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.     

Pediatric head and neck lesions: assessment of vascularity by MR digital subtraction angiography

BACKGROUND AND PURPOSE: Pediatric head and neck lesions can be difficult to characterize on clinical grounds alone. We investigated the use of dynamic MR digital subtraction angiography as a noninvasive adjunct for the assessment of the vascularity of these abnormalities. METHODS: Twelve patients (age range, 2 days to 16 years) with known or suspected vascular abnormalities were studied. Routine MR imaging, time-of-flight MR angiography, and MR digital subtraction angiography were performed in all patients. The dynamic sequence was acquired in two planes at one frame per second by using a thick section (6-10 cm) selective radio-frequency spoiled fast gradient-echo sequence and an IV administered bolus of contrast material. The images were subtracted from a preliminary mask sequence and viewed as a video-inverted cine loop. RESULTS: In all cases, MR digital subtraction angiography was successfully performed. The technique showed the following: 1) slow flow lesions (two choroidal angiomas, eyelid hemangioma, and scalp venous malformation); 2) high flow lesions that were not always suspected by clinical examination alone (parotid hemangioma, scalp, occipital, and eyelid arteriovenous malformations plus a palatal teratoma); 3) a hypovascular tumor for which a biopsy could be safely performed (Burkitt lymphoma); and 4) a hypervascular tumor of the palate (cystic teratoma). CONCLUSION: Our early experience suggests that MR digital subtraction angiography can be reliably performed in children of all ages without complication. The technique provided a noninvasive assessment of the vascularity of each lesion that could not always have been predicted on the basis of clinical examination or routine MR imaging alone.     

Flow phenomena, classification, and clinical aspects of magnetic resonance angiography

Both time-of-flight and phase-contrast techniques are currently being employed in producing angiographic MR images of arteries and veins. Both two-dimensional and three-dimensional acquisition methods can be used to display projective vascular images with the maximum intensity projection algorithm, eliminating the need for image subtraction. MR angiography has expanded the armamentarium of MR imaging, especially in the head and neck, and should in some organ systems reduce the need for conventional x-ray catheter angiography.     

Congenital thoracic vascular anomalies: evaluation with state-of-the-art MR imaging and MDCT

Congenital thoracic vascular anomalies include embryologic developmental disorders of the thoracic aorta, aortic arch branch arteries, pulmonary arteries, thoracic systemic veins, and pulmonary veins. Diagnostic evaluation of these anomalies in pediatric patients has evolved with innovations in diagnostic imaging technology. State-of-the-art magnetic resonance (MR) imaging, MR angiography multidetector-row computed tomographic (MDCT) angiography, and advanced postprocessing visualization techniques offer accurate and reliable high-resolution two-dimensional and three-dimensional noninvasive anatomic displays for interpretation and clinical management of congenital thoracic vascular anomalies. This article reviews vascular MR imaging, MR angiography, MDCT angiography, and advanced visualization techniques and applications for the assessment of congenital thoracic vascular anomalies, emphasizing clinical embryology and the characteristic imaging findings.     

MR angiography in children with cerebral neurovascular diseases: findings in 31 cases.

OBJECTIVE. We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease. SUBJECTS AND METHODS. Thirty-one children, 6 months to 14 years old, with intracranial lesions or clinically suspected vascular malformations were studied prospectively with conventional MR imaging and time-of-flight MR angiography. In nine cases, MR angiographic findings were verified with digital subtraction angiography or conventional angiography. All MR studies were performed on a 1.5-T MR system using a circularly polarized head coil. RESULTS. Arterial MR angiography, performed in 24 cases, revealed congenital abnormalities of the arterial vessels in 20 cases. Vessel stenosis was observed in nine patients, and displacement of intracranial arteries due to tumors could be seen in 10 patients. Seven children had no abnormal findings. Venous MR angiography was performed in seven children, with depiction of sinus thrombosis in six cases. The comparative analysis of MR angiography and digital subtraction angiography showed equivalent results in nine patients; in one patient the degree of stenosis was overestimated with MR angiography. CONCLUSION. MR angiography, when combined with MR imaging, reveals information about soft-tissue and vascular structures in a single setting. At this point, MR angiography can replace invasive conventional angiography or digital subtraction angiography only in selected cases because of software and hardware limitations. Arterial or venous MR angiography can be helpful as an additional scan in MR examinations of children with suspected cerebral neurovascular diseases, and its noninvasive nature makes it well suited for routine use in children.     

