Magnetic resonance colonography for the detection of colorectal neoplasia in asymptomatic adults

[Computed tomography and magnetic resonance imaging of colonic diseases]

BACKGROUND

Early diagnosis of a luminal colonic disease is of essential clinical importance to start timely optimised therapy and detect complications early.

OBJECTIVES

This paper aims to provide an overview of the use of radiological methods in diagnosing neoplastic and inflammatory luminal diseases of the colon. Characteristic morphological features are discussed and compared.

MATERIALS AND METHODS

Based on an extensive literature review, the current state of knowledge regarding the imaging diagnosis of luminal pathologies of the colon and their importance in patient management is presented.

RESULTS

Technological advances in imaging have made the diagnosis of neoplastic and inflammatory colonic diseases using abdominal computed tomography and magnetic resonance imaging the established standard. Imaging is performed as part of the initial diagnosis in clinically symptomatic patients, to exclude complications, as a follow-up assessment under therapy and as an optional screening method in asymptomatic individuals.

CONCLUSIONS

Accurate knowledge of the radiological manifestations of the numerous luminal disease patterns, the typical distribution pattern and characteristic bowel wall changes are essential to improve diagnostic decision-making.

Colon Cancer Screening Methods: 2023 Update

Colorectal cancer (CRC) is a significant cause of morbidity and mortality worldwide. National screening guidelines have been implemented to identify and remove precancerous polyps before they become cancer. Routine CRC screening is advised for people with average risk starting at age 45 because it is a common and preventable malignancy. Various screening modalities are currently in use, ranging from stool-based tests (fecal occult blood test (FOBT), fecal immunochemical test (FIT), and FIT-DNA test), radiologic tests (computed tomographic colonography (CTC), double contrast barium enema), and visual endoscopic examinations (flexible sigmoidoscopy (FS), colonoscopy, and colon capsule endoscopy (CCE)) with their varying sensitivity and specificity. Biomarkers also play a vital role in assessing the recurrence of CRC. This review offers a summary of the current screening options, including biomarkers available to detect CRC, highlighting the benefits and challenges encompassing each screening modality.

Robotic, self-propelled, self-steerable, and disposable colonoscopes: Reality or pipe dream? A state of the art review

Robotic colonoscopes could potentially provide a comfortable, less painful and safer alternative to standard colonoscopy. Recent exciting developments in this field are pushing the boundaries to what is possible in the future. This article provides a comprehensive review of the current work in robotic colonoscopes including self-propelled, steerable and disposable endoscopes that could be alternatives to standard colonoscopy. We discuss the advantages and disadvantages of these systems currently in development and highlight the technical readiness of each system to help the reader understand where and when such systems may be available for routine clinical use and get an idea of where and in which situation they can best be deployed.

Systematic review: non-endoscopic surveillance for colorectal neoplasia in individuals with Lynch syndrome

BACKGROUND

Individuals with Lynch syndrome are at high risk for colorectal cancer (CRC). Regular colonoscopies have proven to decrease CRC incidence and mortality. However, colonoscopy is burdensome and interval CRCs still occur. Hence, an accurate, less-invasive screening method that guides the timing of colonoscopy would be of important value.

AIM

To outline the performance of non-endoscopic screening modalities for Lynch-associated CRC and adenomas.

METHODS

Systematic literature search in MEDLINE and EMBASE to identify studies investigating imaging techniques and biomarkers for detection of CRC and adenomas in Lynch syndrome. The QUADAS-2 tool was used for the quality assessment of included studies.

RESULTS

Seven of 1332 screened articles fulfilled the inclusion criteria. Two studies evaluated either CT colonography or MR colonography; both techniques were unable to detect CRC and (advanced) adenomas <10 mm. The other five studies evaluated plasma methylated-SEPTIN9, faecal immunochemical test (FIT), faecal tumour DNA markers (BAT-26, hMLH1, p53, D9S171, APC, D9S162, IFNA and DCC) and faecal microbiome as screening modalities. Sensitivity for CRC varied from 33% (BAT-26) to 70% (methylated-SEPTIN9) to 91% (hMLH1). High specificity (94-100%) for CRC and/or adenomas was observed for methylated-SEPTIN9, FIT and BAT-26. Desulfovibrio was enriched in the stool of patients having adenomas. However, all these studies were characterised by small populations, high/unclear risk of bias and/or low prevalence of adenomas.

