15-20% of patients present with near obstructing left-sided colorectal cancer. CT colonography (CTC) or PET-CT has been used to detect synchronous lesions, which may alter preoperative planning of colonic resection. We aim to synthesize the usefulness of CT colonography and/or PET-CT in detecting synchronous proximal colon carcinomas in patients who have undergone an incomplete colonoscopy due to a stenosing or obstructing distal colorectal cancer.
A systematic review was performed by searching the databases up to December 2021. Data collected included demographics of the study population, rate of detection of synchronous carcinomas and impact on management of detection of synchronous carcinomas.
A total of 22 studies were included: 17 studies focused on CTC, 3 on PET-CT, and 2 integrated PET-CT with CTC; 2855 patients were included; 53% of patients were male, and 47% were female. All studies reported detection of synchronous proximal colorectal carcinomas using CTC, PET-CT or CTC, and PET-CT combined. CTC detected synchronous carcinomas in 0.2-12.2% of patients. PET-CT was useful in detecting synchronous carcinomas in 4.05-23% of patients. Integrated PET-CT and CTC detected synchronous carcinomas in 2-15% of patients. The surgical plan was changed in 2.4-14.3% of patients after the use of CTC. One PET-CT study reported a change in management in 13.5%. No complication was reported by the use of CTC.
CTC is an effective and useful adjunct to colonoscopy in assessing the proximal colon when colonoscopy fails to do so. However, more evidence is needed with the use of PET-CT for this patient population.

Following incomplete colonoscopy (IC) patients often undergo computed tomography colonography (CTC), but colon capsule endoscopy (CCE) may be an alternative. We compared the completion rate, sensitivity and diagnostic yield for polyp detection from CCE and CTC following IC. A systematic literature search resulted in twenty-six studies. Extracted data included inter alia, complete/incomplete investigations and polyp findings. Pooled estimates of completion rates of CCE and CTC and complete colonic view rates (CCE reaching the most proximal point of IC) of CCE were calculated. Per patient diagnostic yields of CCE and CTC were calculated stratified by polyp sizes. CCE completion rate and complete colonic view rate were 76% (CI 95% 68-84%) and 90% (CI 95% 83-95%). CTC completion rate was 98% (CI 95% 96-100%). Diagnostic yields of CTC and CCE were 10% (CI 95% 7-15%) and 37% (CI 95% 30-43%) for any size, 13% (CI 95% 9-18%) and 21% (CI 95% 12-32%) for >5-mm and 4% (CI 95% 2-7%) and 9% (CI 95% 3-17%) for >9-mm polyps. No study performed a reference standard follow-up after CCE/CTC in individuals without findings, rendering sensitivity calculations unfeasible. The increased diagnostic yield of CCE could outweigh its slightly lower complete colonic view rate compared to the superior CTC completion rate. Hence, CCE following IC appears feasible for an introduction to clinical practice. Therefore, randomized studies investigating CCE and/or CTC following incomplete colonoscopy with a golden standard reference for the entire population enabling estimates for sensitivity and specificity are needed.

OBJECTIVE: The purpose of this study was to perform a systematic review and meta-analysis of published studies on CT colonography (CTC) in which extracolonic findings were assessed.
METHODS: A systematic review of studies of screening CTC and of CTC to evaluate symptoms (1994-June 2017) was conducted to estimate the rate of extra-colonic findings and associated additional workup recommendations. The primary outcome was potentially important extracolonic findings, defined as CT Colonography Imaging Reporting and Data System (C-RADS) category E4 or as having high clinical importance (if C-RADS was not used). Secondary outcomes included likely unimportant extracolonic findings (i.e., C-RADS category E3 or similar). Random-effects and meta-regression analyses were used to generate pooled estimates and to explore risk factors for extracolonic findings related to various cohort characteristics.
RESULTS: Primary data were acquired from 44 studies (49,676 patients). The pooled rate of potentially important extracolonic findings was 4.9% (95% CI, 3.7-6.4%) with a high degree of heterogeneity (I2 = 95%). This estimate progressively declined over time (9% per year since 2006) and was significantly related to the reporting system (lower for C-RADS than for low, moderate, high clinical significance reporting). C-RADS-specific meta-analysis (32,746 patients) showed rates of potentially significant extracolonic findings in 2.8% (95% CI, 1.9-3.5%) of the cohort without symptoms and 5.2% (95% CI, 3.5-7.6%) of the cohort with symptoms and in 5.7% (95% CI, 3.3-9.8%) of seniors (≥ 65 years) versus 2.3% (95% CI, 1.2-4.5%) of those younger than 65 years. The overall pooled rates of recommended workup were 8.2% (95% CI, 6.6-10.1%) for all extracolonic findings and 4.0% (95% CI, 2.7-5.9%) for potentially important extracolonic findings.
CONCLUSIONS: With use of the more robust C-RADS classification, potentially important extracolonic findings at CTC occur in less than 3% of cohorts without symptoms. For all extracolonic findings, the rate of suggested or recommended additional workup is approximately 8% but decreases to 4% for potentially important extracolonic findings.

