***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: AIM To assess the calcification process of the carotid plaque by (18)F-sodium fluoride PET/CT imaging . MATERIAL AND METHODS A prospect ively design ed study including 15 patients in whom an atheroma plaque was detected by contrast enhanced CT scan during a neurological work-up was performed . A total of 29 plaques , 19 asymptomatic and 10 symptomatic , were studied . An (18)F-sodium fluoride PET/CT scan was acquired 180min after the i.v . injection of 370 MBq of (18)F-sodium fluoride in all the patients . The images obtained were analyzed visually according to the intensity of the uptake . RESULTS All the plaques showed (18)F-sodium fluoride uptake , regardless of the intensity . However , the plaques of the symptomatic group showed a level of 2 or greater intensity while the intensity in 6 of the 19 in the asymptomatic group was lower than 2 . CONCLUSIONS Although the study is limited by the small number of cases , the results show the feasibility of the technique to study the calcification of the atheroma using (18)F-sodium fluoride and suggest an association between symptomatology and higher uptake of (18)F-sodium fluoride . Thus , these results encourage us to continue this study , with the inclusion of a larger number of patients Background — The pathophysiology of aortic stenosis is incompletely understood , and the relative contributions of valvular calcification and inflammation to disease progression are unknown . Methods and Results — Patients with aortic sclerosis and mild , moderate , and severe stenosis were compared prospect ively with age- and sex-matched control subjects . Aortic valve severity was determined by echocardiography . Calcification and inflammation in the aortic valve were assessed by 18F-sodium fluoride ( 18F-NaF ) and 18F-fluorodeoxyglucose ( 18F-FDG ) uptake with the use of positron emission tomography .  One hundred twenty-one subjects ( 20 controls ; 20 aortic sclerosis ; 25 mild , 33 moderate , and 23 severe aortic stenosis ) were administered both 18F-NaF and 18F-FDG . Quantification of tracer uptake within the valve demonstrated excellent interobserver repeatability with no fixed or proportional biases and limits of agreement of ±0.21 ( 18F-NaF ) and ±0.13 ( 18F-FDG ) for maximum tissue-to- background ratios . Activity of both tracers was higher in patients with aortic stenosis than in control subjects ( 18F-NaF : 2.87±0.82 versus 1.55±0.17 ; 18F-FDG : 1.58±0.21 versus 1.30±0.13 ; both P<0.001 ) . 18F-NaF uptake displayed a progressive rise with valve severity ( r2=0.540 , P<0.001 ) , with a more modest increase observed for 18F-FDG ( r2=0.218 , P<0.001 ) . Among patients with aortic stenosis , 91 % had increased 18F-NaF uptake ( > 1.97 ) , and 35 % had increased 18F-FDG uptake ( > 1.63 ) . A weak correlation between the activities of these tracers was observed ( r2=0.174 , P<0.001 ) . Conclusions — Positron emission tomography is a novel , feasible , and repeatable approach to the evaluation of valvular calcification and inflammation in patients with aortic stenosis . The frequency and magnitude of increased tracer activity correlate with disease severity and are strongest for 18F-NaF. Clinical Trial Registration — http://www . clinical trials.gov . Unique identifier : NCT01358513 BACKGROUND The use of non-invasive imaging to identify ruptured or high-risk coronary atherosclerotic plaques would represent a major clinical advance for prevention and treatment of coronary artery disease . We used combined PET and CT to identify ruptured and high-risk atherosclerotic plaques using the radioactive tracers (18)F-sodium fluoride ( (18)F-NaF ) and (18)F-fluorodeoxyglucose ( (18)F-FDG ) . METHODS In this prospect i ve clinical trial , patients with myocardial infa rct ion ( n=40 ) and stable angina ( n=40 ) underwent (18)F-NaF and (18)F-FDG PET-CT , and invasive coronary angiography . (18)F-NaF uptake was compared with histology in carotid endarterectomy specimens from patients with symptomatic carotid disease , and with intravascular ultrasound in patients with stable angina . The primary endpoint was the comparison of (18)F-fluoride tissue-to- background ratios of culprit and non-culprit coronary plaques of patients with acute myocardial infa rct ion . FINDINGS In 37 ( 93 % ) patients with myocardial infa rct ion , the highest coronary (18)F-NaF uptake was seen in the culprit plaque ( median maximum tissue-to- background ratio : culprit 1·66 [ IQR 1·40 - 2·25 ] vs highest non-culprit 1·24 [ 1·06 - 1·38 ] , p<0·0001 ) . By contrast , coronary (18)F-FDG uptake was commonly obscured by myocardial uptake and where discernible , there were no differences between culprit and non-culprit plaques ( 1·71 [ 1·40 - 2·13 ] vs 1·58 [ 1·28 - 2·01 ] , p=0·34 ) . Marked  (18)F-NaF uptake occurred at the site of all carotid plaque ruptures and was associated with histological evidence of active calcification , macrophage infiltration , apoptosis , and necrosis . 18 ( 45 % ) patients with stable angina had plaques with focal (18)F-NaF uptake ( maximum tissue-to- background ratio 1·90 [ IQR 1·61 - 2·17 ] ) that were associated with more high-risk features on intravascular ultrasound than those without uptake : positive remodelling ( remodelling index 1·12 [ 1·09 - 1·19 ] vs 1·01 [ 0·94 - 1·06 ] ; p=0·0004 ) , microcalcification ( 73 % vs 21 % , p=0·002 ) , and necrotic core ( 25 % [ 21 - 29 ] vs 18 % [ 14 - 22 ] , p=0·001 ) . INTERPRETATION (18)F-NaF PET-CT is the first non-invasive imaging method to identify and localise ruptured and high-risk coronary plaque . Future studies are needed to establish whether this method can improve the management and treatment of patients with coronary artery disease . FUNDING Chief Scientist Office Scotl and and British Heart Foundation The purpose of this study was to correlate 18F-sodium fluoride accumulation in the common carotid arteries of neurologically asymptomatic patients with cardiovascular risk factors and carotid calcified plaque burden . Methods : Two hundred sixty-nine oncologic patients were examined by 18F-sodium fluoride PET/CT .  