Limitations of Fluorine 18 Fluoromisonidazole in Assessing Treatment-induced Tissue Hypoxia after Transcatheter Arterial Embolization of Hepatocellular Carcinoma: A Prospective Pilot Study.

Purpose To determine the variance and correlation with tumor viability of fluorine 18 (18F) fluoromisonidazole (FMISO) uptake in hepatocellular carcinoma (HCC) prior to and after embolization treatment. Materials and Methods In this single-arm, single-center, prospective pilot study between September 2016 and March 2017, participants with at least one tumor measuring 1.5 cm or larger with imaging or histologic findings diagnostic for HCC were enrolled (five men; mean age, 68 years; age range, 61-76 years). Participants underwent 18F-FMISO PET/CT before and after bland embolization of HCC. A tumor-to-liver ratio (TLR) was calculated by using standardized uptake values of tumor and liver. The difference in mean TLR before and after treatment was compared by using a Wilcoxon rank sum test, and correlation between TLR and tumor viability was assessed by using the Spearman rank correlation coefficient. Results Four participants with five tumors were included in the final analysis. The median tumor diameter was 3.2 cm (IQR, 3.0-3.9 cm). The median TLR before treatment was 0.97 (IQR, 0.88-0.98), with a variance of 0.02, and the median TLR after treatment was 0.85 (IQR, 0.79-1), with a variance of 0.01; both findings indicate a narrow range of 18F-FMISO uptake in HCC. The Spearman rank correlation coefficient was 0.87, indicating a high correlation between change in TLR and nonviable tumor. Conclusion Although there was a correlation between change in TLR and response to treatment, the low signal-to-noise ratio of 18F-FMISO in the liver limited its use in HCC. Keywords: Molecular Imaging-Clinical Translation, Embolization, Abdomen/Gastrointestinal, Liver Clinical trial registration no. NCT02695628 © RSNA, 2022.

Society of Abdominal Radiology Disease Focused Panel Survey on Clinical Utilization of Incidental Pancreatic Cyst Management Recommendations and Template Reporting.

OBJECTIVE: To assess current practice patterns with respect to protocols used for incidental pancreatic cyst follow-up, management guidelines, and template reporting. METHODS: The Society of Abdominal Radiology Disease Focused Panel on intraductal pancreatic neoplasms distributed an anonymous 14-question survey to its members in June 2018 that focused on current utilization of incidental pancreatic cyst guidelines, protocols, and template reporting. RESULTS: Among the 1,390 email invitations, 323 responded, and 94.7% (306 of 323) completed all questions. Respondents were mainly radiologists (93.8%, 303 of 323) from academic institutions (74.7%, 227 of 304) in North America (93.7%, 286 of 305). Of respondents, 42.5% (136 of 320) preferred 2017 ACR recommendations, 17.8% (57 of 320) homegrown systems, 15.0% (48 of 320) Fukuoka guidelines, and 7.8% (25 of 320) American Gastroenterological Association guidelines. The majority (68.7%, 222 of 323) agreed or strongly agreed that developing a single international consensus recommendation for management was important, and most radiologists preferred to include them in reports (231 of 322, 71.7%); yet only half included recommendations in >75% of reports (161 of 321). MR cholangiopancreatography was the modality of choice for follow-up of <2.5 cm cysts. Intravenous contrast was routinely used by 69.7% (212 of 304). Standardized reporting templates were rarely used in practice (12.8% 39 of 306). CONCLUSIONS: Nearly 7 of 10 radiologists desire a unified international consensus recommendation for management of incidental cystic pancreatic lesions; ACR 2017 recommendations are most commonly used, followed by homegrown systems and Fukuoka guidelines. The majority of radiologists routinely use MR cholangiopancreatography with intravenous contrast for follow-up of incidental cystic lesions, but template reporting is rarely used.

The impact of computed high b-value images on the diagnostic accuracy of DWI for prostate cancer: A receiver operating characteristics analysis.

