High-resolution turbo magnetic resonance angiography for diagnosis of Moyamoya disease

A Vessel Wall MRI Investigation in Patients With Moyamoya or Quasi-Moyamoya Disease: Diagnosis, Features, and Outcomes

BACKGROUND AND PURPOSE

None of the previous studies have investigated the pathologic authenticity of affected arteries in moyamoya disease (MMD) and Quasi-MMD diagnosed by angiography. This study aimed to confirm the angiographic diagnosis of moyamoya as well as investigate the pathologic mechanisms in angiographically proven MMD and Quasi-MMD using high-resolution magnetic resonance imaging (MRI) in a large sample.

METHODS

We prospectively studied 116 patients who had angiographically proven MMD and Quasi-MMD. Each affected internal carotid artery, and middle cerebral artery was independently evaluated. In addition, clinical features and postoperative outcomes were compared between hemispheres with MMD and moyamoya syndrome (MMS).

RESULTS

Among 116 patients analyzed, 88 and 22 patients had angiographically proven MMD and Quasi-MMD, respectively. high-resolution magnetic resonance imaging confirmed bilateral MMD in 73 (83.0%) patients, 1 hemisphere with MMD and the other with intracranial atherosclerotic disease (ICAD) in 10 (11.4%) patients, and bilateral hemispheres with different vasculopathies in 5 (5.7%) patients. Detailed analysis of 204 affected hemispheres showed that several combinations of different vasculopathies were observed in the internal carotid artery and middle cerebral artery of the same hemisphere, such as ICAD-ICAD, ICAD-MMD, dissection-ICAD, and dissection-MMD. Hemispheres were assigned to MMD and MMS groups according to their vasculopathies. Transient ischemic attack occurred more frequently in hemispheres with MMD (48.1% versus 21.1%, P =0.024), whereas symptomatic ischemia was more common in hemispheres with MMS (57.9% versus 24.9%, P =0.002). However, postoperative cerebral infarction, symptom improvement and neo-formative collaterals showed no significant difference between hemispheres with MMD and MMS ( P >0.05).

CONCLUSIONS

Patients with angiographically proven MMD or Quasi-MMD needed more accurate evaluation combined with high-resolution magnetic resonance imaging. Highly selected patients with MMS might also obtain benefits from surgical revascularization.

Is STA really a low‐flow graft? A quantitative ultrasonographic study of the flow of STA for cerebral revascularization in MMD patients

OBJECTIVE

Direct revascularization remains an important tool in the treatment of patients with Moyamoya disease (MMD). The superficial temporal artery (STA) is the most commonly used donor vessel for direct bypass, and an STA graft has traditionally been considered a low-flow graft for flow augmentation. This study aimed to quantitatively evaluate the blood flow of the STA after direct revascularization.

METHODS

All direct revascularization procedures performed between 2018 and 2021 by one experienced neurosurgeon were screened. Quantitative ultrasound was used to measure the flow data of the patient's bilateral parietal branch of the STA(STA-PB), the bilateral frontal branch of the STA(STA-FB), and the left radial artery. Data on the patients' basic information, Suzuki grade, Matsushima type, anastomosis type, and blood biochemical parameters were collected and analyzed using univariate and multivariate models. An MBC Scale scoring system was proposed to evaluate the recipient artery network of the middle cerebral artery (MCA) tree. The relationship between MBC Scale score and STA graft flow was statistically analyzed.

RESULTS

In total, 81 patients (43 males and 38 females) successfully underwent STA-MCA bypass and were included in this study. The mean flow rates in the STA-PB graft on 1 day preoperatively, 1 day postoperatively, 7 days postoperatively, and >6 months postoperatively (long-term) were 10.81, 116.74, 118.44, and 56.20 mL/min respectively. Intraoperative graft patency was confirmed in all patients. Comparing the preoperative and all postoperative time points, the STA-PB flow rates were statistically significant (p < 0.001). The MCA-C score was significantly associated with postoperative flow rate on day 1 (p = 0.007).

CONCLUSION

The STA is a useful donor artery for direct revascularization inpatients with MMD and can provide sufficient blood supply to the ischemic cerebral territory.

