Advanced DICOM Viewer Documentation

Introduction

This advanced DICOM viewer is a comprehensive web-based medical imaging platform designed for radiologists, medical professionals, researchers, and healthcare students. Built on the powerful Cornerstone.js framework, this tool enables sophisticated visualization and analysis of Digital Imaging and Communications in Medicine files directly within your browser, without requiring any software downloads or plugin installations.

The application runs entirely client-side, meaning all image processing and manipulation occurs on your local device. This architecture ensures complete data privacy and security, as sensitive patient information never leaves your computer or gets transmitted to external servers. Whether you are reviewing CT scans, MRI sequences, X-rays, ultrasound studies, or other modality images, this viewer provides professional-grade tools for medical image analysis.

Key advantages include zero-installation deployment, cross-platform compatibility across Windows, macOS, Linux, and mobile devices, instant access through modern web browsers, and robust support for both single-frame and multi-frame DICOM datasets. The viewer handles cine loops, image stacks, and volumetric data with smooth navigation and responsive controls optimized for touchscreen and mouse interactions.

Core Features

The viewer integrates a comprehensive suite of imaging tools and functionalities designed to support detailed radiological examination and comparative analysis workflows. Each feature has been optimized for both desktop and mobile environments.

Complete Feature List

• Native DICOM file parsing with metadata extraction and display
• Interactive pan and zoom with mouse-based navigation
• Dynamic window level adjustments for different tissue types
• Color inversion for enhanced visualization of specific structures
• Linear distance measurements with calibrated metric units
• Area calculations using region of interest tools
• Annotation persistence with undo and redo functionality
• Multi-frame cine loop playback and navigation
• Dual viewport compare mode with independent file loading
• Selective viewport synchronization via checkbox controls
• Real-time viewport statistics including zoom scale and position
• Patient demographics and study metadata panel
• Responsive mobile-first design with touch gesture support
• Floating action button toolbar for mobile devices
• Full-screen viewing mode for distraction-free analysis
• Hardware-accelerated rendering for smooth performance
• Multi-threaded DICOM decoding using web workers
• Automatic caching for faster frame navigation

Getting Started

System Requirements

The DICOM viewer works on any device with a modern web browser supporting HTML5, WebGL, and JavaScript ES6. Recommended browsers include Google Chrome version 90 or higher, Mozilla Firefox 88 or newer, Safari 14 and above, or Microsoft Edge 90 and later. Mobile users should use iOS Safari 14 or Android Chrome 90 for optimal touch interaction support.

For processing large imaging datasets or high-resolution scans, a minimum of 4GB RAM is recommended, though 8GB or more provides better performance. The viewer utilizes hardware acceleration when available, so devices with dedicated graphics capabilities will experience smoother rendering of volumetric data and rapid frame navigation.

Loading Your First Image

To begin analyzing medical images, click the file upload area or drag and drop a DICOM file directly onto the viewport. The viewer accepts standard DCM file extensions as well as files without extensions that contain valid DICOM headers. Once selected, the image undergoes automatic parsing to extract both pixel data and embedded metadata.

After successful loading, the viewport displays your image with default windowing settings appropriate for the detected modality. The status bar at the bottom shows current zoom level, window width and center values, mouse position coordinates, and pixel intensity values under the cursor. For multi-frame sequences, a frame slider appears below the image, showing the current frame number and total frame count.

Understanding the Interface

The application interface consists of four primary areas: the viewport canvas where images display, the top toolbar containing tool buttons and controls, the bottom status bar showing real-time image statistics, and the optional metadata panel accessible via the info button. On mobile devices, the toolbar collapses into a floating action button to maximize screen space for image viewing.

Each viewport has a checkbox in its top-left corner used for synchronization control in compare mode. When checked, that viewport participates in synchronized operations like simultaneous zooming, panning, and frame navigation. Unchecked viewports operate independently, allowing mixed interaction patterns within the same session.

Mouse Controls

The viewer implements intuitive mouse-based interaction patterns familiar to radiology professionals. Different mouse buttons and scroll actions perform specific operations, enabling efficient hands-on navigation without constantly clicking toolbar buttons. These controls work system-wide across all viewports when synchronization is disabled.