To evaluate the performance of computed high b value diffusion-weighted images (DWI) in prostate cancer detection. 97 consecutive patients who had undergone multiparametric MRI of the prostate followed by biopsy were reviewed. Five radiologists independently scored 138 lesions on native high b-value images (b = 1200 s/mm2), apparent diffusion coefficient (ADC) maps, and computed high b-value images (contrast equivalent to b = 2000 s/mm2) to compare their diagnostic accuracy. Receiver operating characteristic (ROC) analysis and McNemar's test were performed to assess the relative performance of computed high b value DWI, native high b-value DWI and ADC maps. No significant difference existed in the area under the curve (AUC) for ROCs comparing B1200 (b = 1200 s/mm2) to computed B2000 (c-B2000) in 5 readers. In 4 of 5 readers c-B2000 had significantly increased sensitivity and/or decreased specificity compared to B1200 (McNemar's p < 0.05), at selected thresholds of interpretation. ADC maps were less accurate than B1200 or c-B2000 for 2 of 5 readers (P < 0.05). This study detected no consistent improvement in overall diagnostic accuracy using c-B2000, compared with B1200 images. Readers detected more cancer with c-B2000 images (increased sensitivity) but also more false positive findings (decreased specificity).

Spectral Doppler Waveforms for Diagnosis of Appendicitis: Potential Utility of Point Peak Systolic Velocity and Resistive Index Values.

Purpose To test the hypothesis that appendiceal spectral Doppler waveforms can distinguish patients with and patients without appendicitis. Materials and Methods In this retrospective study, Doppler waveforms were obtained from intramural appendiceal arteries identified with color Doppler imaging in 60% (93 of 155) of consecutive patients whose appendices were visualized at graded compression ultrasonography (US) performed for suspected appendicitis (53 male and 40 female; age, 1-56 years; mean, 14.5 years) over the 5-month period from November 2015 through March 2016. Point, non-angle-corrected peak systolic velocity (PSV) and resistive index (RI) values were compared between patients with and patients without appendicitis by utilizing histopathologically proven appendicitis and 6-week clinical follow-up as diagnostic reference standards. Data were assessed by using the Student t test, exact binomial distribution, two-sample test of proportions, and receiver operating characteristic analysis. Results Among the 93 patients, 36 (38.7%) had proven appendicitis (mean PSV, 19.7 cm/sec; mean RI, 0.69) and 57 patients (61.2%) did not (mean PSV, 7.1 cm/sec, P < .0001; mean RI, 0.50, P < .0001). The area under the receiver operating characteristic curve for the diagnosis of appendicitis was 0.97 (95% confidence interval [CI]: 0.95, 1.00) for PSV and 0.86 (95% CI: 0.78, 0.95; P = .011) for RI. Chosen discriminatory criteria of PSV greater than 10 cm/sec and RI greater than 0.65 yielded specificity for appendicitis of 94.7% and 96.5% with sensitivity of 88.9% and 63.9% (P = .013) and negative predictive value of 93.1% and 80.9% (P = .045), respectively. Original clinical graded compression US interpretations based on established US findings demonstrated specificity of 96.2% and sensitivity of 100.0%. Considering the subset of 20 patients whose maximum outer diameter measured 6-8 mm, the discriminatory criteria of PSV greater than 10 cm/sec and RI greater than 0.65 yielded specificity for appendicitis of 88.9% each, with sensitivity of 100.0% and 63.6% and negative predictive value of 100.0% and 66.6%, respectively. Conclusion In patients with visualized appendices at US, those with appendicitis exhibit significantly higher point PSV and point RI values than do patients without appendicitis and are distinguishable with high specificity by using a PSV greater than 10 cm/sec and an RI greater than 0.65 as diagnostic criteria. © RSNA, 2017.

The incidental bone lesion on computed tomography: management tips for abdominal radiologists.

Incidental bone lesions are commonly seen on abdominal and pelvic computed tomography (CT) examinations. These incidental bone lesions can be diagnostically challenging to the abdominal radiologist who may not be familiar with their appearance or their appropriate management. The characterization of such bone lesions as non-aggressive or aggressive based on their CT appearance involves similar principles to their morphologic evaluation on radiographs. Knowledge of the age of the patient and the presence of symptoms, mainly bone pain, can improve analysis. Examples of bone lesions that may be encountered include solitary or multifocal bone lesions, osteochondromatous and chondroid tumors, Paget's disease, avascular necrosis/bone infarctions, iatrogenic lesions, and periarticular lesions. This pictorial essay aims to provide a framework for the analysis of incidental bone lesions on CT and when further imaging and clinical work-up should be recommended.

Multidetector CT imaging of the pancreatic groove: differentiating carcinomas from paraduodenal pancreatitis.

