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The Instantaneous Signal Loss Simulation (InSiL) model is a promising alternative to the classical mono-exponential fitting of the Modified Look-Locker Inversion-recovery (MOLLI) sequence in cardiac T1 mapping applications, which achieves better accuracy and is less sensitive to heart rate (HR) variations. Classical non-linear least squares (NLLS) estimation methods require some parameters of the model to be fixed a priori in order to give reliable T1 estimations and avoid outliers. This introduces further bias in the estimation, reducing the advantages provided by the InSiL model. In this paper, a novel Bayesian estimation method using a hierarchical model is proposed to fit the parameters of the InSiL model. The hierarchical Bayesian modeling has a shrinkage effect that works as a regularizer for the estimated values, by pulling spurious estimated values toward the group-mean, hence reducing greatly the number of outliers. Simulations, physical phantoms, and in-vivo human cardiac data have been used to show that this approach estimates accurately all the InSiL parameters, and achieve high precision estimation of the T1 compared to the classical MOLLI model and NLLS InSiL estimation.

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Background: Left atrial automated functional myocardial imaging (AFILA) is a new software program for analyzing the structure and function of the left atrium (LA). The present study sought to analyze the correlation between the LA function parameters as measured by AFILA echocardiography and the risk of cerebral ischemic stroke (CIS) in patients with non-valvular paroxysmal atrial fibrillation (NVPAF) to explore the diagnostic value of LA strain in patients with congestive heart failure, hypertension, age of ≥75 years (doubled), diabetes mellitus, stroke or transient ischemic attack (TIA) (doubled), age of 65-74 years, and sex category (female) (CHA2DS2-VASc) scores of <2. Methods: A total of 205 patients with NVPAF were included in the study and divided into the no-CIS group (154 patients) and the CIS group (51 patients). The baseline clinical data for the 2 groups were analyzed, and routine echocardiography examinations were performed. AFILA was used to evaluate the LA function of all the patients. Results: Compared to the no-CIS group, the LA emptying fraction and the LA reservoir strain were decreased, the LA contractile strain (S_CT) was increased, and the S_CT value changed from negative to positive in the CIS group, and the difference between the 2 groups were statistically significant (P<0.001). However, there were no significant differences in the volume at the onset of LA contraction, LA evacuation volume, LA minimum volume, LA maximum volume, and LA conduit strain between the 2 groups. The multifactorial regression analysis showed that age, hypertension, and the S_CT were independently associated risk factors for patients with CIS. After correcting for the clinical factors included in the CHA2DS2-VASc score, the S_CT was shown to predict to NVPAF with stroke [odds ratio (OR): 1.234, 95% confidence interval (CI): 1.101-1.383, P=0.000]. In addition, we included the CHA2DS2-VASc score (instead of age, diabetes, coronary artery disease, and hypertension) in a multiple regression analysis, and found that the S_CT was still significant (OR: 1.252, 95% CI: 1.118-1.402, P=0.000). The difference between the 2 groups in the CHA2DS2-VASc score for the S_CT was statistically significant, especially when the CHA2DS2-VASc score was <2. The S_CT equaled -4.5% was the cut-off value for the presence or absence of CIS in the NVPAF patients, with an area under the curve (AUC) of 0.866, sensitivity of 0.80, and specificity of 0.75 (P<0.0001). Conclusions: Comparison with LA volume parameter, measuring LA strain by AFILA provides a better index for the dynamic assessment of impaired LA function in patients with NVPAF combined with CIS, especially in those with a CHA2DS2-VASc score of <2. In addition, a LA S_CT of >-4.5% is a valuable cut-off for patients with NVPAF. The results of the current study may form the basis for a large prospective multicenter interventional study in which patients with impaired LA S_CT are randomized to receive oral anti-coagulant (OAC) therapy or no OAC therapy for the primary prevention of stroke.

