Journal of Nuclear Cardiology最新文献

Cardiac amyloidosis (CA) is one of the causes of restrictive cardiomyopathy. [^99mTc]Tc-pyrophosphate (PYP) is a sensitive diagnostic tool in diagnosing transthyretin CA. This multicenter retrospective study evaluated whether bone uptake can serve as a reliable reference in [99mTc]Tc-pyrophosphate (PYP) scintigraphy for cardiac amyloidosis (CA). Cases with heart failure preserved ejection fraction whose 99mTc PYP scintigraphy images were evaluated as negative for CA involvement, obtained from two dedicated centers, were included in this retrospective study. AL amyloidosis was ruled out in all patients according to serum/urine laboratory test results. On SPECT images, ROI was drawn over the thoracic vertebral body as bone (B), lung (L), left ventricular cavity as blood pool (BP), interventricular septum (IS), liver (LV), and paraspinal muscle as soft tissue (ST). Counts, volumes; maximum, mean, and minimum standardized uptake values (SUVmax, SUVmean, and SUVmin, respectively) of each ROI were recorded. Counts were corrected according to volumes. A Total of 191 cases (Center 1: n = 92, Center 2: n = 99) were included in the study. Median ages were 68. No significant difference was detected in terms of age and gender between the two centers. When evaluating all cases, B counts, B SUVmean, and BP values were significantly higher in women (p < 0.05). B counts and B SUVmean did not differ between centers and demonstrated a strong correlation between 1h and 3h images (ρ = 0.75, p < 0.001). These findings indicate that bone uptake is stable across centers and time points, supporting its role as a quantitative reference, although higher uptake in women may challenge visual interpretation.

Background: Folate receptor ß (FR-ß) is expressed on activated macrophages in inflammatory conditions. In order to study FR-ß in inflammatory response following myocardial infarction (MI), we evaluated FR-ß-targeted PET imaging using aluminum fluoride-18-labeled NOTA-folate ([¹⁸F]FOL) in a rat model of MI.

Methods: Rats underwent [¹⁸F]FOL PET imaging on 3, 7, 15, and 90 days after induction of MI by permanent coronary artery ligation or sham-operation. [¹⁸F]FDG PET was performed a day before [¹⁸F]FOL scan to localize the infarct area. A subset of rats underwent [¹⁸F]FOL PET on day 7 and serial echocardiography until 90 days post-surgery.

Results: The [¹⁸F]FOL uptake was significantly higher in infarct area than in the myocardium of sham-operated rats on day 3 (SUV 1.97 ± 0.17 vs. 0.74 ± 0.13), and remained higher on day 7 (SUV 1.35 ± 0.33 vs. 0.70 ± 0.16), day 15 (SUV 1.24 ± 0.20 vs. 0.59 ± 0.07), and day 90 (SUV 1.39 ± 0.25 vs. 0.69 ± 0.11). Autoradiography of tissue sections confirmed tracer uptake in the infarct area, where immunofluorescence showed FR-ß in CD68-positive macrophages. Uptake of [¹⁸F]FOL correlated with CD68-positive macrophage density (r = 0.669, p < 0.001) and was associated with decline in left ventricular ejection fraction between days 7 and 90 post-MI (r = -0.665, p = 0.007).

Conclusion: [¹⁸F]FOL PET detects expression of FR-β, a marker of activated macrophages after MI. FR-β expression peaks early and remains elevated up to 3 months post-MI. Early FR-β expression is associated with worsening of left ventricular systolic function.

Total-body PET systems with long axial field of view (LAFOV) are now commercially available and represent the state of the art in PET imaging. These systems provide wide anatomical coverage and markedly increased detection sensitivity. Clinical studies have demonstrated enhanced image quality, superior quantification, and benefits for tracer kinetic modeling through dynamic imaging. LAFOV PET/CT allows for substantial reductions in acquisition time and radiation dose while maintaining diagnostic image quality. Full-body coverage enables dynamic whole-body imaging, which enables tracer kinetic modeling across multiple organs and the large vascular structures, offering new opportunities for studying their interactions in cardiovascular and systemic diseases. Furthermore, these systems facilitate the development of new PET methods, including pharmacokinetics of new tracers. This review discusses the emerging opportunities and challenges associated with the application of LAFOV PET/CT systems in cardiovascular diseases.

