Asymptomatic occlusive lesions of carotid and intracranial arteries in Japanese patients with ischemic heart disease: evaluation by brain magnetic resonance angiography

BACKGROUND AND PURPOSE: The purpose of this study was to elucidate the prevalence and degree of asymptomatic occlusive lesions in the carotid and intracranial arteries in Japanese patients with ischemic heart disease (IHD). METHODS: We performed carotid and intracranial MR angiography (MRA) on 67 patients (49 men, 18 women; age range, 40 to 78 years; mean age, 60.1 years) who had received selective coronary angiography for the clinical diagnosis of IHD. On the basis of these images, degree of stenosis in the regions of the bilateral carotid artery bifurcation and five regions of the intracranial arteries, ie, bilateral intracranial portions of the internal carotid arteries and the middle cerebral arteries and the basilar artery were estimated. RESULTS: Stenosis of more than 25% narrowing of the diameter of the target arteries was found in 15 patients (22.4%) in the extracranial carotid arteries and in 11 patients (16.4%) in the intracranial arteries. Most of the stenotic lesions were mild. The incidence of extracranial carotid stenosis and the severity of coronary atherosclerosis showed a significant correlation. The mean age of the patients with intracranial arterial lesions was statistically higher than those without intracranial lesions. CONCLUSIONS: Our data suggest that asymptomatic occlusive lesions in the carotid and intracranial arteries are fairly common in Japanese patients with IHD, although the degree of stenosis is relatively mild. Coexistence of carotid atherosclerosis should be suspected in IHD patients with severe coronary atherosclerosis, and the possibility of atherosclerosis in the intracranial arteries should be considered in aged IHD patients.     

Magnetic resonance angiography and magnetic resonance tomography in dissection of the vertebral artery

Vertebral artery dissection (VAD) is an important cause of posterior circulation stroke in young adults. Initial symptoms are often non-specific and diagnostic arteriography is not performed until neurological deficits are obvious. Since magnetic resonance tomography (MRT) is superior in the diagnosis of vertebrobasilar ischemia, we retrospectively analyzed the role of MRT and MR angiography (MRA) in the detection of dissections of the vertebral artery. Between 1989 and 1995 we identified 24 patients with a vertebral artery dissection and 1 patient with a basilar artery dissection (8 females and 17 males, 23-60 years of age, mean 41.2 years). The diagnosis of VAD (14 left VAD, 9 right VAD, 1 bilateral VAD, 1 basilar artery dissection) was established by specific arteriographical findings (DSA) or clinical and neuroradiological course. All patients underwent a combined MRT/MRA examination protocol at 1.5T that consisted of spin-echo imaging and time of flight MRA of the intra- and extracranial arteries using 2D Flash and 3D Fisp sequences. The MRT/MRA findings were correlated to DSA and ultrasound results. During the acute and subacute stage, MRT/MRA revealed abnormal findings in 21 of 22 dissected vessels (95.5%). There was one false-negative MRT/MRA in a patient with a V1 dissection (intimal flap without peripheral flow disturbances). In 7/22 VAD the MRT/MRA findings were rated specific (double lumen n = 1, mural hematoma n = 4, pseudoaneurysm n = 2). DAS was sensitive in 100% and ultrasound in 77.3%. Specific results were obtained by DSA in 8/ 22 VAD (36.4%) and in 7/22 VAD (30.4%) by MRT/MRA. When MRT/MRA and DSA results were combined, the specific findings increased to 43.5%. Follow-up examinations revealed recanalization in 52% of initially stenosed or occluded vertebral arteries; four patients developed a pseudoaneurysm, and two of them underwent ligation of the VAD. With this retrospective approach, we were able to show a high sensitivity of MRT/ MRA for the presence of disturbed flow in the dissected vertebral artery. The MRA projections tended to overestimate stenosis and were inferior to DSA in the appreciation of irregularities of the vessel wall. Identification of high-grade stenosis, especially in the presence of distal occlusion, was improved on the MRA source images. During the acute and subacute stage, the diagnosis of luminal thrombus can be difficult, because signal ambiguities exist between hemoglobin breakdown products and flow effects and adjacent fat tissues. The differentiation between luminal thrombus and mural hematoma requires interpretation of MRA source images, together with flow compensated spin-echo images. Additional fat suppressed images and flow presaturation may be required at the appropriate levels. The identification of mural hematoma is important, because this finding is considered specific and cannot be obtained with DSA. There is a complementary role of MRT/MRA and DSA for an improved overall specificity for vertebral artery dissection. A negative MRT/MRA result in a patient with appropriate symptoms, however, cannot exclude a dissection and should prompt DSA. On the other hand, a suggestive MRT/MRA result in the appropriate clinical context can replace DSA. The advantage of MRT/MRA is that the method offers a simultaneous diagnosis of posterior fossa ischemia and vertebral artery abnormalities. Therefore, MRT/MRA should be recommended in patients with suspected VAD and especially in those who have no definite neurological deficit. These patients will benefit greatly from early diagnosis and therapy. The fact that all our patients were diagnosed after neurological symptoms and that 64% of them have residual deficits gives an ethical and economical rationale for advocating early MRT/MRA in these patients.     

