MBF Values Research Articles

Fast vs slow rubidium-82 infusion profiles and test-retest precision of myocardial perfusion using contemporary 3D cardiac analog PET-CT imaging.

BackgroundOn legacy 2D 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. MethodsNinety-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. ResultsrMBF correlated well between F and S profiles, with intraclass correlation coefficients (ICC) ranging 0.91-0.93. sMBF was highly correlated between F and S profiles (ICC=0.97). Fast and slow profiles were associated with similar same-day test-retest precision (COV 11.5% vs. 11.3% (p=0.77); 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. ConclusionsThere 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.

Validation of advanced hybrid SPECT/CT system using dynamic anthropomorphic cardiac phantom

ObjectiveMyocardial blood flow (MBF) assessment can provide incremental diagnostic and prognostic information and thus the validation of dynamic SPECT is of high importance. We recently developed a novel cardiac phantom for dynamic SPECT validation and compared its performance against the GE Discovery NM 530c. We now report its use for validation of a new hybrid SPECT/CT System featuring advanced cadmium zinc telluride (CZT) technology in a ring array detector design (StarGuide™, GE HealthCare).MethodsOur recently developed cardiac phantom with injected technetium-99m radiotracer was used to create physiological time activity curves (TACs) for the left ventricular (LV) cavity and the myocardium. The TACs allow the calculation of uptake rate (K1) and MBF. The StarGuide system was used to acquire and process the TACs, and these were compared to the TACs produced by the phantom and its mathematical model. Fifteen (15) experiments with different doses representing various MBF values were conducted, and a standard statistic tool was applied for significance.ResultsThe TACs produced by the StarGuide system had a significant correlation (p < 0.001) with the reference TACs generated by the phantom both for the LV (r = 0.94) and for the myocardium (r = 0.89). The calculated MBF difference between the system and the phantom was 0.14 ± 0.16 ml/min/g and the average relative absolute difference was 13.2 ± 8.1%. A coefficient of variance of ≤ 11% was observed for all MBF subranges. The regional uptake rate values were similar to the global one with a maximum difference of 5%.ConclusionsOur newly developed dynamic cardiac phantom was used for validation of the dynamic hybrid SPECT/CT CZT-based system (StarGuide™, GE). The accuracy and precision of the system for assessing MBF values were high. The new StarGuide system can reliably perform dynamic SPECT acquisitions over a wide range of myocardial perfusion flow rates.

Quantification of myocardial blood flow using stress cardiac magnetic resonance for the detection of coronary artery disease

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): GE Healthcare. Background Myocardial blood flow (MBF) analysis using stress cardiac magnetic resonance (CMR) has been shown to detect obstructive coronary artery disease (CAD); however, evaluation of its diagnostic performance has primarily been limited to single-center studies. AQUA-MBF (Assessment of QUAntitative MBF using stress CMR) is an international study with the goal of assessing the diagnostic performance of stress MBF for the detection of CAD. In this study, we aim to determine how stress MBF assessment compared against visual analysis (VA) of stress CMR images for the detection of CAD. Methods. 144 individuals (89 (62%) men, age 62±16 years, 97 (68%) hypertension, 54 (38%) diabetes, 92 (64%) hyperlipidemia) from 9 centers who underwent dual sequence stress CMR (1.5T or 3.0T GE Healthcare) and also had either a coronary computed tomography angiography (CTA, n=31), invasive coronary angiogram (ICA, n=95), or low pre-test probability for CAD (n=18) were included. CAD was defined as the presence of: (1) a stenosis ≥50% in the left main coronary artery or ≥70% in the 1 major vessel based on ICA or CTA or (2) an invasive fractional flow reserve (FFR) ≤ 0.8. Absence of obstructive coronary disease (NOCAD) was defined as a no history of myocardial infarction and stenosis &amp;lt;50% by ICA or CTA, 50–70% stenosis with FFR&amp;gt;0.8, or a young individual with no cardiac risk factors. Myocardial perfusion imaging was performed during first pass perfusion of a gadolinium-based contrast agent following the administration of adenosine or regadenoson with a low-resolution image acquired to assess the arterial input function and 2–3 short axis slices acquired to assess myocardial perfusion. VA was performed by 2 experienced cardiologists who assigned a grade of 1–5 based on the probability a study was abnormal. Stress MBF values were determined for each of the 16 myocardial segments using Fermi deconvolution (CircleCVI). The global stress MBF was calculated as the average value of two segments with the lowest values from each of the three coronary artery territories. Unpaired t-test was used to compare stress MBF values between CAD vs NOCAD. Receiver-operating characteristics curves were used to determine diagnostic performance. Results. 60 patients had CAD (20: 1-vessel, 26: 2-vessel, and 14: 3-vessel) (Figure 1A) while 84 had NOCAD (Figure 1B). The global stress MBF in CAD was lower than in NOCAD (1.63±0.52ml/g/min vs 2.41±0.68ml/g/min, p&amp;lt;0.0001) (Figure 2A). Stress MBF had a higher AUC than VA (reader 1 – 0.83 vs 0.73, p = 0.07: reader 2–0.83 vs 0.71, p = 0.02). The optimal stress MBF cut-off value for detecting CAD was 2.05ml/g/min (Figure 2B). Conclusions. In this multicenter study, we show that global stress MBF reported as a single value can identify patients with CAD at least as accurately as VA performed by physicians experienced in the interpretation of stress CMR images.

