Journal of Nuclear Cardiology最新文献

Background: In myocardial perfusion imaging (MPI) with single-photon emission computed tomography (SPECT), ungated studies are used for evaluation of perfusion defects despite motion blur. We investigate the potential benefit of motion correction using a deep-learning (DL) network for evaluating perfusion defects.

Methods: We employed a DL network for cardiac motion correction in ECG-gated SPECT-MPI images, wherein the image data from different cardiac phases are combined with respect to a reference gate to reduce motion blur. For training the DL network, 197 cases were used. Given the variability of gated images during the cardiac cycle, we investigated the detectability of perfusion defects in two distinct reference gates. To assess perfusion defect detection, we performed receiver-operating characteristic (ROC) analyses on the motion-corrected images using a separate test dataset of clinical 194 subjects, in which studies were created from actual patient data with inserted simulated-lesions as ground truth. The reconstructed images were assessed by the quantitative-perfusion SPECT (QPS) software. We also evaluated the performance on reduced-count studies (by two and four folds).

Results: The quantitative results, measured by area-under-the-ROC curve (AUC), demonstrated that DL motion correction improves the detectability of perfusion defects significantly on both standard- and reduced-count studies, and that the detectability can vary with reference cardiac phases. A joint assessment from two reference phases achieved AUC = 0.841 on the quarter-count data, higher than with ungated full-count data (AUC = 0.795, P-value = 0.0054).

Conclusions: DL motion correction can benefit assessment of perfusion defects in standard- and reduced-count SPECT-MPI studies. It can also be beneficial to evaluate perfusion images over multiple cardiac phases.

Background: There has been an increasing call for employing ultrashort exercise activity questionnaires as a clinical "vital sign". To-date, this has not been applied to patients undergoing cardiac stress testing.

Methods: We evaluated 1,136 patients who completed a one-item exercise questionnaire before undergoing stress SPECT myocardial perfusion imaging (MPI). This question asked patients to grade how much they exercise during daily life on an 11-point scale (0= none, 10 = always). Patients were divided into four exercise activity groups based on their response: no, low, moderate, and high exercise activity. The results of this questionnaire were compared to patients clinical risk profile, mode of stress testing (exercise versus pharmacologic), and exercise treadmill duration.

Results: We noted a stepwise inverse relationship between exercise activity and patients' frequency of hypertension, diabetes, and obesity (p<0.001 for each). Patients with no reported exercise activity were more likely to complain of dyspnea. There was a stepwise increase in the number of patients performing treadmill exercise with increasing reported exercise activity (p<0.001). The duration on treadmill exercise increased in stepwise fashion with higher patient reported exercise activity (p<0.001).

Conclusion: Our single-item, self-reported questionnaire was correlated to patients' risk profiles, their mode of stress testing, and cardiorespiratory fitness. These correlates, along with the pragmatic nature of this ultrashort questionnaire, and its built-in identification of patients who may warrant exercise counseling, augurs for adopting ultrashort questionnaires regarding exercise activity among patients undergoing stress MPI and other cardiac imaging tests where functional capacity is not routinely assessed.

Background: Exercise activity reduces mortality and favorably influences mediators of risk, including myocardial flow reserve (MFR) and chronotropic responsiveness. Comprehensive research regarding the relationship between exercise activity, MFR, and chronotropic response to pharmacological stress, as assessed by heart rate response (HRR) among patients undergoing PET myocardial perfusion imaging (MPI) has not been performed. Thus, we aimed to evaluate the relationship between exercise activity as assessed by a practical single-item questionnaire, MFR and HRR, and longitudinal clinical risk.

Methods: We studied outpatients who underwent pharmacological stress rubidium-82. PET-MPI and answered a self-reported one-item exercise activity questionnaire (0-10 scale) at the time of PET-MPI. HRR was calculated by the following equation: (stress HR-rest HR)/rest HR*100 (%). The primary outcome was death or myocardial infarction.

Results: Of 1,686 patients, 221 (13%) patients had hard events during our mean follow up of 3.8 years. Patients were divided into four groups: no/minimal exercise (n=551), low exercise (n=468), moderate exercise (n=485), and high exercise (n=182) based on the questionnaire. MFR and HRR increased with exercise activity in a stepwise manner. By Cox analysis adjusted for clinical and PET-MPI variables including MFR and HRR, exercise activity was independently associated with hard events (HR [95%CI] per activity scale, 0.95 [0.91-0.99]; p=0.028).

Conclusions: Patients with higher exercise activity assessed by a practical single-item questionnaire had higher MFR and HRR. Exercise activity was an independent predictor of hard events in patients undergoing PET-MPI. Because of its ease of use, this single-item questionnaire should be applied among patients undergoing stress MPI.

Background: On legacy 2D positron emission tomography (PET) systems utilizing a 50 mL/min Rb-82 profile, test-retest precision of quantitative perfusion is ∼10%. It is unclear whether Rb-82 infusion rate significantly impacts quantitative perfusion and/or image quality on modern analog 3D PET-CT systems. We aimed to determine whether the Rb-82 infusion profile significantly impacts test-retest precision of quantitative perfusion, perfusion metrics, and/or image quality on a modern analog 3D PET-CT scanner.

