Coronary artery magnetic resonance angiography

Coronary magnetic resonance angiography (coronary MRA) continues to advance rapidly from both a technical and clinical perspective. Coronary MRA has benefited directly from improvements in spatial resolution, contrast definition, and advances in motion correction, which have furthered its routine use in evaluating coronary artery bypass grafts and anomalous coronary arteries. Work in refining the techniques for more accurate identification of coronary artery disease (CAD) continues, with advances in navigator-gated and breath-hold motion correction techniques, novel k-space strategies (e.g., spiral and radial k-space filling), development and application of intravascular contrast agents, and imaging at higher field strengths. Ultimately, these developments may lead to the routine application of coronary MRA as a screening tool for CAD. This article reviews the development of coronary MRA, discusses the requirements and tools necessary for optimal visualization of the coronary arteries, and describes the application of coronary MRA to acquired and congenital CAD.     

Asymptomatic middle cerebral artery stenosis diagnosed by magnetic resonance angiography

We reviewed 1440 MRA studies to identify patients with middle cerebral artery stenosis (MCAS). We identified 99 cases, and after reviewing the clinical records, classified 28 as asymptomatic MCAS (AMCAS), a prevalence of 2%. Suspected stroke was the most frequent indication for MRA. Follow-up was available for 21, mean 46.7 months (range 2.4–75.6 months). One stroke occurred in the AMCAS territory (5%), other strokes in five patients (24%). There were five deaths in patients with MCAS; age >69 ( P =0.045) was the only associated risk factor. This study suggests that patients in whom MRA is performed and shows AMCAS may be at increased risk of strokes in any vascular distribution or of death.Presented in part as an abstract at the 27 ^th International Stroke Meeting, San Antonio, Texas, February 2002 and the 54 ^th American Academy of Neurology Meeting, Denver, Colorado, April, 2002     

Anomalous origin of the occipital artery diagnosed by magnetic resonance angiography

Introduction  

It is well known that the occipital artery (OA) can arise from the internal carotid artery (ICA) or vertebral artery (VA). However, the incidence of an anomalously originating OA has not been reported. We investigate its incidence and characteristic features on magnetic resonance angiography (MRA).     

Coronary magnetic resonance angiography

Coronary magnetic resonance angiography (MRA) is a powerful noninvasive technique with high soft-tissue contrast for the visualization of the coronary anatomy without X-ray exposure. Due to the small dimensions and tortuous nature of the coronary arteries, a high spatial resolution and sufficient volumetric coverage have to be obtained. However, this necessitates scanning times that are typically much longer than one cardiac cycle. By collecting image data during multiple RR intervals, one can successfully acquire coronary MR angiograms. However, constant cardiac contraction and relaxation, as well as respiratory motion, adversely affect image quality. Therefore, sophisticated motion-compensation strategies are needed. Furthermore, a high contrast between the coronary arteries and the surrounding tissue is mandatory. In the present article, challenges and solutions of coronary imaging are discussed, and results obtained in both healthy and diseased states are reviewed. This includes preliminary data obtained with state-of-the-art techniques such as steady-state free precession (SSFP), whole-heart imaging, intravascular contrast agents, coronary vessel wall imaging, and high-field imaging. Simultaneously, the utility of electron beam computed tomography (EBCT) and multidetector computed tomography (MDCT) for the visualization of the coronary arteries is discussed.     

Vertebral artery variations at the C1–2 level diagnosed by magnetic resonance angiography

Introduction  

The craniovertebral junction is clinically important. The vertebral artery (VA) in its several variations runs within this area. We report the prevalence of these VA variations on magnetic resonance angiography (MRA).     

