Techniques for MR Myocardial Perfusion Imaging
Outside the field of MRI, most techniques for myocardial perfusion imaging rely on the detection of injected tracers to assess myocardial blood flow and detect ischemia. Examples are tracers that emit gamma rays for single-photon emission tomography or tracers that scatter ultrasound waves, such as injected gas-filled bubbles. With MRI, blood-borne contrast agents can be used to assess myocardial perfusion. The presence of the contrast agent in tissue is detected through its effects on the local T1 and T2 relaxation times of 1H nuclei. An alternative approach for assessing myocardial perfusion without using an exogenous contrast agent relies on selectively “labeling” 1H spins and detecting the signal changes that are induced by tissue blood flow carrying “labeled” 1H spins in or out of an image slice. Though the absence on contrast agents makes arterial spin labeling an attractive proposition, its use is limited by the relatively small signal changes that need to be detected for quantifying myocardial perfusion. This chapter will focus foremost on contrast-enhanced perfusion imaging, as it remains the most widely used approach for myocardial perfusion imaging.
KeywordsT1 and T2 Perfusion imaging Pulse sequence techniques Arterial input sampling Spatiotemporal sampling Signal analysis Spin labeling 3D perfusion Imaging acceleration
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