N. Cem Balci

Pancreatic diffusion-weighted imaging (DWI): Comparison between mass-forming focal pancreatitis (FP), pancreatic cancer (PC), and normal pancreas

To compare diffusion‐weighted imaging (DWI) findings and the apparent diffusion coefficient (ADC) values of pancreatic cancer (PC), mass‐forming focal pancreatitis (FP), and the normal pancreas.

Neuroendocrine tumors of the pancreas: spectrum of appearances on MRI.

We reviewed our 8.5 year experience with magnetic resonance imaging (MRI) in the demonstration of neuroendocrine tumors of the pancreas using precontrast fat‐suppressed T1‐weighted, fat‐suppressed T2‐weighted, and serial post‐gadolinium T1‐weighted images, to describe the spectrum of appearances of these tumors. All MR examinations of patients with histogically proven neuroendocrine tumors were retrospectively reviewed. Histological type, tumor location, tumor diameter, signal intensity on precontrast images, enhancement patterns, and presence and appearance of metastases were determined. Twenty‐two patients had histologically proved neuroendocrine tumors detected by MRI over the 8.5 year period. Histological types were gastrinoma (n = 8), insulinoma (n = 3), glucagonoma (n = 2), somatostatinoma (n = 1), VIPoma (n = 1), ACTHoma (n = 1), carcinoid (n = 1), and five untyped tumors. Primary tumors ranged in diameter from 1 to 6.2 cm. There was one histopathology‐proven false‐positive neuroendocrine tumor. The positive predictive value for MRI in the detection of these tumors was 96%. The most common appearance on precontrast images was low signal intensity on T1‐weighted images and high signal intensity on T2‐weighted images, which was observed in tumors in 18 of 22 patients. Moderate or intense early enhancement of all or portions of the primary tumors was observed in tumors in 19 of 22 patients either as uniform homogeneous, ring, or diffuse heterogeneous enhancement. Enhancement was minimal on these images in the other three patients. Gastrinomas enhanced in a ring pattern in 7 of 8 patients whereas the majority (9 of 11 patients) of noninsulinoma‐nongastrinoma and untyped tumors enhanced in a diffuse heterogeneous fashion. Liver metastases were present in 13/22 patients including 3/8 with gastrinoma and 9/11 with noninsulinoma‐nongastrinoma tumors. Most neuroendocrine tumors of the pancreas are low signal intensity on fat‐suppressed T1‐weighted images and moderately high in signal intensity on fat‐suppressed T2‐weighted images, although variations do exist. Tumors most often enhance in an early moderately intense fashion. Gastrinomas are often different in appearance than other neuroendocrine tumors in that they usually enhance in a ring fashion whereas nongastrinoma‐noninsulinoma tumors usually enhance in a heterogeneous fashion. J. Magn. Reson. Imaging 2000;11:141–148.

Budd‐chiari syndrome: Spectrum of appearances of acute, subacute, and chronic disease with magnetic resonance imaging

The purpose of this study was to describe our collective experience in the magnetic resonance (MR) investigation of patients with proven acute, subacute, and chronic Budd‐Chiari syndrome and to demonstrate the spectrum of appearances on T1‐ and T2‐weighted as well as dynamic post‐gadolinium spoiled gradient‐echo imaging. All patients with proven Budd‐Chiari syndrome who underwent MR examinations between June, 1992 and October, 1998 were included in the study. Fourteen patients were included in the study: four with acute, three with subacute, three with chronic, and four with acute superimposed on either subacute (two) or chronic (two) Budd‐Chiari syndrome. MR imaging features were retrospectively evaluated to determine: a) liver morphology, b) pattern of signal intensity (SI) on T1‐weighted images, c) pattern of SI on T2 weighted images, d) dynamic enhancement characteristics, e) presence or absence of visible venous thrombosis, and f) presence or absence of venous macroscopic collaterals. The MR findings were correlated with surgical, histopathological, and laboratory data to determine imaging characteristics related to the chronicity of the disease process. Hepatic venous thrombosis or absence of hepatic venous flow was demonstrated in all patients in the study. In the four patients with acute Budd‐Chiari syndrome, the liver periphery was moderately low signal on T1 and moderately high signal on T2‐weighted images relative to the central liver; both early and late gadolinium—enhanced images revealed diminished peripheral enhancement. In the three patients with subacute Budd‐Chiari syndrome, the liver periphery was moderately low signal on T1, and moderately high signal on T2‐weighted images, while early and late gadolinium‐enhanced images revealed heterogenously increased enhancement within the liver periphery. In the three patients with chronic Budd‐Chiari syndrome, the SI differences between peripheral and central liver were minimal on T1‐ and T2‐weighted images, and enhancement differences were also minimal. Extensive bridging intrahepatic and capsular venous collaterals were visualized in chronic cases. In the four patients with acute Budd‐Chiari syndrome superimposed on more chronic disease, a combination of gadolinium enhancement patterns was observed on MR images. Enhancement patterns between central and peripheral liver were different for acute, subacute, and chronic Budd‐Chiari syndromes, suggesting differentiation between these phases of the disease process. Application of this pattern approach permitted recognition of acute changes superimposed on more chronic disease. J. Magn. Reson. Imaging 2000;11:44–50.

