Intraductal papillary mucinous tumors of the pancreas. Comparison of helical CT and MR imaging

PURPOSE: To compare the effectiveness of thin-section helical CT and MR imaging with gadolinium-enhanced dynamic technique and MR cholangiopancreatography (MRCP) in the examination of patients with intraductal papillary mucinous tumors. MATERIAL AND METHODS: Helical CT, dynamic MR imaging, and MRCP of 25 intraductal papillary mucinous tumors were compared with ERCP and surgical findings. RESULTS: The duodenal papilla was identified by helical CT and dynamic MR imaging in 11 (44%) and 20 (80%) of the 25 patients, respectively (p<0.05). The main pancreatic duct was visualized on helical CT, dynamic MR imaging, and MRCP in all patients (100%): 25 (96.2%), 24 (92.3%), and 26 (100%) cystic lesions were depicted, respectively. A communicating duct between the main pancreatic duct and the cystic lesion was visualized on helical CT, dynamic MR imaging, and MRCP in 14 (53.8%), 11 (42.3%), and 15 (55.7%) lesions, respectively. The papillary projections corresponding to 3 mm or larger papillary neoplasms were depicted on helical CT and MR imaging in 7 patients (25%). CONCLUSION: MR imaging was equal or slightly superior to thin-section helical CT in the evaluation of intraductal papillary mucinous tumors.     

Rhabdomyolysis: magnetic resonance imaging and computed tomography findings

OBJECTIVE: Our purpose was to describe the magnetic resonance (MR) imaging and computed tomography (CT) findings in patients with rhabdomyolysis. METHODS: The medical records and imaging studies of 10 patients (5 males, 5 females; age range, 14-60 years; mean age, 28.3 years) with rhabdomyolysis were retrospectively reviewed. Magnetic resonance imaging was available in 9 patients and CT in 2 patients. RESULTS: Two distinct imaging types of rhabdomyolysis were observed. For type 1 rhabdomyolysis (n = 2), the affected muscles revealed homogeneously isointense to hyperintense on T1-weighted, homogeneously hyperintense on T2-weighted and short-tau inversion recovery (STIR) images, and homogeneously enhanced on contrast-enhanced MR images. For type 2 rhabdomyolysis (n = 8), the affected muscles revealed homogeneously or heterogeneously isointense to hyperintense on T1-weighted images, heterogeneously hyperintense on T2-weighted and STIR images, heterogeneously hypodense on CT images, and rim enhanced on contrast-enhanced MR and CT images with the presence of a specific presentation, named as the "stipple sign." CONCLUSIONS: Rhabdomyolysis is a clinical and biochemical syndrome comprising 2 distinct imaging types. Homogeneous signal changes and enhancement in the affected muscles advocate type 1 rhabdomyolysis. The stipple sign is helpful in demonstrating the areas of myonecrosis in type 2 rhabdomyolysis and, together with clinical and laboratory presentations, in reaching the correct diagnosis.     

Gastroenteropankreatische endokrine Tumoren

Clinical/methodical issue

Gastroenteropancreatic neuroendocrine tumors (GEP-NET) are a rare, heterogeneous group of neoplasms. Only 2?% of gastrointestinal tumors belong to the group of neuroendocrine neoplasms.

Standard radiological methods

A wide spectrum of diagnostic imaging modalities is available: apart from ultrasound not only computed tomography (CT) but also magnetic resonance imaging (MRI) and positron emission tomography CT (PET-CT) play an important role in detection and staging of GEP-NETs.

Methodical innovations

The PET-CT technique with somatostatin analogues is used for staging as well as for evaluation and monitoring of treatment with peptide radionuclide radiation therapy.

Performance

According to the literature NETs of the small bowel with a size over 3 cm can be detected with a sensitivity of 84.7?% and a specificity of 96.6?% using CT enteroclysis and MR enteroclysis provides the detection of NETs of the small bowel in 93.3?% of cases. ’The sensitivity of MRI in detection of pancreatic NETs is between 74?% and 100?% and is, therefore, higher than CT. Detection of small primary tumors is carried out using PET-CT and seems to be the most sensitive imaging modality to identify the exact location. On the other hand MRI has to be regarded as the best imaging modality for detection of liver metastases compared to CT and PET-CT.

