A 3D printed pulmonary mock loop for hemodynamic studies in congenital heart disease.

Background. With the increasing survival of the congenital heart disease population, there is a growing need for in-depth understanding of blood circulation in these patients. Mock loops provide the opportunity for comprehensive hemodynamic studies without burden and risks for patients. This study aimed to evaluate the ability of the presented mock loop to mimic the hemodynamics of the pulmonary circulation with and without stenosis and the MR compatibility of the system.Methods. A pulsatile pump with two chambers, separated by a flexible membrane, was designed and 3D printed. A cough assist device applied an alternating positive and negative pressure on the membrane. One adult, and three pediatric pulmonary bifurcations were 3D printed and incorporated in the setup. Two pediatric models had a 50% stenosis of the left branch. Bilateral compliance chambers allowed for individual compliance tuning. A reservoir determined the diastolic pressure. Two carbon heart valves guaranteed unidirectional flow. The positive pressure on the cough assist device was tuned until an adequate stroke volume was reached with a frequency of 60 bpm. Flow and pressure measurements were performed on the main pulmonary artery and the two branches. The MR compatibility of the setup was evaluated.Results. A stroke volume with a cardiac index of 2 l min-1m-2was achieved in all models. Physiological pressure curves were generated in both normal and stenotic models. The mock loop was MR compatible.Conclusion.This MR compatible mock loop, closely resembles the pulmonary circulation thereby providing a controllable environment for hemodynamic studies.

Computational Analysis of the Pulmonary Arteries in Congenital Heart Disease: A Review of the Methods and Results.

With the help of computational fluid dynamics (CFD), hemodynamics of the pulmonary arteries (PA's) can be studied in detail and varying physiological circumstances and treatment options can be simulated. This offers the opportunity to improve the diagnostics and treatment of PA stenosis in biventricular congenital heart disease (CHD). The aim of this review was to evaluate the methods of computational studies for PA's in biventricular CHD and the level of validation of the numerical outcomes. A total of 34 original research papers were selected. The literature showed a great variety in the used methods for (re) construction of the geometry as well as definition of the boundary conditions and numerical setup. There were 10 different methods identified to define inlet boundary conditions and 17 for outlet boundary conditions. A total of nine papers verified their CFD outcomes by comparing results to clinical data or by an experimental mock loop. The diversity in used methods and the low level of validation of the outcomes result in uncertainties regarding the reliability of numerical studies. This limits the current clinical utility of CFD for the study of PA flow in CHD. Standardization and validation of the methods are therefore recommended.

Visual cerebral microbleed detection on 7T MR imaging: reliability and effects of image processing.

SUMMARY: MR imaging at 7T has a high sensitivity for cerebral microbleed detection. We identified mIP processing conditions with an optimal balance between the number of visually detected microbleeds and the number of sections on 7T MR imaging. Even with optimal mIP processing, the limited size of some of the microbleeds and the susceptibility effects of other adjacent structures were a challenge for visual detection, which led to a modest inter-rater agreement, mainly due to missed microbleeds. Automated lesion-detection techniques may be required to optimally benefit from the increased spatial resolution offered by 7T MR imaging.

Cerebral microbleeds on MR imaging: comparison between 1.5 and 7T.

BACKGROUND AND PURPOSE: The detection of microbleeds differs strongly between studies, due to differences in scan protocol. This study aims to compare the visualization of microbleeds with 3D T2*-weighted imaging at 1.5T with 3D dual-echo T2*-weighted imaging at 7T. MATERIALS AND METHODS: Thirty-four patients (29 male; mean age, 58 ± 12 years) with atherosclerotic disease from the Second Manifestations of ARTerial Disease study were included. 3D T2*-weighted imaging at 1.5T and dual-echo T2*-weighted imaging at 7T were done in all patients. The presence and number of definite microbleeds were recorded on minimal intensity projections. Inter- and intraobserver reliability was assessed with Cohen κ test and the ICC. The difference in presence and number of microbleeds was tested with the McNemar test and Wilcoxon signed rank test. RESULTS: The interobserver ICC at 7T was 0.61 and the intraobserver ICC was 0.94, whereas at 1.5T the interobserver ICC was 0.50 and the intraobserver ICC was 0.59. Microbleeds were detected in significantly more patients on 7T (50%) than on 1.5T scans (21%) (P = .001). The number of microbleeds was also higher at 7T (median, 0.5; range, 0-5) than on 1.5T (median, 0.0; range, 0-6) (P = .002). CONCLUSIONS: 3D dual-echo T2*-weighted imaging at 7T results in better and more reliable detection of microbleeds compared with 3D T2*-weighted imaging at 1.5T.