Prog Med Phys.  2013 Jun;24(2):108-118.

Investigation of Perfusion-weighted Signal Changes on a Pulsed Arterial Spin Labeling Magnetic Resonance Imaging Technique: Dependence on the Labeling Gap, Delay Time, Labeling Thickness, and Slice Scan Order

• Byun JH
• Park MH
• Kang JY
• Lee JW
• Lee KW
• Jahng GH

Abstract

Currently, an arterial spin labeling (ASL) magnetic resonance imaging (MRI) technique does not routinely used in clinical studies to measure perfusion in brain because optimization of imaging protocol is required to obtain optimal perfusion signals. Therefore, the objective of this study was to investigate changes of perfusion-weighed signal intensities with varying several parameters on a pulsed arterial spin labeling MRI technique obtained from a 3T MRI system. We especially evaluated alternations of ASL-MRI signal intensities on special brain areas, including in brain tissues and lobes. The signal targeting with alternating radiofrequency (STAR) pulsed ASL method was scanned on five normal subjects (mean age: 36 years, range: 29~41 years) on a 3T MRI system. Four parameters were evaluated with varying: 1) the labeling gap, 2) the labeling delay time, 3) the labeling thickness, and 4) the slice scan order. Signal intensities were obtained from the perfusion-weighted imaging on the gray and white matters and brain lobes of the frontal, parietal, temporal, and occipital areas. The results of this study were summarized: 1) Perfusion-weighted signal intensities were decreased with increasing the labeling gap in the bilateral gray matter areas and were least affected on the parietal lobe, but most affected on the occipital lobe. 2) Perfusion-weighted signal intensities were decreased with increasing the labeling delay time until 400 ms, but increased up to 1,000 ms in the bilateral gray matter areas. 3) Perfusion-weighted signal intensities were increased with increasing the labeling thickness until 120 mm in both the gray and white matter. 4) Perfusion-weighted signal intensities were higher descending scans than asending scans in both the gray and white matter. We investigated changes of perfusion-weighted signal intensities with varying several parameters in the STAR ASL method. It should require having protocol optimization processing before applying in patients. It has limitations to apply the ASL method in the white matter on a 3T MRI system.

Keyword

Arterial spin labeling; Labeling gap; Labeling delay time; Labeling thickness; Slice scan order

MeSH Terms

Brain
Humans
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Magnetics
Magnets
Occipital Lobe
Parietal Lobe
Perfusion

Figure

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  Fig. 1. Descriptions of the experimental conditions of the labeling gap, the labeling thickness, slice scan orders (a), and the labeling delay time (TI) (b).

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  Fig. 2. Definitions of the region-of-interests (ROI) of gray matter and white matter (a), the frontal lobe (b), the temporal lobe (c), the occipital lobe (d), and the the parietal lobe (e) drawing on a T2-weighted image.

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  Fig. 3. Experimental results of changing the labeling gaps: perfusion-weighted images (a) and the corresponding signal-intensities in the the gray (GM) and white (WM) matters (b) and in the the frontal (FL), parietal (PL), temporal (TL), and occipital (OL) lobes (c). Rt: right; Lt: left. The labeling gaps were 0 (A), 5 (B), 10 (C), 15 (D), 20 (E), 25 (F), and 30 (G) mm in Fig. 3a. There was statistically signidicant difference between right and left signal intensities in the gray matter (p=0.0169), but not in the white matter (p=0.0510). There was statistically signidicant difference between right and left signal intensities in the parietal lobe (p=0.0417), but not in the temporal (p=0.2530) and frontal (p=0.3279) lobes.

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  Fig. 4. Experimental results of changing the labeling delay times: perfusion-weighted images (a) and the corresponding signal intensities in the gray (GM) and white (WM) matters (b) and in the the frontal (FL), parietal (PL), temporal (TL), and occipital (OL) lobes (c). Rt: right; Lt: left. The labeling delay times were 50 (A), 200 (B), 400 (C), 600 (D), 800 (E), 1,000 (F), 1,200 (G), 1,400 (H), 1,600 (I), 1,800 (J), and 2,000 (K) ms in Fig. 4a. There was not statistically signidicant difference between right and left signal intensities in both the gray matter (p=0.4230) and the white matter (p=0.3897). There was not statistically signidicant difference between right and left signal intensities in the parietal lobe (p=0.5392), the temporal (p=0.6891) and frontal (p=0.6619) lobes.

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  Fig. 5. Experimental results of changing the labeling thicknesses: perfusion-weighted images (a) and the corresponding signal intensities in the gray (GM) and white (WM) matters (b) and in the the frontal (FL), parietal (PL), temporal (TL), and occipital (OL) lobes (c). Rt: right; Lt: left. The labeling thicknesses were 40 (A), 60 (B), 80 (C), 100 (D), 120 (E), 140 (F), 160 (G), 180 (H), and 200 (I) mm in Fig 5a. There was not statistically signidicant difference between right and left signal intensities in both the gray matter (p=0.1713) and the white matter (p=0.9922). There was not statistically signidicant difference between right and left signal intensities in the parietal lobe (p=0.6257), the temporal (p=0.6619) and frontal (p=0.7477) lobes.

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  Fig. 6. Perfusion-weighted images obtained with changing the slice scan orders (a. ascend, b. descend).

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