ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

A variety of diffuse and focal disease processes affect the liver. MRI is likely the imaging modality of choice tor investigation of patients suspected of having diffuse disease such as cirrhosis, hemochromatosis, or fatty infiltration. MRI is extremely effective at detecting and characterizing focal hepatic lesions. In particular, patients suspected of possessing hemangiomas, hepatocellular carcinoma, or hypervascular liver metastases are better evaluated by MRI than other imaging modalities. Immediate post gadolinium spoiled gradient echo and T2-weighted fat suppressed spin echo are very effective at lesion detection, whereas serial post gadolinium spoiled gradient echo is essential for lesion characterization. New fast T2-weighted sequences and tissue specific contrast agents may further increase the role of liver MRI by shortening exam time and increasing sensitivity and specificity, respectively.

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

MRI of the spleen and pancreas requires specialized sequences which diminish artifacts in the upper abdomen High temporal resolution sequences (e.g., spoiled gradient echo) acquired immediately after intravenous Gd-DTPA administration are necessary for imaging both the spleen and pancreas. In evaluating the spleen, early post Gd-DTPA images are essential as many focal disease-processes (e.g., lymphomatous deposits or metastases) equilibrate rapidly (<2 min) with splenic parenchyma. Complete pancreatic examination also requires the use of T1-weighted fat suppressed spin echo T2-weighted images provide complementary information in a number of settings, in particular in the evaluation of islet cell tumors. Pancreatic ductal carcinoma is low signal on T1-weighted images and enhances in a diminished fashion on immediate post Gd-DTPA images. These tumors are well differentiated from local chronic pancreatitis and islet celltumors based on their appearances on combined T1. T2-weighted and immediate post Gd-DTPA enhanced images.

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

MR is able to detect and characterize the majority of disease entities which affect the adrenal glands and kidneys. In the evaluation of the adrenal glands in-phase and out-of-phase T1-weighted imaging may be the most effective noninvasive method to distinguish benign adenomas from malignant masses. T2-weighted images are sensitive and relatively specific for the investigation of pheochromocytoma. Although MRI is excellent at evaluating the kidneys, the lower cost and good image quality of CT render it the primary diagnostic tool for renal imaging. The major current applications for MRI ol the kidneys include evaluation of patients with allergy to iodnated contrast, renal failure, and the characterization of com plicated renal lesions. Evaluation of venous thrombus in the context of renal cancer is likely also a useful role for MRI.

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

The diagnosis of retroperitoneal pathology has historically presented a challenge to physicians. The signs and symptoms of retropcritoneal diseases are myriad and often subtle. Cross-sectional imaging techniques have therefore had a major impact on retroperitoneal diagnosis. Computed tomography (CT) is currently the standard imaging technique for evaluating the retropcritoneum. Magnetic resonance (MR) imaging is also well suited for retropentoneal imaging and has several advantages over CT. MR imaging is the preferred technique in patients with contraindications to iodinated contrast material due to renal dysfunction or allergy. It excels at evaluating the blood vessels, providing a reliable assessment of vessel patency, aneurysm, or dissection. The ability of MR imaging to acquire images without exposure to ionizing radiation facilitates imaging of obstetric and pediatric patients. The ability to acquire images in any plane is a distinct advantage for assessing the extent and origin of retroperitoneal pathology, although this can now be accomplished with spiral CT as well as MR imaging. The spatial resolution of CT is currently superior to MR imaging for most retroperitoneal studies, but this may change with continued technological advances such as improved phased array coil systems (Bidgood WD Jr. Schiebler ML. Retroperitoneum and mesentery. In: Ros PR, Bidgood WD Jr. eds.Ahdominal magnetic resonance imaging. St. Louis: Mosby Year Book. 1993:310–47). Finally, MR imaging provides the flexibility to tailor each examination to the specific clinical question. With few exceptions, anything CT can do in the retroperitoneum, MR imaging can do as well or better.

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

Echo planar imaging (EPI) is an ultrafast magnetic resonance (MR) imaging method first proposed more than 15 years ago. With EPI, all the information necessary to create an image is obtained very rapidlv (typically on the order of 50–150 ms). Special hardware modifications are needed, particularly in the magnetic field gradients and data acquisition systems, to permit such high-speed imaging. In the abdomen, EPI images are insensitive to degradation from breathing or peristaltic motion. The essentially infinite repetition time and lack of motion-induced blurring can improve lesion characterization compared with standard imaging methods. Segmented EPI permits high-resolution T2-weighted images to be acquired within a single breath-hold. Diffusion imaging, which was previously restricted to the brain, can now be done in the abdomen because of the relative insensitivity of EPI images to bulk motion. Diffusion imaging of the kidney has been found to correlate with its functional status. By using EPI readouts, MR angiography can be done more quickly. Further work is needed to improve the spatial resolution and overcome magnetic susceptibility artifacts, particularly with single-shot EPI. Nonetheless, EPI offers considerable potential for improved anatomical and functional imaging of the abdomen.

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0899-3459    

出版商:OVID    

年代:1995

数据来源: OVID