CT colonography: pitfalls in interpretation

Comparison of MiraLAX and magnesium citrate for bowel preparation at CT colonography

PURPOSE

To compare MiraLAX, a hypo-osmotic lavage, and magnesium citrate (MgC), a hyper-osmotic agent for bowel preparation at CTC.

METHODS

398 total screening CTC studies were included in this retrospective, single institution study. 297 underwent preparation with a double-dose MgC regimen (mean age, 61 ± 5.5 years; 142 male/155 female) and 101 with 8.3 oz (equivalent to 238 g PEG) of MiraLAX (mean age, 60 ± 9.6 years; 45 male/56 female). Oral contrast for tagging purposes was utilized in both regimens. Studies were retrospectively analyzed for residual fluid volume and attenuation by automated analysis, as well for subjective oral contrast coating of the normal colonic wall and polyps. 50 patients underwent successive CTC studies utilizing each agent (mean, 6.1 ± 1.7 years apart), allowing for intra-patient comparison. Chi-squared, Fisher's exact, McNemar, and t-tests were used for data comparison.

RESULTS

Residual fluid volume (as percentage of total colonic volume) and fluid density was 7.2 ± 4.2% and 713 ± 183 HU for the MgC cohort and 8.7 ± 3.8% and 1044 HU ± 274 for the MiraLAX cohort, respectively (p = 0.001 and p < 0.001, respectively). Similar results were observed for the intra-patient cohort. Colonic wall coating negatively influencing interpretation was noted in 1.7% of MgC vs. 6.9% of MiraLAX examinations (p = 0.008). Polyps were detected in 12% of all MgC vs. 16% of all MiraLAX CTCs (p = 0.29).

CONCLUSION

CTC bowel preparation with the hypo-osmotic MiraLAX agent appears to provide acceptable diagnostic quality that is comparable to the hyper-osmotic MgC agent, especially when factoring in patient safety and tolerance.

Feasibility of Simple Oral Preparation Contrast-Enhanced CT Colonography (SOP-CE-CTC) Using Mannitol as a Neutral Oral Contrast Agent

Purpose This article prospectively assesses the feasibility of simple oral preparation contrast-enhanced computed tomography colonography (SOP-CE-CTC) using a large volume of oral 3% mannitol for good colonic distension along with mural and mucosal fold visualization.

Methods A total of 100 patients in whom contrast CT abdomen was requested, recruited as per selection criteria, were advised to take mild oral bowel preparation for two nights, prior to the investigation. Then, after fasting overnight, they were asked to consume 1,500 to 2,000 mL of 3% mannitol solution in about an hour. Thirty minutes after completing the ingestion of oral mannitol, intravenous contrast was injected and SOP-CE-CTC was acquired at 55 seconds. Distension of six segments of the colon was evaluated by assigning scores 1 to 4 for qualitative assessment; and measuring the maximum luminal diameter of the colon, for quantitative assessment. Colonic mucosal and mural visualization were evaluated subjectively. All observations were recorded by two reviewers (with varying levels of experience) independently.

Results On qualitative analysis, the colon showed optimal distension (score 4) in 58 to 89% cases on SOP-CE-CTC. There was agreement between both the reviewers in 89 to 99% cases (weighted kappa 0.820–0.979; p < 0.001). On quantitative analysis, the mean of the maximum colonic diameter ranged between 3.4 and 5.2 cm; and both the reviewers agreed in 89 to 97% cases (weighted kappa 0.777–0.967; p < 0.001). Mural and mucosal fold visualization in the proximal four segments of the colon was excellent (in 90–98%) but in the rectum and sigmoid it was 45 and 66%, respectively; both the reviewers agreed in 100% cases (weighted kappa 1.0 and p < 0.001).

Conclusion Good colonic distension, mural, and mucosal fold visualization can be achieved on SOP-CE-CTC using 1,500 to 2,000 mL of 3% oral mannitol and mild oral bowel preparation agents.

Role of CT colonography in differentiating sigmoid cancer from chronic diverticular disease

PURPOSE

To evaluate the accuracy of computed tomography colonography (CTC) in differentiating chronic diverticular disease from colorectal cancer (CRC), using morphological and textural parameters.

