Using the DICOM Viewer

Mouse Controls

By default, the viewer opens with the Window/Level tool active on left-click.

• Left-click + drag: Active tool (Window/Level by default)
• Middle-click + drag: Pan
• Mouse wheel: Scroll through images

Switch the active tool using the toolbar buttons or keyboard shortcuts below.

Toolbar

The toolbar across the top of the viewer provides quick access to:

• Window/Level — Adjust brightness and contrast by dragging

• W/L Presets — Quick presets for CT/MR scans (dropdown, only shown for CT and MR images). On CT series, keys 5–0 apply each preset directly:

  • 5 Soft Tissue (W:400 / L:40)
  • 6 Lung (W:1500 / L:-500)
  • 7 Bone (W:2000 / L:500)
  • 8 Brain (W:80 / L:40)
  • 9 Subdural (W:200 / L:90)
  • 0 Stroke (W:32 / L:32)

  Preset keys are ignored while typing in a report, notebook, or other text field — they only fire when the DICOM viewer has focus.

• Zoom/Pan — Left-click to zoom, middle-click to pan

• Magnify — Magnifying glass over the cursor area

• Rotate — Rotate the image

• Invert — Invert grayscale

• Scroll — Scroll through the image stack (multi-image series only)

• Fullscreen — Expand the viewer to fill the screen

Measurement Tools

A measurement dropdown in the toolbar provides:

• Length — Measure distance between two points
• Angle — Measure angles
• Rectangle ROI — Draw a rectangular region of interest
• Elliptical ROI — Draw an elliptical region of interest
• Bidirectional — Two perpendicular length measurements
• Arrow Annotation — Drop an arrow pointer on a finding
• Freehand ROI — Trace an irregular region by hand

Label Spine

Under Label Spine in the same dropdown, pick the region you want to mark and each click on the image drops the next vertebral level in sequence:

• Cervical — C1 → C7, T1
• Thoracic — T1 → T12, L1
• Lumbar — S1, L5, L4 → T12 (counts up from S1)

Click on an existing label to cycle it to a different level. Labels clear alongside other measurements via the trash icon or the Reset button.

To delete a measurement, select it and press Delete or Backspace. To clear all measurements, use the trash icon in the toolbar.

Scroll Speed

You can adjust how fast the viewer scrolls through images using the Scroll Sensitivity control in the image navigation bar at the bottom of the viewer.

• On desktop, use the slider to set a speed between 0.05x (very slow) and 1.75x (very fast). The current value is shown next to the slider.
• On a phone or tablet browser, tap the scroll speed button to open a dropdown with preset speed options.
• In the mobile app, this is the Sensitivity button in the row beneath the image. It sets both how far a drag scrubs the stack and how fast window and level move.
• Keyboard shortcut: Press Ctrl+Plus (or Cmd+Plus on Mac) to increase scroll speed, and Ctrl+Minus (or Cmd+Minus) to decrease it, in 0.05x increments.

Your scroll speed preference is saved automatically and persists across sessions.

Series Navigation

When a case has multiple image series, tabs appear at the top of the viewer. Click a tab to switch between series. DICOM series tabs appear first, followed by any regular image galleries.

Series load on demand when you click the tab, so there's no delay from loading everything upfront.

Fullscreen Mode

Click the fullscreen button in the toolbar or press Shift+F to enter fullscreen. Press Shift+F or Esc to exit.

In tabbed viewers, fullscreen expands the entire viewer including all tabs, so you can still switch series while in fullscreen.

Keyboard Shortcuts

Tool Selection

W/L Presets (CT)

Image Navigation

Measurements

Image Adjustments

Annotations

Browser Requirements

The DICOM viewer requires a modern browser with WebGL support. For best results:

• Chrome 110+ (recommended)
• Firefox 115+
• Safari 17+
• Edge 110+

Enable hardware acceleration in your browser settings for the best performance. A desktop or laptop computer is recommended for large CT or MRI studies. The viewer also works in a phone or tablet browser with touch controls, though performance may be limited on older hardware.

These requirements apply to the website. The CaseStacks mobile app has its own viewer with touch controls built in, described below.

In the Mobile App

The app's viewer runs inside the Images tab of a case. It is touch-driven rather than mouse-driven, so the controls differ from the website.

Gestures. One finger does whatever the selected mode button says. The modes are Scroll for moving through the stack, W/L for window and level, Zoom, and Measure. Pinch to zoom and drag with two fingers to pan at any time, in any mode. Reset restores the original view.

Buttons on the image. Depending on the case you may see Annotations, which toggles markers on and off and opens a jump list if you hold it, plus Feedback, How it works, Sensitivity, and Fullscreen. A help panel opens by itself the first time you use the viewer, and How it works brings it back later.

Measurement. Tap Measure, then hold that button for the full set of tools: Length, Angle, Bidirectional, Ellipse, and Rectangle. Clear removes what you've drawn.

Window presets. On CT cases, a preset menu appears while W/L is selected, with Brain, Subdural, Stroke, Soft Tissue, Lung, and Bone.

Multiple series. When a case has more than one series, chips appear at the top of the image. Tap one to switch.

Invert is available on tablets.

Turning a phone sideways moves the app's buttons into a column down the left edge and the viewer's own tools to the right, leaving the image the space between them. Imaging is streamed, so the viewer always needs a connection.