Touchscreen Gestures

Mobile and tablet users can navigate using standard touch gestures. Single-finger drag performs panning operations, while pinch-to-zoom gestures control magnification. Two-finger vertical swipes navigate through multi-frame datasets. Touch and hold activates tool-specific functions when annotation tools are selected, such as placing measurement endpoints or text markers.

Toolbar Functions

The horizontal toolbar provides quick access to all viewer functions through clearly labeled buttons. Each tool activates with a single click and remains active until another tool is selected or pan mode is restored. The toolbar adapts to screen size, collapsing into a floating action button menu on mobile devices for space efficiency.

Navigation Tools

• Pan: Activates click-and-drag repositioning of the image within the viewport. Default tool on startup.
• Zoom In: Increases magnification by 20% increments, maintaining center point focus.
• Zoom Out: Decreases magnification by 20% increments with minimum scale limit to prevent over-reduction.
• Reset: Restores default viewport settings including original zoom level, center position, and standard windowing values.

Window Level Tools

• WW/WC: Activates interactive windowing mode where vertical mouse drag adjusts window center and horizontal drag modifies window width. This tool is essential for examining different tissue densities within the same scan.
• Invert: Toggles color inversion, displaying dark regions as bright and vice versa. Useful for certain imaging modalities and user preferences.

Annotation and Measurement Tools

These tools overlay calibrated graphics and measurements directly onto the displayed image. All annotations remain editable after placement and persist throughout the session unless explicitly cleared. Measurements utilize pixel spacing metadata from the DICOM file for accurate metric calculations.

• Length: Measures linear distances between two points. Click to place the start point, move the cursor to the endpoint, and click again. The measurement displays in millimeters when pixel spacing is available.
• Arrow: Creates directional arrows for indicating anatomical structures or findings. Click to set the arrow origin, drag to the target, and click to complete.
• Rectangle: Draws rectangular regions of interest with area calculations. Click and drag to define opposite corners. The tool displays length, width, and total area statistics.
• Circle: Creates elliptical regions of interest. Click and drag from center to edge to define the ellipse. Shows major and minor axis measurements plus total area.
• Text: Places text annotations anywhere on the image. Click to position the text marker, then type your annotation in the dialog box that appears.
• Clear Annotations: Removes all annotations and measurements from the currently active viewport. This action cannot be undone, so use carefully.

History Controls

• Undo: Reverts the last annotation or measurement action. Supports multiple levels of undo for incremental backtracking.
• Redo: Restores previously undone actions, allowing forward navigation through the history stack.

Data Management

• Info: Opens the metadata panel displaying patient demographics, study information, acquisition parameters, and technical image characteristics extracted from DICOM tags.
• Export PNG: Saves the current viewport view as a high-quality PNG image file including all visible annotations and current windowing settings. Useful for reports and presentations.
• Export JSON: Exports all annotations and measurements as a structured JSON file. This enables sharing findings with colleagues or importing annotations in future sessions.
• Import JSON: Loads previously exported annotation files, overlaying saved measurements and markings onto the current image.

Annotations and Measurements

The annotation system provides radiologists and clinicians with professional measurement and marking capabilities for documenting findings, preparing teaching materials, and collaborating with colleagues. All annotations overlay non-destructively on the image without modifying the underlying DICOM data.

Making Accurate Measurements

To create precise linear measurements, select the Length tool from the toolbar, then click once at the measurement starting point. Move your cursor to the endpoint while observing the dynamic line preview. Click again to finalize the measurement. The annotation displays the distance in millimeters when calibrated pixel spacing metadata is available in the DICOM file. For uncalibrated images, measurements appear in pixels.

Region of interest tools including Rectangle and Circle calculate both perimeter and area measurements. These are particularly useful for quantifying lesion sizes, organ dimensions, or other anatomical structures requiring area assessment. After placing an ROI, hover over it to see detailed statistics including mean pixel value within the region, standard deviation, minimum and maximum intensity values.

