Plaque Simulator fuses images and measurements derived from CT (or MR), fundus camera photographs and ultrasound studies to build a three dimensional model of each patient's eye and tumor. A simulation session begins by preparing these images for import into Plaque Simulator.

• Prepare the fundus collage.
• Prepare CT images using OsiriX.
• Prepare ultrasound measurements.

After the images have been prepared, they will be imported into Plaque Simulator, typically as .jpg files, and calibrated. A 3D model of the eye will be created and the tumor location and altitude entered. Please review these links before proceeding with this tutorial.

• Entering patient identifiers.
• Calibrating the CT images.
• Measuring the eye size.
• Calibrating the fundus collage.
• Digitizing the tumor.

Full size versions of the screen captures in this tutorial can be viewed by simply clicking on the pictures. Use the 'back' button of your browser to return to the tutorial after downloading the full size picture.

From the File menu:

• If you have been working on other plans since launching Plaque Simulator, select New Patient...to reset Plaque Simulator and create a new patient.

From the Plan menu:

• If the Image window is not visible, bring it to the front by selecting the Images item from the Window menu (in the menu bar at the top of the screen).
• Increase the window size to fill a significant portion of your available screen by dragging the lower right corner of the window, or by opening the Window Size dialog and selecting one of the preset sizes or manually entering dimensions.
  
  
  

• Click the Axial button in the CT controls group.
• A file navigation dialog will open.
• The intermediate tutorial files can be found in the Tutorials folder which is located in the Plaque Simulator Patients folder which is in the Documents folder at the root level of your system hard drive. These files and folders should have been installed as part of your original installation or update of Plaque Simulator.
• Open the image entitled Axial.jpg.

• Click the Equator button in the CT controls group.
• A file navigation dialog will open.
• Open the image entitled Equatorial.jpg.

• Click the Sagittal button in the CT controls group.
• A file navigation dialog will open.
• Open the image entitled Sagittal.jpg.

• Click the Coronal button in the Tumor Apex controls group.
• A file navigation dialog will open.
• Open the image entitled T-Coronal.jpg.

• Click the Meridian button in the Tumor Apex controls group.
• A file navigation dialog will open.
• Open the image entitled T-Meridian.jpg.

• Click the Ultrasound button in the Tumor Apex controls group.
• A file navigation dialog will open.
• Open the image entitled US.jpg.
• Note that the tumor height is 2.2 mm at the apex and 9.8 x 7.4 mm at the base.

• Click the Fundus button in the Fundus controls group.
• A file navigation dialog will open.
• Open the image entitled Fundus.jpg.

• As detailed in this link, Calibrate the axial image first and then the other four CT reconstructions.
• In the CT controls group, enable the CT Ruler, open the ruler diameter to 50 mm in the axial image, and click the Calibrate button.
• Note: because all 5 multiplanar reconstructions were exported from OsiriX without changing magnification or window size, they all share the same calibration factor, so you only need to calibrate the axial image and copy the calibration to all the other CT reconstructions.

• Using the axial reconstruction, measure the size of the eye with the eye sizing tool as described in this link.
• Then enable (by clicking the Eye button), position and orient eye sizing tools on the other CT reconstructions as illustrated.
• The appearance of the eye sizing tools varies according to the tasks associated with each type of image. For example, only the axial eye tool includes the yellow colored portion of the tool that measures the angle between the posterior pole and the center of the optic disc.

• Select the fundus image by clicking the Fundus button in the Fundus contols group.
• As described in this link, Calibrate the fundus collage.
• Be sure to set the number of photo centers (e.g 3 total in this example) from the popup menu. If there are more than 5 photos in the collage, choose those closest to the tumor.
• Position photo centers #2 and #3 and adjust the photo diameter slider as illustrated.
• Note: there is actually a portion of a 4th photo visible in this collage but because it is mostly obscurred by the other photos it can be ignored.

