Karssemeijer N, Frieling J T, Hendriks J H
University Hospital Nijmegen, Department of Diagnostic Radiology, The Netherlands.
Invest Radiol. 1993 May;28(5):413-9. doi: 10.1097/00004424-199305000-00005.
Digital acquisition systems currently available limit spatial resolution in digital mammography to roughly 0.1 mm/pixel. The objective of this study is to determine if high-quality mammography is possible at this resolution.
The influence of spatial resolution on diagnostic quality was investigated by comparing observer performance on film to that on digitized film. A 0.1-mm sampling distance was used for digitization. Detection of mammographic details was studied by measuring threshold contrast as a function of detail size for small circular objects in the range of 0.12 to 2.5 mm. Characterization of microcalcifications was investigated in a receiver operating characteristic (ROC) study, in which 10 radiologists read 72 mammographic details with microcalcifications, both digitally and on film.
Digitization improved the detectability of the larger, low contrast objects, whereas for small objects the detectability did not change. The authors found that even under the most optimal circumstances, isolated spherical calcifications with diameters smaller than 0.13 mm are not detectable with film-screen mammography, despite its resolution limit of 15 line patterns per mm (lp/mm). The ability to characterize microcalcification clusters did not change significantly with digitization. However, the results suggest that differentiation of benign from malignant cases decreases slightly, and that characterization of different types of malignancies somewhat improves by digitization. Mean differences between the two modalities were considerably smaller than the interobserver variability.
A relatively low spatial resolution of 0.1 mm/pixel does not prohibit high-quality diagnostic performance in digital mammography.
目前可用的数字采集系统将数字乳腺摄影的空间分辨率限制在大约0.1毫米/像素。本研究的目的是确定在此分辨率下是否能够进行高质量的乳腺摄影。
通过比较观察者在胶片和数字化胶片上的表现，研究空间分辨率对诊断质量的影响。数字化采用0.1毫米的采样距离。通过测量0.12至2.5毫米范围内小圆形物体的阈值对比度作为细节尺寸的函数，研究乳腺摄影细节的检测。在一项接受者操作特征（ROC）研究中，对微钙化进行特征分析，其中10名放射科医生对72个带有微钙化的乳腺摄影细节进行了数字化和胶片阅读。
数字化提高了较大的低对比度物体的可检测性，而对于小物体，可检测性没有变化。作者发现，即使在最理想的情况下，直径小于0.13毫米的孤立球形钙化在屏-片乳腺摄影中也无法检测到，尽管其分辨率限制为每毫米15线对（lp/mm）。数字化后，微钙化簇的特征分析能力没有显著变化。然而，结果表明，数字化后良性与恶性病例的区分略有下降，不同类型恶性肿瘤的特征分析有所改善。两种模式之间的平均差异远小于观察者间的变异性。
0.1毫米/像素的相对较低空间分辨率并不妨碍数字乳腺摄影的高质量诊断性能。