Diagnostic accuracy of dynamic stress myocardial ct perfusion as compared with invasive coronary physiology assessment in patients with suspected ISR or CAD progression: results of ADVANTAGE II study

Abstract Funding Acknowledgements Type of funding sources: None. Objectives To compare the diagnostic performance of regadenosone-stress dynamic myocardial perfusion assessed by CT (CTP) as compared with that of coronary CT angiography (CCTA) alone by using invasive fractional flow reserve (FFR) and index of microvascular resistance (IMR) as standard of reference. Background Diagnostic performance of CCTA for in-stent restenosis (ISR) detection is still challenging. Recently, CTP demonstrated additional specificity and diagnostic accuracy over CCTA alone in patients with previous stent implantation and suspected IRS or progression of coronary artery disease (CAD). However, no data are available in this clinical setting on the performance of CTP by using a new technique allowing for a non-invasive adjudication of regional myocardial blood flow (Dynamic CTP) and to assess both macrovascular and microvascular disease status. Methods We enrolled consecutive stable patients with previous coronary stenting referred for invasive quantitative coronary angiography (QCA) for clinical indication. All patients underwent dynamic stress myocardial CTP and rest CTP+CCTA by using a last generation scanner characterized by a 16-cm Z-axis coverage and fast (0.28 sec) gantry rotation time. Invasive FFR and IMR were performed during QCA according to the standard practice. The diagnostic rate and diagnostic accuracy of CCTA and CTP were evaluated in a territory-based analyses vs. FFR, IMR (primary endpoint of the study) and QCA (secundary endpoint). Results In 156 enrolled patients (126 men, mean age 63.1±8.2 years), the diagnostic rate (number of territories interpretable/number of territories evaluated) of CTP was significantly higher than that of CCTA (789/799=98.7% vs. 764/799=95.6%; p = 0.0002). The mean absolute MBF values for ischemic territories (pathological FFR and/or IMR) was significantly lower as compared with those for normal territories (96 ± 32 ml/100 g/min vs. 130 ± 46 ml/100 g/min; p&amp;lt; 0.0001). When FFR was used as gold standard, sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CTP were higher than those of CCTA (89%, 82.8%, 69.2%, 94.6% and 84.7% vs. 60%, 61.9%, 31.9%, 83.8% and 61.5%, p&amp;lt;0.001, respectively). When IMR was used as gold standard, sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CTP were higher than those of CCTA (76.5%, 85.9%, 72.2%, 88.4% and 82.9% vs. 48.2%, 63.5%, 33.3%, 76.4% and 59.3%, p&amp;lt;0.01, respectively). When the presence of at least one abnormal physiological parameter among FFR and IMR was used as gold standard, the diagnostic accuracy of CTP was higher than that of CCTA (90.8% vs. 68.1%, p&amp;lt;0.001). The mean ED of the total CCTA/rest CTP/stress CTP was 5.63±4.2 mSv. Conclusion In patients with coronary stents, dynamic CTP significantly improves diagnostic rate and accuracy of CCTA alone in comparison with both FFR and IMR.

