PurposeThe expression of chemokine receptor type 4 (CXCR4) was found co-localized with macrophages on the atherosclerotic vessel wall and participated in the initial emigration of leukocytes. Gallium-68 [68Ga]Pentixafor has recently been introduced for the imaging of atherosclerosis by targeting CXCR4. We sought to evaluate human atherosclerotic lesions using [68Ga]Pentixafor PET/MRI.MethodsThirty-eight oncology patients underwent [68Ga]Pentixafor PET/MR imaging at baseline. Maximum standardized uptake values (SUVmax) were derived from hot lesions in seven arterial segments and target-to-blood ratios (TBR) were calculated. ANOVA post-hoc and paired t test were performed for statistical comparison, Spearman’s correlation coefficient between uptake ratios and cardiovascular risk factors were assessed. The reproducibility of [68Ga]Pentixafor PET/MRI was assessed in seven patients with a follow-up exanimation by Pearson’s regression and Bland–Altman plots analysis.ResultsThirty-four of 38 patients showed 611 focal [68Ga]Pentixafor uptake that followed the contours of the large arteries. Both prevalence and mean TBRmax were highest in the descending aorta. There were significantly higher TBR values found in men (1.9 ± 0.3) as compared to women (1.7 ± 0.2; p < 0.05). Patients with mean TBRmax > 1.7 showed a significantly higher incidence of diabetes, hypertension hypercholesterolemia and history of cardiovascular disease than patients with mean TBRmax ≤ 1.7. [68Ga]Pentixafor uptake showed a good reproducibility (r = 0.6, p < 0.01), and there was no difference between the mean TBRmax values of plaque lesions (TBRbaseline1.8 ± 0.3 vs TBRfollow-up1.8 ± 0.3) (p = 0.9).ConclusionPatients with high arterial uptake showed increased incidence of cardiovascular risk factors, suggesting a potential role of [68Ga]Pentixafor in characterization of atherosclerosis.
BackgroundAccurate quantification of plaque imaging using 18F-NaF PET requires partial volume correction (PVC).MethodsPVC of PET data was implemented by the use of a local projection (LP) method. LP-based PVC was evaluated with an image quality (NEMA) and with a thorax phantom with “plaque-type” lesions of 18-36 mL. The validated PVC method was then applied to a cohort of 17 patients, each with at least one plaque in the carotid or ascending aortic arteries. In total, 51 calcified (HU > 110) and 16 non-calcified plaque lesions (HU < 110) were analyzed. The lesion-to-background ratio (LBR) and the relative change of LBR (ΔLBR) were measured on PET.ResultsFollowing PVC, LBR of the spheres (NEMA phantom) was within 10% of the original values. LBR of the thoracic lesions increased by 155% to 440% when the LP-PVC method was applied to the PET images. In patients, PVC increased the LBR in both calcified [mean = 78% (−8% to 227%)] and non-calcified plaques [mean = 41%, (−9%-104%)].ConclusionsPVC helps to improve LBR of plaque-type lesions in both phantom studies and clinical patients. Better results were obtained when the PVC method was applied to images reconstructed with point spread function modeling.Electronic supplementary materialThe online version of this article (doi:10.1007/s12350-017-0778-2) contains supplementary material, which is available to authorized users.
PurposePET with 18F-FDG has the potential to assess vascular macrophage metabolism. 18F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel 18F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior morphological conspicuity of plaque lesions. The purpose of this study was to evaluate the reliability and accuracy of 18F-FDG PET/MRI uptake quantification compared to PET/CT as a reference standard in patients with carotid atherosclerotic plaques.MethodsThe study group comprised 34 consecutive oncological patients with carotid plaques who underwent both PET/CT and PET/MRI with 18F-FDG on the same day. The presence of atherosclerotic plaques was confirmed by 3 T MRI scans. Maximum standardized uptake values (SUVmax) for carotid plaque lesions and the average SUV of the blood pool within the adjacent internal jugular vein were determined and target-to-blood ratios (TBRs, plaque to blood pool) were calculated.ResultsAtherosclerotic lesions with maximum colocalized focal FDG uptake were assessed in each patient. SUVmax values of carotid plaque lesions were significantly lower on PET/MRI than on PET/CT (2.3 ± 0.6 vs. 3.1 ± 0.6; P < 0.01), but were significantly correlated between PET/CT and PET/MRI (Spearman’s r = 0.67, P < 0.01). In contrast, TBRmax values of plaque lesions were similar on PET/MRI and on PET/CT (2.2 ± 0.3 vs. 2.2 ± 0.3; P = 0.4), and again were significantly correlated between PET/MRI and PET/CT (Spearman’s r = 0.73, P < 0.01). Considering the increasing trend in SUVmax and TBRmax values from early to delayed imaging time-points on PET/CT and PET/MRI, respectively, with continuous clearance of radioactivity from the blood, a slight underestimation of TBRmax values may also be expected with PET/MRI compared with PET/CT.ConclusionSUVmax and TBRmax values are widely accepted reference parameters for estimation of the radioactivity of atherosclerotic plaques on PET/CT. However, due to a systematic underestimation of SUVmax and TBRmax with PET/MRI, the optimal cut-off values indicating the presence of inflamed plaque tissue need to be newly defined for PET/MRI.
