Registration of Supine MR Mammography with Breast Ultrasound for Surgical Planning of Breast Conserving Surgery: AFeasibility Study.

Anne Hubbard,Ayesha Rahman,Caroline Bradley,Joanna Wieczorek,Lindsay Turnbull,Martin Pickles,Peter Gibbs,Ronjabati Roychaudhury

doi:10.1055/s-0041-108008

Abstract

Purpose To report the feasibility, accuracy and initial clinical experience of the use of real-time magnetic resonance navigated ultrasound (rtMRnUS) in the surgical planning of breast-conserving surgery (BCS) via guide wire insertion. Materials and Methods 29 participants were recruited into this prospective ethics committee approved study. The first 4 cases were utilized as a training set. Participants underwent asupine contrast-enhanced breast MR examination with external fiducials and corresponding ink marks placed on the skin of the affected breast to act as co-registration pairs. MR examinations included both functional and morphological images. A LOGIQ E9 ultrasound system (GE Healthcare, Milwaukee, WI, USA) equipped with a 6 - 15 MHz transducer was utilized for rtMRnUS. To facilitate point co-registration of the previously acquired MR dataset with the real-time ultrasound, co-registration pairs were identified on both imaging modalities. The following co-registration quality metrics were recorded: root mean square deviation (RMSD), lesion and global accuracies. Post co-registration guide wire insertion was performed. Results Co-registration was successfully undertaken in all participants. Results from 25 participants are presented. The median (min, max) RMSD was 3.3 mm (0.6 mm, 8.8 mm). The global accuracy was assessed as very good (8), good (12), moderate (3) and poor (2) while the median (min, max) lesion accuracy was recorded at 8.9 mm (2.1 mm, 33.2 mm). Conclusion The use of rtMRnUS to facilitate guide wire insertion is a feasible technique. Generally, very good or good global registration can be expected. Lesion accuracy results indicate that a median difference, in 3 D space, of 9 mm can be expected between imaging modalities.

Highlights

Localised breast tumours are typically managed by breast conserving surgery (BCS) combined with adjuvant radiotherapy, which provides comparable survival outcomes to traditional mastectomy [1,2], whilst providing a better cosmetic result
Positive margin status was noted from 4 participants following real-time MRI navigated ultrasound (rtMRnUS) facilitated guide wire insertion
If histopathology of the resected specimen reveals tumour extending to the surgical margin, so called positive margin, further resection is advised until a clear margin is obtained, since margin positivity is an important risk factor for recurrent disease [1]

Summary

Introduction

Localised breast tumours are typically managed by breast conserving surgery (BCS) combined with adjuvant radiotherapy, which provides comparable survival outcomes to traditional mastectomy [1,2], whilst providing a better cosmetic result. Re-operation for positive tumour margin status can result in poor cosmetic outcome, increased patient anxiety, delayed adjuvant therapy and increased treatment costs [1,2]. Ultrasound or stereotactic guided wire insertion is frequently used in the pre-surgical localisation of small breast cancers prior to BCS. Real-time MRI navigated ultrasound (rtMRnUS) has been introduced, that combines the benefits of both ultrasound and MRI. In this technique a previously acquired 3D MR dataset is co-registered to real-time US images. Both modalities are displayed simultaneously and the MR images can be used to navigate real-time US, allowing insertion of the guide wire into the optimum location

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Conclusion