Treatment Simulation: Anterior Tutorial

The tutorial involves an anteriorly located medium height tumor that extends from the limbus to the equator for which fundus images were not available. Only the posterior retinal diagram is required for this tutorial. For anterior tumors that extend beyond the limbus (e.g. iris tumors) or between the cornea and lens you will want to learn how to use the anterior retinal diagram. Also, many new plaques designed for anterior tumors (including the models EP2028, EP2335, EP2339 and EP2343) have been introduced since this tutorial was created. This case was selected for the tutorial because it illustrates treatment planning using CT and ultrasound alone. You will gain experience:

  • Using the multiple image loader.
  • Approximating the tumor location, shape, size and apex using only CT and ultrasound images.
  • Using the standard tumor sheet to set the model's tumor location, shape, size and apex to match the CT and ultrasound images.
  • Using the model EP2025 slot collimated plaque.
  • Using the retina dose area histogram (RDAH) to evaluate dosimetric coverage of the tumor base and its surrounding margin.
  • Calculating scleral suture coordinates.
  • Printing documents.
AnteriorTutorialIntro


These are steps that you will accomplish in this tutorial.

1. Preparing for the anterior tutorial

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. Note: this tutorial does not use fundus images.

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.

Please familiarize yourself with the basics of image based planning for eye plaques by following the links below before proceeding with this tutorial.

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.

Please familiarize yourself with the Basic and Posterior tutorials before proceeding with this tutorial.


2. Find the tutorial images

The sample images used in this tutorial can be found in Plaque Simulator Patients/(Tutorials)/PS6/Anterior Tutorial which should have been installed in the Documents folder of the logged-in PS user as part of your original installation or update of Plaque Simulator.


AnteriorTutorialInFinder

3. Launch PS and create a new patient plan

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.
PatientIDs

From the Plan menu:

  • Select Patient IDs... to open the Patient ID window.
  • Name this planning session 'Anterior Tutorial'.
  • Optionally fill in any other patient or institutional identifiers.
  • Leave the plan name blank.
PatientIDs
ATPatientIDs

4. Open the Images window

If the Image window is not visible or frontmost, make it the frontmost window by clicking the cursor in its window or by selecting Images from the Window menu (in the menu bar at the top of the screen).

Images
  • Increase the window size to fill a significant portion of your available screen by dragging the lower right corner of the window, or by clicking the window sizing button
    WndwSize to open the Window Size sheet and selecting one of the preset sizes (e.g. 512 x 512) or manually entering dimensions.

    ImageWindowResize
  • ImageWindow512

    5. Open the MPR and US images
    AxialPlane

    In the Image window

    Hold down the Option button on the keyboard while clicking the Axial button in the MPR controls group to load multiple images.


    CTGroup
    • A file navigation dialog will open.
    • Navigate to the patient folder Anterior Tutorial.
    • Open the image entitled axial.jpg.
    • All of the other images in the patient folder that adhere to the PS image file naming conventions will open at the same time.
    • Note 1: This tutorial does not include a fundus image. It is not required that all of the possible images be present in the patient folder. The multiple image loader will simply not find a file named fundus in this patient folder, so a fundus image will not be loaded.
    • Note 2: If you have not yet entered a name in Patient IDs..., PS will suggest a patient name based on the name of the folder (e.g. Anterior Tutorial) from which the images are loaded.

    • Using the image enhancement tools in the toolbar, adjust the image brightness & contrast (or bias, gain and level) to best visualize the sclera.
    • Calibrate the axial image using the MPR ruler and copy the calibration to the other MPR images as described in Importing and calibrating MPR images. You can safely copy the axial calibration to the other MPR images because all of the MPR images in this tutorial were created in OsiriX using exactly the same window settings.

    • AxialCalibrationSheet

    • Fit the interactive Eye tool to the eye as described in Fitting the eye model.
    OpenAxial
    AxialOpened

    6. The equator image
    EquatorialPlane

    In the Image window

    • The equator image will already be calibrated because you copied the axial calibration to all the other MPR images.
    • Center the Eye tool on the eye. The eye tool appearance varies with the image context, for equatorial and coronal images the tool represents the equator circle of the retinal diagram.
    • Rotate the tool using the red handle so that 12 o'clock is superior in the image.
    • If you aligned the yellow and purple crosshairs (representing the sagittal and axial planes of the eye) accurately when you created the equatorial image in OsiriX, the vertical yellow line in the image should pass through 12 and 6 o'clock on the eye tool, and the purple line through 3 and 9 o'clock as illustrated.
    EquatorOpened

