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OBJECTIVE: Altered joint function is a hallmark of osteoarthritis (OA). Imaging techniques for joint function are limited, but [18F]sodium fluoride (NaF) PET-MRI may assess the acute joint response to loading stresses. [18F]NaF PET-MRI was used to study the acute joint response to exercise in OA knees, and compare relationships between regions of increased uptake after loading and structural OA progression two years later. METHODS: In this prospective study, 10 participants with knee OA (59 ± 8 years; 8 female) were scanned twice consecutively using a PET-MR system and performed a one-legged squat exercise between scans. Changes in tracer uptake measures in 9 bone regions were compared between knees that did and did not exercise with a mixed-effects model. Areas of focally large changes in uptake between scans (ROIfocal, ΔSUVmax > 3) were identified and the presence of structural MRI features was noted. Five participants returned two years later to assess structural change on MRI. RESULTS: There was a significant increase in [18F]NaF uptake in OA exercised knees (SUV P < 0.001, KiP = 0.002, K1P < 0.001) that differed by bone region. CONCLUSION: There were regional differences in the acute bone metabolic response to exercise and areas of focally large changes in the metabolic bone response that might be representative of whole-joint dysfunction.

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OBJECTIVE: Molecular information derived from dynamic [18F]sodium fluoride ([18F]NaF) PET imaging holds promise as a quantitative marker of bone metabolism. The objective of this work was to evaluate physiological mechanisms of [18F]NaF uptake in subchondral bone of individuals with and without knee osteoarthritis (OA). METHODS: Eleven healthy volunteers and twenty OA subjects were included. Both knees of all subjects were scanned simultaneously using a 3T hybrid PET/MRI system. MRI MOAKS assessment was performed to score the presence and size of osteophytes, bone marrow lesions, and cartilage lesions. Subchondral bone kinetic parameters of bone perfusion (K1), tracer extraction fraction, and total tracer uptake into bone (Ki) were evaluated using the Hawkins 3-compartment model. Measures were compared between structurally normal-appearing bone regions and those with structural findings. RESULTS: Mean and maximum SUV and kinetic parameters Ki, K1, and extraction fraction were significantly different between Healthy subjects and subjects with OA. Between-group differences in metabolic parameters were observed both in regions where the OA group had degenerative changes as well as in regions that appeared structurally normal. CONCLUSIONS: Results suggest that bone metabolism is altered in OA subjects, including bone regions with and without structural findings, compared to healthy subjects. Kinetic parameters of [18F]NaF uptake in subchondral bone show potential to quantitatively evaluate the role of bone physiology in OA initiation and progression. Objective measures of bone metabolism from [18F]NaF PET imaging can complement assessments of structural abnormalities observed on MRI.

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PURPOSE: To assess reliability and clinical utility of evaluating stress-related metaphyseal water distribution using a semi-quantitative Dixon MRI-based method for early diagnosis of physeal stress injuries in adolescent gymnasts. METHODS: Twenty-four gymnasts with clinically suspected overuse injury of the distal radial physis, 18 asymptomatic gymnasts, and 24 non-gymnast controls aged 12 ± 1.5 years prospectively underwent hand radiographs and 3T MRI of the wrist including coronal T1-weighted and T2-weighted Dixon sequences. Two raters measured metaphyseal water signal fraction in 13 radial and ulnar regions of interest (ROI). Inter- and intrarater reliability, interslice (between 3 middle radial slices), and inter-ROI (between 3 ROIs on same level) reliability were assessed using intraclass correlation coefficients (ICC). Water signal fractions and their within-person ratios in distal versus most proximal ROIs were compared between groups using one-way analysis of variance. RESULTS: Inter- and intrarater ICCs were 0.79-0.99 and 0.94-1.0 for T1-weighted, and 0.88-1.0 and 0.88-1.0 for T2-weighted Dixon. Interslice and inter-ROI ICCs were 0.55-0.94 and 0.95-0.97 for T1-weighted, and 0.70-0.96 and 0.96-0.97 for T2-weighted Dixon. Metaphyseal water signal fraction in symptomatic gymnasts was higher in six distal ROIs compared with asymptomatic gymnasts and in nine ROIs compared with non-gymnasts (p < 0.05). Metaphyseal water score (ratio of distal versus most proximal ROIs) was 1.61 in symptomatic gymnasts and 1.35 in asymptomatic gymnasts on T2-weighted Dixon (p < 0.05). CONCLUSION: Semi-quantitative Dixon MRI-based water signal fraction assessment has good to excellent reproducibility and shows increased metaphyseal water scores in symptomatic gymnasts compared with asymptomatic gymnastic peers. KEY POINTS: • The proposed Dixon MRI-based semi-quantitative method for assessment of metaphyseal bone marrow water content is reliable, with off-the-shelf availability and short scan times. • The metaphyseal water score allows comparisons between gymnasts using a within-person reference area for unaffected metaphyseal bone. • As metaphyseal water score was increased in symptomatic gymnasts compared with asymptomatic gymnasts, this semi-quantitative method can potentially be used as an indicator of bone marrow edema in the early diagnosis of gymnastic physeal stress injury.

