Prevalence and significance of extracardiac uptake on pyrophosphate imaging in the SCAN-MP study: the first 379 cases.

INTRODUCTION: Technetium-labeled bone-avid radiotracers can be used to diagnose transthyretin cardiac amyloidosis (ATTR-CA). Extracardiac uptake of technetium pyrophosphate (Tc-99m PYP) in this context has not been extensively explored and its significance is not well characterized. We assessed extracardiac Tc-99m PYP uptake in individuals undergoing nuclear scintigraphy and the extent of clinically actionable findings. METHODS: The Screening for Cardiac Amyloidosis with Nuclear Imaging in Minority Populations (SCAN-MP) study utilizes Tc-99m PYP imaging to identify ATTR-CA in self-identified Black and Caribbean Hispanic participants ≥ 60 years old with heart failure. We characterized the distribution of extracardiac uptake, including stratification of findings by timing of scan (1 hour vs 3 hours after Tc-99m PYP administration) and noted any additional testing in these subjects. RESULTS: Of 379 participants, 195 (51%) were male, 306 (81%) Black race, and 120 (32%) Hispanic ethnicity; mean age was 73 years. Extracardiac Tc-99m PYP uptake was found in 42 subjects (11.1%): 21 with renal uptake only, 14 with bone uptake only, 4 with both renal and bone uptake, 2 with breast uptake, and 1 with thyroid uptake. Extracardiac uptake was more common in subjects with Tc-99m PYP scans at 1 hour (23.8%) than at 3 hours (6.2%). Overall, four individuals (1.1%) had clinically actionable findings. CONCLUSION: Extracardiac Tc-99m PYP uptake manifested in about 1 in 9 SCAN-MP subjects but was clinically actionable in only 1.1% of cases.

Diagnostic performance characteristics of planar quantitative and semi-quantitative parameters of Tc99m pyrophosphate (PYP) imaging for diagnosis of transthyretin (ATTR) cardiac amyloidosis: the SCAN-MP study.

BACKGROUND: The optimal heart-to-contralateral chest (H/CL) ratio threshold for non-invasive diagnosis of transthyretin cardiac amyloidosis (ATTR-CA) using Tc99m pyrophosphate (PYP) imaging in a population with low pretest probability is not known. METHODS: Using myocardial PYP retention by SPECT as the reference standard, we evaluated the diagnostic performance of different semi-quantitative and quantitative (H/CL chest ratio) planar parameters obtained from 3-hour PYP imaging in a prospectively recruited cohort of minority older adults with heart failure and increased LV wall thickness. RESULTS: Of 229 patients, 14 were found to have ATTR-CA (6.1%). No PYP uptake (grade 0) was observed in 77% of scans, all grade 3 scans were ATTR-CA, and only 4 of 11 (36%) grade 2 scans were ATTR-CA. An H/CL threshold of ≥ 1.4 maximized specificity (99%) and positive predictive value (93%) but resulted in decreased sensitivity (93%), compared to the ≥ 1.3 threshold which had 100% sensitivity. CONCLUSION: Among patients with a low pretest likelihood of ATTR-CA, planar interpretation, while useful to exclude disease, must be interpreted with caution. H/CL ratio threshold of ≥ 1.3 resulted in clinically important misclassifications. These data suggest that quantitative planar imaging thresholds may not be appropriate to apply in low pretest likelihood populations being evaluated for ATTR-CA.

Blocking RAGE expression after injury reduces inflammation in mouse model of acute lung injury.

