Horos and OsiriX Tutorial for Plaque Simulator

What are Horos and OsiriX?

Horos and OsiriX are DICOM listeners and viewers that can manipulate 3-D data sets and export reconstructions of axial, equatorial and sagittal planes which bisect the affected eye as .jpg files. Other reconstructions of interest are the meridian and coronal planes which intersect the tumor apex. OsiriX predates Horos but is now a paid, FDA approved product. Horos (son of Osiris) is derived from the same code base as OsiriX but is free to use. The user interfaces are nearly identical.

These 6 reconstructions will be imported into Plaque Simulator and used to measure the size and shape of the eye and, in conjunction with ultrasound images and fundus photos, to determine the tumor size, shape and location within the eye.

To install Horos:

  • Download Horos and install it on your MacOSX computer.
  • Horos (version 4.0.0 and greater) is a free 64-bit application that will run under MacOS 10.15 Catalina and subsequent versions of MacOS.

To install OsiriX:

  • Download OsiriX and install it on your MacOSX computer.
  • The paid version of OsiriX is an FDA approved 64 bit application that will run under MacOS 10.15 Catalina.
  • The free OsiriX Lite is a 32-bit application and is not compatible with MacOS 10.15 Catalina and subsequent versions of MacOS which require 64 bit applications.

Example of Plaque Simulator fusion of 3D model of eye and plaque with fundus photo and meridian CT reconstruction through the tumor apex with isodose lines.

The 6 reconstructions for Plaque Simulator

These are the 6 multi planar reconstructions for Plaque Simulator that you will create using Horos or OsiriX


Axial meridian plane bisecting the eye and intersecting the optic disc (3 to 9 o'clock meridian on the retinal diagram).


Equatorial plane bisecting the eye.


Sagittal meridian plane bisecting the eye (12 to 6 o'clock meridian on the retinal diagram)


Coronal plane through posterior sclera and nerve.


Meridian plane bisecting the eye through the tumor apex.


Coronal plane intersecting the tumor apex.

Preparing the reconstructions
  • Horos and OsiriX are comprehensive MacOSX DICOM listener clients that can receive images over your local network. In this tutorial, however, we will assume you are working with a set of transaxial CT images that cover the orbit at <= 3 mm spacing, and that the images were received on portable media such as a CD, DVD or USB memory stick.
  • Download and install Horos or OsiriX as described above.
  • Launch whichever application you installed (Horos or OsiriX).
  • With Horos or OsiriX running, drag a folder of DICOM images onto the patient database viewer window of the application, or insert a disk containing the patient's DICOM images into the optical drive of your computer.
  • The application will find and load the images from portable media. If it doesn't automatically find the images, open the CD (or portable device) from the MacOSX Finder and drag the folder containing the images onto the application window or its icon in the dock.
  • The loaded image sets will appear in the patient database viewer window of the application.
  • Double-click on the desired study: e.g. Axial slices with 2 mm resolution.
  • A new window will appear.
  • Click on the 2D/3D button at the top of the window.
  • Select the 3D Curved-MPR (Multi Planar Reconstruction) menu item.
  • Adjust the three orthogonal views to align with the appropriate eye.
  • Export axial, coronal, sagittal, tumor-coronal and tumor-meridian reconstructions as .jpg files for subsequent importation into Plaque Simulator.

Launching Horos or OsiriX: The initial screen

The thumbnail images beneath the patient list represent the available studies for the selected patient. Double-click the thumbnail image of the desired study. The selected study will appear in its own separate window.


Opened study

Navigate through the opened study using the horizontal slider located just below the title bar (EYE FOR EYE PLAQUE-KW) of the window that displays the images.


Controls and buttons
  • In the tools panel at the top of the screen, click the cursor on the button labeled 2D/3D. It has a gear shaped icon. The 2D/3D dropdown menu will appear.
  • Select the 3D Curved - MPR menu item, the second item on the list.
  • A new window with 4 panes will appear showing three orthogonal reconstructions and a blank pane.

The 3D Curved-MPR 4-pane window
  • SyncZoom.png In the window toolbar (upper right corner), be sure the Sync Zoom control is enabled. If the control is not visible, increase the window width until you can see control. Once enabled, you can resize the window as you like. When Sync Zoom is enabled, changes in one pane will be propagated to the other panes.
  • The image manipulation tools are on the left side of the header section.
  • Select a tool from this group in the header by clicking on the desired tool button.
  • OsiriXWindowLevel.png

    Adjust window & level to maximize contrast of the sclera and tumor.

