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Transcript
S25-21
Artifacts induced by bone conduction implant with MRI-scan. A method to reduce their impact on
radiologic assessment
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Collin M. , Lavieille J.-P. , Chaumoitre K. , Craighero F. , Rolland G. , Berbis J. , Deveze A.
1,2
1
University Hospital Nord, Department of Otolaryngology, Marseille, France, 2Aix Marseille University, Laboratory of Biomechanics and
Applications IFSTTAR UMR T24, Marseille, France, 3University Hospital Nord, Department of Radiology, Marseille, France, 4University
Hospital Nord, Department of Public Health, Marseille, France, 5Aix Marseille University, EA 3279 Research Unit, Marseille, France
Background: The Bone Bridge implant is being said to be MRI-scan safe and its applicability to the treatment of
single sided deafness and conductive or mixed hearing losses has been demonstrated. However, the limitation
due to the MRI-induced artifacts is still unknown and may impact the follow-up of otologic or cerebral diseases.
Objectives: To evaluate artifacts induced by the Bone Bridge implant exposed to a 1.5 Tesla magnetic
resonance field. We aimed to analyze first the impact of these artifacts on the visualization of the temporal bone
and intra-cranial structures, and second to test whether different positioning of the implant may reduce the
location and size of the artifacts.
Methods: Ten healthy volunteers underwent a cranial MRI-scan. MRI-scan was done without implant and
repeated with the Bone Bridge implant just applied onto the skin in the mastoid area, maintained by a standard
bandage Artifacts' areas were measured relative to surface of the whole slices for two different slices: one
reference axial section crossing the column of the fornix and one reference axial section crossing vestibular
labyrinths. 3 different positioning of the implant relative to the orbitomeatal plane were tested: 0°, 45° and 90°.
MRI-scan acquisitions were repeated identically. We performed a quantitative and qualitative analysis of artifacts'
areas using the Osirix software. The relative percentage of artifact area was calculated for each patient and each
implant position. The mean percentage artifact area for each MRI sequence and each implant position was
calculated and compared intra- and inter-individually. Using a qualitative assessment grid, two radiologists
evaluated the visibility and deformation of specific intra-cranial structures for each subject with regards to implant
positioning. Wilcoxon signed-rank test (non-parametric statistical hypothesis test) was used to compare artifact
area in regard of sequence, slice thickness or implant position.
Results: Whatever the type of MRI-scan acquisition, implant positioning at 90° impacted significantly less both
the surface of artifacts (p = 0.002) and the visualization and deformation of structures. Artifact area is greater for
2.5 mm slices comparing to 5 mm slices (p = 0,002 for T2 weighted sequences, p = 0,006 for T1-weighted
sequences). T2-weighted sequences create fewer artifacts than T1-weighted sequences with a 90° implant
positioning (p = 0.002). Radiologist evaluation found better scores for 90° implant positioning (p = 0.03).
Conclusion: tifacts are reduced by the positioning the Bone Bridge implant perpendicular to the orbitomeatal
line, by using thicker slices and T2-weighted sequences. This experimental study provides trails for further
clinical studies with patient requiring bone vibrator implants. This study helps to adapt the position of implant
according to a specific cerebral or temporal bone pathology needing radiologic follow-up.
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