BACKGROUND: Receptor for Advanced Glycated Endproducts (RAGE) plays a major role in the inflammatory response to infectious and toxin induced acute lung injury. We tested the hypothesis that a RAGE blocking antibody when administered after the onset of injury can reduce lung inflammation compared to control antibody. METHODS: Male and female C57BL/6 (WT) mice were used. Forty-six received lipopolysaccharide (LPS) and 26 PBS by nasal instillation on day one, repeated on day three. On day 2, 36 mice receiving LPS were divided into two groups of 18, one treated with 200 µg of non-immune isotype control IgG and the second group treated with 200 µg of anti-RAGE Ab, each dose divided between IV and IP. Ten of the 46 were not treated. On day 4, before euthanasia, mice were injected with fluorescein isothiocyanate (FITC) labelled albumen. BALF and serum samples were collected as well as lung tissue for immunohistochemistry (IHC). BALF was analyzed for cell (leukocyte) counts, for FITC BALF/serum ratios indicating pulmonary vascular leak, and for cytokines/chemokines using bead based multiplex assays. Quantitative IHC was performed for MPO and RAGE. RESULTS: Ten LPS mice showed minimal inflammation by all measures indicating poor delivery of LPS and were excluded from analysis leaving n = 11 in the LPS + IgG group and n = 12 in the LPS + anti-RAGE group. BALF cell counts were low in the PBS administered mice (4.9 ± 2.1 × 105/ml) and high in the LPS injured untreated mice (109 ± 34) and in the LPS + IgG mice (91 ± 54) while in comparison, LPS + anti-RAGE ab mice counts were significantly lower (51.3 ± 18 vs. LPS + IgG, P = 0.03). The BALF/serum FITC ratios were lower for the LPS + anti-RAGE mice than for the LPS + IgG mice indicating less capillary leakiness. Quantitative IHC RAGE staining was lower in the LPS + anti-RAGE ab mice than in the LPS + IgG treated mice (P = 0.02). CONCLUSIONS: These results describe a four-day LPS protocol to sustain lung injury and allow for treatment and suggests that treatment aimed at blocking RAGE when given after onset of injury can reduce lung inflammation.

Blocking RAGE improves wound healing in diabetic pigs.

Receptor for Advanced Glycated End-products (RAGE) is highly expressed in diabetes and impairs wound healing. We proposed that administering an antibody that blocks RAGE will hasten the healing of dorsal wounds in diabetic pigs compared with a non-immune IgG. Two purpose-bred diabetic (D) Yucatan minipigs (Sinclair, Auxvasse MO) each underwent 12 2 × 2 cm full thickness dorsal wounds: four wounds received decellularized porcine skin patches (Xylyx Bio, Bklyn NY): four anti-RAGE Ab (CR-3) infused patches, four saline infused patches and four wounds were left open. One pig received anti-RAGE Ab (CR-3) 1 mg/kg IM q 10 days and other received non-immune IgG. Wounds were measured at 2 and 4 weeks followed by euthanasia and wound harvesting. At 2 weeks few of the patches appeared to be incorporated into the wound. By 4 weeks all patches in pigs treated systemically with CR-3 were detached and the wounds almost healed. For all 24 wounds for both pigs regardless of presence of patch or type of patch, the average IgG treated pig wound size at 4 weeks was 69.2 ± 14.6% of initial size and the average CR-3 treated pig wound size was 40.9 ± 11.3% of initial size (P = 0.0002). Quantitative immunohistology showed greater staining for collagen in the CR-3 treated wounds compared with IgG treated. Staining was positive for RAGE, Mac, and IL-6 in the IgG treated wounds and negative in the CR-3 treated wounds. From these pilot experiments, we conclude that a RAGE blocking antibody given parenterally improved wound healing in a diabetic pig while patches were not effective.

Noninvasive Physiologic Assessment of Cardiac Allograft Vasculopathy Is Prognostic for Post-Transplant Events.

