The Use of Quantitative SPECT/CT Imaging to Assess Residual Limb Health

Background: In accordance with the intent of the Fiscal Year 2014 Orthotics and Prosthetics Outcomes Research Program award mechanism, the goal of the proposed research is to provide outcomes data to inform and improve the care of military Service members with lower extremity amputation(s). This will be accomplished by translating single photon emission tomography (SPECT)/X-ray computed tomography (CT) (SPECT/CT) imaging to non-invasively assess which prosthetic socket technologies will generate the best patient outcomes (i.e., residual limb health) for Service members with limb loss. As such, the proposed study leverages prior and current Department of Defense (DoD) investments by providing justification for prescribing only those prosthetic socket technologies most effective at promoting the overall health/tissue viability of the residual limb.Objective/ Hypothesis: The objective of the proposed study is to translate SPECT/CT imaging to patients with lower extremity amputation and subsequently evaluate the utility of non-invasive imaging for evaluating the impact of next-generation socket technologies on the health of the residual limb. It is hypothesized that SPECT/CT imaging will provide a highly sensitive, non-invasive tool for clinicians to assess changes in microvascular perfusion elicited by next-generation prosthetic socket technologies and that acute changes in microvascular perfusion will be predictive of long-term residual limb health outcomes.Specific Aim 1: To quantify basal microvascular perfusion and perfusion reserve of the residual limb in patients with lower extremity amputation using 99mTc-sestamibi SPECT/CT imaging. Specific Aim 2: To evaluate the efficacy of next-generation prosthetic socket technologies at promoting tissue health of the residual limb of patients with lower extremity amputation using 99mTc-sestamibi SPECT/CT imaging.Study Design: Participants with lower extremity amputations, both transtibial and transfemoral, will be recruited to Walter Reed National Military Medical Center for this study. Upon enrollment, subjects will undergo initial SPECT/CT imaging using a standard clinical imaging protocol. Briefly, patients will receive a low dose radiotracer injection (~8 mCi 99mTc-sestamibi) and will be imaged using a conventional hybrid SPECT/CT imaging system with large field of view sodium iodide detectors. Images will be acquired at the level of amputation in the residual limb. Participants will then be fitted with a socket technology that purports beneficial effects on residual limb health (e.g., VASS [vacuum-assisted suspension system], breathable socket). Participants will be re-evaluated via the aforementioned imaging protocol following 3 months of use of new socket technology. All SPECT images will be reconstructed using iterative reconstruction applying corrections for attenuation, scatter, and resolution loss. SPECT images will be reconstructed using system software, which is capable of generating co-registered functional (SPECT) and anatomical (CT) maps of the lower extremities. CT images will be used to define individual muscle groups in the lower extremities. Average SPECT activity within each CT-defined muscle group will be expressed as a percentage of the injected radiotracer dose per volume of muscle. SPECT/CT images will be quantified using validated image analysis tools.Military Benefit: Completion of the proposed study will greatly benefit patient care by providing a highly sensitive, non-invasive tool for clinicians and researchers to use for assessing the tissue health of the residual limb in patients with lower extremity amputations, both in the acute setting following a surgical intervention and chronically, to evaluate next-generation prosthetic socket technologies. As such, results from the proposed study could significantly reduce cost and burden to the DoD and Department of Veterans Affairs systems by providing justification towards the prescription of only those prosthetic socket technologies most effective at promoting the overall health/tissue viability of the residual limb.