Radiologic features of cystic, endocrine and other pancreatic neoplasms

This article presents imaging features of cystic, endocrine and other pancreatic neoplasms. Microcystic adenoma which is composed of small cysts (<2 cm), its macrocystic subgroup contains solitary cyst. Multiple cysts larger than 2 cm are associated with mucinous cystic neoplasm. Swiss cheese appearence with central calcification is characteristic for microcystic adenomas. Septal and mural enhancement as well as larger size (>2 cm) are accounted for mucinous cystic neoplasms, its variant along pancreatic duct is ductectatic mucinous cystic neolasm. Endocrine tumors of pancreas are hypervascular and can be depicted on early dynamic enhanced crosssectional imaging modalities or on angiography when they are <1 cm. Pancreatic metastases and lymphomas are rare neoplasms which should also be included in differential diagnosis for pancreatic masses.

Radiologic diagnosis and staging of pancreatic ductal adenocarcinoma

This article presents imaging modalities in the diagnosis and staging of pancreatic ductal adenocarcinoma. Magnetic resonance imaging (MRI) and endoscopic ultrasonography (EUS) have the highest accuracy in detection of pancreatic cancer. MRI and EUS have similar accuracy in determining the local extent of pancreatic cancer. Angiography, computed tomography (CT) angiography and EUS are similarly accurate in evaluating peripancreatic vascular involvement. MRI is the superior method for detecting liver metastases and peritoneal implants of pancreatic ductal adenocarcinoma. Endoscopic retrograde cholangiopancreatography (ERCP) and magnetic resonance cholangiopancreatography (MRCP) are used to assess the biliary tract of patients with pancreatic cancer. Positron emission tomography (PET) is useful in distinguishing pancreatic cancer from focal pancreatic inflammation.

Suspected chronic pancreatitis with normal MRCP: Findings on MRI in correlation with secretin MRCP

To review pancreatic MRI findings and their relationship with estimated pancreatic exocrine function on secretin‐stimulated MR cholangiopancreatography (S‐MRCP) in patients with clinically suspected chronic pancreatitis and normal baseline MRCP findings.

Pyogenic hepatic abscesses: MRI findings on T1- and T2-weighted and serial gadolinium-enhanced gradient-echo images.

