The relationship between applied energy and ablation zone volume in patients with hepatocellular carcinoma and colorectal liver metastasis

Abstract

ObjectivesTo study the ratio of ablation zone volume to applied energy in computed tomography (CT)-guided radiofrequency ablation (RFA) and microwave ablation (MWA) in patients with hepatocellular carcinoma (HCC) in a cirrhotic liver and in patients with colorectal liver metastasis (CRLM).MethodsIn total, 90 liver tumors, 45 HCCs in a cirrhotic liver and 45 CRLMs were treated with RFA or with one of two MWA devices (MWA_A and MWA_B), resulting in 15 procedures for each tumor type, per device. Device settings were recorded and the applied energy was calculated. Ablation volumes were segmented on the contrast-enhanced CT scans obtained 1 week after the procedure. The ratio of ablation zone volume in milliliters to applied energy in kilojoules was determined for each procedure and compared between HCC (RHCC) and CRLM (RCRLM), stratified according to ablation device.ResultsWith RFA, RHCC and RCRLM were 0.22 mL/kJ (0.14–0.45 mL/kJ) and 0.15 mL/kJ (0.14–0.22 mL/kJ; p = 0.110), respectively. With MWA_A, RHCC was 0.81 (0.61–1.07 mL/kJ) and RCRLM was 0.43 (0.35–0.61 mL/kJ; p = 0.001). With MWA_B, RHCC was 0.67 (0.41–0.85 mL/kJ) and RCRLM was 0.43 (0.35–0.61 mL/kJ; p = 0.040).ConclusionsWith RFA, there was no significant difference in energy deposition ratio between tumor types. With both MWA devices, the ratios were higher for HCCs. Tailoring microwave ablation device protocols to tumor type might prevent incomplete ablations.Key Points • HCCs and CRLMs respond differently to microwave ablation • For MWA, CRLMs required more energy to achieve a similar ablation volume • Tailoring ablation protocols to tumor type might prevent incomplete ablations

Stereotactic Image-Guidance for Ablation of Malignant Liver Tumors

“…The amount of energy needed can also be planned with the planning software. However, recent studies have shown that the resulting ablation zones differ from the prediction based on the ex-vivo results that are provided by the ablation device manufacturers [26] and also depend on the tumor type [27].…”

Moderate Heat Application Enhances the Efficacy of Nanosecond Pulse Stimulation for the Treatment of Squamous Cell Carcinoma

“…Current microwave and radiofrequency ablative therapies are most efficient for thermal ablation, where the goal is to raise the target tumor temperature to a lethal temperature, thereby inducing necrosis or apoptosis. 36 Instead, our platform provides fast, focused MH (43°C) to the target tissue only; a benefit of utilizing a laser heating source versus microwaves 37 – 39 or radiofrequency, 6 – 8 , 36 whose temperatures can exceed 100°C and 150°C, respectively, and can in some cases stimulate heat-induced tumor spreading. 40 By combining low-voltage NPS with a moderate amount of heat, we can mitigate theses deleterious effects providing high-power fast heating with an infrared laser.…”

Stereotactic image guided microwave ablation of HCC: A step forward and still a long way to go

“…Thus, how can the manufacturers’ provided ablation algorithms ever predict the ablation zone in humans with diseased liver parenchyma, with various types of tumours and highly variable arterial and portal blood flow and in close contact with adjacent structures? The impact of tumour type was analysed in a clinical MWA study; we found that the ratio “ablation zone volume:applied energy” was higher in HCC tumours as compared to colorectal liver metastases . This suggests that also the tumour type is of relevance for the completeness of ablation: colorectal liver metastases require more energy than HCCs.…”