SLR - July 2018 - Nicholas M. Williams

Radiotracer Imaging Allows for Noninvasive Detection and Quantification of Abnormalities in Angiosome Foot Perfusion in Diabetic Patients with Critical Limb Ischemia and Nonhealing Wounds

Reference: Alvelo JL, Papademetris X, Mena-hurtado C, et al. Radiotracer Imaging Allows for Noninvasive Detection and Quantification of Abnormalities in Angiosome Foot Perfusion in Diabetic Patients With Critical Limb Ischemia and Nonhealing Wounds. Circ Cardiovasc Imaging. 2018;11(5):e006932.

Scientific Literature Review

Reviewed By: Nicholas M. Williams, DPM
Residency Program: Ascension Columbia St. Mary’s Hospital, Milwaukee, WI

Podiatric Relevance: Diabetes is a condition that podiatrists encounter in a large portion of their patients. Peripheral vascular disease (PVD) is a commonly associated condition in people living with diabetes. Both macrovascular and microvascular compromise can cause wounds to develop and inhibit healing of diabetic foot ulcers. Critical limb ischemia (CLI) is an advanced form of PVD that presents with rest pain, a nonhealing arterial ulcer or gangrene. Currently, there is no standard quantification of the microvasculature of the foot. Using radiotracer-based imaging with SPECT/CT provides a noninvasive method to evaluate the angiosomes of the foot following revascularization. In this current study, the SPECT/CT imaging was compared to ankle-brachial indexes (ABI) of both diabetic and nondiabetic patients.

Methods: This study included healthy subjects (n=9) and patients living with diabetes, some with CLI (n=42) who met inclusion and exclusion criteria. All subjects were administered intravenous 99mTc-tetrofosmin, and SPECT imaging was done, which was followed by CT imaging for attenuation correction. The SPECT images were reconstructed and overlaid over the CT for quantification of perfusion and the angiosomes. Next, standard ABI measurements were obtained from all normal patients (n=9) and patients living with diabetes with CLI (n=30). Statistical analysis was performed to compare multiple factors.

Results:
SPECT/CT noninvasive images showed both quantitative and qualitative differences in microvascular foot perfusion represented by angiosomes of the foot. Correlational analysis of both the healthy and critical limb ischemia subjects demonstrated a significant relationship between ABI and SPECT angiosome perfusion. Most importantly, though, this relationship was not significant in correlational analysis of the diabetic CLI patient population.

Conclusions: In this study, SPECT/CT imaging was used to quantitatively assess the microvascular perfusion of angiosomes of the foot. This technique provides a noninvasive assessment of the angiosome perfusion, specifically in the setting of DM and CLI. In current practice, ABI measurements are commonly used to assess pedal vasculature, but many patients living with diabetes have microvasculature disease or have noncompressible vessels that do not allow for an accurate ABI measurement. In this study, it showed that there was not a statistically significant association among the diabetic CLI patient group between SPECT/CT imaging and ABI. SPECT/CT imaging provides a reliable microvascular and macrovascular assessment of foot perfusion. Although current techniques like toe-brachial index, transcutaneous oxygen pressure or skin perfusion pressures are performed to assess microvascular disease, SPECT/CT imaging can provide a quantitative and qualitative evaluation of specific angiosomes. Further studies should be done to compare the results of TBI, transcutaneous oxygenation and skin perfusion pressures with SPECT/CT.

The importance of this imaging modality is significant for both the podiatric surgeon and the vascular or interventional surgeons. This imaging could provide a baseline for a diabetic patient's microvasculature, especially in a particular angiosome where they have a nonhealing wound. It could aid the physician performing revascularization to assess for perfusion following a procedure. For the podiatric surgeon, it can also help determine an appropriate amputation level that would optimize healing. Overall, SPECT/CT imaging is a promising imaging modality that is relevant to all physicians treating the diabetic population with PVD.

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