Analysis of Color Doppler Twinkling on Breast Biopsy Markers With Hydrostatic Overpressurization and Micro-CT Imaging

Previous development of a breast biopsy marker that can be readily detected using color Doppler twinkling has been reported, but the cause of twinkling remains unclear. The objective is to better understand the mechanism for twinkling by exploring the effects of microbubbles on the surfaces of markers that twinkle compared to those that do not.

Twinkling metallic clinical markers and twinkling polymethyl methacrylate (PMMA) markers were evaluated in a pressure chamber. The hydrostatic pressure around the markers was increased from 0 to 1000 psi. To evaluate the effects of internal and external structures on twinkling, micro-CT scans were conducted to analyze the internal voids and surface roughness of the markers. A low-twinkling PMMA sample and a non-twinkling metal rod were also tested.

Twinkling markers exhibited decreased twinkling as the hydrostatic pressure increased. PMMA markers mixed for approximately 75% of the time required to reach the hardening phase of the polymerization reaction exhibited the highest twinkling signals under increased pressure. Internal voids were found to have no correlation with twinkling. Samples with higher surface roughness values (S_a and full width at half maximum in the y-dimension) were found to correlate with twinkling (p = 0.037 and p = 0.011, respectively).

These results support oscillating microbubbles on surfaces as a cause of twinkling. Prior work connecting surface roughness to twinkling is, hence, corroborated by the microbubbles present on rougher surfaces.