Distribution of Treatment Time
Original peer-reviewed paper:
Grey, K: “Distribution of Treatment Time in Physiotherapeutic Application of Ultrasound” in Physiotherapy, ( The Journal of the Chartered Society of Physiotherapy, UK), Volume 89, No 12, December 2003, pp 696-707.
This article is found online at www.ScienceDirect.com, (search by author).
Background and Purpose. In physiotherapy, the ultrasound transducer is moved across the treated area. Because of the movement, some points in the tissue are exposed to sound for less than the total treatment time. In the literature, some authors use the total treatment time, while others use a kind of average local exposure time to describe the temporal part of the exposure. It is unknown to what degree the total treatment time and the planned average local exposure time actually represent the local exposure. The reproducibility and sources of variation in spatial and temporal distribution of local exposure time across the tissue were investigated in this work.
Methods. Ideal scanning patterns were constructed mathematically, and manual application patterns from 22 therapists were sampled with a digitizer. One transducer model and various sizes of tissue models were used. From these application patterns the distributions of local exposure were calculated. The calculation model consisted of a circle, representing the cross section of the beam, moving across a plane surface, the tissue. By relating the beam position to tissue coordinates, the local exposure periods were found.
Results. Constructed applications showed an excellent match between planned and resulting average exposure. The therapists produced median local exposure times that were 0.3-0.9 times the planned average local exposure time. Considerable variation was found, where the calculated maxima were 0.4-3.8 times the planned average values.
Conclusions. Part of the variation is inherent in the nature of scanning application. Careful planning, concentration and guidelines drawn around the lesion increased the reproducibility of manual application. While the total treatment time alone was inadequate as a time parameter, the planned average local exposure time predicted the central tendency of the exposure, when the application was confined to the designated area. The investigation indicated that clinical testing of different application strategies with equal average exposure is necessary.
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Download: SONOMOVE simulator software
Fig 1A. The SonoMove simulator. The concentric "beam" (red) is moved over the skin (green). Fig 1A is the start position of the beam.
Fig 1B. The SonoMove simulator. Fig 1B is the third position of the beam. The local exposures are added up in each cell.
Would you like to experiment with the moving transducer technique and the distribution of energy?
Moving of the transducer is supposed to even out the "hot spots" of the ultrasound beam. But what really happens?
Download a small program containing a simulator, demonstrating just that (freeware by K. Grey) . Click the link below to download a compressed file containing two files.
Unpack the downloaded file SONOMOV3.RAR with winzip or winrar to a new directory, e.g. named "Sonomove". You need WinZip or WinRar on your computer. You may click the links on this page to download and install either one at first in order to unpack SonoMove.
The two files SONOMOV3.EXE and COMRUN87.OVR must reside in the same folder. The program cannot open from the Windows Start Menu. Go to "My Computer" and open the folder, where you saved the two files.
Click the main file
to run the simulation.
Read the on-screen help text, or press the key F1.
The simulator used in “Distribution of Treatment Time in Physiotherapeutic Application of Ultrasound” captured movements of the transducer and its speed by using a digitizer. Likewise, the simulator in SONOMOVE captures your movements, but regardless of speed.
In DOS-systems the computer-mouse may be used to move the simulator beam around, but in most Windows-based systems only the arrow-keys will work. Still, the SONOMOVE
simulator provides an opportunity to experience the energy being distributed across the exposed surface with every step, as you move the "applicator".
To further explore the feasibility of the distribution theory experiments were conducted with a moving light source, and furthermore with an irrigation system. This theory seems applicable to several distribution systems. Experiments with ultrasound are being planned.
The moving light distributions are illustrated in the Gallery pictures B1-B5. A light source was programmed to show and move on a computer monitor along a strict path and with even speed covering a predefined field of exposure. A camera was fixed in front of the monitor with the shutter opened during the entire exposure, and thus the light distribution was demonstrated in one picture.
This experiment was repeated with several light source profiles.
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