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BACKGROUND AND AIM: The capacity of the results of clinical studies to lead to changes in clinical practice is controversial. The treatment of elderly patients with acute myocardial infarction (AMI) represents an increasingly important challenge for the physician. The decreasing mortality rate for AMI in the general population is countered by an increasingly high mortality rate among the elderly. The aim of this prospective study was to evaluate the impact of the results of clinical studies on the treatment of AMI in community hospitals, and to highlight any differences in treatment and prognosis depending on age. MATERIALS AND METHODS: 123 patients with AMI were divided into two groups: (1) young patients (61.2%) aged under 75 (76 patients of whom 64 were male, with a mean age of 61.08 +/- 9.63) and (2) elderly patients (38.8%) aged over 75 (47 patients of whom 26 were male, with a mean age of 81.77 +/- 3.94). All patients were monitored for at least 12 months after discharge. RESULTS: The percentage administration of fibrinolytics (60.5%), aspirin (80.3%), beta-blockers (oral 40.8%; i.v. 32.9%) and anticoagulants (97.4%) showed that young patients were treated according to the indications reported in the literature. Thrombolysis was more frequently performed in young patients than in the aged (60.5% vs 10.6%; p = 0.0001). Multiple logistic regression analysis showed that age, Killip's class and time at hospitalization were variables predicting the exclusion from fibrinolysis. During hospitalization the elderly group received oral beta-blockers less frequently (8.5% vs 40.8%; p = 0.0001); on discharge, they less frequently received ACE-inhibitors (14.9% vs 46.1%; p = 0.0004), aspirin (48.9% vs 77.6%; p = 0.001), beta-blockers (12.8% vs 44.7%; p = 0.0002). The elderly group revealed a higher mortality rate both during hospitalization (19.1% vs 3.9%; p = 0.01) and follow-up (44.7% vs 11.0%; p = 0.0001). Multivariate analysis showed a direct correlation between ventricular arrhythmia and Killip's class and hospital mortality, whereas smoking and time at hospitalization were inversely correlated. Mortality during follow-up was directly associated with Killip's class and inversely to the use of ACE-inhibitors during hospitalization, and beta-blockers and diuretics on discharge. Kaplan-Meier analysis did not show any differences in the survival rate of the two groups, but the first year after AMI was particularly critical for elderly patients among whom 40% of all deaths were recorded. CONCLUSIONS: This study confirms the application in clinical practice of the results of clinical studies also in community hospitals, and shows that elderly AMI patients are high-risk patients. The high mortality in the latter group is correlated to the fact that they are less eligible to undergo fibrinolytic therapy and have a lower probability of receiving drugs of proven efficacy as a means of increasing survival after AMI. Further clinical studies are required to reduce mortality after AMI in a population that is increasingly widely represented in community hospitals.

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