  • Use the translation tool to move the image and the axes crosshairs.
  • OsiriXTranslate.png
  • Quadrant I: Coronal reconstruction in the upper-right pane.
  • Quadrant II: Sagittal reconstruction in the upper-left pane.
  • Quadrant III: Axial reconstruction in the lower-left pane.
  • Quadrant IV: The lower-right pane is empty.
  • Placing the cursor over the intersection of the axes crosshairs in any image will produce a cursor that translates the two axes in unison. Drag the crosshairs to the center of the affected eye.
  • Placing the cursor over an axis away from the intersection will produce a rotation-cursor.
  • Drag and rotate the axes such that the yellow-orange axis marks the left-right bisecting plane of the eye (ie the sagittal meridian, aka the 12 to 6 o'clock meridian on the retinal diagram), the blue axis marks the coronal plane with the largest diameter (ie the approximate equator of the eye), and the purple axis marks the bisecting (inf-sup) axial meridian plane of the eye through the optic disc (3 to 9 o'clock meridian on the retinal diagram).
  • UPPER-RIGHT: In this coronal-equatorial pane, rotate the purple axis so that it bisects (inf.-sup.) BOTH eyes. Assuming contralateral symmetry of the orbits, this rotation will correct for the most commonly encountered rotation of the head in the scanner. This purple axis corresponds to the Y-axis of Plaque Simulator's 3D model of the eye. The yellow-orange axis corresponds to the Z-axis of Plaque Simulator's 3D model of the eye.
  • LOWER-LEFT: In this axial image the yellow-orange axis corresponds to the X-axis of Plaque Simulator's 3D model of the eye. It passes through the apex of the cornea, the midpoint of the lens, and the posterior pole of the eye. The blue axis corresponds to the Y-axis of Plaque Simulator's 3D model, representing the transition from the posterior hemisphere to the anterior oblate spheroid elements of the 3D model.
  • UPPER-LEFT: In this sagittal image the blue axis becomes Plaque Simulator's Z axis, also representing the transition from the posterior hemisphere to the anterior oblate spheroid elements of the 3D model. The purple axis is Plaque Simulator's X axis.
  • Note: because the patient's eye may not have been looking "straight ahead" during the scan, the axial, equatorial and sagittal reconstructions of the eye as expected by Plaque Simulator might not be parallel to the axial, coronal and sagittal planes of the body or the CT scanner. It is important to provide Plaque Simulator reconstructions that correspond to the geometry expected by Plaque Simulators 3D model of the eye.

Prepare axial, equator and sagittal reconstructions


(upper left pane)



(upper right pane)



(lower left pane)

  • For best results with PS, the axial, coronal and sagittal reconstruction panes should be in the range 900 to 1000 pixels wide.
  • Magnify to taste.
  • OsiriXmagnify.png

    Use the magnifier tool to adjust the CT image size so that the eye occupies about half of the pane width, is not obscured by text overlays and a total of at least 5 green tick marks, one centered, two to left of center, and 2 to the right of center are clearly visible along the horizontal calibration ruler near the bottom of the image. In the example below, the 5 tick marks are being pointed at by 5 green arrowheads. Make sure the tick marks are not obscurred by text overlays.

  • When the reconstructions are ready, click on the axial pane (lower left quadrant) to select it.
  • A colored BORDER will appear to indicate the selected pane.
  • Click on the File menu > Export > Export to JPEG (or use keyboard shortcut command-shift-E)
  • Name the file using the PS6 naming conventions (e.g. 'axial.jpg' for the axial image).
  • Navigate the file save dialog to find the folder you previously created for the patient (e.g. somewhere in Documents/Plaque Simulator Patients) or a generic location in which to save files exported from OsiriX or Horus.
  • Accept the default .jpg settings and save the file in the patient's folder or your generic location.
  • Save the coronal and sagittal images in the same general way except with the appropriate file names (e.g. sagittal.jpg and equator.jpg). The axial meridian image is required by PS, the sagittal meridian and equatorial planes are optional but very useful and highly recommended.

Prepare the nerve-coronal reconstruction

In the axial pane (ie the lower-left pane), drag the axes crosshair posteriorly (in Plaque Simulator's eye coordinate system) until the blue line, which represents the coronal reconstruction, passes through the posterior sclera about 0.5 to 0.8 mm posterior to the pole (in PS the posterior pole is located at the inner sclera) and the optic nerve where it connects to the eye. Assure that the yellow-orange axis continues to pass through the posterior pole. The nerve-coronal reconstruction appears in the upper-right coronal pane. Save the nerve-coronal image in the same manner you saved the axial and equator images previously except with the file name "nerve.jpg". You might also save the axial reconstruction with file name "n-axial.jpg" because it documents (the blue axis line) the location of the nerve-coronal plane. In the nerve-coronal reconstruction you should be able to clearly see a bit of the sclera surrounding the axes crosshair and the cross-section of the nerve where it connects to the eye on the nasal (medial) side of the axes crosshair.


(upper-right pane)


Prepare meridian and coronal reconstructions through the tumor apex
  • In the axial (lower-left) reconstruction pane, drag the axes crosshair back toward the center of the eye and in the coronal reconstruction pane (upper-right) rotate the crosshair to create both coronal and meridian reconstructions that intersect the tumor apex. The meridian reconstruction will appear in either the the upper-left or lower-left quadrant depending upon how you rotated (ie CW or CCW) the crosshairs in the coronal pane. In this example the tumor-meridian reconstruction appears in the upper-left quadrant associated with a CCW rotation of the yellow-orange axis in the coronal pane to pass through the tumor apex.
  • Export as .jpg files in the same way as the axial, equatorial and sagittal images. Name the tumor-meridian reconstruction 't-meridian.jpg' as specified in the PS6 naming conventions. Name the tumor-coronal reconstruction 't-coronal.jpg'.


(upper-left pane)



(upper-right pane)