This is a single occasion on which a patient is positioned and exposed to ionizing radiation. This is usually related to the pressing of a button on the machine which is the source of radiation. Total exposures are divided into two categories:
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a) |
Treatment exposures, which may be: i. Treatment exposure ii. Check film iii. Simultaneous treatment exposure and check film |
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b) |
Other exposures: i. Exposure for calibration and quality control (patient is not present) ii. Exposure for research etc. |
Notes:
1. If a machine switches itself off during the exposure and it can be restarted immediately from the control panel, this constitutes one exposure.
2. If a machine switches itself off during an exposure and, before being restarted, the radiographer has to enter the room to readjust the equipment this is counted as two exposures.
3. If a patient becomes distressed during an exposure, necessitating turning off the machine and the radiographer has to enter the room before restarting this is counted as two exposures.
4. Total body irradiation may involve a very long exposure. For the purposes of assessing availability of radiotherapy machines, total body irradiation should be counted as 20 exposures for each hour the procedure took.
Fraction: A set of exposures delivered to one patient in the course of one visit to a radiotherapy room. A patient can have one or more fractions in a day, in that, although all day has been spent in the department, there has been more than one separate visit to the radiotherapy room.
Number of diseases treated by radiotherapy: determined by counting the number of initial first treatment exposures, comprising:
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a) |
First exposure for all primary courses (see COURSE OF TREATMENT |
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b) |
First exposure for all subsequent courses where previous course was administered in another district. |