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Metaiodobenzylguanidine (MIBG) is an analog of norepinephrine that accumulates in sympathetic nerve endings soon after intravenous administration. The degree of accumulation reflects the uptake, storage and release of transmitters by noradrenergic neurons. Myocardial imaging with 123I labeled MIBG ( 123I-MIBG) can be used to estimate the extent of local myocardial sympathetic nerve damage, which has been widely used in the diagnosis and treatment of various heart diseases. In recent years, numerous studies have been carried out on the application of 123I-MIBG in the diagnosis of degenerative diseases of the nervous system (such as Parkinson's disease and dementia of Lewy body), and have made some achievements. The purpose of this review is to summarize the current clinical application of 123I-MIBG myocardial imaging in the diagnosis of dementia with Lewy bodies, the problems in imaging technology and the possible research directions in the future, so as to provide valuable reference information for clinicians to reasonably and accurately apply this technology in the early diagnosis and discrimination of dementia.

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BACKGROUND: Single-shot balanced steady-state free precession (bSSFP) sequence is widely used in cardiac imaging. However, the limited scan time in one heartbeat greatly hinders its spatial resolution compared to the segmented acquisition mode. Therefore, a highly accelerated single-shot bSSFP imaging technology is needed for clinical use. PURPOSE: To develop and evaluate a wave-encoded bSSFP sequence with high acceleration rates for single-shot myocardial imaging. METHODS: The proposed Wave-bSSFP method is implemented by adding a sinusoidal wave gradient in the phase encoding direction during the readout of bSSFP sequence. Uniform undersampling is used for acceleration. Its performance was first validated via phantom studies by comparison with conventional bSSFP. Then it was evaluated in volunteer studies via anatomical imaging, T2 -prepared bSSFP, and T1 mapping in in-vivo cardiac imaging. All methods were compared with accelerated conventional bSSFP reconstructed using iterative SENSE and compressed sensing (CS), to demonstrate the advantage of wave encoding in suppressing the noise amplification and artifacts induced by acceleration. RESULTS: The proposed Wave-bSSFP method achieved a high acceleration factor of 4 for single-shot acquisitions. The proposed method showed lower average g-factors than bSSFP, and fewer blurring artifacts than CS reconstruction. The Wave-bSSFP with R = 4 achieved higher spatial and temporal resolutions compared with the conventional bSSFP with R = 2 in several applications such as T2 -prepared bSSFP and T1 mapping, and could be applied in systolic imaging. CONCLUSION: Wave encoding can be used to highly accelerate 2D bSSFP imaging with single-shot acquisitions. Compared with the conventional bSSFP sequence, the proposed Wave-bSSFP method can effectively reduce the g-factor and aliasing artifacts in cardiac imaging.

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BACKGROUND: Myocardial first-pass perfusion (FPP) imaging is a useful cardiac MRI method for the diagnosis of coronary artery disease. However, conventional 2D multislice FPP acquisitions usually have gaps between myocardium slices, which limits the overall assessment of myocardial ischemia. PURPOSE: To increase the anatomic coverage of myocardial FPP imaging at 3 T by implementing both autocalibrated multiband (MB) acquisition and k-t space acceleration with compress sensing (CS) reconstruction, without the need for additional reference scans. STUDY TYPE: Phantom and prospective human studies. PHANTOM/SUBJECTS: A T1MES (T1 Mapping and ECV Standardization in cardiovascular magnetic resonance) phantom and 20 subjects (12 healthy subjects and 8 patients, 10 males, age 42 ± 16 years). FIELD STRENGTH/SEQUENCE: A 3 T/saturation recovery prepared gradient echo sequence with contrast administration. ASSESSMENT: Phantom experiments were performed to compare the performance of autocalibrated MB-FPP with k-t acceleration using slice-GRAPPA and CS reconstructions. In vivo experiments were performed to compare the performance of conventional FPP (2.5× acceleration) with autocalibrated MB + CS-FPP (6× acceleration). In phantom experiments, the error maps were calculated. In in vivo experiments, the contrast ratio (CR) and blurring were quantitatively measured, while image quality, perceived signal-to-noise ratio (SNR), and artifact level were qualitatively graded by three cardiologists on a 4-point scale. STATISTICAL TESTS: Wilcoxon signed-rank test, paired t-test. A P value <0.05 was considered statistically significant. RESULTS: In phantom experiments, residual artifact was reduced using the MB + CS-FPP reconstruction method compared with using the MB + slice-GRAPPA reconstruction method. In in vivo experiments, the proposed autocalibrated MB + CS-FPP method demonstrated significantly higher CR (3.52 ± 0.78 vs 2.91 ± 0.81) and had significantly better perceived SNR (2.69 ± 0.29 vs 2.48 ± 0.31) compared to the conventional sequence. Compared with conventional FPP, MB + CS-FPP doubled the spatial coverage (MB + CS-FPP vs conventional FPP) without compromising the image quality (2.69 ± 0.26 vs 2.60 ± 0.30) or increasing the artifact level (2.60 ± 0.26 vs 2.52 ± 0.31). CONCLUSION: Autocalibrated MB + CS-FPP improved the myocardial coverage and achieved comparable image quality with the same spatial resolution and scan time as conventional FPP and is a promising technique for clinical myocardial perfusion imaging. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 3.