OBJECTIVE: We sought to perform a systematic review and meta-analysis of published CT colonography (CTC) studies assessing lesion detection in senior-age (≥ 65 years old) cohorts.
METHODS: We conducted a systematic review of CTC studies published between January 1994 and August 2017 containing data on senior-age adults. The primary endpoint was the CTC-positive rate for large colorectal polyps (≥ 10 mm) and masses. Secondary endpoints included lesions ≥ 6 mm, proven advanced neoplasia, and colorectal cancer (CRC). Study authors were contacted for additional missing data. Random-effects and meta-regression analyses were used to generate pooled estimates and explore contributing factors.
RESULTS: A total of 34 studies with 41,680 (18,798 senior-age) subjects were included. Pooled CTC-positive rates among senior-age patients using the 10-mm size threshold were significantly lower in cohorts of patients with no symptoms (8.2%; 95% CI, 6.0-11.1%) compared with cohorts of patients with positive fecal occult blood tests (32.8%; 95% CI, 15.4-56.7%) and other symptoms of CRC (14.0%; 95% CI, 12.0-16.1%). However, a uniformly high positive predictive value for advanced neoplasia at colonoscopy was seen for all senior-age cohorts using a 10-mm threshold (84.3%; 95% CI, 79.3-88.3%; I2 = 0.0) where such data were available. CTC sensitivity for CRC was 93.0% (95% CI, 89.0-95.0%) in senior-age patients compared with 92.0% (95% CI, 84.0-93.0%) in younger patients. Overall, CTC detection rates were higher in senior-age adults compared with younger adults.
CONCLUSIONS: On average, one in every 12 senior-age adults without symptoms of CRC who underwent screening would be referred to colonoscopy using the 10-mm threshold, with a high yield for advanced neoplasia and high sensitivity for cancer detection. As expected, CTC-positive rates were higher in cohorts of patients 65 years old or older with symptoms of CRC. These results should help inform the Centers for Medicare & Medicaid Services regarding coverage determination of CTC screening for Medicare beneficiaries.

Colorectal cancer (CRC) is a significant cause of morbidity and mortality. Optical colonoscopy (OC) is the first choice of investigation for assessing the state of the colon and it is excellent for CRC screening. Newer technologies such as computed tomography colonography (CTC) may also be useful in CRC screening. This systematic review compares the benefits of CTC and OC for CRC screening. This review includes all the available randomized clinical trials comparing CTC and OC for CRC screening in asymptomatic patients. Three studies were included in the systematic review and were submitted for meta-analysis. In the analysis of participation rates, only 2,333 of 8,104 (29%) patients who were invited for screening underwent the CTC, and only 1,486 of the 7,310 (20%) patients who were invited for screening underwent OC. The absolute risk difference in participation rate in the two procedures was 0.1 (95% CI, 0.05-0.14) in favor of CTC. In the analysis of advanced colorectal neoplasia (ACN) detection rates, 2,357 patients undergoing CTC and 1,524 patients undergoing OC were included. Of these, 135 patients (5.7%) who underwent a CTC and 130 patients (8.5%) who underwent an OC were diagnosed with ACN. The absolute risk difference in ACN detection rate in the two procedure types was -0.02 (with a 95% CI between -0.04 and -0.00) in favor of OC. CTC is an option for CRC screening in asymptomatic patients. However, as CTC was inferior in detecting ACN, it should not replace OC, which remains the gold standard.

