Using the DICOM Viewer

Mouse Controls

By default, the viewer opens with the Window/Level tool active on left-click. To open in Scroll instead, change Default tool in the viewer's settings (the gear icon, when signed in).

• Left-click + drag: Active tool (Window/Level by default)
• Middle-click + drag: Pan (while the Zoom/Pan tool is selected)
• 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 scans (dropdown, shown on multi-image CT series). 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 you type in a report, notebook, or other text field.

• 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 Measurements dropdown in the top-left corner of the image 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 red X next to the Measurements dropdown or the Reset button.

To delete a length, angle, ROI or bidirectional measurement, hover over it and press Delete or Backspace. Arrows, freehand shapes and spine labels are removed with the clear-all control. To clear all measurements, click the red X next to the Measurements dropdown, or use Reset.

Scroll Speed

You can adjust how fast the viewer scrolls through images using the Sensitivity control in the image navigation bar at the bottom of the viewer. Choose Scroll or W/L to set scroll speed or window/level speed.

• On desktop, use the slider. Scroll speed runs from 0.05x (very slow) to 1.75x (very fast), and the current value is shown next to the slider.
• On a phone or tablet browser, tap the Scroll or W/L button to open a dropdown with preset speeds.
• In the mobile app, use the Settings button (a sliders icon) in the row of buttons by the image. It sets how far a drag scrubs the stack and how fast window and level move, and can hide the slice scrubber under the image.
• 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. Keep your mouse over the image; elsewhere these keys zoom the page.

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. A Key Images tab (if the case has one) comes first, then DICOM series, then any other 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

Press Shift+?, or click the keyboard button below the image, to see every shortcut.

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. Two fingers always pan, never window and level, and there is no double-tap gesture. Reset restores the original view.

Buttons by 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. Then come Notes, Feedback, How it works, Settings, and Fullscreen. On a phone most show as icons only. A help panel opens by itself the first time you use the viewer, and How it works brings it back later.

Settings sets how far a drag scrubs the stack and how fast window and level move. Its Slice scrubber switch shows or hides the slider under the image, which jumps straight to a slice.

Notes lists your notes for this case and starts a new one already linked to it. See Notes & Notebook.

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 image stacks, a Presets menu sits with the mode buttons in every mode except Measure, 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. A case with a single series shows no chips.

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.