Contrast-enhanced CT colonography in recurrent colorectal carcinoma: feasibility of simultaneous evaluation for metastatic disease, local recurrence, and metachronous neoplasia in colorectal carcinoma

Patient-Specific Phantomless Estimation of Bone Mineral Density and Its Effects on Finite Element Analysis Results: A Feasibility Study

Objectives

This study proposes a regression model for the phantomless Hounsfield units (HU) to bone mineral density (BMD) conversion including patient physical factors and analyzes the accuracy of the estimated BMD values.

Methods

The HU values, BMDs, circumferences of the body, and cross-sectional areas of bone were measured from 39 quantitative computed tomography images of L2 vertebrae and hips. Then, the phantomless HU-to-BMD conversion was derived using a multiple linear regression model. For the statistical analysis, the correlation between the estimated BMD values and the reference BMD values was evaluated using Pearson's correlation test. Voxelwise BMD and finite element analysis (FEA) results were analyzed in terms of root-mean-square error (RMSE) and strain energy density, respectively.

Results

The HU values and circumferences were statistically significant (p < 0.05) for the lumbar spine, whereas only the HU values were statistically significant (p < 0.05) for the proximal femur. The BMD values estimated using the proposed HU-to-BMD conversion were significantly correlated with those measured using the reference phantom: Pearson's correlation coefficients of 0.998 and 0.984 for the lumbar spine and proximal femur, respectively. The RMSEs of the estimated BMD values for the lumbar spine and hip were 4.26 ± 0.60 (mg/cc) and 8.35 ± 0.57 (mg/cc), respectively. The errors of total strain energy were 1.06% and 0.91%, respectively.

Conclusions

The proposed phantomless HU-to-BMD conversion demonstrates the potential of precisely estimating BMD values from CT images without the reference phantom and being utilized as a viable tool for FEA-based quantitative assessment using routine CT images.

Prospective Trial Evaluating the Surgical Anastomosis at One-Year Colorectal Cancer Surveillance: CT Colonography Versus Optical Colonoscopy and Implications for Patient Care

OBJECTIVE

The aim of this study was to compare the accuracy of CT colonography versus optical colonoscopy for neoplastic involvement at the surgical anastomosis 1 year after curative-intent colorectal cancer resection.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

Two hundred one patients (mean age, 58.6 years; 117 men, 84 women) underwent same-day contrast-enhanced CT colonography and colonoscopy approximately 1 year (mean, 12.1 months; median, 11.9 months) after colorectal cancer resection as part of a prospective, multicenter trial. All patients enrolled were without clinical evidence of disease and considered low risk for recurrence (stage I-III).

MAIN OUTCOME MEASURES

Suspected neoplastic lesions within 5 cm of the colonic anastomosis were recorded at CT colonography, with subsequent colonoscopy performed for the same, with segmental unblinding of colonography findings. Anastomotic region biopsy or polypectomy was performed at the endoscopist's discretion.

RESULTS

None of the 201 patients had intraluminal anastomotic cancer recurrence or advanced neoplasia (or metachronous cancers). CT colonography detected extramural perianastomotic recurrence in 2 patients (1.0%); neither was detected at colonoscopy. Only 2 patients (1.0%; 2/201) were called positive at CT colonography for intraluminal anastomotic nondiminutive lesions (7- to 8-mm polyps), which were confirmed at colonoscopy but nonneoplastic at histopathology. At optical colonoscopy, the anastomosis was deemed abnormal and/or biopsied in 10.0% (20/201), yielding only 1 nondiminutive benign neoplasm (7-mm tubular adenoma).

LIMITATIONS

The lack of luminal cancer recurrence in our lower-risk cohort precludes assessment of sensitivity for detection, rendering the study underpowered in this regard. Potential cost savings of combined CT/CT colonography over the standard CT/colonoscopy approach were not assessed.

CONCLUSIONS

Relevant intraluminal anastomotic pathology appears to be very uncommon 1 year after colorectal cancer resection in lower-risk cohorts. Unlike colonoscopy, diagnostic contrast-enhanced CT colonography effectively evaluates both the intra- and extraluminal aspects of the anastomosis. See Video Abstract at http://links.lww.com/DCR/A471.

Computed tomography colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications

Colorectal cancer (CRC) represents one of the most relevant causes of morbidity and mortality in Western societies. CRC screening is actually based on faecal occult blood testing, and optical colonoscopy still remains the gold standard screening test for cancer detection. However, computed tomography colonography (CT colonography) constitutes a reliable, minimally-invasive method to rapidly and effectively evaluate the entire colon for clinically relevant lesions. Furthermore, even if the benefits of its employment in CRC mass screening have not fully established yet, CT colonography may represent a reasonable alternative screening test in patients who cannot undergo or refuse colonoscopy. Therefore, the purpose of our review is to illustrate the most updated recommendations on methodology and the current clinical indications of CT colonography, according to the data of the existing relevant literature.

Early detection of colorectal cancer recurrence in patients undergoing surgery with curative intent: current status and challenges

Despite advances in neoadjuvant and adjuvant therapy, attention to proper surgical technique, and improved pathological staging for both the primary and metastatic lesions, almost half of all colorectal cancer patients will develop recurrent disease. More concerning, this includes ~25% of patients with theoretically curable node-negative, non-metastatic Stage I and II disease. Given the annual incidence of colorectal cancer, approximately 150,000 new patients are candidates each year for follow-up surveillance. When combined with the greater population already enrolled in a surveillance protocol, this translates to a tremendous number of patients at risk for recurrence. It is therefore imperative that strategies aim for detection of recurrence as early as possible to allow initiation of treatment that may still result in cure. Yet, controversy exists regarding the optimal surveillance strategy (high-intensity vs. traditional), ideal testing regimen, and overall effectiveness. While benefits may involve earlier detection of recurrence, psychological welfare improvement, and greater overall survival, this must be weighed against the potential disadvantages including more invasive tests, higher rates of reoperation, and increased costs. In this review, we will examine the current options available and challenges surrounding colorectal cancer surveillance and early detection of recurrence.

