| Abstract |
AIM
Aim of the present PhD Thesis is the evaluation of the performance of advanced ultrasound imaging, namely 4D STIC and 4D e-STIC (acquisition and reconstruction of 3D volumes with temporal information -4D- based on mechanical –STIC- or electronic-eSTIC- cross sectional sweep of fetal thoracic area by using Spatial Temporal Image Corellation-STIC technology) against conventional 2D imaging. We studied also the impact of gestational age (trimester) on the 4D STIC performance to document normal and abnormal anatomy. The PhD Thesis included four substudies to evaluate: a) feasibility and diagnostic accuracy of 4D STIC against 2D ultrasound imaging (and comparison between STIC and eSTIC) b) Direct comparison of STIC/eSTIC against 2D ultrasound imaging in terms of time required for each technique in both levels of fetal heart imaging (basic-extended basic and fetal echocardiogram), c) Comparison of 2dimensional measurments of cardiac structures (heart valves) by each technique (2D, STIC, eSTIC), d) evaluation of 4DSTIC as a teaching tool, allowing reconstruction of all recommended basic-extended basic fetal heart imaging and recognition of key features of normal anatomy in each plane, by physicians of various levels of expertise in fetal ultrasound imaging.
METHODS.
In order to address the main study hypothesis (4D STIC is equal or superior to 2D ultrasound fetal heart imaging) and evaluate factors that can influence its performance, the study included four sub-studies which followed an learning curve period: Learning Curve Period. During this period the key investigators (Observer 1. PhD Candidate S.P, obstetrician-fetal medicine expert, Observer 2. Co-Supervisor. I.G. pediatrician-pediatric/fetal cardiology expert) performed several 4D STIC volume acquisitions (Investigator 1) and off-line reconstructions (Investigator 2), with interim analysis, fine tuning and standardization of image acquisition presetings, up to a level of a satisfactory (best possible) and steady (as demonstrated in several subsequent interim analysis) performance. Sub-study 1. Direct comparison of fetal heart 4D Ultrasound Imaging (STIC): electronic (eSTIC) vs conventional (STIC) 4D image aquisisition. Pairs of B-Mode and Color Doppler STIC volumes were acquired sequentially by STIC and eSTIC in 33 obstetric scans (median gestational age 23 (range 13-31) weeks. 66 fetal heart volume pairs were blindly assessed by a fetal cardiologist. The reconstruction feasibility, motion or artifact presentation, the subjective image quality (4-level scale: 1-best to 4-non-diagnostic) and the final diagnosis were documented, enabling paired comparison of STIC and eSTIC in same subjects under same conditions. Sub-study 2. 2D vs 4D STIC fetal heart imaging feasibility. A total of 22 singleton pregnancies, median maternal age 30 (19-39) yrs, referred for fetal echocardiogram, at a median gestational age 25.3 wks (range 18-36, IQR: 22.2-29.5wks) have been consecutive evaluated by an expert fetal sonographer (Obs.1) and a fetal cardiologist (Obs.1). Each observer documented the time required for basic (Obs.1) and extended (Obs.2) fetal heart imaging. Acquisition of STIC and eSTIC (2D and color Doppler) volumes was also documented (Obs.1). Stored 4D volumes have been off-line analyzed regarding feasibility and reconstruction time for basic and extended fetal heart imaging (Obs.2), Sub-study 3. Comparison of 4D STIC and 2D fetal heart measurments. A total of 10 fetal echocardiograms of normal mid-term singleton pregnancies (median gestational age 22.6 wks, range 21.9-23.9wks) with stored 2D cine loops and STIC / eSTIC fetal heart 4D volumes (transverse acquisition plane) obtained by a single expert sonographer (Observer 1) have been retrospectively reviewed by the same observer. Linear 2D dimensions of mitral (MV), tricuspid (TV) in diastole, aortic (AoV) and pulmonary (PV) valve in systole were measured repeatedly (3 times) from a) 2D cine loops obtained by conventional fetal echocardiography (2D) and from 4D volumes obtained during b) STIC and c) e-STIC 4D fetal echocardiography. Intraobserver variability for each set of measurements and each mode has been assessed (ICC: intraclass correlation coefficient), average measurements have been compared for significant differences (related samples Friedman’s test) and the regression of STIC and eSTIC values against each other and 2D values has been assessed. Sub-study 4. 4D STIC in Basic Fetal Heart Imaging Teching. Documentation of the first structured teaching of basic and extended basic routine fetal heart imaging, based on visual evaluation of reconstructed 4D fetal heart volumes (4D STIC), during the summer school entitled “Introduction in 4D Fetal Echocardiography”, School of Medicine, University of Crete, Heraklion 12-16th September 2022, organized by the PhD Thesis research team. Participants were 27 certified physicians and trainees (66% PhD level), including obstetricians (52%) paediatricians (37%) cardiologists (7%) and one radiologist. Throught the course their ability to reconstruct and correctly interpret the recommended cross-sectional views of basic-extended basic fetal heart imaging was evaluated, while a quality evaluation of the seminar was performed by anonymized questionaires.
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Συγκριτική μελέτη της κλασικής υπερηχογραφίας δύο διαστάσεων (2D) με τις νεότερες υπερηχογραφικές τεχνικές τεσσάρων διαστάσεων (4D STIC) για την απεικόνηση της φυσιολογικής ανατομίας και την ανίχνευση της παθολογικής ανατομίας της εμβρυϊκής καρδιάς στο 1ο και στο 2ο τρίμηνο της εγκυμοσύνης
