Development of an MRI/x-ray/ultrasound compatible marker for pre-operative breast tumour localization

Abstract

This paper describes an in vitro investigation into the composition, structure and development of an magnetic resonance imaging (MRI), ultrasound (US) and x-ray imaging compatible marker for breast tumour localization. The marker is composed of 0.4-0.6 mm glass and iron-containing aluminium microspheres suspended in a gelatin matrix. The final form of the marker is a cylindrical shape 7 mm long with 2.05 mm diameter to facilitate delivery through a 12 gauge biopsy needle. To get optimal reflectivity for the US contrast, the glass microsphere concentration was found to be 40% by weight. US contrast is independent of marker orientation and the cylindrical shape made its US signal appearance distinctive thus ensuring confident identification. To control the MRI contrast, iron content was varied to generate a clear and local susceptibility signal void to reflect the marker position. Optimal iron content was found to be 52 microg iron which produced a clear signal void in spoiled gradient recalled MR images. The appearance of the susceptibility artefact is determined by the marker's shape, orientation and echo time. The final marker produces a dark artefact in MRI while appears as a clear hyperintense structure with acoustic shadowing in US images. The x-ray image showed the marker as a radio-opaque structure. This in vitro study demonstrates that the marker forms an alternative to traditional wire localization currently used for breast surgical procedures and creates new opportunities for US guided surgical procedures.

A positive contrast, tri-modality tissue marker for breast tumour localization

“…The copper microspheres had a diameter of 0.4 mm (Salem Specialty Co., USA) and the copper concentration was set at 5% by volume. This was based on our previous studies with glass microspheres (Li et al 2005b) which showed that this concentration of rigid scattering centres provided a clear ultrasound contrast (5-12 MHz) without ultrasound beam attenuation. This low concentration of copper meant that the majority of the marker volume is composed of Gd-DTPA-doped gel which provides the positive T1-weighted signal on MRI.…”

“…After determining the optimal marker mixture, a final marker composed of 60 copper microspheres was cast into a cylindrical gelatin structure (2 mm in diameter and 7 mm in length) using the fabrication method outlined in our previous work (Li et al 2005b). In brief, the microspheres were added in correct numbers to the gelatin and the mixture was cast in a 12 gauge needle.…”

Self-assembled gold coating enhances X-ray imaging of alginate microcapsules

“…More recently, macroscale contrast agents with distinctive shapes have been proposed to counter the issue of detection and positive identification at low contrast levels. 43,44 However the use of unnatural and distinctive shapes to aid the identification of labeled MCs has not been previously reported.…”

Potential for Contamination during Removal of Radioactive Seeds from Surgically Excised Tissue

“…Today, 125 I seeds are used most commonly in permanent implants for prostate cancer and are beginning to be used as permanent implants for breast cancer (Borchers et al 2004;Keller et al 2005). Over the past few years, several alternatives to the use of pre-operative wire localization for nonpalpable breast lesions have been investigated (Bergaz et al 2002;Li et al 2005). Some studies have focused on the use of 125 I seeds for more precise localization of lesions (Gray et al 2001(Gray et al , 2004Cox et al 2003;Hughes et al 2008).…”