31 mei 2006: Bron: BJU International Volume 97 Page 779 - April 2006 doi:10.1111/j.1464-410X.2006.06037.x Volume 97 Issue 4

HIFU = High Focused Ultra Sound succesvol toegepast bij niertumoren. Deze studie bevestigt eerdere studieresultaten dat HIFU een belangrijk alternatief kan zijn voor andere meer traditionele operatie technieken bij niertumoren.

Extracorporeally induced ablation of renal tissue by high-intensity focused ultrasound AXEL HÄCKER, MAURICE S. MICHEL, ERNST MARLINGHAUS*, KAI U. KÖHRMANN† and PETER ALKEN

Authors from Germany describe the use of percutaneously applied high-intensity focused ultrasound for non-invasive tissue ablation. They found that the lessons they learned from the use of this technology in animals could be transferred to its use in humans, both of which are described. They indicate that refinements in the technology are essential before this treatment can be used outside the departmental stage.

The use of endoluminal ultrasonography is discussed by authors from the Netherlands, for preventing significant bleeding during endopyelotomy. In a prospective study, they evaluate this technology against helical CT.

OBJECTIVE

To investigate the safety and the effects on healthy renal tissue of high-intensity focused ultrasound (HIFU) applied extracorporeally.

PATIENTS, MATERIALS AND METHODS

Ultrasound waves (1.04 MHz) created by a cylindrical piezo-ceramic element were focused by a parabolic reflector to a physical focus size of 32 × 4 mm (−6 dB). For an in vivo study, HIFU was applied to the healthy tissue of 24 kidneys, monitored by ultrasonography, with a maximum power of 400 W and a spatially averaged intensity (ISAL) in the focus of 1192 W/cm2. Fourteen kidneys were removed immediately after ablation to evaluate the side-effects and the effects in the focal zone, and 10 kidneys were removed delayed after 1, 7 and 10 days. The clinical study consisted of 19 patients requiring radical nephrectomy for a renal tumour. HIFU was applied to the healthy tissue of 19 kidneys (up to 1600 W, ISAL = 4768 W/cm2) before proceeding with the radical nephrectomy.

RESULTS

There were no major complications after applying HIFU to the 43 kidneys. Side-effects included skin burns (grade 3) in two patients. During the follow-up there were no further HIFU-specific side-effects. In one case (in vivo study) there was a thermal lesion of the small intestine, which was due to mis-focusing. HIFU effects in the focal zone immediately after application were: interstitial haemorrhages, fibre rupture, shrinking of the collagen fibres, and coagulation necrosis. These effects occurred sporadically, and their number and size did not correspond to the number of HIFU pulses applied. After 7 and 10 days, there was a well-demarcated coagulation necrosis in vivo.

CONCLUSION

Using this device, extracorporeally applied HIFU can ablate healthy kidney tissue in vivo in combination with diagnostic online ultrasonography. The technique is safe and resulted only in minor complications (skin burns). Refinements in the technology are essential to establish HIFU as a noninvasive treatment option that allows complete and reliable tissue ablation.

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