Search

Therapy with high intensity focused ultrasound (HIFU) has been shown to be both safe and clinically practical in a growing number of patient studies for a variety of different target organs. Especially in cancer therapy there are comparable ablation methods like radio frequency (RFA) or laser (LITT) ablation, which are clinically more accepted. In an ongoing study we compare HIFU with RF‐ and laser ablation under MRI guidance in a perfused organ model. All evaluated techniques were appropriate to induce defined and localized ablation necrosis in the renal cortex. Our HIFU system and the laser system were completely MRI compatible. The tested RF‐ system showed local needle artefacts and disturbed the MR images during operation. The ablation rate of HIFU using a spot scanning technique was clearly lower compared to the other ablation techniques. However, advanced HIFU scanning methods might overcome this limitation. In addition HIFU is the only complete non‐invasive ablation technique.

High intensity focused ultrasound (HIFU) under magnetic resonance imaging (MRI) guidance is an attractive instrument to ablate tissue non‐invasively. The aim of this work was to investigate the coagulation volume and the perfusion changes after HIFU‐ablation in an isolated kidney model using MRI. Ablation was performed at least at two regions of the renal cortex. Morphological T1‐/T2‐weighted, temperature sensitive images and contrast‐enhanced perfusion measurements were performed. The detection of single HIFU induced coagulation necroses and HIFU induced tissue cavities was feasible. Perfusion changes could only be detected in few experiments because of relatively inhomogeneous kidney perfusion patterns. MR‐imaging is a sensitive method to detect and to quantify the HIFU‐focus. Moreover, MRI is a valuable approach for the detection of HIFU induced coagulation necroses. The investigation of perfusion changes, particularly important in tumor treatment, was sometimes hampered due to limitations in the used organ model. However, in patients MR perfusion imaging as well as volumetric and morphological imaging can be used to control the outcome of HIFU‐therapy.