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Alternative Tumor-Targeting Strategies
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Ultrasound is already a useful imaging tool in medicine, useful for the diagnosis of various diseases and for monitoring the progress of pregnancy. Due to its acceptable safety, non-invasive nature, low cost, and ease of administration, ultrasonography is the second most-used diagnostic imaging technique after traditional X-ray radiography. However, in addition to its diagnostic applications, ultrasound is of growing interest for cancer treatment using an experimental approach known as Ultrasound Hyperthermia which involves the use of ultrasound energy to directly heat cells in a tumor to kill them. Electromagnetic waves and lasers have previously been tried for this purpose, but ultrasound has the intrinsic advantage of focusing to any depth inside the body. Current ultrasound-based thermo-ablation procedures use HIFU devices to induce rapid cell death in small regions of tissues for treating benign medical conditions (e.g., uterine fibroids and benign prostatic hyperplasia) and for the experimental treatment of some cancer types (e.g., prostate, breast, and pancreatic).
Magnetic Resonance-Guided Focused Ultrasound (MRgFUS)
Published in John C. Petrozza, Uterine Fibroids, 2020
Prior to consideration of MRgFUS, a contrast-enhanced MRI should be obtained to document size and location of fibroids. There are several unique anatomic considerations that must be considered prior to proceeding with MRgFUS, owing to the use of ultrasound energy during ablation; appropriate patient selection is an important factor affecting procedure outcomes [2,3]. Due to the rapid decrease in ultrasound energy as it passes through tissue, fibroid depth from the skin surface is an important consideration impacting ablation outcome. This cannot be greater than 12 cm [1,4]. Mindjuk et al. evaluated factors associated with clinical success in a single-center experience with 252 women [1], finding that a more complete ablation could be achieved in fibroids with low-enhancement pre-procedure, as well as fibroids distant from the spine (>3 cm). Less complete ablation was seen in fibroids with a subserosal component and those further away from the skin (skin-distant fibroids) (p < 0.001), with the postprocedure nonperfused fraction of the fibroid decreasing by 1.5% per centimeter of distance. A single-center evaluation of the anatomic appropriateness of MRgFUS for all fibroid patients presenting for care found that only 80 of 169 (47%) patients were eligible for treatment with this technique [5], with the main reasons being obesity and inaccessibility of fibroids. Other considerations include overlying bowel loops, as ultrasound energy cannot travel through air, as well as location of fibroids close to the spine, which limit the ability to sonicate owing to risk of injury to the sacral nerve [1].
Basic and Technical Aspects of Ultrasound
Published in Arianna D'Angelo, Nazar N. Amso, Ultrasound in Assisted Reproduction and Early Pregnancy, 2020
There is a third interaction of ultrasound with tissue that does not contribute to the signals returning to the ultrasound transducer but is nevertheless important—that is, absorption. Absorption is basically the conversion of ultrasound (mechanical) energy into another form of energy due to the interaction of the pressure wave with tissue. The most common conversion of ultrasound energy is into internal molecular energy or heat. In diagnostic ultrasound, heating is undesirable, as it can lead to detrimental bioeffects, particularly in sensitive tissues. This is covered at a later point. In addition, absorption leads to energy loss from the ultrasound beam, which reduces the penetration of the beam. As absorption increases with frequency, this effectively also contributes to the upper limit of ultrasound frequency possible. In general terms, diagnostic ultrasound rarely exceeds 20–24 MHz.
Oxford’s clinical experience in the development of high intensity focused ultrasound therapy
Published in International Journal of Hyperthermia, 2021
Ishika Prachee, Feng Wu, David Cranston
A novel application has been investigated to explore the feasibility of ultrasound-mediated anti-tumour drug delivery. This work is beyond ablation, which uses a lower ultrasound energy for treatment. A pioneering trial of Oxford clinical therapeutic ultrasound research has been the exploration of ultrasound as a tool for drug delivery. This uses both thermal mechanisms for mild-hyperthermia triggered drug delivery from thermosensitive liposomes, and cavitational mechanisms for enhanced delivery and distribution of unmodified small-molecule and antibody therapeutics. The first-in-human trial of ultrasonically triggered drug delivery in oncology, TARDOX, was completed in 2018 and published in Lancet Oncology [29]. Two further studies, one to treat pancreatic tumours with thermosensitive liposomal doxorubicin and one to treat metastatic colorectal tumours in the liver by cavitation-enhanced antibody delivery, are currently starting.
Comparison of outcomes of hysteroscopic myomectomy of type 2 submucous fibroids greater than 4 cm in diameter via pretreatment with HIFU or GnRH-a
Published in International Journal of Hyperthermia, 2021
Ping Liao, Jing Jiang, Yu-hua Zeng, Yan Chen, Min Yong, Da-cheng Qu, Hong-gui Zhou
The protocol of HIFU treatment was described in a previously study [15]. Briefly, HIFU treatment was performed under conscious sedation. The JC HIFU tumor therapeutic system (Chongqing Haifu Medical Technology, Co., Ltd., Chongqing, China) was used for HIFU treatment. Therapeutic ultrasound energy was generated by a transducer with a frequency of 1.0 MHz. A Mylab 70 ultrasound imaging device (Esaote, Genova, Italy) was used to provide real-time imaging to monitor the treatment. The patients were placed in a prone position on the HIFU table, with the anterior abdominal wall in contact with degassed water. A degassed water balloon was placed between the abdominal wall and the transducer to help compress or push the bowel away from the acoustic pathway. Focal point was selected, and power set between 300–400 watts. During the procedure, the power was adjusted based on patient feedback and gray scale changes. This process was repeated until there was an absence of blood supply under contrast-enhanced ultrasound. The patients' vital signs such as heart rate, blood pressure, respiration, oxygen saturation were monitored during the procedure. The following formula: V = (1/6) × π ×D1 × D2 × D3 was used to calculated the volume of the fibroids, the non-perfused volume, and the volume of the uterus [16].
Long-term follow-up outcome and reintervention analysis of ultrasound-guided high intensity focused ultrasound treatment for uterine fibroids
Published in International Journal of Hyperthermia, 2020
Waixing Li, Zhaoying Jiang, Xinliang Deng, Dabao Xu
USgHIFU ablation was performed under intravenous conscious sedation. The device used was a JC200 HIFU tumor therapeutic system (Chongqing Haifu Medical Technology, Co., Ltd., Chongqing, China). Therapeutic ultrasound energy was generated by a transducer with a frequency of 0.8 MHz, a focal length of 15 cm and a diameter of 20 cm. A Mylab 70 ultrasound imaging device (Esaote, Genova, Italy) was used to provide real-time imaging to localize and monitor the treatment. The patients were placed in a prone position on the HIFU table, with the anterior abdominal wall in contact with degassed water. A degassed water balloon was placed between the abdominal wall and the transducer to help compress and push the bowel away from the acoustic pathway. Point scan was selected, and power set between 300 and 400 W. The distance from focal point to endometrium was at least 1.5 cm, and the distance from focal point to subserosal surface of the uterus was 1 cm. During the procedure, therapeutic energy was adjusted based on patient feedback and changes in grayscale on ultrasonographic imaging. This process was repeated until there was an absence of blood supply under contrast-enhanced ultrasound. The patients' vital signs such as heart rate, blood pressure, respiration and oxygen saturation were monitored during the procedure.