Magnetic resonance angiography in the head-neck area

Magnetic resonance angiography is a noninvasive method in vascular imaging using non-contrast-enhanced and contrast-enhanced techniques. The contrast media used in contrast-enhanced magnetic resonance angiography are different from the X-ray contrast me-dia and do not affect the thyroid gland or renal function. In detecting hypervascularized lesions in the head and neck, contrast-enhanced magnetic resonance angiography is the method of choice, which provides an acceptable quality in comparison to digital subtraction angiography. Future developments in magnetic resonance imaging techniques will cause a wider use of magnetic resonance angiography, especially in head and neck imaging. Digital subtraction angiography should therefore only be used in problem cases and for preoperative embolization.     

46例脑动静脉畸形的MRI和MRA分析

目的：探讨MRI和MRA检查在脑AVM临床诊断中的价值。方法：46例脑动静脉畸形作了常规MRI和MR血管造影,MRI采用SET1、T2加权成像,MRA采用三维时飞跃法。结果：MRI准确显示了46例AVM的瘤巢,11例可见亚急性出血灶,5例可见含铁血黄素沉积,23例病灶区组织软化或萎缩,4例有占位效应。3D-TOF RMA显示41例AVM供血动脉、23例引流静脉。5例加做增强3D-TOF及6例加做2D-TOF后,引流静脉显示明显改善。结论：MRI和MRA结合应用能对脑血管畸形作出较准确的诊断,为临床治疗提供所需的基本信息并对治疗效果作出客观的评价。     

Three-dimensional time-of-flight MR angiography with a surface coil: evaluation in 12 subjects.

We compared three-dimensional time-of-flight MR angiograms obtained with head coils and then with surface coils in five patients with intracranial vascular lesions and in seven normal volunteers to determine if imaging of intracranial vascular anatomy could be improved with the use of a surface coil. Visualization of small peripheral vessels was consistently better with a surface coil than with a head coil at identical small fields of view (FOVs). The surface-coil technique allowed small-FOV imaging of peripheral vascular lesions with higher spatial resolution and signal-to-noise ratio similar to that of large-FOV head-coil images. The use of a surface coil introduced the problem of signal falloff; centrally located vessels were visualized as well or better when a standard head coil was used. We conclude that surface-coil MR angiography can serve as a useful adjunct to routine head-coil MR angiography in the evaluation of peripheral vascular abnormalities.     

MR imaging of partial anomalous pulmonary venous connections

Magnetic resonance imaging was performed on 11 patients with partial anomalous pulmonary venous connections (PAPVC). Ten of these patients also had echocardiographic examinations, eight of which included color-flow Doppler studies. The diagnosis of PAPVC was confirmed in each of these patients by surgery or angiography. Fourteen anomalous pulmonary venous connections were identified, 10 involving the right upper lobe pulmonary vein and 4 involving the left upper lobe pulmonary vein. This retrospective review demonstrated that all 14 anomalous venous connections were correctly identified by MR imaging, whereas only 8 of 13 (62%) were identified by echocardiography. With MR, 89% of all the pulmonary veins and 93% of the anomalous pulmonary veins were visualized on axial images, while 41% of all pulmonary veins and 71% of anomalous veins were seen on coronal MR images. There were five atrial septal defects (ASDs), four of the sinus venous type and one of the septum secundum type. All five ASDs were correctly identified with MR imaging; three of four ASDs were identified with echocardiography. We conclude that MR imaging provides an accurate noninvasive method of depicting the anatomic abnormalities associated with PAPVC.     

