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The current accepted standard for quantifying shock wave lithotripsy (SWL)-induced tissue damage is based on morphometric detection of renal hemorrhage in serial tissue sections from fixed kidneys. This methodology is time and labor intensive and is tissue destructive. We have developed a non-destructive magnetic resonance imaging (MRI) method that permits rapid assessment of SWL-induced hemorrhagic lesion volumes in post-mortem kidneys using native tissue contrast to reduce cycle time. Kidneys of anesthetized pigs were targeted with shock waves using the Dornier Compact S lithotripter. Harvested kidneys were then prepared for tissue injury quantification. T1 weighted (T1W) and T2 weighted (T2W) images were acquired on a Siemens 3T Tim Trio MRI scanner. Images were co-registered, normalized, difference (T1W - T2W) images generated, and volumes classified and segmented using a Multi-Spectral Neural Network (MSNN) classifier. Kidneys were then subjected to standard morphometric analysis for the measurement of lesion volumes. Classifications of T1W, T2W and difference image volumes were correlated with morphometric measurements of whole kidney and parenchymal lesion volumes. From these relationships, a mathematical model was developed that allowed predictions of the morphological parenchymal lesion volume from MRI whole kidney lesion volumes. Predictions and morphology were highly correlated (R = 0.9691, n = 20) and described by the relationship y = 0.84x + 0.09, and highly accurate with a sum of squares difference error of 0.79%. MRI and the MSNN classifier provide a semi-automated segmentation approach, which provide a rapid and reliable means to quantify renal injury lesion volumes due to SWL.

Objective: The objective of our study was to prospectively obtain pilot data on the accuracy of MR enterography for detecting small-bowel Crohn's disease compared with CT enterography and with a clinical reference standard based on imaging, clinical information, and ileocolonoscopy., Subjects and Methods: The study group for this blinded prospective study was composed of 33 patients with suspected active Crohn's ileal inflammation who were scheduled for clinical CT enterography and ileocolonoscopy and had consented to also undergo MR enterography. The MR enterography and CT enterography examinations were each interpreted by two radiologists with disagreements resolved by consensus. The reports from ileocolonoscopy with or without mucosal biopsy were interpreted by a gastroenterologist. The reference standard for the presence of small-bowel Crohn's disease was based on the final clinical diagnosis by the referring gastroenterologist after reviewing all of the available information., Results: All 33 patients underwent CT enterography and ileocolonoscopy, 30 of whom also underwent MR enterography. The sensitivities of MR enterography and CT enterography for detecting active small-bowel Crohn's disease were similar (90.5% vs 95.2%, respectively; p = 0.32). The image quality scores for MR enterography examinations were significantly lower than those for CT enterography (p = 0.005). MR enterography and CT enterography identified eight cases (24%) with a final diagnosis of active small-bowel inflammation in which the ileal mucosa appeared normal at ileocolonoscopy. Furthermore, enterography provided the only available imaging in three additional patients who did not have ileal intubation., Conclusion: MR enterography and CT enterography have similar sensitivities for detecting active small-bowel inflammation, but image quality across the study cohort was better with CT. Cross-sectional enterography provides complementary information to ileocolonoscopy.

Objective: To determine small bowel distention, scanning time, and side effects of commercially available oral contrast agents used in cross-sectional enterography., Methods: Ten healthy volunteers ingested 2000 mL of water, methylcellulose, polyethylene glycol (PEG), or 1350 mL of low-concentration barium (LCB) followed by 500 mL water on different days. Magnetic resonance imaging occurred every 10 minutes from 30 to 90 minutes after ingestion. Small bowel distention was compared between time points and agents. Volunteers ranked side effects, drinking difficulty, and preference., Results: By quantitative assessment, PEG and LCB distended small bowel loops better than water and methylcellulose (P < 0.0001). Time to optimal distention of the terminal ileum was from 51 to 72 minutes. Water and methylcellulose had the fewest side effects. Water was the most preferred contrast and PEG the least., Conclusions: Polyethylene glycol and LCB distend small bowel better than water and methylcellulose. Polyethylene glycol was the most difficult to drink and least preferred agent.