Anthropomorphic cardiac phantom for dynamic SPECT

BackgroundAs myocardial blood flow measurement (MBF) in SPECT systems became recently available, significant effort has been devoted to its validation. For that purpose, we have developed a cardiac phantom that is able to mimic physiological radiotracer variation in the left ventricle cavity and in the myocardium, while performing beating-like motion. The new phantom is integrated inside a standard anthropomorphic torso allowing a realistic tissue attenuation and gamma-ray scattering Methods and ResultsA mechanical cardiac phantom was integrated in a commercially available anthropomorphic torso. Using a GE Discovery 530c SPECT, measurements were performed. It was found that gamma-ray attenuation effects are significant and limit the MBF measurements to global/three-vessel resolution. Dynamic SPECT experiments were performed to validate MBF accuracy and showed mean relative error of 14%. Finally, the effect of varying radiotracer dose on the accuracy of dynamic SPECT was studied ConclusionsA dynamic cardiac phantom has been developed and successfully integrated in a standard SPECT torso. A good agreement was found between SPECT-reported MBF values and the expected results. Despite increased noise-to-signal ratio when radiotracer doses were reduced, MBF uncertainty did not increase significantly down to very low doses, thanks to the temporal integration of the activity during the measurement

A Minimum Bayes Factor Based Threshold for Activation Likelihood Estimation

Activation likelihood estimation (ALE) is among the most used algorithms to perform neuroimaging meta-analysis. Since its first implementation, several thresholding procedures had been proposed, all referred to the frequentist framework, returning a rejection criterion for the null hypothesis according to the critical p-value selected. However, this is not informative in terms of probabilities of the validity of the hypotheses. Here, we describe an innovative thresholding procedure based on the concept of minimum Bayes factor (mBF). The use of the Bayesian framework allows to consider different levels of probability, each of these being equally significant. In order to simplify the translation between the common ALE practice and the proposed approach, we analised six task-fMRI/VBM datasets and determined the mBF values equivalent to the currently recommended frequentist thresholds based on Family Wise Error (FWE). Sensitivity and robustness toward spurious findings were also analyzed. Results showed that the cutoff log10(mBF) = 5 is equivalent to the FWE threshold, often referred as voxel-level threshold, while the cutoff log10(mBF) = 2 is equivalent to the cluster-level FWE (c-FWE) threshold. However, only in the latter case voxels spatially far from the blobs of effect in the c-FWE ALE map survived. Therefore, when using the Bayesian thresholding the cutoff log10(mBF) = 5 should be preferred. However, being in the Bayesian framework, lower values are all equally significant, while suggesting weaker level of force for that hypothesis. Hence, results obtained through less conservative thresholds can be legitimately discussed without losing statistical rigor. The proposed technique adds therefore a powerful tool to the human-brain-mapping field.

Attenuated niacin response is associated with a subtype of first-episode drug-naïve psychosis characterized as serious negative symptoms.

Although the phenomenon of attenuated niacin response (ANR) has been widely replicated in some patients with first-episode psychosis (FEP), its relevance to the negative symptoms (NS) of psychosis remains unclear. Total of 240 patients with drug-naïve FEP and 101 healthy controls (HCs) were recruited, and 209 were followed up for 1year. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), and niacin-induced responses were measured using laser Doppler flowmetry. We calculated the log-transform EC50 [concentration of methyl nicotinate required to elicit a half-maximal blood flow (MBF) response] and MBF values. Core-NS was generated by factor analysis of the PANSS-NS subscale and cluster analysis to produce subtypes. Significant differences were found in the log10 (EC50) values between the FEP and HC groups (p < 0.001), supporting the ANR in patients with FEP. A higher NS severity was found in the ANR subgroup than that in other patients. Factor analysis determined that a two-dimensional model included core NS and rigidity of thinking. The log10 (EC50) value was significantly associated with only the core NS. Cluster analysis revealed three subtypes-36.7% (cluster-1, n = 88), 16.7% (cluster-2, n = 40), and 46.7% (cluster-3, n = 112). Cluster-2 characterized by extensive NS appeared to have a moreremarkable ANR and less symptomatic improvement than those with other clusters during follow-up. No significant changes were found in the niacin response trajectories between the baseline and follow-up. Our findings indicate a significant correlation between ANR and core NS in patients with FEP. ANR may be a potential biomarker for certain subtypes with NS-dominated characteristics and poor symptomatic remission.