Annotation Best Practices

• Place measurements at maximum lesion diameters for standardized reporting and follow-up comparison
• Use arrows to highlight subtle findings that may be difficult to identify without guidance
• Add text annotations to label anatomical structures in teaching files or complex cases
• Take advantage of undo functionality to refine measurement placement for maximum accuracy
• Export annotations as JSON before closing the viewer to preserve your work for later review
• Verify pixel spacing calibration in the metadata panel before relying on metric measurements

Editing and Removing Annotations

After placement, annotations remain interactive and editable. Click directly on any measurement line, ROI, or arrow to select it. Small handles appear at control points, allowing you to drag and reposition endpoints or adjust dimensions. To delete a single annotation, select it and press the Delete or Backspace key. The Clear Annotations button removes all markings from the active viewport simultaneously.

Compare Mode and Synchronization

Compare mode transforms the single viewport layout into a dual viewport configuration, enabling side-by-side comparison of different images, temporal studies, or multiple sequences from the same examination. This feature is invaluable for assessing treatment response, identifying progression or regression of findings, and comparing different imaging modalities of the same anatomical region.

Activating Compare Mode

Click the Compare button in the toolbar to split the display into two equal viewports. Each viewport maintains independent file loading capabilities, allowing you to load different DICOM files into each panel. The first viewport retains any currently loaded image, while the second viewport displays a file upload placeholder. Use the dedicated file input controls beneath each viewport to load comparison studies.

Understanding Viewport Synchronization

Each viewport features a synchronization checkbox in its top-left corner. This checkbox controls whether that viewport participates in synchronized operations. When both checkboxes are enabled, the viewports link together, causing zoom, pan, windowing, and frame navigation actions to occur simultaneously in both panels. This synchronized viewing maintains consistent perspective and presentation across comparison images.

Synchronization applies to all control methods including mouse interactions, toolbar buttons, and slider adjustments. For example, clicking the Zoom In button when both viewports are synchronized increases magnification equally in both panels. Similarly, dragging the frame slider navigates both image stacks in parallel, maintaining temporal alignment for dynamic studies.

Selective Synchronization

The checkbox system provides flexible control over synchronization behavior. Unchecking one viewport disables synchronization for that panel, allowing independent manipulation while the other viewport remains responsive to controls. This selective approach is useful when comparing images with different anatomical coverage or when one study requires different windowing settings than the other.

With only one checkbox enabled, that viewport receives all control inputs from mouse interactions, toolbar buttons, and sliders. The unchecked viewport remains static unless directly interacted with. To apply controls to an unchecked viewport, hover your mouse over it to make it the active viewport, then perform your desired operations.

Synchronization Scenarios

• Both checked: Perfect for temporal comparison where maintaining identical zoom, pan, and windowing across studies is essential. Mouse wheel frame navigation scrolls both image stacks simultaneously.
• One checked: Allows focused manipulation of a single viewport while keeping the other as a static reference image. Ideal when one study needs extensive windowing adjustments.
• Both unchecked: Provides completely independent viewport behavior. Each panel responds only to direct mouse interaction within its boundaries. Toolbar buttons and sliders affect only the currently active viewport.
• Mixed workflow: Toggle checkboxes dynamically during analysis. Enable synchronization to align images, then disable it to make independent annotations or measurements.

Compare Mode Applications

Temporal comparison studies benefit greatly from synchronized navigation. When reviewing pre-treatment and post-treatment scans, synchronized windowing ensures consistent contrast presentation, making subtle changes more apparent. Frame-by-frame comparison of multi-phase CT or MRI sequences reveals enhancement patterns and perfusion differences.

Cross-modality comparison allows correlation between different imaging techniques. Display a CT scan alongside an MRI of the same region to leverage the complementary information each modality provides. Use independent windowing for each viewport to optimize contrast for the specific modality while maintaining synchronized spatial navigation.

Window Level Adjustments

Window level adjustment, also called windowing or contrast adjustment, is the most critical tool for medical image interpretation. Medical images contain a wide range of pixel intensity values representing different tissue densities, but human vision can only distinguish a limited number of gray shades. Windowing maps a selected range of values to the full displayable grayscale spectrum, emphasizing specific tissues while de-emphasizing others.

