[Mitral valve replacement for mitral regurgitation caused by papillary muscle head rupture complicating acute myocardial infarction: report of a case].

A 71-year-old female was admitted for acute posterolateral infarction. On the next day of the successful emergency perctaneous coronary intervention, she developed severe dyspnea and was intubated at intensive care unit. Massive mitral regurgitation was detected on color Doppler imaging and left ventricular cardiac failure was increasingly developed. The urgent operation was performed for papillary muscle rupture 18 days after first episode. Head rupture of the posterior papillary muscle was found during surgery and the mitral valve was replaced by a prosthetic valve (SJM # 25). The postoperative course was uneventful and she discharged on 52 days after surgery.

Volume-rendered 3D display of MR angiograms in the diagnosis of cerebral arteriovenous malformations.

PURPOSE: To determine whether application of a volume-rendered display of 3D time-of-flight (TOF) MR angiography could assist the diagnosis of cerebral arteriovenous malformations (AVMs). MATERIAL AND METHODS: Volume-rendered 3D images of postcontrast 3D time-of-flight MR angiography were compared with conventional angiograms in 12 patients. The correlation between the 3D images and the operative findings was also analyzed in 5 patients. RESULTS: The 3D-displayed images showed all of the feeders and drainers in 10 and 9 patients, respectively. In all patients, the nidus was three-dimensionally visualized. In 3 patients with hematomas, the relationship between the hematoma and the AVM was well demonstrated. The 3D images corresponded well with the operative findings in the 5 patients. CONCLUSION: This method is of help in assessing the relationship between the components of an AVM as well as that between an AVM and an associated hematoma.

Diffusion-weighted MRI of subdural and epidural empyemas.

We reviewed diffusion-weighted images (DWI) from eight patients with subdural and four with epidural empyemas to assess the possibility of differentiating between these lesions by DWI. The signal intensities of the empyemas on DWI, and maps of the apparent diffusion coefficient (ADC) were analysed in seven patients. In seven of the eight patients with subdural empyema, the lesions appeared as areas of high signal. The ADC maps confirmed that these areas were the result of restricted diffusion. (In the remaining patient, the lesion showed a mixture of high and low signal.) The epidural empyemas contained areas of low signal in all four patients; part of the empyema was isointense or gave high signal in two. DWI may be an adjunct to conventional sequences for differentiating between subdural and epidural empyemas.

Diffusion-weighted MRI of the cervical spinal cord using a single-shot fast spin-echo technique: findings in normal subjects and in myelomalacia.

We have implemented a new diffusion-weighted MRI (DWI) sequence based on the single-shot fast spin-echo technique. We hypothesised that this would add information to conventional MRI for diagnosis of lesions of the cervical spinal cord. DWI was performed using a technique in which echo collection after the application of motion-probing gradients was done in the same manner as in the single-shot fast spin-echo technique. We first imaged six healthy volunteers to demonstrate the cervical spinal cord using the sequence. Then we applied the sequence to 12 patients with cervical myelomalacia due to chronic cord compression. The spinal cord was well seen in all subjects without the distortion associated with echo-planar DWI. In the patients, lesions appeared as areas of low- or isointense signal on DWI. Calculated apparent diffusion coefficients of the lesions (3.30+/-0.38x10(-3) mm(2)/s) were significantly higher than those of normal volunteers (2.26+/-0.08x10(-3) mm(2)/s). Increased diffusion in areas of cervical myelomalacia, suggesting irreversible damage, can be detected using this technique.

Diffusion-weighted MR imaging of Carmofur-induced leukoencephalopathy.

Carmofur (1-hexylcarbamyl-5-fluorouracil), a derivative of 5-fluorouracil (5-FU), has been widely used in Japan as a postoperative adjuvant chemotherapy agent for colorectal and breast cancer. Periventricular hyperintensity on T2-weighted MR images in carmofur-induced leukoencephalopathy confront the physician with a broad range of differential diagnoses. We describe two cases of carmofur-induced leukoencephalopathy in which diffusion-weighted MR imaging revealed periventricular hyperintensity. We compared their findings with those of age-related periventricular hyperintensity in five patients and found discrepancies in signal intensity of periventricular areas. Our results suggest that diffusion-weighted MR imaging may be useful to differentiate carmofur-induced leukoencephalopathy from age-related periventricular hyperintensity.

Non-contrast enhanced MR venography using 3D fresh blood imaging (FBI): initial experience.