BACKGROUND: Cardiac allograft vasculopathy (CAV) causes impaired blood flow in both epicardial coronary arteries and the microvasculature. A leading cause of post-transplant mortality, CAV affects 50% of heart transplant recipients within 10 years of heart transplant. OBJECTIVES: This analysis examined the outcomes of heart transplant recipients with reduced myocardial blood flow reserve (MBFR) and microvascular CAV detected by 13N-ammonia positron emission tomography (PET) myocardial perfusion imaging. METHODS: A total of 181 heart transplant recipients who underwent PET to assess for CAV were included with a median follow-up of 4.7 years. Patients were classified into 2 groups according to the total MBFR: >2.0 and ≤2.0. Microvascular CAV was defined as no epicardial CAV detected by PET and/or coronary angiography, but with an MBFR ≤2.0 by PET. RESULTS: In total, 71 (39%) patients had an MBFR ≤2.0. Patients with an MBFR ≤2.0 experienced an increased risk for all outcomes: 7-fold increase in death or retransplantation (HR: 7.05; 95% CI: 3.2-15.6; P < 0.0001), 12-fold increase in cardiovascular death (HR: 12.0; 95% CI: 2.64-54.12; P = 0.001), and 10-fold increase in cardiovascular hospitalization (HR: 10.1; 95% CI: 3.43-29.9; P < 0.0001). The 5-year mean survival was 302 days less than those with an MBFR >2.0 (95% CI: 260.2-345.4 days; P < 0.0001). Microvascular CAV (adjusted HR: 3.86; 95% CI: 1.58-9.40; P = 0.003) was independently associated with an increased risk of death or retransplantation. CONCLUSIONS: Abnormal myocardial blood flow reserve, even in the absence of epicardial CAV, identifies patients at a high risk of death or retransplantation. Measures of myocardial blood flow provide prognostic information in addition to traditional CAV assessment.

Novel Receptor for Advanced Glycation End Products-Blocking Antibody to Treat Diabetic Peripheral Artery Disease.

Background Expression of receptor for advanced glycation end products (RAGE) plays an important role in diabetic peripheral artery disease. We proposed to show that treatment with an antibody blocking RAGE would improve hind limb perfusion and muscle viability in diabetic pig with femoral artery (FA) ligation. Methods and Results Purpose-bred diabetic Yucatan minipigs with average fasting blood sugar of 357 mg/dL on insulin to maintain a glucose range of 300 to 500 mg/dL were treated with either a humanized monoclonal anti-RAGE antibody (CR-3) or nonimmune IgG. All pigs underwent intravascular occlusion of the anterior FA. Animals underwent (201Tl) single-photon emission computed tomography/x-ray computed tomography imaging on days 1 and 28 after FA occlusion, angiogenesis imaging with [99mTc]dodecane tetra-acetic acid-polyethylene glycol-single chain vascular endothelial growth factor (scVEGF), muscle biopsies on day 7, and contrast angiogram day 28. Results showed greater increases in perfusion to the gastrocnemius from day 1 to day 28 in CR-3 compared with IgG treated pigs (P=0.0024), greater uptake of [99mTc]dodecane tetra-acetic acid-polyethylene glycol-scVEGF (scV/Tc) in the proximal gastrocnemius at day 7, confirmed by tissue staining for capillaries and vascular endothelial growth factor A, and less muscle loss and fibrosis at day 28. Contrast angiograms showed better reconstitution of the distal FA from collaterals in the CR-3 versus IgG treated diabetic pigs (P=0.01). The gastrocnemius on nonoccluded limb at necropsy had higher 201Tl uptake (percentage injected dose per gram) and reduced RAGE staining in arterioles in CR-3 treated compared with IgG treated animals (P=0.04). Conclusions A novel RAGE-blocking antibody improved hind limb perfusion and angiogenesis in diabetic pigs with FA occlusion. Contributing factors are increased collaterals and reduced vascular RAGE expression. CR-3 shows promise for clinical treatment in diabetic peripheral artery disease.

Diagnosing Transthyretin Cardiac Amyloidosis by Technetium Tc 99m Pyrophosphate: A Test in Evolution.