Achievements

The role of diagnostic imaging is to identify the exact location of the primary tumor and possible metastases, to define an appropriate therapy and to monitor treatment effects; however, the choice of the most appropriate diagnostic imaging modality varies depending on the location and type of the primary tumor.

Practical recommendations

The GEP-NETs are predominantly well-vascularized; therefore, dual-phase CT/MR imaging with the arterial and venous phases after contrast media injection is mandatory for detection and localization of primary tumors and metastases. For whole body staging CT and PET-CT should be performed.     

CT and MRI features of pure acinar cell carcinoma of the pancreas in adults

OBJECTIVE: We sought to describe the CT and MRI features of pure acinar cell carcinoma of the pancreas in adults. MATERIALS AND METHODS: Eleven patients (six women and five men; mean age, 64 years) with acinar cell carcinoma, documented by pathologic examination of resected specimens, underwent CT (n=9) or MRI (n=2) examinations. Two radiologists evaluated imaging studies and determined, by consensus, the following data for each tumor: size, location, margination, internal density or signal intensity, and contrast enhancement pattern. In addition, they assessed the presence of calcification, pancreatic or bile duct dilation, and metastases. Imaging features were correlated with gross and microscopic pathologic features of the tumors. RESULTS: Masses were distributed throughout the pancreas (head, n=5; body, n=2; and tail, n=4). The mean largest dimensions were 6.0 x 5.3 cm (range, from 2 x 1.7 to 15 x 11 cm). Tumors were oval (n=5), round (n=4), or lobular (n=2). Ten (91%) masses were well marginated; nine (82%) were exophytic. Five (45%) masses enhanced homogeneously; the remaining tumors contained cystic areas. All masses enhanced less than the surrounding pancreas. Three (27%) masses contained calcifications. Four (80%) masses invaded the duodenum. Common bile and pancreatic duct dilatation was present in two and three patients, respectively. One patient had metastatic liver disease at presentation. CONCLUSION: Pure acinar cell carcinoma of the pancreas is usually an exophytic, oval or round, well-marginated, and hypovascular mass on CT and MRI. It typically is completely solid when small and contains cystic areas due to necrosis when large.     

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.     

Macrocystic serous adenoma of the pancreas: radiologic-pathologic correlation

OBJECTIVE: Macrocystic serous adenoma is a rare benign pancreatic neoplasm, recently described in the pathology literature. We describe the CT and MR imaging features in a series of five consecutive pathologically proven cases. MATERIALS AND METHODS: Of seven cases fulfilling the pathology criteria for macrocystic serous adenoma over an 11-year period, five patients underwent preoperative CT and MR imaging at our institution. In addition to the clinical presentation and pathologic features of the tumor, the following CT and MR imaging features were reviewed: size and location; wall thickness; internal septations; and presence of mural nodules, papillary projections, or calcifications. RESULTS: All patients but one were women (age range, 36-78 years; mean age, 48.6 years). The sizes of the tumors ranged from 1.5 to 5.0 cm (mean, 3.1 cm). Three (60%) of five tumors were located in the pancreatic head. The wall measured less than 2 mm in four lesions and 4 mm in one. No mural nodules, papillary projections, or calcifications were present. Lesions were unilocular (n = 3) or bilocular (n = 2). Excellent correlation of imaging features with gross pathology was observed. CONCLUSION: On CT and MR imaging, the macrocystic variant of serous adenoma typically appears as a small (< 5 cm), uni- or bilocular cyst with a thin (< 2 mm) wall that lacks mural nodules or calcifications. The imaging appearance of macrocystic serous adenoma is distinctly different from that of microcystic serous cystadenoma, but the imaging appearance of macrocystic serous adenoma is indistinguishable from mucinous cystadenoma and cystadenocarcinoma of the pancreas.     