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Nuclear medicine specialty involves the administration of unsealed radioactive substances to patients to allow specific diagnostics and treatments using radiopharmaceuticals, radiotracers, and materials. Developing a radiopharmaceutical must involve considering and addressing some limitations such as its retention by unintended organs, which can influence patient and worker safety, imaging findings, and diagnostic and therapeutic accuracy. This paper presents data on the changing biodistribution, localization, stability, and accuracy patterns of radiopharmaceuticals by liposome encapsulation. METHODS: Data are presented for 5 male New Zealand white rabbits. They were injected intravenously with the 99mTc-liposomes encapsulated MIBI through a marginal ear vein, and whole-body images were acquired using a dual-head gamma camera. Cationic PEGylated liposomes were prepared using the conventional thin-film-hydration method. The liposomes were tested for particle size, zeta potential, high-performance-liquid-chromatography (HPLC), and toxicity. RESULTS: The liver activity was slightly greater than or equivalent to heart uptake, using 99mTcsestamibi, MIBI, without liposome as a reference. The absorbed doses in myocardium cells after injecting rabbits with 99mTc-MIBI labeled with free positive lower pH liposomes was greater than in the liver, whereas 99mTc labeled with encapsulated MIBI within positive liposomes showed a significantly higher heart-to-liver ratio. The heart-to-spleen activity uptake ratio in 99mTc-MIBI was higher than or equal to one but increased in 99mTc labeled with MIBI and free positive liposomes. Injecting rabbits with 99mTc labeled with encapsulated MIBI raised myocardium uptake to 2-4 times more than the spleen. Heart-to-bowel activity began to rise with 99m Tc-labeld-MIBI and liposomes. CONCLUSION: This study provides findings in radiopharmaceutical biodistribution using liposomal agents. Adding free liposomes using a pH gradient technique enhanced the uptake and localization of the radiotracer. However, tracer encapsulation during the formation of the liposomes showed even better specificity.

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Metaiodobenzylguanidine (MIBG) is an analog of norepinephrine that accumulates in sympathetic nerve endings soon after intravenous administration. The degree of accumulation reflects the uptake, storage and release of transmitters by noradrenergic neurons. Myocardial imaging with 123I labeled MIBG ( 123I-MIBG) can be used to estimate the extent of local myocardial sympathetic nerve damage, which has been widely used in the diagnosis and treatment of various heart diseases. In recent years, numerous studies have been carried out on the application of 123I-MIBG in the diagnosis of degenerative diseases of the nervous system (such as Parkinson's disease and dementia of Lewy body), and have made some achievements. The purpose of this review is to summarize the current clinical application of 123I-MIBG myocardial imaging in the diagnosis of dementia with Lewy bodies, the problems in imaging technology and the possible research directions in the future, so as to provide valuable reference information for clinicians to reasonably and accurately apply this technology in the early diagnosis and discrimination of dementia.