Window Width and Window Center

Two parameters control windowing: window width and window center. Window width determines the range of pixel values displayed across the grayscale spectrum. A narrow window width shows high contrast with fewer distinguishable tissue types, while a wide window width displays more tissue types but with reduced contrast between them.

Window center sets the midpoint of the displayed value range. Adjusting the center moves the windowing range up or down through the available pixel values. Pixels below the window appear black, pixels above appear white, and pixels within the window distribute across the grayscale range proportionally.

Interactive Windowing Methods

The viewer provides three methods for adjusting windowing. The most intuitive approach uses the WW/WC tool activated from the toolbar. With this tool active, click and drag on the image: horizontal movement adjusts window width (drag right to widen, left to narrow), while vertical movement adjusts window center (drag up to increase, down to decrease).

Alternatively, use the dedicated window width and window center sliders located below the viewport. These sliders provide precise numeric control with real-time value display. The sliders prove especially useful when targeting specific windowing values from radiology protocols or when fine-tuning windowing incrementally.

Middle mouse button dragging provides a third windowing method familiar to users of clinical PACS workstations. Hold the middle mouse button and drag horizontally to adjust width, vertically to adjust center. This method allows windowing without switching tools, maintaining uninterrupted workflow.

Clinical Windowing Applications

Different anatomical structures and tissue types require specific windowing settings for optimal visualization. Bone windows use a wide window width centered at high values to show bone detail while rendering soft tissues as dark gray. Soft tissue windows employ moderate window widths at middle values to differentiate between muscle, fat, and organs. Lung windows utilize very wide windows at low center values to visualize air-filled spaces and subtle parenchymal changes.

When examining CT scans, systematically review the study using multiple window settings. Start with a soft tissue window to assess organs and muscles, then switch to a bone window to evaluate skeletal structures, and finally use a lung window for thoracic studies. This comprehensive windowing approach ensures no findings are missed due to inappropriate contrast settings.

Windowing in Compare Mode

In compare mode with synchronization enabled, windowing adjustments apply simultaneously to both viewports. This synchronized windowing is essential for temporal studies, ensuring equivalent contrast presentation across pre-treatment and post-treatment scans. Differences in lesion appearance then reflect true biological changes rather than windowing artifacts.

For cross-modality comparisons, disable synchronization to apply modality-specific windowing to each viewport independently. CT scans require different windowing than MRI sequences, and independent control allows optimization of each modality while maintaining synchronized spatial navigation.

Multi-frame Navigation

Many DICOM files contain multiple frames or slices within a single file. These multi-frame datasets include cine loops from fluoroscopy or echocardiography, volumetric CT or MRI acquisitions, and dynamic contrast-enhanced sequences. The viewer provides smooth navigation through these frame sequences using multiple control methods optimized for different navigation patterns.

Frame Slider Control

When a multi-frame DICOM file loads, a frame slider automatically appears below the viewport. This slider displays the current frame number and total frame count in format “Frame: 15 / 120”. Drag the slider thumb left or right to navigate backward or forward through the sequence. The slider provides visual feedback of your position within the dataset and enables rapid jumping to any frame.

In compare mode with synchronization enabled, the frame slider controls both viewports simultaneously. This synchronized frame navigation is ideal for comparing dynamic sequences frame-by-frame, such as pre-contrast and post-contrast phases of an MRI examination. Both image stacks advance together, maintaining temporal alignment throughout the review.

Mouse Wheel Scrolling

The mouse wheel provides the most efficient method for sequential frame navigation. Simply hover your mouse over a viewport and scroll the wheel up to advance forward through frames or scroll down to move backward. This hands-on scrolling creates a fluid browsing experience, allowing rapid scanning through large image stacks to identify key frames or subtle changes.

Mouse wheel scrolling respects synchronization settings. With both viewports synchronized, scrolling navigates both image stacks together. With synchronization disabled, scrolling affects only the viewport under your mouse cursor, allowing independent navigation of each stack.

