Näppi Janne, Yoshida Hiroyuki
Massachusetts General Hospital and Harvard Medical School, 25 New Chardon Street, Suite 400C, Boston, Massachusetts 02114, USA.
Med Phys. 2009 May;36(5):1830-8. doi: 10.1118/1.3113893.
Laxative-free computed tomographic colonography (lfCTC) could significantly improve patient adherence to colorectal screening. However, the interpretation of lfCTC data is complicated by the presence of poorly tagged feces and partial-volume artifacts that imitate colorectal lesions. The authors developed a method for virtual tagging of such artifacts. A probabilistic model of colonic wall was developed, and virtual tagging was performed on artifacts that were identified by the model. The method was evaluated with 46 clinical lfCTC cases that were prepared with dietary fecal tagging only. Visual examples show that the method can label partial-volume artifacts, poorly tagged feces, nonadhering completely untagged feces, and artifacts such as rectal tubes. The effect of virtual tagging was evaluated by comparing the detection accuracy of a fully automated polyp detection scheme without and with the method. With virtual tagging, the per-lesion detection sensitivity was 100% for lesions > or = 10 mm (n = 4) with 3.8 false positives per patient (per two CT scan volumes) and 90% for lesions > or = 6 mm (n = 10) with 5.4 false positives per patient on average. The improvement in detection performance by virtual tagging was statistically significant (p = 0.03; JAFROC and JAFROC-1).
无泻药计算机断层结肠成像（lfCTC）可显著提高患者对结直肠癌筛查的依从性。然而，由于存在标记不佳的粪便和模仿结直肠病变的部分容积伪影，lfCTC数据的解读变得复杂。作者开发了一种对此类伪影进行虚拟标记的方法。建立了结肠壁的概率模型，并对该模型识别出的伪影进行虚拟标记。该方法在仅采用饮食粪便标记准备的46例临床lfCTC病例中进行了评估。视觉示例表明，该方法可以标记部分容积伪影、标记不佳的粪便、完全未附着的未标记粪便以及直肠管等伪影。通过比较有无该方法的全自动息肉检测方案的检测准确性来评估虚拟标记的效果。采用虚拟标记时，对于直径≥10 mm的病变（n = 4），每病变检测敏感性为100%，平均每位患者（每两个CT扫描容积）有3.8例假阳性；对于直径≥6 mm的病变（n = 10），检测敏感性为90%，平均每位患者有5.4例假阳性。虚拟标记对检测性能的改善具有统计学意义（p = 0.03；JAFROC和JAFROC - 1）。
