The purpose of this study was to determine the advantage of a three-dimensional (3D) single-shot fast-spin-echo (SSFSE) sequence to obtain MR cholangiopancreatography (MRCP) with a .5-T MR unit by comparison with a two-dimensional (2D) SSFSE sequence. MRCP with 2D-SSFSE and with 3D-SSFSE with 128 echo train lengths was performed on 15 volunteers and 38 patients with pancreatobiliary disease using a .5-T MR unit. For maximum intensity projection (MIP) reconstruction, the section thickness of source images was 4 mm in the 2D-SSFSE and 3 mm in the 3D-SSFSE. 3D volume data in 3D-SSFSE were obtained using repeated short breath-hold of 2 seconds for every repetition time throughout the examination. The image quality, duct conspicuity, signal-intensity ratio (SIR), and contrast-to-noise ratio (CNR) were evaluated. In 23 of the patients who underwent both MRCP and direct cholangiopancreatography (endoscopic retrograde cholangiopancreatography [ERCP]/percutaneous transhepatic cholangiography [PTC]), a comparison between these two modalities was also conducted. The image quality of the MIP image with 3D-SSFSE (49 of 53, 92.5% graded excellent or good) was superior to that with 2D-SSFSE (31 of 53, 58.4%). Duct conspicuity, SIR, and CNR were significantly higher with 3D-SSFSE than with 2D-SSFSE. 3D-SSFSE also showed a stronger relationship with the ERCP/PTC findings compared to 2D-SSFSE. 3D-SSFSE provided satisfactory quality, SIR, and CNR of MRCP images, even when a .5-T MR unit was used, because the breath-hold technique used during 3D data sampling minimized all types of motion effects.

Adolescent↗

PubMedDate not supplied

Diffusion-weighted MR imaging with single-shot echo-planar imaging in the upper abdomen: preliminary clinical experience in 61 patients.

BACKGROUND: To determine the potential ability of diffusion-weighted magnetic resonance (MR) imaging with single-shot echo-planar imaging (DW imaging) in the upper abdomen by apparent diffusion coefficient (ADC) and signal:intensity ratio (SIR) measurements. METHODS: DW imaging was performed in 61 clinical patients. ADCs in the liver, pancreas, spleen, kidney, and different pathological conditions were calculated. Spleen-to-liver SIR and segmental intensity difference of the liver (SID) were also calculated. RESULTS: The mean ADCs (mm(2)/s) were 2.28 x 10(-3) +/- 0.07 in the liver, 1.44 x 10(-3) +/- 0.05 in the spleen, 1.94 x 10(-3) +/- 0.19 in the pancreas, and 5.76 x 10(-3) +/- 0.06 in the kidney. The mean ADC of cirrhotic liver was 1.96 x 10(-3) +/- 0.62, which was lower than that of normal liver. Other pathologic conditions also showed ADCs different from those of normal tissues. All DW images showed significantly higher spleen-to-liver SIRs and SIDs than did T2-weighted images (p < 0.05). CONCLUSION: The mean ADCs obtained with DW imaging were different in each upper abdominal organ and with each pathologic condition. DW images showed better soft tissue contrast than did T2-weighted images with regard to SIR and CNR in depicting and characterizing upper abdominal disorders.

Adult↗

PubMedDate not supplied

CT evaluation of invasive trophoblastic disease.

We report the use of dynamic CT for the evaluation of trophoblastic disease of the uterus. In five cases showing evidence of persistent trophoblastic disease after evacuation of a molar gestation, contrast enhancement of the myometrium demonstrated several hypodense foci surrounded by highly enhanced areas. These observations were not found in two cases of successfully evacuated hydatidiform mole without sequela. A case of choriocarcinoma showed a large central nonenhanced lesion with peripheral contrast enhancement. Filling defects in a markedly contrast enhanced lesion probably represent hydatids penetrating the myometrium and should suggest invasive mole.

Adult↗

PubMedDate not supplied

Transient hepatic attenuation differences on dynamic computed tomography.

Transient hepatic attenuation differences (THAD) are occasionally noted on dynamic CT in patients with portal vein obstruction, arterioportal shunt, liver tumor, and liver abscess. We report four additional cases of THAD with unreported and/or unexplained etiology.

