Cerebral proliferative angiopathy depicted by four-dimensional computed tomographic angiography: A case report

Cerebral proliferative angiopathy is a rare cerebrovascular disorder characterized by diffuse abnormal vessels with intermingled brain parenchyma fed by many arteries and draining into many veins without high-flow arteriovenous shunts, which is usually confirmed by conventional digital subtraction angiography. However, dilution of the contrast medium due to the markedly increased blood flow and volume in cerebral proliferative angiopathy leads to low-contrast angiography. We report a 53-year-old man with cerebral proliferative angiopathy who underwent CT, MR imaging, MR angiography, digital subtraction angiography and 4D-CTA. The 4D-CTA exhibited abnormal vessels without early venous filling between the atrophic brain parenchyma in higher contrast than the angiography due to high spatial and time resolution, whereas the left external carotid angiography visualized the characteristic transdural supply more clearly than the 4D-CTA due to high vascular selectivity. Therefore, novel 4D-CTA and conventional angiography plays a complementary role in the accurate diagnosis of cerebral proliferative angiopathy. Taking invasiveness into account, 4D-CTA may be advantageous for the diagnosis of cerebral proliferative angiopathy based on the characteristic imaging findings.     

MR of hereditary hemorrhagic telangiectasia: prevalence and spectrum of cerebrovascular malformations.

PURPOSEOur goal was to describe the prevalence and types of cerebral vascular malformations (CVMs) seen with MR imaging in patients with hereditary hemorrhagic telangiectasia (HHT).METHODSWe reviewed retrospectively the brain MR images of 184 consecutive patients with HHT. Catheter angiography was performed in 17 patients with CVMs detected on MR images.RESULTSMR imaging revealed 63 CVMs in 42 patients. Classic arteriovenous malformations (n = 10) had a conspicuous network of vessels with flow voids and enlarged adjacent pial vessels. Apparent venous malformations (n = 5) were best seen after administration of contrast material as a prominent vessel coursing through normal brain parenchyma. Indeterminate vascular malformations (n = 48) had a spectrum of appearances characterized by variable combinations of heterogeneous signal intensity, enhancement, or hemosiderin. Angiography in 17 patients revealed 47 CVMs. Forty-six were arteriovenous malformations (AVMs), including 25 CVMs not seen with MR imaging and 21 CVMs that by MR criteria included 8 AVMs and 13 indeterminate vascular malformations. Angiography confirmed 1 venous malformation seen with MR imaging but failed to detect 3 indeterminate lesions revealed by MR imaging.CONCLUSIONMR imaging of a large cohort of consecutive patients with HHT revealed a CVM prevalence of 23% (42/184). Most CVMs (48/63) have an atypical appearance for vascular malformations on MR images. Angiographic correlation suggests that MR imaging underestimates the prevalence of CVMs and that the majority of indeterminate CVMs, despite their variable MR appearance, are AVMs.     

Three-dimensional phase-contrast MR angiography in the head and neck: preliminary report

Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnormalities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angiograms in 37 min and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of arteriovenous malformations were well delineated; aneurysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities.     

Three-dimensional phase-contrast MR angiography in the head and neck: preliminary report

Morbidity and possible mortality associated with contrast angiography lead to its cautious use. A noninvasive method for screening and further delineating known abnormalities would be welcomed. This article reviews the initial results and application of MR imaging to vascular imaging in the head and neck. By using the three-dimensional phase-sensitive method of Dumoulin, Souza, and collaborators, we acquired MR angiograms in 37 min and portrayed blood flow in all the major arteries and veins. Feeding arteries and draining veins of arteriovenous malformations were well delineated; aneurysms as small as 3-4 mm were shown, and obstructed cerebral vessels and the patency of a highly stenotic internal carotid artery were demonstrated. MR angiography of the head or neck offers great promise as a noninvasive means of studying vascular abnormalities.     