BACKGROUND: Several dedicated computed tomography (CT) colonography phantoms have been described previously.
OBJECTIVE: To compare their pros and cons and describe the construction of a dedicated phantom that can be easily manufactured.
METHODS: We found 15 different phantom designs by literature search and compared their advantages and disadvantages based on their description and images. We tested various materials for density and mechanical properties and constructed a phantom from polypropylene pipes (30 mm and 50 mm in diameter, 52 cm in length). Haustral folds were created by heat shaping and 39 intermediate sessile polyps with a target size of 6-10 mm and two flat lesions were created from silicone. Nine polyps were attached to a fold. The model was placed in a 30-cm barrel filled with water to simulate attenuation of human body. Attenuation of polyps was compared to intermediate polyps found in patients.
RESULTS: None of the earlier colonic phantoms found in the literature incorporated all the properties that would ensure both reproducibility and validity of the model (including a rigid wall, density of the wall and polyps similar to human colon, at least two levels of distension and durability). In the present phantom, the average size of sessile polyps was 8.6 ± 0.9 mm and their density was 53 ± 24 HU. We found no significant difference in polyp density between simulated polyps in the phantom and polyps in human subjects (P = 0.70). All polyps, with the exception of one flat lesion, were detected by computer aided detection.
CONCLUSIONS: We constructed and validated a CT colonography phantom with correct density allowing performance of reproducible experiments.

OBJECTIVE: To review primary research evidence investigating performance of CT colonography for colorectal cancer surveillance. The financial impact of using CT colonography for surveillance was also estimated.
METHODS: We identified primary studies of CT colonography for surveillance of colorectal cancer patients. A summary ROC curve was constructed. Inter-study heterogeneity was explored using the I2 value. Financial impact was estimated for a theoretical cohort of patients, based on Cancer Research UK statistics.
RESULTS: Seven studies provided data on 880 patients. Five of seven studies (765 patients) were included for qualitative analysis. Sensitivity of CT colonography for detection of anastomotic recurrence was 95 % (95 % CI 62 - 100), specificity 100 % (95 % CI 75 - 100) and sensitivity for metachronous cancers was 100 %. No statistical heterogeneity was detected (I2 = 0 %). We estimated that CT colonography as a \'single test\' alternative to colonoscopy and standard CT for surveillance would potentially save €20,785,232 (£14,803,404) for an annual cohort of UK patients.
CONCLUSIONS: CT colonography compares favourably to colonoscopy for detection of anastomotic recurrence and metachronous colorectal cancer, and appears financially beneficial. These findings should be considered alongside limitations of small patient numbers and high clinical heterogeneity between studies.
CONCLUSIONS: • CT colonography compares favourably to colonoscopy/standard CT for colorectal cancer surveillance. • CT colonography offers single-test luminal, serosal and extra-colonic assessment. • CT colonography is a potentially cost-saving alternative to standard surveillance protocols.

Medical imaging has been indispensable in medicine since the discovery of x-rays. Medical imaging offers useful information on patients\' medical conditions and on the causes of their symptoms and diseases. As imaging technologies advance, a large number of medical images are produced which physicians/radiologists must interpret. Thus, computer aids are demanded and become indispensable in physicians\' decision making based on medical images. Consequently, computer-aided detection and diagnosis (CAD) has been investigated and has been an active research area in medical imaging. CAD is defined as detection and/or diagnosis made by a radiologist/physician who takes into account the computer output as a \"second opinion\". In CAD research, detection and diagnosis of lung and colorectal cancer in thoracic and colonic imaging constitute major areas, because lung and colorectal cancers are the leading and second leading causes, respectively, of cancer deaths in the U.S. and also in other countries. In this review, CAD of the thorax and colon, including CAD for detection and diagnosis of lung nodules in thoracic CT, and that for detection of polyps in CT colonography, are reviewed.