Frame Navigation Strategies

• Use the frame slider for rapid jumping to specific frames when the approximate frame number is known
• Employ mouse wheel scrolling for sequential review and identification of dynamic changes across frames
• Combine both methods: use the slider to jump to a region of interest, then fine-tune position with mouse wheel
• In synchronized compare mode, advance both sequences together to identify temporal changes between studies
• Disable synchronization to compare the same frame number across different acquisition phases

Performance Optimization

The viewer implements intelligent caching to ensure smooth frame navigation even with large datasets. Frames are decoded and cached as you navigate, with subsequent visits to previously viewed frames loading instantly from cache. The caching system prioritizes frames near your current position, pre-loading adjacent frames for seamless sequential scrolling.

For optimal performance with very large multi-frame files, allow a moment after initial load for the caching system to decode nearby frames. Rapid scrolling immediately after load may cause brief pauses as frames decode on-demand. After the initial pass through a sequence, subsequent navigation will be significantly faster due to cached frame data.

Export and Import

The viewer provides comprehensive data export capabilities for documentation, collaboration, presentation, and archival purposes. Export functions preserve your work including windowing settings, zoom level, annotations, and measurements, enabling sharing of interpreted studies with colleagues or incorporation into teaching materials and reports.

PNG Screenshot Export

Click the Export PNG button to save the current viewport view as a high-resolution PNG image file. The exported image captures everything visible in the viewport including the DICOM pixel data with current windowing applied, all annotations and measurements with labels and values, zoom level and positioning, and color inversion if enabled.

PNG export is ideal for creating figures for presentations, incorporating findings into radiology reports, documenting baseline measurements for follow-up comparison, preparing teaching files for educational conferences, and sharing anonymized findings via email or messaging platforms. The exported PNG files are standard image format compatible with any image viewer or document editor.

JSON Annotation Export

The Export JSON function saves all annotations and measurements from the current viewport as a structured JSON data file. This file contains coordinates, measurement values, annotation text, and geometric parameters for every marking placed on the image. JSON export enables preserving detailed measurement data separately from the image, sharing quantitative findings with colleagues who can import your annotations, archiving measurement data for research studies or clinical trials, and maintaining a permanent record of documented findings independent of screenshot images.

The JSON file format is human-readable and can be opened in any text editor. Each annotation includes metadata specifying its type, coordinates, calibrated measurements, and display properties. This structured format facilitates programmatic analysis of measurement data or integration with external analysis pipelines.

JSON Annotation Import

Click the Import JSON button to load previously exported annotation files. After selecting a JSON file, the viewer reconstructs all annotations and overlays them on the currently displayed image. Import functionality enables reviewing previously marked studies, sharing findings with colleagues who can load your annotations on their own viewer, comparing current and prior measurements by importing historical annotation files, and collaborative workflow where multiple reviewers contribute annotations to the same study.

For successful import, the JSON file must have been exported from the same or a compatible DICOM viewer. The annotations overlay at their original coordinates, so importing annotations onto a different image than they were created on may result in misaligned markings. Always verify that imported annotations align correctly with the intended anatomical structures.

Export Workflow Recommendations

• Export PNG screenshots after optimizing windowing and positioning for the clearest depiction of findings
• Use JSON export to back up annotations before closing the viewer or loading a different image
• Create standardized file naming conventions for exported files to maintain organized archives
• Export multiple PNG views with different windowing settings to show the same finding in various contrasts
• Combine PNG and JSON export for comprehensive documentation of complex cases
• Store exported files in secure locations maintaining patient confidentiality compliance

Image Interpretation Tips

While the DICOM viewer provides powerful visualization tools, effective medical image interpretation requires systematic approach, anatomical knowledge, and clinical correlation. These guidelines help maximize the diagnostic value of the viewing tools available.

Systematic Review Protocol

Develop a consistent viewing protocol for each examination type. Begin with default windowing to gain an overall impression of the study. Then systematically review the entire dataset using appropriate window settings for different tissues. For CT scans, this typically means reviewing in soft tissue windows, bone windows, and lung windows when applicable. For multi-frame sequences, scroll through the entire stack at least once before focusing on specific findings.

