Room: Track 1
To demonstrate a novel method for quantitative evaluation of tomosynthesis-guided stereotactic breast biopsy (SBB) localization accuracy.
A biopsy phantom was constructed with a metallic pellet (1.5mm, X-SPOT-101) target on a flexible plastic shaft. The localization accuracy was assessed in the following steps:
1. Phantom was held by biopsy compression paddle on the detector.
2. Stereo pair images were acquired and center of the pellet was targeted.
3. Needle (Eviva, Hologic) was manually advanced to the pre-fire ([0,0,0]) position and pre-fire stereo pair and tomo images were obtained.
4. The needle was deployed and post-fire stereo pair and tomo images were obtained.
5. The DICOM images were exported and analyzed in a DICOM viewer (OsiriX).
The 3D coordinates of three key points were determined on pre- and post-fire tomo images including: pre-fire needle tip, post-fire needle tip and the target (center of the pellet). Using the analysis method illustrated in Fig.1g, the stroke length, target-to-trough center distance, and target-trough mis-alignment (off-center) error were calculated.
Three different biopsy strategies were investigated: (I) lateral biopsy on a prone table unit (Hologic, Affirm) as well as (II) cranio-caudal and (III) lateral biopsy using an upright system (Hologic, Selenia Dimensions). The measured stroke length, target to trough center distance and target-trough mis-alignment error for I, II and III geometries were (23.1, 2.5, 2)mm, (22.6, 2.8, 1.9)mm, and (23.2, 4.1, 3.8)mm respectively. The average measured stroke length was within 1.2 ± 0.01% of the nominal length (23mm) therefore, the observed variations in target location with respect to the trough center primarily stemmed from the target localization error.
Currently no standard quality control procedure exists for quantitative assessment of SBB localization accuracy. The proposed method shows potential to replace the current method which typically involves a breast biopsy phantom and binary, pass/fail results.