MATERIALS AND METHODS

We included 95 consecutive patients with histologically proven chronic diverticular disease (n = 53) or CRC (n = 42) who underwent CTC. One radiologist, unaware of histological findings, evaluated CTC studies for the presence of potential discriminators including: maximum thickness, involved segment length, shouldering phenomenon, growth pattern, diverticula, fascia thickening, fat tissue edema, loco-regional lymph nodes, mucosal pattern. Another radiologist performed volumetric texture analysis on the involved segment.

RESULTS

Several qualitative imaging parameters resulted to significantly correlated with colorectal cancer, including absence of diverticula in the affected segment, straightened growth pattern and shouldering phenomenon. A maximum wall thickness/involved segment length ratio < 0.1 had 98% specificity and 47% sensitivity in identifying diverticular disease. Regarding first-order texture analysis parameters, kurtosis resulted to be significantly different between the two groups.

CONCLUSIONS

Absence of diverticula, straightened growth pattern and shouldering phenomenon are significantly associated with CRC (71-91% sensitivity; 82-91%).

Meeting the new joint British Society of Gastrointestinal and Abdominal Radiology and Royal College of Radiologists CT colonography standards: a 6-year experience

AIM

To audit the performance of computed tomography colonography (CTC) at St Mark's Hospital against the joint British Society of Gastrointestinal and Abdominal Radiology (BSGAR) and Royal College of Radiologists (RCR) standards.

MATERIALS AND METHODS

A retrospective audit of all CTC studies between January 2012 to December 2017 was performed against the BSGAR/RCR standards along with additional data outwith the guidelines. Evidence was obtained from a central database, radiology information systems (RISs), picture archiving and communication systems (PACSs), and electronic patient records (EPRs).

RESULTS

Over the 6 years, 13,143 CTCs were performed and 12,996 (99%) were adequate or better. Of the cases 1,867 had a >6 mm polyp or cancer reported (polyp identification rate [PIR] 14%) and the positive predictive value (PPV) was 93% (1,148/1,240). Median radiation dose was 458 mGy·cm, mean additional acquisition rate was 19% (2,505/13,143), subsequent endoscopy rate was 9% (1,222/13,143) and mean interpretation time for a negative study was 34.6 minutes. Nine perforations occurred (perforation rate of 0.068%) and one was symptomatic (symptomatic perforation rate of 0.008%). For suspected cancers, the same-day endoscopy rate was 27% (96/360) and same-day staging rate was 76% (272/360). Post-imaging colorectal cancer rates (PICRC) was 3.06 per 100 cancers detected and 0.23 per 1,000 CTCs. The service was always rated "good" or higher by patients.

CONCLUSION

This audit shows the CTC service at St Mark's Hospital to be safe and of sufficiently high quality to meet the BSGAR/RCR standards with most outcomes equal to or above the aspirational target. Areas for service and individual reader improvement were also identified.

CT Colonography: Improving Interpretive Skill by Avoiding Pitfalls

An earlier incorrect version of this article appeared online. This article was corrected on December 20, 2019.

Immersive Virtual Colonoscopy

Virtual colonoscopy (VC) is a non-invasive screening tool for colorectal polyps which employs volume visualization of a colon model reconstructed from a CT scan of the patient's abdomen. We present an immersive analytics system for VC which enhances and improves the traditional desktop VC through the use of VR technologies. Our system, using a head-mounted display (HMD), includes all of the standard VC features, such as the volume rendered endoluminal fly-through, measurement tool, bookmark modes, electronic biopsy, and slice views. The use of VR immersion, stereo, and wider field of view and field of regard has a positive effect on polyp search and analysis tasks in our immersive VC system, a volumetric-based immersive analytics application. Navigation includes enhanced automatic speed and direction controls, based on the user's head orientation, in conjunction with physical navigation for exploration of local proximity. In order to accommodate the resolution and frame rate requirements for HMDs, new rendering techniques have been developed, including mesh-assisted volume raycasting and a novel lighting paradigm. Feedback and further suggestions from expert radiologists show the promise of our system for immersive analysis for VC and encourage new avenues for exploring the use of VR in visualization systems for medical diagnosis.