Imaging of pancreatic neoplasms: comparison of MR and CT

Thirty-two patients with pathologically proved pancreatic carcinomas or cystadenomas were evaluated with MR images obtained with T1-weighted spin echo (short TR/short TE), inversion recovery, and T2-weighted spin-echo (long TR/long TE) pulse sequences. CT was used as the reference standard to determine the ability of MR to delineate normal and abnormal pancreatic anatomy and thereby to exclude or detect pancreatic malignancy. Short TR/short TE spin-echo sequences were significantly better (p less than .05) than inversion recovery or T2-weighted spin-echo sequences in resolution of both normal and abnormal anatomy. Resolution of pancreatic anatomy correlated (r = .9) with the image signal-to-noise ratio. In seven (22%) of 32 cases, MR visualized pancreatic tumors better than CT did because it showed a signal intensity difference between the tumor and normal pancreatic tissue. Overall, the slight superiority of MR over CT for tumor visualization tended to occur in larger tumors and was not statistically significant. On T1-weighted images, 63% (20 of 32) of pancreatic tumors studied had lower signal intensities than normal pancreatic tissue, whereas on T2-weighted sequences (TE = 60, 120, and 180 msec) only 41% (13 of 32) of tumors had increased signal intensities. Currently available MR imaging techniques offer no significant advantages over CT for evaluating the pancreas for neoplasia.     

Eosinophilic hepatic necrosis: magnetic resonance imaging and computed tomography comparison

OBJECTIVE: To compare the findings of magnetic resonance (MR) imaging with those of computed tomography (CT) of focal liver lesions related to peripheral eosinophilia. METHODS: For 12 patients with peripheral eosinophilia (>7%) examined with hepatic MR imaging and CT, 52 focal hepatic lesions larger than 0.5 cm, including 31 lesions simultaneously found on the 2 imaging modalities, were subjected to a comparative analysis of their imaging features. RESULTS: The total number of lesions distinguished from background liver was 39 (75%) on MR imaging and 44 (85%) on CT scans. On arterial phase images of 10 patients with comparable data, homogeneously hyperintense lesions were demonstrated more frequently (P = 0.006) on MR imaging (16 [50%] of 32 lesions) than on CT scans (4 [13%] of 32 lesions). Only 7 (22%) of the 32 hypoattenuating lesions on portal phase CT were depicted as hypointense lesions on portal phase MR images in 12 patients. On delayed phase images in 8 patients, the number of hyperintense lesions on MR images (9 [56%] of 16) was greater (P = 0.077) than that seen on the CT scans (4 [25%] of 16). CONCLUSIONS: For many focal hepatic lesions related to peripheral eosinophilia, dynamic MR imaging more easily demonstrates lesional enhancement on arterial and delayed phases than CT scans. Because of the higher degree of lesional enhancement of MR imaging compared with CT, the lesion-to-liver contrast may not be sufficient to distinguish the lesion from the background liver, resulting in decreased sensitivity of portal phase dynamic MR imaging.     

Hypervascular solid-appearing serous cystic neoplasms of the pancreas: Differential diagnosis with neuroendocrine tumours

Purpose

To describe imaging findings of arterial hypervascular solid-appearing serous cystic neoplasms (SCNs) of the pancreas on CT and MR and determine imaging features differentiating them from neuroendocrine tumours (NETs).

Materials and methods

We retrospectively identified 15 arterial hypervascular solid-appearing SCNs and randomly chose 30 size-matched pancreatic NETs. On CT, two radiologists in consensus assessed the size, morphology, and CT attenuation. On MR, predominant signal intensity and the amount of the cystic component on T2-weighted images and ADC maps were evaluated and compared using Fisher’s exact and Student’s t-test.

Results

The mean SCN size was 2.6 cm (range, 0.8–8.3). The CT findings were similar between the two tumours: location, shape, margin, and enhancement pattern. SCNs were significantly more hypodense on non-enhanced CT images than NETs (P?=?.03). They differed significantly on MR: bright signal intensity (P?=?.01) and more than a 10 % cystic component on T2-weighted images (P?=?.01) were more common in SCNs than in NETs. All SCNs showed a non-restrictive pattern on the ADC map, while NETs showed diffusion restriction (P?<?.01).

