In this tutorial we will create a model of the COMS 10 mm plaque. Please note that finished models of all of the COMS, ROPES, and BEBIG plaques are selectable from menus in Plaque Simulator. End users of these commercially available plaques may never need to create plaque models. The COMS 10 mm plaque was selected as the object of this introductory tutorial because it is a small, simple plaque with only 5 I-125 seed slots and therefore a logical choice for illustrating the process.

Step 1: Create a picture of the new plaque & carrier. When creating a new plaque model, begin by using your digital camera or flatbed scanner to create a frontal picture of the plaque with carrier inserted and a calibrating ruler. This is a picture of the COMS 10 mm plaque and carrier. Orient the plaque as symmetrically as possible with the suture eyelets towards the top of the picture. Include a ruler with 1 mm increments along the top edge of the picture. The picture resolution should be at least 500x500 pixels. A good file format to use is ".jpg". Sample pictures of the COMS 10 and 22 mm plaques are included in the Plaque Simulator download. These pictures can be loaded into the plaque window and edit shell dialog to assist with building the models.

Step 2: Find a similar plaque model as a starting point. In Plaque Simulator bring the Plaque window to the front by clicking in the window or by selecting it in the Window menu. Click the Plaque #1 button. From the Plaque menu, find an existing plaque with a similar shape and spherical radius of curvature as the new plaque you want to model. For the purposes of this tutorial we will load the slightly larger diameter COMS 12 mm plaque from the COMS Plaques menu.

Step 3: Load the picture of the new plaque From the Plaque menu select Load Plaque Picture.

Step 4: Open the picture file In the file navigation dialog find your picture and open it as illustrated above. The picture will become the background of the Plaque window, but it needs to be calibrated.

Step 5: Calibrate the plaque picture. To calibrate the picture, first activate rulers in the Plaque window. You can drag the picture by command-clicking on it, and magnify the picture using the zoom controls at the bottom of the window. Adjust the picture magnification (to 0.80 in this example) and position until the ruler marks along the top edge of the picture match the ruler marks in the Plaque window as illustrated here. The picture is now calibrated.

Step 6: Align centers. Now drag the picture (by command-clicking on it) until the center of the plaque in the picture and the center of the plaque model are aligned.

Step 7: Open the Edit Plaque Shell dialog. Select Edit Plaque Shell from the Plaque menu. This opens the Edit Plaque Shell dialog.

Step 8: Remove source slots and suture eyelets. In the Delete all group box click the Slots and Eyelets buttons. If the suture eyelets on the model happen to be at the correct positions you can leave them. In this tutorial we will remove them to illustrate the process.

Now we are left with just the 24 perimeter defining nodes of the shell.

Step 9: Select a control node. Drag one of the perimeter control nodes to the outside edge of the shell (or select and edit one of the items in the control node list). In this example node 6 (90°) has been selected and its radius set to to 5.5 mm.

Step 10: Create a circular shell. In the Shell group box, click the Circular button. The radius of all nodes will be matched to that of the currently selected node.

Now that we have a circular shell of 11 mm outer diameter, we need to describe the plaque and source carrier materials and add suture eyelets.

Step 11: Adjust shell & carrier parameters. In the Shell group box, click the Carrier button. This will open the Shell & Carrier Parameters dialog.

In the Shell parameters group box we indicate that the shell is made of gold and has a perimeter lip. The thickness of the shell is 0.5 mm, the height of the lip is 3 mm, the total thickness on the central axis is 2.75 mm and the spherical radius of curvature is 12.3 mm. The transmission parameter should normally be set to -1 to indicate that transmission though the shell depends on the energy characteristics of the isotope being loaded into the plaque. If you enter a value here it will override the physics data of the isotope.

In the Carrier parameters group box we indicate that this COMS plaque has a Silastic (silicone) carrier that can rotate inside the shell and that the carrier is intended to hold linear sources. Click the OK button to exit this dialog.

The Misc and Beta patch source parameters are accessible here for research and debugging purposes beyond the scope of this tutorial. There is generally no reason for end users to modify these values.

Step 12: Rotate the picture if necessary. Back in the Edit Plaque Shell dialog, rotate the picture as necessary to align the suture eyelets with the control nodes. In this example the picture has been rotated 4° CW (displayed as 356° CCW) so that the 6 nodes at 15°, 45°, 75°, 285°, 315° and 345° align with the eyelets in the picture.

The 24 point default perimeter has nodes at 15° increments. If the sutures don't line up over existing nodes, add more nodes to the list as necessary. When you click the Add button in the Control node list a new node is added after the first currently selected node. For example, if you wanted to add a new node at 97.5° select node 6 (90°) and then click Add. Adding nodes is not illustrated here.

Step 13: Add 1st suture eyelets. Option-click on one of the control nodes that you wish to add suture eyelets to. The Suture Eyelet dialog will be displayed. Creating suture eyelets is complex and may require several iterations of trial and error to find the best parameters. The Setup and Plaque windows will update as you change the parameters. Suitable parameters for COMS type eyelets are illustrated here.

Step 14: Add remaining suture eyelets. Repeat this process for each suture eyelet. Click the OK button to exit the dialog and return to the Plaque window.

Step 15: Align the slots. Back in the Plaque window we will now add source slots to the plaque. In this case we are actually adding the slots to the silastic carrier. Set Carrier rotation to 0° using the Plaque window's rotation control. Control-click (or right mouse button) on empty space in the control dial (or use the Rotate Plaque menu) and change the control's context to the picture. Rotate the picture until its source slots are as symmetric as possible (some plaque designs may not have symmetric patterns of slots) and the central slot vertical.

The picture has now been rotated from 356° (ie 4° CW) that was used to create the shell, to 1° CCW. The slots are now symmetrically aligned and the center slot is vertical.

Step 16: Add slot pattern. Open the Add/Delete Patterns dialog from the Plaque menu.

From the Pattern group box radio buttons select a Circular pattern and choose r, Beta & Tilt as the data entry mode. Set the number of slots to 4, pattern ID to 0, r to 2.87 mm, Beta to 45°, Tilt to 90° and the seed offset (distance from the carrier surface to the seed center) to 1.4 mm. You can ignore the parameters in the Slot group box which are for plaques with collimating slots and therefore do not apply to COMS type plaques with non-collimating carriers. Click the Add button to add the slots (1..4) and then click OK to exit the dialog.

Step 17: Add center slot. Open the Add/Delete Slots dialog from the Plaque menu.

In the Source location group box ignore the Slot # popup menu (it is used for editing existing slots). Set the radio buttons for r, Beta & Tilt data entry mode. Set the pattern ID to 0, r to 0 mm, Beta to 0°, Tilt to 0° and the seed offset (distance from the carrier surface to the seed center) to 1.4 mm. You can ignore the parameters in the Slot group box which are for plaques with collimating slots and therefore do not apply to COMS type plaques with non-collimating carriers. Click the Add button to add the slot (#5) and then click OK to exit the dialog.

Step 18: Save the plaque. From the File menu choose Save plaque as... to open the file navigation window.

Plaques should generally be saved in the Plaques folder in the Plaque Simulator Data folder. You may optionally add the ".iplq" tag to the end of the file name.

When you update the Plaque Files menu or restart Plaque Simulator your new plaque will appear in the Plaque Files menu.

The finished plaque looks like this when it is loaded with 5 model 6711 I-125 seeds. The suture eyelets, shell, seeds & slots should match the picture when the proper plaque and carrier rotations are applied.