Atherosclerosis Burdens in Diabetes Mellitus: Assessment by PET Imaging.

Arteriosclerosis and its sequelae are the most common cause of death in diabetic patients and one of the reasons why diabetes has entered the top 10 causes of death worldwide, fatalities having doubled since 2000. The literature in the field claims almost unanimously that arteriosclerosis is more frequent or develops more rapidly in diabetic than non-diabetic subjects, and that the disease is caused by arterial inflammation, the control of which should therefore be the goal of therapeutic efforts. These views are mostly based on indirect methodologies, including studies of artery wall thickness or stiffness, or on conventional CT-based imaging used to demonstrate tissue changes occurring late in the disease process. In contrast, imaging with positron emission tomography and computed tomography (PET/CT) applying the tracers 18F-fluorodeoxyglucose (FDG) or 18F-sodium fluoride (NaF) mirrors arterial wall inflammation and microcalcification, respectively, early in the course of the disease, potentially enabling in vivo insight into molecular processes. The present review provides an overview of the literature from the more than 20 and 10 years, respectively, that these two tracers have been used for the study of atherosclerosis, with emphasis on what new information they have provided in relation to diabetes and which questions remain insufficiently elucidated.

A critical review of radiotracers in the positron emission tomography imaging of traumatic brain injury: FDG, tau, and amyloid imaging in mild traumatic brain injury and chronic traumatic encephalopathy.

PURPOSE: Positron emission tomography (PET) has been widely utilized in the study of traumatic brain injury (TBI) for decades. While most applications of PET have attempted to assess neuronal function after TBI, more recently, novel radiotracers have sought to image biomarkers in the context of TBI and chronic traumatic encephalopathy (CTE). METHODS: This review will begin with an overview of TBI and CTE along with the acute and chronic pathophysiological consequences of TBI. Next, glycolysis, beta-amyloid, and tau protein radiotracers will be critically assessed in light of the most recent imaging studies available. CONCLUSIONS: Based on the scientific relevance of such radiotracers to the molecular processes of TBI and CTE along with the broader evidence of radiotracer specificity and selectivity, this review will weigh the strengths and weaknesses of each radiotracer. Nonetheless, the evidence indicates that PET will continue to be a powerful modality in the diagnosis of TBI-related conditions.

Quantitative thoracic aorta calcification assessment by 18F-NaF PET/CT and its correlation with atherosclerotic cardiovascular disorders and increasing age.

OBJECTIVES: We aimed to assess the correlation between age and cardiovascular risk factors with NaF-PET/CT imaging in the thoracic aorta (TA). METHODS: In this prospective study, 80 healthy controls and 44 patients with chest pain underwent NaF-PET/CT imaging, and three segments of the aorta (ascending, arch, and descending) were examined. Average SUVmax, SUVmean, and Alavi-Carlsen Score (ACS) were calculated in each segment and the entire vessel. The degree of NaF uptake in controls and patients and its correlation with age were determined. Multivariate linear regression and logistic regression models were employed to determine the predictabilities of Framingham Risk Score (FRS) and unfavorable cardiovascular disease (CVD) risk profile by these measurements. RESULTS: Average SUVmax, average SUVmean, and ACS were significantly higher in patients than in controls, and all correlated well with age. The correlation of average SUVmean with age was significant in both controls (r = 0.32, p = 0.04) and patients (r = 0.64, p < 0.001). ACS of the entire TA was a stronger predictor of FRS compared with average SUVmax and average SUVmean (adjusted R2 = 0.38, standardized ß = 0.58, p < 0.001). ACS was a significant predictor of unfavorable CVD risk profile as compared with other values (odds ratio = 1.006, 95% CI = 1.000-1.013, p = 0.05). CONCLUSIONS: Active calcification in TA correlates with age, and its correlation is higher among subjects with CVD risk factors. Global assessment (ACS) can predict unfavorable CVD risk profile. These data provide evidence for the potential role of NaF in assessing micro-calcification in arteries and its relations to cardiovascular events. KEY POINTS: • Global micro-calcification in the thoracic aorta as measured by NaF-PET/CT imaging correlates with increasing age. • The extent of the correlation was higher among patients with cardiovascular disease (CVD) risk factors. • These data provide evidence for the potential role of NaF in assessing active calcification in arteries and its relations to cardiovascular events.

