Temperature–density hysteresis in X-ray CT during HIFU thermal ablation: Heating and cooling phantom study

Abstract

Our results demonstrate a HU-temperature hysteresis phenomenon for HIFU ablation, which is detectible by X-ray CT. This hysteresis is related to the amount of heat induced into the tissue and could potentially indicate irreversible tissue damage. Accordingly, this measurable phenomenon can be utilised as a quantitative method for non-invasive monitoring of thermal ablation.

Non-invasive temperature monitoring and hyperthermic injury onset detection using X-ray CT during HIFU thermal treatment in ex vivo fatty tissue

“…This can also be observed quantitatively in Table I. Both observations are consistent with the above hypothesis and previous findings [21].…”

“…These time progression images demonstrate how the heat dissipates around the centre of the HIFU focal spot zone while the temperature rises. However, contrary to findings in liver tissue [21], where the heat-up curve displayed a monotonic concave shape, in this case of fat tissue, a convex non-monotonic curve was observed, with a defined nadir point at about 44.5 C. Moreover, when combined with the post-ablation trajectory the plots described a counter-clockwise trajectory for fat tissue (marked in Figure 4F), which is fundamentally different from the clockwise trajectory observed in liver and chicken serum albumin experimentally studied [21]. These findings imply that the observed hysteresis phenomenon is tissue-type dependent.…”

“…Consequently, this has led to the assumption that the HU are linearly related to the temperature [27,28]. In a recent study [21], it was revealed that a very prominent non-linear behaviour of HU versus temperature exists and this is associated with a significant hysteresis phenomenon. This leads to the conclusion that the linear assumption is insufficient to adequately describe the physical process.…”

“…As prior studies of HU-temperature curves depict a hysteresis phenomenon whereby the heating trajectory differs substantially from the post-ablation stage trajectory [21], four hysteresis indices for quantifying this data were performed, as illustrated in Figure 2. …”

Planar strain analysis of liver undergoing microwave thermal ablation using x‐ray CT

“…Several works have investigated the potential of thermal monitoring by CT for ablation monitoring using RF, 32 laser, 33 and also HIFU. 34 It is important to note, that for treatment in human subjects, some differences from the presented results can be potentially anticipated. It is acknowledged that lower heat conduction mainly due to tissue cooling from blood flow is missing in exvivo experiments.…”