Using US Twinkling Artifact to Identify Breast Biopsy Markers: Brief Report

Long-Term Ultrasound Twinkling Detectability and Safety of a Polymethyl Methacrylate Soft Tissue Marker Compared to Conventional Breast Biopsy Markers-A Preclinical Study in a Porcine Model

OBJECTIVE

We have studied the use of polymethyl methacrylate (PMMA) as an alternative biopsy marker that is readily detectable with ultrasound Doppler twinkling in cases of in vitro, ex vivo, or limited duration in vivo settings. This study investigates the long-term safety and ultrasound Doppler twinkling detectability of a PMMA breast biopsy marker following local perturbations and different dwell times in a 6-mo animal experiment.

METHODS

This study, which was approved by our Institutional Animal Care and Use Committee, involved three pigs and utilized various markers, including PMMA (Zimmer Biomet), 3D-printed, and Tumark Q markers. Markers were implanted at different times for each pig. Mesh material or ethanol was used to induce a local inflammatory reaction near certain markers. A semiquantitative twinkling score assessed twinkling for actionable localization during monthly ultrasounds. At the primary endpoint, ultrasound-guided localization of lymph nodes with detectable markers was performed. Following surgical resection of the localized nodes, histomorphometric analysis was conducted to evaluate for tissue ingrowth and the formation of a tissue rind around the markers.

RESULTS

No adverse events occurred. Twinkling scores of all markers for all three pigs decreased gradually over time. The Q marker exhibited the highest mean twinkling score followed by the PMMA marker, PMMA with mesh, and Q with ethanol. The 3D-printed marker with mesh and PMMA with ethanol had the lowest scores. All wire-localized lymph nodes were successfully resected. Despite varying percentages of tissue rind around the markers and a significant reduction in overall twinkling (p < 0.001) over time, mean PMMA twinkling scores remained clinically actionable at 6 and 5 mo using a General Electric C1-6 probe and 9L-probe, respectively.

CONCLUSIONS

In this porcine model, the PMMA marker demonstrates an acceptable safety profile. Clinically actionable twinkling aids PMMA marker detection even after 6 mo of dwell time in porcine lymph nodes. The Q marker maintained the greatest twinkling over time compared to all the other markers studied.

A Novel Color Doppler Ultrasound Artifact for Identifying Breast and Axilla Tumor Markers: Blooming-like Artifact

RATIONALE AND OBJECTIVES: Detection of tumor marker location in the breast and axilla using a less commonly utilized color Doppler ultrasound (CDUS) artifact.

MATERIALS AND METHODS

This prospective study was conducted between August and December 2023 and included consecutive patients with markers placed in the breast and axilla, both before and after neoadjuvant chemotherapy (NACT). Examinations were conducted using a 14 to 5 MHz linear array transducer with B-mode and Doppler capability. By reducing the velocity scale and increasing the color gain values, adjustments were made to create a bloom-like artifact. CDUS was performed with the ultrasound transmit frequency set between 14-5 MHz, color frequency between 6 and 7, color gain ranging from 58 to 80, and velocity scale within the range of 4.6-6.1 cm/s.

RESULTS

Twenty patients, with a mean age of 55.50 years ± 12.04 SD (range, 31-72), were included in the study. 14 (70%) were pre-NACT, and six (30%) were post-NACT patients. A total of 20 breast lesions and six axillary lymph nodes were marked. The breast lesions and axillary lymph nodes where the biopsy marker was placed (14 breast lesions and five axillary lymph nodes before NACT, six breast lesions and one axillary lymph node after NACT) were localized with blooming-like artifact. The average size of breast lesions was 20.95 mm ± 6.56 SD (range, 15-40). For axillary lymph nodes, the average size was 20.63 mm ± 5.01 SD (range: 31-14).

CONCLUSION

The blooming-like CDUS artifact is a novel and easily applicable method determining the location of metallic markers in the breast and axilla on diagnostic examinations.

Using 3-D-Printed Structures to Evaluate the Potential Causes of the Color Doppler Twinkling Signature

OBJECTIVE

The color Doppler twinkling artifact has been attributed to existing microbubbles or cavitation occurring on rough objects such as kidney stones, some breast biopsy clips, catheter guidewires and sandpaper. The objective was to investigate the correlation between the surface characteristics of helical constructs with different groove geometries and the occurrence of twinkling, as well as to identify locations conducive to bubble retention and/or cavitation.

METHODS

Six half-cylinders were created with a microscale 3-D printer with 5 µm resolution to replicate the geometry of twinkling helical constructs resembling catheter guidewires. Four copies of each marker including a non-twinkling control were printed. The half-cylinders had pitch (peak-to-peak distance) values ranging from 87.5 to 343 µm and amplitude (groove depth) values ranging from 41.5 to 209 µm. The half-cylinders were submerged in degassed water and optically imaged before and after ultrasound insonification to visualize bubbles on the cylinders. The cylinders remained submerged while scanning with the color Doppler mode at frequencies from 3.1 to 6.3 MHz using a GE Logiq E9 scanner and 9L linear array transducer.

RESULTS

Two markers exhibited twinkling: one with pitch-to-amplitude ratio of 174/210 µm/µm (0.8) that twinkled only with pre-existing bubbles on the marker; the other had a ratio of 87/87 µm/µm (1.00) that twinkled without pre-existing bubbles on the marker.

CONCLUSION

This work provides strong evidence that both existing bubbles and either cavitation or ultrasound wave interactions with patterned or rough surfaces are significant factors in producing the twinkling signature.