The role of magnetic resonance angiography in the assessment of intracranial vascular disease

Magnetic resonance techniques have a significant role in the evaluation of intracranial vascular diseases; however, to achieve an appropriate diagnosis, a combination of both magnetic resonance imaging and angiography are needed. It is extremely important for the interpreting physician to be aware of the potential limitations of the techniques being used. With this knowledge, magnetic resonance techniques can eliminate the need for more invasive procedures. An overview of the current methods and their applications and limitations is provided.     

The usefulness of magnetic resonance angiography in surgery for intracranial aneurysms that have bled

BACKGROUND: Once it was confirmed that magnetic resonance imaging (MRI) including angiography (MRA) could demonstrate intracranial aneurysms, a study was set up to establish whether satisfactory images could be obtained to plan and execute early surgery on ruptured intracranial aneurysms without recourse to intra-arterial digital subtraction angiography (IA.DSA) in the acute phase of the illness. METHODS: All patients presenting with a subarachnoid haemorrhage (SAH) were considered for MR studies. The patient selection was based on whether they were considered fit enough to tolerate scanning and did not have a known contraindication. A standard protocol was used--a three-dimensional time-of-flight with T1 and T2-weighted sagittal and axial images. If an aneurysm was demonstrated and early surgery was undertaken they were entered into the study. RESULTS: Over a 25-month period, 122 patients were submitted for MR studies, these being selected from over 200 patients presenting with an SAH. Aneurysms were believed to be present in 55 patients who were clinically suitable for early surgery. There were 21 males and 34 females, with an age range of 23-79 years, a mean of 50.5 years. Sixty-three aneurysms in all were demonstrated and 55 of these were surgically dealt with. There were two false positives. CONCLUSION: MRI is the investigation of choice to plan surgery in those patients presenting with an SAH who, on clinical grounds, would be considered suitable for early surgery. The imaging is easily obtained, non-invasive, avoids radiation, and in view of the multiple images obtained is often superior to conventional DSA.     

Surgical decisions on the basis of magnetic resonance angiography of the carotid arteries

The recent demonstration of the efficacy of carotid endarterectomy in certain patients emphasizes the advantages of having a noninvasive, accurate means of evaluating the carotid arteries. Advances in magnetic resonance (MR) angiography now allow accurate depiction of the carotid arteries that may be adequate for surgical planning in many cases. This report examines the accuracy of MR angiography compared with that of conventional angiography in symptomatic patients undergoing carotid endarterectomy and compares them with surgical findings. Twenty-one carotid arteries in 20 patients were treated surgically for severe stenosis or occlusion. Preoperatively, all patients had both MR and conventional angiograms, which were interpreted on a five-grade scale by two independent neuroradiologists who were unaware of the patient's clinical history. The two studies were highly correlated, particularly in the case of severe stenosis and occlusion. There were no false-negative MR studies that missed surgically significant lesions. In two cases, MR angiography overestimated the stenosis by one grade. On MR angiography, surgically significant stenosis appears as focal areas of signal intensity loss at the level of stenosis with reappearance of the signal distally. If the distal signal intensity does not reappear, the artery is likely to be occluded. In symptomatic patients, MR angiograms that demonstrate a flow-void gap with distal reappearance at a site consistent with the symptoms may be adequate as the sole preoperative study. Three patients who underwent carotid endarterectomy on this basis are presented. The factors that contribute to artifactual and overestimated stenosis are reviewed.     

