Adrenal gland enhancement at MR imaging with Mn-DPDP.

PURPOSE: To determine adrenal gland enhancement with manganese (II) N,N' dipyridoxylethylenediamine-N,N'-diacetate 5,5'bis(phosphate) (DPDP) at magnetic resonance imaging. MATERIALS AND METHODS: After phase III trials, fat-suppressed, motion-compensated, T1-weighted spin-echo images (repetition time, 500 msec; echo time, 12 msec) of 13 consecutive patients were obtained at 1.5 T at one site, prior to and approximately 30 minutes after intravenous administration of 5 mumol/kg Mn-DPDP. Images were analyzed visually and by means of region-of-interest measurements, normalized to spleen. With data added from three more sites, enhancement of three adrenal adenomas and two metastases was analyzed. RESULTS: Twenty-five of 26 adrenal glands were depicted on MR images, and all showed enhancement. Mean adrenal enhancement (38%) was comparable to mean enhancement of liver (46%), pancreas (25%), and renal cortex (58%). Adrenal cortex and medulla could not be distinguished in nonenhanced or enhanced images. All three adrenal adenomas enhanced by more than 40%, but the metastases did not enhance. CONCLUSION: Functioning adrenal tissue (glands and at least some adenomas) are enhanced with Mn-DPDP.

Hybrid RARE: implementations for abdominal MR imaging.

Hybrid RARE (rapid acquisition with relaxation enhancement) is a family of magnetic resonance (MR) imaging techniques whereby a set of images is phase encoded with more than one spin echo per excitation pulse. This increases the efficiency of obtaining T2-weighted images, allowing greater flexibility regarding acquisition time, resolution, signal-to-noise ratio, and tissue contrast. Hybrid RARE techniques involve several important new user-selectable parameters such as effective TE, echo train length, and echo spacing. Choices of other parameters, such as TR, sampling bandwidth, and acquisition matrix, may be different from those of comparable conventional T2-weighted spin-echo images. Different hybrid RARE implementations can be used for abdominal screening, with T2-weighted or T2-weighted and inversion-recovery contrast, or for characterizing liver lesions or imaging the biliary system with an extremely long TE. High-resolution images may be obtained by averaging multiple signals during quiet breathing, or images may be acquired more rapidly during suspended respiration. In this review, the authors discuss the basic principles of hybrid RARE techniques and how various imaging parameters can be manipulated to increase the quality and flexibility of abdominal T2-weighted MR imaging.

Abdominal iron distribution in sickle cell disease: MR findings in transfusion and nontransfusion dependent patients.

OBJECTIVE: Our goal was to determine the difference in iron distribution between transfusion dependent (TD) and nontransfusion dependent (NT) patients with sickle cell disease (SCD). MATERIALS AND METHODS: The T2-weighted and T2*-weighted abdominal MR images in nine cases of homozygous SCD were reviewed to determine the distribution of low signal from iron in five TD and four NT patients. RESULTS: All eight patients with visualized spleens had decreased splenic signal intensity. One patient who had no history of splenectomy had no visualized splenic tissue. The majority of both groups had renal cortex of low signal intensity that was attributable to iron deposition from intravascular hemolysis and was not correlated with clinical renal abnormalities. None of the NT group had liver or pancreas of low signal intensity, while all five TD patients had decreased liver signal intensity and three of five had decreased pancreatic signal intensity. CONCLUSION: Decreased pancreatic signal intensity can occur in TD patients, perhaps suggesting total body iron overload. Nontransfusion dependent sickle cell patients usually have normal hepatic signal intensity and do not have total body iron overload, even in the presence of renal and splenic iron deposition.

Idiopathic hemochromatosis: MR imaging findings in cirrhotic and precirrhotic patients.

The authors reviewed T2-weighted and T2*-weighted abdominal magnetic resonance (MR) images in 19 pathology-proved cases of hepatic iron overload to compare patterns of iron distribution among cirrhotic and precirrhotic patients with idiopathic hemochromatosis (IH), as well as nontransfusional hepatic siderosis of other causes. Fifteen patients had clinical and laboratory evidence of IH. Four patients without IH had cirrhosis with moderate siderosis. In the MR images of all 19 patients, the liver had low signal intensity. The pancreas of 10 of 11 cirrhotic patients with IH had low signal intensity. All four precirrhotic patients with IH and all four cirrhotic patients without IH had pancreas with normal signal intensity at MR. Thus, pancreatic signal intensity was decreased only in cirrhotic patients with IH in this limited series. Conversely, pancreatic signal intensity is often normal in precirrhotic patients with IH prior to the development of cirrhosis, a stage at which definitive diagnosis by means of quantitative liver biopsy is important because early phlebotomy may prevent morbidity and mortality from IH. In cirrhotic patients with MR evidence of increased hepatic iron, the cause of cirrhosis is less likely to be IH if pancreatic signal intensity is normal.