OBJECTIVES: This study aimed to characterize trends in technetium Tc 99m pyrophosphate (99mTc-PYP) scanning for amyloid transthyretin cardiac amyloidosis (ATTR-CA) diagnosis, to determine whether patients underwent appropriate assessment with monoclonal protein and genetic testing, to evaluate use of single-photon emission computed tomography (SPECT) in addition to planar imaging, and to identify predictive factors for ATTR-CA. BACKGROUND: 99mTc-PYP scintigraphy has been repurposed for noninvasive diagnosis of ATTR-CA. Increasing use of 99mTc-PYP can facilitate identification of ATTR-CA, but appropriate use is critical for accurate diagnosis in an era of high-cost targeted therapeutics. METHODS: Patients undergoing 99mTc-PYP scanning 1 h after injection at a quaternary care center from 2010 to 2019 were analyzed; clinical information was abstracted; and SPECT results were analyzed. RESULTS: Over the decade, endomyocardial biopsy rates remained stable with scanning rates peaking at 132 in 2019 (p < 0.001). Among 753 patients (516 men, mean age 77 years), 307 (41%) had a visual score of 0, 177 (23%) of 1, and 269 (36%) of 2 or 3. Of 751 patients with analyzable heart to contralateral chest ratios, 249 (33%) had a ratio ≥1.5. Monoclonal protein testing status was assessed in 550 patients, of these, 174 (32%) did not undergo both serum immunofixation and serum free light chain analysis tests, and 331 (60%) did not undergo all 3 tests-serum immunofixation, serum free light chain analysis, and urine protein electrophoresis. Of 196 patients with confirmed ATTR-CA, 143 (73%) had genetic testing for transthyretin mutations. In 103 patients undergoing cardiac biopsy, grades 2 and 3 99mTc-PYP had sensitivity of 94% and specificity of 89% for ATTR-CA with 100% specificity for grade 3 scans. With respect to SPECT as a reference standard, planar imaging had false positive results in 16 of 25 (64%) grade 2 scans. CONCLUSIONS: Use of noninvasive testing with 99mTc-PYP scanning for evaluation of ATTR-CA is increasing, and the inclusion of monoclonal protein testing and SPECT imaging is crucial to rule out amyloid light chain amyloidosis and distinguish myocardial retention from blood pooling.

VEGF receptor targeted imaging of angiogenic response to limb ischemia in diabetic vs. non-diabetic Yucatan minipigs.

BACKGROUND: New therapies to treat diabetic peripheral artery disease (PAD) require target-specific non-invasive imaging modalities to follow efficacy. As a translational study, we performed targeted imaging of receptors for vascular endothelial growth factor (VEGF) in response to anterior femoral artery occlusion (FAO) in Yucatan minipigs and compare the normal response to response in diabetic Yucatan minipigs. METHODS: Eleven Yucatan minipigs, 6 non-diabetic (non-D) and 5 purpose bred diabetic (D) (Sinclair, Auxvasse MO), underwent intravascular total occlusion of the anterior femoral artery (FA). At days 1 and 28, pigs underwent SPECT/CT 201Tl hindlimb perfusion imaging and at day 7 were injected with [99mTc]DOTA-PEG-scVEGF (scV/Tc) tracer targeting VEGF receptor, and underwent biopsies of the hindlimb muscles for gamma counting and histology, followed by imaging. One day after the final scan, pigs underwent contrast angiography of the lower extremities. Counts from scans were converted to percentage injected activity (%IA). RESULTS: Perfusion was lower in the occluded hindlimb compared to non-occluded on day 1 in both the D and non-D pigs. At day 7, scV/Tc count ratio of counts from ROIs drawn in proximal gastrocnemius muscle for the occluded over non-occluded limb was significantly higher in non-D vs. D pigs (1.32 ± 0.06 vs. 1.04 ± 0.13, P = 0.02) reflecting higher level of angiogenesis. Perfusion increased between days 1 and 28 in the muscles in the occluded limb for the non-diabetic pigs while the diabetic pig showed no increase (+ 0.13 ± 0.08 %IA vs. - 0.13 ± 0.11, P = 0.003). The anterior FA showed poor contrast filling beyond occluder and qualitatively fewer bridging collaterals compared to non-D pigs at 28 days. CONCLUSION: VEGF receptor targeted imaging showed the effects of diabetes to suppress angiogenesis in response to occlusion of the anterior femoral artery of purpose bred diabetic Yucatan minipigs and indicates potential applicability as a marker to follow efficacy of novel therapies to improve blood flow by stimulating angiogenesis in diabetic PAD.

