Characterisation of tissue shrinkage during microwave thermal ablation. (17th October 2014)

• Record Type: Journal Article
• Authors: Farina, Laura; Weiss, Noam; Nissenbaum, Yitzhak; Cavagnaro, Marta; Lopresto, Vanni; Pinto, Rosanna; Tosoratti, Nevio; Amabile, Claudio; Cassarino, Simone; Goldberg, S. Nahum
• Is Part Of: International journal of hyperthermia. Volume 30:Number 7(2014)
• Page Start: 419
• Page End: 428
• Publication Date: 2014-10-17
• Subjects: Ex vivo studies -- microwave thermal ablation -- tissue shrinkage; Thermotherapy -- Periodicals; 615.832
• DOI: 10.3109/02656736.2014.957250
• Languages: English
• ISSNs: 0265-6736

Abstract

Abstract: Purpose : The aim of this study was to characterise changes in tissue volume during image-guided microwave ablation in order to arrive at a more precise determination of the true ablation zone. Materials and methods : The effect of power (20–80 W) and time (1–10 min) on microwave-induced tissue contraction was experimentally evaluated in various-sized cubes of ex vivo liver (10–40 mm ± 2 mm) and muscle (20 and 40 mm ± 2 mm) embedded in agar phantoms ( N = 119). Post-ablation linear and volumetric dimensions of the tissue cubes were measured and compared with pre-ablation dimensions. Subsequently, the process of tissue contraction was investigated dynamically during the ablation procedure through real-time X-ray CT scanning. Results : Overall, substantial shrinkage of 52–74% of initial tissue volume was noted. The shrinkage was non-uniform over time and space, with observed asymmetry favouring the radial (23–43 % range) over the longitudinal (21–29%) direction. Algorithmic relationships for the shrinkage as a function of time were demonstrated. Furthermore, the smallest cubes showed more substantial and faster contraction (28–40% after 1 min), with more considerable volumetric shrinkage (>10%) in muscle than in liver tissue. Additionally, CT imaging demonstrated initial expansion of the tissue volume, lasting in some cases up to 3 min during the microwave ablation procedure, prior to the contraction phenomenon. Conclusions : In addition to an asymmetric substantial shrinkage of the ablated tissue volume, an initial expansion phenomenon occurs during MW ablation. Thus, complex modifications of the tissue close to a radiating antenna will likely need to be taken into account for future methods of real-time ablation monitoring.