Recognizing Moyamoya Disease in a Soldier With Recurrent Cerebrovascular Symptoms

Moyamoya is a rare and progressive cerebrovascular disease involving collateral small vessel formation associated with intracranial artery narrowing. It is a disease that frequently presents with stroke and transient ischemic attacks and has potential to affect our active duty service members and their families with its bimodal age of onset of 10 and 40. This case report describes a soldier with moyamoya whose diagnosis was unrecognized for over a year after seeing multiple medical providers regarding his symptoms. The goal of this case report is to raise vigilance for this disease as it can cause significant morbidity and mortality with mental decline, recurrent strokes, and death without timely surgery.

[Modern trends in diagnosis and surgical treatment of moyamoya disease]

This review is devoted to moyamoya disease. It is a rare chronic steno-occlusive cerebrovascular disease. However, moyamoya disease is increasingly diagnosed by neurosurgeons in our country. Unlike atherosclerotic lesions of cerebral arteries, pathogenesis and course of this disease are much more complex and variable. Therefore, specialists often have certain difficulties in diagnosis, management and treatment of these patients. To date, a large number of surgical interventions have been proposed for the treatment of moyamoya disease. Revascularization approaches include direct procedures (extra-intracranial microanastomoses), indirect methods (synangioses) and combined revascularization. The purpose of the review is to systematize current literature data on the pathogenesis, diagnosis, clinical patterns and surgical treatment of patients with moyamoya disease. results Outcomes of surgical revascularization and the role of its various components in combined approach are under particular attention.

High-resolution Magnetic Resonance Imaging of Moyamoya Disease

Objective:

To introduce the imaging characteristics of moyamoya disease (MMD) using high-resolution magnetic resonance imaging (HR-MRI) and to discuss the role of HR-MRI in differentiating MMD from other intracranial artery diseases, especially intracranial atherosclerotic disease (ICAD).

Data Sources:

This review was based on the data in articles published between 2005 and 2015, which were obtained from PubMed. The keywords included HR-MRI, MMD, ICAD, and intracranial artery diseases.

Study Selection:

Articles related to HR-MRI for MMD or other intracranial artery diseases were selected for review.

Results:

There are differences between the characteristic patterns of HR-MRI in MMD and ICAD. MMD is associated with inward remodeling, smaller outer diameters, concentric occlusive lesions and homogeneous signal intensity, while ICAD is more likely to be associated with outward remodeling, normal outer diameters, eccentric occlusive lesions, and heterogeneous signal intensity. Other intracranial artery diseases, such as dissection and vasculitis, also have distinctive characteristics in HR-MRI. HR-MRI may become a useful tool for the differential diagnosis of MMD in the future.

Conclusions:

HR-MRI of MMD provides a more in-depth understanding of MMD, and it is helpful in evaluating pathological changes in the vessel wall and in differentiating MMD from other intracranial artery steno-occlusive diseases, particularly ICAD.

Single-photon emission tomography

Single-photon emission computed tomography (SPECT) is a functional nuclear imaging technique that allows visualization and quantification of different in vivo physiologic and pathologic features of brain neurobiology. It has been used for many years in diagnosis of several neurologic and psychiatric disorders. In this chapter, we discuss the current state-of-the-art of SPECT imaging of brain perfusion and dopamine transporter (DAT) imaging. Brain perfusion SPECT imaging plays an important role in the localization of the seizure onset zone in patients with refractory epilepsy. In cerebrovascular disease, it can be useful in determining the cerebrovascular reserve. After traumatic brain injury, SPECT has shown perfusion abnormalities despite normal morphology. In the context of organ donation, the diagnosis of brain death can be made with high accuracy. In neurodegeneration, while amyloid or (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) are the nuclear diagnostic tools of preference for early and differential diagnosis of dementia, perfusion SPECT imaging can be useful, albeit with slightly lower accuracy. SPECT imaging of the dopamine transporter system is widely available in Europe and Asia, but since recently also in the USA, and has been accepted as an important diagnostic tool in the early and differential diagnosis of parkinsonism in patients with unclear clinical features. The combination of perfusion SPECT (or FDG-PET) and DAT imaging provides differential diagnosis between idiopathic Parkinson's disease, Parkinson-plus syndromes, dementia with Lewy bodies, and essential tremor.

Imaging of cerebral ischemia: from acute stroke to chronic disorders

Cerebral ischemia manifests widely in patient symptoms. Along with the clinical examination, imaging serves as a powerful tool throughout the course of ischemia-from acute onset to evolution. A thorough understanding of imaging modalities, their strengths and their limitations, is essential for capitalizing on the benefit of this complementary source of information for understanding the mechanism of disease, making therapeutic decisions, and monitoring patient response over time.