Single-photon emission computed tomography/computed tomography imaging of RAGE in smoking-induced lung injury.

BACKGROUND: Expression of the Receptor for Advanced Glycation Endproducts (RAGE) initiates pro-inflammatory pathways resulting in lung destruction. We hypothesized that RAGE directed imaging demonstrates increased lung uptake in smoke-exposure. METHODS: After exposure to room air or to cigarette smoke for 4-weeks or 16-weeks, rabbits were injected with 99mTc-anti-RAGE F(ab')2 and underwent Single-Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) imaging. Lung radiotracer uptake was calculated as percent injected dose (%ID). Lungs were dissected for gamma well counting and histological analysis. RESULTS: 99mTc-anti-RAGE F(ab')2 SPECT/CT imaging demonstrated increased lung expression of RAGE with smoke exposure compared to room air control at 4-weeks: Room air right (R) 0.75 ± 0.38%ID, left (L) 0.62 ± 0.32%ID vs. Smoke exposed R 0.17 ± 0.03, L 0.17 ± 0.02%ID (p = 0.02 and 0.028, respectively). By 16-weeks of smoke exposure, the uptake decreased to 0.19 ± 0.05%ID R and 0.17 ± 0.05%ID L, significantly lower than 4-week imaging (p = 0.0076 and 0.0129 respectively). Staining for RAGE confirmed SPECT results, with the RAGE ligand HMGB1 upregulated in the macrophages of 4-week smoke-exposed rabbits. CONCLUSIONS: RAGE-directed imaging identified pulmonary RAGE expression acutely in vivo in an animal model of emphysema early after smoke exposure, with diminution over time. These studies document the extent and time course of RAGE expression under smoke exposure conditions and could be utilized for disease monitoring and examining response to future RAGE-targeted therapies.

Imaging VEGF Receptors and αvß3 Integrins in a Mouse Hindlimb Ischemia Model of Peripheral Arterial Disease.

PURPOSE: To compare targeted imaging of vascular endothelial growth factor (VEGF) receptors vs. αvß3 integrins in a mouse hindlimb ischemia model of peripheral artery disease. PROCEDURES: Male wild-type (WT) C57BL/6 mice (8- to 10-week old) (n = 24) underwent left femoral artery ligation. The right leg served as control. Five days later, mice were injected with either VEGF receptor targeting [99mTc]DOTA-PEG-scVEGF ([99mTc]scV) (n = 8) or with αvß3-targeting tracer [99mTc]HYNIC-cycloRGD ([99mTc]RGD) (n = 8) and underwent single photon emission computed tomography (SPECT) x-ray computed tomography imaging. To assess non-specific [99mTc]scV uptake, six additional mice received a mixture of [99mTc]scV and 30-fold excess of targeting protein, scVEGF. Tracer uptake as %ID was measured using volumetric regions encompassing the hindlimb muscles and as %ID/g from harvested limb muscles. Double and triple immunofluorescent analysis on tissue sections established localization of αvß3, VEGFR-1, VEGFR-2, as well as certain cell lineage markers. RESULTS: Tracer uptake, as %ID/g, was higher in ligated limbs of mice injected with [99mTc]scV compared to ligated hindlimbs in mice injected with [99mTc]RGD (p = 0.02). The ratio of tracer uptake for ligated/control hindlimb was borderline higher for [99mTc]scV than for [99mTc]RGD (p = 0.06). Immunofluorescent analysis showed higher prevalence of VEGFR-1, VEGFR-2, and αvß3, in damaged vs. undamaged hindlimb tissue, but with little co-localization of these markers. Double immunofluorescent staining showed partial co-localization of VEGFR-1, VEGFR-2, and αvß3, with endothelial cell marker FVIII, but not with CD31. Immunostaining for VEGFR-1 and VEGFR-2 additionally co-localized with lineage markers for endothelial progenitor cell and monocytes/macrophages, with a more diverse pattern of co-localization for VEGFR-2. CONCLUSION: In a mouse hindlimb ischemia model of peripheral artery disease, [99mTc]scV SPECT tracer-targeting VEGF receptors showed a more robust signal than [99mTc]RGD tracer-targeting αvß3. Immunofluorescent analysis suggests that uptake of [99mTc]scV and [99mTc]RGD in damaged tissue is due to non-overlapping cell populations and reflects different dynamic processes and that enhanced uptake of [99mTc]scV may be due to the presence of VEGF receptors on additional cell types.