    7. The sagittal image
    SagittalPlane

    In the Image window

    • The sagittal image will already be calibrated because you copied the axial calibration to all the other MPR images.
    • Center the sagittal Eye tool on the eye.
    • Rotate the tool using the red handle to fit the image.
    • If you aligned the blue and purple crosshairs accurately when you created the sagittal image in OsiriX, the vertical blue line which represents the equatorial plane in the image should should be close to the white and green equatorial handles on the PS sagittal eye tool, while the purple line, which represents the axial plane, should pass through the apex of the cornea and posterior pole of the PS tool. The OsiriX alignment was close but not perfect in this example.
    SagittalOpened

    8. The tumor-coronal image
    T-CoronalPlane


    CTGroup

    In the Image window

    • The tumor-coronal image will already be calibrated because you copied the axial calibration to all the other MPR images.
    • The eye tool appearance varies with the image context, for equatorial and coronal images the tool represents the equator circle of the retinal diagram. Center the Eye tool on the eye and rotate using the red handle to match its alignment on the equatorial image.
    • The coronal eye tool always represents the diameter of the eye at the equator. The tumor-coronal plane may not be near the equator, so it may be smaller in diameter than the tool.
    • Note that the yellow crosshair line in the OsiriX image now represents the tumor-meridian plane rather than the sagittal plane as it was in the equator image.
    TCorOpened

    Enable angle measurement by clicking the Angle button (found just below the ruler button and to the right of the calibrate button) in the MPR controls group. This will add an angle indicator to the ruler tool and the angular reference handle will become tinted yellow or green. Drag the ruler reference handle over 12 o'clock on the eye tool and its diametrically opposite handle over 6 o'clock as illustrated below.

    TCorAngle1

    Drag the angle indicator handle to measure the clock hour (e.g. 8:37) at the anterior edge of the tumor.

    TCorAngle2

    Drag the angle indicator handle to measure the clock hour (e.g. 6:17) at the posterior edge of the tumor.

    Disable the angle indicator by again clicking the Angle button and then drag the ruler tool to measure the tumor height (e.g. 6.03 mm) and the circumferential base dimension (e.g. 13.04 mm) as it appears in the coronal plane.

    TCorHeight
    TCorBase

    9. The tumor-meridian image
    T-MeridianPlane

    In the Image window

    • The tumor-meridian image will already be calibrated because you copied the axial calibration to all the other MPR images.
    • Center the Eye tool on the eye.
    • Rotate the tool using the red handle to fit the image.
    • If you aligned the crosshairs accurately when you created the tumor-meridian image in OsiriX, the purple line should pass through the apex of the cornea and posterior pole of the PS tool.
    • The blue crosshair line in the OsiriX image now represents the tumor-coronal plane rather than the equatorial plane as it was in the sagittal image.
    • The OsiriX alignment was very close but not perfect in this example.
    TMerOpened

    Drag the ruler tool to measure the tumor height (e.g. 4.51 mm) and the radial (meridian) base dimension (e.g. 11.03 mm) in the meridian plane. Note that the tumor height measurement depends upon the location of the tumor apex, the angle at which the imaging plane passes through the tumor and the curvature of the sclera below the tumor. As a result, the meridian plane is generally the most reliable image for measuring the tumor height.

    TMerHeight
    TMerBase

    10. The ultrasound image

    In the Image window

    • Click the U.Snd. button in the Ultrasound controls group.

    CTGroup
    • Enable the Ultrasound control group ruler tool.
    • Drag the tool to overlay the calibration ruler in the image (e.g. 20 mm).
    • Click the Ultrasound control group Calib. button and enter the calibration distance in the sheet.
    • Drag the ruler tool to estimate the inner scleral surface and then measure the tumor height (e.g. 4.52 mm, illustrated) and diameter. These measurements should closely match the tumor base and height as measured from the CT images.
    USOpened

    Drag the ruler tool to measure the tumor height (e.g. 4.52 mm) and the radial base dimension (e.g. 13.05 mm).