Spinal vascular malformations: MR angiography after treatment

PURPOSE: To evaluate the role of magnetic resonance (MR) angiography in the assessment of spinal vascular malformation therapy. MATERIALS AND METHODS: Thirty-four patients with spinal vascular malformations (30 dural arteriovenous fistulas, two perimedullary arteriovenous fistulas, and two intramedullary arteriovenous malformations) underwent MR angiography and MR imaging before and after endovascular or surgical treatment. RESULTS: MR angiography showed residual flow in perimedullary vessels in seven patients with dural fistula after embolization with liquid adhesive. In all seven, treatment failure was confirmed with arteriography. Long-lasting disappearance of flow in perimedullary vessels was demonstrated at MR angiography in 22 patients with dural fistula. MR imaging demonstrated normalization of spinal cord volume in 16 of 22 patients and signal intensity on T2-weighted images in three patients. Disappearance of cord enhancement was observed in five of 21 patients and of perimedullary enhanced vessels in six of 13 patients. In one additional patient with dural fistula treated with embolization, early posttreatment MR angiography showed disappearance of flow in perimedullary vessels, which reappeared at follow-up and was consistent with reopening of a small residual fistula. Posttreatment MR angiography demonstrated transient reduction of flow in the nidus in two patients with intramedullary malformations treated with embolization. Permanent disappearance of flow in the perimedullary vessel was seen after endovascular treatment in two patients with perimedullary fistula. CONCLUSION: MR angiography is more sensitive than MR imaging in depicting residual or recurrent flow in peri- or intramedullary vessels, which indicates patency of the vascular malformation.     

Rapid MR imaging of a vascular challenge to focal ischemia in cat brain

Deoxygenated blood was effectively used as a magnetic resonance (MR) susceptibility contrast agent to distinguish perfused and nonperfused (ischemic) regions in a focal ischemia model in cat brain at 2 T. Modulation of cerebral blood oxygenation levels in response to apnea was followed in real time with T2*-weighted (gradient-recalled) echo-planar MR imaging. Signal loss in the T2*-weighted images occurred only in perfused tissues as blood became globally deoxygenated. These data complemented information from diffusion-weighted and contrast agent bolus–-tracking images. In addition, observation of the signal recovery behavior on reventilation in both normal and ischemic brain offered potentially useful information about the state of the cerebral autoregulatory mechanism.     

New developments in MRA: time-resolved MRA

For many clinical questions, less invasive angiography methods have at least in part already replaced digital subtraction angiography (DSA) as a routine diagnostic procedure. However, temporal resolution achievable with DSA is still indispensable in some patients. Recent advances in MR hardware performance and imaging techniques permit sub-second frame rate MR angiographies to be performed using a rapidly repeated fast T1 weighted gradient echo sequence during administration of a contrast bolus, and subsequent complex subtraction in k-space to emphasise the difference in phase between stationary tissue and contrast-enhanced blood. This technique allows two-dimensional projection angiograms to be obtained at a temporal frame rate of three images per second and with a spatial in-plane resolution of about one square millimetre. This time-resolved information is important for (a) the detection and follow-up of arteriovenous malformations, including their arterial feeders, the size of the nidus and their venous drainage patterns, (b) the demonstration of dural arteriovenous fistulas, recognised as an early filling of a dural sinus during the early arterial phase, and (c) the characterization of the vascularisation of brain tumours. With regards to vascular malformations, the direction of venous drainage and therefore the most pressing clinical questions concerning the need for therapeutic intervention can be ascertained. This technique is the only MR imaging method able to provide dynamic information on the cerebral vasculature. It therefore constitutes a helpful adjunct to the imaging armentarium in many clinical situations.     

Cerebral blood volume in a rat model of ischemia by MR imaging at 4.7 T

Perturbation of the cerebral circulation by occlusion of the vertebral arteries and a carotid artery can be visualized by using MR imaging and the intravascular contrast agent Gd-DTPA complexed to albumin. This tracer consistently reduced the T1 relaxation time in the brain and blood. The difference between hemispheres was revealed by less T1 reduction in the occluded hemisphere and by an adjustment in the display contrast of images that revealed the territory of decreased perfusion. These results were confirmed by comparing them with cerebral blood flow using radioactive microspheres and the intravascular blood volume tracer 51Cr-EDTA. This method, combined with high-resolution MR imaging, can be applied to serial noninvasive studies of cerebral blood volume in ischemia and other conditions.     