Imaging of colorectal cancer - the clue to individualized treatment

Colorectal cancer (CRC) is the most common gastrointestinal neoplasm and the second most common cause for cancer-related death in Europe. Imaging plays an important role both in the primary diagnosis, treatment evaluation, follow-up, and, to some extent, also in prevention. Like in the clinical setting, colon and rectal cancer have to be distinguished as two quite separate entities with different goals of imaging and, consequently, also different technical requirements. Over the past decade, there have been improvements in both more robust imaging techniques and new data and guidelines that help to use the optimal imaging modality for each scenario. For colon cancer, the continued research on computed tomography (CT) colonography (CTC) has led to high-level evidence that puts this technique on eye height to optical colonoscopy in terms of detection of cancer and polyps ≥10 mm. However, also for smaller polyps and thus for screening purposes, CTC seems to be an optimal tool. In rectal cancer, the technical requirements to perform state-of-the art imaging have recently been defined. Evaluation of T-stage, mesorectal fascia infiltration and extramural vascular invasion are the most important prognostic factors that can be identified on MRI. With this information, risk stratification both for local and distal failure is possible, enabling the clinician to tailor the optimal therapeutic approach in non-metastatic rectal cancer. Imaging of metastatic CRC is also covered, although the complex ramifications of treatment options in the metastatic setting are beyond the scope of this article. In this review, the most important recent developments in the imaging of colon and rectal cancer will be highlighted. If used in an interdisciplinary setting, this can lead to an individualized treatment concept for each patient.

CT colonography interpretation: how to maximize polyp detection and minimize overcalling

This article outlines how to achieve maximum accuracy in interpreting CT colonography (CTC) regarding colonic findings. Interpreting extracolonic findings seen on CTC is a separate diagnostic task and will not be addressed in this article. While many interpretive pitfalls are in fact related to CTC techniques, this article focuses on issues that are related to interpretive knowledge and skills, avoiding in-depth discussions on CTC techniques. Principal methods and further tips for detecting possible polyp candidates and for confirming true soft-tissue polyps will be discussed. Specific points about optimizing interpretation strategies for difficult flat polyps including sessile serrated polyp will be raised. There are numerous interpretive pitfalls regarding the colonic interpretation of CTC. Knowledge of these pitfalls will shorten the learning curve and help achieve accurate reads.

TC Rectal Pathology: Findings at CT-Colonography

OBJECTIVE

To review the spectrum of benign and malignant rectal diseases, their findings on CT colonography, and their management.

CONCLUSION

Although CT colonography is not the first choice for the study of rectal disease, it is indicated in cases where optical colonoscopy is contraindicated or cannot be completed. Rectal lesions can go undetected because this anatomic area is difficult to evaluate; for this reason, it is essential to ensure optimal preparation and distension, moderate balloon insufflation, and careful 2D and 3D navigation with knowledge of the spectrum of rectal disease and its CT colonography signs.

Flat Serrated Polyps at CT Colonography: Relevance, Appearance, and Optimizing Interpretation

Serrated polyps are a recently recognized family of colonic polyps with subgroups that harbor future malignant potential. In the past, the significance of these lesions to the colorectal cancer carcinogenesis pathway was not recognized nor well understood. It is now known that serrated polyps account for approximately one-fourth of all sporadic colorectal cancers. The sessile serrated polyp (SSP) (also known as a sessile serrated adenoma [SSA]) is the main lesion of interest given its prevalence and subtle presentation. These lesions are often flat-only minimally raised from the colonic surface-and occur in the right colon. These lesions have been a likely common cause of screening failure at colonoscopy, although detection has improved with improved recognition over time. Although detection is difficult with image-based screening, serrated lesions can be detected at CT colonography. The prevalence in CT colonography screening populations mirrors the rates at colonoscopy for similar size categories. CT colonography allows identification of SSPs despite their minimally raised profile owing to the phenomenon of lesional contrast material coating. This contrast material coat aids in lesion detection by highlighting the subtle morphologic changes as well as increasing confidence that a true lesion exists despite a flat morphology. It is important to optimize contrast material coating with specific bowel preparations and other technical parameters. Radiologists should be aware of these technical and interpretation issues. Armed with this knowledge, radiologists should expect excellent results in detection of these subtle but important lesions. ^©RSNA, 2017.

