Delivering conventional ultrasound to underserved global regions has been unsuccessful due to inadequate infrastructure, untrained personnel, and insufficient funds. Volume scan imaging (VSI) may represent a vehicle which allows ultrasound to reach underserved populations. This study compares the efficacy of fetal VSI protocols relative to conventional ultrasound, serving as the predecessor for future studies to validate vascular and cardiac VSI protocols.
Sixty patients were scanned by nurse-midwives instructed in VSI protocols, with data interpreted by experienced radiologists. After VSI study completion, the patients were scanned by an experienced ultrasound practitioner, “back-scanner,” who was blinded to VSI results. The back-scanner, certified in performing and interpreting conventional ultrasound, used conventional ultrasound to assess seven clinical findings. Exams were interpreted as normal/abnormal, using a grading scale of 1 (normal) through 5 (abnormal). Interpretation of these exams served as the “gold standard” against which VSI interpretations were compared. VSI data were interpreted by seven radiologists with experience specific to VSI imaging; each radiologist assessed the same categories and generated an overall score of 1-5. The findings of each radiologist were compared against the gold standard data.
Relative to conventional ultrasound, VSI data correlated as follows: Identifying intrauterine pregnancy: 99.75%, Fetal position (breech and transverse): 85.71%, Placental position: 93.18%, Amniotic fluid: 86.92%, Free pelvic fluid: 93.32%, Masses: 94.33%. The overall radiologist scoring (1-5) matched the gold standard as follows: Sensitivity: 72.97%, Specificity: 89.27%, PPV: 72.32%, NPV: 89.58%, and Accuracy: 84.75%.
These data indicate that early VSI interpretations compare favorably with conventional ultrasound. As with other ultrasound procedures, overall findings were impacted by the interpreting radiologists’ experience and technique familiarity. Although the analysis compares favorably, it is presumed that modifications to the VSI protocols and increased familiarity with interpretation guidelines will result in even better concordance. The results warrant further studies to assess additional VSI protocols.
Gina Miele, VSI Educator and Spanish Translator, Medical Imaging Ministries of the Americas (MIMAs)