Relationship between vascular enhancement, cerebral hemodynamics, and MR angiography in cases of acute stroke

BACKGROUND AND PURPOSE: The use of MR angiography and contrast-enhanced T1-weighted MR imaging in cases of acute cerebral ischemia may be helpful in the evaluation of middle cerebral artery (MCA) occlusion and leptomeningeal collaterals, respectively. The aim of our work was to investigate the relationship between MCA occlusion, T1-weighted vascular contrast enhancement, hemodynamic alterations, and tissue damage in cases of acute ischemic stroke. METHODS: We studied the MCA territory in 15 patients with acute ischemic stroke within 8 hr of symptom onset. The first MR imaging study (<8 hr after onset) comprised diffusion-weighted imaging, MR angiography, perfusion-weighted imaging, and contrast-enhanced T1-weighted MR imaging sequences. Follow-up MR imaging, performed 1 week later, consisted of MR angiography and T2-weighted fluid-attenuated inversion recovery MR imaging. RESULTS: Early MR angiography showed MCA stem occlusion in nine of 15 patients. Patients with MCA occlusion had significantly larger areas of abnormality on early diffusion-weighted images, significantly larger areas of altered hemodynamics, larger final lesion volumes, and poorer clinical outcome. Among the nine patients with MCA stem occlusion, vascular enhancement was marked in seven and absent in two who had complete MCA infarcts and poor clinical outcome. Among patients with MCA patency, vascular enhancement was marked in only one, mild in four, and absent in one. Patients with marked vascular enhancement had significantly larger regions of altered hemodynamics and significantly higher asymmetries in both regional cerebral blood volume and mean transit time because of increased values in the affected hemisphere. CONCLUSION: Among patients with stroke with MCA occlusion, marked vascular enhancement and increased blood volume indicate efficient leptomeningeal collaterals and compensatory hemodynamic mechanisms.     

Angiographic abnormalities in progressive multifocal leukoencephalopathy: an explanation based on neuropathologic findings

BACKGROUND AND PURPOSE: Progressive multifocal leukoencephalopathy (PML) is typically occult at angiography and fails to enhance on MR images. After observing angiographic abnormalities characterized by arteriovenous shunting and pathologic parenchymal blush in patients with AIDS-related PML, often in the absence of contrast enhancement on MR images, we hypothesized that there might be distinct changes in the cerebral microvasculature that account for the reduction in vascular transit time (arteriovenous shunting) in the absence of blood-brain barrier dysfunction. METHODS: The imaging studies and neuropathologic specimens of six patients with biopsy-proved PML were reviewed retrospectively. In all patients contrast-enhanced MR imaging and CT, followed by cerebral angiography, were performed before stereotactically directed biopsy. The angiograms were evaluated for the presence of vascular displacement, pathologic parenchymal blush, arteriovenous shunting, and neovascularity. The CT and MR studies were reviewed for the presence of enhancement of the PML lesions. Biopsy specimens were examined for the presence of necrosis, perivascular inflammation, and neovascularity. RESULTS: All patients had oligodendrocytic intranuclear inclusions diagnostic of PML, together with perivascular inflammation and neovascularity to a varying extent; no other neuropathologic processes were identified. Angiographic abnormalities, characterized by a pathologic parenchymal blush and arteriovenous shunting, were identified in four of the six patients. In only one of these cases, however, was abnormal enhancement identified on cross-sectional imaging studies (MR and CT), and this patient had florid perivascular inflammatory infiltrates histologically. CONCLUSION: The pathologic parenchymal blush and arteriovenous shunting seen angiographically in some patients with PML reflect small-vessel proliferation and perivascular inflammatory changes incited by the presence of the JC virus in infected oligodendrocytes.     