One-tissue compartment model for myocardial perfusion quantification with N-13 ammonia PET provides matching results: A cross-comparison between Carimas, FlowQuant, and PMOD

PurposeTo cross-compare three software packages (SPs)—Carimas, FlowQuant, and PMOD—to quantify myocardial perfusion at global, regional, and segmental levels. Materials and MethodsStress N-13 ammonia PET scans of 48 patients with HCM were analyzed in three centers using Carimas, FlowQuant, and PMOD. Values agreed if they had an ICC > 0.75 and a difference < 20% of the median across all observers. ResultsWhen using 1TCM on the global level, the agreement was good, and the maximum difference between 1TCM MBF values was 17.2% (ICC = 0.83). On the regional level, the agreement was acceptable except in the LCx region (25.5% difference, ICC = 0.74) between FlowQuant and PMOD. Carimas-1TCM agreed well with PMOD-1TCM and FlowQuant-1TCM. Values obtained with FlowQuant-1TCM had a somewhat lesser agreement with PMOD-1TCM, especially at the segmental level. ConclusionsThe global and regional MBF values (with one exception) agree well between the different software packages. There is significant variability in segmental values, mainly located in the LCx region and segments. Out of the studied tools, Carimas can be used interchangeably with both PMOD and FlowQuant for 1TCM implementation on all levels—global, regional, and segmental.

Quantitative myocardial perfusion parameters in subjects without coronary artery lesions based on computed tomography dynamic myocardial perfusion imaging

Objective: To determinate the range of quantitative myocardial perfusion parameters (MBF, MBV) in subjects without coronary artery lesions by dynamic computed tomography myocardial perfusion imaging (CTP). Methods: Subjects with occasional chest tightness or family history of coronary artery disease coming to Fuwai Hospital underwent coronary computed tomography angiography (CCTA) were prospectively enrolled. A total of 34 subjects [mean age (50±7) years, range from 33 to 65 years; 15 male and 19 female] were enrolled. Coronary lesions were not confirmed in any subjects using CCTA and volunteered for stress and rest dynamic CTP examination. MBF and MBV values were calculated in each myocardial segment using a 17-segment model. The global ranges of MBF and MBV were analyzed, and the gender variability and regional variability were compared. Results: The mean global MBF and MBV at rest and under stress were (115.5±27.4) ml·100 g-1·min-1, (212.8±40.8) ml·100 g-1·min-1 and (17.6±4.0) ml/100 g, (25.8±4.6) ml/100 g, respectively. The absolute and resolute reserves of MBF and MBV [(102.8±41.5) ml·100 g-1·min-1, 107.7%±52.5%; (9.3±5.2) ml/100 g, 62.1%±47.4%] were highest in the right coronary artery territory, but without any significant differences. The stress MBF and absolute reserve of MBF in females were higher than those of males [(228.6±39.9) ml·100 g-1·min-1, (113.3±46.2) ml·100 g-1·min-1; (192.8±33.4) ml·100 g-1·min-1, (77.0±41.2) ml·100 g-1·min-1] (both P<0.05). The MBF resolute reserve, rest MBV, stress MBV and MBV absolute and resolute reserves were higher in females, but without significant differences (all P>0.05). Conclusion: The mean global MBF and MBV at rest and under stress were (115.5±27.4) ml·100 g-1·min-1, (212.8±40.8) ml·100 g-1·min-1 and (17.6±4.0) ml/100 g, (25.8±4.6) ml/100 g. The MBF under stress perfusion and MBF absolute reserve of females are higher than those of males.

Evaluation of quantitative CMR perfusion imaging by comparison with simultaneous 15O-water-PET

BackgroundWe assessed the quantitative accuracy of cardiac perfusion measurements using dynamic contrast-enhanced MRI with simultaneous 15O-water PET as reference with a fully integrated PET-MR scanner. Methods15 patients underwent simultaneous DCE MRI and 15O-water PET scans at rest and adenosine-stress on an integrated PET-MR scanner. Correlation and agreement between MRI- and PET-based global and regional MBF values were assessed using correlation and Bland–Altman analysis. ResultsThree subjects were excluded due to technical problems. Global mean (± SD) MBF values at rest and stress were 0.97 ± 0.27 and 3.19 ± 0.70 mL/g/min for MRI and 1.02 ± 0.28 and 3.13 ± 1.16 mL/g/min for PET (P = 0.66 and P = 0.81). The correlations between global and regional MRI- and PET-based MBF values were strong (r = 0.86 and r = 0.75). The biases were negligible for both global and regional MBF comparisons (0.01 and 0.00 mL/min/g for both), but the limits of agreement were wide for both global and regional MBF, with larger variability for high MBF-values. ConclusionThe correlation between simultaneous MBF measurements with DCE MRI and 15O-water PET measured in an integrated PET-MRI was strong but the agreement was only moderate indicating that MRI-based quantitative MBF measurements is not ready for clinical introduction.