    USTumorHeight
    USTumorBase

    11. Create the tumor base

    In the Retinal Diagram window

    • If the Retinal Diagram window is not visible, bring it to the front by selecting Retinal Diagram item from the Window menu (in the menu bar at the top of the screen).
    • Click the Std. button and use the Standard Tumor sheet to model the tumor base.
    • The anterior of this eye is a noticeably oblate spheroid. Adjust the radial and circumferential tumor spherical size fields to achieve the desired tumor measurements (11.03 x 13.05 mm) in the oblate column (artificially highlighted in yellow in this figure).
    • Enter the best estimate of tumor apex height (e.g. 4.52 mm).
    • Adjust location longitude and latitude to place the anterior edge of the proposed standard tumor (plotted in orange) at the limbus and the circumferential edges between 6:17 and 8:37 o'clock as was determined in step 8 above.
    StandardTumorSheet

    12. Overlay tumor model on MPR images

    The objective of this step is to verify that the tumor location, shape, size and apex as created in the Retinal Diagram window is consistant with the tumor as it appears in the MPR images. Cross-sections of the tumor in the meridian and coronal dosimetry planes are tinted brown. The brown tinted regions should closely overlay the tumor in the MPR images. If the model and MPR do not overlay, further refinement of the model may be necessary.

    In the Planar Dosimetry window

    • In the toolbar controls, change the layout to side-by-side.
      LayoutControl
    • Note: the Meridian and Coronal buttons are now disabled (dimmed) because in this layout both planes are already displayed in side-by-side panes. These buttons are only active when the window is in single pane layout.
      LayoutControl
      In side-by-side layout, the meridian plane is always on the left, the coronal on the right.
    • Activate the meridian (left) pane by clicking anywhere within the pane. The active pane is indicated by a thin black frame around the pane and the matrix indicator in the lower right corner of the pane has a black background.
    • In the Overlay Image controls group along the right side of the window, click the T-Mer button.
    • Using the upper pair of buttons in the Rotate group
      RotateGroup
      rotate the meridian dosimetry plane projection (dashed purple line) to match the tumor-meridian imaging plane (represented by the diagonal yellow line in the OsiriX tumor-coronal image) or as an approximation to pass through the tumor apex in the Retinal Diagram window. The meridian plane appears as a translucent purple line bisecting the retinal diagram. You could also use the plaque control group center button in the Retinal Diagram window to achieve the same effect if Planes Track Plaque Motion is enabled. You may need to click the Flip 180 if the tumor appears on the wrong side of the eye when using meridian plane auto tracking and/or auto-centering.
    • Activate the coronal pane by clicking anywhere within the pane. The active pane is indicated by a thin black frame around the pane and the matrix indicator in the lower right corner of the pane has a black background.
    • In the Overlay Image controls group along the right side of the window, click the T-Cor button.
    • Using the lower pair of buttons in the Rotate group, translate the coronal dosimetry plane projection (dashed purple line) to match the tumor-coronal imaging plane (represented by the vertical blue line in the OsiriX tumor-meridian image).
      RotateGroup
    MeridianPlaneOnDiagram
    CompareMeridianWithMPR

    The Standard Tumor sheet always returns the tumor apex to a point directly above the geometric center of the elliptical tumor base. Observe that the apex of this tumor needs to be shifted anteriorly to better model the tumor and the measurements. Set the Retinal Diagram window cursor mode to drag apex in the toolbar and then nudge the tumor a bit anteriorly along the meridian plane projection until the tumor matches in the Planar Dosimetry window.

    DragApexAnterior
    AfterDraggingApex

    After moving the tumor apex slightly anterior the standard model and the CT images match nicely.


    13. Select a plaque

    In the Plaque Loading window

    From the Plaque menu select Plaque Files.

    PlaqueFiles

    From the Plaque Files menu select the EP2025P_AB file.

    PlaqueFilesEP2025PAB
    EP2025PABPOpened

    The EP2025 is a unique asymmetric variant of EP plaque with 4 suture eyelets. The 'P' near the end of the file name EP2025P_AB indicates that the file includes an embedded picture of the face of the plaque. The _AB at the end of the file name indicates that suture eyelets A&B have been preset for balancing the eyelets which has advantages for anterior tumors. The related file EP2025P is the same plaque except that eyelets A&D are preset for balancing which is a better orientation for posterior tumors.

    The EP2025 plaque was selected because:

    • The shape and size are a good physical and dosimetric fit for anterior tumors near the limbus.
    • The spacing between suture eyelets A&B is greater than the spacing between A&D, so the plaque face will curve above the edge of the cornea yet suture a few mm posterior to the limbus.
    • The deep collimating slots for the radionuclide sources create a steep dose gradient outside the tumor perimeter.

