KaVo ORTHOPANTOMOGRAPH OP 3D Pro Installation Manual page 96

6 Panoramic and 3D calibrations and adjustments
88
"ROIs" are smaller
reconstructed volume that are used to calculate noise or
average grey values, for example. ROIs are marked with
thin circular lines inside the reconstructed volume.
Last lines of text on the image tell the file name of the
measurement results stored in a csv table. Path for this file
is typically C:\ProgramData\DXR120\. It is not necessary,
but the "3DROI" file can be copied to be archived as
constancy check results or imported to a spreadsheet
program to closer examine measured values. In case of
failed QC result, this file can be attached for technical
support request.
Description for the measurements
Noise measurement
Noise is defined as standard deviation of the 3D
measurement ROI in the volume. Noise is determined from
several materials in the phantom:
• PMMA std. dev.
• PTFE std. dev.
• Air std. dev.
Grey values measurement
Grey values of several materials in the reconstructed
volume are measured. There must be difference in grey
values in different materials to ensure adequate low
contrast resolution and consequently to make sure that
good tissue/bone separation is achieved in the 3D volume.
Following grey values are measured from the volume:
• PMMA average value
- Corresponds closely water x-ray absorption
• PTFE average value
• Air average value
Field Uniformity
Field uniformity measurement calculates max difference in
grey values between centre and border regions of the
PMMA material in the phantom.
volumes inside the 3D QC