SPECT/CT Imaging: A Noninvasive Approach for Evaluating Serial Changes in Angiosome Foot Perfusion in Critical Limb Ischemia

Abstract

Objective: To investigate the feasibility of serial radiotracer-based imaging as a noninvasive approach for quantifying volumetric changes in microvascular perfusion within angiosomes of the foot following lower extremity revascularization in the setting of critical limb ischemia (CLI). Approach: A CLI patient with a nonhealing foot ulcer underwent singlephoton emission computed tomography (SPECT)/computed tomography (CT) imaging of the feet before and after balloon angioplasty of the superficial femoral artery (SFA) and popliteal artery. SPECT/CT imaging was used to evaluate serial changes in angiosome perfusion, which was compared to quantitative changes in peripheral vascular anatomy and hemodynamics, as assessed by standard clinical tools that included digital subtraction angiography (DSA), ankle-brachial index (ABI), and toe-brachial index (TBI). Results: Following revascularization, upstream quantitative improvements in stenosis of the SFA (pre: 35.4% to post: 11.9%) and popliteal artery (pre: 59.1% to post: 21.7%) shown by DSA were associated with downstream angiosomedependent improvements in SPECT microvascular foot perfusion that ranged from 2% to 16%. ABI measurement was not possible due to extensive arterial calcification, while TBI values decreased from 0.26 to 0.16 following revascularization. Innovation: This is the first study to demonstrate the feasibility of assessing noninvasive volumetric changes in angiosome foot perfusion in response to lower extremity revascularization in a patient with CLI by utilizing radiotracer-based imaging. Conclusion: SPECT/CT imaging allows for quantification of serial perfusion changes within angiosomes containing nonhealing ulcers and provides physiological assessment that is complementary to conventional anatomical (DSA) and hemodynamic (ABI/TBI) measures in the evaluation of lower extremity revascularization.

Grades of Below-the-Ankle Arterial Occlusive Disease following the Angiosome Perfusion: A New Morphological Assessment and Correlations with the Inframalleolar GVG Stratification in CLTI Patients

“…Though doubts about the real clinical benefit of WDR for both bypass and EVT have been raised in contemporary literature 1-8, 10, 19-21, 32, 37 , using modern microcirculatory diagnostic methods with valuable topographic information 10,19,40,42 . While some authors have found the assessment of anatomical 6,10,16,28 and physiological 16,40,41 angiosomal flow by MRI oximetry 40 , trans-cutaneous laser Doppler 16,28 , or peripheral SPECT-Scan perfusion 10,[41][42][43] useful, others have questioned the utility of topographic reperfusion using white-light tissue spectrophotometry 44 , and low-frequency oscillations analyzed by diffuse speckle contrast analysis 45 . The clinical value of all these studies that support or refute specific postoperative angiosomal microcirculatory changes is indisputable.…”

Low frequency oscillations assessed by diffuse speckle contrast analysis for foot angiosome concept

“…This implies that the analysis of Pearson's correlation coefficient also does not fully support to the foot angiosome concept. To date, regarding the angiosome concept, some studies have focused on assessment of peripheral tissue perfusion to identify the origin location of diabetic foot ulcers with bench-top optical modalities [29][30][31][32][33][34] , to evaluate the quantitative wound healing with high-resolution imaging modalities such as CT 35,36 , SPECT/CT 37,38 and MRI perfusion [39][40][41] , and to evaluate leg revascularization surgeries Table 6. Comparison of ranks between six cross-correlations and six Pearson's correlation (CORR) coefficients at zero lag and in supine posture according to baseline and release periods from one subject's foot.…”

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

“…Specifically, SPECT/CT imaging with technetium-99m ( 99m Tc)-tetrofosmin, a standard myocardial perfusion radionuclide that is retained based on mitochondrial membrane potential and tissue viability ( 18 ), has been shown to allow for evaluation of relative perfusion defects within specific vascular territories, or angiosomes, of the feet ( 19 ). Additionally, this approach has revealed utility for detecting resting differences in regional foot perfusion between CLI patients and healthy control subjects ( 19 ), assessing tissue viability that corresponds with the subsequent level of amputation ( 20 ), and quantifying regional improvements in relative perfusion within the foot that occurs in response to endovascular revascularization ( 21 , 22 ). Most recently and importantly, perfusion imaging of the feet using SPECT/CT imaging has also demonstrated prognostic value for predicting risk for lower extremity amputation in patients with CLI who underwent endovascular revascularization for limb salvage, where patients who were high perfusion responders to revascularization experienced greater limb salvage success compared to those who were categorized as low perfusion responders ( Figure 1 ) ( 22 ).…”