CT colonography in the diagnosis and management of colorectal cancer: Emphasis on pre- and post-surgical evaluation

This article addresses the use of computed tomographic colonography (CTC) for the diagnosis and management of colorectal cancer, focusing on presurgical evaluation of the colon proximal to an occlusive cancer and surveillance after cancer resection surgery. The key evidences accumulated in the literature and future work needed are summarized. CTC is a technically robust and the most practical method to evaluate the colon proximal to an occlusive cancer, which prevents colonoscopic examination past the occlusion, either before or after metallic stent placement. The high sensitivity of CTC for detecting cancers and advanced adenomas in the proximal colon can help prevent additional surgical procedures in patients showing negative results. However, the accuracy of CTC for distinguishing intramural cancers from adenomas is low, and the technique is limited in guiding management when a medium-sized lesion that do not show invasive features such as pericolic extension or nodal metastasis is found in the proximal colon. A maximal diameter ≥ 15 mm has been proposed as a criterion for surgical removal of proximal lesions. However, this needs to be verified in a larger cohort. In addition, the influence of presurgical CTC results on the current post-cancer resection colonic surveillance timeline remains to be determined. CTC can be readily added to the routine abdominopelvic CT in the form of contrast-enhanced CTC, which can serve as an effective stand-alone tool for post-cancer resection surveillance of both the colorectum and extracolonic organs. Although the accuracy of CTC has been demonstrated, its role in the current colonoscopy-based postoperative colonic surveillance protocols remains to be determined. Readers of CTC also need to be knowledgeable on the colonic lesions that are unique to the postoperative colon.

CT colonography in patients who have undergone sigmoid colostomy: a feasibility study

OBJECTIVE

The purpose of this study was to evaluate the technical feasibility of CT colonography of patients who have undergone sigmoid colostomy after abdominoperineal resection.

MATERIALS AND METHODS

Seven men and 11 women (mean age, 57.2 ± 14.5 [SD] years) who had undergone abdominoperineal resection with sigmoid colostomy for rectal cancer were included. Colonic cleansing and fecal tagging were performed with magnesium citrate and 5% weight/volume barium. A conventional small rectal catheter with a retention balloon was introduced into the colonic stoma. An inflated balloon (15-25 mL) was positioned several centimeters beneath the skin. The interposed tissue acted as the mechanism for preventing balloon expulsion during colonic insufflation with carbon dioxide. Unenhanced right decubitus and contrast-enhanced supine images were obtained. Air-fluid leak, balloon expulsion, complications, and colonic distention evaluated on a 4-point scale in which 1 was the worst and 4 the best and mucosal coverage were assessed.

RESULTS

Examinations were performed uneventfully for all but one patient, who had temporary air and fluid leakage. The mean amount of carbon dioxide used was 2.64 ± 0.64 L. In the right decubitus position, the mean distention grade of each colonic segment was 2.7 ± 1.1 (sigmoid), 3.4 ± 0.6 (descending), 3.6 ± 0.5 (transverse), 3.6 ± 0.5 (ascending), and 3.7 ± 0.5 (cecum). In the supine position the mean grades were 2.7 ± 1.2, 3.1 ± 0.7, 3.7 ± 0.5, 3.7 ± 0.5, and 3.8 ± 0.4. Four patients (22.2%) had segments not adequately visualized in either position owing to luminal collapse; all of these segments were in the sigmoid colon. Three patients (16.7%) had areas submerged under fecal matter in both positions, but these areas were evaluable because of fecal tagging or IV contrast enhancement.

CONCLUSION

CT colonographic examination through a sigmoid stoma was technically feasible with currently available instruments, but further improvements in technique are needed.

Colon distension and scan protocol for CT-colonography: an overview

This article reviews two important aspects of CT-colonography, namely colonic distension and scan parameters. Adequate distension should be obtained to visualize the complete colonic lumen and optimal scan parameters should be used to prevent unnecessary radiation burden. For optimal distension, automatic carbon dioxide insufflation should be performed, preferably via a thin, flexible catheter. Hyoscine butylbromide is - when available - the preferred spasmolytic agent because of the positive effect on insufflation and pain/burden and its low costs. Scans in two positions are required for adequate distension and high polyp sensitivity and decubitus position may be used as an alternative for patients unable to lie in prone position. The great intrinsic contrast between air or tagging and polyps allows the use of low radiation dose. Low-dose protocol without intravenous contrast should be used when extracolonic findings are deemed unimportant. In patients suspected for colorectal cancer, normal abdominal CT scan protocols and intravenous contrast should be used in supine position for the evaluation of extracolonic findings. Dose reduction can be obtained by lowering the tube current and/or voltage. Tube current modulation reduces the radiation dose (except in obese patients), and should be used when available. Iterative reconstructions is a promising dose reducing tool and dual-energy CT is currently evaluated for its applications in CT-colonography. This review also provides our institution's insufflation procedure and scan parameters.

[CT colonography: what radiologists need to know]

In 2008, CT colonography was approved by the American Cancer Society as a technique for screening for colorectal cancer. This approval should be considered an important step in the recognition of the technique, which although still relatively new is already changing some diagnostic algorithms. This update about CT colonography reports the quality parameters necessary for a CT colonographic study to be diagnostic and reviews the technical innovations and colonic preparation for the study. We provide a brief review of the signs and close with a discussion of the current indications for and controversies about the technique.

Computed tomographic colonography in preoperative evaluation of colorectal tumors: a prospective study

Background

This study aimed to assess the usefulness of computed tomographic colonography (CTC) in preoperative evaluation of colorectal tumors and the entire bowel including endoscopically inaccessible regions.

Methods

Colonoscopy and CTC were performed for 49 patients. The tumor and the entire colon were assessed, and the results were compared with colonoscopy. The extraluminal findings of CTC were compared with contrast-enhanced computed tomography (CT) of the abdomen and the pelvis in 33 patients. All these patients had undergone surgery. A comparison of results for tumor node metastasis classification between CTC, CT, and histopathology was performed.

