Semi-quantitative evaluation of myocardial perfusion and left ventricular function: comparison between the standard Anger and novel CZT camera

Introduction: Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is a well-established technique for the diagnosis and risk stratification of patients with suspected or known coronary artery disease (CAD). Conventional Anger camera systems for SPECT imaging use sodium iodide crystals and parallel-hole collimators. The novel gamma cameras with semiconductor Cadmium-Zinc-Telluride (CZT) detectors directly convert radiation into electric signals, allowing an improvement in terms of image accuracy and acquisition time. Aim: We conducted a retrospective study to compare the ability of CZT camera (D-SPECT) with that of conventional SPECT in detecting myocardial perfusion and functional abnormalities in patients referred for clinical evaluation of suspected or known CAD at our institution using semi-quantitative analysis of myocardial perfusion and function. Methods: We analyzed 517 consecutive patients with suspected or known CAD underwent gated stress MPI for the assessment of myocardial ischemia at our institution. Linear regression was used to evaluate the correlations between SSS, SRS, EDV, ESV, LVEF and TPD, by D-SPECT versus conventional SPECT and differences between the two methods were assessed by Bland-Altman analysis. In patients with angiographic available data, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy for the detection of CAD (≥50% luminal narrowing) were calculated for conventional SPECT and D-SPECT. A p-value of less than 0.05 was considered as statistically significant. Results: In the overall study population, an excellent correlation between SSS, SRS and TPD, measured by conventional SPECT and by D-SPECT was observed (r=0.808, 0.915, 0.892, p< 0.001, respectively). In Bland-Altman analysis, the mean differences in SSS, SRS and TPD (conventional SPECT minus D-SPECT) were 1.3%, 0.55% and 0.54%, respectively. In 478 patients (92%) who successfully completed LV functional analysis with electrocardiogram-gated SPECT, linear regression analysis showed an excellent correlation between EDV, ESV and LVEF (r=0.911, 0.926, 0.820, p<0.001). In Bland-Altman analysis, the mean differences in EDV, ESV and LVEF (conventional SPECT minus D-SPECT) were -13%, -8% and 3.4%, respectively. In 86 patients with coronary angiography data available, conventional SPECT yields sensitivity and specificity of 95% and 75% respectively, while for D-SPECT sensitivity and specificity of 86% and 85% were recorded. No statistical differences in sensitivity and specificity have been observed between the two methods (p=0.12 and p=0.36, respectively). The diagnostic accuracy for conventional SPECT and D-SPECT was not different (88% and 84%, respectively, p=0.5). The PPV and NPV for conventional and D-SPECT were 88% and 84%, p=0.48 and 87% and 85%, p=0.8, respectively. Conclusions: The novel CZT camera provides excellent image quality, which is equivalent to standard myocardial SPECT, despite a short scan time of less than half the standard time. Quantitative measures of myocardial perfusion and function, obtained using normal limits specific for the new technology, correlated extremely well with respective conventional SPECT measures. These findings support the use of this technology in nuclear laboratories using various radiopharmaceutical and stress protocols, evaluating patient populations with suspected or known CAD

Prone-only SPECT myocardial perfusion imaging: An alternative standard in clinical practice?

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First basin-wide experimental results on N2-fixation in the open Mediterranean Sea.

Mediterranean Sea presents several biogeochemical anomalies compared to the global ocean. Unbalanced N budget, high nitrate/phosphate ratios in subsurface waters and light isotopic signals in particulate and dissolved nitrogen have suggested a relevant occurrence of N2-fixation. This study presents, for the first time, N2-fixation rate measurements in the open Mediterranean Sea on a basin scale during early summer, compared to one site in the North Atlantic. Very low rates (0.052?0.031 nmols N l-1d-1) were observed in all sub-regions of the Mediterranean, unlike the higher values measured in the North Atlantic surface waters (0.300?0.115 nmols N l-1d-1). No evidence of phosphate limitation emerges from this study. Low N2-fixation rates associated to light isotopic composition of PON (from -2.10 to 4.11?) suggest that other light N sources, different from atmospheric N2, fuel the Mediterranean ecosystem

Meningioma MRI radiomics and machine learning: systematic review, quality score assessment, and meta-analysis

