HIFU History: How, When and Where Did it Start?
The development of ultrasound transducers started with the work of P. Langevin who used the piezoelectric properties of quartz crystal to build the first submarine sonar.
In the 1950s, the Fry brothers - Francis and William - pioneered the first medical application of ultrasonic waves.
Their first works were related to the extra-corporeal treatment of neurological disorders. Using a set of ultrasound transducers, they were able to focus the energy deep inside the cerebral cortex. Unfortunately, this therapy was not completely developed due to the lack of necessary imaging technology devices.
In the 1980s, Lizzi, with a more advanced technology, set up a device for the treatment of glaucoma and intra-ocular tumors. This approach has been rapidly replaced by laser.
At the end of the 1980s, the INSERM - French National Institute for Medical Research - Lyon Hospitals and EDAP Technomed, engaged in a research program on the interaction of High Intensity Focused Ultrasound (HIFU) on tissues. The main purpose of this work was to develop applications to treat malignant tumors. As a result, the prototype of the Ablatherm® HIFU was born.
Ultrasound wave emission is based on transducer vibration. This results in dilatation and contraction modification of acoustical pressure.
The acoustical pressure creates tissue movement (dilatation and contraction) whose amplitude is directly related to the pressure level. As the tissue response is not perfectly elastic, energy is lost and converted into heat.
By using a spherical shaped transducer, the ultrasound beam is concentrated on the transducer focus point, resulting in a maximum of pressure concentrated at this point. As tissue heating is directly related to pressure maximum, the necrotic lesion is formed at the transducer focus.
Is Tissue Destroyed
How Does Ablatherm® HIFU Cause Destruction of Tissue?
Tissue temperature increases in the focal area resulting in a finite necrotic area.
This area extends about 3/4 in front of the transducer focus and 1/4 beyond.
The area dimension is related to the firing duration: the area starts at the transducer focus and progresses toward the transducer during the firing sequence.