Results

Exploration of the entire colon was possible for 89.8% of the patients using CTC and 49.0% of the patients using colonoscopy. Bowel cleansing was assessed as worse with CTC. In the evaluation of tumor location and morphologic type, CTC was congruent with colonoscopy. Colonoscopy enabled approximate tumor size and volume to be evaluated for only 59.2% (29/49) and 30.6% (15/49) of patients, respectively, whereas CTC enabled evaluation of all 48 (100.0%) visualized tumors. Wall thickening, outer contour, and suspected infiltration of surrounding tissues and organs are impossible to determine with colonoscopy but can be determined with CTC. Using CTC, two additional tumors were found proximate to occlusive masses in endoscopically inaccessible regions.

Conclusion

Computed tomographic colonography is a useful method for diagnosing colorectal tumors. It allows the clinician to diagnose tumor, determine local tumor progression, and detect synchronous lesions in the large bowel including endoscopically inaccessible regions.

CT colonography for combined colonic and extracolonic surveillance after curative resection of colorectal cancer

PURPOSE

To determine the accuracy of contrast material-enhanced computed tomographic (CT) colonography for postoperative surveillance in colorectal cancer patients without clinical or laboratory evidence of disease recurrence.

MATERIALS AND METHODS

The Institutional Review Board approved this HIPAA-compliant study and waived informed consent. Between January 2006 and December 2007, 742 consecutive patients without clinical or laboratory evidence of recurrence following curative-intent colorectal cancer surgery underwent contrast-enhanced CT colonography. Of these, 548 patients who had subsequent colonoscopy and pathologic confirmation of colonic lesions (reference standard) were included in the colonic analysis. All 742 patients were included in the extracolonic analysis. Sensitivity and specificity of CT colonography for nonanastomotic colonic lesions at least 6 mm in size and anastomotic lesions of any size, including performance according to lesion histologic type, were determined. Diagnostic yields of contrast-enhanced CT colonography for colonic cancers and for extracolonic recurrences were obtained.

RESULTS

CT colonography depicted all six metachronous cancers and one anastomotic recurrence within the colon in six patients (0.8%; 95% confidence interval [CI]: 0.3%, 1.8%]), for per-patient and per-lesion sensitivities of 100% (95% CIs: 64.3%, 100% and 67.8%, 100%, respectively). All cancer lesions within the colon were amenable to additional curative treatment. CT colonography per-patient and per-lesion sensitivity was 81.8% (95% CI: 60.9%, 93.3%) and 80.8% (95% CI: 64.3%, 97.2%), respectively, for advanced neoplasia and 80.0% (95% CI: 68.6%, 88.1%) and 78.5% (95% CI: 68.3%, 88.7%), respectively, for all adenomatous lesions. Negative predictive values for adenocarcinoma, advanced neoplasia, and all adenomatous lesions were 100%, 99.1%, and 97.0%, respectively. CT colonography specificity was 93.1% (95% CI: 90.4%, 95.2%). Contrast-enhanced CT colonography enabled detection of extracolonic recurrences in an additional 11 patients (1.5%; 95% CI: 0.8%, 2.7%).

CONCLUSION

Contrast-enhanced CT colonography is an accurate and practical surveillance tool following colorectal cancer surgery in patients without clinical or laboratory evidence of recurrence, allowing for simultaneous less-invasive evaluation of both colon and extracolonic organs.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.10100385/-/DC1.

CT colonography in detection of colorectal carcinoma

BACKGROUND

Diagnostic methods used in screening and detecting colorectal carcinoma are digitorectal examination, faecal occult blood testing, sigmoidoscopy, DNA stool analysis, barium enema, colonoscopy, and as of recently CT colonography. The aim of this study was to establish diagnostic accuracy and comfort of CT colonography compared to colonoscopy and barium enema.

PATIENTS AND METHODS

We included 231 patients in the prospective study. For all patients CT colonography and barium enema followed by colonoscopy were performed. After the procedures a comfort assessment was done in all patients. Diagnostic positive results were verified by the pato-histological examination. Sensitivity, specificity, positive predicative value (PPV) and negative predicative value (NPV) were calculated for each procedure.

RESULTS

With CT colonography, barium enema and colonoscopy 95 lesions were found, 56 (59%) of them were tumours and 39 (41%) were polyps. Among polyps pato-histology revealed 34 adenomas, 3 tubulovillous adenomas and 2 lipomas, among tumours there were 55 adenocarcinomas and 1 lymphoma. Results showed CT colonography sensitivity to polyps to be 89.7%, barium enema 48.7%, and colonoscopy 94.9%. Sensitivity to tumours of CT colonography and colonoscopy was 100% and of barium enema 94.6%. Specificities and PPV were 100% in all procedures. The comfort assessment showed CT colonography as the far most comfortable out of three procedures.

PET/CT pattern analysis for surgical staple line recurrence in patients with colorectal cancer

OBJECTIVE

The purpose of our study was to determine whether (18)F-FDG PET/CT interpretation with metabolic-anatomic pattern analysis can be used to accurately assess for surgical staple line recurrence after colorectal cancer resection.

MATERIALS AND METHODS

Seventy-nine consecutive patients with previous surgical resection of colorectal cancer were studied retrospectively. The surgical anastomotic or Hartmann's pouch staple lines were evaluated for presence or absence of tumor recurrence with FDG PET/CT metabolic-anatomic pattern analysis. Focal, eccentric, or perianastomotic CT masses with any associated PET pattern were regarded as positive for staple line recurrence. If the perianastomotic CT abnormality was presacral in location, then FDG uptake at least as intense as normal liver was required for positive interpretation. Eccentric or perianastomotic PET patterns matched with normal or diffuse thickening CT patterns were regarded as indeterminate. Presence or absence of recurrent tumor was confirmed by pathology, surgery, colonoscopy, imaging follow-up of at least 3 months, or clinical follow-up of at least 1 year.