Potential pitfalls in the anorectal region during CT colonography: A discussion and pictorial overview of common pitfalls

Common potential anorectal pitfalls are presented with accompanying CT colonography images. Although most lesions are benign, care must be taken in not missing an underlying cancer.

Prevalence and risk factors for post-investigation colorectal cancer ("interval cancer") after computed tomographic colonography: protocol for a systematic review

BACKGROUND

Colorectal cancer (CRC) is a common and important disease. There are different tests for diagnosis, one of which is computed tomographic colonography (CTC). No test is perfect, and patients with normal CTC may subsequently develop CRC (either because it was overlooked originally, or because it has developed in the interim). This is termed post-investigation colorectal cancer (PICRC) or "interval cancer". How frequently this occurs after CTC is not known. The purpose of this systematic review and meta-analysis is to use the primary literature to estimate the PICRC rate after CTC, and explore associated factors.

METHODS

Primary studies reporting post-investigation colorectal cancer (PICRC) rates after CTC will be identified from PubMed, Embase and Cochrane Register of Controlled Trials databases. Peer-reviewed studies published after 1994 (the year CTC was introduced) will be included and the rate of PICRC within 36 months of CTC recorded. Data will be extracted from selected studies for a random effects meta-analysis. Heterogeneity, risk of bias and publication bias will be assessed, and exploratory analysis will examine factors associated with higher PICRC rates in the literature.

CONCLUSION

PICRC rates are the ultimate benchmark of diagnostic quality for colonic investigations. This systematic review and meta-analysis will identify and synthesise evidence to determine PICRC rates after CTC and explore factors that may contribute to higher rates.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (registration number CRD42016042437 ).

Computed Tomography Colonography Phantom: Construction, Validation and Literature Review

Background

Several dedicated computed tomography (CT) colonography phantoms have been described previously.

Objectives

To compare their pros and cons and describe the construction of a dedicated phantom that can be easily manufactured.

Materials and 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.

Conclusion

We constructed and validated a CT colonography phantom with correct density allowing performance of reproducible experiments.

Diagnostic value of computed tomography colonography (CTC) after incomplete optical colonoscopy

INTRODUCTION

This study evaluated the role of computed tomography colonography (CTC) in patients who previously underwent incomplete optical colonoscopy (OC). We analyzed the impact of colonic lesions in intestinal segments not studied by OC and extracolonic findings in these patients.

METHODS

Between January 2014 and May 2015, 61 patients with a history of abdominal pain and incomplete OC examination were studied by CTC. CTCs were performed by 320-row CT scan in both the supine and the prone position, without intravenous administration of contrast medium. In all patients both colonic findings and extracolonic findings were evaluated.

RESULTS

Among the study group, 24 CTC examinations were negative for both colonic and extracolonic findings while 6 examinations revealed the presence of both colonic and extracolonic findings. In 24 patients CTC depicted colonic anomalies without extracolonic ones, while in 7 patients it showed extracolonic findings without colonic ones.

DISCUSSION

CTC is a noninvasive imaging technique with the advantages of high diagnostic performance, rapid data acquisition, minimal patient discomfort, lack of need for sedation, and virtually no recovery time. CTC accurately allows the evaluation of the nonvisualized part of the colon after incomplete OC and has the distinct advantage to detect clinically important extracolonic findings in patients with incomplete OC potentially explaining the patient's symptoms and conditioning their therapeutic management.

CONCLUSION

CTC accurately allows the assessment of both colonic and extracolonic pathologies representing a useful diagnostic tool in patients for whom complete OC is not achievable.

Sub-milliSievert ultralow-dose CT colonography with iterative model reconstruction technique

Purpose. The purpose of this study was to evaluate the technical and diagnostic performance of sub-milliSievert ultralow-dose (ULD) CT colonograpy (CTC) in the detection of colonic and extracolonic lesions.

