Monitoring of temperature increase and tissue vaporization during laser interstitial thermotherapy of ex-vivo swine liver by computed tomography

Laser interstitial thermotherapy (LITT) is aminimally invasive technique used to thermally destroy tumourcells. Being based on hyperthermia, LITT outcome depends onthe temperature distribution inside the tissue.Recently, CT scan thermometry, based on the dependence ofthe CT number (HU) on tissue temperature (T) has beenintroduced during LITT; it is an attractive approach tomonitor T because it overcomes the concerns related to theinvasiveness.We performed LITT on nine ex vivo swine livers at threedifferent laser powers, (P=1.5 W, P=3 W, P=5 W) with aconstant treatment time t=200 s; HU is averaged on twoellipsoidal regions of interest (ROI) of 0.2 cm2, placed at twodistances from the applicator (d=3.6 mm and d=8.7 mm); areference ROI was placed away from the applicator (d=30mm).The aim of this study is twofold: 1) to evaluate the effect ofthe T increase in terms of HU variation in ex vivo swine liversundergoing LITT; and 2) to estimate the P value for tissue vaporization. To the best of our knowledge, this is the firststudy focused on the HU variation in swine livers undergoingLITT at different P.The reported findings could be useful to assess the effect ofLITT on the liver in terms of both T changes and tissuevaporization, with the aim to obtain an effective therapy