Investigations examining the use of magnetic resonance cholangiography (MRC) for the diagnosis of primary sclerosing cholangitis (PSC) have described comparable accuracy when compared to endoscopic retrograde cholangiopancreatography (ERCP). The effectiveness of MRC based on overall cost, however, remains unknown. Our aim was to determine the average cost per correct diagnosis using MRC or ERCP as the initial testing strategy for the diagnosis of PSC. A decision analysis model was constructed employing diagnostic test parameters prospectively determined among 73 patients with clinically suspected biliary disease. ERCP was performed within 24 hours after MRC. Cost data were derived from average Medicare reimbursement fee schedules. The prevalence of PSC in the study cohort was 32%. The sensitivity and specificity of MRC for the diagnosis of PSC were 82% and 98%, respectively. The average cost per correct diagnosis of PSC was 724.00 US dollars for initial MRC (including the cost of ERCP following a negative MRC examination) versus 793.17 US dollars for initial ERCP. In the absence of biliary obstruction, the average cost per correct diagnosis of PSC was 549.64 US dollars with MRC versus 623.25 US dollars or ERCP. The average cost of managing post-ERCP-related complications among patients with PSC was 2902.20 US dollars (range, 1915.40-5031.54 US dollars). For ERCP to be the optimal initial test strategy, a prevalence rate of PSC greater than 45%, MRC specificity less than 85%, or reduction in the average cost per diagnosis to 538.30 US dollars would be required. In conclusion, MRC has comparable accuracy to ERCP and results in cost savings when used as the initial test strategy for diagnosing PSC.

Purpose: To evaluate and describe cross-sectional imaging findings in patients with pathologically confirmed primary hepatic angiosarcoma., Materials and Methods: Findings from imaging examinations in 13 patients with pathologically confirmed primary hepatic angiosarcoma were retrospectively reviewed (computed tomographic [CT] images obtained in 10 patients and magnetic resonance [MR] images obtained in five patients were available for review). Two gastrointestinal radiologists evaluated lesion number, size, attenuation and signal intensity characteristics, and the pattern and degree of contrast material enhancement. Medical records were reviewed for clinical features associated with angiosarcoma., Results: Angiosarcoma appeared as multiple nodules (n = 6), as dominant masses (n = 6), or as a diffusely infiltrating lesion (n = 1). Multiple nodules were hypoattenuating at unenhanced and contrast material--enhanced CT (six of six patients). When dominant masses were encountered at MR imaging, T2-weighted MR imaging demonstrated heterogeneous internal architecture (four of four patients) similar to that of hepatocellular carcinoma. Multiphase contrast-enhanced CT and MR images showed dominant masses to have heterogeneous and progressive enhancement (three of three patients). Clinical features associated with angiosarcoma included splenic metastases (six of 13 patients), thrombocytopenia (seven of 13 patients), disseminated intravascular coagulation (four of 13 patients), and hemolytic anemia (three of 13 patients)., Conclusion: Primary hepatic angiosarcoma exhibits a spectrum of appearances that reflect its varied pathologic features.

Background: Neuroendocrine tumors of the pancreas are uncommon neoplasms of the pancreas that can occur sporadically or in association with various syndromes such as multiple endocrine neoplasia type 1 (MEN I). Patients can present with a specific clinical syndrome related to biochemically functioning tumors or with nonspecific symptoms related to mass effect or metastases. The size, function, consistency, and malignant behavior of neuroendocrine tumors are integrally related. Imaging has a major role in the preoperative localization of the primary tumor and detection of metastases. Several techniques are available including ultrasound, endoscopic ultrasound, computed tomography (CT), MR, somatostatin receptor scintigraphy, angiography, and arterial stimulation with venous sampling; each with unique advantages and limitations. The reported performance for these techniques vary widely, and as a result, recommended imaging algorithms are controversial. Recent technical advances in ultrasound, CT, and MRI have occurred that may improve the sensitivity of some of the techniques. Further improvements are likely in the future. In this chapter we will review imaging techniques used to study the pancreas as it relates to the detection of neuroendocrine tumors, imaging findings of these tumors using various imaging modalities, and the advantages, limitations and results obtained with each technique.