3.0T磁共振高分辨磁敏感成像在血管畸形中的应用价值

目的:探讨高分辨磁敏感成像(HR-SWI)在脑部血管畸形中的应用价值。方法:对45例脑血管畸形的患者行常规MR序列和HRSWI扫描。其中8例同时行MRA检查,31例行增强检查。结果:45例患者均在HR-SWI上清晰显示畸形血管,其中海绵状血管瘤26例,动静脉畸形5例,静脉瘤11例,Sturge-Weber综合征3例。结论:SWI显示血管畸形更清晰,明显优于常规序列,可为临床提供更多有用的信息并有助于脑血管畸形的确诊。     

高压注射器在磁共振灌注及血管成像中的应用

目的：通过压力注射器在磁共振灌注及血管成像中的应用体会,探讨其在磁共振检查中的临床意义,方法：30例脑肿瘤患者脑灌注成像,28例血管病变患者常规增强扫描及5例冠心病患者心肌灌注成像,使用Medrad Spectris MR injector注射器经上肢大静脉进行快速大剂量对比剂团注。造影前根据病变或血管的大小,首先预设置流速,流量及注射时间,对选定某一病变区域用动脉程序行短时扫描或延迟扫描,作为对照,另12例脑肿瘤患者脑灌注成像采用手推方式注射,并对脑灌注曲线做对比分析,结果：42例脑肿瘤中30例经手术病理确诊,6例外院手术,6例本院活检穿刺,28例血管病变经IADSA证实,所有检查均获成功。脑血流灌注曲线压力注射器组优于手推组,28例血管病变血管造影像及5例心肌灌注图像均达诊断标准。结论：压力注射器可保持稳定速度,确保对比剂浓度以完成准确灌注,江可根据灌注成像及血管造影成像程序调节速度和时间,更为精确地进行上述检查。     

Cerebral hemodynamics on MR perfusion images before and after bypass surgery in patients with giant intracranial aneurysms.

BACKGROUND AND PURPOSE: Preoperative assessment of the anatomy and dynamics of cerebral circulation for patients with giant intracranial aneurysm can improve both outcome prediction and therapeutic approach. The aim of our study was to use perfusion MR imaging to evaluate cerebral hemodynamics in such patients before and after extraintracranial high-flow bypass surgery. METHODS: Five patients with a giant aneurysm of the intracranial internal carotid artery underwent MR studies before, 1 week after, and 1 month after high-flow bypass surgery. We performed MR and digital subtraction angiography, and conventional and functional MR sequences (diffusion and perfusion). Surgery consisted of middle cerebral artery (MCA)-internal carotid artery bypass with saphenous vein grafts (n = 4) or MCA-external carotid artery bypass (n = 1). RESULTS: In four patients, MR perfusion study showed impaired hemodynamics in the vascular territory supplied by the MCA of the aneurysm side, characterized by significantly reduced mean cerebral blood flow (CBF), whereas mean transit time (MTT) and regional cerebral blood volume (rCBV) were either preserved, reduced, or increased. After surgery, angiography showed good canalization of the bypass graft. MR perfusion data obtained after surgery showed improved cerebral hemodynamics in all cases, with a return of CBF index (CBFi), MTT, and rCBV to nearly normal values. CONCLUSION: Increased MTT with increased or preserved rCBV can be interpreted as a compensatory vasodilatory response to reduced perfusion pressure, presumably from compression and disturbed flow in the giant aneurysmal sac. When maximal vasodilation has occurred, however, the brain can no longer compensate for diminished perfusion by vasodilation, and rCBV and CBFi diminish. Bypass surgery improves hemodynamics, increasing perfusion pressure and, thus, CBFi. Perfusion MR imaging can be used to evaluate cerebral hemodynamics in patients with intracranial giant aneurysm.     

