RT Journal Article SR Electronic T1 Quantification of hand blood flow by Rubidium-82 positron emission tomography JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 3385 OP 3385 VO 63 IS supplement 2 A1 Feher, Attila A1 Papademetris, Xenophon A1 Sumpio, Bauer A1 Burg, Matthew A1 Albert, Sinusas A1 Hinchcliff, Monique A1 Miller, Edward YR 2022 UL http://jnm.snmjournals.org/content/63/supplement_2/3385.abstract AB 3385 Introduction: Patients with systemic sclerosis (SSc) are at high risk for developing digital ischemia with associated digital ulcerations and digital amputations. Current treatment options for digital ulcers are limited and include vasodilators, pain control and life style modifications. Currently, the development of effective therapies is limited by the lack of sensitive biomarkers which could be used for monitoring disease activity. We sought to develop a technique for the quantification of hand blood flow by dynamic Rubidium-82 (Rb-82) positron emission tomography (PET). Methods: We evaluated blood flow quantification in 7 healthy participants without autoimmune rheumatic conditions and without Raynaud’s phenomenon (n=5 female, age: 28 ± 10 years, BMI: 25.3 ± 2.5 kg/m2). The participants avoided food and caffeine for 4 hours prior to the study. Intravenous access was established on the left upper extremity for radioisotope injection. Dynamic Rb-82 PET imaging was performed on a hybrid PET/CT equipped with a 64-slice CT (GE Discovery 690). The right hand was positioned above the left side of the chest (Position 1) approximately 20-30 mm above the level of the chest to avoid scatter from the body. Following a scout image, a low-energy CT (120 kVp, 13 mA) was acquired for attenuation correction. Dynamic rest PET imaging was performed after intravenous injection of 20 ± 2 mCi of Rb-82. Twenty-seven dynamic frames were acquired in list mode with the following time sequences: 14 × 5-s frames; 6 × 10-s frames; 3 × 20-s frames; 3 × 30-s frames; and 1 × 90-s frame. Reproducibility was evaluated by obtaining another set of images (with separate attenuation CT) after repositioning the right hand to the right side of the chest (Position 2). Dynamic PET images were also acquired in 3 participants in the presence of reactive hyperemia performed by a 5-minute upper arm cuff occlusion by inflating a blood pressure cuff on the upper arm to 50 mmHg higher than the participant’s systolic blood pressure. The cuff was released after 5 minutes and Rb-82 was delivered 1 minute after cuff release corresponding to peak hyperemia. Reconstructed dynamic images were analyzed using Carimas (Turku, Finland). Hand segmentation was performed by using the superimposed attenuation CT images manually contouring the soft tissue of the hands with avoiding bony structures. Background contours were drawn randomly at areas free of body structures approximately the same distance from surface of the chest (20-30 mm). Rest and peak hyperemic k1 values were estimated by fitting the Rb-82 time-activity curves to a single-compartment tracer kinetic model by using the left ventricle as input function. Pearson correlation was used to evaluate correlation between resting k1 values. Hyperemic k1 values were compared to resting k1 values (average of position 1 and 2) by a paired t test.Results: Rb-82 injection imaging revealed hand radiotracer uptake which was substantially higher than background activity (Figure 1A). The one-compartment model described Rb-82 kinetics very well (median R2 = 0.94). Repeat imaging yielded similar k1 values at the two different hand positions (Rest position 1: 0.015 ± 0.008 mL/min/mL, Rest position 2: 0.016 ± 0.009 mL/min/mL, p = 0.17), with excellent correlation between resting k1 values obtained at position 1 and position 2 (Figure 1B, r2 = 0.90, p=0.001). Reactive hyperemia resulted in a significant increase in k1 in the limited number of evaluated participants (Figure 1C, hyperemia: 0.028 ± 0.004 mL/min/mL versus rest: 0.012 ± 0.005 mL/min/mL, p=0.02).Conclusions: Quantification of hand blood flow is feasible with dynamic Rb-82 PET and can detect changes in response to reactive hyperemia. Further studies are required to evaluate whether hand blood flow quantification by Rb-82 PET can serve as a novel imaging marker to guide prevention and to monitor effectiveness of therapy for digital ulcers in patients with SSc.