Clinical application of magnetic resonance angiography for coronary arteries: correlation with conventional angiography and evaluation of imaging time

Magnetic resonance angiography (MRA) of the coronary arteries is a particularly difficult task because of the small size of the vessels and cardio-respiratory motion. The authors describe a method of performing of ultrafast MRA of the coronary arteries with a standard MR system and body coil. Each image was obtained within a single breath hold by "segmented Turbo FLASH" sequences using an electrocardiography gate. Clinical application was performed in 20 patients with ischemic heart disease, and a comparison was made with conventional coronary angiography. The imaging time was shortened significantly by our methods. The diagnosis was made by at least two different images to avoid false positives. The results indicated a good correlation between MRA and conventional angiography.     

Combined use of duplex imaging and magnetic resonance angiography for evaluation of patients with symptomatic ipsilateral high-grade carotid stenosis

PURPOSE: Advances in cerebral vascular imaging suggest that patients with critical levels of carotid artery stenosis (> 70%) who have symptoms can be identified accurately and necessary information about the intracranial and extracranial circulation obtained before surgery without conventional angiography. We have used carotid duplex imaging in combination with magnetic resonance angiography (MRA) to evaluate 20 patients with symptomatic ipsilateral high-grade carotid stenosis. METHODS: All patients underwent CT and magnetic resonance imaging brain scans, as well as MRA and conventional arteriography of the cerebral circulation. Magnetic resonance angiograms were obtained with two-dimensional phase contrast and time-of-flight techniques. Phase contrast was used for intracranial vascular imaging and for determining qualitative flow velocities and the direction of blood flow in the circle of Willis. Two-dimensional time of flight was used to assess the carotid bifurcations. RESULTS: Twenty patients with symptoms (six with strokes, 11 with transient ischemic attacks, and three with amaurosis fugax) had duplex evidence of high-grade carotid stenoses. Computed tomographic and magnetic resonance brain scans were positive for cerebral infarction in six patients with clinical strokes. Comparison of MRA with conventional angiography was 91% accurate for high-grade stenoses and occlusions (sensitivity 100% and specificity 90% for stenosis; sensitivity/specificity was 100% for complete occlusion). Comparison of duplex imaging with conventional angiography demonstrated 86% accuracy for detection of severe stenosis or occlusion (sensitivity 94% and specificity 89% for stenosis; sensitivity and specificity were 100% for complete occlusion). CONCLUSIONS: This study suggests that combined use of MRA and duplex imaging is accurate for detection and evaluation of high-grade carotid stenoses in patients with symptoms.     

Fat-suppressed gadolinium-enhanced three-dimensional magnetic resonance angiography adequately depicts the status of iliac arteries following atherectomy and stent placement

Members of a large family of proteins, called the DEAD box family, are ribonucleic acid binding proteins with ATPase activity. Recent investigations into the developmentally and cell type-specific expression patterns of one family member, p68 RNA helicase, suggest that this protein might play a role in organ differentiation and/or maturation, and that its expression is subject to complex regulation.     

Detection of joint pathology by magnetic resonance imaging in patients with early rheumatoid arthritis

Magnetic resonance imaging (MRI) permits the visualization of anatomical structures not appreciated by conventional radiographic imaging, and may assess inflammatory disease and its progression with greater sensitivity than conventional radiography. In this study of 30 patients with early rheumatoid arthritis (RA), which could be considered as a pilot study because of the relatively small number of patients, we compare MRI of the knee and the fifth metatarsophalangeal joint with clinical and radiographic findings. A parallel study of 10 healthy individuals served as a reference group. In all but one of the 30 patients, MRI revealed some kind of joint abnormality, whereas conventional radiography was normal in 14 patients. The present study thus suggests that MRI may detect inflammatory and/or destructive joint changes in patients with early RA, and that these changes may occur in the absence of clinical symptoms or signs and/or radiographic signs in the examined joint. If these data prove to be confirmed in further controlled studies, MRI may be of importance both for the assessment of prognosis and for the decision to treat in the early critical stages of RA.     