OBJECTIVE: This study aims to identify multidetector row CT (MDCT) findings that differentiate paraduodenal pancreatitis (PDP) from groove carcinomas (GC). METHODS: Two radiologists retrospectively reviewed various imaging features on pancreas protocol CT scans of 8 PDP and 8 GC patients. Two-tailed Fisher's Exact Test was used for statistical analysis. RESULTS: MDCT findings correlating with PDP included benign common bile duct morphology (P<.01), duodenal wall thickening (P<.05), and cystic groove lesions (P<.01). A statistical difference in gastroduodenal artery (GDA) encasement was not observed (P=.119). CONCLUSIONS: There are several MDCT findings that favor PDP over GC. However, presence of GDA encasement is not a reliable distinguishing feature.

Color Doppler Imaging of the Appendix: Criteria to Improve Specificity for Appendicitis in the Borderline-Size Appendix.

OBJECTIVES: To test the hypothesis that continuous intramural vascular signal measuring at least 3 mm on color Doppler imaging is highly specific for appendicitis in patients with diagnostically borderline-size appendices. METHODS: Two blinded observers independently reviewed color Doppler images of the appendix in 94 consecutive patients who had undergone sonography for suspected appendicitis and whose appendices were of diagnostically borderline size (6-8 mm maximum outer diameter). Intramural vascular flow on color Doppler images was classified as absent, type 1 (only punctate and dispersed signal), or type 2 (continuous linear or curvilinear signal measuring at least 3.0 mm in long- or short-axis views). Histopathologic examination and clinical follow-up served as reference standards. Proportions were assessed by the exact binomial test. RESULTS: Of the 94 patients, 33 (35.1%) had type 1 flow (of whom 5 [15.2%] had appendicitis); 23 (24.5%) had type 2 flow (of whom 20 [87.0%] had appendicitis); and 38 (40.4%) had absent flow (of whom 10 [26.3%] had appendicitis). The sensitivity, specificity, and odds ratio of type 2 flow as an indicator of appendicitis were 57.1%, 94.9%, and 24.9 (P< .001), respectively; the corresponding values for type 1 flow as an indicator of normal appendices were and 47.5%, 85.7%, and 5.4 (P = .002). CONCLUSIONS: Continuous intramural linear or curvilinear signal measuring at least 3 mm on color Doppler imaging is a highly specific, although relatively insensitive, sign of acute appendicitis in noncompressible appendices of diagnostically borderline size (6-8 mm).

Predictors of appendicitis on computed tomography among cases with borderline appendix size.

Confident diagnosis of appendicitis when the appendix is borderline (6 to 7 mm) in size can be challenging. This retrospective study assessed computed tomography (CT) findings that are most predictive of appendicitis when the appendix is borderline in diameter. Three radiologists conducted separate, blind retrospective reviews of 105 contrast-enhanced CTs with borderline appendices. Presence or absence of appendicitis was confirmed by chart review of clinical or surgical outcomes. Logistic regression was used to determine the odds ratio (OR) and the receiver operating characteristic for CT features predictive of appendicitis. Absence of intraluminal air (OR = 5.11, p < 0.001), wall hyperemia (OR = 3.92, p = 0.002), wall thickening (OR = 29.7, p < 0.001), and fat stranding (OR = 3.85, p = 0.003) were significant findings in univariate logistic regression. Using a multivariate model, we found that the absence of intraluminal air (OR = 6.04, p = 0.002) and wall thickening (OR = 24.6, p < 0.001) remained statistically significant and were unaffected by adjustment for gender and pediatric age. The area under the curve was significantly greater for the multivariate model than the initial, clinical CT impressions (p = 0.024). The combination of wall thickening and absence of intraluminal air was 92.6 % (95 % CI 75.7-99.1) sensitive and 82.4 % (95 % CI 65.5-93.2) specific for appendicitis. Wall thickening and the absence of intraluminal air are prominent predictors of appendicitis and, if present together, these features may aid in identifying appendicitis on CT when the appendix is borderline in size.

Model-based iterative reconstruction compared to adaptive statistical iterative reconstruction and filtered back-projection in CT of the kidneys and the adjacent retroperitoneum.