Effect of short-term smoking & L-arginine on coronary endothelial function assessed by cardiac magnetic resonance cold pressor testing: a pilot study

BackgroundThe effect of smoking on coronary vasomotion has been investigated in the past with various imaging techniques in both short- and long-term smokers. Additionally, coronary vasomotion has been shown to be normalized in long-term smokers by L-Arginine acting as a substrate for NO synthase, revealing the coronary endothelium as the major site of abnormal vasomotor response. Aim of the prospective cohort study was to investigate coronary vasomotion of young healthy short-term smokers via magnetic resonance cold pressor test with and without the administration of L-Arginine and compare obtained results with the ones from nonsmokers.MethodsMyocardial blood flow (MBF) was quantified with first-pass perfusion MRI on a 1.5 T scanner in healthy short-term smokers (N = 10, age: 25.0 ± 2.8 years, 5.0 ± 2.9 pack years) and nonsmokers (N = 10, age: 34.3 ± 13.6) both at rest and during cold pressor test (CPT). Smokers underwent an additional examination after administration of L-Arginine within a median of 7 days of the naïve examination.ResultsMBF at rest turned out to be 0.77 ± 0.30 (smokers with no L-Arginine; mean ± standard deviation), 0.66 ± 0.21 (smokers L-Arginine) and 0.84 ± 0.08 (nonsmokers). Values under CPT were 1.21 ± 0.42 (smokers no L-Arginine), 1.09 ± 0.35 (smokers L-Arginine) and 1.63 ± 0.33 (nonsmokers). In all groups, MBF was significantly increased under CPT compared to the corresponding rest examination (p < 0.05 in all cases). Additionally, MBF under CPT was significantly different between the smokers and the nonsmokers (p = 0.002). MBF at rest was significantly different between the smokers when L-Arginine was given and the nonsmokers (p = 0.035).ConclusionShort-term smokers showed a reduced response to cold both with and without the administration of L-Arginine. However, absolute MBF values under CPT were lower compared to nonsmokers independently of L-Arginine administration.

Automated Inline Analysis of Myocardial Perfusion MRI with Deep Learning.

PurposeTo develop a deep neural network–based computational workflow for inline myocardial perfusion analysis that automatically delineates the myocardium, which improves the clinical workflow and offers a “one-click” solution.Materials and MethodsIn this retrospective study, consecutive adenosine stress and rest perfusion scans were acquired from three hospitals between October 1, 2018 and February 27, 2019. The training and validation set included 1825 perfusion series from 1034 patients (mean age, 60.6 years ± 14.2 [standard deviation]). The independent test set included 200 scans from 105 patients (mean age, 59.1 years ± 12.5). A convolutional neural network (CNN) model was trained to segment the left ventricular cavity, myocardium, and right ventricle by processing an incoming time series of perfusion images. Model outputs were compared with manual ground truth for accuracy of segmentation and flow measures derived on a global and per-sector basis with t test performed for statistical significance. The trained models were integrated onto MR scanners for effective inference.ResultsThe mean Dice ratio of automatic and manual segmentation was 0.93 ± 0.04. The CNN performed similarly to manual segmentation and flow measures for mean stress myocardial blood flow (MBF; 2.25 mL/min/g ± 0.59 vs 2.24 mL/min/g ± 0.59, P = .94) and mean rest MBF (1.08 mL/min/g ± 0.23 vs 1.07 mL/min/g ± 0.23, P = .83). The per-sector MBF values showed no difference between the CNN and manual assessment (P = .92). A central processing unit–based model inference on the MR scanner took less than 1 second for a typical perfusion scan of three slices.ConclusionThe described CNN was capable of cardiac perfusion mapping and integrated an automated inline implementation on the MR scanner, enabling one-click analysis and reporting in a manner comparable to manual assessment.Published under a CC BY 4.0 license.Supplemental material is available for this article.

Evaluation of the masticatory biomechanical function in Down syndrome and its Influence on sleep disorders, body adiposity and salivary parameters

