New Type of High-Intensity Focused Ultrasound Treatment for Prostate Cancer

HighIntensity Focused Ultrasound

High-Intensity Focused Ultrasound (HIFU) utilizes ultrasound energy to destroy tumours or diseased tissue without harming surrounding tissues, with many applications in oncology, urology, and gynaecology. This non-invasive procedure could potentially obviate the need for surgery, radiation and chemotherapy in some patients suffering from certain cancers. HIFU therapy has proven highly successful at treating prostate cancer, pelvic pain caused by an enlarged prostate gland and benign prostatic hyperplasia (BPH), as well as some gynecological disorders like fibroids, endometriosis myoma and uterine leimyoma. A clinical trial on HIFU therapy for prostate cancer has demonstrated its efficacy, with significant improvements seen among some men with prostate cancer and no need for more invasive approaches such as surgery, radiation or chemotherapy.

HIFU technology works on the principle that ultrasound waves can be focused onto small volumes within tissue to cause thermal coagulative necrosis, killing target cells while leaving surrounding tissue undamaged. This occurs via compression, refraction and harmonic oscillation of water molecules carried into tissue by soundwaves; creating an abrupt temperature gradient between targeted region and collateral tissue.

At therapeutic intensities (ISATA > 5 W/cm2), high intensity focused ultrasound produces both thermal and mechanical effects, including cavitation-driven effects that increase radiation force as well as mechanical ones caused by acoustic cavitation and radiation force amplification, leading to reduced therapy effectiveness and lengthened procedure times.

To maximise HIFU effectiveness and prevent unwanted side effects, it is critical that an accurate target volume for ablation be selected. This requires ensuring the acoustic window through which sound waves enter the body is large enough for safe treatment, the target boundaries are clearly delineated, and no sensitive normal tissue structures lie within its area of action. Determining an ideal ultrasound exposure requires detailed mechanistic studies in tissue-mimicking materials or complex numerical models.

HIFU treatments involve healthcare providers placing a spherical ultrasound transducer above or on top of the target tissue and using imaging to find its exact location. Once identified, electronic beam steering will direct US energy directly onto it. Furthermore, devices may be used to keep target areas still, such as head frames for treating tremor or devices to hold prostate during prostate cancer treatments; depending on each situation patients can be fully conscious or lightly sedated or under general anesthesia as appropriate.

Most tissues in the human body, with the exception of fat, air and bone, possess similar physical properties to water. Therefore, ultrasound waves easily pass through these tissues while reflections at their interfaces remain negligible and coupling between adjacent cells is strong.

Focusing ultrasound energy onto target tissue can be accomplished in various ways: single element spherical shell of piezoelectric material such as quartz can create a focused bowl; flat transducers with interchangeable lenses provide steering but cannot focus; and phased arrays enable both steering and focusing simultaneously.