Avoid satisfaction of search errors by continuing systematic review even after identifying an obvious abnormality. Multiple pathologies often coexist, and premature termination of review leads to missed findings. Use windowing extensively, as subtle lesions may only be visible with specific contrast settings.

Leveraging Comparison Tools

When prior studies are available, load them in compare mode for direct side-by-side evaluation. Enable synchronization to maintain identical viewing parameters, making subtle interval changes more apparent. Pay particular attention to measurements of lesions or anatomical structures, comparing current measurements to prior values to assess progression, stability, or regression.

For dynamic studies like contrast-enhanced CT or MRI, use synchronized frame navigation to compare enhancement patterns across different phases. Load the pre-contrast series in one viewport and the post-contrast series in the other, then scroll simultaneously through both stacks to assess enhancement timing and degree.

Measurement Accuracy Considerations

Verify pixel spacing calibration in the DICOM metadata before relying on measurement values for clinical decision-making. Check the metadata panel to confirm that pixel spacing values are present and reasonable for the imaging modality. Uncalibrated images display measurements in pixels rather than millimeters, which are not clinically useful.

For maximum accuracy, measure lesions at their largest diameter perpendicular to the long axis. Place measurement endpoints at the outer edges of lesions, including any irregular margins or surrounding edema if clinically relevant. Take multiple measurements from different angles and use the largest value for standardized reporting protocols like RECIST criteria.

Optimizing Image Display

Use zoom functionality to examine areas of interest at higher magnification while maintaining awareness of surrounding anatomy. Over-zooming can lead to loss of context, while under-zooming may obscure subtle findings. A magnification level where individual pixels become visible is usually optimal for detailed lesion characterization.

Experiment with color inversion for certain findings. Some structures or artifacts become more conspicuous with inverted display. Calcifications, air-fluid levels, and certain enhancement patterns may be easier to identify with negative grayscale presentation.

Clinical Correlation

Always interpret images in the context of clinical history, physical examination findings, and laboratory results. Imaging findings gain significance when correlated with patient symptoms and other clinical data. Use text annotations to document clinical correlation points directly on relevant images for teaching or case discussion purposes.

Advanced Usage

Beyond basic viewing and measurement capabilities, the DICOM viewer supports advanced workflows for power users, researchers, and educators. These techniques leverage the full feature set for specialized applications.

Teaching File Creation

The viewer excels at preparing annotated teaching files for educational conferences and training programs. Load exemplary cases and use the complete annotation toolkit to highlight pathognomonic features. Add text labels identifying anatomical structures or describing pathological findings. Use arrows to draw attention to subtle abnormalities that trainees might overlook. Export the annotated images as PNG files for inclusion in presentations or online teaching modules.

Create a series of images demonstrating the same pathology with different windowing settings. This multi-window approach teaches the importance of systematic windowing and shows how different tissues require different contrast settings for optimal visualization. Export both the annotations as JSON and screenshots as PNG to create comprehensive teaching packages that others can import and review.

Research Applications

Researchers conducting quantitative imaging studies benefit from the calibrated measurement tools and annotation export capabilities. Perform standardized measurements on study subjects using the length and ROI tools. Export measurement data as JSON files for batch processing and statistical analysis. The structured JSON format facilitates automated extraction of measurement values using simple scripts.

For multi-reader studies, multiple observers can independently annotate the same images and export their annotations as separate JSON files. These can then be compared programmatically to assess inter-observer variability and measurement reproducibility. The viewer’s undo/redo functionality allows careful refinement of measurements for maximum precision.

Workflow Optimization

Frequent users should master keyboard shortcuts and mouse-based navigation to minimize toolbar interaction. Learn the mouse button mappings for pan, zoom, and windowing to navigate efficiently without tool switching. Use mouse wheel scrolling extensively for frame navigation rather than repeatedly clicking the slider.

In compare mode, develop the habit of checking synchronization checkboxes before beginning review to ensure the desired linkage behavior. Toggle synchronization dynamically during review based on whether synchronized or independent control is needed for the current task. This flexibility allows seamless transitions between different viewing strategies.