Carotid artery molecular calcification assessed by [18F]fluoride PET/CT: correlation with cardiovascular and thromboembolic risk factors.

OBJECTIVES: There is growing evidence that sodium fluoride ([18F]fluoride) PET/CT can detect active arterial calcifications at the molecular stage. We investigated the relationship between arterial mineralization in the left common carotid artery (LCC) assessed by [18F]fluoride PET/CT and cardiovascular/thromboembolic risk. METHODS: In total, 128 subjects (mean age 48 ± 14 years, 51% males) were included. [18F]fluoride uptake in the LCC was quantitatively assessed by measuring the blood-pool-corrected maximum standardized uptake value (SUVmax) on each axial slice. Average SUVmax (aSUVmax) was calculated over all slices and correlated with 10-year risk of cardiovascular events estimated by the Framingham model, CHA2DS2-VASc score, and level of physical activity (LPA). RESULTS: The aSUVmax was significantly higher in patients with increased risk of cardiovascular (one-way ANOVA, p < 0.01) and thromboembolic (one-way ANOVA, p < 0.01) events, and it was significantly lower in patients with greater LPA (one-way ANOVA, p = 0.02). On multivariable linear regression analysis, age ( = 0.07, 95% CI 0.05 - 0.10, p < 0.01), body mass index ( = 0.02, 95% CI 0.01 - 0.03, p < 0.01), arterial hypertension ( = 0.15, 95% CI 0.08 - 0.23, p < 0.01), and LPA ( = -0.10, 95% CI -0.19 to -0.02, p=0.02) were independent associations of aSUVmax. CONCLUSIONS: Carotid [18F]fluoride uptake is significantly increased in patients with unfavorable cardiovascular and thromboembolic risk profiles. [18F]fluoride PET/CT could become a valuable tool to estimate subjects' risk of future cardiovascular events although still major trials are needed to further evaluate the associations found in this study and their potential clinical usefulness. KEY POINTS: • Sodium fluoride ([18F]fluoride) PET/CT imaging identifies patients with early-stage atherosclerosis. • Carotid [18F]fluoride uptake is significantly higher in patients with increased risk of cardiovascular and thromboembolic events and inversely correlated with the level of physical activity. • Early detection of arterial mineralization at a molecular level could help guide clinical decisions in the context of cardiovascular risk assessment.

18F-Sodium Fluoride PET as a Diagnostic Modality for Metabolic, Autoimmune, and Osteogenic Bone Disorders: Cellular Mechanisms and Clinical Applications.

In a healthy body, homeostatic actions of osteoclasts and osteoblasts maintain the integrity of the skeletal system. When cellular activities of osteoclasts and osteoblasts become abnormal, pathological bone conditions, such as osteoporosis, can occur. Traditional imaging modalities, such as radiographs, are insensitive to the early cellular changes that precede gross pathological findings, often leading to delayed disease diagnoses and suboptimal therapeutic strategies. 18F-sodium fluoride (18F-NaF)-positron emission tomography (PET) is an emerging imaging modality with the potential for early diagnosis and monitoring of bone diseases through the detection of subtle metabolic changes. Specifically, the dissociated 18F- is incorporated into hydroxyapatite, and its uptake reflects osteoblastic activity and bone perfusion, allowing for the quantification of bone turnover. While 18F-NaF-PET has traditionally been used to detect metastatic bone disease, recent literature corroborates the use of 18F-NaF-PET in benign osseous conditions as well. In this review, we discuss the cellular mechanisms of 18F-NaF-PET and examine recent findings on its clinical application in diverse metabolic, autoimmune, and osteogenic bone disorders.

Comparison of 18F-sodium fluoride uptake in the whole bone, pelvis, and femoral neck of multiple myeloma patients before and after high-dose therapy and conventional-dose chemotherapy.

