Calibrate Image

MPR (CT and MR) Image Calibration

When an image has been loaded into an Image window buffer, the button for that buffer will display a small, dark gray badge to the upper right of the button icon.

To calibrate a CT (or MR) multiplanar reconstruction (MPR) image you must first activate one of the MPR group images (axial, equator, sagittal, t-coronal or t-meridian) then enable and position the MPR ruler in the Image window.
Click the Ruler button in the MPR image controls group (its just above the button labeled Angle) to display Plaque Simulator's MPR calibration ruler. Although PS optionally supports up to 4 rulers per image, only the primary ruler (#1) may be used to calibrate an image.
Ruler options are enabled and accessed from the Properties... item of the ruler button's contextual menu. Optional rulers #2 through 4 share the image calibration established by ruler #1.
Ruler properties that you can customize include:
- A label for the ruler
- Color
- Line width
- Font size
- End marks
- Line style
- Label angle
- Label position
- Showing the outer circle
- Showing the ruler
In the Image window, drag Plaque Simulator's MPR primary ruler (#1) over the calibration indicator of the image or any object in the image of known dimensions, typically about 40 or 50 mm.
Adjust the diameter of Plaque Simulator's MPR ruler by dragging the control boxes until the outer circle diameter fits the known object. The control boxes change from the ruler color property to yellow when the boxes are horizontally or vertically aligned. In the example on the right, the diameter of Plaque Simulator's MPR ruler represents 50 mm according to the green colored calibration indicator in the image.
With the MPR ruler still enabled, click the Calibrate button in the CT Image controls group to open the calibration dialog sheet.
Enter the diameter in mm (e.g. 50 mm). Buttons for 30, 40 and 50 mm diameter presets are also provided as a convenience.
You can propagate this calibration to other images by selecting any or all of the other MPR images that you know will use the same calibration.
Click the OK button to exit the sheet.

Fundus Image Calibration

To calibrate a fundus image you must first activate the fundus image and then enable and position the fundus ruler in the Image window.
Drag the fundus ruler yellow control boxes to mark the center of the optic disc and the posterior pole. The control end for the pole is so labeled.
With the ruler still enabled, click the Calib. button in the Fundus controls group to open the calibration dialog sheet.
Enter the Distance in mm (e.g. 3.99) between the center of the disc and the pole. If you have previously adjusted the Eye modeling tool on the axial image, you can import this distance as a convenience.
The Disc radius perimeter indicator of the ruler tool defaults to a 1 mm radius. You can customize this if you wish.
The Transparent color defaults to black. All black pixels in the fundus image will become transparent when the image is applied to the surface of the retina in both 2D and 3D models. By default both 2D and 3D transparency is enabled. Although black is the recommended color to use as the surrounding fill for fundus images, you can change the transparency color to suit your actual image.
While dragging the fundus ruler tool and/or any of its control boxes, holding down the control key on the keyboard enables live updating of the fundus image in other windows. Holding down the option key maintains the current calibration distance once the image has been calibrated. For example, hold down both keys to maintain the current calibration with live updates.
Click the OK button to exit the sheet.

Eye Picture Calibration

The eye picture and its ruler do not require any calibration. The eye ruler is a meridian compass which optionally overlays the plaque suture eyelet coordinate meridians.
Drag the center marker of the compass to the center of the cornea and drag the sizing handle on the perimeter so that the compass perimeter outlines the limbus and adjust the axial plane (either the 180 degree toric angle or the 9 and 3 o'clock indicators) to the eye.
From the contextual menu you can customize the compass to display either clock hours or toric angles, enable or disable the suture meridian overlays, and edit the colors in the properties sheet.

Ultrasound Image Calibration

In general, it is not necessary to calibrate ultrasound images unless you wish to use the Eye modeling tool with the ultrasound image.
To calibrate an ultrasound image you must first activate the ultrasound image and then enable and position the ultrasound ruler in the Image window.
Click the Ruler button in the Ultrasound controls group to display Plaque Simulator's ultrasound calibration ruler. Although PS supports up to 4 rulers per image, only ruler #1 may be used to calibrate an image. Optional rulers #2 through 4 share the image calibration established by ruler #1. Ruler options are enabled and accessed from the Properties... item of the ruler button's contextual menu.
Drag the ruler's control boxes delineate an object of known dimension. The control boxes change from the ruler color property to yellow when the boxes are horizontally or vertically aligned.
With the ruler still enabled, click the Calibrate button in the ultrasound controls group to open the calibration dialog sheet.
Enter the distance in mm corresponding to the delineated object (e.g. the base of the tumor is known to be 9.8 mm).
Click the OK button to exit the sheet.