Derek G. Lohan

Prevalence and significance of asymptomatic venous thromboembolic disease found on oncologic staging CT.

OBJECTIVE The purpose of our study was to determine the prevalence of unsuspected venous thromboembolic disease--specifically, of pulmonary embolism (PE) and of inferior vena cava (IVC), iliac, and iliofemoral deep venous thromboses (DVTs)--in oncology patients on staging CT scans of the thorax, abdomen, and pelvis. MATERIALS AND METHODS Retrospective analysis was performed on 435 consecutive staging CT thorax, abdomen, and pelvis scans performed on a variety of oncology patients for the presence of venous thromboembolic disease. The patient group consisted of 198 men and 237 women who ranged in age from 20 to 79 years (mean, 55 years). Disease type, stage, concomitant surgery or chemoradiation therapy regimes, anticoagulation status, and 6-month clinical and radiologic follow-up findings were recorded. RESULTS We found a prevalence of 6.8% (23/339) unsuspected iliofemoral, 1.2% (4/339) unsuspected common iliac, and 0.3% (1/315) unsuspected IVC DVTs and 3.3% (13/397) unsuspected PEs occurring in patients with a wide range of malignancies. The overall prevalence of unsuspected venous thromboembolism (i.e., DVT, PE, or both) was 6.3% (25/397). DVT, PE, and venous thromboembolic disease were more common in inpatients (p = 0.002, 0.004, 0.023; relative risk [RR] = 1.6, 2.1, 1.4, respectively) and in those with advanced disease (p = 0.001, 0.01, 0.001; RR = 2.2, 1.8, 2.0, respectively). CONCLUSION Although there is a known increased risk of thromboembolism (DVT and PE) in oncology patients, many cases are not diagnosed, which can prove fatal. Staging CT simultaneously affords one sole investigation of the pulmonary, IVC, iliac, and upper femoral veins, thereby providing an important diagnostic opportunity. Assessment for DVT and PE is important when reviewing staging CT scans.

Retroperitoneal Fibrosis: A Review of Clinical Features and Imaging Findings

OBJECTIVE Retroperitoneal fibrosis is a rare collagen vascular disorder of unclear cause. Both benign and malignant associations have been described, rendering differentiation of these entities of paramount importance because sinister pathology alters the diagnosis. Thus, a high level of diligence is required in the investigation of this condition, particularly in patients with concomitant systemic conditions. CONCLUSION Familiarity with the realm of imaging manifestations of retroperitoneal fibrosis is vital to ensure correct diagnosis and optimal treatment.

MR Enterography of Small- Bowel Lymphoma: Potential for Suggestion of Histologic Subtype and the Presence of Underlying Celiac Disease

OBJECTIVE The objective of our study was to evaluate the morphologic appearances of small-bowel lymphoma using MR enterography to identify key morphologic traits capable of providing an association between imaging manifestations and likely histologic diagnosis. MATERIALS AND METHODS Over a 54-month period, 10 patients with subsequently confirmed small-bowel lymphoma were imaged using a standardized MR enterography technique. Retrospective chart review was performed to detect associated disease processes, such as celiac disease. The morphologic characteristics of each segment with lymphomatous involvement were evaluated with respect to tumor location, tumor size, mural characteristics, fold features, loop dilatation, luminal stricturing, mesenteric or antimesenteric distribution, mesenteric involvement, and signal intensity. RESULTS Nineteen distinct segments of lymphomatous involvement were identified in 10 patients, and underlying celiac disease was confirmed in six of the 10 patients. This patient group comprised 10 patients with non-Hodgkins lymphoma (NHL) of various subtypes. No cases of Hodgkins lymphoma were encountered. Analysis revealed celiac NHL enteropathy to have a tendency toward localization to a single, long (> 10 cm), smooth continuous bowel segment, often with aneurysmal loop dilatation, in the absence of a distinct mesenteric or antimesenteric distribution. Luminal stricturing was encountered in cases of low-grade lymphoma, whereas mesenteric fat infiltration represented a characteristic of high-grade disease. CONCLUSION We describe the characteristics of small-bowel lymphoma on MR enterography, identifying a number of key features that may help the interpreting radiologist in suggesting the underlying histologic subtype and whether the presence of underlying celiac disease is likely.