AIM: To compare the effects of high-dose therapy (HDT consisting of high-dose chemotherapy followed by autologous stem cell transplantation) and conventional-dose chemotherapy (non-HDT) on the uptake of 18F-sodium fluoride (NaF) in the whole bone, pelvis, and femoral neck of multiple myeloma (MM) patients. METHOD: The data of 19 MM patients who received HDT (61.5 (SD 5.6) years) and 11 MM patients who received conventional-dose chemotherapy (70.9 (SD 7.2) years) were collected in a prospective study. NaF PET/CT imaging was performed at baseline, and 8 weeks and 2 weeks after treatment for the HDT group and the non-HDT group, respectively. A CT-based algorithm was applied to segment the bones, and the global mean SUV (GSUVmean) of the whole bone and pelvis was calculated (OsiriX MD v.9.0, Pixmeo SARL; Bernex, Switzerland). In addition, regions of interest for the whole, medial, and lateral femoral neck were delineated bilaterally. Whole bone and pelvis measurements were replicated by two observers. RESULTS: The average GSUVmean in the whole bone and pelvis of the patients who underwent HDT significantly decreased from before to after treatment (- 16.27%, p = 0.02 and - 16.54%, p = 0.01, respectively). A significant decrease in the whole and lateral femoral neck was also observed bilaterally in the HDT group. No significant decrease in average GSUVmean was observed in the non-HDT group. A high level of inter-observer reliability was found in intra-class correlation (ICC for pre-treatment whole bone 0.983, post-treatment whole bone 0.989, pre-treatment whole pelvis 0.998, post-treatment whole pelvis 0.996). CONCLUSION: NaF uptake significantly decreased after treatment in patients who received high-dose therapy. A high level of agreement was observed between two operators for whole bone and pelvis measurements.

A prospective study of the feasibility of FDG-PET/CT imaging to quantify radiation-induced lung inflammation in locally advanced non-small cell lung cancer patients receiving proton or photon radiotherapy.

PURPOSE: This prospective study assessed the feasibility of 18F-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) to quantify radiation-induced lung inflammation in patients with locally advanced non-small cell lung cancer (NSCLC) who received radiotherapy (RT), and compared the differences in inflammation in the ipsilateral and contralateral lungs following proton and photon RT. METHODS: Thirty-nine consecutive patients with NSCLC underwent FDG-PET/CT imaging before and after RT on a prospective study. A novel quantitative approach utilized regions of interest placed around the anatomical boundaries of the lung parenchyma and provided lung mean standardized uptake value (SUVmean), global lung glycolysis (GLG), global lung parenchymal glycolysis (GLPG) and total lung volume (LV). To quantify primary tumor metabolic response to RT, an adaptive contrast-oriented thresholding algorithm was applied to measure metabolically active tumor volume (MTV), tumor uncorrected SUVmean, tumor partial volume corrected SUVmean (tumor-PVC-SUVmean), and total lesion glycolysis (TLG). Parameters of FDG-PET/CT scans before and after RT were compared using two-tailed paired t-tests. RESULTS: All tumor parameters after either proton or photon RT decreased significantly (p < 0.001). Among the 21 patients treated exclusively with proton RT, no significant increase in PVC-SUVmean or PVC-GLPG was observed in ipsilateral lungs after the PVC parameters of primary tumor were subtracted (p = 0.114 and p = 0.453, respectively). Also, there were no significant increases in SUVmean or GLG of contralateral lungs of patients who received proton RT (p = 0.841, p = 0.241, respectively). In contrast, among the nine patients who received photon RT, there was a statistically significant increase in PVC-GLPG of ipsilateral lung (p < 0.001) and in GLG of contralateral (p = 0.036) lung. In the subset of nine patients who received a combined proton and photon RT, there was a statistically significant increase in PVC-GLPG of ipsilateral lung (p < 0.001). CONCLUSION: Our data suggest less induction of inflammatory response in both the ipsilateral and contralateral lungs of patients treated with proton compared to photon or combined proton-photon RT.

Prevalence of clinically significant incidental findings by whole-body fludeoxyglucose F 18 positron emission tomography/computed tomography scanning in moderate-to-severe psoriasis patients participating in clinical trials.