Selective Imaging of Vascular Endothelial Growth Factor Receptor-1 and Receptor-2 in Atherosclerotic Lesions in Diabetic and Non-diabetic ApoE-/- Mice.

PURPOSE: Plaque vulnerability is associated with inflammation and angiogenesis, processes that rely on vascular endothelial growth factor (VEGF) signaling via two receptors, VEGFR-1 and VEGFR-2. We have recently reported that enhanced uptake of scVEGF-PEG-DOTA/Tc-99m (scV/Tc) single photon emission computed tomography (SPECT) tracer that targets both VEGFR-1 and VEGFR-2, identifies accelerated atherosclerosis in diabetic relative to non-diabetic ApoE-/- mice. Since VEGFR-1 and VEGFR-2 may play different roles in atherosclerotic plaques, we reasoned that selective imaging of each receptor can provide more detailed information on plaque biology. PROCEDURES: Recently described VEGFR-1 and VEGFR-2 selective mutants of scVEGF, named scVR1 and scVR2, were site-specifically derivatized with Tc-99m chelator DOTA via 3.4 kDa PEG linker, and their selectivity to the cognate receptors was confirmed in vitro. scVR1 and scVR2 conjugates were radiolabeled with Tc-99m to specific activity of 110 ± 11 MBq/nmol, yielding tracers named scVR1/Tc and scVR2/Tc. 34-40 week old diabetic and age-matched non-diabetic ApoE-/- mice were injected with tracers, 2-3 h later injected with x-ray computed tomography (CT) contrast agent and underwent hybrid SPECT/CT imaging. Tracer uptake, localized to proximal aorta and brachiocephalic vessels, was quantified as %ID from. Tracer uptake was also quantified as %ID/g from gamma counting of harvested plaques. Harvested atherosclerotic arterial tissue was used for immunofluorescent analyses of VEGFR-1 and VEGFR-2 and various lineage-specific markers. RESULTS: Focal, receptor-mediated uptake in proximal aorta and brachiocephalic vessels was detected for both scVR1/Tc and scVR2/Tc tracers. Uptake of scVR1/Tc and scVR2/Tc was efficiently inhibited only by "cold" proteins of the same receptor selectivity. Tracer uptake in this area, expressed as %ID, was higher in diabetic vs. non- diabetic mice for scVR1/Tc (p = 0.01) but not for scVR2/Tc. Immunofluorescent analysis revealed enhanced VEGFR-1 prevalence in and around plaque area in diabetic mice. CONCLUSIONS: Selective VEGFR-1 and VEGFR-2 imaging of atherosclerotic lesions may be useful to explore plaque biology and identify vulnerability.

Single-Photon Emission Computed Tomography/Computed Tomography Imaging in a Rabbit Model of Emphysema Reveals Ongoing Apoptosis In Vivo.