MRI Small-Bowel Follow-Through: Prone Versus Supine Patient Positioning for Best Small-Bowel Distention and Lesion Detection

OBJECTIVE The purpose of this study was to assess whether prone or supine imaging provides superior small-bowel loop distention during MRI small-bowel follow-through examinations and whether either position is better with regard to lesion detection and evaluation. SUBJECTS AND METHODS Forty consecutively enrolled clinically referred patients with known or suspected small-bowel abnormalities prospectively underwent 62 MRI small-bowel follow-through examinations in both the prone and the supine positions. Images were blindly and independently reviewed by two observers. Each small-bowel segment was assessed with a 3-point scoring system, and differences in bowel distention in the prone and supine positions were evaluated with a paired Wilcoxons test. Differences between rates of lesion detection and characterization (e.g., ulceration, stricturing) were analyzed with a paired Students t test. Interobserver agreement was estimated with the kappa coefficient. RESULTS In both normal and diseased small bowel, the prone position had statistically significantly higher distention scores than did the supine position (p < 0.05) with a high level of interobserver agreement. This finding, however, did not translate into improved lesion detection or characterization (p > 0.05). CONCLUSION Although use of the prone position results in superior small-bowel distention during MRI small-bowel follow-through, both the prone and supine positions are equal in terms of lesion detection and feature visualization.

Normal small bowel wall characteristics on MR enterography

PURPOSE To assess the normal small bowel parameters, namely bowel diameter, bowel wall thickness, number of folds (valvulae connivientes) per 2.5 cm (in.), fold thickness and interfold distance per small bowel segment (duodenum, jejunum, proximal ileum, distal ileum and terminal ileum) on MR enterography. MATERIALS AND METHODS Between September 2003 and January 2008, 280 MR enterography examinations were performed for investigation of known or suspected small bowel pathology. 120 of these examinations were normal. Sixty-five (m=29, f=36, mean age=34 years, range=17-73 years) of 120 examinations without a prior small bowel diagnosis, with no prior or subsequent abnormal radiology or endoscopy examinations, no prior small bowel surgery and with a minimum 3 years follow-up demonstrating normality were retrospectively evaluated for the described small bowel parameters. RESULTS We found the mean diameter of the duodenum to be 24.8mm (S.D.=4.5mm), jejunum to be 24.5mm (S.D.=4.2mm), proximal ileum to be 19.5mm (S.D.=3.6mm), distal ileum to be 18.9 mm (S.D.=4.2mm) and terminal ileum to be 18.7 mm (S.D.=3.6mm). The number of folds per 2.5 cm varied from 4.6 in the jejunum to 1.5 in the terminal ileum. The fold thickness varied from 2.1mm in the duodenum to 1.8mm in the terminal ileum. The small bowel parameters gradually decreased in size from the duodenum to the smallest measurements which were in the terminal ileum. The bowel wall is similar in size throughout the small bowel measuring 1.5+/-0.5mm. CONCLUSION These results provide the mean, range of normality and standard deviation of the small bowel parameters per segment on the current population on MR enterography. From our experience, knowledge of these parameters is extremely helpful and essential in the everyday assessment of MR enterography studies.

High-spatial-resolution lower extremity MR angiography at 3.0 T: contrast agent dose comparison study.

