Prognostic value of lower limb perfusion single-photon emission computed tomography-computed tomography in patients with lower limb atherosclerotic peripheral artery disease

Applications of SPECT and PET Imaging for the Physiological Evaluation of Lower Extremity Peripheral Artery Disease

Peripheral artery disease (PAD) is classified as the narrowing or complete occlusion of the lower extremity arteries due to atherosclerosis. The risk of developing PAD increases with increased age and risk factors such as smoking, diabetes, hypertension, and hypercholesterolemia. Current treatment for PAD involves lifestyle and symptom management, statin and antiplatelet therapy, and/or surgical interventions to improve quality of life with varying efficacy. PAD affects approximately 5 to 6 percent of the global population, with this global burden continuing to increase. Despite the increase in disease prevalence, no gold standard functional diagnostic tool has been established for enabling early detection of the disease, appropriate medical management, and prediction of adverse outcomes for PAD patients. The visualization and quantification of the physiological consequences of PAD are possible by way of nuclear imaging: specifically, via scintigraphy, single-photon emission computed tomography (SPECT), and positron emission tomography (PET) imaging. These non-invasive modalities, when combined with targeted radionuclides, possess utility for detecting functional perfusion deficits and provide unique insight into muscle tissue- and vascular-level characteristics of PAD patients. This review discusses the past, present, and emerging applications of hybrid nuclear imaging modalities in the evaluation and monitoring of patients with PAD.

Perfusion imaging techniques in lower extremity peripheral arterial disease

Lower limb peripheral arterial disease (PAD) characterizes the impairment of blood flow to extremities caused by arterial stenoses or occlusions. Evaluation of PAD is based on clinical examination, calculation of ankle-brachial index and imaging studies such as ultrasound, CT, MRI and digital subtraction angiography. These modalities provide significant information about location, extension and severity of macrovasular lesions in lower extremity arterial system. However, they can be also used to evaluate limb perfusion, using appropriate techniques and protocols. This information may be valuable for assessment of the severity of ischemia and detection of hypoperfused areas. Moreover, they can be used for planning of revascularization strategy in patients with severe PAD and evaluation of therapeutic outcome. These techniques may also determine prognosis and amputation risk in patients with PAD. This review gives a basic overview of the perfusion techniques for lower limbs provided by imaging modalities such as ultrasound, CT, MRI, digital subtraction angiography and scintigraphy and their clinical applications for evaluation of PAD and revascularization outcome.

Molecular Imaging of Lower Extremity Peripheral Arterial Disease: An Emerging Field in Nuclear Medicine

Peripheral arterial disease (PAD) is an atherosclerotic disorder of non-coronary arteries that is associated with vascular stenosis and/or occlusion. PAD affecting the lower extremities is characterized by a variety of health-related consequences, including lifestyle-limiting intermittent claudication, ulceration of the limbs and/or feet, increased risk for lower extremity amputation, and increased mortality. The diagnosis of lower extremity PAD is typically established by using non-invasive tests such as the ankle-brachial index, toe-brachial index, duplex ultrasound, and/or angiography imaging studies. While these common diagnostic tools provide hemodynamic and anatomical vascular assessments, the potential for non-invasive physiological assessment of the lower extremities has more recently emerged through the use of magnetic resonance- and nuclear medicine-based approaches, which can provide insight into the functional consequences of PAD-related limb ischemia. This perspectives article specifically highlights and discusses the emerging applications of clinical nuclear medicine techniques for molecular imaging investigations in the setting of lower extremity PAD.

Spinal Cord Stimulation Improves the Microvascular Perfusion Insufficiency Caused by Critical Limb Ischemia

OBJECTIVE

This retrospective case-controlled study intended to identify the benefits and efficacy of spinal cord stimulation (SCS) as a therapeutic strategy for patients with perfusion problems caused by critical limb ischemia (CLI). The outcomes of patients who received SCS were compared with those of patients who did not receive SCS.

METHODS

This study recruited 78 patients who were diagnosed with perfusion problems over the period of 2003-2011. Lower-limb Thallium-201 (²⁰¹ Tl) scintigraphy revealed that the patients exhibited a perfusion difference of <0.95. Thirty-seven of the recruited patients received SCS treatment and 41 did not receive SCS treatment. All patients received the same medication: 100 mg aspirin once a day and 500 mg paracetamol thrice a day. The outcomes of walking distance, walking time, and sleeping quality were measured and recorded. Pain intensities were evaluated using the visual analog scale (VAS) scoring system.

RESULTS

Prior to SCS implantation, patients in the SCS treatment group had worse walking distance (64.86 ± 40.80 vs. 613.70 ± 535.00, p < 0.001), walking time (2.65 ± 1.64 vs. 13.90 ± 11.91, p < 0.001), and sleep quality (1.70 ± 0.78 vs. 3.32 ± 1.17, p < 0.001) than patients in the non-SCS treatment group. At the one-year follow-up, however, patients in the SCS treatment group had significantly better walking distance (1595.00 ± 483.60, p < 0.001), walking time (48.92 ± 14.10, p < 0.001), and sleep quality (4.65 ± 0.92, p < 0.001) than patients in the non-SCS treatment group. Moreover, the VAS score of patients in the SCS treatment group improved one week (8.63 ± 0.54 vs. 4.48 ± 0.59, p < 0.001) and one year after SCS implantation (2.35 ± 0.62, p < 0.001). By contrast, at the one-year follow-up, the walking distance (277.60 ± 374.80, p = 0.002), walking time (9.44 ± 10.73, p = 0.078), sleep quality (2.20 ± 1.10, p < 0.001), and VAS score (7.98 ± 0.43, p = 0.020) of patients in the non-SCS treatment group worsened. Furthermore, lower-limb ²⁰¹ Tl scintigraphy revealed that microcirculation intensity increased in the lower extremities of patients in the SCS treatment group after SCS implantation relative to that before SCS implantation. Most importantly, 10 of the 41 patients in the non-SCS treatment group required the use of wheelchairs, whereas none of the patients in the SCS treatment group required the use of wheelchairs.

CONCLUSION

Treatment of CLI patient with SCS improved patient's walking ability, pain severity, and sleep quality. SCS should be considered as an effective treatment toward limb salvage in CLI.