Background/aim: Magnetic resonance cholangiography (MRC) is a non-invasive diagnostic procedure whose role in the management of patients with primary sclerosing cholangitis (PSC) is unclear. The aim of this study was to determine the usefulness of MRC in the evaluation of the biliary tree in patients with suspected biliary disease, and in particular, PSC., Methods: MRC and invasive cholangiography (ERCP or PTC) were both performed in 73 patients, (33 male, 40 female, mean age 56 years) with clinical and/or biochemical evidence of cholestasis. Images were interpreted by two radiologists unaware of the results of other studies., Results: Forty-two patients (58%) had benign biliary disease, including 23 patients (32%) with PSC; 9 patients (12%) had malignant biliary disease; and 22 patients (30%) had a normal biliary tree. Diagnostic quality images were obtained in 73/73 (100%) of MRC, and in 70/73 (96%) of invasive cholangiography (68 ERCP's, 2 PTC's) procedures. Using ERCP/PTC findings as the reference standard, MRC had an accuracy greater than 90% in the diagnosis of normal bile ducts, biliary dilatation, biliary obstruction, bile duct stones, and PSC. Using the final diagnosis, MRC had an overall diagnostic accuracy of 90% in the detection of biliary disease compared to 97% for invasive cholangiography. Additional diagnostic/therapeutic interventions were performed during ERCP in 73% of patients with PSC and in 43% of patients without PSC (p=0.02)., Conclusions: MRC has excellent diagnostic accuracy in the presence of biliary disease. Because of its noninvasive nature, MRC may have advantages over invasive cholangiography when diagnosis is the major goal of the procedure.

The short-term safety of mangafodipir trisodium (MnDPDP) injection was studied in 546 adults with known or suspected focal liver lesions. An initial contrast-enhanced computed tomography examination was followed by unenhanced magnetic resonance imaging (MRI), injection of MnDPDP (5 micromol/kg), and enhanced MRI. Adverse events were reported for 23% of the patients; most were mild to moderate in intensity, did not require treatment, and were not drug related. The most commonly reported adverse events were nausea (7%) and headache (4%). The incidence of serious adverse events was low (nine events in six patients) and not drug related. Injection-associated discomfort was reported for 69% of the patients, and the most commonly reported discomforts included heat (49%) and flushing (33%). Changes in laboratory values and vital signs were generally transient, were not clinically significant, and did not require treatment. There were no clinically significant short-term risks from exposure to MnDPDP.

Objective: The purpose of this study was to compare liver signal-to-noise ratio (SNR), lesion SNR, and lesion-liver contrast-to-noise-ratio (CNR) in patients with malignant liver lesions after the administration of a standard dose (0.1 mmol/kg of body weight) or a triple dose (0.3 mmol/kg) of a gadolinium chelate (gadoteridol). We hypothesized that the higher dose would produce a higher lesion-liver CNR and therefore increase the conspicuity of hepatic lesions., Materials and Methods: A total of 85 patients with malignant hepatic masses (61 metastases, 22 hepatocellular carcinomas, and two lymphomas) proved by histologic or follow-up studies underwent MR imaging at 1.5 T. T1-weighted spin-echo imaging and gradient-echo imaging were done before and within 1 min after (gradient echo) as well as 5 (spin echo) and 15 (spin echo) min after the injection of 0.1 or 0.3 mmol of gadoteridol per kg, randomized before the start of the study (39 patients received the standard dose, and 46 received the triple dose). The signal intensities of the liver and lesions and the SD of background noise were measured by use of regions of interest to calculate the SNR of the liver and malignant lesions and the lesion-liver CNR., Results: The lesion-liver CNR was increased significantly at 5 and 15 min after the administration of gadoteridol. No significant differences in the liver SNR, lesion SNR, and lesion-liver CNR (after 1 min: standard dose, -5 +/- 8, and triple dose, -4 +/- 14; after 5 min: standard dose, -1 +/- 5, and triple dose, 2 +/- 8; and after 15 min: standard dose, 1 +/- 5, and triple dose, 6 +/- 20) were found between the doses at all time points., Conclusion: Triple-dose gadoteridol does not improve the lesion-liver contrast of malignant hepatic lesions over that provided by the standard dose and is not warranted for liver MR imaging.