Materials and Methods. CTC with standard dose (SD) and ULD acquisitions of 64 matched patients, half of them with colonic findings, were reconstructed with filtered back projection (FBP), hybrid (HIR) and iterative model reconstruction techniques (IMR). Image noise in six colonic segments, in the left psoas muscle and aorta were measured. Image quality of the left adrenal gland and of the colon in the endoscopic and 2D view was rated on a five point Likert scale by two observers, who also completed the reading of CTC for colonic and extracolonic findings.

Results. The mean radiation dose estimate was 4.1 ± 1.4 mSv for SD and 0.86 ± 0.17 mSv for ULD for both positions (p < 0.0001). In ULD-IMR, SD-IMR and SD-HIR, the endoluminal noise was decreased in all colonic segments compared to SD-FBP (p < 0.001). There were 27 small (6–9 mm) and 17 large (≥10 mm) colonic lesions that were classified as sessile polyps (n = 38), flat lesions (n = 3), or as a mass (n = 3). Per patient sensitivity and specificity were 0.82 and 0.93 for ULD-FBP, 0.97 and 0.97 for ULD-HIR, 0.97 and 1.0 for ULD-IMR. Per polyp sensitivity was 0.84 for ULD-FBP, 0.98 for ULD-HIR, 0.98 for ULD-IMR. Significantly less extracolonic findings were detected in ULD-FBP and ULD-HIR, but in the E4 category by C-RADS (potentially important findings), the detection was similar.

Conclusion. Both HIR and IMR are suitable for sub-milliSievert ULD CTC without sacrificing diagnostic performance of the study.

CT colonography after incomplete optical colonoscopy: bowel preparation quality at same-day vs. deferred examination

PURPOSE

To objectively compare the volume, density, and distribution of luminal fluid for same-day oral-contrast-enhanced CTC following incomplete optical colonoscopy (OC) vs. deferred CTC on a separate day utilizing a dedicated CTC bowel preparation.

METHODS

HIPAA-compliant, IRB-approved retrospective study compared 103 same-day CTC studies after incomplete OC (utilizing 30 mL oral diatrizoate) against 151 CTC examinations performed on a separate day after failed OC using a dedicated CTC bowel preparation (oral magnesium citrate/dilute barium/diatrizoate the evening before). A subgroup of 15 patients who had both same-day CTC and separate-day routine CTC was also identified and underwent separate analysis. CTC exams were analyzed for opacified fluid distribution within the GI tract, as well as density and volume. Data were analyzed utilizing Kruskal-Wallis and Wilcoxon Signed Rank tests.

RESULTS

Opacified luminal fluid extended to the rectum in 56% (58/103) of same-day CTC vs. 100% (151/151) of deferred separate-day CTC (p < 0.0001). For same-day CTC, contrast failed to reach the colon in 11% (11/103) and failed to reach the left colon in 26% (27/103). Volumetric colonic fluid segmentation for fluid analysis (successful in 80 same-day and 147 separate-day cases) showed significantly more fluid in the same-day cohort (mean, 227 vs. 166 mL; p < 0.0001); the actual difference is underestimated due to excluded cases. Mean colonic fluid attenuation was significantly lower in the same-day cohort (545 vs. 735 HU; p < 0.0001). Similar findings were identified in the smaller cohort with direct intra-patient CTC comparison.

CONCLUSIONS

Dedicated CTC bowel preparation on a separate day following incomplete OC results in a much higher quality examination compared with same-day CTC.

Automated volumetric analysis for comparison of oral sulfate solution (SUPREP) with established cathartic agents at CT colonography

PURPOSE

To objectively compare residual colonic fluid volume and attenuation of oral sulfate solution (OSS) with four different established cathartic regimens using an automated volumetric software tool at CT colonography (CTC).

METHODS

This HIPAA-compliant study had institutional review board approval. Volumetric analysis of residual contrast-tagged colonic fluid was performed on CTC studies in 263 adults (mean age 60.1 years; 137M/126F) using an automated volumetric software tool. Twenty-three patients receiving 177 mL OSS (SUPREP; single-bottle purgation) were compared with 60 patients each receiving 45 mL sodium phosphate (NaP), 90 mL NaP (2× NaP), 592 mL (two bottles) magnesium citrate (MgC), and 4,000 mL polyethylene glycol (PEG). All patients received oral contrast cleansing after catharsis. Data were analyzed with unpaired t test with Welch correction and F test.