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BACKGROUND/AIM: Radiotherapy (RT) related myocardial changes were analyzed by deformation imaging echocardiography in this study. PATIENTS AND METHODS: Ninety-nine breast cancer patients were studied at baseline, after chemotherapy, after RT, and three years after RT (3Y). Eighty patients received RT only, and twenty patients had right-sided breast cancer. Echocardiography included cyclic variation of the integrated backscatter in the septum (sCV) and posterior wall (pCV), global longitudinal strain (GLS), and left ventricular ejection fraction (LVEF). RESULTS: In patients with left-sided breast cancer, sCV declined from 11.3±3.3 dB at baseline to 10.3±2.9 dB after RT (p=0.001). No changes were observed after chemotherapy (p=0.211) or in patients with right-sided breast cancer after RT (p=0.977). No other parameters declined after RT. The decline in sCV was independently associated with the left anterior descending coronary artery radiation dose (ß=-0.290, p=0.020). CONCLUSION: In contrast to other parameters, sCV correlated with heart radiation dose.

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P-wave terminal force in lead V1 (PTFV1) is a marker of increased left atrial (LA) overload. Whether PTFV1 is associated with left ventricular (LV) diastolic function remains undetermined. We tested the hypothesis that PTFV1 is associated with LV diastolic parameters derived from gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with no significant perfusion abnormalities.The study population included 158 patients with preserved ejection fraction and no significant perfusion abnormalities. The amplitude and duration of the P-wave negative phase in lead V1 were measured using an electrocardiogram, and PTFV1 was calculated. The peak filling rate (PFR) and one-third mean filling rate (1/3 MFR) were obtained as LV diastolic parameters using gated SPECT.PTFV1 showed a weak correlation with the LA volume index (r = 0.31; P < 0.001). Significant associations were observed between PTFV1 and PFR (r = -0.27; P < 0.001) and 1/3 MFR (r = -0.26; P = 0.001). A multivariate linear regression analysis showed that age (ß = -0.26; P < 0.001), LV end-diastolic volume index (ß = -0.27; P = 0.001), and PTFV1 (ß = -0.15; P = 0.036) were significant factors associated with PFR. Moreover, male gender (ß = -0.16; P = 0.041), LV mass index (ß = -0.17; P = 0.046), and PTFV1 (ß = -0.17; P = 0.022) were significant factors associated with the 1/3 MFR.PTFV1 is associated with LV diastolic function, as derived from gated SPECT in patients with no significant perfusion abnormalities.

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BACKGROUND: I-123 meta-iodobenzylguanidine (MIBG) imaging has long been employed to noninvasively assess the integrity of human norepinephrine transporter-1 and, hence, myocardial sympathetic innervation. Positron-emitting F-18 meta-fluorobenzylguanidine (MFBG) has recently been developed for potentially superior quantitative characterization. We assessed the feasibility of MFBG imaging of myocardial sympathetic innervation. METHODS: 16 patients were imaged with MFBG PET (30-minute dynamic imaging of chest, followed by 3 whole-body acquisitions between 30 minutes and 4-hour post-injection). Blood kinetics were assessed from multiple samples. Pharmacokinetic modeling with reversible 1- and 2-compartment models was performed. Kinetic rate constants were re-calculated from truncated datasets. All patients underwent concurrent MIBG SPECT. RESULTS: MFBG myocardial uptake was rapid and sustained; the mean standardized uptake value (SUV (mean ± standard deviation)) was 5.1 ± 2.2 and 3.4 ± 1.9 at 1 hour and 3-4-hour post-injection, respectively. The mean K1 and distribution volume (VT) were 1.1 ± 0.6 mL/min/g and 34 ± 22 mL/cm3, respectively. Both were reproducible when re-calculated from truncated 1-hour datasets (Intraclass Correlation Coefficient of 0.99 and 0.91, respectively). Spearman's ϱ = 0.86 between MFBG SUV and VT and 0.80 between MFBG PET-derived VT and MIBG SPECT-derived heart-to-mediastinum activity concentration ratio. CONCLUSION: MFBG is a promising PET radiotracer for the assessment of myocardial sympathetic innervation.

