Plaque Simulator supports 2 dose histogram data structures. Each data structure supports 4 plaques, 2 plots, a table and a legend for the table. By default, each histogram document prints only plot #1. You may optionally enable additional pages to print plot #2, tables and legends via the histogram preferences settings window.

You can click the cursor anywhere on the plot to interactively display the dose and area (or volume) at that location.

RDAH Reference: Astrahan, M.A., The retina dose-area histogram: a metric for quantitatively comparing rival eye plaque treatment options, J Contemp Brachytherapy, 5(1): 23-32, 2013. Download PDF

The RDAH is usually the more useful metric for treatment optimization because the critical regions of the eye that we are interested in sparing (e.g. macula, fovea and optic disc) are primarily located in the thin retinal and choroidal layers which are more rapidly approximated and mapped to the azimuthal equidistant projection (aka retinal diagram) using a 2D surface area calculation over the inner sclera compared to using a volumetric model of those layers and the entire eye.

Note: Dose histograms in printed documents will be plotted in the same manner as the histograms in this window except that the plot will be optimized to print on white paper and layout adjusted to fit to the paper size and orientation.

• Plaque Selects the active plaque for planning calculations and histogram settings context. Note: each histogram data structure maintains independent mode and plot settings for each plaque so you can create some interesting comparisons.
• Histogram # Selects which of the two histograms to plot.
• Mode Histogram #1 defaults to a RDAH calculation whereas histogram #2 defaults to a DVH calculation.
• Line Style Line style with which to plot histograms for the selected plaque.
• Plot # Plot #1 defaults to a cummulative histogram and plot #2 to a differential histogram. By default, only plot #1 is printed.
• Plot Type Selects between cummulative and differential plotting of the histogram data.
• Legend Selects between no legend, a minimalist legend and a full legend that includes dose statistics overlayed on the plot. Note: changes apply only to the currently selected plaque.
• Overlay Enables overlay of histogram calculations to compare up to four plaques. Examples using overlays to compare two plaque candidates are illustrated below.
• Calc. Forces recalculation of the currently displayed histogram. In general, you may find it more convenient to use the Dosimetry Menu to calculate histograms.

• Window Size Click to display the resize sheet for this window.
• Zoom Out Reduces the window content plot scaling by 2X.
• Zoom In Enlarges the window content plot scaling by 2X.
• Home View Forces the plot size to home view (1:1).
• Preferences... Open the PS Preference Settings window.
• Axes... Opens the custom axes parameter sheet.
• 300 Convenience functions for horizontal axis dose range.
• Auto When enabled, automatically rescales fonts and plot appearance for the current window size.
• Font Size Slider Manually rescale font and plot appearance if auto mode is disabled.

Histogram custom axes sheet (click the Axes... button in the footer controls to access)

The examples below illustrate the use of dose histogram overlays to compare the dosimetry of a COMS16 vs an EP1821 plaque for identical 12x12x6 mm tumors in identical left eyes for a Rx of 85 Gy at the tumor apex. The diameter of the concave face of the EP1821 and COMS16 are nearly identical. Examples of cumulative and differential histograms, and various legend options are illustrated.

You can customize your histogram plots to directly compare alternative plaque models and loading patterns by opting to overlay rivals. In the examples below Rx dose (85 Gy) coverage of the tumor base-margin PTV surface (GREEN curves in the RDAH plots) and tumor GTV volume (BROWN curves in the DVH plots) are nearly identical. These histograms also reveal that maximum dose to the inner-scleral surface and optic disc surface (MAGENTA curves) are reduced for the EP1821 (dashed lines) compared to the COMS16 (solid lines).

Cumulative RDAH with minimal legend (histogram #1, plot #1)

Differential RDAH with full legend (histogram #1, plot #2)

Cumulative DVH with minimal legend (histogram #2, plot #1)

Differential DVH with full legend (histogram #2, plot #2)

Cumulative RDAH with full legend (histogram #1, plot #1

Cumulative RDAH with no legend (histogram #1, plot #1

You can create mixed DVH, RDAH, cumulative and differential plots, customize the plotted range, line styles and so on in this window or via advanced settings found in the histogram document preferences pane.

Most of the time, you will find it easier to use the histogram parameter convenience functions such as the controls located in the window toolbar (e.g. the Legend segmented control) or one of the Axes... butons along the bottom of the window or by double-clicking the x or y axes lines. This will open the axes parameters sheet primed for the most likely subsequent actions.

For finer, but more complex customization of histogram plotting and appearance parameters you can use the Dosimetry Menu or alternatively access all histogram document preferences by double clicking anywhere else in the histogram window or by clicking the Preferences button at the bottom of the window. Changes in window settings are not automatically propagated to preferences, but there is a button in the preferences pane to do so. Changes to preferences, on the other hand, are immediately propagated to histogram window settings. Histogram window settings are saved in the .iplan6 patient file.