriorated since digitalisation.
After defining the ADI, we compared the proportion of the irradiated field outside the ADI in 86 digital and 86 analogue frontal lumbar spine radiographs using the Mann-Whitney test. 50 digital images and 50 analogue images were from a Norwegian hospital and the remainder from a Danish hospital. Consecutive digital images were compared with analogue images (from the hospitals' archives) produced in the 4 years prior to digitalisation. Both hospitals' standard radiographic procedures remained unchanged during the study. For digital images, the irradiated field was assessed using non-masked raw-data images.
The proportion of the irradiated field outside the ADI was larger in digital than in analogue images (mean 61.7% vs 42.4%, p<0.001), and also in a subsample of 39 image pairs that could be matched for patient age (p<0.001). The mean total field size was 46% larger in digital than in analogue images (791 cm(2) vs 541 cm(2)).
Following the implementation of digital radiography, considerably larger areas were irradiated. This causes unnecessarily high radiation doses to patients.
从模拟到数字放射摄影的转变可能降低了正确准直的动力，因为数字技术使得可以掩盖在诊断感兴趣区域（ADI）之外的照射区域。我们检验了这样一个假设，即自从数字化以来，准直实践已经恶化。
在定义 ADI 后，我们使用曼-惠特尼检验比较了 86 张数字和 86 张模拟的腰椎前后位片的 ADI 外照射区域的比例。50 张数字图像和 50 张模拟图像来自挪威的一家医院，其余的来自丹麦的一家医院。连续的数字图像与数字化前 4 年的模拟图像（来自医院档案）进行了比较。在研究期间，两家医院的标准放射程序均保持不变。对于数字图像，使用未屏蔽的原始数据图像评估照射区域。
ADI 外的照射区域在数字图像中比在模拟图像中更大（平均值 61.7%比 42.4%，p<0.001），并且在可以匹配患者年龄的 39 对图像中也更大（p<0.001）。数字图像的总照射区域比模拟图像大 46%（791cm²比 541cm²）。
在实施数字放射摄影之后，照射区域大大增加。这会导致患者不必要地接受高剂量的辐射。
