Full feature selection for estimating KAP radiation dose in coronary angiographies and percutaneous coronary interventions.

In interventional cardiology (IC) the radiation dose variation is very significant, and its estimation has been difficult due to the complexity of the treatments. In order to tackle this problem, the aim of this study was to identify the most important demographic and clinical features to estimate Kerma-Area Product (KAP) radiation dose in coronary angiographies (CA) and percutaneous coronary interventions (PCI). The study was retrospective using clinical patient data from 838 CA and PCI procedures. A total of 59 features were extracted from the patient data and 9 different filter-based feature selection methods were used to select the most informative features in terms of the KAP radiation dose from the treatments. The selected features were then used in a support vector regression (SVR) model to evaluate their performance in estimating the radiation dose. The ten highest-ranking features were: (1) FN1AC (CA), (2) FN2BA (PCI), (3) weight, (4) post-stenosis 0%, (5) multi-vessel disease, (6) number of procedures 3, (7) pre-stenosis 100%, (8) American Heart Association (AHA) score C, (9) pre-stenosis 85% and (10) gender. The performance of the SVR model increased (mean squared error ≈ 450) with the number of features approximately up to 30 features. The identification of the most informative features for CA and PCI KAP is an important step in determining suitable complexity models for clinical practice. The highest-ranking features can be used as individual predictors of IC procedure KAP or can be incorporated into combined complexity score or different estimation models in the future.

CONTEMPORARY RADIATION DOSES IN INTERVENTIONAL CARDIOLOGY: A NATIONWIDE STUDY OF PATIENT SKIN DOSES IN FINLAND.

In contemporary interventional cardiology, for typical elderly patients, the most severe radiation-related harm to patients can be considered to come from skin exposures. In this paper, maximum local skin doses in cardiological procedures are explored with Gafchromic film dosimetry. Film and reader calibrations and reading were performed at the Secondary Standards Dosimetry Laboratory of the Radiation and Nuclear Safety Authority (STUK), and data were gathered from seven hospitals in Finland. As alert levels for early transient erythema, 200 Gycm2 kerma area product (KAP) and 2000 mGy air kerma levels for transcatheter aortic valve implantations (TAVI) procedures are proposed. The largest doses were measured in TAVI (4158.8 mGy) and percutaneous coronary interventions (PCI) (941.68 mGy). Accuracies of the GE DoseWatch and Siemens CareMonitor skin dose estimates were reasonable, but more results are needed to reliably assess and validate the tools' capabilities and reliabilities. Uncertainty of the Gafchromic dosimetry was estimated as 9.1% for a calibration with seven data points and 19.3% for a calibration with five data points.

CONTEMPORARY RADIATION DOSES IN INTERVENTIONAL CARDIOLOGY: A NATIONWIDE STUDY OF PATIENT DOSES IN FINLAND.

The amount of interventional procedures such as percutaneous coronary intervention (PCI), transcatheter aortic valve implantation (TAVI), pacemaker implantation (PI) and ablations has increased within the previous decade. Simultaneously, novel fluoroscopy mainframes enable lower radiation doses for patients and operators. Therefore, there is a need to update the existing diagnostic reference levels (DRLs) and propose new ones for common or recently introduced procedures. We sought to assess patient radiation doses in interventional cardiology in a large sample from seven hospitals across Finland between 2014 and 2016. Data were used to set updated national DRLs for coronary angiographies (kerma-air product (KAP) 30 Gycm2) and PCIs (KAP 75 cm2), and novel levels for PIs (KAP 3.5 Gycm2), atrial fibrillation ablation procedures (KAP 25 Gycm2) and TAVI (KAP 90 Gycm2). Tentative KAP values were set for implantations of cardiac resynchronization therapy devices (CRT, KAP 22 Gycm2), electrophysiological treatment of atrioventricular nodal re-entry tachycardia (6 Gycm2) and atrial flutter procedures (KAP 16 Gycm2). The values for TAVI and CRT device implantation are published for the first time on national level. Dose from image acquisition (cine) constitutes the major part of the total dose in coronary and atrial fibrillation ablation procedures. For TAVI, patient weight is a good predictor of patient dose.

Optimization of b-value distribution for biexponential diffusion-weighted MR imaging of normal prostate.

PURPOSE: To determine the optimal b-value distribution for biexponential diffusion-weighted imaging (DWI) of normal prostate using both a computer modeling approach and in vivo measurements. MATERIALS AND METHODS: Optimal b-value distributions for the fit of three parameters (fast diffusion Df, slow diffusion Ds, and fraction of fast diffusion f) were determined using Monte-Carlo simulations. The optimal b-value distribution was calculated using four individual optimization methods. Eight healthy volunteers underwent four repeated 3 Tesla prostate DWI scans using both 16 equally distributed b-values and an optimized b-value distribution obtained from the simulations. The b-value distributions were compared in terms of measurement reliability and repeatability using Shrout-Fleiss analysis. RESULTS: Using low noise levels, the optimal b-value distribution formed three separate clusters at low (0-400 s/mm2), mid-range (650-1200 s/mm2), and high b-values (1700-2000 s/mm2). Higher noise levels resulted into less pronounced clustering of b-values. The clustered optimized b-value distribution demonstrated better measurement reliability and repeatability in Shrout-Fleiss analysis compared with 16 equally distributed b-values. CONCLUSION: The optimal b-value distribution was found to be a clustered distribution with b-values concentrated in the low, mid, and high ranges and was shown to improve the estimation quality of biexponential DWI parameters of in vivo experiments.