OBJECTIVE: This study examined the efficacy of 3D-fresh blood imaging (FBI) in patients with venous disease in the iliac region to lower extremity. MATERIALS AND METHODS: Fourteen patients with venous disease were examined [8 deep venous thrombosis (DVT) and 6 varix] by 3D-FBI and 2D-TOF MRA. All FBI images and 2D-TOF images were evaluated in terms of visualization of the disease and compared with conventional X-ray venography (CV). RESULTS: The total scan time of 3D-FBI ranged from 3 min 24 sec to 4 min 52 sec. 3D-FBI was positive in all 23 anatomical levels in which DVT was diagnosed by CV (100% sensitivity) as well as 2D-TOF. The delineation of collateral veins was superior or equal to that of 2D-TOF. 3D-FBI allowed depiction of varices in five of six cases; however, in one case, the evaluation was limited because the separation of arteries from veins was difficult. CONCLUSION: The 3D-FBI technique, which allows iliac to peripheral MR venography without contrast medium within a short acquisition time, is considered clinically useful.

Duct-penetrating sign at MRCP: usefulness for differentiating inflammatory pancreatic mass from pancreatic carcinomas.

PURPOSE: To define the duct-penetrating sign at magnetic resonance (MR) cholangiopancreatography (MRCP) and to assess the usefulness of this sign for distinguishing an inflammatory pancreatic mass (IPM) from a conventional pancreatic carcinoma (CPC) compared with arterial phase computed tomography (hereafter, CT) and arterial phase MR imaging (hereafter, MR imaging). MATERIALS AND METHODS: MRCP, CT, and MR images were compared by means of receiver operating characteristic (ROC) analysis for 11 IPMs and 43 CPCs. With the MRCP images, a morphologic classification of the main pancreatic duct (MPD) was attempted for all lesions. On the basis of this classification and the enhancement patterns of a lesion, all readers graded the presence of IPM or CPC on a five-point scale for all images. RESULTS: On the MRCP images, the morphologic characteristics of the MPD were nonobstruction for IPM (28 of 33, 85%) and obstruction or irregular stenosis for CPC (124 of 129, 96%). At ROC analysis among all the techniques, MRCP images had the highest value (0.98) for significant areas under the ROC curve (CT, 0.84; MR, 0.76) (P <.001). For the duct-penetrating sign in the broad sense (nonobstructed MPD) and the sign in the narrow sense (only normal MPD), the sensitivity, specificity, and accuracy for diagnosis of IPM were 85%, 96%, and 94%, respectively, and 36%, 100%, and 87%, respectively. CONCLUSION: The duct-penetrating sign on MRCP images was more helpful to distinguish IPM from CPC than were the enhancement patterns on CT and MR images.

Preliminary evaluation of volume-rendered three-dimensional display of time-of-flight MR angiography in the diagnosis of intracranial aneurysms.

We assessed the value of the volume-rendering method of displaying images of three-dimensional (3D) time-of-flight MR angiography (MRA) in the diagnosis of intracranial aneurysms. We obtained three-dimensional volume-rendered MRA from 21 patients with intracranial aneurysms. The images were evaluated in comparison with maximum-intensity-projection images (in 21 patients), conventional angiograms (in 21) and CT angiography (in nine). In 17 patients, 3D volume-rendered images were thought to show morphological features most clearly. They were superior to the other methods for demonstrating the precise location of the aneurysm in three patients and in showing the shape of the bleb in another three. 3D volume-rendered MRA can be effectively added to conventional imaging techniques for diagnosis of intracranial aneurysms.

Magnetic resonance cholangiopancreatography for diagnosing hepatolithiasis.

BACKGROUND/AIMS: Direct cholangiography with endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography sometimes fails to adequately opacify the entire biliary tract, because of severe biliary obstruction caused by ductal stricture or lodged stones. We assessed the diagnostic accuracy of magnetic resonance cholangiopancreatography for hepatolithiasis. METHODOLOGY: Five patients with hepatolithiasis underwent ultrasonography, computed tomography, direct cholangiography, and magnetic resonance cholangiopancreatography, using a half-Fourier acquisition single-shot turbo spin-echo sequence. Surgical exploration or pathologic examination revealed stricture and dilatation of the intrahepatic ducts in all patients. Diagnostic accuracies for stones and ductal abnormalities were compared among the imaging studies. RESULTS: No complications occurred during magnetic resonance cholangiopancreatography studies. Magnetic resonance cholangiopancreatography fully depicted the biliary tract. Magnetic resonance cholangiopancreatography accurately detected and localized intrahepatic stones, as well as bile duct stricture and dilatation, in all patients. Intrahepatic stones were detected by endoscopic retrograde cholangiopancreatography in one of four patients and by percutaneous transhepatic cholangiography in all three who underwent this procedure. Endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography demonstrated ductal stricture in all patients but failed to completely demonstrate the biliary tree in three of four patients, and one of three, respectively. On ultrasonography and computed tomography, precise localization of stones was difficult. Ultrasonography and computed tomography failed to demonstrate ductal stricture in one and two of the five patients, respectively. CONCLUSIONS: Magnetic resonance cholangiopancreatography diagnoses intrahepatic stones and bile duct abnormalities less invasively and more accurately than endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography.

