Magnetic resonance imaging of pancreatic carcinoma

The authors have used MRI for investigation of 41 patients with pancreatic tumours. MR examinations were performed with 0.5 T superconductive equipment. Short TR, short TE spin echo (SE) sequences were obtained with 8 averages and 256×256 matrix. T2-weighted sequences were also acquired. T1-weighted SE sequences provided more detail, with high intrinsic contrast between the tumour and the normal pancreas; small lesions (19 smaller than 3 cm in diameter) were always detected on these images. T2-weighted SE sequences were not useful for lesion detection, due to the lower intrinsic contrast and the number of artefacts. T2-weighted sequences proved helpful for lesion characterisation in two cases of cystoadenocarcinoma only. Staging of the tumour was possible with MRI, with good assessment of local spread, lymphoadenopathy, vascular involvement and hepatic metastases. MRI of the pancreas at medium field strength can be an alternative to CT in selected cases. Offprints requests to: P.Pavone     

MR imaging in the diagnosis of pancreatic disease

MR imaging examinations of 20 patients with normal pancreas and of 38 patients with suspected pancreatic disease were analyzed retrospectively to evaluate the ability of MR imaging to depict the normal and abnormal pancreas, establish MR criteria for various pancreatic diseases, determine if MR imaging can distinguish among various pancreatic diseases, and compare the usefulness of MR imaging with CT. In all 20 patients with normal pancreas and in 34 of the 38 patients with suspected pancreatic disease excellent or good evaluation of the pancreas was achieved. A 0.35-T magnet (Diasonics MT/S) was used, and both T1- and T2-weighted images were needed. T1 and T2 relaxation times and MR signal intensities showed no specific pattern to allow consistent differentiation between normal and diseased pancreatic tissue or to distinguish between tumor and inflammation. In the 29 patients in whom MR and CT images could be compared, MR imaging and CT provided equivalent information in 20 (69%). In 4 patients (14%), MR imaging added information, and in 5 patients (17%) of cases, MR imaging yielded less information than CT. MR imaging of the pancreas was found to be superior to CT in selected instances, such as in the staging of pancreatic neoplasms (n = 4) and in the evaluation of pancreatic disease after surgery (n = 3). We conclude that, at present, MR imaging should not be used as the screening method for pancreatic disease but should be reserved as an adjunct when the information provided by CT is insufficient.     

Current status of imaging in pancreatic diseases

Recent technological developments in multidetector CT allow pancreatic imaging in a single breath-hold, which is especially valuable in obtaining isotropic three-dimensional reformations that improve our ability to provide accurate preoperative vascular mapping. Advanced MR technology allows faster imaging of pancreas, thus facilitating MR cholangiopancreatography. Use of tissue-specific MR contrast agents, endoscopic ultrasound, and positron emission tomography (PET) in pancreatic imaging has evolved considerably. This review article discusses the roles of CT, MR, endoscopic ultrasound, and PET imaging in the pancreas.     

3.0 T MRI不同脉冲序列对胰腺疾病的诊断价值

目的 探讨MRI检查不同脉冲序列对胰腺病变的诊断价值。方法 对87例临床怀疑胰腺病变的病人应用3.0 T MR设备进行检查,扫描序列包括双回波T1WI（同相位与反相位成像）、脂肪抑制T1WI（T1WI+FS）、脂肪抑制T2WI (T2WI+FS)、磁共振胆胰管水成像（MRCP）、快速多层面扰相梯度回波(FSPGR)动态增强扫描。由2名放射科医师分析不同脉冲序列的MRI所见。结果 正常胰腺15例,急性胰腺炎27例,慢性胰腺炎30例,胰腺癌15例。T1WI+FS显示胰腺形态与信号最佳,正常胰腺呈稍高信号。在双回波T1WI上,胰腺与周围组织对比度降低。胰腺病变在T1WI上表现为低信号50例,T2WI+FS显示胰周渗出性病变34例。MRCP显示胰管扩张35例,胆管扩张20例,双管征9例。快速扰相梯度回波（FSPGR）动态增强显示胰腺癌13例,肿块在动脉期表现为相对低信号,延迟期轻度强化,周围血管受侵2例。结论 合理应用MR扫描序列有助于提高胰腺病变的诊断效能。     

Adenocarcinoma of the pancreatic ducts: comparative evaluation with CT and MR imaging at 1.5 T.

