Simultaneous multi-slice (SMS) acquisition enhances the sensitivity of hemodynamic mapping using gas challenges.
Hemodynamic mapping using gas inhalation has received increasing interest in recent years. Cerebrovascular reactivity (CVR), which reflects the ability of the brain vasculature to dilate in response to a vasoactive stimulus, can be measured by CO2inhalation with continuous acquisition of blood oxygen level-dependent (BOLD) magnetic resonance images. Cerebral blood volume (CBV) can be measured by O2inhalation. These hemodynamic mapping methods are appealing because of their absence of gadolinium contrast agent, their ability to assess both baseline perfusion and vascular reserve, and their utility in calibrating the functional magnetic resonance imaging (fMRI) signal. However, like other functional and physiological indices, a major drawback of these measurements is their poor sensitivity and reliability. Simultaneous multi-slice echo planar imaging (SMS EPI) is a fast imaging technology that allows the excitation and acquisition of multiple two-dimensional slices simultaneously, and has been shown to enhance the sensitivity of several MRI applications. To our knowledge, the benefit of SMS in gas inhalation imaging has not been investigated. In this work, we compared the sensitivity of CO2and O2inhalation data collected using SMS factor 2 (SMS2) and SMS factor 3 (SMS3) with those collected using conventional EPI (SMS1). We showed that the sensitivity of SMS scans was significantly (p = 0.01) higher than that of conventional EPI, although no difference was found between SMS2 and SMS3 (p = 0.3). On a voxel-wise level, approximately 20-30% of voxels in the brain showed a significant enhancement in sensitivity when using SMS compared with conventional EPI, with other voxels showing an increase, but not reaching statistical significance. When using SMS, the scan duration can be reduced by half, whilst maintaining the sensitivity of conventional EPI. The availability of a sensitive acquisition technique can further enhance the potential of gas inhalation MRI in clinical applications.
Department of Radiology, Johns Hopkins University, Baltimore, MD, USA.|Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA.|Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA.
Harshan
H
Ravi
Department of Radiology, Johns Hopkins University, Baltimore, MD, USA.|Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA.
Peiying
P
Liu
Department of Radiology, Johns Hopkins University, Baltimore, MD, USA.|Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA.|Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan.
Shin-Lei
SL
Peng
Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA.
Hanli
H
Liu
Department of Radiology, Johns Hopkins University, Baltimore, MD, USA. hanzhang.lu@jhu.edu.|Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, USA. hanzhang.lu@jhu.edu.
Hanzhang
H
Lu
D000280:Administration, Inhalation; D001783:Blood Flow Velocity / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply / Q000502:physiology; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D017352:Echo-Planar Imaging / Q000379:methods; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000008:administration & dosage / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D002245:Carbon Dioxide; D010100:Oxygen
CO2; MRI; SMS; brain; cerebrovascular reactivity; gas inhalation