    14. Center the plaque under the tumor

    In the Retinal Diagram window:

    • You can manually drag and rotate a plaque on the diagram by setting the cursor to drag-plaque mode.
      DragPlaqueMode Click within the projection of the plaque perimeter on the retina to drag. The control and command keys rotate the plaque while dragging.
    • Clicking the Center button in the Plaque controls group
      PlaqueGroup will automatically center the plaque under the tumor base and rotate the plaque so as to balance the suture eyelets at equal distances from the limbus. Balancing the eyelets is not required, but it does slightly simplify surgical placement.
    • The small arrows at the corners of the rotation control rotate the plaque CW and CCW in 1 or 90 degree increments.
    • Rotate the plaque CCW to achieve a symmetric fit of the notch to the nerve as illustrated in figure 3 below.
    DiagramCentered

    Auto-centered, eyelets balanced


    PlanarCentered

    In the planar dosimetry window it becomes clear that the anterior edge of the plaque where it will be sutured needs to be tilted to fit to this noticeably oblate eye.


    15. Prepare to tilt the plaque

    In the Setup window:

    Open the Setup Appearance window and set the plaque to opaque and enable rendering of the meridian plane to more clearly see the fit of the plaque to the eye.

    SetupAppearance
    SetupCentered

    In the Setup window click the Offset button to open the Plaque Offset window.

    In the Plaque Offset window:

    • In the Show axes control group disable Eye axes and enable Plaque axes display.
    • Note that in order to tilt the plaque to fit the eye we will need to rotate the plaque about its Z axis.
    PlaqueOffsetCentered

    Adjust the Setup window appearance to taste, e.g. disable the meridian plane and set the view to Plaque Center LookAtPlaqueBtn using the view controls in the toolbar controls group.

    PlaqueViewCentered

    16. Tilt the plaque to fit the anterior eye

    In the Plaque Offset window:

    • Rotate the Z axes 13 degrees and offset the plaque -0.5 mm so that the center of the plaque touches the sclera, the suture eyelets touch the sclera and the face of the plaque arcs above the cornea.
    • Disable the plaque axes and reenable the eye axes display.
    PlaqueOffsetTilted

    SetupTilted PlanarTilted

    17. Enter prescription

    In the Prescription window we will set the prescription (Rx) dose, the Rx point, dose calculation modifiers, and the implant and removal dates and times.
    Note: subsequent planning activities are simplified by establishing the Rx at this stage of the planning process, but the Rx can be revised at any time.

    When the EP2025P_AB plaque file was opened, the dose calculation modifiers in the Prescription window's toolbar were automatically set to:
    ModifiersEP

    • 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 plaques such as the EP2025 where virtually all collimation occurs at the slot edges close to the seed rather than at the perimeter of the plaque shell. In this case, disabling the shell collimation modifier accelerates the collimation ray tracing computation.)
    • Slotted collimation enabled
    • Do NOT change these modifier settings until and unless you are VERY familiar with PS.

    For this tutorial, we will begin with a Rx of 85 Gy to the tumor apex to be delivered in 168 hours (1 week) with the implant scheduled for 10 AM on June 23, 2014.

    • Set the Rx units to Gy.
      UnitsButton
    • Set the Rx dose to 85 Gy..
      DoseField
    • In the insertion controls group set the implant date and time to 10AM on June 23, 2014.
      InsertionGroup
    • In the removal controls group click the 1 Week button.
      RemovalGroup
    RxSetDate

    Notes:

    • The insertion and removal calendar buttons open the Calendar dialog where you can set date and time with an expanded user interface.
      CalendarButton
    • The initial state of the 'P1 Central AXis table' is zero because the plaque is currently empty.
    • The background of the 'Rx point' field is red because the Rx has not been satisfied.
    • The background of the 'time' field is green because the implant duration is within the bounds that were set in PS preferences. Implant durations between 4 and 7 days (96 to 168 hours) are typical.

    18. Create a new radionuclide inventory entry
    • From the Plaque window click the Source button to open the radionuclide inventory window.
      SourceButton42x42
    • To create a new entry in the inventory database click the Show only radio button to enable physics model selection.
    • Select a seed physics model from the menu. In this example model IAI-125A (IsoAid) has been selected. This physics model is designed for source strength to be entered in units of mCi as described in the Physics Dose Constants section.
    • Click the New button to create a new inventory entry.
    • The new entry will automatically be selected (highlighted in blue in the scrollview). It will inherit the implant date and time from the current prescription as its calibration, will be named for the current patient and will contain the number of sources in the currently active plaque (plaque #1 was selected as currently the active plaque in step 18 above). The source strength will be initialized to 1.0 (either mCi or U depending upon the physics settings for the model seed selected).
    • To select a different inventory with which to load the plaque, simply click in the list.
    • Click the Edit button to review or change the selected inventory entry parameters.
    NewInventory

    NewInventorySheet

    19. Load sources into the plaque

    Organize your windows so the Plaque window and the Retinal Diagram window are both visible alongside one another.