To evaluate the phenotypic features of the masticatory biomechanics in atypical subjects with Down syndrome (DS). Its influence was analysed on sleep disorders, body adiposity and its risks, and some physicochemical properties of saliva. Seventy subjects were enrolled to assess masticatory biomechanical function and divided into two groups: DS and control groups. Electrical activities of the masseter and temporal muscles (at rest and in maximum voluntary clench-MVC), maximum bite force-MBF and maximum mouth opening-MMO were investigated. Among the atypical subjects, just 24 participants underwent the anthropometry, the polysomnography II and the saliva testing (salivary flow rate-SFR, buffer capacity-BC and salivary cortisol levels, morning/SC-AM and night/SC-PM). MVC and MBF values showed high statistical significance in the control group (P<.001) than in the DS group of 35. MMO values were slightly increased in the DS group in relation to the control group. Overweight and obesity were found in both genders. Atypical women showed higher risk to develop cardiovascular-metabolic diseases than in atypical men. OSA severe was 20% for atypical women and 42.8% for atypical men, whereas snoring index was present in all genders. SFR was reduced in 100% of atypical subjects (hyposalivation in 10% women and 28.5% men). Furthermore, 100% BC, 66.6% SC-AM and 91.6% SC-PM showed normal patterns. Masseter and temporal muscle hypotonia was found in all atypical subjects with DS. This muscle dysfunction strongly was related to overweight/obesity, risks for development of cardiovascular/metabolic diseases, OSA severity, successive snoring episodes and salivary flow reduction in DS.

Relationship of non-invasive quantification of myocardial blood flow to arrhythmic events in patients with implantable cardiac defibrillators

BackgroundIschemia contributes to arrhythmogenesis though its role is incompletely understood. Abnormal myocardial perfusion measured by PET imaging may predict ventricular arrhythmias (VAs) in a high-risk population. MethodsPatients with implantable cardiac defibrillators who had undergone rubidium-82 cardiac PET imaging were identified. Patients were stratified by median MBF and MFR values for analysis. The Cox proportional hazards model was used to assess the impact of myocardial perfusion on survival free of VT independent of critical covariates. ResultsA total of 159 patients (124 (78%) males, median age 65.9 years, IQR [56.76-72.63]) were followed for 1.43 years IQR [0.83-2.21]. VA occurred in 29 patients (23.7%). After adjustment for ejection fraction, age, and sex, impaired stress MBF was associated with an increased risk of VA (adjusted HR per ml/min/g 1.52, 95% CI (1.01-2.31), P = 0.04). Summed rest and stress scores were not predictive of VA. Among patients with severe LV dysfunction, stress MBF remained an independent predictor of VA (adjusted HR per 1 ml/min/g HR 1.69, 95% CI (1.03-11.36), P = 0.03), while residual EF, summed rest, and summed stress scores were not (P > 0.05). ConclusionsImpaired stress myocardial blood flow was associated with less survival free of ventricular arrhythmias.

Evaluation of Maximum Bite Force in Patients with Complete Dentures.

OBJECTIVE:This study aimed to evaluate maximum bite forces (mBF) in dominant (DS) and non-dominant sides (NDS) at certain time periods after the insertion of new complete dentures based on prior experience and gender.MATERIALS AND METHODS:A total of 88 patients, complete denture wearers (CDWs), were examined. The maximum bite force at the intercuspal position between the first molars in 3 seconds was registered and recorded with piezoelectric gnathodynamometer. The procedure was repeated 3 times in identical conditions, with relaxation intervals of 1 minute between repeats and the limiting factor was the subjective feeling of pain. Testing of parametric data was performed with One Way Repeated Measurement of ANOVA test.RESULTS:The average mBF values increased during the observational period, both on the DS and NDS, with significant difference in DS, which was greater. The analysis of one-factor variance showed that there were differences of average mBF values in DS and NDS during six consecutive measurements (mBF–DS = 11.3, p = 0.0001, and mBF-NDS = 2.26, p = 0.047). Significant changes in the masticatory force (mBF) on the DS and NDS is explained by different measurement times and with the prior experience with complete dentures, BF–DS = 11.76, p = 0.0000; mBF–NDS = 2.42, p = 0.0351; mBFe–DS = 40.48; P = 0.0000 mBFe–NDS = 39.93, p = 0.0000.CONCLUSION:mBF represents a significant discriminating variable of the level of functional adaptation of new complete denture wearers (nCDWs) about the initial measurements.

The diagnostic value of dual source coronary CT angiography combined with dynamic CT myocardial perfusion imaging in coronary artery disease

