Published online before print February 16, 2005, 10.1148/radiol.2351031663
Amplitude-modulated Continuous Arterial Spin-labeling 3.0-T Perfusion MR Imaging with a Single Coil: Feasibility Study1
Jiongjiong Wang, PhD,
Yan Zhang, PhD,
Ronald L. Wolf, MD, PhD,
Anne C. Roc, MS,
David C. Alsop, PhD and
John A. Detre, MD
1 From the Departments of Radiology (J.W., Y.Z., R.L.W., J.A.D.) and Neurology (J.W., A.C.R., J.A.D.) and Center for Functional Neuroimaging (J.W., J.A.D.), University of Pennsylvania, 3 W Gates, 3400 Spruce St, Philadelphia, PA, 19104; and Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Mass (D.C.A.). Received October 13, 2003; revision requested January 7, 2004; final revision received May 27; accepted June 17. Supported by National Institutes of Health grants HD39621 and DA015149 and National Science Foundation grant BCS0224007. Address correspondence to J.W. (e-mail: wangj3@mail.med.upenn.edu).
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Figure 1. Evaluation of amplitude-modulated control in a healthy subject. Four of 12 transverse sections are shown, acquired by using the 3.0-T CASL method with the labeling plane placed at the pontomedullary junction (proximal) and above the brain (distal). Note that areas of static signal are almost completely subtracted during the distal label state.
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Figure 2. Mean fractional CASL signal (dM/Mcon) acquired at 3.0 T by using different gradient strengths and RF irradiation. Control modulation frequency is 100 Hz. Peak fractional CASL signal (0.70% ± 0.10) is obtained with 1.6-mT/m gradient and 2.25-µT (uT) RF irradiation.
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Figure 3. CASL difference perfusion images ( M) acquired at 3.0 T by using different gradient strengths and RF irradiation in a representative subject. One of 12 transverse sections is shown. Control modulation frequency is 100 Hz. Maximum perfusion contrast is observed with 1.6-mT/m gradient (G) and 2.25-µT (uT) RF irradiation.
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Figure 4. Mean fractional 3.0-T CASL signal (M/Mcon) as a function of control modulation frequency measured in whole-brain, gray matter, and white matter ROIs. Error bars indicate the standard deviation across subjects. Data were acquired with 1.6-mT/m gradient and 2.25-µT RF irradiation. Main effect of modulation frequency is not statistically significant.
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Figure 5. Comparison of the difference perfusion images acquired with single-section (SS) CASL method and amplitude-modulated (AM) CASL technique in a representative subject. Single transverse section is shown. Ratio of mean CASL signals obtained with amplitude-modulated and single-section approach is 0.74 ± 0.12.
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Figure 6. Comparison of 12 transverse sections of difference perfusion images (M) acquired by using amplitude-modulated CASL technique and PASL method in a representative subject at 3.0 T. Background noise on CASL and PASL perfusion images is scaled at the same level. Mean ratio of SNRs and SNR efficiencies in CASL versus PASL method is 1.33 and 1.15 in the whole brain, respectively.
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Figure 7. Perfusion-weighted images (M) acquired by using amplitude-modulated CASL method at 3.0 T with postlabeling delay times of 1.5 and 1.8 seconds in a 41-year-old woman with bilateral carotid steno-occlusive disease. Twelve transverse sections are shown. Vascular artifacts (arrows) are greatly reduced at longer delay time without apparent deterioration of perfusion image quality.
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Figure 8. T2-weighted fluid-attenuation inversion-recovery images (T2W FLAIR) and perfusion-weighted images (PWI) acquired by using the amplitude-modulated CASL method at 3.0 T in a 47-year-old man with glioblastoma multiforme. Twelve transverse sections are shown. Perfusion images show heterogeneous blood flow (arrows) in tumor regions.
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Copyright © 2005 by the Radiological Society of North America.
Is labeling efficiency; f is CBF; 
is tissue transit time (1.4 sec) (40); 
is the blood-tissue water partition coefficient (0.9 mL/g); Mcon is raw control image intensity; R1a is longitudinal relaxation rate of arterial blood (0.67 sec–1); R1s (1.15 sec–1) and R1ns (0.81 sec–1) are longitudinal relaxation rates of brain tissue with and without off-resonance RF saturation, respectively; R2*tissue (28.6 sec–1) and R2*blood (5.0 sec–1) are transverse relaxation rates of brain tissue and arterial blood, respectively; 
is duration of labeling pulses (2 sec); and w is postlabeling delay time (1.0-1.5 sec due to sequential image acquisition).