RESULTS

Nine patients (11.4%) had staple line recurrence and 70 (88.6%) did not. FDG PET/CT interpretation yielded sensitivity, specificity, positive predictive value, negative predictive value, and accuracy results of 100% (9/9), 97.1% (68/70), 81.8% (9/11), 100% (68/68), and 97.5% (77/79), respectively. All nine patients with staple line recurrence showed perianastomotic or eccentric masses on CT, eight with matching perianastomotic or eccentric FDG uptake patterns. Background, diffuse, curvilinear, or focal FDG uptake patterns, regardless of FDG uptake intensity, paired with normal findings or diffuse mural thickening on CT were seen only in patients without staple line recurrence.

CONCLUSION

FDG PET/CT pattern analysis enables accurate assessment for staple line recurrence in patients with previous resection of colorectal cancer. The most reliable PET/CT pattern predicting staple line recurrence is an eccentric or perianastomotic mass on CT with corresponding eccentric or perianastomotic FDG uptake on PET. Background, diffuse (on one or both sides of the staple line), curvilinear, and focal patterns of FDG uptake do not correlate with recurrence in the absence of a mass on CT.

Contrast-enhanced CT colonography with 64-slice MDCT compared to endoscopic colonoscopy in the follow-up of patients after colorectal cancer resection

BACKGROUND

Seventy percent of newly diagnosed colorectal cancer cases are potential candidates for curative surgery, but after resection, in 30%, the tumor will recur. Postoperative follow-up includes endoscopic colonoscopy (EC) and computed tomography (CT). There have been only a few publications on the use of contrast-enhanced CT colonography (CECTC) in the follow-up of these patients.

METHODS

Twenty-nine consecutive patients after resection of colorectal cancer underwent CECTC and EC on the same day. CECTC studies were reviewed for identification of strictures, recurrence, polyps and metastases.

RESULTS

The anastomosis was identified in 96% of patients on CECTC and in 82% on endoscopic colonoscopy. One stricture was identified by both techniques. One extraluminal recurrence was depicted only on CECTC. Sensitivity in detecting polyps was per polyp 93% and per patient 100%.

CONCLUSION

CECTC performed on a 64-slice multidetector CT is reliable in imaging the postoperative colon for the follow-up of patients after resection of colorectal cancer.

Virtual endoscopy using CT scan

The term virtual endoscopy refers to using either spiral computed tomography (CT colonography) or magnetic resonance scanning (MR colonography) combined with computer technology to produce high-resolution two- and three-dimensional imaging of the large bowel. Current CT techniques require meticulous bowel preparation and gas insufflation prior to the examination. The advantages of CT colonography over conventional colonography include safety, its ability to demonstrate the entire large bowel in almost all patients, even following incomplete endoscopy, to accurately localize lesions, and to examine the entire colon in patients with obstructing tumors. Additionally, CT colonography allows simultaneous preoperative tumor staging. Screening for colorectal polyps is a controversially discussed indication for CT colonography. Sensitivity and specificity range widely and decrease with decreasing polyp size. However, better results can be achieved using multidetector technology. Most frequently, the examination is well tolerated and assessed by patients to be more acceptable than conventional colonoscopy. There are no reported complications from CT colonography. The procedure requires a scan time of about 25 to 30 seconds with new multidetector CT scanners, and sedation is not used. Currently, CT colonography is less cost-effective than conventional endoscopy. Another disadvantage is the relatively high irradiation exposure associated with CT colonography. Therefore, at the moment, this technique does not appear ready to be included in general screening strategies. However, ongoing and future improvements may prove its value in colorectal examination strategies.

Whole-body PET/CT-colonography: a possible new concept for colorectal cancer staging

BACKGROUND

Colorectal cancer (CRC) is a leading cause of death, and necessitates a conjointly performed staging. Until now, a multi-step-examination including optical colonoscopy, cross-sectional and functional imaging is recommended. However, a single examination for whole-body staging with a dedicated CRC staging protocol is desirable. Thus, we developed and evaluated a combined whole-body PET/CT-colonography protocol for dedicated CRC staging in routine clinical use.

METHODS

We integrated CT-colonography into a whole-body PET/CT protocol to achieve a specific "all-in-one" examination for patients suspected of having CRC. After oral and rectal bowel distension, PET/CT-colonography has been performed in 55 patients. All patients had optical colonoscopy one day before PET/CT. PET/CT data sets were evaluated concerning detection and evaluation of colorectal tumour sites, lymph nodes and distant metastases; these results were compared to the results of CT-colonography alone. Surgical resection and/or biopsy served as standards of reference in all patients.

RESULTS

All examinations were fully diagnostic and well tolerated by the patients. PET/CT-colonography showed highly accurate results for overall TNM-evaluation and was significantly more accurate than CT-colonography alone.

CONCLUSIONS

Staging patients with whole-body PET/CT-colonography is technically feasible and accurate. Patients with incomplete colonoscopy or potential synchronous bowel lesions might benefit from this approach.

CT colonography: current status and future promise

CT colonography (CTC) is an innovative technology that entails CT examination of the entire colon and computerized processing of the raw data after colon cleansing and colonic distention. CTC could potentially increase the screening rate for colon cancer because of its relative safety, relatively low expense, and greater patient acceptance, but its role in mass colon cancer screening is controversial because of its highly variable sensitivity, the inability to sample polyps for histologic analysis, and lack of therapeutic capabilities. This article reviews the CTC literature, including imaging and adjunctive techniques, radiologic interpretation, procedure indications, contraindications, risks, sensitivity, interpretation pitfalls, and controversies.

Colonography by CT, MRI and PET/CT combined with conventional colonoscopy in colorectal cancer screening and staging

Colorectal cancer (CRC) remains a leading cancer killer worldwide. But the disease is both curable and preventable at an early stage. Regular CRC cancer screening has been shown to reduce the risk of dying from CRC. However, the importance of large-scale screening is only now starting to be appreciated. This article reviews a variety of imaging procedures available for detecting ulcerative colitis (UC) and Crohn’s disease (CD), polyps and CRC in their early stage and also presents details on various screening options. Detecting, staging and re-staging of patients with CRC also require multimodality, multistep imaging approaches. Staging and re-staging with conventional colonoscopy (CC), computer tomography colonography (CTC), magnetic resonance colonography (MRC) and positron emission tomography/computer tomography colonography (PET/CTC) are of paramount importance in determining the most appropriate therapeutic method and in predicting the risk of tumor recurrence and overall prognosis. The advantages and limitations of these modalities are also discussed.