Middle cerebral artery variations detected by magnetic resonance angiography

Middle cerebral artery (MCA) variations are found incidentally on cranial magnetic resonance angiography (MRA). Our goal was to examine the incidence and types of MCA variations detected by MRA. Between April 1996 and March 1999, cranial MRA was performed in 432 cases at our institution. Most of the patients examined had or were suspected to have cerebrovascular disease. After excluding 7 patients with moyamoya disease, we retrospectively reviewed 425 MRA results. A 1.5-T scanner was used in all studies, and maximum-intensity projection images obtained using the three-dimensional time-of-flight technique were displayed stereoscopically. In the 425 patients MRA revealed 16 anomalous MCAs, including 9 duplicated MCAs, 5 accessory MCAs, and 2 fenestrated MCAs, which is a rate of 3.8 %. Thus, although the clinical significance is not great, we found a relatively high incidence of anomalous MCAs on MRA. We stress that knowledge and recognition of these variations are useful and important during the interpretation of cranial MRA. Received: 3 August 1999; Revised: 22 November 1999; Accepted: 22 November 1999     

Assessment of renal artery stenosis by phase-contrast magnetic resonance angiography

Three-dimensional (3D) phase-contrast magnetic resonance angiography (MRA) and velocity-encoded cine magnetic resonance (VEC-MR) imaging were performed in 23 subjects to assess the severity of renal artery stenosis. MRA was used for detection of stenosis, demonstrating a sensitivity of 100% and a specificity of 80%; the severity of stenosis was overestimated in 33%. VEC-MR was used to quantify the renal flow oattern and was successful in 11 subjects. Mean blood flow of normal renal arteries (420 +- 107 ml/min) was significantly higher (P < 0.01) than mean blood flow of stenotic arteries (131 +- 46ml/min). The flow profile displayed both systolic and diastolic peaks in 75% of the normal arteries, while the flow in stenotic arteries showed only a single systolic peak in all cases. The systolic peak in stenotic arteries occurred significantly later (32 +- 3% of the period of one cardiac cycle) than in normal subjects (21 +- 7%) (P < 0.05). Phase-contrast MR is likely to gain considerable importance in the noninvasive aetection and quantification of renal artery stenosis. Correspondence to: C. S. Richter     

Coronary artery anomalies

Coronary artery anomalies are uncommon findings but can be of significant clinical importance in a small number of individuals. Clinical presentation depends on the specific anomaly. Most coronary artery anomalies are benign and clinically insignificant, however, some anomalies are potentially significant and can lead to heart failure and even death. Noninvasive imaging has emerged as the preferred way to image coronary anomalies. Both electron beam computed tomography (EBCT) and magnetic resonance angiography (MRA) are useful for the diagnosis of anomalous coronary arteries. Recently, MDCT has also proven to be very useful in the detection and characterization of anomalous coronary arteries. This chapter will review the appearance of the most commonly encountered coronary anomalies on MDCT.     

Coronary artery anomalies: Role of contrast enhanced MDCT coronary angiography

Objective

The purpose of this study is to evaluate the role of MDCT in the depiction of coronary artery anomalies.

Patients and methods

Sixteen patients were included in this study. Retrospectively gated coronary CT angiography was performed in 11 patients and prospectively gated CT coronary angiography was performed in 5 patients. Post-processing techniques as maximum-intensity projection, curved multiplanar reconstruction, and volume rendering were applied to assess the origin and course of the coronary vessels.

Results

Origin and course anomalies of the central coronary artery segments were seen in 11 patients (67%), anomalies of only coronary artery origin in 2 patients (13%), origin and course anomalies of the peripheral coronary segments in 2 patients (13%) and coronary arterio-venous fistula in one patient (7%). The origin and course anomalies of the central coronary artery segment were more common in the left coronary artery involving 8 patients (73%). Malignant inter-arterial course between aortic root and pulmonary artery or the right ventricle outflow tract was seen in 3 anomalous arteries.

Conclusion

MDCT coronary angiography can precisely depict the origin and course coronary artery anomalies and is recommended in young patients and before cardiac intervention or surgery to prevent possible complications.     