RATIONALE AND OBJECTIVES: To prospectively evaluate the perceived image quality of model-based iterative reconstruction (MBIR) compared to adaptive statistical iterative reconstruction (ASIR) and filtered back-projection (FBP) in computed tomography (CT) of the kidneys and retroperitoneum. MATERIALS AND METHODS: With investigational review board and Health Insurance Portability and Accountability Act compliance, 17 adults underwent 31 contrast-enhanced CT acquisitions at constant tube potential and current (range 30-300 mA). Each was reconstructed with MBIR, ASIR (50%), and FBP. Four reviewers scored each reconstruction's perceived image quality overall and the perceived image quality of seven imaging features that were selected by the authors as being relevant to imaging in the region and pertinent to the evaluation of high-quality diagnostic CT. RESULTS: MBIR perceived image quality scored superior to ASIR and FBP both overall (P < .001) and for observations of the retroperitoneal fascia (99.2%), corticomedullary differentiation (94.4%), renal hilar structures (96.8%), focal renal lesions (92.5%), and mitigation of streak artifact (100.0%; all, P < .001). MBIR achieved diagnostic overall perceived image quality with approximately half the radiation dose required by ASIR and FBP. The noise curve of MBIR was significantly lower and flatter (P < .001). CONCLUSIONS: Compared to ASIR and FBP, MBIR provides superior perceived image quality, both overall and for several specific imaging features, across a broad range of tube current levels, and requires approximately half the radiation dose to achieve diagnostic overall perceived image quality. Accordingly, MBIR should enable CT scanning with improved perceived image quality and/or reduced radiation exposure.

Ultrasonographic evaluation of malignant and normal cervical lymph nodes.

Head and neck malignancies, including squamous cell carcinoma, lymphoma, and thyroid cancer, are a major cause of morbidity and mortality worldwide and frequently present with cervical lymphadenopathy. Distinguishing normal from malignant lymph nodes is critical for accurate staging, prognosis, and determination of optimal therapeutic options. Gray-scale, power, and color Doppler ultrasonography offers an inexpensive yet effective method in identifying abnormal cervical lymph nodes. Sonographic nodal features that should be assessed include size, shape, echotexture (including microcalcifications and cystic changes), presence of an echogenic hilus, and vascularity. Although no single sonographic feature can accurately distinguish malignant from normal nodes, a combination of these characteristics can help to make this determination.

Improved sleep MRI at 3 tesla in patients with obstructive sleep apnea.

PURPOSE: To describe a real-time MR imaging platform for synchronous, multi-planar visualization of upper airway collapse in obstructive sleep apnea at 3 Tesla (T) to promote natural sleep with an emphasis on lateral wall visualization. MATERIALS AND METHODS: A real-time imaging platform was configured for sleep MR imaging which used a cartesian, partial k-space gradient-echo sequence with an inherent temporal resolution of 3 independent slices every 2 s. Combinations of axial, mid-sagittal, and coronal scan planes were acquired. The system was tested in five subjects with polysomnography-proven obstructive sleep apnea during sleep, with synchronous acquisition of respiratory effort and combined oral-nasal airflow data. RESULTS: Sleep was initiated and maintained to allow demonstration of sleep-induced, upper airway collapse as illustrated in two subjects when using a real-time, sleep MR imaging platform at 3T. Lateral wall collapse could not be visualized on mid-sagittal imaging alone and was best characterized on multiplanar coronal and axial imaging planes. CONCLUSION: Our dedicated sleep MR imaging platform permitted an acoustic environment of constant "white noise" which was conducive to sleep onset and sleep maintenance in obstructive sleep apnea patients at 3T. Apneic episodes, specifically the lateral walls, were more accurately characterized with synchronous, multiplanar acquisitions.

Sonographic evaluation of cervical lymph nodes in papillary thyroid cancer.

Sonography is the modality of choice for imaging cervical lymph nodes in patients with papillary thyroid cancer, both before surgery and for postoperative surveillance. Sonography is also an invaluable tool to guide fine-needle aspiration of abnormal nodes. Microcalcifications, cystic changes, abnormal morphology, and disordered vascularity are features of metastatic nodal involvement with papillary thyroid carcinoma and should be sought during surveillance scans as well as in targeting for fine-needle aspiration.

Quantitatively defining washout in hepatocellular carcinoma.

