Clinicians led by Dr Thomas Marini, a radiologist at the University of Rochester in upstate New York, have recently published a freely available article in the Journal of Ultrasound in Medicine that assesses volume sweep imaging (VSI) of the breast. Since the majority of women in the world lack access to basic imaging – resulting in a delay to diagnose breast cancer – Marini et al. tested a VSI ultrasound protocol for evaluation of palpable breast lumps. They hypothesized that unskilled operators with minimal training could produce images that were good enough for comparison with the standard of care.
Medical students who had no previous ultrasound experience were trained for less than two hours using a Butterfly Network iQ hand-held scanner that costs approximately $2,000 (seen above right). The VSI protocol is “an imaging technique in which the operator sweeps the ultrasound probe over the target region in relation to external body landmarks requiring no significant anatomic or medical knowledge. Sweeps are recorded as videos which are then saved for later interpretation by a specialist.” Note that the operator does not interpret the images.
The images at left (© American Institute of Ultrasound in Medicine) illustrate the initial steps in the VSI protocol. First, the patient identifies where the lump is located in her breast and the operator draws an X over the area of concern. Then the operator scans over the X from superior to inferior with the ultrasound probe in a transverse orientation, while recording a cine clip. Further clips are recorded with scans in the inferior-superior, medio-lateral, and diagonal directions. The exam is short in duration and can be completed in under 5 minutes.
As seen below right (© AIUM), the standard of care images, acquired with an ultrasound system costing up to $100,000, are of better quality than volume sweep images although the latter are of diagnostic quality. A total of 170 palpable lumps were scanned by the medical students using the VSI protocol, then diagnosed by experts, with sensitivity of 97% and specificity of 100% for a breast mass which corresponded to 97.6% agreement with standard of care.
Three-quarters of the lesions were benign, with good agreement for mass characteristics between VSI and standard of care, including 87% agreement on Breast Imaging-Reporting and Data Systems (BI-RADS) assessments. The authors concluded that breast ultrasound VSI for palpable lumps offers promise for women in underserved areas of the world, potentially improving morbidity and mortality. Marini and his team have also suggested that artificial intelligence (AI) could also play an important role when combined with VSI.