Conclusion

Arterial hypervascular solid-appearing SCNs and NETs share similar imaging features. Non-enhanced CT and MR images with T2-weighted images and ADC maps can facilitate the differentiation.

Key points

? Frequency of hypervascular solid-appearing SCNs was 7.3?% among surgically confirmed SCNs.? Hypervascular solid-appearing SCN of the pancreas can mimic pancreatic NETs.? Unenhanced CT and MR features help to differentiate the two tumours.

     

Hepatocellular carcinoma in patients with nonalcoholic fatty liver disease: helical CT and MR imaging findings with clinical-pathologic comparison

PURPOSE: To retrospectively evaluate the clinical, pathologic, and helical computed tomographic (CT) and magnetic resonance (MR) imaging findings of hepatocellular carcinoma (HCC) in patients with nonalcoholic fatty liver disease (NAFLD). MATERIALS AND METHODS: Institutional review board approval was obtained for this study; the need for patient informed consent was waived. Clinical, pathologic, and imaging findings were retrospectively evaluated in 22 men (mean age, 64.5 years) with HCC and NAFLD. Helical CT and MR images were reviewed for morphologic features such as tumor size, margins, necrosis, and degree of enhancement. RESULTS: Obesity, diabetes, and hypertension were common findings and were observed in 12 (55%), 14 (64%), and 13 (59%) of the 22 patients, respectively. The serum alpha-fetoprotein level was elevated in eight patients (36%). All patients had pathologic evidence of NAFLD. HCC was well-differentiated in seven patients, moderately differentiated in 11, and poorly differentiated in four. Large tumors (mean diameter, 8.4 cm) were depicted at CT and/or MR imaging in all patients. Twenty-one patients had a solitary or dominant mass. At imaging, tumor margins were well defined in 17 patients, with a smooth surface in 17, and there was evidence of a tumor capsule in 15. Necrosis was depicted in 16 patients. There was no evidence of calcifications, central scar, fat, or abdominal lymphadenopathy. CT was performed in 20 patients. HCC was hypoattenuating on unenhanced CT scans in 14 patients, heterogeneously hyperattenuating in the arterial phase in 20, and hypoattenuating in the portal phase in 14. MR imaging was performed in 16 patients. HCC was hyperintense compared with liver parenchyma at T2-weighted MR imaging in all 16 patients, hypointense at T1-weighted imaging in 14, heterogeneously hyperintense at arterial phase T1-weighted imaging in 16, and hypointense at portal phase T1-weighted imaging in 14. CONCLUSION: HCC in patients with NAFLD is more likely to manifest as a large solitary or dominant mass characterized by smooth and possibly encapsulated margins, necrosis, and hypervascularity.     

Primary malignant mixed mullerian tumor of the uterus: findings on sonography, CT, and gadolinium-enhanced MRI

OBJECTIVE: The purpose of our study was to evaluate the sonographic, contrast-enhanced CT, and gadolinium-enhanced MRI findings of primary malignant mixed müllerian tumors (MMMTs) of the uterus. CONCLUSION: Uterine MMMT most commonly presents as an intracavitary mass with coexistent dilatation of the endometrial canal. Tumors tend to appear hyperechoic on sonography, heterogeneously hypodense and ill defined on contrast-enhanced CT, and heterogeneously hyperintense on T2-weighted MR images with signal abnormalities indicating subacute hemorrhage on T1-weighted MR images. Myometrial invasion is common and has a predilection for the uterine fundus.     