Purpose: To prospectively compare use of a phased-array multicoil and a conventional body coil in abdominal MR imaging., Materials and Methods: Thirteen patients (seven men, six women; mean age, 55 years) underwent imaging with a phased-array multicoil and with a conventional body coil. Four pulse sequences were used: T2-weighted spin echo (SE), magnetization-prepared gradient-recalled echo (GRE), breath-hold fast SE, and echo planar (EP)., Results: Lesion detection improved the most on fast SE, multicoil-acquired images. Signal-to-noise ratio (S/N) increased 64% with fast SE (P = .0005) and EP (P < .0109) sequences. Contrast-to-noise ratio (C/N) doubled (P < .05) with T2-weighted SE sequences. Lesion conspicuity improved on multicoil-acquired images with all fast sequences (magnetization-prepared GRE, P = .015; fast SE, P = .002; EP imaging, P = .013). There was little difference in respiratory and vascular artifact. Depiction of most abdominal structures improved (P < .01)., Conclusion: Use of the phased-array multicoil provides better MR images of the abdomen than does use of a conventional body coil.

Purpose: To determine if hepatic metastases can be distinguished from cavernous hemangiomas by pattern analysis of magnetic resonance (MR) images obtained prior to and following administration of gadoteridol at standard (0.1 mmol/kg) and triple (0.3 mmol/kg) doses., Materials and Methods: Ninety-five patients with proved hepatic metastases (n = 71) or cavernous hemangiomas (n = 24) underwent MR imaging at 16 different institutions. T2-weighted spin-echo and T1-weighted images were obtained before and after gadoteridol administration. Two independent blinded reviewers rated individual features of benignancy versus malignancy on a five-point confidence scale., Results: The most useful diagnostic features, with 100% specificity, were nodular enhancement for hemangiomas and rim enhancement for metastases. Confident (definitely benign or definitely malignant) diagnoses were rendered in 80 of 95 cases (84%), with an accuracy of a confident diagnosis of 96%., Conclusion: The pattern of enhancement on T1-weighted images is highly accurate for distinction between hemangiomas and metastases in images obtained with both doses.

Objective: The purpose of this study was to construct a method of vessel edge detection that correctly identifies vessel pixels and to compare the interuser variability of cine phase contrast MR volumetric flow rates obtained with the conventional manual method and an automated method., Materials and Methods: The automated method was developed based on a magnitude image threshold value and compared with the manual method in a flow phantom (three users) and in velocity images of the portal vein (five users). The threshold value determined from the magnitude image was applied to a region of interest surrounding the vessel of interest on the magnitude image to construct a vessel edge detection mask m(x,y). The velocity images were then multiplied by the mask m(x,y) and volumetric flow rates determined using the identified vessel pixels., Results: In the flow phantom, flow measurements with the magnitude threshold method had significantly less interuser variability compared with the manual method (p < 0.01) and were within 10% (mean 6.0%) of the actual flow versus 35% (mean 18.6%) with the manual method. Regarding flow measurements in the portal vein of six volunteers, the magnitude threshold method was significantly more precise (p < 0.01) than the manual method with a mean standard deviation between the five users of 40.4 +/- 12.9 ml/min (range 22-60 ml/min) and 110.4 +/- 32.7 ml/min (range 70-155 ml/min), respectively., Conclusion: The magnitude threshold method of vessel edge detection developed in this study yields flow measurements that are accurate in the model system and have significantly less interuser variability than the manual method. This method shows promise for improving the precision of cine phase contrast flow measurements.

Objective: The purpose of this study was to determine if a consistent relationship exists between (1) flow in the portal vein and superior mesenteric vein and (2) flow in the mesenteric arteries., Subjects and Methods: Cine phase-contrast methods were used to determine volumetric flow in the celiac axis, superior mesenteric artery, portal vein, and superior mesenteric vein in 11 healthy volunteers., Results: The mean (+/- SD) volumetric flow rates in the celiac axis, superior mesenteric artery, superior mesenteric vein, and portal vein were 9.9 +/- 3.2, 6.0 +/- 1.8, 5.7 +/- 2.0, and 13.7 +/- 1.8 ml/min per kilogram, respectively. A strong correlation was found between measured mesenteric arterial blood flow, defined as the sum of flow in the celiac axis and the superior mesenteric artery, and portal venous flow (r = .97, p = .00002). Good agreement was found between flow in the superior mesenteric artery and that in the superior mesenteric vein (r = .98; p = .00001; bias = 20 ml/min)., Conclusion: There is a consistent relationship between MR measurements of flow in the portal or superior mesenteric vein and the measured flow in the arteries supplying those veins. Flow in the superior mesenteric vein is an accurate predictor of flow in the superior mesenteric artery.