BACKGROUND: There has been an increase in the number of psoriasis treatments being investigated in clinical trials. Patients may have undiagnosed issues at the start of a study which may become identified during follow-up as incident medicinal conditions. The prevalence of incidental findings in patients with moderate-to-severe psoriasis presenting for clinical trials is unknown. OBJECTIVE: Determine the prevalence of incidentalomas and rate of malignancy identified by fludeoxyglucose F 18 (FDG) positron emission tomography/computed tomography (PET/CT) imaging in clinical trial patients with moderate-to-severe psoriasis. METHODS: A cross-sectional secondary analysis of patients with moderate-to-severe psoriasis who underwent FDG PET/CT scans at the baseline visit, before randomization, for 3 phase 4 clinical trials on vascular inflammation in psoriasis. Only patients without active infection, malignancy, or uncontrolled comorbidities were eligible for the clinical trials. RESULTS: A total of 259 healthy patients with moderate-to-severe psoriasis underwent an FDG PET/CT scan as part of the study procedures. In all, 31 patients (11.97%) (95% confidence interval [CI], 8.28-16.56) had clinically significant incidentalomas on the baseline FDG PET/CT scan. Univariate logistic regression demonstrated that with every increase of 10 years of age, there was an approximate 30% increased risk of discovery of an incidentaloma (odds ratio, 1.30; 95% CI, 1.01-1.68). Of those patients with findings suggestive of malignancy (n = 28), 6 were confirmed to have cancer, resulting in a 2.31% (95% CI, 0.9-5.0) prevalence of malignancy. The positive predictive value of a true cancer was 31.58% (range, 21%-54%). LIMITATIONS: Generalizability and lost to follow-up. CONCLUSION: Incidentalomas on FDG PET/CT imaging are common in otherwise healthy, asymptomatic patients with moderate-to-severe psoriasis in clinical trials. Our results can help inform interpretation of clinical trial safety data and emphasize the importance of compliance with cancer screening recommendations.

Utility of 18 F-FDG PET/CT in pre-surgical risk stratification of patients with breast cancer.

OBJECTIVE: To determine the correlation between fluorine-18-fluorodeoxyglucose (18F-FDG) uptake values and clinicopathological prognostic markers using preoperative 18F-FDG positron emission tomography/computed tomography (PET/CT) in primary breast cancer (BC). SUBJECTS AND METHODS: One hundred and twelve patients with primary BC were studied prospectively. Pretreatment 18F-FDG PET/CT was performed. Maximum standardized uptake values (SUVmax) were compared with various clinicopathological variables. RESULTS: In a univariate analysis, SUVmax correlated well with the following prognostic variables: T stage, absence of progesterone receptor (PR), absence of estrogen receptor (ER), triple negative lesions (ER/PR and Her 2 negative) and high histologic grade. Metastatic lesions and ductal lesions had higher SUVmax than lobular carcinoma. No significant correlation was found between SUVmax,and human epidermal growth factor receptor 2 (Her-2) statusor perineural and lymphovascular invasion. Multivariate analyses showed that breast density, tumor size and PR negativity were significantly correlated with SUVmax (P=0.046 and 0.009, respectively). CONCLUSION: The pre-treatment tumor SUVmax could be utilized as an independent imaging biomarker of the tumor aggressiveness and poor prognosis. Risk stratification based on this index could play a pivotal role in alteration of treatment planning, such as neoadjuvant chemotherapy (precision oncology).

Association between age, uptake of 18F-fluorodeoxyglucose and of 18F-sodium fluoride, as cardiovascular risk factors in the abdominal aorta.