Evaluation of lung disease is limited by the inability to visualize ongoing pathological processes. Molecular imaging that targets cellular processes related to disease pathogenesis has the potential to assess disease activity over time to allow intervention before lung destruction. Because apoptosis is a critical component of lung damage in emphysema, a functional imaging approach was taken to determine if targeting apoptosis in a smoke exposure model would allow the quantification of early lung damage in vivo. Rabbits were exposed to cigarette smoke for 4 or 16 weeks and underwent single-photon emission computed tomography/computed tomography scanning using technetium-99m-rhAnnexin V-128. Imaging results were correlated with ex vivo tissue analysis to validate the presence of lung destruction and apoptosis. Lung computed tomography scans of long-term smoke-exposed rabbits exhibit anatomical similarities to human emphysema, with increased lung volumes compared with controls. Morphometry on lung tissue confirmed increased mean linear intercept and destructive index at 16 weeks of smoke exposure and compliance measurements documented physiological changes of emphysema. Tissue and lavage analysis displayed the hallmarks of smoke exposure, including increased tissue cellularity and protease activity. Technetium-99m-rhAnnexin V-128 single-photon emission computed tomography signal was increased after smoke exposure at 4 and 16 weeks, with confirmation of increased apoptosis through terminal deoxynucleotidyl transferase dUTP nick end labeling staining and increased tissue neutral sphingomyelinase activity in the tissue. These studies not only describe a novel emphysema model for use with future therapeutic applications, but, most importantly, also characterize a promising imaging modality that identifies ongoing destructive cellular processes within the lung.

Treatment effect with anti-RAGE F(ab')2 antibody improves hind limb angiogenesis and blood flow in Type 1 diabetic mice with left femoral artery ligation.

We investigated treatment with a receptor for advanced glycation endproduct (RAGE) blocking antibody on angiogenic response to hind limb ischemia in diabetic mice. Streptozotocin treated C57BL/6 mice received either murine monoclonal anti-RAGE F(ab')2 intraperitoneally (n=10) or saline (n=9) for 9 weeks. Diabetic plus 10 non-diabetic C57BL/6 mice underwent left femoral artery ligation and 5 days later angiogenesis imaging with (99m)Tc-Arg-Gly-Asp (RGD) nanoSPECT/CT. Twenty-four days later, hind limb blood flow was measured with ultrasound, the mice were euthanized, and tissue was taken for immunohistochemistry. The angiogenic imaging signal in ischemic limbs was higher in RAGE-ab treated versus saline treated mice at day 5 (3.1±1.4 vs 1.68±0.35, p=0.02) and blood flow was higher at day 24 (1.49±0.5 vs 0.61±0.39, p=0.04). Immunohistochemistry of ischemic muscles showed greater capillary density in the RAGE-ab treated group versus the vehicle-treated group (p<0.001) (NS from non-diabetic mice). In conclusion, treatment with anti-RAGE F(ab')2 in diabetic mice improves neovascularization in the ischemic leg.

Radiation dose and prognosis of ultra-low-dose stress-first myocardial perfusion SPECT in patients with chest pain using a high-efficiency camera.

UNLABELLED: Although SPECT myocardial perfusion imaging (MPI) provides valuable information about patients with chest pain, there is growing concern regarding its radiation burden and lengthy duration. New high-efficiency (HE) cameras and stress-first protocols both offer the potential to markedly reduce radiation. No previous study has assessed outcomes and radiation doses of patients undergoing MPI on an HE-SPECT camera using an ultra-low-dose stress-first protocol. METHODS: One hundred patients presenting to the emergency department with chest pain who were candidates for stress-first MPI underwent injection of approximately 185 MBq (5 mCi) of (99m)Tc-tetrofosmin at peak stress, followed by supine and prone imaging on an HE-SPECT camera. Same-day rest imaging was performed on patients with any abnormality on imaging after stress. Radiation effective dose was calculated from administered and residual activities. Patients were contacted 3 mo after discharge, and electronic records were accessed to evaluate the need for reevaluation for chest pain, additional imaging, or cardiac events. RESULTS: Stress-only imaging was performed in 69 patients, for whom radiation effective dose averaged 0.99 mSv and study duration, 117 min. Radiation dose averaged 2.22 mSv over all patients. At 3 mo, 96 patients were free of major adverse cardiac events, repeat hospital chest pain evaluation, and repeat imaging or stress testing. One year after MPI and hospital discharge, all patients were living and without acute coronary syndrome. CONCLUSION: HE-SPECT stress-only imaging can be performed in more than two thirds of chest pain patients without a high pretest probability of a stress perfusion defect, with excellent prognosis, a radiation dose averaging 1 mSv, and a test duration of less than 2 h.

