Medical Imaging Group, Centre for Vision, Speech, and Signal Processing, University of Surrey, Guildford, GU2 7XH, United Kingdom. National Co-ordinating Centre for the Physics of Mammography (NCCPM), Royal Surrey County Hospital, Guildford GU2 7XX, United Kingdom.
Phys Med Biol. 2018 May 4;63(9):095014. doi: 10.1088/1361-6560/aabd53.
This work investigates the detection performance of specialist and non-specialist observers for different targets in 2D-mammography and digital breast tomosynthesis (DBT) using the OPTIMAM virtual clinical trials (VCT) Toolbox and a 4-alternative forced choice (4AFC) assessment paradigm. Using 2D-mammography and DBT images of virtual breast phantoms, we compare the detection limits of simple uniform spherical targets and irregular solid masses. Target diameters of 4 mm and 6 mm have been chosen to represent target sizes close to the minimum detectable size found in breast screening, across a range of controlled contrast levels. The images were viewed by a set of specialist observers (five medical physicists and six experienced clinical readers) and five non-specialists. Combined results from both observer groups indicate that DBT has a significantly lower detectable threshold contrast than 2D-mammography for small masses (4 mm: 2.1% [DBT] versus 6.9% [2D]; 6 mm: 0.7% [DBT] versus 3.9% [2D]) and spheres (4 mm: 2.9% [DBT] versus 5.3% [2D]; 6 mm: 0.3% [DBT] versus 2.2% [2D]) (p < 0.0001). Both observer groups found spheres significantly easier to detect than irregular solid masses for both sizes and modalities (p < 0.0001) (except 4 mm DBT). The detection performances of specialist and non-specialist observers were generally found to be comparable, where each group marginally outperformed the other in particular detection tasks. Within the specialist group, the clinical readers performed better than the medical physicists with irregular masses (p < 0.0001). The results indicate that using spherical targets in such studies may produce over-optimistic detection thresholds compared to more complex masses, and that the superiority of DBT for detecting masses over 2D-mammography has been quantified. The results also suggest specialist observers may be supplemented by non-specialist observers (with training) in some types of 4AFC studies.
本研究使用 OPTIMAM 虚拟临床试验（VCT）工具箱和四择一强迫选择（4AFC）评估范式，调查了在二维乳房 X 线摄影和数字乳腺断层合成术（DBT）中，专家和非专家观察者对不同目标的检测性能。通过对虚拟乳房体模的二维乳房 X 线摄影和 DBT 图像进行分析，我们比较了简单均匀球形目标和不规则实体肿块的检测极限。选择直径为 4mm 和 6mm 的目标，代表在各种控制对比度水平下接近乳腺筛查中最小可检测大小的目标大小。一组专家观察者（五名医学物理学家和六名经验丰富的临床读者）和五名非专家观察者对图像进行了观察。来自两组观察者的综合结果表明，对于小肿块（4mm：2.1%[DBT] 与 6.9%[2D]；6mm：0.7%[DBT] 与 3.9%[2D]）和球体（4mm：2.9%[DBT] 与 5.3%[2D]；6mm：0.3%[DBT] 与 2.2%[2D]），DBT 的检测阈值对比度明显低于 2D 乳房 X 线摄影（p<0.0001）。两个观察组都发现，对于两种大小和两种模式的球体，都比不规则实体肿块更容易被检测到（p<0.0001）（4mm DBT 除外）。一般来说，专家和非专家观察者的检测性能被发现是相当的，每个组在特定的检测任务中都略优于另一个组。在专家组中，临床读者对不规则肿块的检测性能优于医学物理学家（p<0.0001）。结果表明，与更复杂的肿块相比，在这种研究中使用球形目标可能会产生过于乐观的检测阈值，并且已经量化了 DBT 在检测肿块方面相对于二维乳房 X 线摄影的优势。结果还表明，在某些类型的 4AFC 研究中，可以由经过培训的非专家观察者来补充专家观察者。