A prospective comparison of computed tomography (CT) and magnetic resonance (MR) imaging at 1.5 T was performed in 50 patients with the suspected diagnosis of pancreatic carcinoma. CT scans were obtained before and after administration of contrast material in 41 of 50 patients (82%); 34 of 41 postcontrast scans (83%) were obtained with dynamic CT. MR images were interpreted without knowledge of the results of CT, ultrasound, cholangiography, or endoscopic retrograde cholangiopancreatography in 48 patients (96%). Surgical correlation of findings at CT and MR imaging was performed in 24 patients (48%) at laparotomy and in two patients (4%) at autopsy. On T1-weighted MR images, relatively diminished signal intensity of tumor compared with that of the adjacent pancreas was a consistent finding. MR imaging proved superior to CT in identification of pancreatic carcinoma (particularly in smaller intrapancreatic tumors), peripancreatic extension, vascular and portal vein invasion, and duodenal invasion. These results suggest that MR imaging of the pancreas is superior in many instances to CT in preoperative evaluation of pancreatic carcinoma.     

Preliminary results of MR imaging with superparamagnetic iron oxide in pancreatic and retroperitoneal disorders

The authors conducted a preliminary evaluation of the potential of superparamagnetic iron oxide as contrast material for delineation of the bowel. Ten patients with various pancreatic diseases and 18 patients with suspected retroperitoneal disease underwent T1- and T2-weighted MR imaging before and after contrast material was administered. Two radiologists reviewed randomized images and scored them for depiction of anatomic structures and abnormalities. In most patients, postcontrast T1-weighted images showed improved delineation of the retroperitoneal small bowel (duodenum), stomach, and pancreas. Postcontrast T2-weighted images showed improved delineation of retroperitoneal small bowel, para-aortic region, peripancreatic fat, and renal veins. There was no improvement in delineation of retroperitoneal diseases, except for lymphadenopathy, which was better seen on both T1- and T2-weighted postcontrast images. Preliminary results suggest that superparamagnetic iron oxide is a useful contrast agent for delineating some normal retroperitoneal structures, lymphadenopathy, and pancreatic disease and that it is less useful in evaluating other retroperitoneal masses.     

Pancreatoblastoma: imaging findings in 10 patients and review of the literature

PURPOSE: To describe the features of pancreatoblastoma at magnetic resonance (MR) imaging, computed tomography (CT), and ultrasonography (US). MATERIALS AND METHODS: Imaging and surgical findings in 10 patients (age range, 2-20 years; mean age, 6.8 years) with pathologically proved pancreatoblastoma were reviewed for tumor size, organ of origin, definition and quality of tumor margins, tumor heterogeneity, calcification, enhancement, ascites, biliary and/or pancreatic ductal dilatation, local invasion, adenopathy, vascular invasion, vascular encasement, metastases, and signal intensity on MR images. Results from 10 CT, seven US, and three MR imaging examinations were reviewed. RESULTS: Five of the 10 tumors were pancreatic; four others appeared to be pancreatic or hepatic. Most had well-defined margins (nine of 10), were heterogeneous (nine of 10), and enhanced (10 of 10). Other findings included calcification (two of 10), biliary and pancreatic ductal dilatation (one of 10), and ascites (three of 10). Hepatic (two patients) and pelvic (two patients) metastases were present. Adenopathy (two patients) and vascular invasion (one patient) were not identified radiologically. Tumors had low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. CONCLUSION: Pancreatoblastoma is typically a heterogeneous tumor with well-defined margins that may appear to arise from the pancreas or liver. It may behave aggressively, with localized vascular or bowel invasion or with widespread metastatic disease. Although it is rare, it should be considered in the differential diagnosis of an upper abdominal mass in a child.     

