DViewer

A lightweight, cross-platform DICOM viewer built with .NET MAUI.

Focus areas:

• fast metadata inspection
• side-by-side comparison
• basic metadata editing
• simple conversions (e.g., extracting encapsulated video)
• highlighting of non-conformant values

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Features

• Cross-platform UI (Windows, macOS/MacCatalyst, Android, iOS)
• Two-pane workflow: load a DICOM on the left/right and compare tag-by-tag
• Fast metadata browser with search, tag filter, sorting, and a “differences only” toggle
• Inline editing of left/right values with instant highlighting
• Validation cues for obviously invalid or mismatched values
• Multi-frame support: frame slider + simple timer-based playback
• Encapsulated video (H.264/MPEG-4) extraction to a temp file and inline playback
• Pragmatic preview: renders a first frame when it is not a video
• File association friendly (open from OS into a side)

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Requirements

• .NET SDK 8.0 (or the version used in the solution)

• .NET MAUI workloads for your target platforms

• NuGet packages:

  • FellowOakDicom
  • CommunityToolkit.Maui
  • CommunityToolkit.Maui.MediaElement
  • SixLabors.ImageSharp

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Setup

Enable the Community Toolkit (including MediaElement) in MauiProgram.cs

using CommunityToolkit.Maui;

public static class MauiProgram
{
    public static MauiApp CreateMauiApp()
    {
        var builder = MauiApp.CreateBuilder();

        builder
            .UseMauiApp<App>()
            .UseMauiCommunityToolkit()
            .UseMauiCommunityToolkitMediaElement()
            .ConfigureFonts(fonts =>
            {
                fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");
                fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");
            });

        return builder.Build();
    }
}

XAML namespace for MediaElement

xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"

(Optional) Fellow Oak DICOM setup

If you use native codecs/transcoding, initialize once at startup:

using FellowOakDicom;
using FellowOakDicom.Imaging;

new DicomSetupBuilder()
    .RegisterServices(s => s.AddFellowOakDicom())
    .SkipValidation()
    .Build();

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Build and Run

# Restore and build
dotnet restore
dotnet build

# Example: run on Windows
dotnet run -f net8.0-windows10.0.19041.0

Use Visual Studio to select and run Android, iOS, or MacCatalyst targets.

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How It Works

• Loader (DicomLoader)

  • Opens DICOM via Fellow Oak DICOM
  • Builds safe metadata (skips large/binary tags)
  • Detects encapsulated video; if present, extracts the elementary stream (H.264/MPEG-4) to the app cache and exposes a path
  • For images, renders a first frame and exposes a delegate to render arbitrary frames for multi-frame studies

• Per-file ViewModel (DicomFileViewModel)

  • Holds FileName, Image (preview), Metadata (read-only), Rows, and RowMap
  • Video case: VideoPath set (e.g., .mp4), FrameCount = 0, GetFrameImageSource = null
  • Multi-frame case: VideoPath = null, FrameCount = NumberOfFrames, GetFrameImageSource = idx => RenderFrameAsImageSource(ds, idx)

• Main ViewModel (MainViewModel)

  • Holds Left and Right files, combined comparison table, filtering/sorting state
  • Multi-frame playback via IDispatcherTimer (videos play in MediaElement)
  • Exposes LeftHasVideo, Left/RightVideoSource, Left/RightHasMultiFrame, FrameCount, FrameIndex, etc.

• UI (XAML)

  • Each side shows either an Image (no video) or a MediaElement (video)
  • Compact overlay shows key patient/study fields
  • Bottom half shows the combined metadata grid with inline editing

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Usage

1. Open files Click the L (left) or R (right) button to pick a DICOM file for that side.

2. Preview

   • Video: MediaElement with playback controls (via CommunityToolkit.Maui.MediaElement)
   • Multi-frame: frame slider and play/pause
   • Single-frame: static preview of frame 0

3. Browse and filter metadata

   • Free-text filter (tag, name, or value)
   • Tag-Filter list to focus on a single tag
   • Toggles: “Only differences” and “Only invalid”

4. Edit values

   • Edit left/right values inline; highlighting updates immediately

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Conversions

• Encapsulated video extraction If the DICOM contains H.264/MPEG-4, the elementary stream is written to the app cache (e.g., .mp4) and bound to the player.

• Future ideas Transfer syntax normalization, anonymization, bulk export.

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Validation and Non-Conformance

• Basic heuristics flag suspicious or invalid values and differences between sides.
• Extend validators as needed (e.g., stricter VR/VM checks, modality-specific rules).

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Troubleshooting

• Video does not play

  • Ensure CommunityToolkit.Maui.MediaElement is installed and enabled in MauiProgram.cs.
  • Confirm platform codec support (H.264 recommended).
  • Check that LeftVideoSource/RightVideoSource points to a valid file (app cache).

• No preview or wrong colors

  • Some uncommon photometric interpretations or high bit depths may need extra handling.

• Large files slow UI

  • Large/binary tags are skipped; consider virtualization for extremely large tag lists.

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Roadmap

• Optional write-back of edited metadata
• Expanded validators and conformance profiles
• Bulk conversion/export tools
• Keyboard shortcuts and advanced tag editors

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License

Apache-2.0