Fundamental elements for successful performance of CT colonography (virtual colonoscopy)

There are many factors affecting the successful performance of CT colonography (CTC). Adequate colonic cleansing and distention, the optimal CT technique and interpretation with using the newest CTC software by a trained reader will help ensure high accuracy for lesion detection. Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation. Automated carbon dioxide insufflation is more efficient and may be safer for colonic distention as compared to manual room air insufflation. CT scanning should use thin collimation of < or =3 mm with a reconstruction interval of < or =1.5 mm and a low radiation dose. There is not any one correct method for the interpretation of CTC; therefore, readers should be well-versed with both the primary 3D and 2D reviews. Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system. The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.

Resection of peritoneal metastases causing malignant small bowel obstruction

Background

Resection of peritoneal metastases has been shown to improve survival in patients with abdominal metastatic disease from abdominal or extra abdominal malignancy. This study evaluates the benefit of peritoneal metastatic resection in patients with malignant small bowel obstruction and a past history of treated cancer.

Patients and methods

Patients undergoing laparotomy for resection of peritoneal metastases from recurrence of previous cancer between 1992–2003 were reviewed retrospectively. Data were collected about type of primary cancer, interval to recurrence, extent of the disease and completeness of resection, morbidity and mortality and long-term survival.

Results

Between 1992 and 2003 there were 79 patients (median age 62, range 19–91) who had laparotomy for small bowel obstruction due to recurrent cancer. The primary cancer was colorectal (31), gynaecologic cancer (19), melanoma (16) and others (13). Overall, the rate of complications was 35% and mortality was 10%. Median survival was 5 months; patients with history of colorectal cancer had better survival than other cancer (median survival 7 months vs. 4 months; p = 0.02). Multivariate analysis showed that the extent of recurrent disease was the only factor that affected overall survival.

Conclusion

Laparotomy for small bowel obstruction is a worthwhile option for patients with malignant small bowel obstruction. Although it is associated with significant morbidity and mortality it offers a reasonable survival benefit in particular for patients with completely resectable disease.

Colorectal cancer: imaging surveillance following resection of primary tumour

Most patients with colorectal cancer undergo treatment with curative intent and subsequently enter a surveillance programme. The primary aim of surveillance is to identify patients with disease relapse at a resectable stage. However, the identification of local recurrence and metachronous carcinoma are also important aspects of follow up. Patients under observation may be referred for imaging either because regular imaging forms part of the surveillance strategy, or because tumour relapse is suggested by the development of new symptoms or a rise in tumour markers. This paper reviews the use of new and existing imaging techniques during surveillance following resection of primary colorectal cancer. The use of imaging for this surveillance is an application of cancer imaging that is supported by evidence-based clinical guidelines. Computed tomography provides the mainstay modality on grounds of good overall diagnostic performance combined with high availability and low cost. Improvements in survival with more aggressive follow up and treatment are likely to demand more accurate imaging techniques in the future.

CT colonography for follow-up after surgery for colorectal cancer

OBJECTIVE

The purpose of this article is to discuss the CT colonography (CTC) findings and the role of CTC for follow-up after curative surgery for colorectal cancer.

CONCLUSION

Contrast-enhanced CTC can be effective for surveillance for colorectal cancer recurrence after curative surgery because it enables simultaneous evaluation of distant abdominal metastasis, pericolic recurrence, intraluminal recurrence, and metachronous lesions. The appearances of anastomotic recurrences at CTC overlap with those of more common inflammatory polyps and rare benign ulcers.

Colorectal polyps on portal phase contrast-enhanced CT colonography: lesion attenuation and distinction from tagged feces

OBJECTIVE

The purpose of our study was to determine the attenuation of colorectal polyps on portal phase contrast-enhanced CT colonography (CTC) and evaluate whether enhanced polyps can be clearly distinguished from tagged feces during CTC review.

MATERIALS AND METHODS

Our institutional review board approved this study and waived patient informed consent. Forty-eight colonoscopy-proven polyps (6-20 mm) and 41 polypoid tagged feces (6-19 mm) were selected from contrast-enhanced CTC performed without (n = 37 examinations) and with (n = 10 examinations) fecal tagging, respectively. Scanning was performed 72 seconds after i.v. injection of 150 mL of contrast material at a rate of 2.5 mL/s. Fecal tagging consisted of three doses of 200 mL of 5% weight/volume (w/v) barium sulfate suspension taken at each meal the day before CTC. Attenuation of the polyps and tagged feces was measured. Four independent blinded radiologists reviewed the polyps and tagged feces at both wide (width, 1,500 H; level -400 H) and soft-tissue (width, 400 H; level, 20 H) window settings to distinguish them by using subjective visual assessment.

RESULTS

Polyp attenuation on the portal phase was not correlated with size (R = -0.003; p = 0.99) and was not different between histologic types (p = 0.884). Enhanced polyps (mean +/- SD, 119.9 +/- 25.3 H; range, 50-173 H) showed significantly lower attenuation than did tagged feces (1,521.4 +/- 683.6 H; range, 495-2,683 H) without any overlap (p < 0.0005). An 8-mm sessile adenomatous polyp was misinterpreted as tagged feces by one reviewer. The rest of the lesions were correctly interpreted by all reviewers, resulting in high interobserver agreement (kappa value, 0.988).

CONCLUSION

Polyp attenuation on portal phase contrast-enhanced CTC ranges from 50 to 173 H. Contrast-enhanced polyps are clearly and consistently distinguished from barium-tagged polypoid feces.