Advances in vascular echoplanar imaging

Magnetic resonance (MR) angiography is emerging as an increasingly useful tool for the noninvasive evaluation of the cardiovascular system. Ultrafast echoplanar imaging (EPI) data acquisition strategies are becoming more widely available. When applied to MR angiography, the associated reduction in data collection time allows breathheld acquisitions of entire vascular territories, as well as the exploitation of short-lived flow-enhancing measures. This paper describes technical aspects of EPI, its implementation into vascular imaging sequences, and associated artifacts. This is followed by a discussion of potential EPI MRA applications in the carotid and renal arteries, the portal venous system, and arteries and veins of the lower leg.     

Magnetic resonance applications in cerebral injury.

CT and MR imaging are complementary in the evaluation of cerebral head trauma. CT is still more useful for the initial evaluation of the acutely unstable patient who has a head injury. However, many lesions are identified by MR imaging such as cortical contusions, small subdural hematomas, and diffuse axonal injuries that may not be seen on CT examinations. In addition, MR angiography can play an important role in the diagnostic evaluation of the trauma patient. MR angiography can be clinically useful in delineating vascular abnormalities such as arterial occlusions, arteriovenous fistulae, dissecting aneurysms, and venous sinus occlusion. In pediatric trauma, MR imaging appears to be superior to CT in assessing head injuries, particularly those due to child abuse.     

MR-Tomographie des Herzens

The introduction of magnetic resonance (MR) tomography has fundamentally changed radiological diagnosis for many diseases. Invasive digital subtraction angiography has already been widely replaced by noninvasive MR angiography for most of the vascular diseases. The rapid technical development of MR imaging in recent years has opened new functional imaging techniques. MR imaging of the heart allows simultaneous measurement of morphological and functional parameters in a single noninvasive examination without any radiation exposure. Because of the high spatial resolution and the reproducibility cine MR imaging is now the gold standard for functional analysis. With the improvement of myocardial perfusion and viability studies many diseases of the heart can be diagnosed in a single examination. MR spectroscopy is the only method which allows a view of the metabolism of the heart. New examinations for vascular imaging and flow quantification complete the goal of "one-stop-shop" imaging of the heart. MR imaging is the only diagnostic modality which allows a complete evaluation of many diseases of the heart with one technique, basic examination as well as follow-up studies. The very rapid improvement in MRI will overcome most of the limitations in the near future, especially concerning MR coronary angiography.     

Use trends and geographic variation in neuroimaging: nationwide medicare data for 1993 and 1998.

BACKGROUND AND PURPOSE: Powerful tools, including CT and MR imaging, have revolutionized neuroimaging. These are routinely used, but the extent and variation of use has not been studied. Our purposes were to determine the use rates of MR imaging and CT (of spine, brain, or head and neck), myelography, conventional angiography, and MR angiography in diagnosing neurologic disorders; to study trends in use; and to determine regional variations in use. METHODS: We used the National Part B Medicare Database for 1993 and 1998 to compare rates of use for these procedures in 10 geographic regions. RESULTS: In 1993 and 1998, respectively, 13,897 and 19,431 (39.8% increase) neuroimaging procedures were performed per 100,000 Medicare beneficiaries nationwide. Use of brain or head and neck CT (30.4%) and MR imaging (43.6%), spinal CT (3.5%) and MR imaging (83.0%), myelography (56.6%), and conventional angiography (24.3%) increased in 1998 versus 1993. Increases in MR angiography were not assessed, because this procedure was not reimbursable in 1993. Regional use of brain or head and neck and spinal CT and MR studies varied considerably; ratios of highest and lowest rates were 1.38-1.56. Use of MR angiography, myelography, and conventional angiography varied three- to fourfold. CONCLUSION: Use of MR and CT studies of the brain or head and neck and of the spine increased considerably in the Medicare population between 1993 and 1998. Use of conventional invasive procedures such as myelography and angiography increased strikingly, contrary to the expected decline. Regional use varied substantially.     