    • In the Plaque window click the Load button to fill the plaque with 25 sources from the currently selected radionuclide inventory (that we created in the previous step).
      LoadButton42x42
    • Click the Labels button to display the source strength.
      LabelsButton42x42
    EP2025PABLoaded
    DiagramLoaded

    In the Retinal Diagram, the source placeholders change from brown to the color of the inventory sources (e.g. cyan) to indicate that they are occupied.


    20. Calculate source strength

    1. In the Prescription (Rx) window

    • In step 17 we set the prescription (Rx) to deliver 85 Gy to the apex of the tumor in 168 hours.
    • The 25 sources in the plaque are currently all 1.00 mCi (at the time of implant) because that is how we initialized them when we created their inventory in step 18.
    • The state of the 'P1 Central AXis table' reflects the current plaque loading. The dose to the Rx point (tumor apex) of 71.829 Gy is less than the Rx of 85 Gy. The background color is red indicating that the Rx has NOT been fulfilled.
    • Click the Implant Calculator button.
      ImplantCalc41x41
      to open the Implant Calculator window.
    RxApex1mCiSeeds
    Plaque1mCiSeeds

    2. In the Implant Calculator window

    • Click the Calc. Sources button. This will rescale the source strengths in the plaque to deliver the prescription of 85 Gy to the tumor apex in 168 hours.
      ImplantCalcuator1mCiSeeds
    • The Prescription (Rx) and Plaque Loading windows will update to reflect the revised source strengths of 1.18 mCi per source.
    RxApex118Seeds

    The 'P1 Central AXis table' now lists the dose at the Rx point (tumor #1 apex at 4.52 mm) as 85 Gy and the background color has changed from red to green indicating the Rx has been fulfilled.

    Plaque118Seeds

    The sources in the plaque are now 1.18 mCi at the time of implant.


    21. Choose an isodose legend

    In the Isodose window

    • From the Select menu choose the MyFavorite.idos6 legend file.
    • PS6 isodose legend files bundle instructions regarding isodose values, colors, absolute vs normalized plotting, and which isodose lines and surfaces to display.
    • Note: the column of checkboxes simultaneously affects all 2D isodose displays; the Retinal Diagram, the meridian and coronal Planar Dosimetry surfaces, and any 2D dosimetry surfaces being rendered in the Patient Setup window.
    • Note: the column of radio buttons selects one or more 3D isodose surface(s) (e.g. 85 Gy) for 3D rendering in the Patient Setup window.
    IsodoseWndwFileMenuX
    IsodoseMyFavorite

    22. Calculate isodose distributions and the retina dose area histogram

    From the Dosimetry menu:

    • 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.
    Calculate2DMatrices
    CalculateRDAH

    23. Review dosimetry
    AT118RetinaDosimetry
    AT118PlanarDosimetry
    AT118RDAHDocument
    AT118RDAHPreferences

    In the RDAH Document window

    • The X axis of the RDAH is plotted over the range 0..400 Gy. This range was set by clicking the Fixed button in the Histogram axes group of the Histogram document preferences pane.
    • 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 90% 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 need to revise the prescription in order to improve margin coverage.

    24. Revise the prescription for better margin coverage

    In the Prescription (Rx) window

    • From the prescription site popup menu, change the prescription from the Tumor 1 Apex at 4.52 mm to the item labeled Tumor 1 TAX (inner + x.xx mm). TAX is an acronym for Tumor AXis.
      SelectTAX
    • The Tumor Axis sheet will open.
    ChangeRxToTAX7
    • In the Tumor Axis sheet set the Height field to 7 mm from the inner surface of the sclera.
    • Note: the new Rx point will be above the tumor apex and 7 mm from the inner sclera as illustrated to the right.
    NewRxPoint

    25. Recalculate source strength

    1. In the Prescription (Rx) window

    • In step 24 we revised the prescription (Rx) point from the tumor apex to a point 7 mm above the inner sclera along the tumor axis. This places the Rx point in the vitreous humour above the apex.
    • The 25 sources in the plaque are still all 1.18 mCi (at the time of implant).
    • The state of the 'P1 Central AXis table' reflects the current plaque loading. The dose to the new Rx point (TAX+7 mm) of 64 Gy is now less than the Rx of 85 Gy. The background color is red indicating that the new Rx has NOT been fulfilled.
    • Click the Implant Calculator button.
      ImplantCalc41x41
      to open the Implant Calculator window.
    Rx118Seeds
    Plaque118Seeds

