Читать книгу Intracranial Gliomas Part III - Innovative Treatment Modalities - Группа авторов - Страница 35

A long-term problem in clinical application of the thermal therapies relates to our inability to achieve interactive control of the destructive energy deposition in the tissue; this requires the integration of real-time intraoperative information with posttreatment structural changes within the target and with the biological behavior of the lesion. Correspondingly, in the early days of LITT development, the most important limitations for its use were the absence of effective monitoring of the procedure and an inability to control the extent of the hyperthermic area, which was assessed only postoperatively with CT, MRI, and positron emission tomography (PET) [20]. Thereafter, post-contrast intraoperative MRI (iMRI) and different variations of the fast low angle shot (FLASH) MR sequence were applied for real-time assessment of the extent of thermal damage during the procedure [21, 22]. Jolesz and Zientara [9 ]have been at the forefront of establishing the principle of image-to-actual function (IAF)-based laser therapy and have defined the fundamental requirements for the real-time control of photo-irradiation energy: image contrast should primarily depend on temperature changes induced in tissue; contrast must be sufficient to allow visual detection; spatial resolution must be sufficient to show treated volume; and temporal resolution must be faster than thermal changes. De Poorter et al. [23] introduced the method of MR thermometry based on the dependence of proton resonance frequency on temperature, and demonstrated its 0.2°C accuracy. It has developed further into technology that currently supports real-time monitoring of the thermal changes in the targeted tissue during LITT [24]. At present a number of dynamic imaging protocols for intraoperative monitoring of the thermal therapies have been established based on various fast and ultrafast MR sequences, including echo-planar imaging (EPI), rapid acquisition with relaxation enhancement (RARE), BURST, gradient- and spin-echo (GRASE), etc. [9].