coDiagnostiX Knowledge Base

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====== Registration Reliability Display is red or yellow when pins seem to be set correctly ======

The registration reliability display is a security feature. It's mandatory to move the blue boxes exactly
over the white shape of the pins. Please always do this as exact as possible. Then the registration
reliability display shows you how good the quality of the underlying CT/CBCT dataset is in aspects of
the horizontal and vertical dimensions. If you set the boxes over the white pins and the registration
reliability is yellow or even red, the DICOM data isn't representing the dimensions of the patient's jaws correctly.
This means that something is wrong with the CT/CBCT dataset, which needs further investigation to find out why.
For example it sometimes happens that CBCT machines become inaccurate due to the fact that they have moving mechanical parts.
Then they need to be recalibrated. To prove it and to show how big the divergence is you have the possibility to measure
the distances between the pins. For this, please do the pin registration first (blue boxes exactly on white pins).

Then align the patient coordinate system according to the pin plane:

  - Double click ''Patient coordinate system''\\ {{:gonyx:reg_reliability_patient_coordinate_system.png?nolink|}}\\ \\
  - Then click the ''Align patient coordinate system to pins'' and hit ''OK''\\ {{:gonyx:reg_reliability_align_pcs_to_pins.png?nolink|}}\\ \\
  - Now you can measure the pin distance in the axial view.\\ {{:gonyx:reg_reliability_pin_measurements.png?nolink|}}

**The horizontal length from Pin 2 to Pin 3 must be a multiple of 5mm. The length of the perpendicular line segment
from the horizontal line to the center of Pin 1 must be 25mm.** There might always be smaller deviations (~0.1 up to 0.5mm).
This is normal and based on several interference factors and the Doctors usually know this. But if there is a bigger deviation
(above 1mm), the customer should start investigating, why the DICOM data is showing either a stretched or clinched image.

First recommendation is to contact the radiology where he got the DICOM CD and forward them the measurement screenshot.
They should then measure the pin distances in their CBCT software and contact the CBCT customer service with the request
to recalibrate the CBCT, if the deviation is reproducible.