BACKGROUND Compared to surgery, radiofrequency ablation(RFA) for colorectal liver metastasis(CRLM) is associated with higher local recurrence(LR) rates. A wide margin (at least 5 mm) is generally recommended to prevent LR, but the optimal method to assess ablation margins is yet to be established. The aim of our study was to evaluate the feasibility and reproducibility of CT-CT co-registration, using MIRADA software, in order to assess ablation margins of patients with CRLM. METHODS In this retrospective study, pre- and post-ablation contrast-enhanced CT scans of 29 patients, treated with percutaneous RFA for a solitary CRLM, were co-registered. Co-registration was performed by two independent radiologist, based on venous structures in proximity to the tumor. Feasibility of CT-CT co-registration and inter-observer agreement for reproducibility and ablation margins was determined. Furthermore, the minimal ablation margin was compared with the occurrence of LR during follow-up. RESULTS Co-registration was considered feasible in 18 patients (61% male, 63.1(±10.9) year), with a perfect inter-observer agreement for completeness of ablation: κ = 1.0(p < 0.001). And substantial inter-observer agreement for measurement of the minimal margin (≤ 0 mm, 1-5 mm, ≥ 5 mm): κ = 0.723(p-value < 0.001). LR occurred in eight of nine(88.9%) incompletely ablated CRLM and in one of the nine completely ablated CRLM(11.1%). CONCLUSION Co-registration using MIRADA is reproducible and potentially a valuable tool in defining technical success. Feasibility of co-registration of pre- and post-ablation CT scans is suboptimal if scans are not acquired concordantly. Co-registration may potentially aid in the prediction of LR after percutaneous ablation.

中文翻译：

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在CT扫描上使用MIRADA RTx对孤立性结直肠肝转移进行射频消融的定量余量评估：一项可行性研究。

背景技术与手术相比，射频消融（RFA）治疗结直肠肝转移（CRLM）与更高的局部复发（LR）率相关。通常建议使用宽裕度（至少5 mm）以防止LR，但是尚无最佳的评估消融裕度的方法。我们的研究目的是使用MIRADA软件评估CT-CT共配准的可行性和可重复性，以评估CRLM患者的消融余量。方法在这项回顾性研究中，对经消融术前和消融后对比增强的CT扫描（共29例）进行了配准，这些CT扫描均经皮RFA进行了单独CRLM治疗。由两名独立的放射科医生根据靠近肿瘤的静脉结构进行共配准。确定了CT-CT共同注册和观察员之间关于可重复性和消融余量的协议的可行性。此外，将最小消融余量与随访期间LR的发生率进行了比较。结果18位患者（61％的男性，63.1（±10.9）年）被认为是可行的，并且观察者之间达成了一个完美的消融完整性协议：κ= 1.0（p <0.001）。观察者之间达成的关于最小裕度（≤0 mm，1-5 mm，≥5 mm）的基本协议：κ= 0.723（p值<0.001）。LR发生在九个完全消融的CRLM中的八个（88.9％）和九个完全消融的CRLM中的一个（11.1％）。结论使用MIRADA进行共注册是可重复的，并且可能是定义技术成功的有价值的工具。如果没有一致地获得扫描，则消融前后CT扫描共配准的可行性不是最佳的。共注册可能潜在地有助于经皮消融后LR的预测。