FLAIR MR imaging for diagnosing intracranial meningeal carcinomatosis.

OBJECTIVE: The purpose of this study was to compare unenhanced and contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging with other sequences to visualize meningeal carcinomatosis. MATERIALS AND METHODS: Unenhanced FLAIR images were compared with spin echo T2-weighted and contrast-enhanced FLAIR images in five patients with documented meningeal carcinomatosis and four patients with suspected meningeal carcinomatosis. Comparisons were also made between contrast-enhanced T1-weighted and FLAIR images. RESULTS: In six patients, the unenhanced FLAIR images showed areas of abnormal hyperintensity within the sulci that were not noted on the spin-echo T2-weighted images. In all patients, the contrast-enhanced FLAIR images also showed meningeal enhancement, periventricular enhancement, or both. The contrast-enhanced T1-weighted and FLAIR images were equivalent in their depiction of abnormal enhancement in five of the nine patients; contrast-enhanced FLAIR images were superior in three patients. CONCLUSION: Unenhanced FLAIR images are of more value than spin-echo T2-weighted images for the diagnosis of intracranial meningeal carcinomatosis. Contrast-enhanced FLAIR images can sometimes surpass contrast-enhanced T1-weighted images in their quality.

MR digital subtraction angiography of cerebral arteriovenous malformations.

BACKGROUND AND PURPOSE: Although phase-contrast MR angiography provides some information regarding hemodynamics of cerebral arteriovenous malformations (AVMs), most conventional MR angiographic techniques have not been helpful in this respect. We attempted to determine the value of MR digital subtraction angiography (DSA) in assessing AVM hemodynamics. METHODS: We developed an MR DSA technique by combining rapid thick-section T1-weighted imaging with a bolus injection of contrast material. The temporal resolution was 0.56 to 0.61 seconds per scan. MR DSA images obtained from 14 patients with AVMs were reviewed. Anatomic depiction of each component of the AVM was rated using a four-point grading scale (excellent = 3, good = 2, fair = 1, poor = 0) to compare conventional vs MR angiograms. RESULTS: We were able to obtain serial images in which passage of contrast material was evident within the AVM, although the sequence we used allowed images to be obtained in only one projection. The average score for feeders, nidi, and drainers was 1.6, 2.4, and 2.3, respectively, with an overall average of 2.1. CONCLUSION: The spatial resolution of our technique may fall below the level needed for identification of small vascular components of an AVM. Additionally, the limited slab may restrict application of the technique to assessment of large or very small AVMs. MR DSA, however, can show the hemodynamics of AVMs and may serve as a supplement to conventional MR imaging in the diagnosis of cerebral AVMs.

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.

Pre- and postcontrast FLAIR MR imaging in the diagnosis of intracranial meningeal pathology.

PURPOSE: Few reports address the use of fluid-attenuated inversion-recovery (FLAIR) images of the brain in the diagnosis of extraaxial lesions. Our purpose was to assess the value of FLAIR images, including postcontrast ones, in the diagnosis of intracranial meningeal diseases. METHODS: We reviewed precontrast (n=24) and postcontrast (n=20) FLAIR images obtained from 25 patients with infectious meningitis (n=13), carcinomatous meningitis or dissemination of primary brain tumor (n=7), dural metastasis (n=3), and others (n=2) in comparison with fast spin-echo T2-weighted and postcontrast T1-weighted images. RESULTS: In lesion detectability, precontrast FLAIR images were significantly superior to fast spin-echo T2-weighted images but inferior to postcontrast T1-weighted images. There was no significant difference between postcontrast T1-weighted and FLAIR images. CONCLUSION: Precontrast FLAIR images can substitute for conventional fast spin-echo T2-weighted images. Postcontrast FLAIR images have diagnostic potential equivalent to conventional postcontrast T1-weighted images.