Imaging RAGE expression in atherosclerotic plaques in hyperlipidemic pigs.

BACKGROUND: Receptor for advanced glycated end product (RAGE) expression is a prominent feature of atherosclerosis. We have previously shown in apoE null mice uptake of a radiolabeled anti-RAGE antibody in atherosclerotic plaque and now evaluate RAGE-directed imaging to identify advanced plaques in a large animal model. METHODS: Nine hyperlipidemic (HL) pigs were injected with 603.1 ± 129.5 MBq of (99m)Tc-anti-RAGE F(ab')2, and after 6 h (blood pool clearance), they underwent single-photon emission computed tomography/computed tomography (SPECT/CT) imaging of the neck, thorax, and hind limbs. Two HL pigs received (99m)Tc non-immune IgG F(ab')2, and three farm pigs were injected with (99m)Tc-anti-RAGE F(ab')2. After imaging, the pigs were euthanized. The aorta from the root to bifurcation was dissected, and the innominates, proximal carotids, and coronaries were dissected and counted, stained for H&E and RAGE, and AHA-classified. RESULTS: On pathology, 24% of the arterial segments showed AHA class III or IV lesions, and these lesions were confined almost exclusively to coronaries and carotids with % stenosis from 15% to 65%. Scatter plots of %ID/g for class III/IV vs. I/II lesions showed almost complete separation. Focal vascular uptake of tracer visualized on SPECT scans corresponded to class III/IV lesions in the coronary and carotid vessels. In addition, uptake in the hind limbs was noted in the HL pigs and corresponded to RAGE staining of small arteries in the muscle sections. Correlations for the vascular lesions were r = 0.747, P = 0.001 for %ID vs. %ID/g and r = 0.83, P = 0.002 for %ID/g vs. % RAGE staining. CONCLUSIONS: Uptake of radiolabeled anti-RAGE antibody in coronary and carotid fibroatheroma and in the small arteries of the hind limbs in a relevant large animal model of atherosclerosis supports the important role of RAGE in atherosclerosis and peripheral artery disease as a target for imaging and treatment.

Beneficial Effect of Glucose Control on Atherosclerosis Progression in Diabetic ApoE(-/-) Mice: Shown by Rage Directed Imaging.

Objective. Receptor for advanced glycated endproducts (RAGE) plays an important role in atherogenesis in diabetes. We imaged RAGE to investigate the effect of glucose control to suppress RAGE and reduce atherosclerosis in apolipoprotein E null (apoE(-/-)) diabetic mice. Methods and Results. Thirty-three apoE(-/-) mice received streptozotocin and 6 weeks later 15 began treatment with insulin implants. Blood glucose measurements during study averaged: 140 ± 23 mg/dL (treated) and 354 ± 14 mg/dL (untreated). After 15 wk 30 mice were injected with (99m)Tc-anti-RAGE F(ab')2, 3 with (99m)Tc-nonimmune IgG F(ab')2, and all with CT contrast agent and underwent SPECT/CT imaging. At necropsy, the proximal aorta was weighed, counted, and sectioned and the % injected dose per gram (%ID/g) was calculated. From the merged SPECT/CT scans, tracer uptake localized to arteries was lower in the treated mice: 3.15 ± 1.82 × 10(-3) versus 8.69 ± 4.58 × 10(-3)%ID (P = 0.001). Percent cross-sectional lesion area was smaller in the treated (14.3 ± 7.8% versus 29.5 ± 10.9%) (P = 0.03). RAGE uptake on scans (%ID) correlated with quantitative RAGE staining in the atheroma and with %ID/g (R = 0.6887; P = 0.01). Lesion size as percent cross-sectional area was smaller in the treated (14.3 ± 7.8% versus 29.5 ± 10.9%) (P = 0.03). RAGE uptake on scans (%ID) correlated with quantitative RAGE staining in the atheroma and with %ID/g (R = 0.6887; P = 0.01). Conclusions. These results support the importance of suppressing RAGE to reduce atherosclerotic complications of diabetes and value of molecular imaging to assess treatment effect.