Fluke Biomedical 660-6 - Manual (Page 11)

Theory of Operation
Theory of Operation
2
2-1
Section 2
Theory of Operation
2.1 Theory of Operation
In a phantom, integration of the radiation exposure profile produced by a single scan from a CT scanner
along a line normal to the slice, divided by the table increment, is equal to the average exposure
produced by a series of scans to a central slice at that point. * The line of integration must be of sufficient
length to intercept both the primary beam and the Compton scanner produced in the phantom. The
integral is expressed as R cm.
A long, thin radiation probe can be used for the measurement. The probe should be calibrated in a
uniform field covering its entire sensitive length, with a correction factor determined in the conventional
manner. Subsequent probe readings, multiplied by the correction factor and then by its sensitive length,
will be in units of R cm.
The CT probes are designed especially for CT scanner applications. The correction factor due to their
length (10.0 cm) is built into the probe calibration:
• The Model 660-6, when used with the Model 660, is read directly in R cm or R cm/min.
• The Model 550-100 correction factor is stated in R cm/coulomb
In applications where the probes are used to
measure uniform field exposure in terms of R, the
Model 660 readings should be divided by 10 or the
Model 500-100 correction should be divided by 10.
*R. A. Jucius, G. X. Kambic, “Measurements of Computed Tomography X-Ray Fields Utilizing the Partial
Volume Effect”
NOTE