The purpose of this study was to determine the magnetic resonance imaging (MRI) features of pyogenic hepatic abscesses on T1‐weighted, T2‐weighted, and serial gadolinium (Gd)‐enhanced T1‐weighted spoiled gradient‐echo (SGE) images including images acquired in the immediate, intermediate, and late phases of enhancement. The MRI studies of 20 patients with pyogenic liver abscesses were retrospectively reviewed. All patients were examined on 1.5 (n = 19) and 1.0 (n = 1) T MR scanners. MR studies included T1‐weighted, T2‐weighted, and serial Gd‐enhanced SGE images. The following determinations were made: signal intensity of the abscess cavity and perilesional liver tissue, and the presence of internal septations, layering material, or air in the abscess cavity. The pattern of enhancement of the abscess wall, internal septae and peri‐abscess liver were evaluated on serial Gd‐enhanced SGE images. A total of 53 abscesses were observed in the 20 patients. Forty‐eight abscesses were hypointense on T1‐weighted and hyperintense on T2‐weighted images. Internal septations were present in four abscesses. Lower signal intensity material was observed in a dependent location on T2‐weighted images in one abscess. Signal void foci of air located on the nondependent surface was observed in two abscesses. Two other abscesses contained signal void air that occupied the entire abscess cavity, observed on all imaging sequences. On serial gadolinium‐enhanced images, all abscesses revealed early enhancement of the wall, which persisted with negligible change in degree of enhancement or thickness on delayed images. Abscess walls ranged in thickness from 2 to 5 mm. Internal septations ranged in thickness from 2 to 3 mm. Abscess walls and septations were relatively uniform in thickness with no evidence of focal nodularity. Periabscess liver tissue was mildly hypointense on T1‐weighted and mildly hyperintense on T2‐weighted images in 20 lesions, which were either circumferential (n = 12) or wedge‐shaped (n = 8). All these regions enhanced more than the remainder of the liver on immediate post‐gadolinium images and remained relatively hyperintense on late phase images. Periabscess liver parenchyma was isointense on both T1‐ and T2‐weighted images in 18 lesions, and in these lesions wedge‐shaped subsegmental (n = 6) or segmental (n = 12) enhancement was observed on immediate gadolinium‐enhanced images, which faded to isointensity on intermediate phase images. No perilesional signal changes and enhancement difference was observed in 15 lesions. Characteristic features of abscesses include: intense mural enhancement on early gadolinium‐enhanced images, which persists with negligible change in thickness and intensity on later post‐gadolinium images, and the presence of periabscess increased enhancement on immediate post‐gadolinium images. These MRI features may help to distinguish abscesses from other focal liver lesions during differential diagnosis.J. Magn. Reson. Imaging 1999;9:285–290.

Breath‐hold 3D gradient‐echo MR imaging of the lung parenchyma: Evaluation of reproducibility of image quality in normals and preliminary observations in patients with disease

This study evaluates the reproducibility and image quality of a three‐dimensional (3D) gradient‐echo sequence for imaging the lung parenchyma, with and without gadolinium administration, using a 2D spoiled gradient‐echo sequence for comparison. Twenty patients without lung disease (normals) and five patients with lung disease (lung disease) underwent paired 2D and 3D gradient‐echo sequences, without contrast (24 patients) and with contrast (18 patients). Images were retrospectively reviewed independently in a blinded fashion by two investigators. Artifacts and demonstration of central lung, peripheral lung, heart, pulmonary arteries, and esophagus were evaluated. Image quality of the central lung was rated as fair or good in 5 and 4 (reader one and two) patients with non‐contrast 2D gradient‐echo, 24 and 25 patients with non‐contrast 3D gradient‐echo, 3 and 1 patient(s) with contrast‐enhanced 2D gradient‐echo, and 19 and 19 patients with contrast‐enhanced 3D gradient‐echo imaging. Differences in image quality between 2D and 3D sequences were significant (P < 0.001). Heart‐related phase artifacts were negligible in 2 and 0 patients with non‐contrast 2D gradient‐echo, 23 and 25 patients with non‐contrast 3D gradient‐echo, 0 and 0 patients with contrast‐enhanced 2D gradient‐echo, and 17 and 19 patients with contrast‐enhanced 3D gradient‐echo imaging. Differences in heart‐related phase artifact in the central lung between 2D and 3D sequences were significant (P = 0.001). Infiltrates, lung cancer, and pulmonary metastasis were better shown on the gadolinium‐enhanced 3D gradient‐echo sequences than on the other sequences. Breath‐hold 3D gradient‐echo imaging results in good image quality and negligible image artifacts and is superior to 2D spoiled gradient‐echo imaging. Preliminary results in patients with disease appear promising. J. Magn. Reson. Imaging 2000;11:195–200.

Hepatobiliary and Pancreatic MRI and MRCP Findings in Patients with HIV Infection

OBJECTIVE The purpose of this article is to describe the spectrum of MRI and MR cholangiopancreatography (MRCP) findings of hepatic, pancreatic, and biliary manifestations in patients with HIV infection. CONCLUSION The spectrum of MRI and MRCP findings in HIV-infected patients includes acute or chronic hepatitis (or both), pancreatitis, cholangitis, acalculous cholecystitis, and biliary strictures that may resemble primary sclerosing cholangitis. The presence of segmental extrahepatic biliary strictures is characteristic of AIDS cholangiopathy.

Magnetic resonance imaging of the liver: How I do it

The present paper provides a brief overview of the rationale behind magnetic resonance imaging (MRI) techniques, a description of the most common sequences used, and a general approach to performing liver MRI.