胰腺浆液性微囊性囊腺瘤CT和MRI表现

目的 分析胰腺浆液性微囊性囊腺瘤(SMCA)的CT和MRI影像表现特征.方法 回顾性分析经手术病理证实的17例胰腺SMCA的CT及MRI表现,包括肿瘤位置、长径、分隔、增强表现及有无钙化、中央瘢痕、胰胆管扩张等影像表现.结果 17例SMCA:1例同时行CT和MR检查,10例行CT检查,6例MR扫描(其中2例同时行MRCP).病变位于胰头2例,胰颈2例,胰腺体尾部13例.肿瘤长径1.7~14 cm,平均5.2 cm.16例可见分隔,1例分隔显示欠佳,9例可见中央瘢痕.增强扫描分隔及瘢痕强化,囊性成分均无强化.6例可见远端主胰管扩张.结论 胰腺SMCA有一定的影像学特征,多表现为分叶状结节或肿物,具有多发小囊,囊腔多<2 cm,囊与囊之间见多发纤维分隔,增强扫描后纤维分隔明显强化,但低于胰腺组织.中央瘢痕是其特征性表现,在MR上多表现为T1WI及T2WI等或稍低信号.典型的胰腺SMCA根据CT和MRI表现可以做出明确诊断.     

Intracranial germinomas: correlation of imaging findings with tumor response to radiation therapy

OBJECTIVE: The purpose of this study was to correlate imaging characteristics of intracranial germinomas with response to radiation therapy. MATERIALS AND METHODS: Using tumor size at the completion of irradiation, we classified 23 patients with histologically proven germinomas in the pineal gland (n = 6), the suprasellar region (n = 7), and the basal ganglia (n = 10) into two groups: excellent response group (n = 14) and good response group (n = 9). Excellent response was defined as complete resolution or residual tumor less than 1.0 cm in diameter, and good response was defined as residual tumor of 1.0-3.0 cm in diameter. CT (n = 53) and MR (n = 32) images obtained before, during, and after radiation therapy were retrospectively analyzed with particular attention to the location, size, presence of cystic change, and CSF seeding of the tumors. RESULTS: In all 23 patients, the tumors decreased 85-100% in size at the completion of irradiation with 40-56 Gy. A significant factor in the different responses to irradiation between patients in the excellent and good response groups was cystic change of the tumor. Tumors with cystic components responded more slowly and had larger residual lesions than did tumors without cystic components (p < .01). In eight of 12 cystic tumors, the cystic portion of the tumor responded more slowly than did the solid portion and remained visible on imaging 6-12 months after irradiation. We found no significant differences between the two groups in location, size, and CSF seeding of tumors. In 12 patients with residual lesions at the completion of irradiation, the tumors proceeded to resolve after completion of treatment. CONCLUSION: In our study, tumor response to radiation therapy correlated negatively with the presence of a cystic region.     

Imaging-guided radiofrequency ablation of solid renal tumors

OBJECTIVE: We performed a retrospective review of imaging-guided radiofrequency ablation of solid renal tumors. MATERIALS AND METHODS: Since May 2000, 35 tumors in 20 patients have been treated with radiofrequency ablation. The size range of treated tumors was 0.9-3.6 cm (mean, 1.7 cm). Reasons for patient referrals were a prior partial or total nephrectomy (nine patients), a comorbidity excluding nephrectomy or partial nephrectomy (10 patients), or a treatment alterative to nephron-sparing surgery (one patient who refused surgery). Tumors were classified as exophytic, intraparenchymal, or central. Sixteen patients had 31 lesions that showed serial growth on CT or MR imaging. Of these 16 patients, four patients with 10 lesions had a history of renal cell carcinoma, and two patients with 11 lesions had a history of von Hippel-Lindau disease. Four patients had incidental solid masses, two of which were biopsied and shown to represent renal cell carcinoma, and the remaining two masses were presumed malignant on the basis of imaging features. Successful ablation was regarded as any lesion showing less than 10 H of contrast enhancement on CT or no qualitative evidence of enhancement after IV gadolinium contrast-enhanced MR imaging. RESULTS: Of the 35 tumors, 22 were exophytic and 13 were intraparenchymal. Twenty-seven of the 35 were treated percutaneously using either sonography (n = 22) or CT (n = 5). Two patients had eight tumors treated intraoperatively using sonography. Patients were followed up with contrast-enhanced CT (n = 18), MR imaging (n = 5), or both (n = 5) with a follow-up range of 1-23 months (mean, 9 months). No residual or recurrent tumor and no major side effects were seen. CONCLUSION: Preliminary results with radiofrequency ablation of exophytic and intraparenchymal renal tumors are promising. Radiofrequency ablation is not associated with significant side effects. Further follow-up is necessary to determine the long-term efficacy of radiofrequency ablation.     