The clinical utility of magnetic resonance imaging in 3-dimensional treatment planning of brain neoplasms

Results of the clinical experience gained since 1986 in the treatment planning of patients with brain neoplasms through integration of magnetic resonance imaging (MRI) into computerized tomography (CT)-based, three-dimensional treatment planning are presented. Data from MRI can now be fully registered with CT data using appropriate three-dimensional coordinate transformations allowing: (a) display of MRI defined structures on CT images; (b) treatment planning of composite CT-MRI volumes; (c) dose display on either CT or MRI images. Treatment planning with non-coplanar beam arrangements is also facilitated by MRI because of direct acquisition of information in multiple, orthogonal planes. The advantages of this integration of information are especially evident in certain situations, for example, low grade astrocytomas with indistinct CT margins, tumors with margins obscured by bone artifact on CT scan. Target definitions have repeatedly been altered based on MRI detected abnormalities not visualized on CT scans. Regions of gadolinium enhancement on MRI T1-weighted scans can be compared to the contrast-enhancing CT tumor volumes, while abnormalities detected on MRI T2-weighted scans are the counterpart of CT-defined edema. Generally, MRI markedly increased the apparent macroscopic tumor volume from that seen on contrast-CT alone. However, CT tumor information was also necessary as it defined abnormalities not always perceptible with MRI (on average, 19% of composite CT-MRI volume seen on CT only). In all, the integration of MRI data with CT information has been found to be practical, and often necessary, for the three-dimensional treatment of brain neoplasms.     

Magnetic resonance angiography with TOF-TONE tridimensional sequences in the study of steno-occlusive diseases of the renal arteries. Comparison with digital angiography

The authors examined 32 patients (68 renal arteries in all) with suspected renovascular hypertension with MRA (3D TOF-TONE sequences) and DSA. MRA visualization of the renal vessels was considered good in 96.8%, 91.6%, 76.6% and 16.6% of cases for the ostium, the proximal third, the distal third and the hilum, respectively. MRA correctly assessed the 4 occlusions in our series and 19/20 atherosclerotic stenoses, all in proximal site. In proximal stenosis detection, MRA had 100% sensitivity and 98% specificity in atherosclerotic sclerosis-occlusion grading considering a 50% caliber reduction as the cut-off value. The two techniques were in agreement in 68% of cases; MRA overestimated stenosis grade in 25% of cases. The 3D TOF-TONE sequence is a reliable diagnostic tool in the study of the proximal tract of the renal arteries, but its major limitation remains in distal tract studies. Nevertheless, this technique has elective indications in a selected group of patients, namely the elderly with hypertension and impaired renal function.     

Evaluation of aortic distensibility in patients with essential hypertension by using cine magnetic resonance imaging

The rabbit liver microsomal biotransformation of alpha-methylstyrene (1a), 2-methyl-1-hexene (1b), 2,4,4-trimethyl-1-pentene (1c), and 1,3,3-trimethyl-1-butene (1d) has been investigated with the aim at establishing the enantioface selection of the cytochrome P-450-promoted epoxidation of the double bond and the enantioselectivity of microsomal epoxide hydrolase(mEH)-catalyzed hydrolysis of the resulting epoxides. GLC on a Chiraldex G-TA (ASTEC) column was used to determine the enantiomeric composition of the products. The epoxides 2 first produced in incubations carried out in the presence of an NADPH regenerating system were not detected, being rapidly hydrolyzed by mEH to diols 3. The enantiomeric composition of the latter showed that no enantioface selection occurred in the epoxidation of 1c and 1d, and a very low (8%) ee of the (R)-epoxide was formed from 1b. Incubation of racemic epoxides 2b-d with the microsomal fraction showed that the mEH-catalyzed hydrolysis of 2c and 2d was practically nonenantioselective, while that of 2b exhibited a selectivity E = 4.9 favoring the hydrolysis of the (S)-enantiomer. A comparison of these results with those previously obtained for linear and branched chain alkyl monosubstituted oxiranes shows that the introduction of the second alkyl substituent suppresses the selectivity of the mEH reaction of the latter and reverses that of the former substrates.     

