Adverse effects of metallic artifacts on voxel-wise analysis and tract-based spatial statistics in diffusion tensor imaging.

Background Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that reflects the Brownian motion of water molecules constrained within brain tissue. Fractional anisotropy (FA) is one of the most commonly measured DTI parameters, and can be applied to quantitative analysis of white matter as tract-based spatial statistics (TBSS) and voxel-wise analysis. Purpose To show an association between metallic implants and the results of statistical analysis (voxel-wise group comparison and TBSS) for fractional anisotropy (FA) mapping, in DTI of healthy adults. Material and Methods Sixteen healthy volunteers were scanned with 3-Tesla MRI. A magnetic keeper type of dental implant was used as the metallic implant. DTI was acquired three times in each participant: (i) without a magnetic keeper (FAnon1); (ii) with a magnetic keeper (FAimp); and (iii) without a magnetic keeper (FAnon2) as reproducibility of FAnon1. Group comparisons with paired t-test were performed as FAnon1 vs. FAnon2, and as FAnon1 vs. FAimp. Results Regions of significantly reduced and increased local FA values were revealed by voxel-wise group comparison analysis (a P value of less than 0.05, corrected with family-wise error), but not by TBSS. Conclusion Metallic implants existing outside the field of view produce artifacts that affect the statistical analysis (voxel-wise group comparisons) for FA mapping. When statistical analysis for FA mapping is conducted by researchers, it is important to pay attention to any dental implants present in the mouths of the participants.

Significant improvement in superselective intra-arterial chemotherapy for oral cancer by using indocyanine green fluorescence.

BACKGROUND: Recent advances in indocyanine green (ICG) fluorescence imaging have enabled the visualization of the blood supply to tissues. For advanced head and neck cancer, intra-arterial chemotherapy has been applied for organ preservation and improvement of the prognosis. To identify the tumor-feeding artery, through which the intra-arterial chemotherapy should be administered, CT angiography has been shown to be useful. However, the precise evaluation for oral cancer patients depends on the oral environment, that is, whether they have been treated with dental metal. OBJECTIVES: To assess the feasibility of the ICG fluorescence technique during intra-arterial chemotherapy for advanced oral cancer. MATERIAL AND METHOD: Twenty-five patients with oral cancer who were treated by intra-arterial chemotherapy were included in this study. Conventional CT angiography followed by 5mg of ICG injection was performed to confirm the areas in which the drug had dispersed. Intra-arterial chemotherapy was administered at 75 mg/m(2) of CDDP. Additional information about the arteries feeding the tumors provided by ICG was evaluated. RESULTS: Out of 25 cases, in 15 (56%) the blood supply to the cancer was clearly detected by CT angiography. Using the infrared ICG evaluation, the blood supply to the tumor was confirmed easily in all cases. The information obtained from fluorescence imaging was helpful for making decisions concerning the administration of chemo-agents for oral cancers. CONCLUSION: ICG fluorescence imaging during intra-arterial chemotherapy compensated for the deficiencies of CT angiography, especially for oral cancer. ICG fluorescence provided us clearer and more useful information about the feeders to tumors.