Mobile Usage Strategies

Mobile and tablet users should take advantage of the floating action button toolbar for efficient tool access. The toolbar automatically collapses on smaller screens to maximize image viewing space. Tap the floating button to reveal tool options, select your desired tool, then tap again to hide the toolbar and return to full-screen viewing.

Touch gestures work intuitively for basic navigation, but precise measurements are easier with a stylus on tablet devices. Consider using a capacitive stylus for accurate placement of measurement endpoints and annotation markers. Pinch-to-zoom gestures provide smooth magnification control without requiring toolbar button interactions.

Data Privacy and Security

Since all processing occurs client-side, no patient data transmits to external servers during normal operation. However, exported PNG and JSON files contain identifiable information if the original DICOM files included patient metadata. When sharing exported files, ensure compliance with data protection regulations like HIPAA or GDPR. Consider anonymizing DICOM files before loading them into the viewer for teaching or research purposes.

Be aware that browser caching and local storage may temporarily retain image data and annotations. Clear browser cache after viewing sensitive studies if using a shared computer. For maximum security, use the viewer in a private browsing or incognito mode that automatically clears all cached data upon session termination.

Frequently Asked Questions

Can I use this viewer for clinical diagnosis?

This DICOM viewer is designed for educational, research, and preliminary review purposes. It should not serve as the sole platform for clinical diagnosis or treatment decisions. Medical image interpretation for patient care must be performed on FDA-cleared or CE-marked diagnostic workstations by qualified radiologists using validated diagnostic displays. While the viewer provides professional-grade tools, it has not undergone regulatory clearance for diagnostic use.

What DICOM file types are supported?

The viewer supports standard DICOM files from all common imaging modalities including CT, MRI, X-ray, ultrasound, PET, SPECT, and fluoroscopy. Both single-frame and multi-frame DICOM formats are fully supported. The viewer handles compressed and uncompressed transfer syntaxes, with automatic decompression performed via web workers. Files with or without the DCM extension load successfully as long as they contain valid DICOM headers.

Are my files uploaded to a server?

No, all processing occurs entirely within your browser on your local device. Files never upload to external servers. The viewer uses JavaScript and WebAssembly to parse and decode DICOM data client-side. This architecture ensures complete data privacy and eliminates dependency on internet connectivity after the initial page load. Patient information remains strictly confidential on your computer throughout the viewing session.

Why do some measurements show pixels instead of millimeters?

Measurements display in millimeters only when the DICOM file contains valid pixel spacing metadata. This metadata specifies the physical size represented by each pixel. Some imaging systems do not embed this information, or it may be absent in anonymized or converted files. Check the metadata panel to verify pixel spacing values. If pixel spacing is missing or reads as unavailable, measurements default to pixels. Contact your imaging system administrator if pixel spacing should be present but is missing.

How do I compare two different studies?

Activate compare mode by clicking the Compare button in the toolbar. This creates two side-by-side viewports. Load one study in each viewport using the dedicated file input controls. Enable both synchronization checkboxes to link the viewports for simultaneous navigation and windowing. This synchronized viewing allows direct comparison while maintaining identical viewing parameters. Adjust zoom, windowing, and frame position, and both viewports update together.

Can I view DICOM series with multiple files?

The current version is optimized for viewing individual DICOM files including multi-frame files that contain entire series within a single file. For DICOM series split across multiple files, you would need to load each file separately. Consider using DICOM conversion tools to combine multi-file series into single multi-frame DICOM files before loading into the viewer for seamless navigation through the entire series.

How do I save my annotations?

Use the Export JSON button to save all annotations and measurements from the current viewport as a JSON data file. This file downloads to your computer and can be imported later using the Import JSON button. For visual documentation, use Export PNG to save a screenshot image including all annotations. Always export annotations before closing the viewer or loading a different image, as annotations exist only in the current session and do not persist automatically.

Why does the viewer load slowly on my device?

