Sir,
The article written by Dr. Singh et al.: Perivascular extension of microwave ablation zone: demonstrated using an in vitro porcine perfusion liver model (2018) VOL. 34, NO. 7, 1114–1120, has been met with great interest [Citation1]. With the advent of precise ablation, microwave ablation (MWA) has been widely used in the treatment of liver tumors. In this study, the researchers thoroughly discuss the concept of conformal thermal ablation.
The perfused liver model used in Dr. Singh’s study adequately imitates in vivo liver perfusions and suggests that large vessels can remove some of the energy during ablation. We have also used an in vivo model for liver ablation and demonstrated similar results. We found that local microcirculation can eliminate some of the heat that is carried away by flowing blood. Additionally, the effect of blood flow on the range of the ablation zone in MWA is significantly lower than that in radiofrequency ablation (RFA) because of the rapid rise of temperature in MWA (as compared to RFA). However, issues regarding the methodology of this study must be addressed. In Dr. Singh’s study, the liver was bisected after ablation; however, the time that the liver was bisected after ablation is not specified. If the MWA was performed immediately after the bisection, a large amount of outside energy would be necessary, and this would affect the results of the experiment. We believe that a delay in the time after ablation, and before incision, may allow blood vessels to transmit heat better. This is important because it challenges the authors’ conclusion suggesting that the extension of the ablation zone occurs independently of blood flow. We have used an in vivo model for ablation, which showed that after 24 h, the extent of ablation is significantly different from that under the immediate incision. In 2015, Ringe et al. reached similar conclusions in their study; within 24 h, a significant increase in the volume of the ablation zone was observed. They focused on increasing the volume of the ablation zone but not the blood perfusion [Citation2]. We look forward to submitting our results to your journal in the near future.
Disclosure statement
No potential conflict of interest was reported by the authors.
References
- Singh S, Siriwardana PN, Johnston EW, et al. Perivascular extension of microwave ablation zone: demonstrated using an ex vivo porcine perfusion liver model. Int J Hyperther. 2018;34:1114–1120.
- Ringe KI, Wacker F, Raatschen HJ. Is there a need for MRI within 24 hours after CT-guided percutaneous thermoablation of the liver? Acta Radiol. 2015;56:10–17.