Purpose To systematically review and evaluate the methodological quality of studies using radiomics for diagnostic and predictive purposes in patients with intracranial meningioma. To perform a meta-analysis of machine learning studies for the prediction of intracranial meningioma grading from pre-operative brain MRI. Methods Articles published from the year 2000 on radiomics and machine learning applications in brain imaging of meningioma patients were included. Their methodological quality was assessed by three readers with the radiomics quality score, using the intra-class correlation coefficient (ICC) to evaluate inter-reader reproducibility. A meta-analysis of machine learning studies for the preoperative evaluation of meningioma grading was performed and their risk of bias was assessed with the Quality Assessment of Diagnostic Accuracy Studies tool. Results In all, 23 studies were included in the systematic review, 8 of which were suitable for the meta-analysis. Total (possible range, −8 to 36) and percentage radiomics quality scores were respectively 6.96 ± 4.86 and 19 ± 13% with a moderate to good inter-reader reproducibility (ICC = 0.75, 95% confidence intervals, 95%CI = 0.54–0.88). The meta-analysis showed an overall AUC of 0.88 (95%CI = 0.84–0.93) with a standard error of 0.02. Conclusions Machine learning and radiomics have been proposed for multiple applications in the imaging of meningiomas, with promising results for preoperative lesion grading. However, future studies with adequate standardization and higher methodological quality are required prior to their introduction in clinical practice

Nitrogen fixation in the Mediterranean Sea

The Mediterranean Sea is an oligotrophic basin characterized by low nutrient levels and unusually high NO3/PO4 molar ratios in the deeper layers, that reach the maximum (N/P = 28) in the Eastern Mediterranean. An external nitrogen source needs to be claimed in order to explain the nitrogen excess. Pantoja et al. (2002) found that the 15N/14N natural abundance in particulate and in dissolved inorganic nitrogen display low values, suggesting an important role of a "light" nitrogen source. Two hypotheses can be invoked: (i) nitrogen compounds from atmospheric deposition and/or(ii)atmospheric molecular nitrogen throughout nitrogen fixation . During TRANSMED oceanographic cruise carried out in the framework of Italian project VECTOR(June 2007), N2 fixation experiments have been carried out all over the Mediterranean Sea and outside the Gibraltar Strait. Surprisingly, very low rates (< 0.10 nmol N2*l-1*d-1) have been observed in different areas of the basin, while higher values have been observed in Atlantic Ocean according with literature data. These preliminary results suggest a major role for nitrogen atmospheric deposition in shaping the NO3/PO4 anomaly of the basin. Pantoja, S., D. J. Repeta, J. P. Sachs, and D. M. Sigman (2002). Stable isotope constraints on the nitrogen cycle of the Mediterranean Sea water column, Deep Sea Res., Part I, 4, 1609- 1621

Prognostic value of coronary vascular dysfunction assessed by rubidium-82 PET/CT imaging in patients with resistant hypertension without overt coronary artery disease

Purpose: The identification of coronary vascular dysfunction may enhance risk stratification in patients with resistant hypertension (RH). We evaluated if impaired coronary vascular function, assessed by rubidium-82 (82Rb) positron emission tomography/computed tomography (PET/CT) imaging, is associated with increased cardiovascular risk in patients with hypertension without overt coronary artery disease (CAD). Methods: We studied 517 hypertensive subjects, 26% with RH, without overt CAD, and with normal stress-rest myocardial perfusion imaging at 82Rb PET/CT. The outcome end points were cardiac death, nonfatal myocardial infarction, coronary revascularization, and admission for heart failure. Results: Over a median of 38 months (interquartile range 26 to 50), 21 cardiac events (4.1% cumulative event rate) occurred. Patients with RH were older (p < 0.05) and had a higher prevalence of left ventricular hypertrophy (p < 0.001), a lower hyperemic myocardial blood flow (MBF), and myocardial perfusion reserve (MPR) (both p < 0.001) compared to those without. Conversely, coronary artery calcium content and baseline MBF were not different between patients with and without RH. At univariable Cox regression analysis, age, RH, left ventricular ejection fraction, coronary artery calcium score, and reduced MPR were significant predictors of events. At multivariable analysis, age, RH, and reduced MPR (all p < 0.05) were independent predictors of events. Patients with RH and reduced MPR had the highest risk of events and the major risk acceleration over time. Conclusion: The findings suggest that the assessment of coronary vascular function may enhance risk stratification in patients with hypertension