Background: [¹⁸F]flurpiridaz is a newly FDA-approved tracer for PET MPI with a long half-life and improved physical characteristics. However, its long half-life leads to residual rest activity. Prior trials used 30 to 60 minutes delays between rest and stress injections and proposed stress-to-rest dose ratios of 1:2 to 1:3 to mitigate the potential impact of residual rest counts on the stress myocardial perfusion images.

Objective: To evaluate the effect of stress-to-rest dose ratio and time interval between injections on residual activity.

Methods: We analyzed consecutive 115 patients who underwent PET MPI with [¹⁸F]flurpiridaz. Relative Residual activity was calculated as the ratio of tissue activity concentration (kBq/mL) in the first stress frame to that in the stress tissue phase. Linear regression was used to assess the association of dose ratio and injection time interval with global residual activity. The optimal dose ratio cutoff was identified. Mixed-effects models with interaction terms were used to assess whether the effect varied across vascular territories.

Results: A total of 115 patients underwent PET MPI. Results showed that increasing the stress-to-rest dose ratio was significantly associated with lower relative residual activity (β = -3.41; 95% CI: -4.72; -2.11 per 1-unit increase), while increasing the time interval between injections up to 39 minutes showed no significant association (β =0.03 95% CI: -0.12; 0.17 per 1-minute increase) within this time window. The optimal cutoff dose ratio to achieve relative residual activity <20% ranged between 3.2 and 4.3.

Conclusion: Increasing the stress-to-rest dose ratio between 3.2 and 4.3, effectively reduces residual activity to <20% of the stress dose across all time intervals, thereby enabling back-to-back imaging and improving protocol efficiency on digital PET systems. Further validation is warranted for older, non-digital scanners.

Background: Colchicine reduces sympathetic denervation after acute myocardial infarction (AMI), yet the COLD-MI trial found no change in myocardial perfusion scintigraphy (MPS). MPS-detected necrotic lesions were limited by early management, and MPS may therefore have lacked the sensitivity to capture subtle colchicine-induced variations in minimal necrosis during the immediate post-stenting period. Myocardial perfusion reserve (MPR), a quantitative indicator of global microvascular function, may overcome these limitations. This ancillary analysis of the COLD-MI trial evaluated whether colchicine improves MPR six months after AMI.

Methods: Forty-five post-AMI patients randomized to colchicine for 30 days or no colchicine underwent quantitative dynamic [99mTc]Tc-tetrofosmin SPECT and [123I]-mIBG imaging at 6 months. MPR was quantified using CZT-SPECT as the stress-to-rest uptake ratio. Secondary endpoints included MPS scoring (SRS, SSS, SDS) and sympathetic innervation assessed by normalized mean segmental activity. Analyses were blinded.

Results: Colchicine-treated patients showed significantly higher MPR in remote myocardium than controls (2.37 ± 0.61 vs. 1.92 ± 0.53; p = 0.01). Denervated myocardial surface area in remote regions was also lower with colchicine (43% [29-50] vs. 50% [38-64]; p = 0.04). In infarcted myocardium, MPR did not differ (1.79 ± 0.61 vs. 1.60 ± 0.63; p = 0.35). A non-significant trend toward better preserved innervation was observed (denervation: 46% [35-50] vs. 50% [45-69]; p = 0.09). SRS, SSS, and SDS were similar between groups.

Conclusions: Colchicine significantly increases MPR in remote myocardium six months after AMI, consistent with reduced sympathetic denervation and supporting a microvascular benefit of colchicine post-AMI.