OBJECTIVE: We aimed to assess the feasibility of quantifying fluorine-18-fluorodexoglucose (18F-FDG) and 18F-sodium fluoride (18F-NaF) uptake in abdominal aorta and examine their association with age and cardiovascular risk factors. SUBJECTS AND METHODS: Our study comprised 123 subjects (48±14 years of age, 62 men) including 78 healthy volunteers and 45 patients with chest pain syndrome, who originally enrolled in the CAMONA study in Odense, Denmark (NCT01724749). All subjects underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) and 18F-NaF PET/CT on separate days, 180min and 90min after administration of tracers, respectively. The global tracer uptake value (GTUV) in the abdominal aorta was determined as sum of the product of each slice area and its corresponding average standardized uptake value (SUV mean), divided by the sum of those slice areas. In addition, for each subject, the 10 years Framingham risk score (FRS) was calculated. The correlations between 18F-NaF and 18F-FDG GTUV with age and 10 years FRS were assessed in all, healthy and patient subjects. RESULTS: There was a significant, positive correlation between subjects' age and 18F-NaF GTUV (r=0.35, P<0.001), but not 18F-FDG GTUV (r=0.06, P=0.53). Also, there was a significant, positive correlation between 10 years FRS and 18F-NaF GTUV (r=0.30, P<0.001), but not 18F-FDG GTUV (r=0.01, P=0.95). Individual differences in 18F-FDG and 118F-NaF uptake were large in both healthy subjects and patients. CONCLUSION: In this study, the global uptake of 18F-NaF in abdominal aorta was positively associated with age and 10 years FRS in all subjects, healthy and patient groups, whereas the global uptake of 18F-FDG was not.

Futility of attempts to detect and quantify beta cells by PET imaging in the pancreas: why it is time to abandon the approach.

In this commentary, we describe the limitations of positron emission tomography (PET) in visualising and characterising beta cell mass in the native pancreas in healthy individuals and those diagnosed with diabetes. Imaging with PET requires a large mass of targeted cells or other structures in the range of approximately 8-10 cm3. Since islets occupy only 1% of the pancreatic volume and are dispersed throughout the organ, it is our view that uptake of PET tracers, including [18F]fluoropropyl-(+)-dihydrotetrabenazine, in islets cannot be successfully detected by current imaging modalities. Therefore, we dispute the feasibility of PET imaging for the detection of loss of beta cells in the native pancreas in individuals with diabetes. However, we believe this novel approach can be successfully employed to visualise beta cell mass in individuals with hyperinsulinism and transplanted islets.

18F-NaF and 18F-FDG as molecular probes in the evaluation of atherosclerosis.

The early detection of atherosclerotic disease is vital to the effective prevention and management of life-threatening cardiovascular events such as myocardial infarctions and cerebrovascular accidents. Given the potential for positron emission tomography (PET) to visualize atherosclerosis earlier in the disease process than anatomic imaging modalities such as computed tomography (CT), this application of PET imaging has been the focus of intense scientific inquiry. Although 18F-FDG has historically been the most widely studied PET radiotracer in this domain, there is a growing body of evidence that 18F-NaF holds significant diagnostic and prognostic value as well. In this article, we review the existing literature on the application of 18F-FDG and 18F-NaF as PET probes in atherosclerosis and present the findings of original animal and human studies that have examined how well 18F-NaF uptake correlates with vascular calcification and cardiovascular risk.

Prognostic role of serial quantitative evaluation of 18F-fluorodeoxyglucose uptake by PET/CT in patients with cardiac sarcoidosis presenting with ventricular tachycardia.