Coronary artery anomalies: assessment with free-breathing three-dimensional coronary MR angiography

PURPOSE: To evaluate a simplified protocol by using free-breathing three-dimensional (3D) coronary magnetic resonance (MR) angiography to determine the anatomy of anomalous coronary arteries, in particular the relationship of the vessels to the aortic root. MATERIALS AND METHODS: Twenty-six patients (18 men, eight women; mean age, 50 years; age range, 18-77 years) who had a history of chest pain, palpitations, or syncope and who were suspected of having coronary artery anomalies were examined with free-breathing MR angiography. Multiple 3D volume slabs were acquired at the level of the sinuses of Valsalva by using diaphragmatic navigators for respiratory artifact suppression. The proximal anatomy of the coronary arteries was determined. RESULTS: Six anomalous circumflex arteries originated from the right sinus of Valsalva and passed behind the aortic root. Six right coronary arteries arose from the left sinus of Valsalva and coursed between the aortic root and the right ventricular outflow tract (RVOT). Nine left coronary arteries arose from the right sinus of Valsalva; seven of nine coursed between the aortic root and the RVOT. Five patients had minor anomalies. Overall, in eight patients with anomalous arteries that coursed between the aortic root and the RVOT, conventional coronary angiography could not be used confidently to identify the proximal course. CONCLUSION: Free-breathing 3D coronary MR angiography can be used to identify the proximal anatomy of anomalous coronary arteries.     

Atherosclerosis of the carotid artery: Evaluation by magnetic resonance angiography

Carotid artery atherosclerotic plaques (APs) can lead to brain ischemia, an event shown to correlate with both the degree of stenosis and the composition of the AP. Currently, accurate estimates of stenosis can be obtained by either x-ray angiography or three-dimensional time of-flight (TOF) magnetic resonance angiography (MRA). Our purpose was to determine whether three-dimensional TOF MRA images could also provide information on plaque location, morphology, and composition. Seven pre-endarterectomy patients underwent three-dimensional TOF MRA. After endarterectomy, plaque histology was evaluated. Three-dimensional TOF MRA images contained sufficient soft tissue contrast to differentiate the plaques from the surrounding tissues in all cases. Estimation of plaque morphology had 80% correlation with histology. Finally, intraplaque hemorrhage and calcification were depicted as regions of moderately high and very low intensity, respectively. These preliminary results suggest that three-dimensional TOF MRA may be useful in studying the development and progression of carotid atherosclerosis.     

Supraclinoid internal carotid artery fenestration from which the posterior communicating artery arising with infundibular dilatation at its origin diagnosed by magnetic resonance angiography

A 72-year-old man with vertigo underwent cranial magnetic resonance (MR) imaging and MR angiography using a 3.0-Tesla scanner. MR angiography showed an aneurysm-like lateral protrusion from the left supraclinoid internal carotid artery (ICA) and infundibular dilatation of the left posterior communicating artery at its origin. After creating both partial maximum-intensity-projection images and partial volume-rendering images, a fenestration of the supraclinoid ICA was found. The posterior communicating artery arose from the fenestrated segment, and its origin was dilated triangularly, indicating infundibular dilatation. Cerebral arterial fenestration is not so rare, but it is rarely found at the ICA. The majority of recently reported cases had an associated aneurysm at the proximal end of the fenestration diagnosed using three-dimensional rotational angiography (3DRA). MR angiography is noninvasive and widely used for the screening of cerebral arterial lesions. Even though 3.0-Tesla scanner, special resolution of MR angiography is much lower than that of the 3DRA. For the diagnosis and confirmation of this rare variation, partial maximum-intensity-projection images and/or partial volume-rendering images are useful.     

Bilateral occipital arteries arising from the thyrocervical trunks (ascending cervical artery-occipital artery anastomosis) diagnosed by magnetic resonance angiography

We herein report a case of bilateral occipital arteries (OAs) arising from the thyrocervical trunks (TCTs). The patient was a 34-year-old woman with suspected basilar artery aneurysm underwent magnetic resonance (MR) angiography of the head and neck region using a 3-Tesla scanner. Cranial MR angiography revealed no aneurysm. Cervical MR angiography showed bilateral OAs arising from the TCTs. The extremely hyperplastic ascending cervical artery (ACA) arose from the transverse cervical artery, and continued to the OA, bilaterally. The OA usually arises from the proximal external carotid artery and runs posterosuperiorly; rarely, it arises from the internal carotid artery or the vertebral artery. The variation in our patient is regarded as bilateral ACA-OA anastomosis. Only one case of the unilateral type of this variation has been reported, having been diagnosed during dissection. Before cervical arterial intervention or head and neck surgery, identification of OA variation is important. During the interpretation of cervical MR angiography findings, careful observation of the origin and course of the OA is required.     