Pancreatic Castleman's disease: MR findings

Castleman's disease can involve a number of organs/tissues but generally affects the mediastinum. Occurrence of Castleman's disease in the pancreas in either form of the disease, the hyaline vascular or the plasma-cell type, is very rare, with only a few case reports in which the imaging findings were described. The MR imaging of pancreatic Castleman's disease has not been previously reported, to our knowledge. We submit the MRI findings in a patient with the plasma-cell-type of Castleman's disease, which presented as an isolated smoothly marginated pancreatic mass, hypointense on T1-weighted fat-suppressed images, isointense on T2-weighted sequences, and that after contrast material injection showed peripheral rim enhancement during the arterial phase.     

MR imaging of pancreatic lesions. Comparison of manganese-DPDP and gadolinium chelate.

RATIONALE AND OBJECTIVES: To compare manganese-DPDP-enhanced and gadolinium-DTPA-enhanced MR imaging in patients suspected of having pancreatic cancer. METHODS: Fifteen patients who underwent MR imaging for suspected pancreatic cancer and received gadolinium-DTPA took part in a clinical phase III trial in which the efficacy of manganese-DPDP for detection of pancreatic cancer was evaluated. T1-weighted gradient-echo (GRE) images with and without fat suppression were used. Signal-to-noise ratio and contrast-to-noise ratio were calculated before and after the administration of each contrast agent. Image quality was assessed using a four-step score; delineation of the normal pancreas was assessed by two readers in consensus. RESULTS: In terms of pancreatic signal-to-noise ratio, only gadolinium-DTPA-enhanced fat-suppressed and non-fat-suppressed GRE imaging showed a significant (P < 0.001) increase (72% and 61%, respectively). In the patients with a focal pancreatic lesion (n = 14), a significant increase in contrast-to-noise ratio was found only in manganese-DPDP-enhanced GRE imaging without (106%) and with (82%) fat saturation. Qualitative image analysis demonstrated a significant improvement of manganese-DPDP-enhanced fat-suppressed MR images in delineating the pancreatic parenchyma (P < 0.01) as well as pancreatic tumors (P < 0.01). CONCLUSIONS: T1-weighted manganese-DPDP-enhanced GRE imaging with fat saturation should be regarded as the most suitable combination for detecting a pancreatic lesion.     

Techniques for high-resolution echo-planar MR imaging of the pancreas.

Recent technical advances in echo-planar magnetic resonance (MR) imaging prompted an investigation of these new techniques in pancreatic MR imaging and evaluation of bowel lumen enhancement with an aqueous bowel contrast agent. In 42 subjects (36 healthy, six with pancreatic disease), various T1-weighted inversion-recovery and T2-weighted spin-echo fat-suppressed pulse sequences were assessed with an echo-planar technique implemented with a modified clinical MR imager. Single-excitation imaging (echo time, 26 msec) provided a higher (P less than .05) signal-to-noise ratio than did conventional spin-echo and all other echo-planar techniques. In 13 (72%) of 18 healthy subjects who did not undergo administration of the contrast agent, the entire pancreas was distinguished from adjoining bowel. In all 18 subjects who underwent contrast-enhanced imaging, a significantly greater (P less than .05) intraluminal signal intensity was apparent with all echo-planar pulse sequences and the entire pancreas was identified. In six patients with pancreatic disease, lesions could be identified by their difference in signal intensity.     

Liver and pancreas: improved spin-echo T1 contrast by shorter echo time and fat suppression at 1.5 T

T1-weighted spin-echo magnetic resonance (MR) images have had limited soft-tissue contrast at 1.5 T. The authors investigated the effects of echo-time (TE) minimization and fat suppression on MR images of the liver and pancreas. Two sets of MR images were obtained with identical repetition times and other parameters. In 10 subjects with seven liver lesions, images with TEs of 20 and 12 msec were compared. In 18 additional subjects with seven liver lesions and five pancreatic carcinomas, images with identical TEs but with and without fat suppression were compared. Contrast-to-noise ratios (CNRs) were greater with a TE of 12 msec than with a TE of 20 msec for liver versus spleen (7.6 vs 4.9, P = .014) and liver versus lesion (6.9 vs 3.9, P = .031). In patients without fatty liver, CNR for six lesions versus liver was greater (9.5 vs 6.0, P = .014) with fat suppression. CNR between glandular pancreas and cancer was most conspicuous with fat suppression, but fat planes were less distinct. Minimization of TE improves T1-weighted images significantly. Fat suppression also improves CNR, but the disadvantages of fat suppression do not allow elimination of conventional T1-weighted images.     