Loading speed depends on file size, device performance, and browser capabilities. Large multi-frame files or high-resolution images require more processing time. The viewer uses web workers for parallel decoding, but performance still varies by device. Older computers or mobile devices with limited RAM may experience slower loading. For best performance, use modern browsers on devices with at least 4GB RAM and updated graphics drivers. Initial loading of large files takes time, but subsequent frame navigation benefits from caching.

Can I use this on my smartphone or tablet?

Yes, the viewer is fully responsive and optimized for mobile devices. The interface adapts automatically to smaller screens with a collapsible toolbar accessible via a floating action button. Touch gestures including pinch-to-zoom, drag-to-pan, and swipe-to-scroll work intuitively. However, detailed annotation and measurement tasks are easier on larger screens or with a stylus. Mobile viewing is excellent for quick review and consultation but may be limiting for extensive annotation work.

What should I do if an image fails to load?

First verify that the file is a valid DICOM file with proper headers. Try opening the file in another DICOM viewer to confirm it is not corrupted. Check browser console for specific error messages that may indicate the problem. Ensure you are using a modern browser version. Some proprietary DICOM variants or unusual transfer syntaxes may not be supported. Try converting the file to standard DICOM format using a tool like dcm4che or DCMTK if the file uses an uncommon encoding.

Troubleshooting

Image Appears All Black or All White

This typically indicates inappropriate windowing settings. The window center may be too high or too low for the pixel values in your image. Use the WW/WC tool or sliders to adjust windowing. Try dragging vertically to adjust window center until image details become visible. Alternatively, click the Reset button to restore default windowing values appropriate for the detected modality. Very wide window widths can also wash out contrast, so narrow the window width if the image appears uniformly gray.

Annotations Disappear After Loading New Image

Annotations are viewport-specific and do not automatically transfer between images. When loading a new file into a viewport, that viewport’s annotations clear. Always export annotations as JSON before loading different images if you need to preserve your markings. To review annotations on the original image, reload that image and import the saved JSON file.

Synchronization Not Working in Compare Mode

Verify that both viewport synchronization checkboxes are enabled. The checkboxes appear in the top-left corner of each viewport. Both must be checked for synchronization to function. If synchronization works for some controls but not others, ensure both viewports have images loaded. Synchronization only activates after both viewports contain valid DICOM images. Try toggling the checkboxes off and back on to reset the synchronization state.

Frame Slider Not Appearing

The frame slider only displays for multi-frame DICOM files containing multiple frames within a single file. Single-frame images do not show the slider. If you expect multiple frames but the slider is absent, check the DICOM metadata to verify the number of frames. Some DICOM series split across multiple files do not show as multi-frame; each file loads independently and would need to be combined into a multi-frame format using external tools.

Measurements Show Unexpected Values

Verify pixel spacing calibration in the metadata panel. Incorrect or missing pixel spacing leads to inaccurate metric measurements. If pixel spacing appears incorrect, the source DICOM file contains erroneous metadata. Contact the imaging facility or system administrator. For images without pixel spacing, measurements default to pixels, which appear as large numbers. This is expected behavior and indicates uncalibrated images.

Toolbar Not Visible on Mobile

On mobile devices, the toolbar automatically collapses into a floating action button to maximize viewing space. Look for a circular button with a plus symbol in the corner of the screen. Tap this button to reveal the toolbar with all tool options. After selecting a tool, tap the button again to hide the toolbar. This collapsible design provides full-screen viewing while keeping tools accessible.

Export Functions Not Working

Ensure pop-ups are not blocked by your browser. Export functions trigger file downloads that may be blocked by browser security settings. Check for a blocked pop-up notification in your address bar and allow downloads from the viewer. Verify you have write permissions to your download folder. Try exporting to a different folder if permissions are restricted. Some browsers on corporate networks may restrict downloads; contact IT support if exports consistently fail.

Performance Issues with Large Files

Large multi-frame files or high-resolution images may cause performance issues on devices with limited resources. Close unnecessary browser tabs to free memory. Update to the latest browser version to benefit from performance improvements. Clear browser cache if memory usage seems excessive. Consider using a desktop computer rather than mobile device for very large datasets. Enable hardware acceleration in browser settings if available. As a last resort, try converting large files to lower resolution versions for preliminary review.