PURPOSE To determine whether contrast material dose reduction at 3.0 T allows preserved image quality for high-spatial-resolution magnetic resonance (MR) angiography of the lower extremities. MATERIALS AND METHODS Forty-five consecutive patients (27 men, 18 women; mean age, 64 years) underwent contrast material-enhanced MR angiography of the lower extremities at 3.0 T. A waiver of informed consent was granted by the institutional review board. Sixteen patients received high-dose (approximately 0.3 mmol/kg), 15 received intermediate-dose (approximately 0.2 mmol/kg), and 14 received low-dose (approximately 0.1 mmol/kg) gadopentetate dimeglumine during a three-station, dual-injection examination. For scoring purposes, the arterial system from the celiac trunk to the plantar arteries was divided into 34 segments. The images were retrospectively and independently evaluated by two specialized radiologists who were blinded to the patient dose groups. All studies were assessed for overall image quality and the degree of contaminating venous enhancement. Each arterial segment was scored for the quality of vessel definition, the severity of stenoses, and the presence of collateral vessels. RESULTS More than 99% of arterial segments were found to be of diagnostic image quality by both readers in all dose groups. Generalized estimating equation analysis showed a significant difference among the three groups with regard to vessel definition (P = .019). No significant difference was found between the high- and intermediate-dose groups; however, the low-dose group had significantly better vessel definition compared with the high-dose (P = .034) and intermediate-dose (P = .015) groups. There was no significant difference among the groups in visualization of collateral vessels. Venous contamination was seen less frequently in the low-dose group, but the difference did not achieve significance. CONCLUSION The study showed that, compared with widely used dose strategies at 1.5 T, the contrast agent dose for 3.0-T lower extremity MR angiography can be reduced multifold without compromising image quality.

Imaging of the complications of laparoscopic cholecystectomy

Laparoscopic cholecystectomy has, in recent years, emerged as the gold standard therapeutic option for the management of uncomplicated symptomatic cholelithiasis. Each year, up to 700,000 of these procedures are performed in the United States alone. While the relative rate of post-procedural complications is low, the popularity of this method of gallbladder removal is such that this entity is not uncommonly clinically encountered, and therefore must be borne in mind by the investigating physician. By way of pictorial review, we explore the radiological appearances of a variety of potential complications of laparoscopic cholecystectomy. The radiological appearances of each shall be illustrated in turn using several imaging modalities, including ultrasound, computed tomography, MR cholangiography and radio-isotope scintigraphy. From calculus retention to portal vein laceration, bile duct injury to infected dropped calculi, we illustrate numerous potential complications of this procedure, as well as indicating the most suitable imaging modalities available for the detection of these adverse outcomes. As one of the most commonly performed intra-abdominal surgeries, laparoscopic cholecystectomy and the complications thereof are not uncommonly encountered. Awareness of the possible presence of these numerous complications, including their radiological appearances, makes early detection more likely, with resultant improved patient outcome.

Low-dose, time-resolved, contrast-enhanced 3D MR angiography in cardiac and vascular diseases: correlation to high spatial resolution 3D contrast-enhanced MRA

AIM To evaluate the effectiveness of low-dose, contrast-enhanced, time-resolved, three-dimensional (3D) magnetic resonance (MR) angiography (TR-MRA) in the assessment of various cardiac and vascular diseases, and to compare the results with high-resolution contrast-enhanced MRA (CE-MRA). MATERIALS AND METHODS Thirty consecutive patients underwent contrast-enhanced 3D TR-MRA and high spatial resolution 3D CE-MRA for evaluation of cardiac and thoracic vascular diseases at 1.5 T, and neurovascular, abdominal and peripheral vascular diseases at 3T. Gadolinium-based contrast medium was administered at a constant dose of 5 ml for TR-MRA, and 20 ml (lower extremity 30 ml) for CE-MRA. Two readers evaluated image quality using a four-point scale (from 0=excellent to 3=non-diagnostic), artefacts and findings on both datasets. Interobserver variability was tested with kappa coefficient. RESULTS The overall image quality for TR-MRA was in the diagnostic range (median 0, range 0-1; k=0.74). Readers demonstrated important additional dynamic information on TR-MRA in 28 of 30 patients (k=0.84). Confident evaluation of organ perfusion (n=23), arteriovenous malformation/fistula flow patterns (n=7), exclusion of intra-cardiac shunts (n=6), and assessment of stent and conduit patency (n=5) were performed by both readers using TR-MRA. Readers demonstrated fine vascular details with higher confidence in 10 patients on CE-MRA. Using CE-MRA, Reader 1 and 2 depicted anatomical details in 6 and 5 patients, respectively, only on CE-MRA. CONCLUSION Low-dose TR-MRA yields rapid and important functional and anatomical information in patients with cardiac and vascular diseases. Due to limited spatial resolution, TR-MRA is inferior to CE-MRA in demonstrating fine vascular details.

