Author + information
- Received July 31, 2011
- Revision received February 22, 2012
- Accepted March 7, 2012
- Published online December 1, 2012.
- Amy W. Pollak, MD⁎,†,
- Craig H. Meyer, PhD†,‡,§,
- Frederick H. Epstein, PhD†,‡,§,
- Ronny S. Jiji, MD⁎,†,
- Jennifer R. Hunter, BSN†,‡,
- Joseph M. DiMaria, BS†,‡,
- John M. Christopher, RRT†,‡ and
- Christopher M. Kramer, MD⁎,†,‡,⁎ ()
- ↵⁎Reprint requests and correspondence:
Dr. Christopher M. Kramer, University of Virginia Health System, Departments of Medicine and Radiology, Lee Street, Box 800170, Charlottesville, Virginia 22908
Objectives This study hypothesized that arterial spin labeling (ASL) magnetic resonance (MR) imaging at 3-T would be a reliable noncontrast technique for measuring peak exercise calf muscle blood flow in both healthy volunteers and patients with peripheral arterial disease (PAD) and will discriminate between these groups.
Background Prior work demonstrated the utility of first-pass gadolinium-enhanced calf muscle perfusion MR imaging in patients with PAD. However, patients with PAD often have advanced renal disease and cannot receive gadolinium.
Methods PAD patients had claudication and an ankle brachial index of 0.4 to 0.9. Age-matched normal subjects (NL) had no PAD risk factors and were symptom-free with exercise. All performed supine plantar flexion exercise in a 3-T MR imaging scanner using a pedal ergometer until exhaustion or limiting symptoms and were imaged at peak exercise with 15 averaged ASL images. Peak perfusion was measured from ASL blood flow images by placing a region of interest in the calf muscle region with the greatest signal intensity. Perfusion was compared between PAD patients and NL and repeat testing was performed in 12 subjects (5 NL, 7 PAD) for assessment of reproducibility.
Results Peak exercise calf perfusion of 15 NL (age: 54 ± 9 years) was higher than in 15 PAD patients (age: 64 ± 5 years, ankle brachial index: 0.70 ± 0.14) (80 ± 23 ml/min – 100 g vs. 49 ± 16 ml/min/100 g, p < 0.001). Five NL performed exercise matched to PAD patients and again demonstrated higher perfusion (84 ± 25 ml/min – 100 g, p < 0.002). As a measure of reproducibility, intraclass correlation coefficient between repeated studies was 0.87 (95% confidence interval [CI]: 0.61 to 0.96). Interobserver reproducibility was 0.96 (95% CI: 0.84 to 0.99).
Conclusions ASL is a reproducible noncontrast technique for quantifying peak exercise blood flow in calf muscle. Independent of exercise time, ASL discriminates between NL and PAD patients. This technique may prove useful for clinical trials of therapies for improving muscle perfusion, especially in patients unable to receive gadolinium.
Supported by National Heart Lung Blood Institute grant no. R01 HL075792 (to Dr. Kramer), and National Institute of Biomedical Imaging and Bioengineering grant no. T32 EB003841 (to Dr. Pollak). Drs. Meyer, Kramer, and Epstein have received research support from Siemens Healthcare. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Eike Nagel, MD, PhD, served as Guest Editor for this paper.
- Received July 31, 2011.
- Revision received February 22, 2012.
- Accepted March 7, 2012.
- American College of Cardiology Foundation