A Comparison among different machine learning pretest approaches to predict stress-Induced ischemia at PET/CT myocardial perfusion imaging

Traditional approach for predicting coronary artery disease (CAD) is based on demographic data, symptoms such as chest pain and dyspnea, and comorbidity related to cardiovascular diseases. Usually, these variables are analyzed by logistic regression to quantifying their relationship with the outcome; nevertheless, their predictive value is limited. In the present study, we aimed to investigate the value of different machine learning (ML) techniques for the evaluation of suspected CAD; having as gold standard, the presence of stress-induced ischemia by 82Rb positron emission tomography/computed tomography (PET/CT) myocardial perfusion imaging (MPI) ML was chosen on their clinical use and on the fact that they are representative of different classes of algorithms, such as deterministic (Support vector machine and Naïve Bayes), adaptive (ADA and AdaBoost), and decision tree (Random Forest, rpart, and XGBoost). The study population included 2503 consecutive patients, who underwent MPI for suspected CAD. To testing ML performances, data were split randomly into two parts: training/test (80%) and validation (20%). For training/test, we applied a 5-fold cross-validation, repeated 2 times. With this subset, we performed the tuning of free parameters for each algorithm. For all metrics, the best performance in training/test was observed for AdaBoost. The Naïve Bayes ML resulted to be more efficient in validation approach. The logistic and rpart algorithms showed similar metric values for the training/test and validation approaches. These results are encouraging and indicate that the ML algorithms can improve the evaluation of pretest probability of stress-induced myocardial ischemia

Linear discriminant analysis and principal component analysis to predict coronary artery disease

Coronary artery disease is one of the most prevalent chronic pathologies in the modern world, leading to the deaths of thousands of people, both in the United States and in Europe. This article reports the use of data mining techniques to analyse a population of 10,265 people who were evaluated by the Department of Advanced Biomedical Sciences for myocardial ischaemia. Overall, 22 features are extracted, and linear discriminant analysis is implemented twice through both the Knime analytics platform and R statistical programming language to classify patients as either normal or pathological. The former of these analyses includes only classification, while the latter method includes principal component analysis before classification to create new features. The classification accuracies obtained for these methods were 84.5 and 86.0 per cent, respectively, with a specificity over 97 per cent and a sensitivity between 62 and 66 per cent. This article presents a practical implementation of traditional data mining techniques that can be used to help clinicians in decision-making; moreover, principal component analysis is used as an algorithm for feature reduction

Prognostic value of heart rate reserve in patients with suspected coronary artery disease undergoing stress myocardial perfusion imaging

Background. Chronotropic incompetence is common in patients with cardiovascular disease and is associated with increased risk of adverse events. We assessed the incremental prognostic value of heart rate reserve (HRR) over stress myocardial perfusion single-photon emission computed tomography (MPS) findings in patients with suspected coronary artery disease (CAD). Methods. We studied 866 patients with suspected CAD undergoing exercise stress-MPS as part of their diagnostic program. The primary study endpoint was all-cause mortality. All patients were followed for at least 5 years. HRR was calculated as the difference between peak exercise and resting HR, divided by the difference of age-predicted maximal and resting HR and expressed as percentage. Results. During 7 years follow-up, 61 deaths occurred, with a 7% cumulative event rate. Patients experiencing death were older (P < .001), and had a higher prevalence of male gender (P < .001) and diabetes (P < .05). Patients with event also had lower values of HRR (65% ± 27% vs 73% ± 18%, P < .0001) and higher prevalence of stress-induced myocardial ischemia (25% vs 8%, P < .0001). Male gender, HRR and stress-induced ischemia were independent predictors of all-cause mortality (all P < .01). HRR improved the prognostic power of a model including clinical data and MPS findings, increasing the global v2 from 66 to 82 (P < .005). Conclusions. Chronotropic incompetence has independent and incremental prognostic value in predicting all-cause mortality in patients with suspected CAD undergoing exercise stress-MPS. Hence, the evaluation of HRR may further improve patients’ risk stratification