18 F-FDG is the most widely validated PET tracer for the evaluation of atherosclerotic inflammation. Recently, 18 F-NaF has also been considered a potential novel biomarker of osteogenesis in atherosclerosis. We aimed to analyze the association between inflammation and osteogenesis at different stages of atherosclerosis, as well as the interrelationship between these 2 processes during disease progression. Methods: Thirty-four myeloma patients underwent 18 F-NaF and 18 F-FDG PET/CT examinations. Lesions were divided into 3 groups (noncalcified, mildly calcified, and severely calcified lesions) on the basis of calcium density as measured in Hounsfield units by CT. Tissue-to-background ratios were determined from PET for both tracers. The association between inflammation and osteogenesis during atherosclerosis progression was evaluated in 19 patients who had at least 2 examinations with both tracers. Results: There were significant correlations between the maximum tissue-to-background ratios of the 2 tracers (Spearman r 5 0.5 [P , 0.01]; Pearson r 5 0.4 [P , 0.01]) in the 221 lesions at baseline. The highest uptake of both tracers was observed in noncalcified lesions, but without any correlation between the tracers (Pearson r 5 0.06; P 5 0.76). Compared with noncalcified plaques, mildly calcified plaques showed concordant significantly lower accumulation, with good correlation between the tracers (Pearson r 5 0.7; P , 0.01). In addition, enhanced osteogenesis-derived 18 F-NaF uptake and regressive inflammation-derived 18 F-FDG uptake were observed in severely calcified lesions (Pearson r 5 0.4; P , 0.01). During follow-up, increased calcium density and increased mean 18 F-NaF uptake were observed, whereas mean 18 F-FDG uptake decreased. Most noncalcified (86%) and mildly calcified (81%) lesions and 47% of severely calcified lesions had concordant development of both vascular inflammation and osteogenesis. Conclusion: The combination of 18 F-NaF PET imaging and 18 F-FDG PET imaging promotes an understanding of the mechanism of plaque progression, thereby providing new insights into plaque stabilization.
Objectives The aim of this prospective study was to examine whether ultrasound or clinical abnormalities at enthesal sites predict radiographic progression at entheses in psoriatic arthritis (PsA). Methods Consecutive PsA patients were included and subjected to clinical and ultrasound assessments at 14 entheses at baseline, 6 and 12 months. Radiographs were performed at 0 and 12 months. By US, we investigated structural (erosions, osteophytes) and inflammatory changes [grey scale (0–32) and power Doppler (0–14, range global ultrasound score 0–140)], and radiographs were evaluated for enthesophytes and erosions (score range 0–56). Multivariate regression models were conducted to identify the possible association of clinical and ultrasound findings with radiographic progression. Results We examined 83 patients at baseline, of whom 43 (51.8%) had complete clinical, ultrasound and X-ray data. Twenty-four of 43 patients (55.8%) developed radiographic progression of entheses. These patients were younger (49.6 vs 59.3, P =0.005), had shorter disease duration (9.7 vs 17.9 years, P=0.015) and lower clinical disease activity at 6-months [disease activity in psoriatic arthritis (DAPSA) 6.7 vs 17.0, P=0.018] as compared with patients without progression. Non-progressors had higher ultrasound enthesophyte scores at baseline than progressors (20 vs 15, P<0.05). The multivariate regression analysis revealed that 48.6% of the variance of the X-ray score at 12-months follow-up (RegcoeffB = 0.827, P=0.000) could be explained by the baseline US enthesophyte score. Conclusion Our data indicate that radiographic progression at entheses is linked with age, disease duration and ultrasound verified enthesophytes at baseline. No other ultrasound parameter predicted radiographic progression at entheses.
Background:Joint replacement is a procedure with a major impact on the quality of life of patients with joint degenerative disease or traumatic injuries. However, some patients develop symptoms after the intervention caused by mechanical loosening or infection. Metabolic imaging by 18F-FDG-PET investigated in these patients isoften hampered by low specificity for diagnosis of possible septic vs. mechanical loosening. The reason for this shortcoming is to our opinion the unawareness of physiological remodeling processes that could be seen in asymptomatic patients.Objectives:In order to overcome this drawback, we aimed to find out the physiological metabolic functional pattern in asymptomatic patients with implanted hip prosthesisPatients and Methods:Twelve patients (6 males, 6 females); mean age 73 ± 7 (range 58 - 91) years were prospectively enrolled in the study. The patients were admitted to our department for oncological referral with implanted hip prostheses. All patients explained no symptoms with regard to their implanted prosthesis. The attenuation corrected images were used for analysis.Results:Fourteen hip prostheses in 12 patients were visually analyzed. Seven out of 14 prostheses among 12 patients showed focal periprosthetic enhanced metabolism, two of which showed two sites of enhanced uptake; whereas, the remaining five prostheses showed singular hypermetabolic areas within the periprosthetic site. The remaining seven prostheses in the other five patients showed no periprosthetic-enhanced uptake.Conclusion:Of the asymptomatic patients investigated, 58% showed focal enhanced periprosthetic glucose metabolism. This finding should be taken into consideration as a more probable unspecific metabolic pattern for correct interpretation of 18F-FDG-PET studies in patients with suspected septic loosening of the hip prosthesis.
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