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Title: Creation of a new fetal biometry image quality scoring tool to improve the accuracy of fetal biometric measurements
Author: Sarris, Ippokratis
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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The hypothesis of this work is that through establishing the background variation of ultrasonographic fetal biometry measurements and elucidating the parameters that influence these measurements, a new Fetal Ultrasound Biometry Quality (FUB-Q) image-scoring tool can be created which will be reproducible and able to quantify the accuracy of fetal measurements. Six studies are included, each answering a specific research question. The aim of the first study was to ascertain whether pre-existing image quality scoring methods reflect measurement accuracy and reproducibility. It demonstrated that during the course of an exercise where there was demonstrable improvement in the consistency of measurements performed - by a group of sonographers, this was not mirrored by the pre-existing image scoring system. The aim of the second study was to establish the intra- and inter- observer variability of fetal biometry measurements throughout pregnancy by expert sonographers. This study demonstrated that ultrasound variability of fetal biometry increases with advancing gestation when expressed in measurement values, but is constant as a percentage of the fetal dimensions or when reported as a z score. Calliper placement was the major component of the overall variability. The values from this study served as the background variability, "reference standard", for the FUB-Q tool. The third study had two aims. The first was to establish how 3D scanning performs compared to conventional, real-time, 20. The second aim was to assess whether off-line 3D volume manipulation can be used as a tool to substitute real-time 20 ultrasound for the subsequent studies. It demonstrated that measurements using 3D volume acquisitions exhibit good agreement with real-time 20 scanning, with no systematic error but with a higher random error. However, it also demonstrated that 3D scanning is slower to perform and, similar to real-time 2D, it is not always possible to acquire a 3D volume from a desired orientation. Furthermore, not all 3D volume acquisitions were amenable to reconstruction. However, this study showed that saved 3D volumes can be used as a mean to store large volumes of data for later detailed analysis. The aim of the fourth study was to create the FUB-Q scoring tool. This was done by establishing the difference in measurement resulting from optimal and different forms of suboptimal images in a systematic fashion. For any . t " given image, and its derived measurement, the observer inserts in the model the various image scoring point parameters. The model then gives a prediction about the confidence interval within which the optimal, "gold standard", measurement should be. The aim of the fifth study was to validate on an independent test set the predictive ability of the newly developed FUB-Q scoring tool. It demonstrated that the FUB-Q tool can correctly predict the confidence interval within which measurements recorded from correctly acquired images should be in relation to measurements acquired from incorrectly acquired ones. The aim of the sixth, and final , study was to evaluate the reproducibility of obtaining the relevant scores for the FUB-Q tool. It demonstrated that the FUB-Q tool has good intra- and inter- observer reproducibility and is a reliable system for assessing the quality of fetal biometry based on ultrasound images. In conclusion, the FUB-Q tool could be a useful system used for audit of clinical practice and quality control as well as for training purposes .
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available