BACKGROUND: Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) has shown to be useful in diagnosis, staging and monitoring of cardiac sarcoidosis (CS) but its interpretation is not standardized. OBJECTIVES: We sought to investigate the clinical impact of serial quantitative FDG uptake analysis in patients with CS presenting with ventricular tachycardia (VT) treated by catheter ablation (CA). METHODS: We followed 20 patients (51 ± 9 years, 70% males) with CS and VT who underwent CA, with 92 serial FDG-PET scans (3-10 per patient). Myocardial FDG-avid lesions were quantified using three parameters: maximum standardized uptake value (SUVmax), partial-volume corrected mean standardized uptake value (SUVmean) and partial-volume corrected volume-intensity product [lesion metabolic activity (LMA)]. The volume-intensity product of the entire heart [global cardiac metabolic activity (gCMA)] and the background cardiac metabolic activity (bCMA: difference between gCMA and LMA) were also calculated. The primary end-point was the occurrence of major adverse cardiac events (MACE), including death, heart transplant, hospitalization for heart failure and implantable cardioverter defibrillator (ICD) appropriate interventions. Evolution of echocardiographic parameters over follow-up was also assessed. RESULTS: During a median follow-up of 35 (20-66) months, 18 MACE (1 death, 2 heart transplants, 12 ICD appropriate interventions, 3 hospitalizations) occurred in 12 (60%) patients. At univariable analysis, lack of PET improvement (defined by decrease in LMA of at least 25%) was the only variable associated with cardiac events during follow-up. In particular, non-responders had a 20-fold higher risk of MACE at follow-up (HR 18.96, 95% CI 2.26-159.27; p = 0.007). Moreover, a significant linear inverse relationship was observed between changes in LMA and changes in left ventricular ejection fraction over follow-up (ß = -20.11; p = 0.003). CONCLUSIONS: In patients with CS and VT, temporal change in FDG uptake evaluated by a quantitative approach is associated with parallel change in systolic function. Moreover, reduction in FDG uptake is strongly associated with fewer MACE at long-term follow-up.

Global temporal lobe asymmetry as a semi-quantitative imaging biomarker for temporal lobe epilepsy lateralization: A machine learning classification study.

OBJECTIVE: The purpose of this study was to evaluate the utility of global semi-quantitative analysis via fluorine-18-flurodeoxyglucose positron emission tomography (18F-FDG PET) at lateralizing seizure foci and diagnosing patients with unilateral temporal lobe epilepsy (TLE). METHODS: Seventeen patients with unilateral TLE (11 right TLE and 6 left TLE) were retrospectively selected for semi-quantitative 18F-FDG PET analysis. Twenty-three control subjects with a Mini Mental State Examination (MMSE) score of 29 or greater were selected for comparison. Globally averaged standardized uptake value (gSUVmean) was computed for each temporal lobe. Lateralization indices (LI) and the absolute value of lateralization indices (|LI|) were calculated to assess the degree of asymmetry in each subject. Logistic regression analyses were performed at a probability cutoff of 0.5 to classify TLE patients as left or right TLE and to discriminate patients from control subjects. Receiver operating characteristic (ROC) curves were generated to evaluate the utility of LI and |LI| as classification predictors. The Bland Altman test was used to evaluate the reproducibility of the measurements. RESULTS: There was a statistically significant difference in gSUVmean computed LI between left and right TLE patients (P<0.01). There was no statistically significant difference in |LI| between the patient and control groups (P=0.22). Logistic regression revealed that 82% of TLE patients were lateralized correctly using LI as the sole predictor. The area under the ROC curve (AUC) was 0.80. Logistic regression using |LI| on the combined patient/control population showed a diagnostic accuracy of 65% and an AUC of 0.44. Bland Altman analysis revealed an intra-observer reproducibility of 96% and an inter-observer reproducibility of 96% and 91% on successive trials. CONCLUSION: We conclude that gSUVmean computed LI is a reliable and reproducible measure for predicting seizure lateralization in unilateral TLE patients. However, gSUVmean computed |LI| does not appear to be particularly effective at diagnosing TLE patients from control subjects. Further studies with more patients should investigate other machine learning techniques that combine gSUVmean with other diagnostic predictors.

CT-based tissue segmentation to assess knee joint inflammation and reactive bone formation assessed by 18F-FDG and 18F-NaF PET/CT: Effects of age and BMI.