Objective To evaluate the diagnostic value of one-stop cardiac CT (stress dynamic CT-MPI combining with CTA) in CAD. Methods Thirty patients underwent CCTA combined with stress dynamic CT-MPI and stress SPECT-MPI including 16 patients underwent ICA were retrospectively enrolled. All procedures were performed within 2 weeks without related treatment. CT-MPI and SPECT-MPI were evaluated visually and MBF was quantified according to dynamic CT-MPI which was compared through paired t test. The diagnostic value of CT-MPI for myocardial ischemia was evaluated with SPECT-MPI as the reference standard. The consistency between the two techniques was determined by Kappa test. With SPECT combined with ICA as the reference standard, we evaluated the value of CT-MPI and its combination with CCTA in the diagnosis of CAD with hemodynamic stenosis. Results On stress CT-MPI, 19 of 30 patients and 52 segments were evaluated with myocardial perfusion defects. There was a significant difference in MBF values between normal[(117.61±29.82)ml·100 ml-1·min-1] and hypoperfused [(80.60±22.15)ml·100 ml-1·min-1] segments (t=15.764,P<0.001). With SPECT as reference standard, the sensitivity, specificity were 94.12% (32/34), 95.80% (456/476) on the vessel basis. The Kappa value of the two examinations was 0.772(P<0.001). As for the 16 patients who also underwent ICA, 15 patients with 22 vessel-areas had hemodynamic stenosis on CT-MPI. Compared with SPECT combined with ICA, the sensitivity, specificity for detecting hemodynamic stenosis were 92.31% (12/13), 71.43% (25/35) for CT-MPI; 100% (13/13), 51.43% (18/35) for CTA and 92.31% (12/13), 82.86% (29/35) for CT-MPI combined with CTA, respectively. Moderate correlation was observed between the combination of CT-MPI and CCTA and reference standard (r=0.690, P<0.001). Conclusion Stress dynamic CT-MPI can detect myocardial perfusion defects and hemodynamic changes and improves the diagnostic ability of functional stenosis of CAD combined with CTA, which can finally achieve the one-stop mode of cardiac CT in CAD. Key words: Myocardial ischemia; Tomography, X-ray computed; Myocardial perfusion imaging; Coronary stenosis

Effect of Bayesian-penalized likelihood reconstruction on [13N]-NH3 rest perfusion quantification

ObjectivesMyocardial blood flow (MBF) imaging is used in patients with suspected cardiac sarcoidosis, and also in stress/rest studies. The accuracy of MBF is dependent on imaging parameters such as new reconstruction methodologies. In this work, we aim to assess the impact of a novel PET reconstruction algorithm (Bayesian-penalized likelihood—BPL) on the values determined from the calculation of [13N]-NH3 MBF values. MethodsData from 21 patients undergoing rest MBF evaluation [13N]-NH3 as part of sarcoidosis imaging were retrospectively analyzed. Each scan was reconstructed with a range of BPL coefficients (1-500), and standard clinical FBP and OSEM reconstructions. MBF values were calculated via an automated software routine for all datasets. ResultsReconstruction of [13N]-NH3 dynamic data using the BPL, OSEM, or FBP reconstruction showed no quantitative differences for the calculation of territorial or global MBF (P = .97). Image noise was lower using OSEM or BPL reconstructions than FBP and noise from BPL reached levels seen in OSEM images between B = 300 and B = 400. Intrasubject differences between all reconstructions over all patients in respect of all cardiac territories showed a maximum coefficient of variation of 9.74%. ConclusionQuantitation of MBF via kinetic modeling of cardiac rest MBF by [13N]-NH3 is minimally affected by the use of a BPL reconstruction technique, with BPL images presenting with less noise.

Shared versus non-shared prepulse perfusion MR sequence in absolute myocardial perfusion quantification

Methods In this substudy of the NOMI-trial (ClinicalTrials.gov identifier: NCT01398384), quantitative perfusion analysis was compared between patients that underwent an MR first pass perfusion sequence with a shared (n=25) and a non-shared prepulse (n=25), at 4 months after revascularized myocardial infarction. Perfusion imaging consisted of 3 short-axis slices acquired every heartbeat, with a balanced turbo gradient echo sequence in a 1.5 tesla MR unit (Achieva, Philips Medical Systems, The Netherlands) and was performed at rest and during adenosine (140 μg/kg/min) stress. MBF was quantified using Fermi deconvolution with a single bolus (SB, 0.05 mmol/kg) and dual bolus (DB, equal volumes of 0.0027 mmol/kg followed by 0.05 mmol/kg of contrast agent) analysis technique, in 6 segments of basal and midventricular short axis slices. Apical segments and segments with infarct scar on the corresponding late gadolinium enhancement-images were excluded. Results Baseline characteristics of both patient groups were comparable. MBF values were significantly higher with SP than with NSP sequence for the SB analysis technique. For DB, MBF was not different for rest perfusion,

Quantification of myocardial blood flow with cardiovascular magnetic resonance throughout the cardiac cycle.