Pancreatic adenocarcinoma: detection and staging with dynamic MR imaging

OBJECTIVE: To compare the efficacy of dynamic contrast-enhanced MR imaging and spin-echo T1-weighted with and without fat-saturated MR imaging in the detection and staging of pancreatic adenocarcinoma. METHODS AND MATERIAL: Spin-echo T1-weighted, fat-saturated T1-weighted and dynamic breath-hold 2D-FLASH MR imaging were performed in 25 patients with pancreatic adenocarcinoma. MR images were analysed by calculating the CNR between tumor and normal portion of the pancreas. The CNRs calculated at each sequences were compared. A total of 16 out of 25 patients underwent surgery. Preoperative staging according to TNM classification was also done in patients undergoing surgery. RESULTS: The CNR was significantly different (P<0.05) in the arterial phase of dynamic MR images. The accuracy of 'T' staging was 75% for SE T1-W, fat-saturated T1-W and arterial phase of dynamic MR images. CONCLUSION: The CNRs between pancreatic carcinoma and normal pancreas is significantly higher in dynamic MR sequences than the SE T1-W, fat-saturated T1-W sequences. However, the accuracy of tumor staging according to TNM is equivocal to SE T1-W and fat-saturated T1-W images.     

On contrast-enhanced magnetic resonance angiography of the aortoiliac arteries

In contrast-enhanced MR angiography (CE-MRA), vascular signal is produced by the acquisition of a T1-weighted MR imaging scan while the presence of a contrast agent induces a low T1 in blood. In this thesis, CE-MRA of the aortoiliac arteries was evaluated. Different contrast agents and techniques for synchronisation of the scan with the contrast bolus passage were assessed. In 30 patients with clinically suspected iliac artery stenoses, CE-MRA was compared with duplex ultrasound scanning (DUS) and digital subtraction X-ray angiography (DSA), with intra-arterial pressure measurements as reference. No statistically significant differences in sensitivity or specificity were observed between the techniques regarding detection of haemodynamically significant iliac stenoses. The use of multiplanar reformat and source images in the MRA examinations was of value for differentiation between highgrade stenoses and occlusions. With DSA as reference method, MRA had significantly higher sensitivity and specificity than DUS for detection of > or = 50% stenoses. In 14 patients who underwent iliac artery MRA, differences in contrast arrival time of up to 7 s were observed between the aorta and the common femoral artery. A dual-station timing technique adjusting for this difference was found feasible. Compared with a fluoroscopically triggered technique (n = 13), which is used in clinical routine, the dual-station technique was more reliable for the visualisation of distal vessels. In a clinical phase II study comparing doses of the contrast agent gadobenate dimeglumine from 0.0125 to 0.2 mmol/kg b.w. for enhancement of iliac artery MRA, significant improvement in subjective diagnostic quality compared with time-of-flight-MRA was found at all doses from 0.025 mmol/kg b.w. An increasing trend with dose was observed up to a dose of 0.05-0.1 mmol/kg b.w. In a phase I clinical study on the intravascular iron oxide contrast agent NC100150 Injection, a positive dose response was observed for abdominal vascular enhancement, with the highest contrast-to-noise ratio observed at 4.0 mg Fe/kg b.w. at 1.5 T and at 2.5-4 mg Fe/kg b.w. at 0.5 T. At 1.5 T higher calculated R2* values were found for the aorta than for the inferior vena cava.     

Contrast-enhanced magnetic resonance angiography of carotid arterial wall in pigs