Pitfalls in Multi–Detector Row CT Colonography: A Systematic Approach

Thin-section multi-detector row computed tomographic (CT) colonography is a powerful tool for the detection and classification of colonic lesions. However, each step in the process of a CT colonographic examination carries the potential for misdiagnosis. Suboptimal patient preparation, CT scanning protocol deficiencies, and perception and interpretation errors can lead to false-positive and false-negative findings, adversely affecting the diagnostic performance of CT colonography. These problems and pitfalls can be overcome with a variety of useful techniques and observations. A relatively clean, dry, and well-distended colon can be achieved with careful patient preparation, thereby avoiding the problem of residual stool and fluid. Knowledge of the morphologic and attenuation characteristics of common colonic lesions and artifacts can help identify bulbous haustral folds, impacted diverticula, an inverted appendiceal stump, or mobile polyps, any of which may pose problems for the radiologist. A combined two-dimensional and three-dimensional imaging approach is recommended for each colonic finding. A thorough knowledge of the various pitfalls and pseudolesions that may be encountered at CT colonography, along with use of dedicated problem-solving techniques, will help the radiologist differentiate between definite colonic lesions and pseudolesions.

CT colonography: techniques, indications, findings

Computed tomographic colonography (CTC) is a minimally invasive technique for imaging the entire colon. Based on a helical thin-section CT of the cleansed and air-distended colon, two-dimensional and three-dimensional projections are used for image interpretation. Several clinical improvements in patient preparation, technical advances in CT, and new developments in evaluation software have allowed CTC to develop into a powerful diagnostic tool. It is already well established as a reliable diagnostic tool in symptomatic patients. Many experts currently consider CTC a comparable alternative to conventional colonoscopy, although there is still debate about its sensitivity for the detection of colonic polyps in a screening population. This article summarizes the main indications, the current techniques in patient preparation, data acquisition and data analysis as well as imaging features for common benign and malignant colorectal lesions.

Update on Colorectal Cancer Imaging

Colorectal cancer remains a leading cancer killer worldwide. The disease is both curable and preventable, and yet the importance of widespread screening is only now starting to be appreciated. This article reviews the variety of diagnostic tests, imaging procedures and endoscopic examinations available to detect colorectal cancer and polyps in their early stage and also presents details on various screening options. The critical role of the radiologist is elaborated on including accurate assessment of the tumor extent within the bowel wall and beyond and the detection of lymph node and distant metastases. Staging with CT, MR imaging, endorectal ultrasound, and positron emission tomography are of paramount importance in determining the most appropriate therapy and the risk of tumor recurrence and overall prognosis.

Assessment of polyp and mass histopathology by intravenous contrast-enhanced CT colonography

RATIONALE AND OBJECTIVES

We sought to demonstrate that intravenous contrast-enhanced CT colonography (CTC) can distinguish colonic adenomas from carcinomas.

METHODS

Supine intravenous contrast-enhanced CTC with colonoscopic and/or surgical correlation was performed on 25 patients with colonic adenomas or carcinomas. Standard deviation of mean polyp CT attenuation was computed and assessed using ANOVA and receiver-operating characteristic analyses.

RESULTS

Colonoscopy confirmed 32 polyps or masses 1 to 8 cm in size. The standard deviations of CT attenuation were carcinomas (n = 13; 36 +/- 6 HU; range 28-48 HU) and adenomas (n = 19; 49 +/- 14 HU; range 31-100 HU) (P = 0.005). At a standard deviation threshold of 42 HU, the sensitivity and specificity for classifying a polyp or mass as a carcinoma were 92% and 79%, respectively. The area under the receiver-operating characteristic curve was 0.89 +/- 0.06 (95% confidence interval 0.73-0.96).

CONCLUSIONS

Measurement of the standard deviation of CT attenuation on intravenous contrast-enhanced CTC permits histopathologic classification of polyps 1 cm or larger as carcinomas versus adenomas. The presence of ulceration or absence of muscular invasion in carcinomas creates overlap with adenomas, reducing the specificity of carcinoma classification.

Abdominal Sacral Resection for Posterior Pelvic Recurrence of Rectal Carcinoma: Analyses of Prognostic Factors and Recurrence Patterns

BACKGROUND

Local recurrence of rectal cancer presents challenging problems. Although abdominal sacral resection (ASR) provides pain control, survival prolongation, and possibly cure, reported morbidity and mortality are still high, and survival is still low. Thus, appropriate patient selection and adjuvant therapy based on prognostic factors and recurrence patterns are necessary. The purpose of this study was to evaluate the results of ASR for posterior pelvic recurrence of rectal carcinoma and to analyze prognostic factors and recurrence patterns.

METHODS

Forty-four patients underwent ASR for curative intent in 40 and palliative intent in 4 cases. All but one could be followed up completely. Multivariate analyses of factors influencing survival and positive surgical margins were conducted.

RESULTS

Morbidity and mortality were 61% and 2%, respectively. Overall 5-year survival was 34%. The Cox regression model revealed a positive resection margin (hazard ratio, 10 [95% confidence interval, 3.8-28]), a local disease-free interval of <12 months (4.2 [1.8-9.8]), and pain radiating to the buttock or further (4.2 [1.6-11]) to be independently associated with poor survival. The logistic regression model showed that macroscopic multiple expanding or diffuse infiltrating growths were independently associated with a positive margin (7.5 [1.4-40]). Of the patients with recurrence, 56% had failures confined locally or to the lung.

CONCLUSIONS

ASR is beneficial to selected patients in terms of survival. To select patients, evaluation of the resection margin, the local disease-free interval, pain extent, and macroscopic growth pattern is important. To improve survival, adjuvant treatment should be aimed at local and lung recurrences.

CT colonography: surveillance in patients with a history of colorectal cancer

Colorectal cancer is a leading cause of morbidity and mortality in the United States. It is also a disease that is preventable if precursor adenomatous polys are removed. Once a diagnosis of colorectal cancer is made, surgical resection is the only means of cure. The ability to resect colorectal cancer for cure is largely dependent upon the stage of tumor at presentation. Once a patient has been treated for colorectal cancer with surgery and in some cases neo-adjuvant or adjuvant therapy, they will present for follow-up. Surveillance is performed on these patients in order to detect local recurrence that if detected early can be surgically resected for cure. Surveillance also allows detection of distant metastatic disease that may in some cases also be cured with resection. Finally, surveillance of the remaining colon is important to detect the development of new or metachronous adenomatoid polyps that if left in place could develop into new colon cancers. Imaging can play a part in patient surveillance to detect recurrent disease at extracolonic sites as well as the development of new colonic lesions. CT colonography is a promising tool for surveillance in patients with a history of colorectal cancer.

