2-7
fourth configuration was with the table in the 20º Trendelenberg position. The lead
curtain was also removed in this case.
Measurements of air kerma were made using a 500 ml ionization chamber con-
nected to a Capintec electrometer. The chamber was mounted vertically on a tri-
pod, centered at heights of 1.0 and 1.5 meters above the floor. The measurements
were made throughout the exam room within 3 meters of the reference point on a
grid using 50 cm spacing between measurements. Measurements were made as
close as practical to the x–ray unit. In areas close to the x–ray unit where the stray
radiation field changed rapidly, the spacing between measurements was reduced
to 25 cm to further improve the accuracy of the isokerma maps.
4-3Results
Measured values of air kerma were normalized to 1 GyVcm as specified in the
IEC standard and used to construct isokerma contours at values of 16, 8, 4, 2, 1,
0.5, 0.25, 0.12, 0.06, 0.03, and 0.02 mGy/GyVcm. An isokerma dose map is pro-
vided for each of the four configurations, in horizontal planes 1.0 and 1.5 meters
above the floor.
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