This study was designed to investigate the effects of contrast agents on MR images of balloon-injured carotid arteries containing atherosclerotic-like lesions. We have evaluated an intravascular contrast agent, MS-325 (METASYN INC., Cambridge, MA) and an extra-vascular contrast agent, Optimark, (Mallinckrodt Medical Inc., St. Louis, MO) on MR angiograms obtained 4 weeks after balloon hyperinflation-induced injury of the left common carotid artery in 12 hypercholesterolemic minipigs. High in-plane resolution (.8 × .4 mm²), thin slice (1 mm) time-of-flight gradient echo sequences were used to acquire the MR angiographic images. Vascular lumen definition was compared before and after a single bolus intravenous injection of a contrast agent. Digital subtraction angiograms were obtained from all pigs after MR imaging. High grade stenosis developed in 1 of the 12 pigs and five pigs had complete occlusion of the injured vessel. The remaining pigs exhibited essentially no visible stenoses as assessed either by MR angiography or digital subtraction angiography. The vessel walls of the stenosed and occluded vessels were visible after the injection of either intravascular or extravascular contrast agent. Histologic analyses showed well developed neovascularization in the neointima or occlusive thrombosis. We conclude that the observed contrast-enhanced vessel wall is caused by an increased vascular supply associated with thrombosis and neointimal thickening that leads to an accumulation of contrast agent in the abnormal vessel walls after the injection of the T1-shortening paramagnetic contrast agent.     

CT and MR imaging of advanced Zollinger-Ellison syndrome

The CT and magnetic resonance (MR) findings in 13 patients with advanced Zollinger-Ellison syndrome are described. In eight patients (62%) one or more primary tumors were found with both methods. All patients with proven liver metastases (n = 7) were identified by MR. Computed tomography was positive in six of these patients. Three patients with lymph node metastases were identified on CT and MR and one patient had bone metastases. Computed tomography and MR were inferior to selective arteriography in the detection of multiple lesions of the pancreas in a patient with multiple endocrine neoplasia-I syndrome. On the T1-weighted MR images, the primary tumors demonstrated no consistency with regard to their signal intensity relative to the adjacent pancreatic parenchyma. All gastrinomas had an increased relative signal intensity on the T2-weighted images with the exception of a calcified tumor. Liver and lymph node metastases had a low signal intensity on the T1-weighted images and an increased signal intensity on the T2-weighted images. The signal intensity of primary tumors and metastases was independent of size. In conclusion, MR was able to detect abnormalities based on its outstanding lesion/normal tissue contrast, whereas CT diagnosis was based mostly on contour distortion. For the current technique, MR is considered at least equal to CT.     

Pancreatic enhancement after low-dose infusion of Mn-DPDP

Enhancement of the pancreas was demonstrated after low-dose (10 mumol/kg) infusion of a new contrast agent for magnetic resonance (MR) imaging, manganese dipyridoxal-diphosphate (Mn-DPDP). To the authors' knowledge, this has not been described previously. The enhancement reached a maximum of 98% +/- 13% (standard deviation) during a long period (greater than 6 hours). Mn-DPDP seems to have potential as a selective contrast agent in MR imaging of the pancreas.     

Ampullary carcinoma: Demonstration by current MR techniques

The objective of this study was to demonstrate the appearance of ampullary carcinoma using current MR techniques, including fat suppression, gadolinium enhancement, and MR cholangiography. Nine patients with ampullary carcinoma were examined by MRI at 1.5 T. MR examinations included T1-weighted spoiled gradient echo, T1-weighted fat-suppressed, and immediate postgadolinium spoiled gradient echo images for all patients and MR cholangiography for three patients. The imaging features of ampullary carcinomas, including tumor size and morphology, signal intensity, and enhancement characteristics, were determined. Ampullary carcinomas shown on MR images ranged in size from 1.5 to 5.5 cm. Tumors were low in signal intensity on precontrast T1-weighted spoiled gradient echo and T1-weighted fat-suppressed images relative to normal pancreatic tissue and enhanced less than normal pancreas on immediate postgadolinium spoiled gradient echo images. Tumor conspicuity was greatest on immediate postgadolinium spoiled gradient echo images. MR cholangiography demonstrated high grade obstruction of the common bile duct and mild dilatation of the pancreatic duct at the level of the ampulla with abrupt termination of the ducts in two untreated patients and moderate dilatation of the common bile duct in one patient who had a biliary stent. Ampullary carcinomas can be demonstrated on MR images as small masses arising at the ampulla. Tumors are well defined on immediate postgadolinium spoiled gradient echo images.     