OBJECTIVE: This study was conducted to determine the role of computed tomography (CT)-based segmentation methodology to semi-quantify the degree of inflammation and reactive bone formation in the knee joints by fluorine-18-fluorodeoxyglucose (18F-FDG) and 18F-sodium fluoride positron emission tomography/CT (18F-NaF PET/CT) imaging, respectively. Furthermore, we assessed the impact of aging and body mass index (BMI) on these biological responses. SUBJECTS AND METHODS: In this retrospective study, we examined a total of 97 subjects who had undergone both 18F-FDG and 18F-NaF PET/CT scanning. The mean age was 49.3±14.9 (21-75) and the mean BMI was 26.7±4.3 (17.7-42.0). Whole joint compartments and osseous compartments were segmented on fused PET/CT images using a 3D-growing algorithm with an adjustable upper/lower Hounsfield Units (HU) thresholds and manual tools. The metabolic activity and volume of each compartment was measured, values from the osseous compartment were subtracted from the whole joint to get the volume and metabolic activity of the soft tissue. The metabolic activity was correlated with age and BMI. RESULTS: Fluorine-18-FDG uptake in the soft tissues surrounding the joint was 0.35±0.07 while 0.19±0.04 in the osseous structures (P<0.0001). Aging positively correlated with 18F-FDG uptake in the soft tissue (r=0.37, P=0.0001). Body mass index positively correlated with 18F-FDG uptake in the soft tissue (r=0.53, P<0.0001), osseous compartment (r=0.58, P<0.0001) and 18F-NaF uptake in the joint (r=0.37, P=0.0001). A positive association was noted between the degree of new bone formation and the inflammatory reaction (P<0.01). CONCLUSION: The PET-based molecular imaging probes along with the CT-based segmentation techniques revealed an association between aging and the inflammatory activity of the soft tissue compartment. Similarly, a positive correlation was noted between BMI and inflammation and reactive bone f ormation of the knee joint compartments.

Efficacy of 18F-FDG and 18F-NaF PET/CT imaging: A novel semi-quantitative assessment of the effects of age and obesity on hip joint inflammation and bone degeneration.

OBJECTIVE: Osteoarthritis (OA) is characterized by synovial tissue inflammation and underlying bone degeneration in the joints. Aging and obesity are among the major risk factors. This study evaluated the effects of aging and body mass index (BMI) on hip joint inflammation and bone degeneration using fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and fluorine-18 sodium fluoride (18F-NaF) PET/CT imaging, respectively. SUBJECTS AND METHODS: In this retrospective study, a total of 116 subjects (58 males and 58 females) who had undergone both 18F-FDG and 18F-NaF PET/CT imaging were analyzed. The mean age of these subjects was 48.6±14.5 with an age range of 21-75 years. Fluorine-18-FDG and 18F-NaF PET/CT imaging was conducted 180min and 90min (respectively) after intravenous administration of the appropriate tracer. The hip joint was segmented on fused PET/CT images using OsiriX MD v.9.5 (DICOM viewer and image-analysis program, Pixmeo SARL; Bernex, Switzerland). The region of interest (ROI) for the hip joint was indicated by using a 3D-growing region algorithm with upper/lower Hounsfield Units (HU) followed by a morphological closing algorithm. The metabolic activity for the left and right side of the joint was measured and correlated with age and BMI. RESULTS: Fluorine-18-FDG uptake in the hip was 0.83±0.22 (right side: 0.83±0.23, left side: 0.83±0.22, P=0.82). Fluorine-18-NaF uptake in the hip was 3.20±1.07 (right side: 3.25±1.14, left side: 3.15±1.04, P=0.02). Body mass index positively correlated with both 18F-FDG (r=0.29, P=0.001) and NaF (r=0.26, P=0.005) uptake. No significant correlation was seen between age and either 18F-FDG (r=0.12, P=0.19) or 18F-NaF (r=0.03, P=0.78) uptake. CONCLUSION: Body mass index had a significant impact on 18F-FDG and 18F-NaF uptake, whereas age had no correlation with either tracer uptake. Obesity increases the mechanical forces applied on weight-bearing joints such as the hip. Body mass index was related to increased joint inflammation and bone degeneration. These findings further support the studies explaining the role of adipose tissue in promoting OA.

Normal patterns of regional brain 18F-FDG uptake in normal aging.

