New Application of Nuclear Imaging in the Legs May Enable Early Detection of Cardiovascular Problems

Researchers have shown for the first time that SPECT/CT imaging can be used to quantify perfusion reserve of specific muscle groups in the lower limbs, which they directly related to exercise tolerance and cardiovascular fitness. The work opens the door for better evaluation and understanding of the underlying physiology associated with therapeutic interventions meant to improve perfusion and/or blood flow to specific muscles of the lower extremities.

“We started studying SPECT/CT in the lower extremities because we thought this technique could be used as screening tool for patients with peripheral artery disease (PAD) that may be asymptomatic,” says Mitchel Stacy, PhD, principal investigator in the Center for Regenerative Medicine in the Abigail Wexner Research Institute at Nationwide Children’s Hospital. “We suspected SPECT/CT imaging could detect underlying perfusion abnormalities in the legs that patients and clinicians weren’t aware of, so that physicians could have additional information for clinical management and potential therapies.”

The work was done by Dr. Stacy and his colleagues during his former appointment at Yale University School of Medicine, and published in the January issue of the Journal of Nuclear Cardiology. The study included 31 adults already receiving exercise stress tests for reasons such as chest pain, shortness of breath, and previous abnormal ECG, and the researchers gathered the imaging data without the need for additional radiation exposure, stress testing, or extended time in the hospital for patients. Each of the calf muscles they studied was significantly related to measures of exercise tolerance and cardiovascular fitness.

“We found that muscle perfusion measures in the legs were significantly related to patients’ exercise performance on treadmill stress tests and their heart rate recovery after completion of stress testing,” Dr. Stacy says.

The novel application of SPECT/CT imaging may be especially useful for early identification of circulation problems in the extremities among patients with type 2 diabetes or PAD, but according to Dr. Stacy, the technique could also prove useful for evaluating wound healing or other musculoskeletal disorders that are associated with underlying blood flow abnormalities. In addition, it could help quantify the physiological changes in perfusion that occur within specific muscles in response to various exercise programs or targeted therapies.

“Currently, clinicians prescribe exercise or perform vascular interventions for many patients who have underlying muscle ischemia, but there is limited understanding of the physiological responses to these interventions,” says Dr. Stacy. “SPECT/CT and other nuclear imaging methods, such as PET/CT, could be used as noninvasive tools to quantify and better understand the perfusion changes that occur within specific muscle groups and are associated with improvements in lower limb function and vascular health.”

Dr. Stacy and his colleagues are currently working on related research funded by the National Institutes of Health, using PET/CT and SPECT/CT imaging to determine if nuclear imaging can detect perfusion responses to vascular interventions directed at improving lower limb muscle perfusion, and if these imaging-detected changes in perfusion can predict clinical outcomes.

Reference:

Chou TH, Janse S, Sinusas AJ, Stacy MR. SPECT/CT imaging of lower extremity perfusion reserve: A non-invasive correlate to exercise tolerance and cardiovascular fitness in patients undergoing clinically indicated myocardial perfusion imaging. J Nucl Cardiol. 2020 Jan 14. [Epub ahead of print]