Solid-pseudopapillary tumor of the pancreas: MR imaging findings in 21 patients

PurposeSolid-pseudopapillary tumor (SPT) of the pancreas is a rare, low-grade malignancy, which mostly occurs in adolescent and young adult females. The goal of this study was to retrospectively analyze the magnetic resonance (MR) imaging presentation of SPT of the pancreas.MethodsWe retrospectively reviewed the preoperative MR imaging examinations and the medical, surgical and histopathological records of 21 patients who underwent surgery for SPT of the pancreas. MR imaging included T1-weighted, T2-weighted, and gadolinium chelate-enhanced MR imaging. In addition, 10 patients had diffusion-weighted (DW) MR imaging. MR examinations were retrospectively reviewed for location, size, morphological features and signal intensity of the tumors.ResultsNineteen women and 2 men (median age, 23 years; range, 14–59) were included. Seven patients (7/21; 33%) presented with abdominal symptoms. The median largest tumor diameter was 53mm (range, 32–141 mm). SPTs were located in the pancreatic head, body, and tail in 9 (9/21; 43%), 5 (5/21; 24%) and 7 (7/21, 33%) patients, respectively. All patients (21/21; 100%) had a single SPT. SPTs were more frequently oval (12/21; 57%), predominantly solid (12/21; 57%), fully encapsulated (16/21; 76%), larger than 30 mm (21/21; 100%), hypointense on T1-weighted MR images (21/21, 100%), hyperintense on T2-weighted MR images (21/21; 100%) and with an enhancing capsule after gadolinium-chelate administration (21/21; 100%).ConclusionsThere is trend of appearance for SPT of the pancreas on MR imaging but that variations may be observed in a number of cases. SPT uniformly presents as a single, well-demarcated and encapsulated pancreatic mass.     

Intraluminal contrast agents for MR imaging of the abdomen and pelvis

Magnetic resonance (MR) imaging of the abdomen and pelvis with use of gastrointestinal (GI) contrast agents is slowly emerging as a valuable diagnostic tool. In the past few years, considerable effort has been expended on developing an oral contrast agent to serve as a bowel marker during abdominal and pelvic imaging. Four major categories of agents have been studied: compounds with positive contrast-enhancing characteristics (ie, which increase signal intensity), which may be either miscible or immiscible with bowel contents, and compounds with negative contrast-enhancing characteristics (ie, which decrease signal intensity), which also may be miscible or immiscible. Compared with precontrast images, MR images acquired after administration of GI contrast agents have shown increased anatomic delineation of the bowel lumen, pancreas, and paraaortic nodes, allowing increased detection of pancreatic lesions, improved assessment of bowel wall lesions, and distinction between intrahepatic and extrahepatic lesions. This review focuses on the general physics and requirements for intraluminal GI contrast media for MR imaging, the currently used intraluminal agents and their regulatory status, current and near-future availability, and cost considerations.     

Pancreatic changes in primary sclerosing cholangitis: evaluation with MR imaging

OBJECTIVE: The purpose of this study was to determine the frequency and the spectrum of MR imaging findings of pancreatic abnormalities in patients with primary sclerosing cholangitis. MATERIALS AND METHODS: MR images in 24 patients with primary sclerosing cholangitis were retrospectively reviewed for evidence of pancreatic abnormalities, including abnormalities of signal intensity; changes in size and morphology; abnormalities of pancreatic ducts; presence of focal lesions, pseudocysts, and peripancreatic edema or fluid; and contrast-enhancement pattern if dynamic studies were available. RESULTS: Eleven patients with pancreatic abnormalities on MR images (case patients) and 13 patients with normal MR findings of the pancreas (cohort patients) were identified. The most common finding in case patients was increased signal intensity of the pancreas on T2-weighted images (73%), followed by decreased signal intensity on T1-weighted images (55%) and decreased enhancement on arterial-phase contrast-enhanced images (50%). Other findings included marked enlargement of the pancreas (27%), narrowing of pancreatic ducts (27%), and peripancreatic edema or fluid (27%). The mean value of the anteroposterior diameter of the pancreatic head in the case patients was significantly greater than that in the cohort patients (p = .039). The mean signal-intensity ratio on the T2-weighted images was significantly higher in the case patients than in the cohort patients (p = .007). CONCLUSION: Increased signal on T2-weighted images, decreased signal on T1-weighted images, enlargement of the pancreas, and decreased contrast-enhancement were MR findings of pancreatic disease associated with primary sclerosing cholangitis.