OBJECTIVE: Normal aging alters the brain function even in the absence of recognizable structural changes, which can be detected using modern in vivo functional imaging modalities such as fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) scan. It is highly important to recognize normal age-dependent changes in order to correctly diagnose pathologic states. The goal of the current study was to evaluate the age-related changes in regional brain 18F-FDG uptake in normal healthy population. SUBJECTS AND METHODS: This study was part of the cardiovascular molecular calcification assessed by 18F-sodium fluoride (NaF) (CAMONA) PET/computed tomography (CT) study. This study was approved by the Danish National Committee on Health Research Ethics registered at ClinicalTrials.gov (NCT01724749). Forty normal healthy subjects were prospectively recruited in group A (22-32 years) and B (56-75 years) and underwent 18F-FDG PET/CT. Static images were obtained 180 minutes following 18F-FDG injection. Supratentorial (including individual measurements for frontal, parieto-occipital and temporal lobes) and cerebellar 18F-FDG uptakes were measured by manual placement of region of interest (ROI) over these regions based on predefined criteria for each and standardized uptake value (SUVmean) values were calculated using OsiriX software. RESULTS: The mean ages of the patients in group A was 26.1±3.4 versus 61±4.4 for group B. There were 10 females in group A and 10 females in group B. Mean SUV of cerebellum was 6.80±1.21 for the young subjects compared to 6.08±0.7 among old subjects (independent t-test, P=0.028). Mean SUV of supratentorial brain was 9.14±1.83 for the young subjects compared to 6.92±072 among old subjects (P<0.001). Mean SUV of frontal (9.72±1.97 vs. 7.03±0.69), temporal (7.37±1.52 vs. 5.65±0.68) and parieto-occipital region (10.7±2.28 vs. 7.41±0.79) was higher among young patients (P<0.001). More interestingly, SUVmean of supratentorial brain was significantly higher among female healthy volunteers in both groups (P= 0.025 and 0.047 for group A and B, respectively). CONCLUSION: In conclusion, these findings confirm a significant age dependent reduction of supratentorial 18F-FDG uptake among healthy individuals. However, cerebellum 18F-FDG uptake reduction was not so redundant. Fluorine-18-FDG uptake of all cerebral lobes including frontal, parieto-occipital and temporal decreases with normal aging in a same fashion. Interestingly, among both young and old female subjects, higher uptake was seen in supratentorial brain.

18F-Fluorodeoxyglucose positron emission tomography and infectious diseases: current applications and future perspectives.

PURPOSE OF REVIEW: 18F-Fluorodeoxyglucose positron emission tomography/computed tomography is a well-established technique for diagnosis and management of a number of neoplastic conditions. However, in recent years the body of literature regarding its potential role in infectious diseases has progressively increased, with promising results. RECENT FINDINGS: So far 18F-fluorodeoxyglucose positron emission tomography/computed tomography has a well-established role and is recommended by guidelines only in a few settings, such as prosthetic valve endocarditis, vascular device infections, and chronic osteomyelitis. However, even the lack of large, prospective randomized trials, an increasing number of small series and case reports suggest a potential role in the diagnosis, disease staging, and monitoring of treatment response of several other infective conditions. SUMMARY: In this article, we summarize the available evidence and potential future applications of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the diagnosis and management of infectious diseases.

An update on the role of PET/CT and PET/MRI in ovarian cancer.

This review article summarizes the role of PET/CT and PET/MRI in ovarian cancer. With regard to the diagnosis of ovarian cancer, the presence of FDG uptake within the ovary of a postmenopausal woman raises the concern for ovarian cancer. Multiple studies show that FDG PET/CT can detect lymph node and distant metastasis in ovarian cancer with high accuracy and may, therefore, alter the management to obtain better clinical outcomes. Although PET/CT staging is superior for N and M staging of ovarian cancer, its role is limited for T staging. Additionally, FDG PET/CT is of great benefit in evaluating treatment response and has prognostic value in patients with ovarian cancer. FDG PET/CT also has value to detect recurrent disease, particularly in patients with elevated serum CA-125 levels and negative or inconclusive conventional imaging test results. PET/MRI may beneficial for tumor staging because MRI has higher soft tissue contrast and no ionizing radiation exposure compared to CT. Some non-FDG PET radiotracers such as 18F-fluorothymidine (FLT) or 11C-methionine (MET) have been studied in preclinical and clinical studies as well and may play a role in the evaluation of patients with ovarian cancer.