Purpose: To evaluate the efficacy and safety of two dose levels of an orally administered ferric ammonium citrate-based contrast agent for bowel enhancement on T1-weighted spin-echo magnetic resonance (MR) images in 222 patients with known or suspected abnormality of the upper abdomen., Materials and Methods: Adverse reactions were graded for intensity, frequency, duration, and relationship to the contrast agent. Twelve unblinded readers compared enhanced with unenhanced images; all MR images were evaluated by two independent offsite radiologists in a blinded review., Results: No statistically significant changes in mean vital signs or laboratory values were seen. Forty-eight of 220 patients (22%) reported minor side effects. The readers found increased intraluminal signal intensity and improved contrast enhancement of the gastrointestinal tract and distention and improved signal homogeneity in 101-107 cases (89%-98%) after ingestion; the blinded reviewers' findings were similar., Conclusion: The contrast agent provided new or additional radiologic information in 142 patients (64%), specific additional information in a detected abnormality in 46 of 142 patients (32%), and information that changed diagnosis, management, or surgical approach in 22 of 142 patients (15%).

Thirty-two patients with portal venous hypertension and endoscopically proved esophageal varices who were being evaluated for possible liver transplantation were studied with cine phase-contrast magnetic resonance (MR) imaging. Flow measurements in the main portal vein were obtained and associated with the presence of variceal hemorrhage within 2 years before the MR examination. Low (hypodynamic) flow was present in 22 patients, while high (hyperdynamic) flow was present in 10 patients. The presence of variceal hemorrhage was significantly associated with a high portal venous flow rate (P = .001), high variceal grade (P = .030), and Child class A or B (P = .003); however, only portal venous flow (P = .006) and variceal grade (P = .044) were found to be associated with variceal hemorrhage in a multiple logistic regression analysis. The portal venous flow rate was significantly higher among patients with Child class A or B disease compared with those with class C disease (median, 24.6 vs 8.0 mL/min.kg; P = .004).

Objective: The purpose of this study is to report the spectrum of MR findings of pancreatic islet cell carcinoma., Materials and Methods: The MR scans of 33 patients with islet cell carcinoma were retrospectively reviewed. Magnetic resonance detected the primary tumor in 21 of 27 patients (78%) who had not had prior resection of their primary tumor. Mean tumor diameter was 7.1 cm (range 3.5-13.0 cm)., Results: In all patients, the primary tumor on T1-weighted images (TR/TE = 250/15) was of signal intensity equal to or lower than that of the adjacent normal pancreas. The primary tumor on T2-weighted images (TR/TE = 2,000/> or = 100) was of signal intensity the same as or higher than fat in 18 of 21 patients (86%) and had mixed signal intensity in the other 3 (14%). Hepatic metastases were found in 28 of 33 patients (85%). Liver metastases were categorized as "usual" (variably circumscribed, homogeneous lesions of medium signal intensity on T2-weighted images) in 19 of 28 patients (68%), necrotic in 8 of 28 (29%), hemorrhagic in 3 of 28 (11%), and calcified in 1 of 28 (4%). Extrahepatic metastases were found in 18 of 33 patients (55%)., Conclusion: We conclude that MRI is an excellent modality for the diagnosis and routine follow-up of patients with islet cell carcinoma.

Thirty-one patients with portal venous hypertension underwent phase-contrast cine magnetic resonance (MR) angiography to validate the technique for assessment of main portal vein patency and blood flow direction. Correlative findings from Doppler ultrasonography, conventional angiography, and surgery were acquired in 30, 17, and 16 patients, respectively. Findings from MR angiography correlated well with those of the other methods for determining portal vein patency and flow direction. The main portal vein was patent in 29 patients and was thrombosed in two patients at MR angiography. With the use of a 40-mm slab projection acquisition that required 5 minutes, the splenic and superior mesenteric veins, as well as extensive varices (when present), were seen in the majority of cases. Phase-contrast cine MR angiography is an accurate method of rapidly assessing morphologic characteristics, patency, and flow direction of the portal venous system and thus is a useful method for evaluating the condition of patients with chronic liver disease.