Recent advances in MR imaging/spectroscopy of cerebral ischemia

Recent advances in high-resolution MR imaging and multinuclear spectroscopy have stimulated studies of the functional relationships between tissue hypoperfusion, cellular energy depletion, and brain edema associated with cerebral ischemia. The very slow (microns/sec) random translational motion of water protons in various brain tissues and intracranial fluid compartments can now be assessed with MR diffusion imaging. More slowly diffusing protons in ischemic tissues can be differentiated from normal parenchyma, CSF, and flowing blood, enabling the detection and localization of ischemic regions within minutes of the onset of stroke. Perfusion imaging "snapshots," obtained in as little as 25 msec with echoplanar MR methods, permit the evaluation of tissue washin/washout kinetics of contrast agents in the microvasculature, and thus the quantification of brain perfusion on a regional basis. Also, delineation of major intra- and extracranial arterial and venous structures with MR angiography, acquired with two- or three-dimensional Fourier transformation techniques, has enabled accurate noninvasive assessments of vascular occlusive disease. Finally, improvements in MR spectroscopic techniques have facilitated investigations of metabolic regulation and bioenergetics in experimental animal models of cerebral ischemia, as well as in stroke patients. Combined MR imaging and spectroscopy will likely play an important role in differentiating reversibly from irreversibly ischemic brain tissues and in the investigation of various neuroprotective pharmaceuticals.     

Gadolinium enhanced MR imaging of vascular stents

The feasibility of obtaining in-plane magnetic resonance (MR) vascular images in the presence of a vascular stent and the value of infusing an MR contrast agent during imaging was assessed. Coronal and sagittal MR imaging at 1.5 T was performed on six dogs with tantalum aortic stents using single-section gradient echo (GRE) imaging and MR angiography techniques before and during intravenous infusion of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In-plane gradient echo (GRE) imaging and MR angiography clearly showed flow within the stented vessel as increased signal, with a minimum amount of stent-related artifact. Infusion of Gd-DTPA significantly increased the signal of flowing blood and allowed for better delineation of the stented aortic lumina. Our results demonstrate that in-plane GRE imaging and MR angiography can potentially be used as noninvasive methods for evaluating vascular patency in the presence of MR-compatible endovascular devices. In addition, Gd-DTPA infusion during MR vascular imaging clearly enhances the definition of flowing blood in the lumina of stented vessels.     

Cerebral vasculitis: imaging signs revisited

Inflammatory stenoses of cerebral blood vessels, although rare in general, are an important cause of cerebral ischemia in younger patients. The diagnosis is often difficult. The first step in the diagnostic process is the identification of brain lesions consistent with cerebral vasculitis. Brain lesions are frequently found in this patient group, especially if modern imaging tools such as diffusion and perfusion-weighted imaging are employed. Although no specific pattern for this entity exists, multiple infarcts of various ages in more than one vascular territory should raise this suspicion. The next step in the imaging of patients with suspected vasculitis is the demonstration of the underlying vascular pathology. MR angiography is the mainstay of investigating patients for intracranial vascular stenoses. However, at 1.5 T it is only diagnostic for stenoses of large brain arteries. Hence, conventional angiography is still required to investigate stenoses of medium and small-sized brain arteries. Recent work suggests that MRI can directly demonstrate mural thickening and contrast enhancement in basal brain arteries, rendering biopsy obsolete in this patient group. A classification for cerebral vasculitis is proposed according to the size of the affected brain vessels, analogous to the pertinent nomenclature of primary systemic vasculitis.     

Intraindividual comparison of gadobenate dimeglumine and gadobutrol for cerebral magnetic resonance perfusion imaging at 1.5 T

RATIONALE AND OBJECTIVE: The objective of this study was to compare 0.1 and 0.2 mmol/kg body weight (bw) doses gadobenate dimeglumine (Gd-BOPTA; MultiHance) and gadobutrol (Gd-BT-DO3A; Gadovist) for cerebral perfusion magnetic resonance (MR) imaging at 1.5 T. METHODS: Twelve healthy male volunteers enrolled into a randomized intraindividual comparative study underwent 4 perfusion MR imaging examinations with 0.1 and 0.2 mmol/kg bw doses of each contrast agent. The imaging parameters, slice positioning, and contrast agent application were highly standardized. Quantitative determinations based on signal intensity/time (SI/T) curves at regions of interest (ROI) on the gray and white matter were made of the regional cerebral blood volume and flow (rCBV and rCBF, respectively), the percentage signal drop, and the full width half maximum (FWHM) of the SI/T curve. Qualitative evaluation of the quality of the rCBV and rCBF maps was assessed by an independent offsite blinded reader. RESULTS: A single dose of both agents was sufficient to achieve high-quality, diagnostically valid perfusion maps at 1.5 T, and no significant benefit for one agent over the other was noted for quantitative or qualitative determinations. The susceptibility effect, described by percentage of signal loss (gadobutrol: 29.4% vs gadobenate dimeglumine: 28.3%) and the FWHM (gadobutrol: 6.4 seconds vs gadobenate dimeglumine: 7.0 seconds) were similar for 0.1 mmol/kg bw doses of the 2 agents. Double doses of the 2 agents produced better overall image quality but no clinical benefit over the single-dose examinations. CONCLUSION: Both the 1 molar MR contrast agent gadobutrol and the weak protein-interacting agent gadobenate dimeglumine permit the acquisition of high-quality perfusion maps at doses of 0.1 mmol/kg bw. The susceptibility effect is comparable for both agents and stronger than for conventional MR contrast agents.     