Clinical features of familial juvenile cases of moyamoya disease: analysis of patients treated in a single institute over a 28-year period

OBJECT

The authors compared the clinical features between familial and sporadic cases of moyamoya disease (MMD) by retrospectively analyzing data on patients with MMD registered in the database of Tokyo Medical and Dental University over a period of 28 years.

METHODS

In total, 383 patients with hospital records at Tokyo Medical and Dental University from 1980 to 2007 were registered into the database. The data on all of these patients were retrospectively reviewed to clarify the occurrence of familial cases. Clinical features of child or adolescent patients (< 20 years of age) with MMD were compared between familial and sporadic cases in a subgroup of patients who were registered after 1995, initially diagnosed using MR angiography, and assessed using an intelligence scale.

RESULTS

Familial occurrence was observed in 59 patients (15.4%) in 40 pedigrees. The clinical features of juvenile patients were analyzed in 124 patients, 22 (17.7%) of whom had familial histories. In comparison with the sporadic cases, patients with familial histories were significantly younger at onset (4.7 vs 6.6 years old), had significantly more cortical infarction (59.1% vs 25.5%), and had significantly more stenoocclusive lesions in the posterior cerebral artery (45.4% vs 24.5%). The rate of patients with intellectual disturbance (intelligence quotient < 75) was significantly larger in the familial cases (47.4%) than in the sporadic cases (17.8%).

CONCLUSIONS

This survey of the clinical features of familial MMD suggests that patients with familial MMD had a more serious clinical course in childhood than the sporadic MMD cases.

Moyamoya disease: a review of the literature

Moyamoya disease is a rare progressive cerebrovascular disorder that can be congenital or acquired and involves progressive stenosis and occlusion of cerebral arteries. The brain through compensatory angeogenesis then attempts to compensate for ischemia by producing a local network of tiny blood vessels, which appear cloud-like on angiograms. Consistent with multifocal or diffuse areas of ischemia, people with moyamoya often have multiple areas of cognitive impairment. A thorough literature review of the neuropsychological profile in individuals diagnosed with moyamoya disease is provided. Medical and neuropsychological/neurobehavioral data of a middle-aged woman with moyamoya disease is also described. The patient (MA) suffered an embolic shower with insult to both cerebral hemispheres. Neuropsychological results suggested a multifocal decline, with both cortical and subcortical involvement. Data were consistent with impairments in attention, concentration, executive skills, processing speed, and memory encoding and retrieval, with relatively spared aspects of memory and language skills. This case study supports the literature and provides an additional example of the neuropsychological profile and deficit pattern of an individual with moyamoya following an embolic stroke shower.

Assessment of moyamoya disease using multidetector row computed tomography

The recent introduction of multidetector row computed tomography (MDCT) scanners has enabled high-resolution 3-dimensional reconstruction. The purpose of this study was to establish a method to evaluate moyamoya disease using computed tomography angiography (CTA), specifically MDCT. Twenty-four patients (48 sides total) with moyamoya disease diagnosed by magnetic resonance angiography (MRA) were evaluated by means of CTA using MDCT by 3 independent observers, and the resulting 144 sides were analyzed. CTA and MRA were compared in terms of the steno-occlusive changes exhibited in each vessel. CTA and MRA scores were assigned on the basis of the severity of occlusive changes in the internal carotid artery, middle cerebral artery, anterior cerebral artery, and posterior cerebral artery. CTA scores were significantly correlated with MRA scores (P < .0001), and the 2 scores were in complete agreement in 57 sides (39.6%). The mean CTA score was significantly lower than the mean MRA score (P < .0001). Compared with CTA, MRA overestimated occlusion in 115 of the 576 vessels assessed. The mean MRA score was significantly higher in the overestimation group than in the good correlation group (P < .0001). CTA had a significantly higher rate of detection of moyamoya-affected vessels (P = .0001). Our data indicate that CTA using MDCT is a more reliable technique than MRA for diagnosing moyamoya disease. The ability to perform CTA quickly is a significant benefit for patients with moyamoya disease, particularly in pediatric and emergency cases.