Evaluation of benign and malignant rectal lesions with CT colonography and endoscopic correlation

Colorectal carcinoma is a significant cause of death from cancer in the United States, and early detection and treatment are critical. Computed tomographic (CT) colonography is a noninvasive, rapidly evolving technique that is a potential alternative to conventional colonoscopy for colorectal cancer screening. Rectal disease (eg, polyps, cancerous lesions, extramucosal lesions, inflammatory disease) can be especially challenging to diagnose with CT colonography because of several factors that can simulate or obscure the disease (eg, over- or underdistention, rectal tube, stool, artifacts). Familiarity with the spectrum of rectal diseases and with the potential pitfalls and technical limitations of CT colonography will help minimize interpretative and perceptual errors.

CT colonography with intravenous contrast material: varied appearances of colorectal carcinoma

Computed tomographic (CT) colonography is a noninvasive, rapidly evolving technique that has been shown in some studies to be comparable with conventional colonoscopy for the screening of colorectal cancer. Because colorectal cancer has a widely varying appearance at both endoscopy and CT colonography, familiarity with the gamut of morphologic appearances can help improve interpretation of the results. The addition of intravenous contrast material to CT colonography can aid differentiation of true colonic masses from pseudolesions such as residual stool and improves the depiction of enhancing masses that might otherwise be obscured by residual colonic fluid. In contrast to staging of most other tumors, staging of colorectal carcinoma depends more on the depth of tumor invasion than on the size of the primary mass. The diverse appearances of colorectal cancers at two- and three-dimensional CT colonography include sessile, annular, ulcerated, necrotic, mucinous, invasive, and noninvasive lesions. Imaging pitfalls that can simulate or obscure neoplasms are retained fecal material or fluid, incomplete distention, and advanced diverticulosis.

Rectal perforations after barium enema: a review

PURPOSE

Rectal injuries during barium enema are rare but life-threatening complications. The last review about this subject was published more than ten years ago. In the present review, we present an overview on the subject and especially focus on changes in treatment strategies and developments of less risky visualization techniques.

METHODS

A literature search was performed in the PubMed library using the key words-barium enema, complications, peritonitis, and rectal perforation-as well as related articles and other references obtained from these articles.

RESULTS

The most frequent cause of perforation is iatrogenic and catheter-related. Other causes are related to weakness of the colorectal wall or obstruction. Five types of perforations have been described: 1) perforations of the anal canal below the levator; 2) incomplete perforations; 3) perforations into the retroperitoneum; 4) transmural perforations into adjacent viscera; 5) perforations into the free intraperitoneal cavity. Most incomplete perforations and one-half of the retroperitoneal perforations have minimal clinical signs. Intraperitoneal perforations lead to the most catastrophic course, starting with rectal bleeding and mild abdominal complaints. This is rapidly followed by progressive sepsis and peritonitis, and leads to a high mortality rate. Surgery is not always required for intramural or small retroperitoneal perforations. These can be treated conservatively and require surgical debridement only in case of large amounts of extravasation or abscesses. Surgical repair of large rectal mucosal lesions or anal sphincter lesions is advised. Perirectal abscesses require drainage. Intraperitoneal perforations with gross extravasation need immediate aggressive surgical treatment in a critical care setting, because the threat of shock is high. Intraperitoneal perforations, neglected perforations, gross barium extravasation, poorly prepared colon, and venous intravasation of barium are prognostically unfavorable. The severest late complication in intraperitoneal perforations is ileus. Meticulous technical performance of the barium enema is the most important factor in prevention.

CONCLUSIONS

Rectal perforations after barium enema are rare. The overall mortality rate decreased in recent decades from approximately 50 to 35 percent as the result of advances in supportive and intensive care. Because of these advances, more aggressive surgical strategies were undertaken. With the advent of endoscopy, less barium enemas are performed. Consequently, the absolute incidence of complications has decreased. It is expected that in the future barium enemas will be replaced by more sensitive and less risky techniques, such as CT colonography and magnetic resonance colonography.

Evaluation of contrast-enhanced computed tomographic colonography in detection of local recurrent colorectal cancer

AIM: To evaluate the diagnostic accuracy, sensitivity, specificity of contrast-enhanced computed tomographic colonography in detecting local recurrence of colorectal cancer.

METHODS: From January 2000 to December 2004, 434 patients after potentially curative resection for invasive colorectal cancer were followed up for a period ranging from 20 to 55 mo. Eighty of the four hundred and thirty-four patients showing strong clinical evidence for recurring colorectal cancer during the last follow-up were enrolled in this study. Each patient underwent contrast-enhanced computed tomographic colonography and colonoscopy on the same day. Any lesions, biopsies, identified during the colonoscopic examination, immediate complications and the duration of the procedure were recorded. The results of contrast-enhanced computed tomographic colonography were evaluated by comparing to those of colonoscopy, surgical finding, and clinical follow-up.

RESULTS: Contrast-enhanced computed tomographic colonography had a sensitivity of 100%, a specificity of 83% and an overall accuracy of 94% in detecting local recurrent colorectal cancer.

CONCLUSION: Conventional colonoscopy and contrast-enhanced tomographic colonography can complement each other in detecting local recurrence of colorectal cancer.

Whole body positron emission tomography/computed tomography (PET/CT) tumour staging with integrated PET/CT colonography: technical feasibility and first experiences in patients with colorectal cancer

AIM

The aim of this study was to implement an imaging protocol for positron emission tomography/computed tomography (PET/CT) colonography and to combine this protocol with whole body PET/CT tumour staging for a single whole body examination for routine clinical use.

SUBJECTS AND METHODS

A whole body PET/CT protocol for tumour staging and a protocol for PET/CT colonography were integrated into one examination. Fourteen prospective patients with suspected colorectal cancer underwent whole body PET/CT after aqueous bowel distension and pharmacological bowel relaxation. Colonoscopy and histopathology served as the standards of reference in all patients.

