Value of Nonrigid Registration of Pre-Procedure MR with Post-Procedure CT After Radiofrequency Ablation for Hepatocellular Carcinoma
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).
Materials and 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.
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.
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.
KeywordsHepatocellular carcinoma Radiofrequency ablation Ablative margin Nonrigid registration Local tumor progression
This study was not funded by any grant.
Compliance with Ethical Standards
Conflict of interest
Author 1 is an employee of Siemens Healthcare. The prototype software (HepaCare version 3.0) utilized in this study was provided by Siemens Healthcare. However, control of all data and information submitted for publication was given to the authors who were not affiliated with Siemens Healthcare. For the remaining authors, they have nothing to disclose.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study before performing radiofrequency ablation. Since the subsequent follow-up liver MR or CT images were obtained during routine clinical practice, the requirement for written informed consent was waived. This retrospective, single-center study was approved by our institutional review board.
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