Natural history and progression factors of unilateral moyamoya disease in pediatric patients

PURPOSE

Thirty-four pediatric age patients with unilateral moyamoya disease (MMD) were reviewed to analyze the natural history and the predictive factors for progression to bilateral MMD.

METHODS

Forty out of 259 MMD patients cared for between January 2000 and June 2008 in the Severance Hospital had unilateral lesion. These patients were followed for a mean of 32.3 months for their symptoms and imaging studies. Thirty-four out of 40 patients were included in this study. Magnetic resonance angiography (MRA) and magnetic resonance perfusion (MR perfusion) images were taken for all patients for initial diagnosis and repeated at 6 months from the initial diagnosis and then at yearly basis. Clinical manifestations, the results of imaging studies, outcome of the indirect revascularization procedure, and the progression of the lesion were reviewed in this study.

RESULTS

Of these 34 patients, contralateral progression was identified in 20 patients (58.8%). Fourteen (70%) out of the 20 patients presented with anterior cerebral artery abnormalities at diagnosis progressed to bilateral disease as well as did 5 (83%) out of 6 patients with middle cerebral artery lesions at the initial examination. Among the 34 patients, six exhibited familial history of MMD and all of them progressed to bilateral disease (100%, p < 0.005).

CONCLUSION

Careful and long-term follow-up would be essential to evaluate the hemodynamic status and progression to bilateral disease in unilateral MMD patients to make prompt decision for a surgical revascularization.

Focal time-to-peak changes on perfusion MRI in children with Moyamoya disease: correlation with conventional angiography

BACKGROUND

Moyamoya disease is a chronic progressive steno-occlusion of the distal internal carotid arteries with unknown etiology. As the classical presentation of childhood Moyamoya disease is ischemic stroke, cerebral hemodynamic evaluation is important for patient selection for surgery to prevent recurrent ischemic attacks. Perfusion MR imaging has been applied to evaluate cerebral hemodynamics.

PURPOSE

To correlate the 'basal time-to-peak preservation sign', 'auto-synangiosis sign', and 'posterior involvement sign' on time-to-peak map of perfusion MRI with catheter angiography.

MATERIAL AND METHODS

Thirty-four children (6.91 ± 3.08 years) with Moyamoya disease who underwent both perfusion-weighted MRI and catheter angiography were enrolled in this study. Given catheter angiography as a reference standard, basal time-to-peak preservation sign, auto-synangiosis sign, and posterior involvement sign were evaluated on time-to-peak maps.

RESULTS

The basal time-to-peak preservation sign was accurate for the diagnosis of childhood Moyamoya disease; both sensitivity and specificity were 100%. The auto-synangiosis sign showed lower sensitivity (65%), however, with an acceptable specificity (98%). The posterior involvement sign showed lower sensitivity (61%) but had an acceptable specificity (96%).

CONCLUSION

The basal time-to-peak preservation sign may be a universal finding in childhood Moyamoya disease. The auto-synangiosis and posterior involvement sign may be useful in determining transdural collateral status and posterior circulation involvement in childhood Moyamoya disease.

About a snail, a toad, and rodents: animal models for adaptation research

Neural adaptation mechanisms have many similarities throughout the animal kingdom, enabling to study fundamentals of human adaptation in selected animal models with experimental approaches that are impossible to apply in man. This will be illustrated by reviewing research on three of such animal models, viz. (1) the egg-laying behavior of a snail, Lymnaea stagnalis: how one neuron type controls behavior, (2) adaptation to the ambient light condition by a toad, Xenopus laevis: how a neuroendocrine cell integrates complex external and neural inputs, and (3) stress, feeding, and depression in rodents: how a neuronal network co-ordinates different but related complex behaviors. Special attention is being paid to the actions of neurochemical messengers, such as neuropeptide Y, urocortin 1, and brain-derived neurotrophic factor. While awaiting new technological developments to study the living human brain at the cellular and molecular levels, continuing progress in the insight in the functioning of human adaptation mechanisms may be expected from neuroendocrine research using invertebrate and vertebrate animal models.

The contribution of imaging in diagnosis, preoperative assessment, and follow-up of moyamoya disease

The aim of this review was to evaluate the imaging tools used in diagnosis and perioperative assessment of moyamoya disease, with particular attention to the last decade.

