title: Multiparametric MRI analysis for the evaluation of MR-guided high intensity focused ultrasound tumor treatment.
abstract: For the clinical application of high intensity focused ultrasound (HIFU) for thermal ablation of malignant tumors, accurate treatment evaluation is of key importance. In this study, we have employed a multiparametric MRI protocol, consisting of quantitative T1, T2, ADC, amide proton transfer (APT), T1ρ and DCE-MRI measurements, to evaluate MR-guided HIFU treatment of subcutaneous tumors in rats. K-means clustering using all different combinations of the endogenous contrast MRI parameters (feature vectors) was performed to segment the multiparametric data into tissue populations with similar MR parameter values. The optimal feature vector for identification of the extent of non-viable tumor tissue after HIFU treatment was determined by quantitative comparison between clustering-derived and histology-derived non-viable tumor fractions. The highest one-to-one correspondence between these clustering-based and histology-based non-viable tumor fractions was observed for the feature vector {ADC, APT-weighted signal} (R(2) to line of identity (R(2)y=x) = 0.92) and the strongest agreement was seen 3 days after HIFU (R(2)y=x = 0.97). To compare the multiparametric MRI analysis results with conventional HIFU monitoring and evaluation methods, the histology-derived non-viable tumor fractions were also quantitatively compared with non-perfused tumor fractions (derived from the level of contrast enhancement in the DCE-MRI measurements) and 240 CEM tumor fractions (i.e. thermal dose > 240 cumulative equivalent minutes at 43 °C). The correlation between histology-derived non-viable tumor fractions directly after HIFU and the 240 CEM fractions was high, but not significant. The non-perfused fractions overestimated the extent of non-viable tumor tissue directly after HIFU, whereas an underestimation was observed 3 days after HIFU. In conclusion, we have shown that a multiparametric MR analysis, especially based on the ADC and the APT-weighted signal, can potentially be used to determine the extent of non-viable tumor tissue 3 days after HIFU treatment. We expect that this method can be incorporated in the current clinical workflow of MR-HIFU ablation therapies.
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.|Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Stefanie J C G
authors.initials: SJ
authors.lastname: Hectors
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
authors.forename: Igor
authors.initials: I
authors.lastname: Jacobs
authors.affiliation: Oncology Solutions, Philips Research Europe, Eindhoven, The Netherlands.
authors.forename: Edwin
authors.initials: E
authors.lastname: Heijman
authors.affiliation: Tomographic Imaging Systems, Philips Research Europe, Hamburg, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Keupp
authors.affiliation: Oncology Solutions, Philips Research Europe, Eindhoven, The Netherlands.
authors.forename: Monique
authors.initials: M
authors.lastname: Berben
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.|Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.|Oncology Solutions, Philips Research Europe, Eindhoven, The Netherlands.
authors.forename: Holger
authors.initials: H
authors.lastname: Grüll
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009369:Neoplasms / Q000473:pathology / Q000628:therapy*; D051381:Rats; D011916:Rats, Inbred F344
keywords: cancer; cluster analysis; high intensity focused ultrasound; multiparametric MRI; treatment response