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The monocyte to high-density lipoprotein cholesterol (HDL-C) ratio has been considered to be a prognostic marker. Whether this ratio is associated with left ventricular (LV) diastolic function remains undetermined. We tested the hypothesis that the monocyte to HDL-C ratio is associated with LV diastolic parameters derived from gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with no significant perfusion abnormality.The study population included 196 patients with no significant perfusion abnormalities and preserved ejection fraction. The peak filling rate (PFR) and one-third mean filling rate (1/3 MFR) were obtained as LV diastolic parameters using gated SPECT. Monocyte counts and plasma HDL-C levels were also examined.Significant associations were observed between the monocyte to HDL-C ratio and PFR (r = -0.20; P = 0.005) and 1/3 MFR (r = -0.19; P = 0.009). Multivariate linear regression analysis was performed to determine factors associated with LV diastolic parameters. Age (ß = -0.27; P < 0.001), LV end-diastolic volume (ß = -0.19; P = 0.034), and monocyte to HDL-C ratio (ß = -0.15; P = 0.027) were determined to be significantly associated with PFR. Moreover, age (ß = -0.13; P = 0.007), LV mass index (ß = -0.18; P = 0.037), and the monocyte to HDL-C ratio (ß = -0.13; P = 0.045) were significantly associated with 1/3 MFR.These results demonstrated that the monocyte to HDL-C ratio is associated with LV diastolic function, as derived from gated SPECT in patients with no significant perfusion abnormality.

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BACKGROUND: Several studies have shown that aortic valve calcium (AVC) is associated with cardiovascular events. Furthermore, the extent of AVC is associated with adverse prognosis even in patients without significant aortic stenosis. We investigated the relationship between AVC and left ventricular (LV) diastolic parameters determined by gated single-photon emission computed tomography (SPECT) in patients with no evidence of ischaemic heart disease. METHODS: This study included 157 patients with no evidence of ischaemic heart disease who underwent both coronary computed tomography and gated SPECT. The AVC scores were calculated by the Agatston method, and peak filling rate (PFR) and one-third mean filling rate (1/3 MFR) were determined as LV diastolic parameters. RESULTS: There were 93 (59%) and 64 (41%) patients with and without AVC, respectively, and the AVC scores ranged from 0 to 1251. There was no significant difference in LV end-diastolic volume (EDV) (60 ± 18 vs 62 ± 25 mL, p = 0.52) or LV ejection fraction (67% ± 10% vs 66% ± 8%, p = 0.60) between the two groups. Patients with AVC had lower PFR (2.2 ± 0.5 vs 2.4 ± 0.5 EDV/s, p = 0.002) and 1/3 MFR (1.3 ± 0.3 vs 1.5 ± 0.4 EDV/s, p = 0.003) than those without AVC. Multivariate linear regression analysis showed that ln(AVC score + 1) was significantly associated with PFR and 1/3 MFR. CONCLUSION: In patients without evidence of ischaemic heart disease, the extent of AVC was inversely correlated with gated SPECT-derived parameters of LV diastolic function.

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AIM: Preterm births and respiratory distress syndrome (RDS) are associated with pulmonary vascular disease and altered myocardial function. We serially assessed up to 1 year of age the effects of RDS on global and regional myocardial function of preterm infants, compared to preterm and term controls using conventional echocardiography parameters, tissue Doppler velocities and deformation analysis. METHODS AND RESULTS: A total of 120 infants (30 preterm [PT] with RDS, 30 PT controls without RDS, and 60 term controls) underwent conventional and tissue Doppler echocardiography within 72 hours of birth, at corrected term age for the preterm infants, at 1 month corrected, and at 1 year corrected age. At birth, compared to preterm and term controls, the PT-RDS group had decreased right ventricular (RV) long-axis function, systolic velocity, peak systolic strain, shorter pulmonary arterial acceleration time (PAAT), and lower ratio of PAAT to RV ejection time (PAAT:RVET). Preterm infants had left ventricular (LV) diastolic dysfunction at birth (lower early diastolic myocardial velocity, mitral E velocity, and mitral E:A ratio), and reduced long-axis systolic velocities and shortening. Differences between groups disappeared by 1 month corrected age, except PAAT:RVET which remained lower in the PT-RDS group. At 1 year, RV function was normal in PT-RDS apart from systolic strain rate, and LV function was normal apart from lower stroke volume and shortening, relative to body weight. CONCLUSION: PT-RDS had lower left and right ventricular systolic and diastolic function at birth which improved over time, suggesting postnatal maturation of cardiac function and resolution of lung disease.