Primary malignant fibrous histiocytoma of the chest wall: CT and MR appearance

PURPOSE: The purpose of this work is to describe the CT and MR appearance of primary malignant fibrous histiocytoma (MFH) of the chest wall. METHOD: Eleven men and eight women (45-76 years old) with primary MFH of the chest wall who underwent both CT and MRI were enrolled, and the imaging interpretation was retrospectively compared to the pathologic specimen. RESULTS: All tumors were inhomogeneous in appearance on CT scans. All tumors showed high signal intensity on T2-weighted images. On T1-weighted MR images, tumors displayed inhomogeneous isosignal intensity in 15 cases (79%) and low signal intensity in 5 (21%) compared with the surrounding muscle. Tumors exhibited inhomogeneous enhancement in all except three localized tumors on enhanced CT and MRI. Invasion of intercostal muscle was noted on MR images in 18 patients (95%) and on CT in 11 patients (58%). CONCLUSION: There might be various radiologic appearances of MFH. However, CT and MRI are able to demonstrate the exact localization and disease extent of MFH arising in the chest wall.     

CT and MR imaging characteristics of infantile hepatic hemangioendothelioma

Aim

This study aims to analyze computed tomography (CT) and magnetic resonance (MR) imaging features of infantile hepatic hemangioendotheliomas before and after treatment.

Materials and methods

CT and MR examinations of seven infants with biopsy proven hepatic hemangioendotheliomas were retrospectively analyzed. The distribution, number, size, imaging appearance, enhancement pattern and post-treatment changes of the tumors were evaluated.

Results

A total of 153 hepatic hemangioendotheliomas were detected on CT (111) and MR (42) imaging. In six infants, 109/111 (98.2%) tumors were hypodense and 2/111 (1.8%) lesions contained calcification on unenhanced CT. On MR imaging, all 42 lesions in one infant were heterogeneously T1-hypointense and T2-hyperintense compared to the normal liver parenchyma. Contrast-enhanced CT and MRI showed peripheral rim (51.6%), uniform (48.4%), fibrillary (33.3%), and nodular (28.8%) contrast enhancement in the hepatic arterial phase. Homogeneous (100%), rim (98.2%) and mixed enhancement patterns were noted in tumors <1.0 cm, >2.0 cm and 1.0-2.0 cm in diameter respectively in the hepatic arterial phase. In three patients who underwent steroid therapy, follow-up CT examination demonstrated tumor size reduction and increased intra-tumoral calcification in two patients.

Conclusion

Infantile hepatic hemangioendotheliomas show some typical imaging features and size-dependent pattern of contrast enhancement on CT and MR imaging, which allow accurate imaging diagnosis and post-treatment evaluation.     

CT and MRI findings in KIT-weak or KIT-negative atypical gastrointestinal stromal tumors

The large majority of gastrointestinal stromal tumors (GIST) can be diagnosed on the basis of KIT immunoreactivity. However, some atypical tumors show weak or negative KIT expression. We studied the imaging characteristics of atypical GIST, reviewing CT and MRI findings in ten patients (eight men, two women; mean age 59 years) with atypical GIST. Radiological studies were evaluated by two radiologists by consensus and included CT and MR imaging in all patients. Pathological diagnoses were made from surgery and confirmed by the polymerase-chain reaction (PCR) to amplify both exons of the c-kit gene and PDGFRA gene. The CT and MR examinations revealed a heterogeneous mass of the stomach containing cystic regions and soft tissue elements in all cases. All lesions were extraluminal masses and had an exophytic epicenter. On T1-weighted MR images soft tissue elements of the tumors were of homogeneously low- (n=3) or iso-signal intensity (n=7) compared with the liver parenchyma. On fast spin-echo T2-weighted MR images soft tissue elements of all tumors showed cystic regions of significantly high signal intensity interspersed with septumlike structures of low signal intensity. All lesions exhibited homogeneously (n=4) or heterogeneously (n=6) mild to moderate enhancement of soft tissue elements. Despite the relatively small number of patients CT and MRI findings of atypical GIST are a submucosal mass with soft tissue elements and cystic regions.     