CONCLUSIONS

Imaging techniques are unsuitable for colon surveillance in Lynch syndrome, whereas biomarkers are understudied. Having outlined biomarker research in Lynch-associated and sporadic CRC/adenomas, we believe that these non-invasive markers may hold potential (whether or not combined) for this population. As they could be of great value, (pre-)clinical studies in this field should be prioritised.

Overview of the Large Bowel Assessment Using Magnetic Resonance Imaging: Different Techniques for Current and Emerging Clinical Applications

Radiological assessments of the small and large bowel are essential in daily clinical practice. Over plain film X-ray and ultrasound, cross-sectional techniques are considered the most comprehensive imaging modalities. In fact, computed tomography and magnetic resonance imaging take great advantage of the three-dimensional appraisal and the extensive evaluation of the abdominal cavity, allowing intestinal evaluation as well as detection of extra-intestinal findings. In this context, the chief advantage of computed tomography is the fast scan time, which is crucial for emergency cases. Nonetheless, it is undeniably impaired using ionizing radiation. As the awareness of radiation exposure is a topic of increasing importance, magnetic resonance imaging is not only becoming a mere alternative but also a primary imaging technique used in assessing intestinal diseases. Specifically, the evaluation of the large bowel through MRI can be still considered relatively uncharted territory. Although it has demonstrated superior accuracy in the assessment of some clinical entities from inflammatory bowel disease to rectal carcinoma, its role needs to be consolidated in many other conditions. Moreover, different technical methods can be applied for colonic evaluation depending on the specific disease and segment involved. This article aims to provide a thorough overview of the techniques that can be utilized in the evaluation of the large bowel and a discussion on the major findings in different colonic pathologies of primary interest.

Improving staging of rectal cancer in the pelvis: the role of PET/MRI

PURPOSE

The role of positron emission tomography/magnetic resonance (PET/MR) in evaluating the local extent of rectal cancer remains uncertain. This study aimed to investigate the possible role of PET/MR versus magnetic resonance (MR) in clinically staging rectal cancer.

METHODS

This retrospective two-center cohort study of 62 patients with untreated rectal cancer investigated the possible role of baseline staging PET/MR versus stand-alone MR in determination of clinical stage. Two readers reviewed T and N stage, mesorectal fascia involvement, tumor length, distance from the anal verge, sphincter involvement, and extramural vascular invasion (EMVI). Sigmoidoscopy, digital rectal examination, and follow-up imaging, along with surgery when available, served as the reference standard.

RESULTS

PET/MR outperformed MR in evaluating tumor size (42.5 ± 21.03 mm per the reference standard, 54 ± 20.45 mm by stand-alone MR, and 44 ± 20 mm by PET/MR, P = 0.004), and in identifying N status (correct by MR in 36/62 patients [58%] and by PET/MR in 49/62 cases [79%]; P = 0.02) and external sphincter infiltration (correct by MR in 6/10 and by PET/MR in 9/10; P = 0.003). No statistically significant differences were observed in relation to any other features.

CONCLUSION

PET/MR provides a more precise assessment of the local extent of rectal cancers in evaluating cancer length, N status, and external sphincter involvement. PET/MR offers the opportunity to improve clinical decision-making, especially when evaluating low rectal tumors with possible external sphincter involvement.

[Colorectal cancer: role of imaging in screening]

CLINICAL PROBLEM

Colorectal cancer (CRC) is a major cause of cancer-related morbidity and mortality. Most colorectal cancers derive from benign precursor lesions, so-called adenomatous polyps, over a long period of time. Colorectal cancer screening is based on the detection of precancerous polyps and early stage CRC in asymptomatic individuals to reduce CRC incidence and mortality. The protective effect of screening programs can be improved by increasing the screening rates.

PRACTICAL RECOMMENDATIONS

Apart from the established examinations, CT colonography (CTC) has been proposed as an optional test for colorectal cancer screening. The detection rates of CTC for large polyps and cancer are similar to the ones of colonoscopy and superior to stool-based tests. CTC is therefore the radiological test of choice for the detection of colorectal neoplasia. It has replaced double contrast barium enema for almost all indications. As a minimally invasive procedure, CTC has a high safety profile and good patient acceptance. The evaluation of extracolonic organs in addition to the colon can increase examination efficacy. The option to choose CTC as a CRC screening test has the potential to increase the overall screening rates.

