High-Speed On-Site Deep Learning-Based FFR-CT Algorithm: Evaluation Using Invasive Angiography as the Reference Standard

BACKGROUND. Estimation of fractional flow reserve from coronary CTA (FFR-CT) is an established method of assessing the hemodynamic significance of coronary lesions. However, clinical implementation has progressed slowly, partly because of off-site data transfer with long turnaround times for results. OBJECTIVE. The purpose of this study was to evaluate the diagnostic performance of FFR-CT computed on-site with a high-speed deep learning-based algorithm with invasive hemodynamic indexes as the reference standard. METHODS. This retrospective study included 59 patients (46 men, 13 women; mean age, 66.5 ± 10.2 years) who underwent coronary CTA (including calcium scoring) followed within 90 days by invasive angiography with invasive fractional flow reserve (FFR) and/or instantaneous wave-free ratio measurements from December 2014 to October 2021. Coronary artery lesions were considered to have hemodynamically significant stenosis in the presence of invasive FFR of 0.80 or less and/or instantaneous wave-free ratio of 0.89 or less. A single cardiologist evaluated the CTA images using an on-site deep learning-based semiautomated algorithm entailing a 3D computational flow dynamics model to determine FFR-CT for coronary artery lesions detected with invasive angiography. Time for FFR-CT analysis was recorded. FFR-CT analysis was repeated by the same cardiologist in 26 randomly selected examinations and by a different cardiologist in 45 randomly selected examinations. Diagnostic performance and agreement were assessed. RESULTS. A total of 74 lesions were identified with invasive angiography. FFR-CT and invasive FFR had strong correlation (r = 0.81) and, in Bland-Altman analysis, bias of 0.01 and 95% limits of agreement of -0.13 to 0.15. FFR-CT had AUC for hemodynamically significant stenosis of 0.975. At a cutoff of 0.80 or less, FFR-CT had 95.9% accuracy, 93.5% sensitivity, and 97.7% specificity. In 39 lesions with severe calcifications (≥ 400 Agatston units), FFR-CT had AUC of 0.991 and at a cutoff of 0.80, 94.7% sensitivity, 95.0% specificity, and 94.9% accuracy. Mean analysis time per patient was 7 minutes 54 seconds. Intraobserver agreement (intraclass correlation coefficient, 0.85; bias, -0.01; 95% limits of agreement, -0.12 and 0.10) and interobserver agreement (intraclass correlation coefficient, 0.94; bias, -0.01; 95% limits of agreement, -0.08 and 0.07) were good to excellent. CONCLUSION. A high-speed on-site deep learning-based FFR-CT algorithm had excellent diagnostic performance for hemodynamically significant stenosis with high reproducibility. CLINICAL IMPACT. The algorithm should facilitate implementation of FFR-CT technology into routine clinical practice.

Radiomics for the detection of diffusely impaired myocardial perfusion: A proof-of-concept study using 13N-ammonia positron emission tomography

AIM

The current proof-of-concept study investigates the value of radiomic features from normal 13N-ammonia positron emission tomography (PET) myocardial retention images to identify patients with reduced global myocardial flow reserve (MFR).

METHODS

Data from 100 patients with normal retention 13N-ammonia PET scans were divided into two groups, according to global MFR (i.e., < 2 and ≥ 2), as derived from quantitative PET analysis. We extracted radiomic features from retention images at each of five different gray-level (GL) discretization (8, 16, 32, 64, and 128 bins). Outcome independent and dependent feature selection and subsequent univariate and multivariate analyses was performed to identify image features predicting reduced global MFR.

RESULTS

A total of 475 radiomic features were extracted per patient. Outcome independent and dependent feature selection resulted in a remainder of 35 features. Discretization at 16 bins (GL16) yielded the highest number of significant predictors of reduced MFR and was chosen for the final analysis. GLRLM_GLNU was the most robust parameter and at a cut-off of 948 yielded an accuracy, sensitivity, specificity, negative and positive predictive value of 67%, 74%, 58%, 64%, and 69%, respectively, to detect diffusely impaired myocardial perfusion.

CONCLUSION

A single radiomic feature (GLRLM_GLNU) extracted from visually normal 13N-ammonia PET retention images independently predicts reduced global MFR with moderate accuracy. This concept could potentially be applied to other myocardial perfusion imaging modalities based purely on relative distribution patterns to allow for better detection of diffuse disease.

Simplifying the World Health Organization Protocol: 3 Steps Versus 6 Steps for Performance of Hand Hygiene in a Cluster-randomized Trial

BACKGROUND

In an experimental setting, a simplified, 3-step hand hygiene technique for applying alcohol-based hand rub was non inferior in terms of reduction of bacterial counts, as compared to the conventional World Health Organization 6-step technique. We therefore compared compliance and microbiological efficacy between both hand hygiene techniques in routine clinical practice.

METHODS

We performed a cluster-randomized trial from October-November 2015 at the University Hospital Basel, Switzerland: a tertiary, academic care center (ISRCTN45923734). We randomly assigned 12 wards to either the 3-step technique or the conventional 6-step technique of hand rubbing. The primary endpoints were compliance with the assigned technique and reduction of bacterial counts on the hands of health-care workers.

RESULTS

Overall, 2923 hand hygiene indications were observed, and compliance was 70.7% (2066/2923). Compliance with technique and indications was 51.7% (595/1151) and 75.9% (1151/1516) on wards assigned to the 3-step technique, respectively, as compared to 12.7% (116/915) and 65.0% (915/1407) on wards assigned to the 6-step technique (P < .001). The reduction factor (RF) of bacterial colony counts did not differ between techniques (median RF 0.97 log10 colony-forming units [CFU] [interquartile range 0.39-1.59] for the 3-step technique vs median RF 1.04 log10 CFU [interquartile range 0.49-1.52] for the 6-step technique; P = .629).

CONCLUSIONS

In a clinical setting, the simpler hand hygiene technique, consisting of 3 steps, resulted in higher compliance with both hand hygiene indications and technique, as compared to the 6 steps. As the results of the microbiological analyses exclude inferiority, the conventional 6 steps could be safely replaced by a simpler hand hygiene technique.

CLINICAL TRIALS REGISTRATION

ISRCTN45923734.

Methodological and metrological issues in the evaluation of noise pollution indicators in residential environment

With regard to differential noise measurements in residential environment, as regulated by Italian law 'DM 16 marzo '98', various factors influencing the dispersion of results and measurement uncertainty are taken into account, and some aspects that can weigh on the usefulness of these measurements for compliance assessment are put in evidence.