BackgroundMyocardial blood flow (MBF) varies throughout the cardiac cycle in response to phasic changes in myocardial tension. The aim of this study was to determine if quantitative myocardial perfusion imaging with cardiovascular magnetic resonance (CMR) can accurately track physiological variations in MBF throughout the cardiac cycle.Methods30 healthy volunteers underwent a single stress/rest perfusion CMR study with data acquisition at 5 different time points in the cardiac cycle (early-systole, mid-systole, end-systole, early-diastole and end-diastole). MBF was estimated on a per-subject basis by Fermi-constrained deconvolution. Interval variations in MBF between successive time points were expressed as percentage change. Maximal cyclic variation (MCV) was calculated as the percentage difference between maximum and minimum MBF values in a cardiac cycle.ResultsAt stress, there was significant variation in MBF across the cardiac cycle with successive reductions in MBF from end-diastole to early-, mid- and end-systole, and an increase from early- to end-diastole (end-diastole: 4.50 ± 0.91 vs. early-systole: 4.03 ± 0.76 vs. mid-systole: 3.68 ± 0.67 vs. end-systole 3.31 ± 0.70 vs. early-diastole: 4.11 ± 0.83 ml/g/min; all p values <0.0001). In all cases, the maximum and minimum stress MBF values occurred at end-diastole and end-systole respectively (mean MCV = 26 ± 5%). There was a strong negative correlation between MCV and peak heart rate at stress (r = −0.88, p < 0.001). The largest interval variation in stress MBF occurred between end-systole and early-diastole (24 ± 9% increase). At rest, there was no significant cyclic variation in MBF (end-diastole: 1.24 ± 0.19 vs. early-systole: 1.28 ± 0.17 vs.mid-systole: 1.28 ± 0.17 vs. end-systole: 1.27 ± 0.19 vs. early-diastole: 1.29 ± 0.19 ml/g/min; p = 0.71).ConclusionQuantitative perfusion CMR can be used to non-invasively assess cyclic variations in MBF throughout the cardiac cycle. In this study, estimates of stress MBF followed the expected physiological trend, peaking at end-diastole and falling steadily through to end-systole. This technique may be useful in future pathophysiological studies of coronary blood flow and microvascular function.

Feasibility and operator variability of myocardial blood flow and reserve measurements with 99mTc-sestamibi quantitative dynamic SPECT/CT imaging

PurposeMyocardial blood flow (MBF) quantification with dynamic SPECT could lead to widespread utilization of MBF imaging in clinical practice with little cost increase over current standard SPECT myocardial perfusion imaging. This work evaluates the feasibility and operator-dependent variability of MBF and flow reserve measurements with 99mTc-sestamibi (MIBI) dynamic SPECT imaging using a standard dual-head SPECT camera. MethodsTwenty-eight patients underwent dipyridamole-stress and rest imaging with dynamic SPECT/CT acquisition. Quantitative images were iteratively reconstructed with all physical corrections and then myocardial and arterial blood regions of interest (ROI) were defined semi-automatically. A compartmental model was fitted to these ROI-sampled time-activity-curves, and flow-dependent MIBI extraction correction was applied to derive regional MBF values. Myocardial flow reserve (MFR) was estimated as stress/rest MBF ratio. MBF and MFR in low and high risk populations were evaluated for ability to detect disease. Images were each processed twice (≥7 days apart) by one expert and one novice operator to evaluate intra- and inter-operator variability of MBF and MFR measurement in the three coronary artery vascular territories. ResultsMean rest flow, stress flow, and MFR values were 0.83, 1.82 mL·minute−1·g−1, and 2.45, respectively. For stress/rest MFR, the inter-operator reproducibility was r2 = 0.86 with RPC = 1.1. Stress MBF and MFR were significantly reduced (P < .05) in high risk (n = 9) vs low risk populations (n = 19), indicating ability to detect disease. For expert and novice operators very good intra-operator correlations of r2 = 0.98 and 0.95 (n = 168, P < .001) were observed for combined rest and stress regional flow values. Bland-Altman reproducibility coefficients (RPC) were 0.25 and 0.47 mL·minute−1·g−1 for the expert and novice operators, respectively (P < .001). Inter-operator correlation was r2 = 0.91 and Bland-Altman RPC = 0.58 mL·minute−1·g−1 (n = 336). ConclusionsMBF and reserve measurements using 99mTc-sestamibi on a traditional, two-headed camera with fast rotation and with quantitative dynamic SPECT appears to be feasible, warranting further investigation.