ACR Appropriateness Criteria® Colorectal Cancer Screening

This review summarizes the relevant literature regarding colorectal screening with imaging. For individuals at average or moderate risk for colorectal cancer, CT colonography is usually appropriate for colorectal cancer screening. After positive results on a fecal occult blood test or immunohistochemical test, CT colonography is usually appropriate for colorectal cancer detection. For individuals at high risk for colorectal cancer (eg, hereditary nonpolyposis colorectal cancer, ulcerative colitis, or Crohn colitis), optical colonoscopy is preferred because of its ability to obtain biopsies to detect dysplasia. After incomplete colonoscopy, CT colonography is usually appropriate for colorectal cancer screening for individuals at average, moderate, or high risk. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Colon cancer screening with CT colonography: logistics, cost-effectiveness, efficiency and progress

Colorectal cancer (CRC) incidence and mortality can be significantly reduced by population screening. Several different screening methods are currently in use, and this review focuses specifically on the imaging technique computed tomographic colonography (CTC). The challenges and logistics of CTC screening, as well as the importance of test accuracy, uptake, quality assurance and cost-effectiveness will be discussed. With comparable advanced adenoma detection rates to colonoscopy (the most commonly used whole-colon investigation), CTC is a less-invasive alternative, requiring less laxative, and with the potential benefit that it permits assessment of extra colonic structures. Three large-scale European trials have contributed valuable evidence supporting the use of CTC in population screening, and highlight the importance of selecting appropriate clinical management pathways based on initial CTC findings. Future research into CTC-screening will likely focus on radiologist training and CTC quality assurance, with identification of evidence-based key performance indicators that are associated with clinically-relevant outcomes such as the incidence of post-test interval cancers (CRC occurring after a presumed negative CTC). In comparison to other CRC screening techniques, CTC offers a safe and accurate option that is particularly useful when colonoscopy is contraindicated. Forthcoming cost-effectiveness analyses which evaluate referral thresholds, the impact of extra-colonic findings and real-world uptake will provide useful information regarding the feasibility of future CTC population screening.

Colon Cancer Screening in Concierge Practice

OBJECTIVES

This study evaluated the effectiveness of the Center for Executive Medicine (CEM) concierge primary care practice on preventive colorectal cancer (CRC) screening rates relative to local and national comparator data.

METHODS

We performed an electronic medical record search encompassing our entire patient population who are between the ages of 50 and 75 years to determine the rate of CRC screening. We compared this rate with the average rate of Medicare Advantage plans reported by our Independent Physician Association (IPA) in 2015 and national health plans reported by the National Committee for Quality Assurance in 2014.

RESULTS

The CEM had a CRC screening rate of 90.2%, which was significantly higher than local IPA Medicare Advantage plans (63.3%) and National Committee for Quality Assurance national plans (57.7%-66.5%). CEM members were significantly more likely than were IPA members to undergo screening (odds ratio 1.425, 95% confidence interval 1.348-1.507, P < 0.0001).

CONCLUSIONS

These results suggest that the CEM practice strategy and processes increase CRC screening rates.

Alternatives to Incomplete Colonoscopy

A thorough and complete colonoscopy is critically important in preventing colorectal cancer. Factors associated with difficult and incomplete colonoscopy include a poor bowel preparation, severe diverticulosis, redundant colon, looping, adhesions, young and female patients, patient discomfort, and the expertise of the endoscopist. For difficult colonoscopy, focusing on bowel preparation techniques, appropriate sedation and adjunct techniques such as water immersion, abdominal pressure techniques, and patient positioning can overcome many of these challenges. Occasionally, these fail and other alternatives to incomplete colonoscopy have to be considered. If patients have low risk of polyps, then noninvasive imaging options such as computed tomography (CT) or magnetic resonance (MR) colonography can be considered. Novel applications such as Colon Capsule™ and Check-Cap are also emerging. In patients in whom a clinically significant lesion is noted on a noninvasive imaging test or if they are at a higher risk of having polyps, balloon-assisted colonoscopy can be performed with either a single- or double-balloon enteroscope or colonoscope. The application of these techniques enables complete colonoscopic examination in the vast majority of patients.

