Arterial spin labeling perfusion MRI in brain and kidney based on compartmental modeling

Abstract

Arterial spin labeling (ASL) is a non-invasive MRI method for acquiring perfusion images by labeling the arterial blood using radio-frequency pulses. Due to its non-invasiveness and the small motions in the brain, ASL has been popular in many brain researches that require perfusion imaging. Recently, ASL has received increasing attention in the kidney because of technical advances in the ASL itself and related MRI techniques. In the first study in the dissertation, we discussed technical considerations of the ASL for renal applications, and the perfusion images acquired from normal subjects and transplanted kidney patients were analyzed to demonstrate its clinical utility. In the following two studies, we proposed new MR methods for measuring novel physiological metrics by combining ASL with diffusion-weighted imaging. In the second study, a novel diffusion-weighted arterial spin labeling (DWASL) sequence and perfusion kinetic model were proposed for measuring the water permeability in the blood-brain barrier in the brain. The proposed multi-delay multi-slice DWASL sequence was developed for systemically acquiring perfusion images at multiple time points. A novel three compartment model was developed and tested for extracting various perfusion and permeability parameters from the DWASL data such as cerebral blood flow, arterial transit time, arterial blood volume, and water exchange rate. The proposed technique was applied to young/elderly normal subjects and elderly patients with Alzheimer's disease. The perfusion and permeability characteristics, especially water exchange rate, were compared between cohorts for demonstration of clinical usefulness of the parameters. Finally, in the third study, we proposed a new two-compartment renal perfusion kinetic model to measure the glomerular blood transfer rate in the kidney for the first time. Subjects were scanned in the caffeine and control days, and the results showed caffeine-induced changes in glomerular blood transfer rate.