Gastrinomas: comparison of MR imaging with CT, angiography, and US

In this prospective study, magnetic resonance (MR) imaging was used to localize gastrinoma in 24 patients with Zollinger-Ellison syndrome. The results were confirmed by means of either surgery or percutaneous liver biopsy and compared with results of computed tomographic (CT) scanning, selective abdominal angiography, and abdominal ultrasound (US). For primary extrahepatic gastrinoma (intra-or extrapancreatic), MR imaging had a sensitivity of 20% and a specificity of 100%, with a positive predictive value of 100% and a negative predictive value of 11%. For metastatic gastrinoma in the liver, MR imaging had a sensitivity of 43% and a specificity of 100%, with a positive predictive value of 100% and a negative predictive value of 81%. The ability of MR imaging to depict extrahepatic gastrinomas was directly related to tumor size; no tumors smaller than 1 cm were detected, and 50% of tumors 3 cm or larger were detected. MR imaging was as effective as abdominal US but less effective than either CT scanning or selective abdominal angiography for the detection of extrahepatic gastrinoma. In seven patients with hepatic gastrinoma, three gastrinomas were detected with MR imaging and with abdominal US, while five were detected with CT scanning and with selective abdominal angiography. These results indicate that, at the present time, MR imaging is generally not useful in the initial attempt to localize gastrinomas.     

In-111-leukocyte scintigraphy for detection of infection associated with peritoneal dialysis catheters

In 41 patients with clinical evidence of pancreatic islet cell tumors, CT detected 21 of 27 tumors that were proved at surgery (sensitivity 78%) and correctly excluded the diagnosis in 14 of 14 patients with no evidence of tumor at long-term follow-up. Using rapid sequence CT scanning and bolus contrast material infusion, a vascular blush was identified in 13 of 16 tumors (81%). Tumors as small as 0.9 cm were localized. CT identified all malignant tumors, and staging accuracy was 100%. CT is useful as the initial imaging procedure for the diagnosis and staging of suspected islet cell tumors. Pancreatic venous sampling and angiography are complementary to CT for the detection of smaller lesions.     

Dynamic contrast-enhanced MR imaging and dual-phase helical CT in the preoperative assessment of suspected pancreatic cancer: a comparative study with receiver operating characteristic analysis.

OBJECTIVE: The purpose of this study was to compare dynamic contrast-enhanced MR imaging and dual-phase helical CT in the preoperative assessment of patients with suspected pancreatic carcinoma. SUBJECTS AND METHODS: Thirty-three consecutive surgical candidates (20 men, 13 women; 39-81 years old) were included. MR imaging comprised fast spin-echo (TR/TE 4000/91), fat-suppressed T1-weighted spin-echo (500/15), and T1-weighted breath-hold gradient-echo fast low-angle shot (100/4; flip angle, 80 degrees) images before and after the administration of gadopentetate dimeglumine. Helical CT used 5-mm collimation with a pitch of 1:1.5-1.7; images were obtained 20 and 65-70 sec after injection of 150 ml of contrast material. Two pairs of interpreters who were unaware of the results of the other imaging method independently scored each examination for the presence of a lesion and for surgical resectability using a five-point scale. Results were correlated with surgery (n = 25) or consensus review (n = 8). Receiver operating characteristic methodology was used to analyze the results for resectability, and positive predictive values were calculated. RESULTS: Both MR imaging and helical CT revealed 29 of 31 lesions. In determining lesion resectability, the mean areas under the receiver operating characteristic curves were 0.96 and 0.81 (p = .01) and the positive predictive values were 86.5% and 76% (p = .02) for MR imaging and helical CT, respectively. CONCLUSION: MR imaging and helical CT performed equally well in lesion detection. MR imaging was significantly better in the assessment of resectability of pancreatic tumors.