Tracer accumulation in the common carotid arteries was analyzed both qualitatively and semiquantitatively by measuring the blood-pool – corrected st and ardized uptake value ( target-to- background ratio ) and comparing it with cardiovascular risk factors and calcified plaque burden . Results : 18F-sodium fluoride uptake was observed at 141 sites in 94 ( 34.9 % ) patients .  Radiotracer accumulation was colocalized with calcification in all atherosclerotic lesions .  18F-sodium fluoride uptake was significantly associated with age ( P < 0.0001 ) , male sex ( P < 0.0001 ) , hypertension ( P < 0.002 ) , and hypercholesterolemia ( P < 0.05 ) . The presence of calcified plaque correlated significantly with these risk factors but also with diabetes ( P < 0.0001 ) , history of smoking ( P = 0.03 ) , and prior cardiovascular events ( P < 0.01 ) . There was a highly significant correlation between the presence of 18F-sodium fluoride uptake and number of present cardiovascular risk factors ( r = 0.30 , P < 0.0001 ) . Conclusion : Carotid 18F-sodium fluoride uptake is a surrogate measure of calcifying carotid plaque , correlates with cardiovascular risk factors , and is more frequent in patients with a high-risk profile for atherothrombotic events but demonstrates a weaker correlation with risk factors than does calcified plaque burden . This study provides a rationale to conduct further prospect i ve studies to determine whether 18F-sodium fluoride uptake can predict vascular events , or if it may be used to monitor pharmacologic therapy Purpose Arterial inflammation and vascular calcification are regarded as early prognostic markers of cardiovascular disease ( CVD ) . In this study we investigated the relationship between CVD risk and arterial inflammation ( 18F-FDG PET/CT imaging ) , vascular calcification metabolism ( Na18F PET/CT imaging ) , and vascular calcium burden ( CT imaging ) of the thoracic aorta in a population at low CVD risk . Methods Study participants underwent blood pressure measurements , blood analyses , and 18F-FDG and Na18F PET/CT imaging . In addition , the 10-year risk for development of CVD , based on the Framingham risk score ( FRS ) , was estimated . CVD risk was compared across quartiles of thoracic aorta 18F-FDG uptake , Na18F uptake , and calcium burden on CT . Results A total of 139 subjects ( 52 % men , mean age 49 years , age range 21 – 75 years , median FRS 6 % ) were evaluated . CVD risk was , on average , 3.7 times higher among subjects with thoracic aorta Na18F uptake in the highest quartile compared with those in the lowest quartile of the distribution ( 15.5 % vs. 4.2 % ; P < 0.001 ) . CVD risk was on average , 3.7 times higher among subjects with a thoracic aorta calcium burden on CT in the highest quartile compared with those in the lowest two quartiles of the distribution ( 18.0 % vs. 4.9 % ; P < 0.001 ) . CVD risk was similar in subjects in all quartiles of thoracic aorta 18F-FDG uptake . Conclusion Our findings indicate that an unfavourable CVD risk profile is associated with marked increases in vascular calcification metabolism and vascular calcium burden of the thoracic aorta , but not with arterial inflammation Background — 18F-sodium fluoride ( 18F-NaF ) positron-emission tomography has been introduced as a potential noninvasive imaging tool to identify plaques with high-risk characteristics in patients with coronary artery disease . We sought to evaluate the clinical relevance of 18F-NaF uptake using optical coherence tomography ( OCT ) , intravascular ultrasound ( IVUS ) , and coronary computed tomography angiography in patients with coronary artery disease . Methods and Results — The target population consisted of 51 prospect ively enrolled patients ( 93 stenoses ) who underwent 18F-NaF positron-emission tomography before invasive coronary angiography . 18F-NaF uptake was compared with IVUS- and OCT-derived plaque characteristics . In the coronary computed tomography angiography subgroup ( 46 lesions ) , qualitative lesion characteristics were compared between 18F-NaF – positive and 18F-NaF – negative plaques using adverse plaque characteristics . The plaques with 18F-NaF uptake showed significantly higher plaque burden , more frequent posterior attenuation and positive remodeling in IVUS , and significantly higher maximum lipid arc and more frequent microvessels in OCT ( all P<0.05 ) . There were no differences in minimum lumen area and area of calcium between 18F-NaF – positive and 18F-NaF – negative lesions . Among 51 lesions with 18F-NaF – positive uptake , 48 lesions ( 94.1 % ) had at least one of high-risk characteristics . The 18F-NaF tissue-to- background ratio in plaques with high-risk characteristics was significantly higher than in those without ( 1.09 [ 95 % confidence interval , 0.85–1.34 ] versus 0.62 [ 95 % confidence interval , 0.42–0.82 ] , P<0.001 for IVUS definition ; 0.76 [ 95 % confidence interval , 0.54–0.98 ] versus 0 
    Output:
    
In atherosclerosis , most studies report a positive correlation with the burden of CV risk factors and vascular calcification .
A higher uptake was found in culprit plaques/rupture sites in coronary and carotid arteries and it was also linked to high-risk features in histology and intravascular imaging analysis of the plaques .
In aortic stenosis , this tracer displayed an increasing uptake with disease severity .
Sodium fluoride positron emission tomography is a promising non-invasive technique to identify high-risk plaques , which sets ground to a potential use of this tracer in evaluating atherosclerotic disease progression and degenerative changes in aortic valve stenosis .