Developing Virtual Colonoscopy for Cancer Screening

描述(申请人提供)：结直肠癌是美国第三种最常见的癌症，也是第二大癌症死亡原因。通常在患者出现症状后的晚期被诊断出来，这解释了它的高死亡率。由于大多数结肠癌是在5到15年的恶变期内由息肉引起的，因此一直提倡筛查小息肉。不幸的是，大多数人没有遵循这一建议。该项目与健康相关的是，通过开发一种方便、几乎无风险的检测细小息肉的方法，大幅增加愿意参与筛查计划的人数。CT结肠成像(CTC)或基于CT的虚拟结肠镜(VC)显示出与黄金标准光学结肠镜(OC)相当的性能，可以以更小的侵入性方式检测8 mm以上的息肉。为了成为一种筛查工具，目前的CTC必须被更多的人群接受，对较小的息肉具有更高的检测能力。最近联邦医疗保险拒绝接受CTC，这证明了这些需求，例如减少CT辐射、检测较小的息肉、缓解肠道准备(BP)压力、最大限度地减少阅读器变化、提高效率等。我们在朝着该项目广泛的长期目标发展的技术进步方面取得了良好进展，即将CTC发展为一种安全、准确、成本效益、微创、压力最小的筛查方式。为了推动CTC朝着长期目标发展，本次项目更新的具体目标是：(1)开发和评估一种自适应统计重建算法，以在尽可能低的mAs水平获得当前腹部CT图像质量，从而将X射线暴露的风险降至最低。该算法不仅考虑了X射线量子统计和能谱，而且还考虑了系统背景噪声，因为这种噪声在低mAs水平下起到了明显的作用。(2)开发和评估一种改进电子结肠清洗(ECC)的部分体积(PV)统计分割算法，并对其进行改进。这一改进将导致检测到更小的息肉，CT辐射减少一半，并通过接近无泻剂的CTC来缓解患者对BP的压力。(3)开发和评估一种ECC自适应的、基于纹理的特征提取算法，以改进计算机辅助息肉检测(CADPolyp)，从而提高CTC的成本效益。人们希望，随着对较小息肉的更高检测能力的改善，以及更容易被大量人群接受(通过更少的辐射和压力)，CTC将推动CTC朝着医疗保险覆盖范围内接受的筛查模式发展。低mAs的统计重建对其他CT应用也有一定的参考价值。对于其他虚拟内窥镜的应用，如在虚拟血管造影中提取用于斑块分析的血管壁和在虚拟膀胱造影术中用于早期检测生长的膀胱壁，这种基于不均一性校正的PV图像分割将是有益的。 与公共卫生相关：这项建议旨在开发计算机断层扫描(CTC)或基于CT的虚拟结肠镜(VC)，通过使用(1)尽可能低的低剂量CT扫描，(2)压力较小的肠道准备(BP)，例如最小的泻药和/或不含泻剂的BP，以及(3)计算机辅助检测(CAD)和三维(3D)内窥镜相结合的息肉检测方法，来开发一种筛查模式。

DESCRIPTION (provided by applicant): Colorectal carcinoma is the third most commonly diagnosed cancer and the second leading cause of death from cancer in the United States. Often it is diagnosed at an advanced stage, after the patient has developed symptoms, explaining its high mortality rate. Since most colon cancers arise from polyps over a 5 to 15 year period of malignant transformation, screening programs to detect small polyps have been advocated. Unfortunately most people do not follow this recommendation. The health relatedness of this project is to dramatically increase the number of people willing to participate in screening programs by developing a convenient, nearly risk-free method of detecting small polyps. Computed tomography colonography (CTC) or CT-based virtual colonoscopy (VC) has shown a comparable performance to the gold-standard optical colonoscopy (OC) for detecting polyps of 8mm and larger by a less invasive manner. To be a screening tool, current CTC has to be advanced for acceptance by a larger population with higher detection capability on smaller polyps. These needs are documented by the recent refusal of CTC being accepted by Medicare coverage, such as reducing CT radiation, detecting smaller polyps, relieving bowel preparation (BP) stress, minimizing reader variation, improving efficiency, etc. We have made good progress in technical advancement toward the broad, long-term objective of this project, i.e., developing CTC as a safe, accurate, cost-effective, minimal-invasive, least-stressful screening modality. To advance CTC toward the long-term objective, the specific aims of this project renewal are: (1) To develop and evaluate an adaptive statistical reconstruction algorithm to obtain the current abdominal CT image quality at as low mAs level as achievable to minimize the risk of X-ray exposure. The algorithm will consider not only the X-ray quanta statistics and energy spectrum, but also the system background noise because this noise plays a noticeable role at low mAs level. (2) To develop and evaluate a partial-volume (PV) statistical segmentation algorithm with correction of fecal tagging inhomogeneity to improve electronic colon cleansing (ECC). The improvement will lead to the detection of smaller polyps, reduction of CT radiation by a half, and relief of patient stress on BP by approaching toward cathartic-free CTC. (3) To develop and evaluate an ECC-adaptive, texture-based, feature-extraction algorithm to improve computer-aided polyp detection (CADpolyp) toward enhancement of CTC cost-effectiveness. It is hoped that an improved performance with higher detection capability on smaller polyps and more acceptable by a large population (via less radiation and stress) would advance CTC toward a screening modality with acceptance by Medicare coverage. The low-mAs statistical reconstruction would be helpful to other CT applications. The PV image segmentation with correction of inhomogeneity would be beneficial to other virtual endoscopy applications, such as extracting blood vessel wall for plaque analysis in virtual angiography and bladder wall for early detection of growth in virtual cystography. PUBLIC HEALTH RELEVANCE: This proposal aims to develop computed tomography colonography (CTC) or CT-based virtual colonoscopy (VC) toward a screening modality by using (1) as low as achievable low-dose CT scan, (2) less-stressful bowel preparation (BP), e.g., minimal laxative and/or cathartic-free BP, and (3) integration of computer-aided detection (CAD) and three-dimensional (3D) endoscopic views for polyp detection.