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It has been shown in several studies that coronary artery calcium (CAC) burden or CAC progression is associated with heart failure. We tested the hypothesis that the extent of CAC is associated with left ventricular (LV) diastolic parameters derived from gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with no evidence of myocardial ischemia.157 patients undergoing coronary computed tomography (CT), gated SPECT, and transthoracic echocardiography (TTE) were enrolled in this study. The CAC score was calculated according to the Agatston method. The peak filling rate (PFR) and the one-third mean filling rate (1/3MFR) were obtained as LV diastolic parameters.There were 139 patients with CAC and 18 patients without. The CAC score ranged from 0 to 4,976. There were no significant differences in the LV end-diastolic volume (LVEDV) (61 ± 21 mL versus 62 ± 22 mL, P = 0.79) and LV ejection fraction (LVEF) (66 ± 9% versus 68 ± 9%, P = 0.43). Patients with CAC had lower PFR than those without (2.2 ± 0.5 EDV/s versus 2.6 ± 0.7 EDV/s, P = 0.03). Multivariate linear regression analysis showed that ln (CAC score + 1) was significantly associated with PFR (ß = -0.20, P = 0.01) and 1/3MFR (ß = -0.18, P = 0.049).Our data suggest that the extent of CAC is inversely associated with LV diastolic parameters derived from gated SPECT independent of myocardial ischemia.

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BACKGROUND: The association between myocardial ischemia in high-risk patients with coronary calcium score (CCS) and high-sensitivity C-reactive protein (hs-CRP) is not well established. AIMS: We evaluated the correlation between hs-CRP, CCS, and myocardial ischemia in asymptomatic high-risk patients without known coronary artery disease (CAD). MATERIALS AND METHODS: We prospectively assessed 68 asymptomatic high-risk outpatients without known CAD. One-day rest-stress Tc-99m single-photon emission computed tomography (SPECT) myocardial perfusion imaging and multislice computed tomography were performed. Multivariate regression analysis was performed for the assessment of predictors of myocardial ischemia. Standard risk factors and hs-CRP values were analyzed. RESULTS: CCS >0 Agatston score was observed in 26 patients (46.4%). Seven patients had CCS between 10 and 99 AU, 8 patients between 100 and 400 AU, and 11 patients had CCS >400 AU. Mild ischemia was noted in 11 patients, moderate ischemia in 10 patients, and severe ischemia in 6 patients. Hs-CRP was >1 mg/L in 39 patients, of whom 8 patients had CCS >0, 13 patients had normal SPECT results, 6 patients had mild ischemia, and 12 patients had moderate and severe ischemia. Multivariate regression analysis showed independent predictors for increased CCS: low-density lipoprotein cholesterol (odds ratio [OR]: 2.891; P = 0.001); age >70 years (OR: 2.568; P = 0.001); and smoking (OR: 1.931; P = 0.001). We found hs-CRP to be an independent predictor of myocardial ischemia (OR: 4.145; 95% confidence interval: 1.398-7.471, P = 0.001). CONCLUSION: hs-CRP was an independent predictor of myocardial ischemia. hs-CRP might improve the selection of high-risk asymptomatic patients for myocardial SPECT imaging.

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Cardiac amyloidosis is associated with very high morbidity and mortality. Only if treated early, cardiac amyloidosis responds well to therapy, and early recognition with a full differential diagnostic workup including multimodality imaging is therefore critical at first presentation. Closely meshed clinical monitoring and imaging are indispensable to ensure optimal individualized treatment. (Level of Difficulty: Beginner.).