OBJECTIVE: Washout on delayed phase (or equilibrium phase) imaging of an arterially hyperenhancing lesion is an excellent predictor of hepatocellular carcinoma (HCC). The purpose of our study was to quantitatively define washout in pathologically proven HCC. A quantitative definition of HCC may minimize interobserver variability and facilitate more accurate diagnosis. MATERIALS AND METHODS: We identified 47 liver lesions that were hyperenhancing in the arterial phase from 24 patients who underwent triphasic MDCT as part of preoperative evaluation for liver transplantation. All HCCs were pathologically proven. Regions of interest were obtained of lesions and areas of adjacent liver on arterial, portal venous, and delayed phase images. Enhancement profiles were assessed by three radiologists. RESULTS: Of the 47 hypervascular lesions, 14 HCCs were identified. There was a statistically significant difference in percentage attenuation ratio (defined as 100 × ratio of attenuation of adjacent liver to that of the lesion) between lesions that were HCC (median percentage attenuation ratio, 121) and those that were not (median percentage attenuation ratio, 101) on delayed phase. Percentage attenuation ratio ≥ 107 on delayed phase imaging achieved maximal sensitivity (100%) with good specificity (75.8%), positive predictive value (PPV) (63.6%), and negative predictive value (NPV) (100%) in HCC detection. Percentage attenuation ratio also correlated well with radiologists' assessments of enhancement profiles of lesions (multinomial logistic regression McFadden R(2), 0.72; chi-square p, < 0.01). CONCLUSION: Our analysis of simple CT attenuation measurements indicates that percentage attenuation ratio offers excellent sensitivity, specificity, PPV, and NPV for HCC detection and very good correlation with radiologists' assessments of washout.

Heparin-induced thrombocytopenia (HIT) causing portosplenic, superior mesenteric, and splenic vein thrombosis resulting in splenic rupture and pulmonary emboli formation.

Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin administration. Of the few reported cases of HIT-associated intra-abdominal thrombosis, none to our knowledge provide multidetector-row computed tomography (MDCT) imaging findings or emphasize its utility in diagnosis. We describe a case of HIT with MDCT images demonstrating extensive intra-abdominal thrombosis and end-organ complications including splenic rupture and pulmonary emboli. This case emphasizes the potential role of MDCT in the rapid detection of HIT-related thromboembolic complications in patients with nonspecific abdominal pain.

Multidetector computed tomography triphasic evaluation of the liver before transplantation: importance of equilibrium phase washout and morphology for characterizing hypervascular lesions.

OBJECTIVE: We aim to identify the sensitivity and positive predictive value (PPV) of arterial phase imaging in detecting hepatocellular carcinoma (HCC) and determine the added value of portal venous and equilibrium phase imaging and lesion morphology characterization. METHODS: We reviewed all patients who underwent liver transplantation at our institution that had a triphasic multidetector computed tomography examination within 6 months of transplantation. Forty-seven hypervascular lesions were identified in 24 patients. Imaging findings were correlated with explant pathologic correlation. RESULTS: Hypervascularity in the arterial phase resulted in sensitivity of 87.5% and PPV of 29.8%. The presence of washout in the equilibrium phase increased the PPV to 92.9% with a slight decrease in sensitivity (81.3%). The negative predictive value of hypervascular lesions without washout in the equilibrium phase was 97.1%. There was significant correlation between larger lesions and HCC and between round lesions and HCC. CONCLUSIONS: The presence of washout in the equilibrium phase is a better indicator of malignancy.

Complicated cholecystitis: the complementary roles of sonography and computed tomography.

Acute cholecystitis is a common cause of abdominal pain in the Western world. Unless treated promptly, patients with acute cholecystitis may develop complications such as gangrenous, perforated, or emphysematous cholecystitis. Because of the increased morbidity and mortality of complicated cholecystitis, early diagnosis and treatment are essential for optimal patient care. Nevertheless, complicated cholecystitis may pose significant challenges with cross-sectional imaging, including sonography and computed tomography (CT). Interpreting radiologists should be familiar with the spectrum of sonographic findings seen with complicated cholecystitis and as well as understand the complementary role of CT. Worrisome imaging findings for complicated cholecystitis include intraluminal findings (sloughed mucosa, hemorrhage, abnormal gas), gallbladder wall abnormalities (striations, asymmetric wall thickening, abnormal gas, loss of sonoreflectivity and contrast enhancement), and pericholecystic changes (echogenic fat, pericholecystic fluid, abscess formation). Finally, diagnosis of complicated cholecystitis by sonography and CT can guide alternative treatments including minimally invasive percutaneous and endoscopic options.

Pathologic continuum of acute appendicitis: sonographic findings and clinical management implications.

