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Magnetic Resonance Imaging
Published in Shoogo Ueno, Bioimaging, 2020
MRI is different from computed tomography (CT) and PET in that there is no radiation exposure, so repeated imaging is possible. It is expected to be a means of navigation in surgery and various other treatments. When this happens, the therapeutic instruments used need to be nonmagnetic, but various nonmagnetic tools are already being developed. In addition, in recent years, surgery has been complemented by methods in which the body is treated without cutting by irradiating affected areas with ultrasonic waves, electromagnetic waves, or radiation. High-intensity focused ultrasound (HIFU) is a therapeutic method in which ultrasonic waves of high amplitude are focused on a single spot, and then the disease sites are eliminated by pyrogenicity. By using MRI, it is possible to monitor temperature distribution in real time in addition to anatomical information from affected areas. Consequently, it is possible to use MRI throughout all treatment, including preparation of an HIFU treatment plan through detailed visualization of lesions, monitoring heat generation in the therapeutic process, and evaluating postoperative status. In recent years, there have also reportedly been examples of developing HIFU devices under MRI guides [23,24].
Current Role of Focal Therapy for Prostate Cancer
Published in Ayman El-Baz, Gyan Pareek, Jasjit S. Suri, Prostate Cancer Imaging, 2018
H. Abraham Chiang, George E. Haleblian
As is the case for all focal therapy modalities, interpretation of the above findings is limited by several issues. The type of pre- and post-treatment prostate biopsies were not standardized and included standard TRUS, targeted, and template biopsies. Furthermore, at least one study did not mandate post-treatment biopsies (i.e., post-treatment biopsy was performed for clinical suspicion of biochemical recurrence only). With regard to the functional outcomes, the definition of ED and urinary incontinence varied widely from study to study. Despite these limitations, the published literature suggests that HIFU is a relatively safe procedure with favorable functional outcomes when compared to standard of care radical therapies. Oncologic outcomes with respect to prostate cancer–specific survival appear no worse than standard of care, which is not surprising given that studies primarily focused on low- to intermediate-risk patients. However, the implications of residual clinically significant prostate cancer remain uncertain in the absence of longer follow-up and secondary outcome data regarding disease progression and development of metastatic disease. Randomized controlled trials comparing HIFU to standard of care therapies are lacking and needed to better evaluate the role of HIFU in the treatment of prostate cancer.
Medical Applications
Published in Suresh C. Ameta, Rakshit Ameta, Garima Ameta, Sonochemistry, 2018
Kennedy et al. (2003) reviewed the recent developments made in the field of HIFU applications. They have discussed the potential of HIFU as a noninvasive surgical technique in the treatment of tumours of various internal organs such as liver, kidney, breast, bone, uterus and pancreas and different other ailments. They suggested that high intensity focussed ultrasound (HIFU) is likely to play a major role as surgery of future.
Deep brain stimulation and other surgical modalities for the management of essential tremor
Published in Expert Review of Medical Devices, 2020
Kai-Liang Wang, Qianwei Ren, Shannon Chiu, Bhavana Patel, Fan-Gang Meng, Wei Hu, Aparna Wagle Shukla
Recently, transcranial MRI-guided FUS treatment became clinically available. The procedure does not require a burr hole drilling. Thus, it is viewed as a noninvasive or a minimally invasive procedure. FUS also does not require implanted foreign hardware. FUS shows benefits through Vim lesioning and has emerged as an alternate choice for medication refractory ET [98,99]. In 1927, the work of Robert Wood and Alfred Loomis demonstrated the effects of sonic waves in living tissues [100]. Lynn et al. reported the first recording of FUS for the brain tissue in 1942 [101], which was later applied in animal brains for the ablation of tissues [102,103]. Although their experiments were promising, an important limitation of FUS was the need for a craniotomy to achieve an adequate acoustic window since an intact skull does not allow transmission of ultrasound. With the advent of MRI and co-registration with CT, it was possible to correct for skull inhomogeneities to defocus the acoustic energy. With real-time monitoring of the intensity and location of thermal lesion, in 2012, Elias et al. published the first clinical trial results of FUS therapy for ET patients [104] and in 2016, the FDA granted an approval. In FUS, high-intensity focused ultrasound (HIFU) is combined with MRI to deploy acoustic energy at a specific target. HIFU has multi biological tissue effects related to thermal energy and mechanical effect [105]. The tissue effects depend on acoustic intensity, rate and the exposure time and since absorption of acoustic wave occurs in a short time, thermal energy is produced by the friction of molecular vibration [105,106]. The irreversible coagulative necrosis of lesions reflected in MRI is seen at temperatures over 56°C [105,107].
Fast computation of desired thermal dose: Application to focused ultrasound-induced lesion planning
Published in Numerical Heat Transfer, Part A: Applications, 2020
Jinao Zhang, Nha-Dat Bui, Wa Cheung, Stuart K. Roberts, Sunita Chauhan
The heat source in HIFU is due to tissue attenuation of ultrasound waves where the mechanical vibration energy of ultrasound waves is absorbed by tissue in the form of heat. Since the simulated ultrasound field is non-linear in which higher harmonic frequencies occur, is also a non-linear heat source to be fed into PBHT and is determined from the harmonic components of the acoustic pressure field, i.e., where is the tissue mass density the tissue sound speed the frequency-dependent attenuation coefficient of the th harmonic with a frequency power law of the form [45] ( in our case) and the angular frequency the acoustic pressure of the th harmonic component and the number of total harmonics ( in our case due to (i) higher harmonic contents were very small in our simulation and could be neglected and (ii) run-time and memory requirements became a challenge for calculating higher harmonics).