• If the Retinal Diagram window is not visible, bring it to the front by selecting the Retinal Diagram item from the Window menu (in the menu bar at the top of the screen).
• As described in this link, digitize the tumor base perimeter.
• In the status line just below the title bar of the Retinal Diagram window, observe that the maximum length and the radial length of the tumor base are both 9.9 mm which compares well with the 9.8 mm expected from the ultrasound measurements. The maximum width and the circumferential width are 7.0 mm which compares well with the 7.4 mm expected from the ultrasound measurements.

Before the fundus collage is warped.

After tracing the tumor perimeter, using the original collage for best image quality, Plaque Simulator will circumferentially warp (aka auto correct) the tumor perimeter for mapping onto the polar diagram and will offer to warp (aka auto correct) the fundus image as well.

After the fundus collage has been warped for correct mapping onto the polar retinal diagram.

You can manually enable or disable fundus image warping using the Auto Correct Collage item in the contextual menu attached to the Photo button.

When checked, the Transparent Backgound item of this menu makes the black (or, optionally, another color of your choice) background of the original fundus collage transparent.

• From the ultrasound measurements, the tumor shape is dome-like and the height at the apex is 2.2 mm.
• In the Tumor controls group of the Retinal Diagram window:
• Click the Dome button.
• Click the Apex button and set the tumor height to 2.2 mm and the base margin to 2 mm.

From the Plaque menu select Plaque Files.

From the Plaque Files menu select the EP917P file.

The 'P' at the end of the file name EP917P indicates that this file includes an embedded picture of the face of the plaque.

The EP917 plaque was selected because:

• The semi ellipsoidal shape (ie this plaque is ellipsoidal near the eyelets, but notched on the opposite side) and size make a good physical and dosimetric fit to this tumor.
• The wide notch allows the plaque to seat comfortably against the optic nerve.
• The collimating slots for the radionuclide sources provide some sparing of the region within the notch.

• You can drag and rotate a plaque on the diagram by setting the cursor controls to plaque mode. Click within the plaque perimeter to drag. The control and command keys rotate the plaque while dragging.
  
  
• Click the button labeled Center. The plaque will automatically center under the tumor with its suture eyelets balanced (equidistant from the limbus).
  
  
• Note the projection from the external sclera onto the retinal diagram showing the collision at the notched end of the plaque with the sheath surrounding the optic nerve.
• Rotate the plaque counterclockwise for a better fit between the optic nerve and the notch.
  
  

• Using the date controls and/or the date window, set the implant insertion date and time and then the removal date and time.
• In a subsequent step, you will calibrate your radionuclide sources to the same insertion date you choose here.
• Implant durations between 4 and 7 days (96 to 168 hours) are typical.
• The insertion and removal calendar buttons open the Calendar dialog where you can set date and time with an expanded user interface.
  
  
  


• In this tutorial, the implant is scheduled for insertion at 10 AM on October 17th, 2012 with a duration of 168 hours.
• By default, Plaque Simulator sets the prescription (Rx) to 85 Gy at the apex of the tumor, accept that Rx for now.
• The initial state of the 'Plaque 1 Central AXis table' is zero because there are no radionuclide sources in the plaque.

• When the EP917P plaque file was opened, the initial states of the dose calculation mode buttons below the title bar of the window were automatically set to:
• Linear, anisotropic source
• No silicone seed carrier
• Gold flourescence corrections enabled
• No air scatter correction
• No shell collimation (Note: shell collimation is redundant for Eye Physics slotted plaques such as the EP917 where virtually all collimation occurs at the slot edges adjacent to the seed rather than at the surface of the plaque face or shell. In this case, disabling shell collimation greatly accelerates the collimation ray tracing computation.)
• Slotted collimation enabled
• Do NOT change the calculation settings.

• Click the Sources button to open the Inventory list dialog.
  
