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Page 1 of 2  Focused ultrasound is a very effective way to raise the temperature in a tumor in a completely non invasive way.
Principle
The principle is very simple: an ultrasounds emitter called a transducer is placed outside of the patient body. By its shape (usually a portion of a sphere) or by means of phased array operation, the transducer concentrates the ultrasound beams into a very small focal spot (the size of a rice grain). At the focal spot, the temperature rises rapidly while the temperature elsewhere remain the same. As an analogy, consider the sun rays focused with a lens: heating is only felt at the focal spot. To ablate a tumor, the focal spot is swept over the target volume. There are basically two strategies for sweeping the tumor with the focal spot:
- The sequential aproach (point by point or line by line) in which a small portion of the tumor (a point or a line) is completely destroyed before moving to the next point or line.
- The volumetric approach in which the focal spot is swept rapidly and repeatedly over the complete tumor volume until the target volume is completely destroyed .
The major advantages of focused ultrasound compared to other therapeutic techniques like radiation therapy are:
- damage to the tissue happens only at the focal spot. There is no effect of the ultrasound along the propagation path to the tumor.
- The technique is both non invasive and non ionizing (no irradiation).
- The physical mean of tissue destruction, heat, is deterministic. When tissues are heated above a threshold temperature, cellular death occurs within seconds with much certainty (this is not the case with radiation therapy).
 Focused ultrasounds ablation: heating at the focal spot through focusing of ultrasounds Focused ultrasound capacity to destroy a target precisely and non invasively, has been studied since the early 1950s [1-24]. What has essentially changed in the last few years to bring this technique into clinical practice is the rapid development of image guidance for the procedures. Real time image guidance during the procedure is indeed the key to safe, effective and reliable treatments.
Relevant links
References
- J. G. Lynn, R. L. Zwemer, A. J. Chick. "THE BIOLOGICAL APPLICATION OF FOCUSED ULTRASONIC WAVES" Science, 1942 Jul;96(2483):119-120
- E. J. Fry. "An ultrasonic projector design for a wide range of research applications" Rev Sci Instrum, 1950 Nov;21:940-1
- V. J. Wulff, W. J. Fry, D. Tucker, F. J. Fry and C. Melton. "Effect of ultrasonic vibrations on nerve tissues" Proc Soc Exp Biol Med, 1951 Feb;76:361-6
- P. D. Wall, W. J. Fry, R. Stephens, D. Tucker and J. Y. Lettvin. "Changes produced in the central nervous system by ultrasound" Science, 1951 Dec 28;114:686-7
- W. J. Fry. "Intense ultrasound; a new tool for neurological research" J Ment Sci, 1954 Jan;100:85-96
- W. J. Fry, W. H. Mosberg, Jr., J. W. Barnard and F. J. Fry. "Production of focal destructive lesions in the central nervous system with ultrasound" J Neurosurg, 1954 Sep;11:471-8
- W. J. Fry, J. W. Barnard, F. J. Fry and J. F. Brennan. "Ultrasonically produced localized selective lesions in the central nervous system" Am J Phys Med, 1955 Jun;34:413-23
- W. Fry. "Neurosonic surgery" Trans Am Neurol Assoc, 1955 86-8
- J. W. Barnard, W. J. Fry, F. J. Fry and R. F. Krumins. "Effects of high intensity ultrasound on the central nervous system of the cat" J Comp Neurol, 1955 Dec;103:459-84
- H. T. Ballantine, Jr., T. F. Hueter, W. J. Nauta and D. M. Sosa. "Focal destruction of nervous tissue by focused ultrasound: biophysical factors influencing its application" J Exp Med, 1956 Sep 1;104:337-60
- H. Thomas Ballantine, Jr. "The production of focal tissue destruction by focused ultrasound" Bull Soc Int Chir, 1956 Jul;15:355-61
- W. J. Fry. "Ultrasound in neurology" Neurology, 1956 Oct;6:693-704
- D. Bowsher. "Effect of high-intensity focused ultrasound on nerve cells in spinal cord of mouse" AMA Arch Neurol Psychiatry, 1957 Oct;78:377-82
- F. J. Fry, H. W. Ades and W. J. Fry. "Production of reversible changes in the central nervous system by ultrasound" Science, 1958 Jan 10;127:83-4
- F. J. Fry. "Precision high intensity focusing ultrasonic machines for surgery" Am J Phys Med, 1958 Jun;37:152-6
- W. J. Fry. "Use of intense ultrasound in neurological research" Am J Phys Med, 1958 Jun;37:143-7
- W. J. Fry. "Intense ultrasound in investigations of the central nervous system" Adv Biol Med Phys, 1958 6:281-348
- H. T. Ballantine, Jr., E. Bell and J. Manlapaz. "Progress and problems in the neurological applications of focused ultrasound" J Neurosurg, 1960 Sep;17:858-76
- K. E. Astrom, Belle, H. T. Ballantine, Jr. and E. Heidensleben. "An experimental neuropathological study of the effects of high-frequency focused ultrasound on the brain of the cat" J Neuropathol Exp Neurol, 1961 Oct;20:484-520
- R. C. Hickey, W. J. Fry, R. Meyers, F. J. Fry and J. T. Bradbury. "Human pituitary irradiation with focused ultrasound. An initial report on effect in advanced breast cancer" Arch Surg, 1961 Oct;83:620-33
- R. R. Young and E. Henneman. "Functional effects of focused ultrasound on mammalian nerves" Science, 1961 Nov 10;134:1521-2
- L. Basauri and P. P. Lele. "A simple method for production of trackless focal lesions with focused ultrasound: statistical evaluation of the effects of irradiation on the central nervous system of the cat" J Physiol, 1962 Mar;160:513-534 2
- A. F. Battista and R. Quint. "Effects of focused ultrasound on spontaneous cortical electrical potentials of the cat" Am J Physiol, 1962 Mar;202:475-9
- P. P. Lele. "A simple method for production of trackless focal lesions with focused ultrasound: physical factors" J Physiol, 1962 Mar;160:494-512
- N. Nakashima. "Experimental study on focal destructive lesions in the brain produced by the focused ultrasound" Nagoya J Med Sci, 1962 Aug;25:11-26
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