2D cine phase-contrast MRI for volume flow evaluation of the brain-supplying circulation in moyamoya disease

OBJECTIVE

The purpose of this study was to evaluate and quantify hemodynamic compromise in patients with moyamoya disease by measuring blood volume flow in the brain-supplying arteries.

SUBJECTS AND METHODS

Thirty-five patients with angiographically proven moyamoya disease (31 women, 4 men; mean age, 39.4 +/- 12.2 years; range, 15-58 years; adult moyamoya disease) and 15 age-matched healthy controls were examined prospectively with 2D cine phase-contrast MRI. Blood volume flow was measured in both common carotid arteries (CCAs), both internal carotid arteries (ICAs), and the basilar artery. The diagnosis of moyamoya disease was based on results of selective intraarterial digital subtraction angiography.

RESULTS

Blood volume flow of the brain-supplying arteries in age-matched controls was 435.6 +/- 47.9 mL/min for the CCA, 254.1 +/- 25.3 mL/min for the ICA, and 173.3 +/- 13.2 mL/min for the basilar artery. Patients with bilateral moyamoya disease had decreased mean blood flow in the CCA (309.4 +/- 89.9 mL/min) and ICA (117.9 +/- 64.0 mL/min) and increased blood volume flow in the basilar artery (433.7 +/- 165.9 mL/min).

CONCLUSION

Moyamoya disease causes a significant decrease in carotid artery circulation, particularly ICA blood volume flow, with a compensatory increase in blood flow in the basilar artery to nearly 2.5 times normal basilar artery blood flow. 2D cine phase-contrast MRI with measurement of blood volume flow in the brain-supplying arteries is useful in the initial evaluation of moyamoya disease and in continuing assessment of hemodynamics in patients with this disease.

Magnetic resonance angiography evaluation of external carotid artery tributaries in moyamoya disease

BACKGROUND AND PURPOSE

High-resolution magnetic resonance (MR) image has been introduced to diagnose and follow-up moyamoya disease and visualized moyamoya vessels and internal carotid artery stenosis. This study was performed to assess the utility of MR angiography (MRA) for the evaluation of anastomotic channels through the external carotid artery (ECA) in moyamoya disease patients.

METHODS

Twenty patients with moyamoya disease were reviewed. The cortical anastomosis and superficial temporal artery (STA), middle meningeal artery, and deep temporal artery by MRA were evaluated and were compared with those by digital subtraction angiography if obtained. Fifteen patients (24 hemispheres) underwent bypass surgery, including encephaloduroarteriosynangiosis in 14 hemispheres and STA-middle cerebral artery anastomosis with encephalomyosinangiosis in 10 hemispheres. Five patients did not undergo any surgery.

RESULTS

MRA could show these vessels and the patency of anastomosis formed by the surgery and also showed naturally formed anastomosis and ECA tributaries in the patients who did not undergo any surgery.

CONCLUSION

MRA provides useful information for follow-up evaluation on the development of the ECA system in moyamoya disease.

Novel magnetic resonance angiography stage grading for moyamoya disease

BACKGROUND

Magnetic resonance angiography (MRA) has been acknowledged as a noninvasive diagnostic modality for moyamoya disease. However, in terms of staging of moyamoya disease, conventional angiography is still the gold standard. Therefore, the purpose of this study was to establish MRA grades for moyamoya disease as an alternative to conventional angiography.

METHODS

Twenty-two patients (44 sides) with moyamoya disease diagnosed by conventional angiography were evaluated by MRA during the past 5 years. MRA scores were assigned based on the severity of occlusive changes of the internal carotid artery, the horizontal portion of the middle cerebral artery, the anterior and the posterior cerebral arteries and the signals of the distal branches of these arteries. Total points ranged from 0 (normal) to 10 (most severe).

RESULTS

MRA scores (0-10) were significantly consistent with the conventional angiographic staging. Four grades based on this novel MRA scores correlated well with Suzuki's stages, with high sensitivity and specificity.

CONCLUSIONS

These novel MRA grades can be a reliable alternative to conventional staging. By employing these novel MRA grades, the use of conventional angiography can be avoided for the purpose of evaluation of the stages of moyamoya disease.