Diagnostics and Epidemiology of Colorectal Cancer

Colorectal cancer is one of the leading causes of cancer-related morbidity and mortality. Main risk factors include advanced age, family history, male sex, and lifestyle factors. Screening can reduce incidence and death from colorectal cancer. Therefore, prevention and early detection are crucial in order to detect and remove pre-neoplastic adenomas and to detect cancers at early stages. Colonoscopy, flexible sigmoidoscopy, and fecal occult blood tests are established tools for screening. Newer fecal immunochemical tests reveal higher sensitivities for advanced adenoma and cancer than guaiac-based hemoccult tests. Molecular stool and blood tests as well as virtual colonoscopy and colon capsule endoscopy are promising new developments so far not established as routine instruments for the prevention and early detection of colorectal cancer. Colonoscopy is the method of choice for the diagnosis of colorectal cancer and for adenoma removal. Prognosis is essentially dependent on the tumor stage at the time of the initial diagnosis. Proper staging based on imaging prior to therapy is a prerequisite. In rectal cancer, local staging is an essential requirement for the identification of appropriate candidates for neoadjuvant therapy.

The potential of imaging techniques as a screening tool for colorectal cancer: a cost-effectiveness analysis

OBJECTIVE

Imaging may be promising for colorectal cancer (CRC) screening, since it has test characteristics comparable with colonoscopy but is less invasive. We aimed to assess the potential of CT colonography (CTC) and MR colonography (MRC) in terms of (cost-effectiveness) using the Adenoma and Serrated pathway to Colorectal CAncer model.

METHODS

We compared several CTC and MRC strategies with 5- or 10-yearly screening intervals with no screening, 10-yearly colonoscopy screening and biennial faecal immunochemical test (FIT) screening. We assumed trial-based participation rates in the base-case analyses and varied the rates in sensitivity analyses. Incremental lifetime costs and health effects were estimated from a healthcare perspective.

RESULTS

The health gain of CTC and MRC was similar and ranged from 0.031 to 0.048 life-year gained compared with no screening, for 2-5 screening rounds. Lifetime costs per person for MRC strategies were €60-110 higher than those for CTC strategies with an equal number of screening rounds. All imaging-based strategies were cost-effective compared with no screening. FIT screening was the dominant screening strategy, leading to most LYG and highest cost-savings. Compared with three rounds of colonoscopy screening, CTC with five rounds was found to be cost-effective in an incremental analysis of imaging strategies. Assumptions on screening participation have a major influence on the ordering of strategies in terms of costs and effects.

CONCLUSION

CTC and MRC have potential for CRC screening, compared with no screening and compared with three rounds of 10-yearly colonoscopy screening. When taking FIT screening as the reference, imaging is not cost-effective. Participation is an important driver of effectiveness and cost estimates.

ADVANCES IN KNOWLEDGE

This is the first study to assess the cost-effectiveness of MRC screening for CRC.

Colonoscopy detects significantly more flat adenomas than 3-tesla magnetic resonance colonography: a pilot trial

BACKGROUND AND STUDY AIMS

Colorectal cancer (CRC) is one of the most common cancers worldwide, and several efforts have been made to reduce its occurrence or severity. Although colonoscopy is considered the gold standard in CRC prevention, it has its disadvantages: missed lesions, bleeding, and perforation. Furthermore, a high number of patients undergo this procedure even though no polyps are detected. Therefore, an initial screening examination may be warranted. Our aim was to compare the adenoma detection rate of magnetic resonance colonography (MRC) with that of optical colonoscopy.

PATIENTS AND METHODS

A total of 25 patients with an intermediate risk for CRC (17 men, 8 women; mean age 57.6, standard deviation 11) underwent MRC with a 3.0-tesla magnet, followed by colonoscopy. The endoscopist was initially blinded to the results of MRC and unblinded immediately after examining the distal rectum. Following endoscopic excision, the size, anatomical localization, and appearance of all polyps were described according to the Paris classification.

RESULTS

A total of 93 lesions were detected during colonoscopy. These included a malignant infiltration of the transverse colon due to gastric cancer in 1 patient, 28 adenomas in 10 patients, 19 hyperplastic polyps in 9 patients, and 45 non-neoplastic lesions. In 5 patients, no lesion was detected. MRC detected significantly fewer lesions: 1 adenoma (P = 0.001) and 1 hyperplastic polyp (P = 0.004). The malignant infiltration was seen with both modalities. Of the 28 adenomas, 23 (82 %) were 5 mm or smaller; only 4 adenomas 10 mm or larger (14 %) were detected.

CONCLUSION

MRC does not detect adenomas sufficiently independently of the location of the lesion. Even advanced lesions were missed. Therefore, colonoscopy should still be considered the current gold standard, even for diagnostic purposes.

