KaVo 3D eXam, Operator'S Manual

Page: 113 / 170

k990400 September 19, 2007
Calibration and Quality Assurance
10-23
Radiation Output Test
It is recommended that a check of the kVp and Radiation Output of
the X-ray source be performed annually by a
qualified Physicist.
The incident Absorbed Dose at the detector may be measured using
a dosimeter. Tests are performed to assess output value and to check
for tube output consistency and timer accuracy.
1. Attach a dosimeter to the detector such that the sensor is
positioned where the vertical (coronal) and horizontal (axial)
lasers intersect. This is in the lower center of the detector.
2. Perform a 9 second, 13 cm, 0.4 voxel scan and record time and
dose from meter.
3. Repeat step 2 for 27 seconds and record.
Measured Dose
The table below shows measurements performed on the detector.
Tube Potential (kV) 120
Selected Scan Time (seconds) 27
Mechanical Rotation Time (seconds) 21.06
Approximate Exposure Time (seconds) 3.6
Displayed mAs 37.07
Measured Exposure at Detector (mR) 225
Measured Exposure at Detector / mAs (mR/mAs) 6.25
Measured Exposure at 1m (mR/mAs) 2.98
Measured Dose at 1m (
μ
Gy/mAs)
25.89
Dose at Detector per Frame (
μ
Gy/fr)
5.39
Tube Output (
μ
Gy/mAs @ 1m)
25.89
Distance Source to Detector (cm) 68
Conversion Factor for Absorbed Dose (R to Gy) 0.87