Zero-Filling Interpolation Processing Technique Can Efficiently Suppress Segmental Stenosis Artifact on Small Arteries of Anatomical Phantoms

The purpose of this study was to evaluate the zero-filling interpolation processing (ZIP) technique for contrast-enhanced MR angiography (CE-MRA). Phantoms of arteries were made with different lumen diameters. Gadolinium-enhanced three-dimensional MR angiography was performed on a GE 1.5T scanner. The parameters of FSPGR pulse sequence were: flip angle 30°, TR 6ms, TE 1.4ms, bandwidth 31.25 kHz, slice thickness 1.2 mm, matrix 256×256. The sequence parameters were kept constant for the studies, whereas four selections were chosen: 1) with ZIP1024 and ZIP×4 techniques; 2) only with ZIP1024 technique; 3) only with ZIP×4 technique; 4) without ZIP technique. For image quality evaluation, MR maximum intensity projection (MIP) images were created. Signal-to-noise ratio (SNR) was measured on MIP images. Vessel edge was determined using full width at half maximum (FWHM) for lumen diameter calculation and results were compared with the actual lumen diameter. The distinctness of the vessel edge and the artifacts on the phantoms were compared for all sequences. Three experienced radiologists made consensus evaluation. The FWHM results of lumen measurements for all the sequences with ZIP techniques were more accurate than that of the sequence without ZIP technique in all phantoms, no matter what the size of the artery. The vessel edge with ZIP1024 technique was more distinct. However, the highest average SNR was obtained with the sequence without ZIP technique. The segmental stenosis artifacts on small artery of phantoms were only efficiently suppressed with the ZIP×4 technique. ZIP technique is excellent for CE-MRA to obtain high quality MR angiography. It not only can improve the spatial resolution and the distinctness of the vessel edge on CE-MRA, but can also efficiently suppress segmental stenosis artifact on small arteries of phantoms.

Leptomeningeal high signal intensity (ivy sign) on fluid-attenuated inversion-recovery (FLAIR) MR images in moyamoya disease

PURPOSE

There are a few reports on leptomeningeal high signal intensity (LMHI: ivy sign) on fluid-attenuated inversion-recovery (FLAIR) images in moyamoya disease, but the feature of this finding has not been completely understood. The purpose of this study was to characterize LMHI on FLAIR images in moyamoya disease and to assess usefulness of this finding in the diagnosis of moyamoya disease in conventional MR imaging.

MATERIAL AND METHODS

MR imaging of 28 patients with moyamoya disease was retrospectively reviewed. The grade of LMHI on FLAIR images was classified as "absent," "minimal," "moderate" and "marked." Fifty-four hemispheres of 28 patients (2 patients had unilateral disease) were assessed for the frequency of visualization and distribution of LMHI. The correlations between LMHI on FLAIR images, moyamoya vessels on T1- and T2-weighted images and MR angiography findings were also analyzed.

RESULTS

Moderate and marked LMHI was seen in 31 out of 54 hemispheres (57%). LMHI was seen more prominently in the frontal and parietal lobes than in the temporal and occipital lobes. Although there was a tendency for LMHI on FLAIR images to be prominent in groups with moderate and marked moyamoya vessels on T1- and T2-weighted images, there was no significant correlation. More prominent LMHI was observed in the hemispheres in which cortical branches of the middle cerebral arteries were poorly visualized on MR angiography.

CONCLUSION

Leptomeningeal high signal intensity (ivy sign) on FLAIR images is predominantly seen in the frontal and parietal lobes. Because this sign can be seen in patients with unremarkable moyamoya vessels, LMHI is a useful sign in conventional MR imaging for the diagnosis of moyamoya disease.

Arterial strokes in children

Pediatric stroke has received special attention in the recent literature. It is now recognized as an important cause of mortality and morbidity in pediatric population. Varied and poorly specific symptomatology as well as overlapping risk factors makes the diagnosis of stroke in childhood challenging. Therapy remains controversial. The use of anticoagulation and thrombolysis in the management of acute stroke in children has not been systematically studied. In this article, we discuss the natural history, investigation, and treatment of pediatric arterial hemorrhagic and ischemic strokes.

CT angiography and MR angiography in the evaluation of extracranial carotid vascular disease

CTA and MRA techniques likely will continue to increase in use in the evaluation of the extracranial cerebrovascular system. The increasing reliance on noninvasive tests mirrors an overall concern with the risks and costs of more invasive examinations. Given the rapid development of the computer technology, data acquisition, and reconstruction algorithms in the past few years, it is apparent that CTA and MRA also will continue to improve.