RESULTS

The mean volume of residual colonic fluid was less with OSS (125 ± 60 mL) than for established cathartic agents: 2× NaP (206 ± 125 mL, P < 0.0001), MgC (184 ± 125 mL, P < 0.01), PEG (166 ± 114 mL, P < 0.05), and NaP (165 ± 135 mL, P = 0.067). Variance of volumes was also significantly lower for OSS (range 28-251 mL) than for established agents (range 4-853 mL) (all P < 0.01). Mean fluid attenuation was higher with OSS (956 ± 168 HU) than for established agents (all P < 0.05): 2× NaP (455 ± 191 HU), MgC (691 ± 154 HU), NaP (779 ± 127 HU), and PEG (843 ± 193 HU).

CONCLUSIONS

Automated volumetry allows rapid objective assessment of bowel preparation quality at CTC. Purgation with the novel oral sulfate solution (SUPREP) consistently resulted in less residual colonic fluid and higher fluid attenuation compared with established cathartic regimens.

Volumetric analysis of colonic distention according to patient position at CT colonography: diagnostic value of the right lateral decubitus series

OBJECTIVE

The purpose of this study was to compare total colonic gas volume and segmental luminal distention according to patient position on CT colonography (CTC), as well as to determine which two views should constitute the routine protocol.

MATERIALS AND METHODS

Volumetric analysis was retrospectively performed on CTC examinations from 146 adults (mean age, 59.2 years; 81 men and 65 women; mean body mass index [BMI], 30.9) for whom supine, prone, and right lateral decubitus series were sequentially obtained using continuous low-pressure CO2 insufflation. Total colonic gas volumes were assessed using a novel automated volumetric tool. In addition, two radiologists scored distention by segment using a 4-point scale (4=optimal; 3=adequate; 2=inadequate; 1=collapsed).

RESULTS

Mean (±SD) colonic gas volumes for supine, prone, and decubitus positioning were 1617±567, 1441±505, and 1901±627, respectively (p<0.001). Colonic volume was highest on the right lateral decubitus series in 73.3% (107/146) and lowest in 6.2% (9/146) of cases, whereas the prone series was highest in 0.7% (1/146) and lowest in 73.3% (107/146) of cases. Overall mean segmental reader scores and percentages of inadequate or collapsed for supine, prone, and decubitus positions were 3.48, 3.33, and 3.71 and 10.4%, 12.1%, and 4.2%, respectively (p<0.001). The only mean segmental scores below 3.0 were the sigmoid colon on supine (2.68) and prone (2.58) series, compared with 3.23 on decubitus series (p<0.001). Improvement in distention in both decubitus and supine positions over the prone position increased further with increasing BMI (p<0.001).

CONCLUSION

The right lateral decubitus position consistently yields the best colonic distention at CTC and significantly improves evaluation of the sigmoid colon. Prone distention was the worst, particularly as BMI increased. Routine supine and decubitus positioning should be considered for standard CTC protocols, particularly in obese individuals. Automated volumetric analysis provides for rapid objective assessment of colonic distention.

Recent developments in colorectal imaging

PURPOSE OF REVIEW

The aim of this review is to provide an update on important recent advances in radiologic colorectal imaging, with emphasis on detection, staging, and surveillance of colorectal neoplasia.

RECENT FINDINGS

Colorectal imaging advances with magnetic resonance (MR), computed tomography colonography (CTC), and positron emission tomography (PET) over the past year or so have been substantial. Progress in MRI for rectal cancer was most notable in terms of assessment of response to neoadjuvant therapy. Continued maturation and clinical validation of CTC was observed for the evaluation of advanced neoplasia, among other areas. Multimodality approaches to colorectal imaging that incorporate functional PET data have also made impressive strides forward.

SUMMARY

Recent advances in cross-sectional and functional radiologic imaging of the colorectum will positively impact the clinical capabilities for noninvasive evaluation of colorectal neoplasia.

