Accuracy of assessment of fetal anomalies using compressed fetal ultrasound video clips
Authors: Begg L. M. , Chan F. Y. , Edie G. , Hockey R. , Wootton R. 
Published: March 2003

Background:  Ultrasound is an accepted method of diagnosis and assessment of fetal anomalies, but the performance of ultrasound varies widely between tertiary and general units. Telemedicine involves the delivery of health care across a distance by combining telecommunications and medical expertise, and bridges the health care gap between the city and the regional centers, where access to subspecialist care is usually limited. Our group has shown that real‐time teleultrasound consultation is not only technically feasible, but also offers diagnostic and management modifications.

Current real‐time telemedicine relies on digital (ISDN) lines and hence is costly and still limited to larger centres. If the Internet could be used as a method of downloading ultrasound images taken in the field quickly and effectively, this would bring tertiary consultation to even extremely remote centers. Before ultrasound video clips could be transferred across the Internet efficiently, they need to be compressed into smaller files. Our group has previously determined that the maximum compression ratio that was considered clinically acceptable (without compromising image quality) was 1:50 to 1:100.

Aim:  To assess the ability of experienced ultrasonologists to make accurate diagnoses based on compressed ultrasound clips of fetal anomalies, as well as their confidence in making such diagnoses.

Methods:  Nine different clips of fetal anomalies and two different normal controls were compressed using commercially available software. The original uncompressed file sizes ranged from 55.6 to 622.7 MB. Final file sizes ranged from 1.6 to 10 MB (i.e. compression ratios of 1:10 to 1:130). Four experienced tertiary ultrasound specialists blinded to the compression factor evaluated the images. The examiners were asked to make a diagnosis from a selection of 48 possible choices. They were also asked to rate their confidence in making the diagnosis (based on the quality of transmission) and image clarity on a scale of 1–7. Data was analyzed using Duncan's multiple range test for variables, with alpha = 0.05.

Results:  A total of 71 versions of the 11 video clips were played at random to the observers. Intra‐ and interobserver variations were not significant. All of the observers were certain of their diagnoses (mean score above 4), although the certainty scores for cardiac anomalies and for normal fetuses were lower than the scores for other anomalies Of the 71 video clips, 66 were correctly diagnosed (93%). Two were partially correct (2.8%), and three were incorrect (4.2%). All the incorrect diagnoses were cardiac anomalies.

Conclusion:  Video clips of fetal ultrasound can be digitized, compressed and displayed on the computer without clinically or statistically significant loss of diagnostic certainty or image clarity. For compressions up to 1:100, the diagnostic accuracy was very high, although cardiac anomalies seem to pose the most difficulties. While the potential for consultation via the Internet is enormous, larger clinical trials need to be performed to confirm these results.