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123 I-Iodophenylpentadecanoic acid (IPPA) is a metabolic agent used in nuclear medicine for diagnosis of myocardial defects. Efforts are underway worldwide to develop a 99m Tc substitute of the above radiopharmaceutical for the aforementioned application. Herein, we report synthesis and biodistribution studies of 99m Tc labeled fatty acids (8, 11, and 15 carbons) obtained via "click chemistry" for its potential use in myocardial imaging. ω-Bromo fatty acids (8C/11C/15C) were synthetically modified at bromo terminal to introduce a heterocyclic triazole with glycine sidearm in a five step procedure. Modified fatty acids were subsequently radiolabeled with preformed [99m Tc(CO)3 ]+ synthon to yield the desired fatty acid complexes which were evaluated in Swiss mice. All the radiolabeled complexes were obtained with radiochemical purities >80%, as characterized by HPLC. Biodistribution studies of all three complexes in Swiss mice showed myocardial uptake of ~6-9% ID/g at 2 minutes post-injection, close to* I-IPPA (~9% ID/g). Complexes exhibited significant retention in the myocardium up to 30 minutes (~1% ID/g) but were lower to the standard agent (~7% ID/g). Similar uptake of activity in myocardium for the newly synthesized complexes in comparison to 125 I-IPPA along with favorable in vivo pharmacokinetics merits potential for the present "click" design of complexes for myocardial imaging.

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Myocardial perfusion imaging using positron emission tomography (PET) has several advantages over single photon emission computed tomography (SPECT). The recent advances in SPECT technology have shown promise, but there is still a large need for PET in the clinical management of coronary artery disease (CAD). Especially, absolute quantification of myocardial blood flow (MBF) using PET is extremely important. In spite of considerable advances in the diagnosis of CAD, novel PET radiopharmaceuticals remain necessary for the diagnosis of CAD because clinical use of current cardiac radiotracers is limited by their physical characteristics, such as decay mode, emission energy, and half-life. Thus, the use of a radioisotope that has proper characteristics and a proper half-life to develop myocardial perfusion agents could overcome these limitations. In this review, the current state of cardiac PET and a general overview of novel 18F or 68Ga-labeled radiotracers, including their radiosynthesis, in vivo characterization, and evaluation, are provided. The future perspectives are discussed in terms of their potential usefulness based on new image analysis methods and hybrid imaging.

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In the recent past, new ultrasound technologies, such as three-dimensional echocardiography and strain imaging echocardiography, raised up in clinical practice leading to a better assessment of cardiac morphology and performance. These tools may assess regional cardiac mechanics, detecting clinical and subclinical myocardial dysfunction in different settings such as ischemic heart disease, cardiomyopathies, and heart valve diseases. Interesting results derive from patients affected from hypertrophic cardiomyopathy (HCM). Particularly, the mentioned techniques are progressively redefining the role of echocardiography in diagnostic evaluation of HCM variants such as apical HCM, detection of the underlying conditions of increased wall thickness, assessment of subclinical myocardial impairment, and potentially refine risk stratification and prognosis. In this review, we describe the clinical uses of these methodologies and the perspective application in HCM patients.

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[11C]-S-methyl-16-thiopalmitic acid (a) was developed with excellent heart-to-background uptake ratios and higher retention in heart. Myocardial uptake and metabolism of the tracer is markedly higher CPT I dependent. When compared to [11C]-S-methyl-14-thiomyristic acid (b), [11C]-S-methyl-12-thiododecanoic acid (c) and [11C]-palmitate, a showed an early high uptake and a significantly slower late clearance in heart and a prolonged myocardial elimination half-life (30 min). Analysis of heart tissue and urine samples showed that a was metabolized via beta-oxidation in myocardium. Small animal PET images of the accumulation of a in the rat myocardium were clearly superior to [11C]-palmitate. These initial studies suggest that a could be a potentially useful clinical PET tracer to assess myocardial fatty acid metabolism.

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