Whole-heart steady-state free precession coronary artery magnetic resonance angiography.

Current implementations of coronary artery magnetic resonance angiography (MRA) suffer from limited coverage of the coronary arterial system. Whole-heart coronary MRA was implemented based on a free-breathing steady-state free-precession (SSFP) technique with magnetization preparation. The technique was compared to a similar implementation of conventional, thin-slab coronary MRA in 12 normal volunteers. Three thin-slab volumes were prescribed: 1) a transverse slab, covering the left main (LM) artery and proximal segments of the left anterior ascending (LAD) and left circumflex (LCX) coronary arteries; 2) a double-oblique slab covering the right coronary artery (RCA); and 3) a double-oblique slab covering the proximal and distal segments of the LCX. The whole-heart data set was reformatted in identical orientations. Visible vessel length, vessel sharpness, and vessel diameter were determined and compared separately for each vessel. Whole-heart coronary MRA visualized LM/LAD (11.7 +/- 3.4 cm) and LCX (6.9 +/- 3.6 cm) over a significantly longer distance than the transverse volume (LM/LAD, 6.1 +/- 1.1 cm, P < 0.001; LCX, 4.2 +/- 1.2 cm, P < 0.05). Improvements in visible vessel length for RCA and LCX in the whole-heart approach vs. their respective targeted volumes were not significant. It is concluded that the whole-heart coronary MRA technique improves visible vessel length and facilitates high-quality coronary MRA of the complete coronary artery tree in a single measurement.     

Isolated rhombencephalosynapsis diagnosed by magnetic resonance imaging

A case of human rhombencephalosynapsis diagnosed in vivo by magnetic resonance imaging (MRI) is presented that demonstrates fusion of the dentate nuclei and agenesis of the cerebellar vermis. To our knowledge, this condition in its isolated form has been previously diagnosed only at necropsy. The developmental features of the cerebellum are discussed and correlation with cerebellar function is also presented. Recognition of this anomaly in the living patient may be useful in further understanding the clinical significance of segmentation of the rhombencephalon.     

脑静脉窦血栓的磁共振诊断

目的 探讨磁共振的常规扫描序列和三维相位对比法MR静脉造影(3D-PC法MRV)对脑静脉窦血栓的诊断价值.方法 共收集34例临床确诊的脑静脉窦血栓病例,男15例,女19例.年龄1～71岁,中位年龄38岁.所有病例均行常规MR序列,3D-PC法MRV扫描;急性期(1～5天)脑静脉窦血栓7例;亚急性期(6～21天)18例,慢性期(＞21天)9例.结果 急性期脑静脉窦血栓信号T1WI以等低信号为主,T2WI以低信号为主;亚急性期T1 WI以高信号为主,T2WI呈低或高信号;慢性期T1WI表现为等或低信号,T2 WI以高信号或流空信号.3D-PC法MRV主要表现为脑静脉窦的闭塞或充盈缺损.同时14例患者合并有脑实质异常,出血9例,缺血水肿5例.结论 常规MR序列与3D-PC法MRV显示脑静脉窦血栓具特征性,可做为理想的检查手段.     

Multiecho magnetic resonance angiography

Several pulse sequences which generate projected MR angiograms are presented. These pulse sequences exploit multiple-gradient refocused echoes to obtain several independent angiograms, which can be combined or separately analyzed to provide more information than an individual angiogram. For example, a series of angiograms, each with a different projection axis, can be obtained in the time required to obtain a single angiogram using a single-echo method. If the view angle of each echo is the same, then the acquired angiograms can be added to enhance the signal-to-noise ratio. Another pulse sequence simultaneously obtains two or more angiograms, sensitive to orthogonal flow components of the overall blood flow. These angiograms are then added to give an angiogram which is sensitive to flow in all directions.