Angeborene Fehlbildungen der Aorta im Kindes- und Jugendalter

Aortic abnormalities are common cardiovascular malformations accounting for 15-20% of all congenital heart disease. Ultrafast CT and MR imaging are noninvasive, accurate and robust techniques that can be used in the diagnosis of aortic malformations. While their sensitivity in detecting vascular abnormalities seems to be as good as that of conventional catheter angiocardiography, at over 90%, they are superior in the diagnosis of potentially life-threatening complications, such as tracheal, bronchial, or esophageal compression. It has been shown that more than 80% of small children with aortic abnormalities benefit directly from the use of noninvasive imaging: either cardiac catheterization is no longer necessary or radiation doses and periods of general anesthesia for interventional catheterization procedures can be much reduced.The most important congenital abnormalities of the aorta in children and adolescents are presented with reference to examples, and the value of CT and MR angiography is documented.     

MRI of the pulmonary veins: comparison between 3D MR angiography and T1-weighted spin echo

OBJECTIVE: The purpose was to determine the ability of three-dimensional (3D) magnetic resonance (MR) angiography to depict normal pulmonary veins in comparison with spin-echo MR imaging. MATERIALS AND METHODS: MR imaging of 40 patients with cardiovascular disease were reviewed. Patients with known pulmonary venous abnormalities were excluded. Using a standard GE 1.5-T magnet, axial T1-weighted spin-echo 5-mm-thick contiguous slices and 3D MR angiography (contiguous slice thickness of 2.5-3.5 mm, 20-30 c.c. of gadolinium bolus at 1-1.5 c.c./sec, 32-43-second breath-hold, coronal and sagittal plane acquisition) were evaluated retrospectively on separate occasions by two experienced radiologists. Multiplanar imaging projection was used for the identification of pulmonary veins. Each lung was considered to have two drainage veins: a superior vein and an inferior vein. Identification of a pulmonary vein was made by visualizing a connection with the left atrium. RESULTS: 143 pulmonary veins (87.5% +/-5.2) were identified at the level of the left atrium on T1-weighted spin-echo images, and 157 (98.1% +/-1.9) were identified on 3D MR angiography (p<0.01). Overall we identified by T -weighted spin-echo imaging 36 right upper, 38 right lower, 27 left upper, and 38 left lower pulmonary veins. By 3D MR angiography, we identified 38 right upper, 40 right lower, 39 left upper, and 40 left lower pulmonary veins. All four pulmonary veins were detected in 22 patients on spin-echo imaging (55%) and in 37 patients (92.5%) on 3D MR angiography (chi = 3.81, p<0.05). CONCLUSION: A significant difference is demonstrated between 3D MR angiography and spin-echo MR imaging in identifying normal pulmonary veins. MR angiography provides a complete view of normal pulmonary venous anatomy and could be a valuable tool for the assessment of abnormal pulmonary venous drainage.     

Gadolinium-enhanced CT angiography of the circle of Willis and neck

CT angiography (CTA) of the cervical and intracranial vessels is a rapid, noninvasive, and relatively inexpensive technique for the evaluation of vascular abnormalities. Contraindications to the use of contrast media, however, can preclude use of iodinated agents for CTA. We report the use of gadolinium as contrast agent for CTA of the head and neck in three patients with contraindications to iodinated contrast agents.     

Suspected dural arteriovenous fistula: results with screening MR angiography in seven patients.

Previous studies have shown that spin-echo (SE) magnetic resonance (MR) imaging has been helpful in the assessment of dural arteriovenous fistula (DAVF); however, direct visualization of the fistula site is limited. Thus, conventional plain angiography is required to establish the diagnosis. Because of this limitation, the additional use of MR angiography may improve noninvasive screening for this disorder. Seven patients with DAVFs proved at plain angiography were evaluated with SE MR imaging and with three-dimensional (3D) time-of-flight (TOF) MR angiography. In six of seven cases, 3D TOF MR angiography demonstrated the fistula site. Correlation was good when compared with findings at plain angiography. Occlusion of the dural sinus was found at plain angiography in three of seven patients but was missed at SE imaging in all three. MR angiography also failed to demonstrate sinus occlusion in two of three patients. Arterial feeders could not be seen on SE MR images, but MR angiography improved their depiction. Plain angiography demonstrated abnormal venous drainage into distended cortical veins in three patients, but dilated cortical veins were noted in only two of the patients on both SE MR images and MR angiograms.     