Adult↗

PubMedDate not supplied

CT of calcified chronic aortic dissection simulating atherosclerotic aneurysm.

Calcification along the outermost aspect of the aorta usually means atherosclerotic aneurysm. On occasion, however, this peripheral type calcification is seen in chronic aortic dissection and leads to a misdiagnosis. Conventional chest roentgenography and CT of 50 cases of chronic dissection proven by angiography were reviewed. Four of these cases (8%) showed calcification in the outermost wall of the affected portion of the aorta. Two cases were Stanford type A and the other two cases were type B. In type A cases chest roentgenography showed calcification in the wall of the dilated ascending aorta closely mimicking aneurysm. In type B cases, calcification was in the outer wall of a localized hump in the descending aorta. Computed tomography clearly demonstrated that this peripheral calcification was located in the outermost wall of the false lumen. Review of the pathologic literature shows sporadic reports of such phenomenon and a theory of endothelialization of the false lumen. It is presumed that the endothelialized false lumen may develop atheromatous changes much more rapidly than the true lumen since two of four cases showed calcification only in the wall of the false lumen with the intimal flap and the wall of the true lumen remaining noncalcified.

Aged↗

PubMedDate not supplied

Breath-held MR cholangiopancreatography with half-averaged single shot hybrid rapid acquisition with relaxation enhancement sequence: comparison of fast GRE and SE sequences.

PURPOSE: Our goal was to determine whether half-averaged single shot hybrid rapid acquisition with relaxation enhancement (single shot hybrid RARE) sequence can improve image quality, duct conspicuity, signal intensity ratio (SIR), and contrast-to-noise ratio (CNR) of MR cholangiopancreatography (MRCP) by comparing it with two other MRCP sequences: fast SE (FSE) and contrast-enhanced Fourier-acquired steady-state technique (CE-FAST). METHOD: MRCP with three sequences was obtained in 46 people (10 volunteers, 36 patients with pancreatobiliary disease). Overall image quality and duct conspicuity were graded. SIR and CNR were also measured. RESULTS: Overall image quality was graded excellent or good in all 46 patients (100%) with single shot hybrid RARE, in 38 of 46 (83%) with FSE, and in 5 of 46 (11%) with CE-FAST. Duct conspicuity was the best in single shot hybrid RARE statistically. SIR was the highest in FSE, while CNR was highest statistically in single shot hybrid RARE of three sequences. CONCLUSION: Single shot hybrid RARE can provide consistently higher quality MRCP than FSE and CE-FAST because sequential images by single shot hybrid RARE minimize respiratory, bowel, and cardiac motion artifacts.

Adolescent↗

PubMedDate not supplied

Combination of surface anatomy MRI and MR venography to demonstrate cerebral cortex and cortical veins on one image.

We assessed in 12 patients the value of MR images in which a surface anatomy scanning (SAS) image and an MR venogram are added. We obtained SAS images using the half-Fourier technique and MR venograms with the 2D phase-contrast technique. The added images provided sufficient information concerning brain surface as well as cortical veins. Their findings correlated with those at surgery in six patients who underwent scalp incision marking. This technique provides valuable anatomical information preoperatively.

Adult↗

PubMedDate not supplied

Cerebral perfusion MRI with arterial spin labeling technique at 0.5 Tesla.

PURPOSE: Our aim was to evaluate the feasibility of cerebral perfusion MRI using an arterial spin labeling technique at 0.5 T. METHOD: We performed perfusion imaging with a flow-sensitive alternating inversion recovery (FAIR) sequence in a total of 37 patients with cerebral infarction. RESULTS: FAIR perfusion images demonstrated areas of pathological perfusion corresponding (13 patients) or not corresponding (15 patients) to the infarcted area on MR images. Among 19 patients in whom comparison between FAIR perfusion imaging and regional cerebral blood flow single photon emission CT was available, the two studies correlated well in 15 patients. CONCLUSION: Our results indicate that the FAIR technique allows reliable cerebral perfusion imaging at 0.5 T.

Adolescent↗

PubMedDate not supplied

MRI of influenza encephalopathy in children: value of diffusion-weighted imaging.