Developments in Screening Tests and Strategies for Colorectal Cancer

BACKGROUND

Worldwide, colorectal cancer (CRC) is the third most common cancer in men and second most common in women. It is the fourth most common cause of cancer mortality. In the United States, CRC is the third most common cause of cancer and second most common cause of cancer mortality. Incidence and mortality rates have steadily fallen, primarily due to widespread screening.

METHODS

We conducted keyword searches on PubMed in four categories of CRC screening: stool, endoscopic, radiologic, and serum, as well as news searches in Medscape and Google News.

RESULTS

Colonoscopy is the gold standard for CRC screening and the most common method in the United States. Technological improvements continue to be made, including the promising "third-eye retroscope." Fecal occult blood remains widely used, particularly outside the United States. The first at-home screen, a fecal DNA screen, has also recently been approved. Radiological methods are effective but seldom used due to cost and other factors. Serum tests are largely experimental, although at least one is moving closer to market.

CONCLUSIONS

Colonoscopy is likely to remain the most popular screening modality for the immediate future, although its shortcomings will continue to spur innovation in a variety of modalities.

Colorectal cancer screening: a global overview of existing programmes

Colorectal cancer (CRC) ranks third among the most commonly diagnosed cancers worldwide, with wide geographical variation in incidence and mortality across the world. Despite proof that screening can decrease CRC incidence and mortality, CRC screening is only offered to a small proportion of the target population worldwide. Throughout the world there are widespread differences in CRC screening implementation status and strategy. Differences can be attributed to geographical variation in CRC incidence, economic resources, healthcare structure and infrastructure to support screening such as the ability to identify the target population at risk and cancer registry availability. This review highlights issues to consider when implementing a CRC screening programme and gives a worldwide overview of CRC burden and the current status of screening programmes, with focus on international differences.

Controversies in colorectal cancer screening

BACKGROUND

Colorectal cancer (CRC) is one of the most common cancers worldwide and a good candidate for screening programmes. However, there is controversy concerning which of the available screening tests should be used.

SUMMARY

There is general agreement that screening for CRC in the asymptomatic population should begin at the age of 50. Several different screening methods are available which can be separated into those that mainly detect cancers: faecal occult blood tests [guaiac (FOBT) and immunochemical (FIT)], genetic stool tests, blood tests and the M2-pyruvate kinase (M2-PK) test. Methods that detect cancers and polyps are colonoscopy, sigmoidoscopy, CT-colonography (CT-C) and colon capsule endoscopy. The only tests for which a reduction in CRC mortality compared to no screening have been proven in randomized trials are FOBT and sigmoidoscopy. Several trials suggest that FIT are superior to FOBT in terms of detection rates of cancers and advanced adenomas and possibly compliance. There is indirect evidence suggesting efficacy of colonoscopy as a screening test. The role of CT-C is controversial. There is data suggesting a good sensitivity for neoplasia >9 mm with a lower sensitivity for smaller neoplasia. However, radiation exposure is considered a major limitation in some countries. Unresolved questions include the lesion cut-off for referral to colonoscopy and work-up of extracolonic findings. For other methods, like genetic stool testing using newer markers, blood tests, capsule endoscopy and M2-PK, there is currently insufficient data on screening of the asymptomatic population. Key Messages: Colorectal screening is recommended and should be performed in the form of an organized programme. If detection of early-stage cancers is the aim of a screening programme, FIT seem to be superior to FOBT. If detection and removal of adenomas is the aim of a screening programme, endoscopic methods seem to be good alternatives. Sigmoidoscopy is easier to perform but will likely only have an effect on distal cancers. Colonoscopy is more invasive but enables inspection of the whole colon. The role of CT-C, capsule endoscopy, genetic stool tests, blood tests and M2-PK is currently unknown.

[Colorectal cancer screening: evidence and implementation]

BACKGROUND

Colorectal cancer (CRC) is the second most common cancer among both men and women in Germany. Owing to its relatively slow growth, perspectives for effective early detection are much better than for other forms of cancer.

AIM

To summarize the evidence on effectiveness and cost-effectiveness of CRC screening, and to provide an overview on the current state and perspectives for effective CRC screening.

MATERIALS AND METHODS

Summary and critical review of evidence from randomized trials and observational epidemiological studies.