Extracardiac vasculature in candidates for Fontan surgery: MR imaging

Magnetic resonance (MR) imaging was performed in 53 patients considered to be candidates for a modified Fontan operation to repair cardiac or extracardiac vascular anomalies. The MR studies were reviewed retrospectively, and the findings with regard to the extracardiac vascular anatomy were compared with the findings from angiography or surgery. The accuracy of MR for the correct identification of the systemic veins was 98%; for pulmonary arteries, 97%; and for pulmonary veins, 95%. For identification of pulmonary veins, MR imaging had a sensitivity of 90% and a specificity of 100%. MR provides excellent demonstration of the extracardiac vascular structures, which are of particular importance in patients being considered for a Fontan procedure.     

Incidence of postangiographic abnormalities revealed by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Occasionally we have observed anecdotal cases of asymptomatic hyperintensities on diffusion-weighted MR (DW-MR) examinations of the brain of patients who previously underwent routine cerebral angiography. These observations, as well as MR imaging and transcranial Doppler data in the literature suggesting a high rate of procedure-associated emboli, raise concern regarding the underdiagnosis of asymptomatic focal infarction associated with cerebral angiography. In order to determine whether asymptomatic diffusion abnormalities are frequently associated with procedures, we prospectively obtained DW-MR images before and after routine cerebral angiography. METHODS: Twenty consecutive patients, who met protocol criteria and received a routine three- or four-vessel diagnostic cerebral angiogram at our institution, were evaluated. Using a Bayesian estimate to establish an upper bound for the incidence of an event with zero occurrences in a study sample, the study group size was selected to exclude a 10% incidence of abnormalities revealed by DW-MR imaging of patients who underwent previous cerebral angiography. Two neuroradiologists evaluated imaging studies. RESULTS: Neither clinical signs nor abnormalities on DW-MR images were found, which suggested no infarction after angiography in our patient sample. Based on this data, an upper bound of 9% (95% confidence) is predicted for the appearance of abnormalities revealed by DW-MR imaging after cerebral angiography. CONCLUSION: Cerebral angiography is associated with an incidence of asymptomatic cerebral infarction of no more than 9%. It well may be substantially lower than this estimate; a more accurate evaluation of the true incidence would require a significantly larger study population. This test provides a convenient noninvasive means of assessing procedure-related cerebral infarction, such as that which occurs after carotid endarterectomy or vascular angioplasty and stenting.     

Noninvasive imaging of living related kidney donors: evaluation with CT angiography and gadolinium-enhanced MR angiography.

OBJECTIVE: This study was performed to determine whether noninvasive imaging with CT angiography and MR angiography in the preoperative investigation of living, related kidney donors provides sufficient information for the surgeon. MATERIALS AND METHODS: Eighty consecutive potential living kidney donors were investigated. Fifty patients underwent CT angiography and 30 underwent MR angiography before donor nephrectomy. CT was performed using 3-mm collimation with a pitch of 1.6 after the injection of 150 mL of nonionic contrast medium. The axial data, multiplanar reconstructions, and maximum intensity projections were reviewed. MR angiography was performed on a 1-T magnet using a contrast-enhanced three-dimensional gradient echo technique. Maximum intensity projections and axial reformations were reviewed. Imaging findings were compared with the surgical results in 54 patients. RESULTS: CT angiography and MR angiography were 100% sensitive in identifying the main renal arteries and renal veins. CT angiography visualized 37 of the 40 arteries identified at surgery, for a detection rate of 93%. MR angiography visualized 18 of the 20 arteries identified at surgery, a detection rate of 90%. CONCLUSION: CT angiography and MR angiography are suitable for the noninvasive investigation of living kidney donors and provide all the information required by the surgeon. Both methods may miss small accessory renal arteries. MR angiography does not use potentially toxic contrast material or radiation and is the preferred investigation, with CT angiography reserved for patients unable to tolerate MR imaging.