PURPOSE: Our purpose was to describe the MR findings of influenza encephalopathy and assess the value of diffusion-weighted imaging for its diagnosis. METHOD: We examined a total of five patients diagnosed as having influenza encephalopathy or encephalitis by MRI, including diffusion-weighted imaging. We analyzed the conventional images and compared them with diffusion-weighted images. RESULTS: Abnormally hyperintense lesions of varying extent and location were noted on T2-weighted and fluid-attenuated inversion recovery images in the cortex and adjacent white matter in every case. They showed no contrast enhancement. Diffusion-weighted imaging demonstrated the lesions as areas of restricted proton diffusion more clearly than conventional imaging. CONCLUSION: Influenza encephalopathy is depicted as areas of T2 elongation having a rather nonspecific distribution. Diffusion-weighted imaging can demonstrate the lesions sensitively and serve as a valuable adjunct to conventional MRI.

Acute Disease↗

PubMedDate not supplied

Fast dynamic MRI of aortic dissection: flow assessment by subsecondal imaging.

PURPOSE: The aim of this study was to evaluate fast dynamic MRI, which consists of a subsecondal MRI sequence combined with a rapid contrast medium infusion technique, in examining clinical cases of aortic dissection. MATERIALS AND METHODS: The subjects consisted of 27 patients with aortic dissection. Turbo-FLASH imaging of the aorta was conducted to obtain 50 image frames within 40 seconds. RESULTS: Recognition of the intimal flap and differentiation of the true channel from the false channel was easily accomplished in all 15 patients with a patent false channel. The entry site was detected in 13 of 15 patients. Differentiation of slow flow from thrombus in the false channel was possible in all 27 cases, and the relationship between the lesion and the main branches of the aortic arch was identified in 26 of 27 cases. CONCLUSION: Fast dynamic MRI may provide a large amount of information that is useful for the diagnosis of aortic dissection.

Aortic Dissection↗

PubMedDate not supplied

MRI artifacts of metallic stents derived from imaging sequencing and the ferromagnetic nature of materials.

In vitro and in vivo studies were performed to assess the optimum materials and imaging methods for metallic stents by conducting an in vitro investigation of MRI artifacts arising during imaging by several representative imaging methods using various types of stents and by clarifying the differences occurring with different metals and imaging sequences. We also examined the use of MRCP and MRA in evaluating luminal patency within stented biliary tracts and blood vessels in vivo. In vitro study showed either no artifacts or very slight artifacts created by titanium stents, however, marked image distortion was created by a stainless steel stent. Using SE instead of GRE sequences can minimize these artifacts. Echo planar imaging (EPI) produced severe susceptibility artifacts, resulting in unsatisfactory images. In vitro and in vivo studies indicated that MRCP was an effective method for follow-up studies of bile duct stents, but that MRA is quite limited as a method of follow-up study for currently available vascular stents.

Aged↗

PubMedDate not supplied

Clinical application of single shot GRE-EPI as non-enhanced MRA (EPI-MRA) for aortic aneurysm and dissection.

We investigated the usefulness of single shot gradient echo type echo planar imaging (GRE-EPI) as magnetic resonance angiography (MRA) for the diagnosis of aortic aneurysm and dissection. This technique can detect blood flow signals in several tenths of a milliseconds without the need for contrast medium, breath-holding, or electrocardiographic (ECG) gating. By scanning approximately 20 frames in the coronal plane, three-dimensional (3D) imaging can be achieved by maximum intensity projection (MIP) at different angles. Three radiologists evaluated the ability of this single shot GRE-EPI as non-enhanced MRA (EPI-MRA) to diagnose aortic aneurysm and dissection. The examined lesions consisted of three cases of thoracic aortic aneurysm, seven of abdominal aortic aneurysm and eight of aortic dissection with a total of 15 involved aorta. In all patients with aortic aneurysm, EPI enabled detection and diagnosis of the aneurysm. However, the size of the lesion and relationship with major branches were determined only in the abdominal aorta, and could not be determined precisely in thoracic lesions. Similar results were obtained for patients with aortic dissection. The technique visualized the intimal flap and enabled determination of the extent of dissection in the abdominal aorta. In the thoracic aorta, serious magnetic susceptibility artifacts caused image distortion, and as a result only the dissection could be detected and diagnosed. No entry site was detected at either the abdominal or thoracic aorta. These results suggest that EPI-MRA may have a clinical potential for screening patients with acute aortic disease who cannot undergo physical restraint for scanning.

Aged↗