Correlative assessment of hemodynamic parameters obtained with T2*-weighted perfusion MR imaging and SPECT in symptomatic carotid artery occlusion

BACKGROUND AND PURPOSE: Perfusion MR imaging and single-photon emission CT (SPECT) are commonly used to evaluate hemodynamic status in patients with symptomatic occlusive cerebrovascular disease. These techniques rely on different underlying physiological mechanisms, and the data may not correspond. We studied the relationship between hemodynamic parameters obtained with these two methods. METHODS: We performed perfusion MR imaging and SPECT in 10 patients with symptomatic unilateral internal carotid artery occlusion. Relative cerebral blood volume (rCBV) and uncorrected mean transit time (uMTT) were obtained with dynamic contrast-enhanced T2*-weighted MR imaging. Relative cerebral blood flow (rCBF) and vascular reserve capacity were measured with 99mTc-HMPAO SPECT; vascular reserve capacity was calculated by the difference in CBF before and after acetazolamide challenge. Ratios of these hemodynamic parameters between the affected and contralateral vascular territories were calculated and compared. RESULTS: Normal-to-increased CBV, prolonged uMTT, decreased CBF, and normal-to-diminished vascular reserve capacity were observed in the affected vascular territories. Reduction of vascular reserve capacity corresponded well with uMTT but not with CBF and CBV. CBF, CBV, and uMTT did not correspond to one another. CONCLUSION: uMTT is more sensitive than the other parameters in estimating vascular reserve capacity. The relationship between parameters obtained with perfusion MR imaging and SPECT should be considered in assessing the hemodynamic status of patients with symptomatic occlusive cerebrovascular disease.     

MR angiography of spinal vascular malformations.

PURPOSETo determine the potential and limitations of MR angiography in the evaluation of spinal vascular malformations.METHODSEleven consecutive patients with spinal vascular malformations proved with spinal selective arteriography underwent two-dimensional phase-contrast MR angiography.RESULTSAbnormal vessels within the spinal canal were identified with MR angiography in 10 patients. In 1 patient with a dural arteriovenous fistula no definite vascular abnormality was seen with MR angiography. Correlation of MR angiography with spinal selective arteriography showed that the former allowed identification of the arterial feeder in 3 patients with intramedullary arteriovenous malformations and 2 with perimedullary arteriovenous fistula, whereas the source of intradural draining vein was seen in only 2 of 6 patients with dural arteriovenous fistula.CONCLUSIONMR angiography is a promising complementary tool to MR imaging for detection and characterization of spinal vascular malformations.     

Arterialization of cerebral veins on dynamic MDCT angiography: a possible sign of a dural arteriovenous fistula

OBJECTIVE: MDCT angiography allows fast imaging of the cerebral vessels, and its potential as a noninvasive technique to detect vascular abnormalities on the basis of morphologic changes is well established. We analyzed vascular enhancement patterns of cerebral venous structures on MDCT angiography, which enabled us to diagnose dural arteriovenous fistula. CONCLUSION: MDCT angiography performed during an early arterial phase showed asymmetrically higher contrast intensity in the transverse or sigmoid sinus, or both, in five patients. In all patients, digital subtraction angiography confirmed the presence of a dural arteriovenous fistula on the side on which the higher contrast intensity appeared. Radiologists should actively look for this sign in the imaging workup of patients presenting with nonspecific symptoms that might be related to a dural arteriovenous fistula.