    2. In the Implant Calculator window

    • Click the Calc. Sources button. This will rescale the source strengths in the plaque to deliver the prescription of 85 Gy to the new Rx point in 168 hours.
      ImplantCalcuator157Seeds
    • The Prescription (Rx) and Plaque Loading windows will update to reflect the revised source strengths of 1.57 mCi per source.
    Rx157Seeds

    The 'P1 Central AXis table' now lists the dose at the Rx point (Tumor 1 TAX inner+7 mm) as 85 Gy and the background color has changed from red to green indicating the Rx has been fulfilled.

    Plaque157Seeds

    The sources in the plaque are now 1.57 mCi at the time of implant.


    26. Recalculate isodose distributions and the retina dose area histogram for the new Rx

    From the Dosimetry menu:

    • 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.
    Calculate2DMatrices
    CalculateRDAH

    27. Review revised dosimetry
    AT7RetinaDosimetry
    AT7PlanarDosimetry
    AT7RDAHDocument

    In the RDAH Document window

    • 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 7 mm on the tumor axis, coverage of the tumor + 2 mm retinal margin surrounding the base (green line on the histogram) has increased from 90% to almost 98% 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. The dose to the macula and optic disc (orange and red lines in the RDAH) are not noticably affected because the tumor is far from these sites. The maximum retinal dose and dose to the neighboring retina outside the base margin (blue RDAH line) does increase a bit. 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.

    28. Calculate 3D dosimetry

    From the Dosimetry menu:

    • Select Calculate 3D Matrix.
    • Each plaque in PS6 maintains its own 3D dosimetry matrix.
    • In PS6 3D dose calculations are offloaded to a separate thread so that you can continue to perform non-dosimetric activities such as rotating the eye or entering patient ID information during the calculation. The 3D calculation progress can be followed in the status line just below the toolbar of the Patient Setup window. 3D calculations for some of the larger BEBIG Ru plaques can take awhile...
    Calculate3D

    29. Review 3D model

    In the Patient Setup window

    • Click the 3D Dose button to render the selected 3D isodose surface.
      DoseGroup
    • Optionally enable Mer. Dose and Ret. Dose.
    • Click the setup appearance button to open the appearance window window.
      Appearance_34x15
    • Experiment with the 3D model and the appearance controls to create pictures for the setup document.
    • For example, enable the Meridian Plane checkbox.
    AT7Setup2
    AT7SetupAppearance

    30. Review documents
    AT7TreatmentPlanPage1

    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.

    AT7TreatmentPlanPage2

    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 (no fundus image was used in this plan), and an optional picture. The default picture is a radiation safety survey form.

    AT7TreatmentPlanPage3

    Page 3 of the treatment plan 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.

    AT7Loading

    The Loading Diagram document is a "road map" to the plaque. Everything needed to order or manufacture the seeds and assemble the plaque is in this document.

    AT7RetinaPage1

    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.

    AT7RetinaPage2

    The optional 2nd page of the Retinal Diagram document is labeled in degrees CCW (instead of clock hours) in the manner of toric intraocular lens (IOL) axis marking tools such as the Duckworth & Kent Axis Marker model 9-841.
    AxisMarker

    AT7MeridianDocument

    The Isodose document prints the current meridian and coronal dosimetry planes.

    AT7RDAHDocument

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

    AT7SetupDocument

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

    AT7QADocument

    The QA document prints a table containing all of the information needed to manually duplicate Plaque Simulator's simplified (isotropic point source in water) QA check point calculation located at 6 mm on the plaque central axis.


    31. Print documents

    The Print Group button in the toolbar of the Document Preview window prints the group of documents selected by the Document group checkboxes to either paper or to a .pdf file.

    Toolbar
    • To print to a .pdf file click the PDF button in the OSX printing sheet.
    • Select Save as PDF... from the menu.
      PDFMenu
    • To send a multipage .pdf print file by email you may need to create an encrypted version to satisfy HIPAA regulations and you may also need to limit the file size to under 10 MB by compressing the embedded images. Both of these tasks can be accomplished using the OSX Preview application and a custom filter. Contact Eye Physics for details.
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