A surface coil on the neck causes adiabatic fast passage in blood as it flows by through a magnetic field gradient. This allows separation of blood and stationary tissue images of the head. Coronal and sagittal images of a volunteer are presented showing the vertebral and common, internal and external carotid arteries in projection views. © 1986 Academic Press, Inc.

Projection angiograms of blood labeled by adiabatic fast passage

MR imaging of 15 paragangliomas in 10 patients was compared with CT of 13 of the lesions in eight patients. All lesions were confirmed with angiography. All lesions were detected by MR and CT with the exception of one small glomus tympanicum tumor that was seen only in retrospect with MR. CT better demonstrated subtle osseous changes of the skull base and the relation of the tumor to the middle ear structures. MR better demonstrated the relation of the tumor to the adjacent internal jugular vein and carotid artery. The paragangliomas had a characteristic MR appearance based on their vascularity. Serpiginous areas of signal void representing high vascular flow were interspersed among areas of high signal intensity caused by slowly flowing blood and tumor cells. This "salt-and-pepper" pattern was seen in all lesions greater than 2 cm in maximal dimension. MR was therefore able to accurately characterize the tumors as highly vascular. Multiplanar imaging and good tissue contrast and anatomic detail permitted display of the relations of these neoplasms to surrounding carotid sheath vessels and to intracranial structures better than did CT. In this experience, the MR appearance of paragangliomas was quite characteristic and differed markedly from meningiomas, neuromas, and metastatic disease of the skull base.

http://www.ajnr.org/content/ajnr/7/6/1039.full.pdf

MR imaging of paragangliomas

First symptoms and initial clinical, ultrasonographic and neuroradiological findings ascertained a mean of 5.6 days (SD = 5.6 days), 7.7 days (7.0), and 11.2 days (8.0) after symptom onset were analysed in 44 patients who suffered a spontaneous internal carotid artery dissection (ICD) verified by magnetic resonance imaging, angiography, or both. Common symptoms signalling dissection were unilateral headache in 68%, transient ischaemic attack in 20%, and cerebral infarction in 9%. Severe pain preceded cerebral ischaemia by more than 3 days in 60% of those patients who eventually suffered a stroke. However, only 2 were admitted because of pain alone and 33 for evolving neurological deficits. During the first month, ipsilateral severe headache occurred in 89%, neck pain in 36%, ipsilateral cerebral ischaemia in 82%, ocular ischaemia in 16%, oculosympathetic palsy in 48%, and cranial nerve palsy in 5%. Recent "trivial" head or neck trauma was elicited in 41%. Doppler and duplex sonography confirmed the clinical suspicion of ICD in 91.5% and in 96% of those with a significant stenosis or occlusion. MRI demonstrated a thickened vessel wall in all 33 imaged carotid dissections and a mural haematoma in 30. None of the 32 patients who received anticoagulant treatment subsequently deteriorated. Monitoring anticoagulant treatment with ultrasonographic follow-up studies demonstrated recanalization in 70% and persistent occlusion in 30%. The results demonstrate that familiarity with the initial symptoms, especially headache, and performance of an ultrasonographic study without delay are the cornerstones of an early diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous internal carotid artery dissection : early diagnosis and management in 44 patients

Magnetic resonance measurement of velocity and flow: technique, validation, and cardiovascular applications.

Blood flow phenomena occurring when flow is within the magnetic resonance (MR) imaging plane were analyzed. In this situation, the signal intensity of vascular lumina is predominantly determined by spin-phase change phenomena, and section transition effects of moving spins can be neglected. In this paper, we develop the concepts of in-plane flow, with emphasis on the notion that the spatial variations in velocity and acceleration of blood, which mainly occur along vessel walls, are important determinants of intravascular signal loss in MR images. Flow patterns in the large mediastinal arteries were qualitatively and quantitatively analyzed in six healthy subjects and 14 patients with hemodynamic abnormalities using multiple electrocardiograph-gated image acquisition; ungated studies of 30 patients were analyzed for venous flow effects. Intraluminal signal was strongly dependent on the phase of the cardiac cycle and the echo number. Signal loss was found to occur along vessel walls, in vascular bends, and ...

Blood flow imaging with MR: spin-phase phenomena.

The appearance of flowing fluid has been evaluated in several clinical situations using a flow phantom, computer simulation, and clinical magnetic resonance (MR) images. Unsaturated protons just entering the imaging volume can emit a strong signal relative to the partially saturated adjacent tissue ("flow-related enhancement"). Slow laminar flow in veins can be distinguished on the basis of a stronger second echo due to rephasing effects ("even echo rephasing"). Synchronization of the cardiac cycle and the MR pulsing sequence produces increased signal in sections acquired during diastole ("diastolic pseudogating"). Intraluminal signal is shown to decrease as velocity is increased ("high velocity signal loss"). Onset of turbulence causes further loss of signal. Direction of flow oblique to the imaging plane can be predicted on the basis of decreased upstream and increased downstream signal.

V Waluch

Papers

Blood flow: magnetic resonance imaging.