RESULTS

A reduction in CRC mortality by offering annual fecal occult blood tests or once-only flexible sigmoidoscopy has been demonstrated in randomized trials. Novel fecal immunochemical tests for hemoglobin in stool have been shown to be more sensitive than traditional fecal occult blood tests and could substantially improve noninvasive CRC screening. Epidemiological studies suggest that the majority of CRC cases and deaths could be prevented by colonoscopy and removal of colorectal adenomas. However, adherence to screening offered outside organized screening programs is low. The National Cancer Plan recommends an organized CRC screening program in Germany. The law on the early detection of cancer from April 2013 has paved the way for its implementation.

DISCUSSION

The great potential for CRC prevention by early detection has so far only been realized to a very limited extent in Germany. Introduction of an organized screening program and the offer of enhanced noninvasive screening tests could strongly enhance the utilization and effectiveness of CRC screening in Germany. The political frame has been set, and timely quality-assured implementation is required.

CT colonography: accuracy, acceptance, safety and position in organised population screening

Colorectal cancer (CRC) is the second most common cancer and second most common cause of cancer-related deaths in Europe. The introduction of CRC screening programmes using stool tests and flexible sigmoidoscopy, have been shown to reduce CRC-related mortality substantially. In several European countries, population-based CRC screening programmes are ongoing or being rolled out. Stool tests like faecal occult blood testing are non-invasive and simple to perform, but are primarily designed to detect early invasive cancer. More invasive tests like colonoscopy and CT colonography (CTC) aim at accurately detecting both CRC and cancer precursors, thus providing for cancer prevention. This review focuses on the accuracy, acceptance and safety of CTC as a CRC screening technique and on the current position of CTC in organised population screening. Based on the detection characteristics and acceptability of CTC screening, it might be a viable screening test. The potential disadvantage of radiation exposure is probably overemphasised, especially with newer technology. At this time-point, it is not entirely clear whether the detection of extracolonic findings at CTC is of net benefit and is cost effective, but with responsible handling, this may be the case. Future efforts will seek to further improve the technique, refine appropriate diagnostic algorithms and study cost-effectiveness.

Optimal section thickness for detection of polyps at MR: resolution phantom study

PURPOSE

To determine (1) the sensitivity for detection of small polyps with varying MR slice thicknesses using a resolution phantom; (2) reader confidence in polyp detection; and (3) image acquisition time.

METHODS

A resolution phantom was created using a 3D printer. Polyp morphologies were sessile (height = diameter), flat (height = 1/2 diameter of the base), and pedunculated (stalk length = polyp diameter). Polyp diameters were 5, 7, 10, and 12 mm. Images were acquired with section thicknesses of 5, 3, and 1 mm. Images were independently reviewed by 4 board-certified radiologists who were blinded to phantom design and sequences parameters. Readers recorded maximal polyp diameter and confidence level that a polyp was present on a 1-100 point scale. Image acquisition time was also recorded.

RESULTS

All polyps were detected by all 4 readers in the 5-mm-section thickness series. All polyps were detected by 3 readers in the 3- and 1-mm-section thickness series. The fourth reader identified 11/12 polyps in the 3- and 1-mm-section thickness series. Confidence levels were not statistically significantly different for the different section thicknesses (p = 0.28). Increasing the section thickness from 1 to 5 mm decreased image acquisition time from 3 min 54 s to 41 s.

CONCLUSIONS

Five-millimeter-section thickness was adequate for identification of 5-12 mm polyps regardless of shape. Pending further reduction in acquisition time, this prototype sequence holds promise for segmental imaging of the colon with MR colonography.

Dual-energy CT colonography for preoperative "one-stop" staging in patients with colonic neoplasia

RATIONALE AND OBJECTIVES

To evaluate the benefits of dual-energy computed tomography (CT) colonography (DECTC) as a preoperative staging tool in patients with clinically suspected colorectal cancer (CRC).

MATERIALS AND METHODS

Twenty-two patients with colorectal neoplasia underwent preoperative abdominal DECTC on a dual-source scanner (SOMATOM Definition Flash; Siemens) operated at tube potentials of Sn140/100 kVp. Scans were evaluated for local tumor stage and the presence of synchronous intracolonic and extracolonic findings using dual-energy color-coded images. An enhancement ≥25 Hounsfield units (HU) was defined to indicate malignancy. Patients' effective doses were calculated.

