title: Amide proton transfer imaging of high intensity focused ultrasound-treated tumor tissue.
abstract: OBJECTIVE
  In this study, the suitability of amide proton transfer (APT) imaging as a biomarker for the characterization of high intensity focused ultrasound (HIFU)-treated tumor tissue was assessed.
  
  
  METHODS
  APT imaging was performed on tumor-bearing mice before (n = 15), directly after (n = 15) and at 3 days (n = 8) after HIFU treatment. A control group (n = 7) of nontreated animals was scanned at the same time points. Histogram analysis of the tumor APT-weighted signal distributions was performed to assess HIFU-induced changes in the tumor APT contrast.
  
  
  RESULTS
  Distinct regions of decreased APT-weighted signal were observed at both time points after HIFU treatment. Analysis of the tumor APT-weighted signal distribution showed a pronounced shift toward lower APT-weighted signal values after HIFU treatment. A significantly increased fraction of pixels with an APT-weighted signal value between -10 and -2% was observed both directly (0.37 ± 0.16) and at 3 days (0.49 ± 0.16) after HIFU treatment as compared to baseline (0.22 ± 0.16).
  
  
  CONCLUSIONS
  The presented results show that APT imaging is sensitive to HIFU-induced changes in tumor tissue and may thus serve as a new biomarker for monitoring the response of tumor tissue to HIFU treatment.
authors.affiliation: Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands; Center for Imaging Research and Education (CIRE), Eindhoven, The Netherlands.
authors.forename: Stefanie J C G
authors.initials: SJ
authors.lastname: Hectors
authors.forename: Igor
authors.initials: I
authors.lastname: Jacobs
authors.forename: Gustav J
authors.initials: GJ
authors.lastname: Strijkers
authors.forename: Klaas
authors.initials: K
authors.lastname: Nicolay
mesh_terms: D000577:Amides / Q000737:chemistry; D000818:Animals; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000473:pathology* / Q000601:surgery*; D019220:High-Energy Shock Waves / Q000627:therapeutic use; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008807:Mice, Inbred BALB C; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D000577:Amides; D011522:Protons
keywords: amide proton transfer imaging; cancer treatment response; high intensity focused ultrasound