  

In the Inventory List dialog:

• Select Show only: and set the menu to the model of radionuclide source you intend to use (e.g. I-125 IAI-125A is a Plaque Simulator physics file for one of the IsoAid products, configured for specification of source strength as activity in mCi.
• Click the Add button to open the inventory entry editor and create a new inventory entry for the selected model source.

• Name the entry 'tutorial'.
• Set the number of sources to 17 of 17 (the model EP917 has slots for up to 17 sources).
• Set the source strength range as 1.0 to 1.0 mCi.
• Set the assay date to be the same as the implant insertion date you established a few steps earlier in this tutorial.

• Click the list to select the just created entry.
• Click the OK button to exit the dialog.

In the Plaque window, with the Retinal Diagram window visible alongside.

• Click the Load button in the Plaque window.
  
  
• All of the slots in the plaque will be filled with the currently selected inventory entry.
• Click the Labels button.
  
  
• Enlarge the Plaque window if you wish for a better view.

• Set the cursor mode to Load slot.
  
  
• Note:
• The other cursor modes are for designing new plaques.
• In the Plaque window, the cursor changes its appearance to indicate when you are directly over a source placeholder and can load or unload it by clicking.
• To create a source loading pattern that better conforms to the shape of the tumor base, remove the two sources that surround the notch by clicking on them in the Plaque window. The inventory count will be automatically updated.

• By default, Plaque Simulator sets the prescription (Rx) to 85 Gy at the apex of the tumor, accept that Rx for now.
• The initial state of the 'Plaque 1 Central AXis table' is based upon the initial choice of 15 1.0 mCi sources in the plaque. The dose at the tumor apex (112.463) is greater than the initial Rx of 85 Gy.
• Click the Implant Calculator button.
  

• Click the Calc. Sources button. This will rescale the distribution of source strengths in the plaque (currently uniform) to deliver the prescription of 85 Gy to the tumor apex in 168 hours.
• If an alert appears requesting to update the inventory to the new seed strength, respond Yes.

• The Prescription (Rx) window will update to reflect the new source strengths of 0.79 mCi per source.
• Observe that the 'Plaque 1 Central AXis table' now lists the dose at the Rx point (tumor #1 apex at 2.2 mm) as 85 Gy.

• Right-click on the Isodose button to display the contextual menu and select MyFavorite.idos. Note: by default, on MacOSX, simultaneously pressing the control button on the keyboard while clicking the cursor with a single button mouse is functionally the same as clicking the right button of a multiple button mouse.
• The column of checkboxes simultaneously enables isodose lines on the retinal diagram, the meridian and coronal planar surfaces, and in the Patient Setup window.
• The column of radio buttons selects a 3D isodose surface (e.g. 85 Gy) for 3D rendering in the Patient Setup window.

• Click the Dual pane side-by-side button. This will double the window width to display both the meridian and coronal planes.
  
  
• Click the T-Cor button. This will translate the coronal dosimetry plane from its default starting position at the equator to intersect the tumor apex and overlay the tumor-coronal CT image based on the location and orientation of the tumor-coronal eye sizing tool in the Image window.
  
  
• Click the T-Mer button. This will rotate the meridian dosimetry plane to intersect the tumor apex and overlay the tumor-meridian CT image based on the location and orientation of the tumor-meridian eye sizing tool in the Image window. Note: by default, the dosimetry meridian plane passes through the center of the plaque, which, depending upon the plaque location, might not be directly under the tumor apex.
  
  

• Select Calculate 2D matrices. This calculates dose to the meridian and coronal planar surfaces, and to the retina.
• Select Calculate RDAH. This calculates the Retina Dose Area Histogram.

• The retina dose area histogram (RDAH) shows that, while the tumor base (brown line on the histogram) is entirely covered by the 85 Gy isodose line, the tumor + 2 mm retinal margin surrounding the base (green line on the histogram) is only about 85% covered at 85 Gy. The 2 mm margin surrounding the tumor base is similar to the PTV concept, it accounts for microscopic tumor extension beneath the retina and uncertainty in surgical placement of the plaque.
• We will need to revise the prescription in order to improve margin coverage.