Intra-individual comparison of magnesium citrate and sodium phosphate for bowel preparation at CT colonography: automated volumetric analysis of residual fluid for quality assessment

AIM

To perform an objective, intra-individual comparison of residual colonic fluid volume and attenuation associated with the current front-line laxative magnesium citrate (MgC) versus the former front-line laxative sodium phosphate (NaP) at CT colonography (CTC).

MATERIALS AND METHODS

This retrospective Health Insurance and Portability and Accountability Act-compliant study had institutional review board approval; informed consent was waived. The study cohort included 250 asymptomatic adults (mean age at index 56.1 years; 124 male/126 female) who underwent CTC screening twice over a 5 year interval. Colon catharsis at initial and follow-up screening employed single-dose NaP and double-dose MgC, respectively, allowing for intra-patient comparison. Automated volumetric analysis of residual colonic fluid volume and attenuation was performed on all 500 CTC studies. Colonic fluid volume <200 ml and mean attenuation between 300-900 HU were considered optimal. Paired t-test and McNemar's test were used to compare differences.

RESULTS

Residual fluid volumes <200 ml were recorded in 192 examinations (76.8%) following MgC and in 204 examinations (81.6%) following NaP (p = 0.23). The mean total residual fluid volume was 155 ± 114 ml for MgC and 143 ± 100 ml for NaP (p = 0.01). The attenuation range of 300-900 HU was significantly more frequent for MgC (n = 220, 88%) than for NaP (n = 127, 50.8%; p < 0.001). Mean fluid attenuation was significantly lower for MgC (700 ± 165 HU) than for NaP (878 ± 155 HU; p < 0.001). Concomitant presence of both optimal fluid volume and attenuation was significantly more frequent for MgC 65.2% than for NaP (38%; p < 0.001).

CONCLUSIONS

Objective intra-individual comparison using automated volumetric analysis suggests that the replacement of NaP by MgC as the front-line laxative for CTC has not compromised overall examination quality.

Carpet lesions detected at CT colonography: clinical, imaging, and pathologic features

PURPOSE

To describe carpet lesions (laterally spreading tumors ≥ 3 cm) detected at computed tomographic (CT) colonography, including their clinical, imaging, and pathologic features.

MATERIALS AND METHODS

The imaging reports for 9152 consecutive adults undergoing initial CT colonography at a tertiary center were reviewed in this HIPAA-compliant, institutional review board-approved retrospective study to identify all potential carpet lesions detected at CT colonography. Carpet lesions were defined as morphologically flat, laterally spreading tumors 3 cm or larger. For those patients with neoplastic carpet lesions, CT colonography studies were analyzed to determine maximal lesion width and height, oral contrast material coating, segmental location, and computer-aided detection (CAD) findings. Demographic data and details of clinical treatment in these patients were reviewed.

RESULTS

Eighteen carpet lesions in 18 patients (0.2%; mean age, 67.1 years; eight men, 10 women) were identified and were subsequently confirmed at colonoscopy and pathologic examination among 20 potential flat masses (≥3 cm) prospectively identified at CT colonography (there were two nonneoplastic rectal false-positive findings). No additional neoplastic carpet lesions were found in the cohort undergoing colonoscopy after CT colonography and/or surgery (there were no false-negatives). Mean lesion width was 46.5 mm (range, 30-80 mm); mean lesion height was 7.9 mm (range, 4-14 mm). Surface retention of oral contrast material was noted in all 18 cases. All but two lesions were located in the distal rectosigmoid or proximal right colon. At CAD, 17 (94.4%) lesions were detected (mean, 6.2 CAD marks per lesion). Sixteen lesions (88.9%) demonstrated advanced histologic features, including a villous component (n = 11), high-grade dysplasia (n = 4), and invasive cancer (n = 5). Sixteen patients (88.9%) required surgical treatment for complete excision.

CONCLUSION

CT colonography can effectively depict carpet lesions. Common features in this series included older patient age, rectal or cecal location, surface coating with oral contrast material, multiple CAD hits, advanced yet typically benign histologic features, and surgical treatment.