Appendicitis is one of the most common causes of the acute abdomen often requiring emergent surgery. Delayed diagnosis leads to the progression of uncomplicated appendicitis to complicated (gangrenous, perforated) appendicitis, often changing clinical management. Computed tomography and ultrasound are imaging modalities of choice to preoperatively diagnose appendicitis. Recent concerns of radiation exposure and cost have renewed interest in using ultrasound as an initial, diagnostic study. A sonographic pictorial and histopathologic review of the continuum of appendicitis is presented. A comprehensive sonographic examination of the appendix should investigate the size (maximal diameter), the echogenic submucosal layer integrity, the mural color Doppler signature, the presence of a fecalith, and the periappendiceal changes. Features of an uncomplicated appendicitis include size greater than 6 to 7 mm, hyperemia on color Doppler, mural thickening, and an intact echogenic submucosal layer. Gangrenous appendicitis is characterized by loss of the echogenic submucosal layer with absent color Doppler flow. Loculated pericecal fluid, prominent pericecal fat, and circumferential loss of the submucosal layer are suggestive of perforation. Sonographic staging can triage management of appendicitis by directing urgent laparoscopic appendectomy for uncomplicated appendicitis, open appendectomy for complicated appendicitis, and conservative management (antibiotics with percutaneous drainage) for perforated appendicitis with abscess formation.

Sonography and computed tomography of the mimics of appendicitis.

There are numerous entities that can mimic acute appendicitis. Ultrasound and computed tomography are the most common first-line, cross-sectional imaging modalities in the acute care setting. Ideally, imaging will either confirm appendicitis or exclude it by identifying a normal appendix. In the latter scenario, an alternate diagnosis can frequently be established that range from genitourinary, gastrointestinal, to even abdominal wall processes. Imaging is especially helpful in cases of patients presenting with atypical signs/symptoms for acute appendicitis and those presenting with a classic presentation where an alternative diagnosis is determined. The correct diagnosis will allow the most appropriate clinical management and therapy; specifically, avoiding nonindicated surgery is essential. Common and uncommon mimics of acute appendicitis are discussed with specific attention to their sonographic and computed tomographic appearances.

In situ vaccination with a TLR9 agonist induces systemic lymphoma regression: a phase I/II study.

PURPOSE: Combining tumor antigens with an immunostimulant can induce the immune system to specifically eliminate cancer cells. Generally, this combination is accomplished in an ex vivo, customized manner. In a preclinical lymphoma model, intratumoral injection of a Toll-like receptor 9 (TLR9) agonist induced systemic antitumor immunity and cured large, disseminated tumors. PATIENTS AND METHODS: We treated 15 patients with low-grade B-cell lymphoma using low-dose radiotherapy to a single tumor site and-at that same site-injected the C-G enriched, synthetic oligodeoxynucleotide (also referred to as CpG) TLR9 agonist PF-3512676. Clinical responses were assessed at distant, untreated tumor sites. Immune responses were evaluated by measuring T-cell activation after in vitro restimulation with autologous tumor cells. RESULTS: This in situ vaccination maneuver was well-tolerated with only grade 1 to 2 local or systemic reactions and no treatment-limiting adverse events. One patient had a complete clinical response, three others had partial responses, and two patients had stable but continually regressing disease for periods significantly longer than that achieved with prior therapies. Vaccination induced tumor-reactive memory CD8 T cells. Some patients' tumors were able to induce a suppressive, regulatory phenotype in autologous T cells in vitro; these patients tended to have a shorter time to disease progression. One clinically responding patient received a second course of vaccination after relapse resulting in a second, more rapid clinical response. CONCLUSION: In situ tumor vaccination with a TLR9 agonist induces systemic antilymphoma clinical responses. This maneuver is clinically feasible and does not require the production of a customized vaccine product.

MR colonography and MR enterography.

The bowel is a common site for pathologic processes, including malignancies and inflammatory disease. Colorectal cancer accounts for 10% of all new cancers and 9% of cancer deaths. A significant decrease in the incidence of colorectal cancer and cancer death rates has been attributed to screening measures, earlier detection, and improved therapies. Virtual colonoscopy (VC), also known as computed tomography colonography, is an effective method for detecting polyps. However, in light of increasing concerns about ionizing radiation exposure from medical imaging and potential increased risk of future radiation-induced malignancies, magnetic resonance imaging (MRI) is seen as an increasingly attractive alternative. Improvements in MRI technology now permit three-dimensional volumetric imaging of the entire colon in a single breath hold at high spatial resolution, making VC with MRI possible.