Developing Virtual Colonoscopy for Cancer Screening

描述（由申请人提供）：结直肠癌是美国第三大最常诊断的癌症，也是第二大癌症死亡原因。它通常在患者出现症状后的晚期才被诊断出来，这解释了它的高死亡率。由于大多数结肠癌是由5至15年恶性转化期的息肉引起的，因此一直提倡筛查小息肉。不幸的是，大多数人并没有遵循这个建议。这个项目与健康的关系是通过开发一种方便、几乎无风险的检测小息肉的方法，来显著增加愿意参与筛查项目的人数。计算机断层扫描结肠镜检查（CTC）或基于ct的虚拟结肠镜检查（VC）已显示出与金标准光学结肠镜检查（OC）相当的性能，以较小的侵入性方式检测8mm及更大的息肉。为了成为一种筛查工具，目前的CTC必须被更大的人群所接受，对较小的息肉具有更高的检测能力。这些需求通过最近拒绝接受医疗保险覆盖的CTC来证明，例如减少CT辐射，检测较小的息肉，缓解肠准备（BP）压力，尽量减少阅读器的变化，提高效率等。我们在技术进步方面取得了良好的进展，朝着这个项目广泛的、长期的目标，即发展CTC作为一种安全、准确、成本效益高、微创、压力最小的筛查方式。为了推动CTC朝着长远目标发展，本课题更新的具体目标是：(1)开发和评估一种自适应统计重建算法，以尽可能低的mAs水平获得当前腹部CT图像质量，以最大限度地降低x射线暴露风险。该算法不仅考虑了x射线量子统计和能谱，还考虑了系统背景噪声，因为在低mAs水平下，系统背景噪声的作用非常明显。(2)开发并评估一种校正粪便标记不均匀性的部分体积（PV）统计分割算法，以改善电子结肠清洗（ECC）。这种改善将导致更小的息肉的发现，减少一半的CT辐射，并通过接近无导管的CTC减轻患者对BP的压力。(3)开发和评估一种自适应、基于纹理的特征提取算法，以改进计算机辅助息肉检测（CADpolyp），提高CTC的成本效益。希望CTC的性能得到改善，对较小的息肉具有更高的检测能力，更容易被大量人群接受（通过更少的辐射和压力），这将推动CTC成为一种被医疗保险所接受的筛查方式。低mas统计重建对其他CT应用有一定的指导意义。对不均匀性进行校正的PV图像分割将有利于虚拟内窥镜的其他应用，例如在虚拟血管造影中提取血管壁用于斑块分析，在虚拟膀胱造影中提取膀胱壁用于早期检测生长。

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.