Ultra-low-dose, time-resolved contrast-enhanced magnetic resonance angiography of the carotid arteries at 3.0 tesla.

Purpose:To determine whether time-resolved magnetic resonance angiography (TR-MRA) with ultra-low-dose gadolinium chelate (1.5–3.0 mL) can reliably detect or rule out hemodynamically significant disease in the carotid-vertebral artery territory. Materials and Methods:Hundred consecutive patients (62 women, 38 men, mean age = 56.6 years) underwent both TR-MRA and standard high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA), having been randomized to 1 of 2 groups; group A receiving a contrast dose of 1.5 mL for TR-MRA and group B receiving 3.0 mL. For scoring purposes the arterial system was divided into 21 segments. All TR-MRA and CE-MRA studies were blindly assessed by 2 radiologists for overall image quality, segmental arterial visualization, grading of arterial stenosis/occlusion, and incidence and severity of artifact. TR-MRA findings were directly compared with those of the corresponding CE-MRA examinations. Results:Group A TR-MRA studies were of significantly inferior overall image quality compared with those of the corresponding CE-MRA examinations (P = 0.01 for both observers). In group B, overall image quality was similar for TR-MRA and single-phase CE-MRA examinations. On a segmental basis, a higher number of “insufficient quality” segments were identified in group A TR-MRA studies than in group B. A similar reduction in the incidence of artifacts was observed for group B relative to group A TR-MRA studies. Both groups A and B TR-MRA studies were of high specificity, negative predictive values, and accuracy (>97%). Conclusion:Ultra-low dose TR-MRA may be performed with 3 mL of gadolinium chelate with preservation of overall image quality and arterial segmental visualization relative to single phase CE-MRA, whereas a 1.5 mL contrast dose is associated with more suboptimal studies. Nonetheless, even at doses as low as 1.5 mL, TR-MRA can exclude arterial stenosis or occlusion.

Supraaortic Arteries: Contrast Material Dose Reduction at 3.0-T High-Spatial-Resolution MR Angiography—Feasibility Study

PURPOSE To evaluate and compare the diagnostic image quality resulting from three contrast agent dose regimens for 3.0-T high-spatial-resolution three-dimensional magnetic resonance (MR) angiography of the supraaortic arteries. MATERIALS AND METHODS Institutional review board approval was obtained; informed consent was waived for this HIPAA-compliant study. One hundred twenty consecutive patients who underwent 3.0-T three-dimensional high-spatial-resolution contrast material-enhanced MR angiography of the supraaortic arteries with an identical acquisition protocol were assigned to either the high-dose (0.154 mmol per kilogram of body weight), intermediate-dose (0.097 mmol/kg), or low-dose (0.047 mmol/kg) group. Two readers evaluated resulting images for arterial definition, venous contamination, and arterial stenosis. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated at six consistent sites. Statistical analysis was performed with the Kruskal-Wallis, Wilcoxon signed rank, and analysis of variance tests and the kappa coefficient. RESULTS Readers 1 and 2 scored vascular definition as excellent or sufficient for diagnosis in 1311 of 1360 segments and in 1313 of 1360 segments in the high-dose group (kappa = 0.73), in 1321 of 1354 and in 1319 of 1354 segments in the intermediate-dose group (kappa = 0.77), and in 1322 of 1350 and in 1320 of 1350 segments in the low-dose group (kappa= 0.66), respectively. Arterial occlusive disease was detected by reader 1 in 52, 27, and 98 segments in the high-, intermediate-, and low-dose groups, respectively. Arterial occlusive disease was detected by reader 2 in 48, 25, and 100 segments in high-, intermediate-, and low-dose groups, respectively. No significant difference existed among the three groups regarding arterial definition scores (reader 1, P = .21; reader 2, P = .25) and venous contamination scores (reader 1, P = .38; reader 2, P = .35). SNRs and CNRs were lower in the low-dose group (P < .01). CONCLUSION At 3.0 T, high-spatial-resolution MR angiography of the supraaortic arteries can be performed with contrast agent doses as low as 0.047 mmol/kg, without compromising image quality, acquisition speed, or spatial resolution. SUPPLEMENTAL MATERIAL http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC1http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC2.