A study of radiation necrosis and edema in the canine brain using positron emission tomography and magnetic resonance imaging

Evidence derived from sequence comparisons and the genomic organization of the murine Antennapedia-class homeobox gene clusters suggest that they arose from a primordial cluster through a process of gene duplication and divergence followed by cluster duplication. A large chromosomal domain surrounding the ancestral homeobox cluster also appears to have been duplicated and has remained relatively stable since the divergence of humans and rodents. To test the extent of the duplicated chromosomal domain, we have initiated physical mapping studies of the regions surrounding the four murine homeobox clusters using pulsed-field gel electrophoresis and yeast artificial chromosome cloning. In this study, we present a long-range restriction map of mouse chromosome 11 spanning 1500 kb in the region surrounding the Hox-b cluster. We have determined that the gene for the nerve growth factor receptor is tightly linked to the Hox-b complex and is located within 50 kb of the Hox-b 1 gene at the 3' end of the cluster. Four yeast artificial chromosomes have been isolated and characterized by the polymerase chain reaction, long-range restriction mapping, and Southern blotting. Two clones of 150 and 300 kb contain the entire Hox-b cluster and the nerve growth factor receptor gene. A 440-kb clone contains the 3' end of the Hox-b cluster, the nerve growth factor receptor gene, and extends downstream. A 210-kb clone contains the 5' end of the Hox-b cluster and extends upstream. These clones confirm the pulsed-field restriction map of uncloned mouse DNA and represent a contig of approximately 600 kb of cloned material from mouse chromosomes 11.     

Arterial-phase three-dimensional gadolinium magnetic resonance angiography of the renal arteries. Strategies for timing and contrast media injection: original investigation

RATIONALE AND OBJECTIVES: The authors review different imaging and contrast-media infusion strategies for arterial-phase three-dimensional (3D) gadolinium-enhanced magnetic resonance angiography (Gd-MRA). METHODS: The influence of physicochemical factors on the infusion of contrast media, including viscosity, flow rate, inline pressure, and cannula size, is assessed. The combination of manual or automated contrast-media administration with timing-dependent or -independent 3D Gd-MRA techniques is reviewed regarding the aspects of effectiveness, robustness, image quality, and costs. RESULTS: For effective bolus delivery with high flow rates, the type and temperature of the contrast media, the size of the cannula, and an immediate saline flush must be considered. Timing-dependent techniques based on a test bolus and using automated contrast-media infusion as well as timing independent techniques such as MR SmartPrep or multiphase 3D Gd-MRA by using a manual injection with a SmartSet tubing set, are all effective procedures for arterial phase 3D Gd-MRA. CONCLUSIONS: Manual contrast-media injection with a tubing set can be used for timing-independent MRA techniques. The multiphase 3D Gd-MRA approach seems to be favorable for different MR systems, robustness, and speed.     

The torcular Herophili: the diagnostic pitfalls in TOF 3D magnetic resonance angiography

The authors report on a diagnostic pitfall which is often observed in magnetic resonance angiography (MRA) of intracranial vessels (time-of-flight 3D)--i.e., the absence of one of the two transverse sinuses. Fifty patients underwent MRA of the intracranial vessels with the TOF 3D (FISP) and the TOF 2D (FISP) techniques. Five patients were affected with sinus stenosis. MRA was performed with a 1.5-T superconductive magnet and a circular head coil. All patients underwent Magnetic Resonance Angiography with FISP 2D sequences (FA 40 degrees, TR 40 ms, TE 12 ms) acquired on coronal plane as well as FISP 3D (FA 15 degrees, TR 30 ms, TE 7 ms) acquired on axial plane. In the patients in whom FISP 2D sequences correctly demonstrated the whole confluence of sinuses, FISP 3D sequences always depicted the upper sagittal sinus, while the right transverse sinus was seen in 84.4% (38/45) of cases and the left transverse sinus in 24.2% (11/45) of cases. In the patients with a stenosis in the confluence of sinuses, FISP 3D sequences demonstrated two false-positive cases with respect to FISP 2D. The statistical analysis (McNemar test) of the results demonstrated the difference between 2D and 3D sequences in the detection of the two transverse sinuses to be statistically significant: p < 0.01 for the right transverse sinus and p < 0.001 for the left transverse sinus. In the study of the intracranial vessels (TOF 3D technique) the absence of one of the two transverse sinuses is suggestive of a diagnostic pitfall; the combination of 3D and 2D sequences answers this diagnostic question.     

The effect of image resolution on vessel signal in high-resolution magnetic resonance angiography

In this paper, the theoretical dependence of the signal of flowing fluids is considered in terms of the imaging parameters and the physical condition of the flowing fluid. For the vessel sizes, flow ranges, and imaging conditions studied, it is demonstrated that the fluid signal can be predicted from the solution of Bloch equations. For vessels on the order of the imaging resolution or smaller, the effects of the image resolution must be included