title: Sensitivity calibration with a uniform magnetization image to improve arterial spin labeling perfusion quantification.
abstract: Quantification of perfusion with arterial spin labeling MRI requires a calibration of the imaging sensitivity to water throughout the imaged volume. Since this sensitivity is affected by coil loading and other interactions between the subject and the scanner, the sensitivity must be calibrated in the subject at the time of scan. Conventional arterial spin labeling perfusion quantification assumes a uniform proton density and acquires a proton density reference image to serve as the calibration. This assumption, in the form of an assumed constant brain-blood partition coefficient, incorrectly adds inverse proton density weighting to the perfusion image. Here, a sensitivity calibration is proposed by generating a uniform magnetization image whose intensity is highly independent of brain tissue type. It is shown that such a uniform magnetization image can be achieved, and brain tissue perfusion values quantified with the sensitivity calibration agree with those quantified with a proton density image when segmentation of brain tissues is performed and appropriate partition coefficients are assumed. Quantification of brain tissue water density is also demonstrated using this sensitivity calibration. This approach can improve and simplify quantification of arterial spin labeling perfusion and may have broader applications to measurement of edema and sensitivity calibration for parallel imaging.
authors.affiliation: Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. wdai@bidmc.harvard.edu
authors.forename: Weiying
authors.initials: W
authors.lastname: Dai
authors.forename: Philip M
authors.initials: PM
authors.lastname: Robson
authors.forename: Ajit
authors.initials: A
authors.lastname: Shankaranarayanan
authors.forename: David C
authors.initials: DC
authors.lastname: Alsop
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D002138:Calibration; D002536:Cerebral Arteries / Q000033:anatomy & histology / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005240:Feasibility Studies; D007089:Image Enhancement / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods* / Q000592:standards*; D008404:Massachusetts; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels
chemical_list: D013113:Spin Labels