RESULTS

The modified PET/CT examination detected all but one lesion in the colon. One additional lesion was detected in a patient with incomplete colonoscopy due to high grade luminal stenosis. One polyp with malignant conversion was identified with the modified PET/CT protocol. PET/CT colonography proved accurate in local lymph node staging and staged nine out of 11 patients correctly. Six additional extracolonic tumour sites were detected based on the whole body staging approach.

CONCLUSION

Whole body PET/CT with integrated colonography is technically feasible for whole body staging in patients with colorectal cancer. Based on these initial diagnostic experiences, this integrated protocol may be of substantial benefit in staging patients with colorectal cancer, focusing on patients with incomplete colonoscopy and those with small synchronous bowel lesions.

Computed tomography differentiation of benign and malignant gastric wall thickness

AIM: To determine the sensitivity and specificity of the computed tomography (CT) for differentiating benign and malignant thickness of the gastric wall.

METHODS: The data were collected from 40 patients with gastric wall thickness determined by spiral CT examination, who underwent barium meal examination within 4 wk before or after the CT examination. The CT images were reviewed to determine the degree of the gastric wall thickeness and the symmetry, distribution, and enhancement of the thickened wall. The sensitivity and specificity of CT in detecting the malignant tumor were calculated through the above features.

RESULTS: Of the 40 cases, 20 were with gastritis, 4 with hiatal hernia, 3 with benign ulcer, 3 with benign gastric neoplasm, 8 with malignant neoplasm, and 2 with no abnormality. The mean thickness of the gastric wall was 14 mm (7-65 mm). All the gastric walls with thickness ≥10 mm were diagnosed as malignancy by CT, and the sensitivity rate was 100%, but the specificity rate was 43%. The sensitivity rate for focal, eccentric, and enhanced gastric wall thickness was 93%, 71%, and 43%, and the specificity rate was 8%, 75%, and 88%, respectively. Generally, the sensitivity for detecting 10 mm- or more than 10 mm-thick gastric walls, which were focal, eccentric, and enhanced, was 36%, but the specificity was 93%.

CONCLUSION: After a comprehensive consideration of focal, eccentric, and enhancing thickness, the specificity rate of CT can be greatly increased, so further examination should be performed in the near future.

Multislice CT Colonography: Current Status and Limitations

CT colonography (CTC) is a promising method for colorectal cancer screening because it provides a full structural evaluation of the entire colon. It has a superior safety profile, a low rate of complications, and high patient acceptance. In addition, CTC offers the real possibility of eliminating the cathartic bowel preparation, one of the biggest obstacles to patient compliance with colorectal cancer screening. Results of CTC studies in recently published literature are extremely encouraging, demonstrating that this method of screening can detect lesions equal to or larger than 8 mm with few false-positive findings.

CT colonography with fecal tagging after incomplete colonoscopy

The objective of this study was to evaluate dietary fecal tagging (FT) as a cleansing method prior to CT colonography (CTC) in patients with incomplete conventional colonoscopy (CC). After written informed consent was obtained, 24 patients had standard colonoscopic preparation (ScCl), and 25 patients had FT as cleansing method. Segmental distention, fluid levels, fecal residues, tagged appearance of fluid levels, and residual stool were evaluated. Mann-Whitney U test was used to test for significant differences between FT and ScCl groups. Compared with ScCl, FT improved distention (p=0.001), reduced the amount of fluid (p=0.043), but suffered from residual stool (p=0.046). A clear correlation was found between distention and fluid. No differences were found in stool size between FT and ScCl. FT showed a good labeling of fecal residues, and acceptable labeling of fluid levels. Compared with ScCl, FT reduces fluid, favors distention, but suffers from fecal residues. The tagged nature of these residues, however, allows differentiation from polyps.

Virtual colonoscopy: Issues in implementation

The following issues and requirements related to the implementation of a CT colonography (CTC) service are important: (i) policies are needed regarding the indications for CTC. Concomitant with this is the need for education of potential referrers and patients. Expectations of the procedure, particularly by general practitioners, may be unrealistic and indications for referral may otherwise be inappropriate. At present there is not general acceptance of CTC for screening asymptomatic persons; (ii) a flexible approach to CT protocols is useful, dependent on the indication for and clinical context of referral, the age and body habitus of the patient; (iii) attention to the issues related to the special skills required by the reporting radiologist. While there is a temptation to regard CTC interpretation as an extension of skills used in interpreting other cross-sectional images, there is a need to realise that there are skills required specific to CTC and there should be adequate provision for training; (iv) matters related to reporting, such as reporting format, and lesions that will be reported/not reported; and (v) informed consent from the patient. Information should be provided with regard to the limitations of CTC, the implications of a positive finding and radiation dosage.

Computed Tomographic Colonography (CTC): Possibilities and Limitations of Clinical Application in Colorectal Polyps and Cancer

Colorectal cancer is the second leading cause of cancer-related deaths in Europe and the United States. Most colorectal cancers develop from adenomatous polyps over a number of years. Early detection of polyps eliminates the risk of subsequent carcinomas.

Computed tomographic (CT) colonography is a diagnostic technique detecting colorectal neoplasms. With the introduction of multidetector-row computed tomography (MD-CT), CT colonography (CTC) has gained influence as a new diagnostic tool in early detection of colonic pathologies by acquiring volumetric CT data sets of the abdomen. This volumetric data is analyzed using CTC workstations, which provide an interactive display of 2D and 3D images of the colon. In several studies, CTC revealed a high accuracy (sensitivity/patient: 83–100% and specificity/patient: 93–100%) in detecting pathological colonic changes. Furthermore, CTC is an excellent diagnostic technique for the evaluation of patients with incomplete conventional colonoscopy and allows the assessment of extracolonic abdominal and pelvic organs.

In this article, the status of CT colonography as a method of detecting colonic polyps and colorectal carcinomas using single- and multidetector-row CT will be reviewed.