Vessel-by-vessel analysis of lower extremity 18F-NaF PET/CT imaging quantifies diabetes- and chronic kidney disease-induced active microcalcification in patients with peripheral arterial disease

Quantification of Skeletal Muscle Perfusion in Peripheral Artery Disease Using 18F-Sodium Fluoride Positron Emission Tomography Imaging

BACKGROUND

Perfusion deficits contribute to symptom severity, morbidity, and death in peripheral artery disease (PAD); however, no standard method for quantifying absolute measures of skeletal muscle perfusion exists. This study sought to preclinically test and clinically translate a positron emission tomography (PET) imaging approach using an atherosclerosis-targeted radionuclide, fluorine-18-sodium fluoride (18F-NaF), to quantify absolute perfusion in PAD.

METHODS AND RESULTS

Eight Yorkshire pigs underwent unilateral femoral artery ligation and dynamic 18F-NaF PET/computed tomography imaging on the day of and 2 weeks after occlusion. Following 2-week imaging, calf muscles were harvested to quantify microvascular density. PET methodology was validated with microspheres in 4 additional pig studies and translated to patients with PAD (n=39) to quantify differences in calf perfusion across clinical symptoms/stages and perfusion responses in a case of revascularization. Associations between PET perfusion, ankle-brachial index, toe-brachial index, and toe pressure were assessed in relation to symptoms. 18F-NaF PET/computed tomography quantified significant deficits in calf perfusion in pigs following arterial occlusion and perfusion recovery 2 weeks after occlusion that coincided with increased muscle microvascular density. Additional studies confirmed that PET-derived perfusion measures agreed with microsphere-derived perfusion measures. Translation of imaging methods demonstrated significant decreases in calf perfusion with increasing severity of PAD and quantified perfusion responses to revascularization. Perfusion measures were also significantly associated with symptom severity, whereas traditional hemodynamic measures were not.

CONCLUSIONS

18F-NaF PET imaging quantifies perfusion deficits that correspond to clinical stages of PAD and represents a novel perfusion imaging strategy that could be partnered with atherosclerosis-targeted 18F-NaF PET imaging using a single radioisotope injection.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03622359.

PET Radiotracers in Atherosclerosis: A Review

Traditional atherosclerosis imaging modalities are limited to late stages of disease, prior to which patients are frequently asymptomatic. Positron emission tomography (PET) imaging allows for the visualization of metabolic processes underscoring disease progression via radioactive tracer, allowing earlier-stage disease to be identified. 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG) uptake largely reflects the metabolic activity of macrophages, but is unspecific and limited in its utility. By detecting areas of microcalcification, 18F-Sodium Fluoride (18F-NaF) uptake also provides insight into atherosclerosis pathogenesis. Gallium-68 DOTA-0-Tyr3-Octreotate (68Ga-DOTATATE) PET has also shown potential in identifying vulnerable atherosclerotic plaques with high somatostatin receptor expression. Finally, 11-carbon (11C)-choline and 18F-fluoromethylcholine (FMCH) tracers may identify high-risk atherosclerotic plaques by detecting increased choline metabolism. Together, these radiotracers quantify disease burden, assess treatment efficacy, and stratify risk for adverse cardiac events.

Anatomical Distribution Patterns of Peripheral Arterial Disease According to Patient Characteristics: A Unicentral Cohort Study

Purpose

Peripheral arterial disease (PAD) is a common disease with multiple risk factors and affects patients worldwide. Several international studies have established correlations between anatomical topography/distribution of atherosclerosis and comorbidities in patients with PAD. In this cohort study, we aimed to analyze the patterns of atherosclerosis (site, distribution, and degree) in patients who underwent lower limb computed tomography angiography and arterial angiography by identifying the atherosclerotic plaque(s) that were possibly responsible for thrombi. Additionally, we aimed to determine any relationship between comorbidities and identified patterns.

Patients and Methods

Between January 2015 and January 2021, we retrospectively recruited 140 patients at King Fahd Hospital of the University of Saudi Arabia. Data collected included patient characteristics, risk factors, and metabolic disorders, such as hypertension (HTN), diabetes mellitus (DM), dyslipidemia, and chronic kidney disease. Patients with incomplete records or unavailable radiological images were excluded.

Results

The infrapopliteal territory was the most common segment that was affected. HTN, DM, and dyslipidemia were found in 81.4%, 77.9%, and 62.9% of patients, respectively. Correlation analyses revealed that DM was the only independent metabolic disorder associated with a PAD distribution pattern in the femoropopliteal segment (p=0.039), thus denoting distal involvement. No significant association was found between PAD distribution and the severity of stenosis.

Conclusion

Segmental involvement in PAD varies with the risk factors and metabolic comorbidities present in patients. DM is an independent predictor of the anatomical distribution of PAD. The identification of such an anatomical distribution is paramount for screening procedures, early detection of disease, and prevention of complications, particularly limb amputation.

Detection of Multi-Vessel Calcific Disease Progression in a Patient with Chronic Limb-Threatening Ischemia Using 18F-Sodium Fluoride Positron Emission Tomography Imaging

Vascular calcification contributes to morbidity and poor clinical outcomes for patients with peripheral artery disease; however, the traditional assessment of the calcium burden using computed tomography (CT) imaging or angiography represents already established disease. In the present report, we describe a 69-year-old man with chronic limb-threatening ischemia who had undergone positron emission tomography/CT imaging with fluorine-18 sodium fluoride to evaluate the relationship between baseline levels of positron emission tomography-detectable active vascular microcalcification and CT-detectable calcium progression 1.5 years later. CT imaging at follow-up identified progression of existing lesions and the formation of new calcium in multiple arteries that had demonstrated elevated fluorine-18 sodium fluoride uptake 1.5 years earlier.