Methods: Ninety-eight volunteers from 3 distinct groups: healthy volunteers (Normals), patients with risk factors, and/or coronary disease (Clinicals) and patients with prior transmural myocardial infarctions (Infarcts), underwent cardiac stress testing on an analog 3D PET-CT. Participants received 3 consecutive resting scans and 2 consecutive stress scans, minutes apart, with two randomly assigned Rb-82 infusion profiles: 50 mL/min (fast [F]) and 20 mL/min (slow [S]). Perfusion metrics (resting (rMBF) and stress myocardial blood flow (sMBF)) were calculated using HeartSee software. Coefficients of variance (COV), repeatability (RC), MBF, and image quality metrics were compared.

Results: rMBF correlated well between F and S profiles, with intraclass correlation coefficients (ICC) ranging .91-.93. sMBF was highly correlated between F and S profiles (ICC = .97). Fast and slow profiles were associated with similar same-day test-retest precision (COV 11.5% vs 11.3% (P = .77); RC 21.5% vs 22.6%, for F-F vs S-S). There were no clinically significant differences in MBF values between F and S profiles. Image quality metrics were similar between the 2 profiles.

Conclusions: There are no clinically significant differences in precision, perfusion metrics, or image quality between Rb-82 fast and slow infusions using a contemporary analog 3D PET-CT.

Background: Cardiac imaging with bone-avid tracers for the diagnosis of transthyretin amyloid (ATTR) cardiac amyloidosis uses only limited quantification, but single-photon emission computed tomography/computed tomography (SPECT/CT) acquisition can provide volumetric assessment with quantification of tracer uptake. Tafamidis is routinely used in the treatment of cardiac amyloidosis, but there are scant data on changes in imaging results during therapy. The purpose of this study was to perform a longitudinal assessment of Tc-99m-pyrophosphate (PYP) imaging to determine if tafamidis therapy results in any change in quantitative measures of tracer uptake.

Methods: The study incorporated a prospective, single-center study of ATTR patients being treated with tafamidis using Tc-99m-PYP SPECT/CT to quantify cardiac tracer uptake in the whole heart and left ventricle. Standardized uptake values (SUVs) were adjusted for blood pool activity. Comparison of baseline activity was made to values obtained approximately every 6 months during treatment.

Results: Twenty-two patients (77.0±7.5 years old, 86.4% male) were on tafamidis for 15.3±4.0 months, with an average time between baseline and final follow-up study of 16.8±4.7 months. Thirteen patients (59.1%) had multiple follow-up amyloid studies. Statistically significant reductions in total SUVs, SUV volume, and percentage of injected dose were seen. Adjusted for the maximal aortic SUV, the total SUV in the left ventricle decreased by 36.9%, the SUV volume by 38.7%, and the percentage of injected dose decreased by 34.9% (all P values≤0.0001). Over the study duration, there was a decrease of 7.7%/month in the measured metrics.

Conclusion: The quantitative SUV measurements from Tc-99m-PYP SPECT/CT revealed an overall decrease in scintographic amyloid burden during the course of tafamidis therapy, but additional work is needed to determine the optimal metrics and improve the reproducibility of the quantification.

Background: The additional prognostic value of ^{18F-flurodeoxyglucose} positron emission tomography (¹⁸F-FDG PET) myocardial ischemic memory imaging for patients with suspected unstable angina (UA) is not well established. This study aimed to determine whether ¹⁸F-FDG PET imaging provides incremental prognostic information for predicting major adverse cardiac events (MACEs) compared to clinical risk factors, Global Registry of Acute Coronary Events (GRACE) score, and coronary artery calcium score (CACS) in patients with suspected UA.

Methods: In this post hoc analysis of a prospective study, 265 patients suspected with UA (62.3% male, mean age: 65.0±9.4 years) were enrolled. ¹⁸F-FDG positivity was defined as focal or focal on diffuse uptake patterns. MACEs included cardiovascular death, acute myocardial infarction, heart failure, rehospitalization for UA, and stroke. Multivariable Cox regression was used to identify predictors of MACEs, and the incremental prognostic value of ¹⁸F-FDG PET imaging was assessed using the Concordance Index (C-index), net reclassification improvement (NRI), and integrated discrimination improvement (IDI).

Results: Over a median follow-up of 25 months, 51 patients (19.2%) experienced MACEs. ¹⁸F-FDG positivity (hazard ratio [HR]=3.220, 95% confidence interval [CI]: 1.630-6.360, P<.001), as well as ¹⁸F-FDG standardized uptake ratio (HR=1.330, 95% CI: 1.131-1.564, P=.0006) and Extent (HR=1.045, 95% CI: 1.028-1.062, P<.0001), were independent predictors of MACE. The addition of ¹⁸F-FDG PET imaging significantly improved risk stratification beyond clinical factors, the GRACE score, and CACS, with improved C-index (.769 vs .688, P=.045), NRI (.324, P=.020), and IDI (.055, P=.027).

Conclusion: ¹⁸F-FDG PET myocardial ischemic memory imaging significantly improves prognostic assessment for patients with suspected UA, providing valuable additional risk stratification beyond clinical risk factors, GRACE score, and CACS.