RESULTS

Preoperative DECTC allowed for complete bowel evaluation in all patients, including subjects with stenosing CRC. DECTC revealed 22 carcinomas (mean enhancement, 47 ± 12 HU). In total, 22 synchronous intracolonic lesions were detected, including 19 adenomas (mean enhancement, 51 ± 19 HU). Benign structures showed enhancement <25 HU. Comparing DECTC to histopathology, 95% carcinomas and 71% synchronous lesions proximal to stenosing CRC could be verified. Mean estimated effective dose was 13.0 ± 5.2 mSv.

CONCLUSIONS

Preoperative DECTC can be used as an accurate and dose-efficient primary-staging examination. Especially after incomplete optical colonoscopy, virtual colonoscopy enables full preoperative colonic assessment on the same day. Dual-energy CT enables distinction between neoplasia and non-neoplastic findings within and outside the colon. Therefore, DECTC can be regarded as a promising "one-stop" staging examination in patients with clinically suspected CRC.

Magnetic resonance colonography with a limited bowel preparation and automated carbon dioxide insufflation in comparison to conventional colonoscopy: patient burden and preferences

OBJECTIVES

To evaluate patient burden and preferences for MR colonography with a limited bowel preparation and automated carbon dioxide insufflation in comparison to conventional colonoscopy.

METHODS

Symptomatic patients were consecutively recruited to undergo MR colonography with automated carbon dioxide insufflation and a limited bowel preparation followed within four weeks by colonoscopy with a standard bowel cleansing preparation. Four questionnaires regarding burden (on a five-point scale) and preferences (on a seven-point scale) were addressed after MR colonography and colonoscopy and five weeks after colonoscopy.

RESULTS

Ninety-nine patients (47 men, 52 women; mean age 62.3, SD 8.7) were included. None of the patients experienced severe or extreme burden from the MR colonography bowel preparation compared to 31.5% of the patients for the colonoscopy bowel preparation. Colonoscopy was rated more burdensome (25.6% severe or extreme burden) compared to MR colonography (5.2% severe or extreme burden) (P<0.0001). When discarding the bowel preparations, the examinations were rated equally burdensome (P=0.35). The majority of patients (61.4%) preferred MR colonography compared to colonoscopy (29.5%) immediately after the examinations and five weeks later (57.0% versus 39.5%).

CONCLUSION

MR colonography with a limited bowel preparation and automated carbon dioxide insufflation demonstrated less burden compared to colonoscopy. The majority of patients preferred MR colonography over colonoscopy.

Magnetic resonance imaging of the gut: a primer for the luminal gastroenterologist

Magnetic resonance imaging (MRI) is well established for imaging the solid organs of the abdomen and pelvis. In recent years it has been having an increasingly important role in the evaluation of the gastrointestinal (GI) tract. Fluoroscopy and abdominal computed tomography, the traditional mainstays of bowel imaging, remain valuable; however, the contemporary emphasis on decreasing patient radiation exposure is driving practice toward non-ionizing modalities such as MRI. The inherent dynamic properties of MRI, its superior tissue contrast, and cross-sectional capabilities offer additional advantages. Here we review, from esophagus to anus, techniques and indications for MRI of the GI lumen with an emphasis on the normal MRI appearance of the GI tract and commonly encountered pathology.

Competition in Colon Cancer Screening? What Is the Role of Colonoscopy?

BACKGROUND

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the Western world. The incidence could be reduced if this cancer were to be diagnosed at an early stage of disease. A competition has started between the existing screening methods to be the most efficient in detecting premalignant conditions. This review illustrates the current state of screening techniques for CRC.

METHOD

Pubmed was searched for meta-analyses and prospective studies on screening for CRC, with an emphasis on colonography, computed tomographic colonography (CTC), magnetic resonance colonography (MRC), stool DNA testing, and colon capsule endoscopy, and critical appraisal of the research was done by the reviewers.

RESULTS

The imaging techniques (CTC and MRC) had similar detection rates for bigger lesions (≥10 mm) as colonoscopy. High-definition colonoscopy showed better efficiency with smaller lesions. The techniques developing around colonoscopy such as the retro-viewing colonoscope, the balloon colonoscope, or the 330-degree viewing colonoscope try to enhance efficacy by reducing the adenoma miss rate in right-sided, non-polypoid lesions. Colon capsule endoscopy and the stool detection systems are limited to identifying cancer but not necessarily adenomas.

CONCLUSION

Colonoscopy is the preferred CRC screening strategy and the undisputed gold standard in terms of efficacy.