Abstract
BackgroundMagnetic Resonance guided High Intensity Focused ultrasound (MR-HIFU) offers precise non-invasive thermotherapy for clinical applications such as the treatment of breast lesions. However, patients with a biopsy marker are usually not eligible for MR-HIFU treatment. This study investigates the interaction of some MR-compatible markers with MR-HIFU thermotherapy.MethodsThe MR-HIFU compatibility of 14 markers (6 Gold Anchor and 4 Visicoil markers in gold, 1 Visicoil marker in brass, 3 BiomarC markers in carbon coated) were tested using the Sonalleve breast MR-HIFU platform at 1.5 T. The impact of these markers was assessed by counting the number of voxels with low signal intensity on MR thermal maps and by comparing temperature increases induced by the HIFU beam.ResultsMost markers were visible on thermal maps with an apparent size 4.2 ± 3.1 and 2 ± 1.8 times larger than their respective actual width and length. The volume of masked voxels was for most of the markers much larger than the actual volume of the marker (up to a factor 65.1). However, it represents only a small fraction of the 12 mm diameter targeted region (up to 8.8 voxels which represents 19% of this targeted region). Some differences in the maximal temperature increase were observed especially for BiomarC 1 × 3 and BiomarC 2 × 4 markers enhancing the heating. These differences were less pronounced at the edge of the targeted region.ConclusionAll markers had a minimal impact on the volume above the thermal dose threshold of 240 EM since the differences measured were smaller than the in-plane image resolution of 1.56 mm.
Highlights
Magnetic Resonance guided High Intensity Focused ultrasound (MR-high-intensity focused ultrasound (HIFU)) offers precise non-invasive thermotherapy for clinical applications such as the treatment of breast lesions
This paper describes an evaluation of the compatibility of some MR-compatible markers with therapeutic ultrasound
Experimental setup The experimental setup is presented in Fig. 1a; Experiments were conducted with a prototype Sonalleve breast Magnetic Resonance guided High Intensity Focused ultrasound (MR-HIFU) platform (Profound, Mississauga, Canada) which is designed to emit ultrasound into the breast horizontally to avoid the risk to damage vital organs while treating breast lesions [13, 14]
Summary
Magnetic Resonance guided High Intensity Focused ultrasound (MR-HIFU) offers precise non-invasive thermotherapy for clinical applications such as the treatment of breast lesions. MR-HIFU uses high-intensity focused ultrasound (HIFU) guided by Magnetic Resonance (MR) to focus ultrasonic energy deep in the body without incisions or radiation. MR-HIFU treatment of small breast tumors or Ductal Carcinoma In Situ (DCIS) lesions has not been considered primarily because the presence of a metallic implant is considered an exclusion criterion for MR-HIFU9. These markers are systematically placed during breast biopsy following detection of a suspicious lesion during screening mammography
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