I want talk about HIFU monitoring with MR and ultrasound. Compared with MR, ultrasound has better temporal resolution and lower cost. However, currently MR thermometry is the only clinically-feasible temperature imaging method. Ultrasound temperature imaging techniques are under heavy investigation, but still far from being clinically applicable. This is mainly due to the low temperature estimation accuracy and limited applicable temperature range (most of them are applicable in 37-45 degrees Celsius). Another aspect of ultrasound-based HIFU monitoring is related to thermal lesions (or ablation zones) when tissue coagulation necrosis forms. This aspect is under extensive exploration too.

Dear Zhuhuang Zhou,

I substantially disagree about the real "status of art" of US temperature imaging with US guided HIFU. By using, eventually, different methods, we can cover, in my opinion, the whole temperature interval of interest (43-90 °C). And if temperature may not directly measurable, some directly related quantity can be used, for example elastic properties of tissues or microbubbles production. But is not just the temperature evaluation hampering the US guided HIFU development. The realization of "sealed" sources can be even more important,. for a really clinically usable device. The source, not the patient, should be moved for the treatment of the different locations! What's your opinion?

All my best,

Gianni

I may add an information potentially useful: in a recent publication (Int J Hyperthermia. 2014 Feb;30(1):27-35. doi: 10.3109/02656736.2013.860241. Epub 2013 Dec 10. ), N. Weiss et al. demonstrated (on a phantom and on ex vivo animal liver) a remarkable dependence of the CT Hounsfield Unit (HU) from the the temperature and an HU hysteresis phenomenon, potentially related with the irreversible tissue change. This effect may be potentially useful to monitor the temperature (eventually in addition of US based methods) for combining "Cone Beams" LINACS with USgFUS in a new device (FUS/RT).