Topic ID: id_13107236
Version: 3.0
Date: Aug 29, 2019 1:30:48 AM

CAMERA CALIBRATION

Prerequisites

Table 1 Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	-	-	-

Table 2 Consumables
Item	Quantity	Effectivity	Part number	Manufacturer
	-	-	-	-

This procedure describes the steps necessary to verify and set the camera parameters. Once the display is re-calibrated, it is essential to re-calibrate the camera before the system is used for filming. Although a qualified GE Service Engineer could perform the steps below, it is recommended that the following procedure be performed with the on-site assistance of the camera vendor field engineer.

DASM Interpolation Setup (If DASM is present)

Procedure

Select the Install soft key from the Service Desktop. When prompted, login using the password operator.
Select the DASM folder from the top of the Guided Install GUI once it appears.
Set the DASM Interpolation method to linear.
Before exiting the GUI, insert the SaveInfo MOD or new MOD into the drive. Go to the top left corner of the Install GUI and select File and then Save GI Configuration to MOD. This process does not create a SaveInfo disk. It just creates a copy of the information already entered in the GUI tabs for use in the next software install.
Exit the install GUI by selecting File then Quit. If any error conditions still exist, you will be warned that no changes will be made before exiting.

Camera Imaging Look-Up Table

Procedure

Verify with the camera vendor field engineer that the currently installed camera lookup table is designed to provide perceivably linear contrast for the light box conditions in the customer’s viewing area.
If not, request that the camera vendor field engineer replace it with the appropriate look-up table.

Camera Maximum Optical Density

Procedure

Note that for optimal reviewing, the light box luminance of the diagnostic region of the film should be in the range of 50 to 500 nits.
Vary the maximum optical density setting of the camera to compensate for the light box and to meet this value. A good starting position is a maximum density of 2.8.

Camera Contrast

Procedure

With the maximum/minimum optical densities set to compensate for the review area’s light box, select a look-up table for your camera that will produce a perceivably linear gray scale for the same light box and the overall ambient light conditions of the viewing area.

note:
The DICOM 3.14 Standard specifies the Barten’s curve for linear perception. It is recommended that the manufacturer base perceptual linearity on this curve.
Film the SMPTE pattern on a 1-on-16 format display. Verify that the 5% and the 95% levels are visually equivalent. If not, perform a Contrast test with the SMPTE pattern. Select the new contrast setting from the contrast image set. A good value for the Imation DryView is 3. Use the camera’s calibration procedure to set the contrast setting. Ensure that the camera maintains a perceivably linear gray scale.

note:
Filming the SMPTE pattern for contrast calibration may be optional for the camera vendor.
Ask the technologist to display a clinical image and set window and level controls for the desired appearance. A good image to start with is a sagittal or axial head image.
Capture the image on the keypad or host control interface.
Print a Contrast Test film. Ask the technologist to select the image that best matches the displayed image on the monitor.
Observe the image number below the selected image and set the Contrast control to this value.

Anatomical Filming

This portion of the procedure requires the technologist to verify the camera settings with true anatomical images.

Procedure

Film representative anatomical images to confirm the settings. The image set should include T1 and T2 head images, joint images and c-spines.
Observe the accuracy of the low-tones, mid-tones and high-tones. If a filmed image is found to not be equivalent then re-calibrate the camera based on the customer’s evaluation.

Finalization

No finalization steps.