Quantitative evaluation of coronary stenosis by coronary magnetic resonance angiography.

Coronary magnetic resonance angiography (coronary MRA) can detect, noninvasively, a high proportion of severe stenotic lesions found on coronary angiograms. However, quantitative evaluation of coronary artery stenosis by coronary MRA has been performed only in a small number of patients. This study was designed to determine whether coronary MRA can assess the degree of stenosis using the two-dimensional segmented turbo-FLASH method (2D method). We studied 108 patients with technically adequate coronary MRA images. The blood flow signal intensity on coronary MRA was classified as markedly decreased, moderately decreased, or normal. The severity of coronary artery stenosis was determined by the caliper method, and coronary stenosis was rated using a seven-point scale (0%, 25%, 50%, 75%, 90%, 99%, and 100%) in accordance with the American Heart Association classification system. Patients were classified into three groups: normal coronary artery (0%-25% stenosis), moderate stenosis (50%-75% stenosis), and severe stenosis (90%-100% stenosis). The degree of stenosis on coronary angiography and the decrease in coronary MRA signal intensity were compared. The right coronary artery was evaluated in 64 patients and the left coronary artery in 73 patients. When a marked or moderate decrease in coronary MRA blood flow signal intensity was defined as indicating stenosis, the sensitivity and specificity of coronary MRA for detecting angiographically severe stenosis were 85% and 80%, respectively. A moderate decrease in coronary MRA blood flow signal intensity detected angiographically moderate stenoses with a sensitivity of 38% and a specificity of 83%. Coronary MRA can detect a high proportion of severe stenoses but only a low proportion of moderate stenoses. Technical improvements are required before coronary MRA can be used clinically.

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.

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.

Diffusion-weighted MR imaging in multiple sclerosis: comparison with contrast-enhanced study.

OBJECTIVE: To assess the utility of cerebral diffusion-weighted MR imaging in the diagnosis of multiple sclerosis (MS) in comparison with contrast-enhanced T1-weighted imaging. METHODS AND MATERIALS: We reviewed T2-weighted spin-echo (SE), fluid-attenuated inversion-recovery (FLAIR), contrast-enhanced T1-weighted SE and echo-planar diffusion-weighted images (DWIs) obtained in seven patients with definite MS on nine occasions. RESULTS: In total, 94 plaques were demonstrated on T2-weighted SE and/or FLAIR images. A total of 13 of these plaques showed enhancement on contrast-enhanced T1-weighted images and hyperintensity on DWIs, and five non-enhancing plaques showed hyperintensity on DWIs. CONCLUSION: Diffusion-weighted imaging, which provides information based on pathophysiology different from contrast-enhanced imaging, is a potential supplementary technique for characterizing MS plaques.

Coronary MR angiography-a clinical experience in Japan.

Magnetic resonance angiography (MRA) has been expected to provide a useful noninvasive means of assessing coronary artery disease as this disease continues to increase due to westernization of life style. Several Japanese investigators have assessed the diagnostic value of two-dimensional (2D) and 3D coronary MRA in clinical patients evaluated for ischemic heart disease. Almost all reports indicate a high correlation between findings on 2D MRA and findings on conventional coronary angiography (CAG) in patients with severe stenosis of proximal arteries. However, in our study involving 153 patients with ischemic heart disease, 2D MRA tended to underestimate lesions in patients with moderate stenotic lesions. Furthermore, this method could not be applied successfully in approximately 15% of our patients due to difficulty with breath-holding. These findings indicate some of the limitations associated with breath-holding in the 2D method. Recently, several reports have described high diagnostic accuracy using respiratory-gated 3D MRA with navigator echo. Effective use of a suitable contrast agent with better spatial and time resolution and better image reconstruction methods will enable 3D MRA to serve a useful role, even in screening for coronary artery disease. J. Magn. Reson. Imaging 1999;10:709-712.

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.

Diffusion-weighted MR imaging of encephalitis.

OBJECTIVE: Our purpose was to evaluate how well diffusion-weighted MR imaging shows viral or bacterial encephalitis in comparison with conventional MR imaging that includes T1- and T2-weighted spin-echo and fluid-attenuated inversion-recovery sequences. CONCLUSION: In nine of the 13 patients examined, diffusion-weighted imaging was superior to other diagnostic imaging sequences (fluid-attenuated inversion-recovery sequences in eight patients and a T2-weighted spin-echo sequence in one patient). Diffusion-weighted imaging can serve as a method of detecting early encephalitic changes.