Objective: The purposes of this study were to (1) validate the accuracy of cine phase-contrast MR flow measurements within the portal vein, (2) develop a suitable protocol for using this method to measure volumetric flow rate in the portal venous system, and (3) use this protocol, with Doppler sonography as a reference, to measure portal venous flow in healthy volunteers and in patients with protal venous hypertension., Subjects and Methods: Flow determinations were obtained in a model of fluid movement approximating blood-flow conditions in the portal venous system. A suitable protocol was based on consideration of the theoretical effects of (1) spatial resolution, (2) obliquity of the imaging plane to the direction of flow, and (3) signal-to-noise ratio of the signed quantitative velocity images (in three volunteers) on the accuracy and precision of flow measurements. This protocol was used to obtain cine phase-contrast MR images of the portal venous system in five volunteers and six patients., Results: Values obtained with a flow phantom showed good accuracy of cine phase-contrast-measured vs actual volumetric flow rate (r = .995; p = .0001; MR rate = [0.94 x actual rate] + 65.6 ml/min; standard error of the y estimate = 67.3 ml/min). Velocity encoding and section thickness substantially influenced the signal-to-noise ratio of the velocity images, whereas flip angle and matrix size had only minimal effect. In volunteers and patients, portal volumetric flow rates determined by using MR images and Doppler sonography showed good correlation (r = .94; p = .0003)., Conclusion: Our results indicate that cine phase-contrast MR imaging is a practical noninvasive method for measuring volumetric flow rates in the portal venous system.

Magnetic resonance imaging provides excellent anatomic depiction of the liver and important information about focal and diffuse diseases that affect this organ. In this report, the current clinical applications of magnetic resonance imaging of the liver in patients with known or suspected hepatic metastatic lesions, hepatocellular carcinoma, cavernous hemangiomas, focal fatty infiltration, focal nodular hyperplasia, hepatic adenoma, regenerative nodules in hepatic cirrhosis, or iron overload are reviewed, and the limitations of the technique are discussed.

Magnetization-prepared ultrashort-repetition-time (snapshot) gradient-echo imaging is a technique of magnetic resonance (MR) imaging with many potential applications. In the application of this technique to abdominal imaging, the effects on contrast of phase-encoding order, resolution, preparation-phase inversion time, and data-acquisition flip angle were predicted and then demonstrated with images obtained in examinations of 22 patients. In the analysis of 36 liver lesions, snapshot images were compared with corresponding T1-weighted spin-echo images on the basis of signal-to-noise ratio (S/N) of liver and contrast-to-noise ratio (C/N) between liver and lesion. Snapshot MR imaging produced abdominal images with 192 (or 256) x 256 resolution, negligible motion artifact, and C/N 1.29 times (+/- 0.48) higher than that in T1-weighted spin-echo imaging. Acquisition times were 13 seconds or less, short enough for imaging during suspended respiration. Also, use of a phased-array multicoil further improves the S/N in snapshot images without acquisition-time penalty.

This study was performed to compare time-of-flight MR angiography in detecting varices with conventional portography and endoscopy in patients with chronic liver disease and to compare MR tomographic images with projection angiograms. In eight patients findings on conventional arterial portography (considered the gold standard) were compared with the MR findings. Varices were graded by size and extent on a scale of 0-3. Splenic varices were detected in all patients by MR but were scored larger on portography in 6 (55%) of 11 comparisons. All left gastric varices were identified at MR and were rated within one grade of those seen at portography. All esophageal varices were identified at MR. Among 12 patients with upper endoscopy, MR rated varices significantly (p less than 0.05) larger than endoscopy in 8 (67%) of 12 comparisons. Varices were detected in two patients on MR that were not seen endoscopically. Extraperitoneal varices were identified in six (75%) of eight patients on MR and were only visualized in one patient at portography. Varices were equally well detected using either axial or coronal images. No significant difference existed when tomographic images were compared with projection images. Time-of-flight MR angiography is a valid technique for noninvasive imaging of abdominal varices. Tomographic single slice images are generally as good as projection images except possibly in the demonstration of extraperitoneal varices.