Zero Echo Time versus T1-Weighted Gradient-Recalled Echo MRI of Breast Biopsy Markers: A Phantom Study Comparing Susceptibility Artifact Volume and Geometric Dimensions

Background: Breast biopsy markers or clips play a critical role in marking biopsy sites, cross-correlating on multi-modality imaging, guiding surgical planning, and monitoring treatment response. However, susceptibility artifacts from metallic breast biopsy markers on conventional T1-weighted (T1w) MRI can obscure adjacent tissues, precluding accurate signaling and enhancement of any residual disease, particularly following neoadjuvant chemotherapy and during targeted axillary dissection procedures. Zero echo time (ZTE) MRI, by acquiring signal before substantial phase dispersion occurs, has the potential to reduce these artifacts. The objective of this study is to compare susceptibility artifact volume and geometric dimensions of breast biopsy markers quantitatively between ZTE and T1w gradient-recalled echo (GRE) MRI acquisitions in a controlled phantom setting.

Methods: Thirty-eight breast biopsy markers (37 commercially available, 1 research marker; 33 metallic, 5 non-metallic) were embedded in water-based gelatin phantoms and imaged at 1.5T using a T1w GRE sequence (Vibrant FLEX) and a ZTE sequence (oZTEo). For each sequence, susceptibility artifact volume and maximum length of the marker were quantified using adaptive thresholding with morphological refinement and compared with physical marker dimensions derived from mass and material density. Statistical analysis included Spearman correlation and Wilcoxon signed-rank tests considering p < 0.05 as denoting statistical significance.

Results: Compared with the physical marker volume, T1w GRE imaging produced a volumetric overestimation of 307 ± 286 mm³ (mean ± SD), whereas ZTE imaging showed a smaller overestimation of 72 ± 65 mm³ (p < 0.001). T1w GRE imaging marker volumes were ~4-5 times larger than those from ZTE, and their corresponding marker lengths were approximately ~1.4–1.5 times greater. Image marker volumes and maximum lengths were larger than their true measurements on both MRI acquisitions. Correlation with true physical volume was weak for both T1w (ρ = 0.21, p = 0.218) and ZTE (ρ = 0.32, p = 0.053). Length correlation with physical measurement was stronger for ZTE (ρ = 0.59, p < 0.001) than T1w (ρ = 0.28, p = 0.001)

Conclusions: In a controlled phantom setting, ZTE MRI demonstrated reduced susceptibility artifact volume and improved geometric agreement with true marker dimensions compared to T1w GRE. These findings warrant further investigation through prospective in vivo validation before clinical recommendations can be made.