• From the prescription popup menu, change the prescription from the Tumor 1 Apex at 2.2 mm to the item labeled Tumor 1 TAX (inner + x.xx mm). TAX is an acronym for Tumor AXis.
• In the Tumor Axis Prescription dialog set the TAX Rx height field to 4.5 mm from the inner surface of the sclera. Note: this will be approximately 5.5 mm from the plaque face.
• Click the Implant Calculator button again, or, if the Implant Calculator window is still visible, simply click the cursor in that window to bring it to the front.
  

• Click the Calc. Sources button again. This will once again rescale the distribution of source strengths in the plaque (currently uniform) to deliver the prescription of 85 Gy to the tumor apex in 168 hours at the new prescription point of 4.5 mm on the tumor axis.
• If an alert appears requesting to update the inventory to the new seed strength, respond Yes.

• The Prescription (Rx) window will update to reflect the new source strengths of 1.35 mCi per source.
• Observe that the 'Plaque 1 Central AXis table' now lists the dose at the Rx point (Tumor 1 TAX inner+4.50 mm) as 85 Gy.
• The dashed blue line in the table shows that the Rx dose of 85 Gy falls between 5 and 6 mm from the surface of the plaque face as expected.

• Select Calculate 2D matrices. This calculates dose to the meridian and coronal planar surfaces, and to the retina.
• Select Calculate RDAH. This calculates the Retina Dose Area Histogram.

• The retina dose area histogram (RDAH) shows that the tumor base (brown line on the histogram) is again entirely covered by the 85 Gy isodose line. However, with the new prescription point at 4.5 mm on the tumor axis, coverage of the tumor + 2 mm retinal margin surrounding the base (green line on the histogram) has increased from 85% to about 99% at 85 Gy.

Prescribing to a height greater than the tumor apex in order to assure base coverage is consistent with the COMS requirement to prescribe to 5 mm for tumors less than 5 mm tall. Note, however, that dose to the macula (orange line in the RDAH) increases noticably because the tumor borders the macula in this case, and dose to the remainder of the retina increases slightly as well. Fortunately, dose to the vitreous humour surrounding the tumor dome is not of biological concern, and dose to the lens is of minor concern because resulting cataracts can be treated with intraocular implants. The choice of prescription height in a case like this is a matter of clinical judgement.

• Select Allocate 3D Matrix.
• Select Calculate 3D Matrix.
• The 3D matrix takes awhile to calculate.
  

• Click the 3D Dose button to render the selected 3D isodose surface.
  
  
• Click the setup appearance button to open the appearance window window.
  
  
• Experiment with the 3D model and the appearance controls to create pictures for the setup document.

The Treatment Plan is a 3 page document that summarizes the entire simulation. Page 1 provides a table of patient identifiers, date & time of treatment, some radionuclide, plaque and tumor properties, a facial picture of the plaque and a miniature retinal diagram showing tumor location.

On page 2 there is a table of point dose calculations along the central axis of the plaque (or tumor), at the prescription point, lens, macula, etc..., a thumbnail of the fundus image, and an optional picture. The default picture is a radiation safety survey form.

Page 3 contains thumbnails of the CT or MR images used to model the eye and any ultrasound images used to measure or model the tumor dome.

The Loading Diagram document is a "road map" to the plaque. Everything the person or company (e.g. IsoAid) needs to manufacture the seeds and assemble the plaque is in this document.

The Retinal Diagram document is a VERY useful "road map" to have in hand during surgery because it illustrates the tumor and plaque location, muscle insertion regions, lists the suture eyelet coordinates and the distance between the coordinates. Everything the surgeon needs to place the plaque at the planned position is in this document.

The Histogram document prints the Retina Dose Area Histogram (RDAH). The RDAH is a metric for comparing competetive treatment plan options.

The Setup document prints the contents of the 3D Patient Setup window.