title: Value of Nonrigid Registration of Pre-Procedure MR with Post-Procedure CT After Radiofrequency Ablation for Hepatocellular Carcinoma.
abstract: OBJECTIVE
  To evaluate the value of pre-radiofrequency ablation (RFA) MR and post-RFA CT registration for the assessment of the therapeutic response of hepatocellular carcinoma (HCC).
  
  
  METHODS
  A total of 178 patients with single HCC who received RFA as an initial treatment and had available pre-RFA MR and post-RFA CT images were included in this retrospective study. Two independent readers (one experienced radiologist, one inexperienced radiologist) scored the ablative margin (AM) of treated tumors on a four-point scale (1, residual tumor; 2, incomplete AM; 3, borderline AM; 4, sufficient AM), in two separate sessions: (1) visual comparison between pre-and post-RFA images; (2) with addition of nonrigid registration for pre- and post-RFA images. Local tumor progression (LTP) rates between low-risk (response score, 3-4) and high-risk groups (1-2) were analyzed using the Kaplan-Meier method at each interpretation session.
  
  
  RESULTS
  The patients' reassignments after using the registered images were statistically significant for inexperienced reader (p < 0.001). In the inexperienced reader, LTP rates of low- and high-risk groups were significantly different with addition of registered images (session 2) (p < 0.001), but not significantly different in session 1 (p = 0.101). However, in the experienced reader, LTP rates of low- and high-risk groups were significantly different in both interpretation sessions (p < 0.001). Using the registered images, the cumulative incidence of LTP at 2 years was 3.0-6.6%, for the low-risk group, and 18.6-27.8% for the high-risk group.
  
  
  CONCLUSIONS
  Registration between pre-RFA MR and post-RFA CT images may allow better assessment of the therapeutic response of HCC after RFA, especially for inexperienced radiologists, helping in the risk stratification for LTP.
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Juil
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul, South Korea. jmlshy2000@gmail.com.|Department of Radiology, Institute of Radiation Medicine, Seoul National University College of Medicine, 101 Daehangno, Jongno-gu, Seoul, 03080, South Korea. jmlshy2000@gmail.com.
authors.forename: Jeong Min
authors.initials: JM
authors.lastname: Lee
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Lee
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Ijin
authors.initials: I
authors.lastname: Joo
authors.affiliation: Department of Radiology, Seoul National University Hospital, Seoul, South Korea.
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Department of Radiology, Dongnam Institute of Radiological and Medical Sciences, Busan, South Korea.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Park
authors.affiliation: Siemens Healthineers, Computed Tomography, 91301, Forchheim, Germany.
authors.forename: Ernst
authors.initials: E
authors.lastname: Klotz
mesh_terms: D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000601:surgery*; D017115:Catheter Ablation / Q000379:methods*; D002983:Clinical Competence; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000601:surgery; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D000072662:Margins of Excision; D008875:Middle Aged; D015588:Observer Variation; D010166:Palliative Care; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
keywords: Ablative margin; Hepatocellular carcinoma; Local tumor progression; Nonrigid registration; Radiofrequency ablation