Image MIME Reference
DICOM-RLE
DICOM Run-Length Encoding
image/dicom-rle
VS
TIFF for Facsimile eXtended
image/tiff-fx
TIFF-FX
A complete technical comparison of DICOM Run-Length Encoding and TIFF for Facsimile eXtended — covering compression, feature support, browser compatibility, magic bytes, and when to choose each format.
Equal browser support
Feature Support
| Feature | DICOM-RLE | TIFF-FX |
|---|---|---|
| Transparency (Alpha) | ✕ No | ✕ No |
| Animation Support | Yes | ✕ No |
| Progressive Loading | ✕ No | ✕ No |
| HDR Support | Yes | ✕ No |
| EXIF Metadata | ✕ No | ✕ No |
| ICC Color Profile | Yes | Yes |
DICOM Run-Length Encoding
image/dicom-rle
Extension
.dcm.dicom
Container
DICOM (PS3.10)
Compression
Lossless (RLE)
Algorithm
Run-Length Encoding (RLE)
Color Depth
8-bit, 16-bit, 24-bit
Developed by
National Electrical Manufacturers Association (NEMA) / ACR
Released
1993
Magic Bytes
44 49 43 4D (at byte offset 128)
TIFF for Facsimile eXtended
image/tiff-fx
Extension
.tiff.tif
Container
TIFF 6.0 Tag Directory Structure
Compression
MH / MR / MMR (CCITT Group 3 & 4) / JBIG / JPEG
Algorithm
CCITT Group 3/4JBIGJPEG
Color Depth
1-bit (Monochrome B&W), 8-bit (Grayscale/Color Indexed), 24-bit (RGB Color)
Developed by
IETF (Internet Engineering Task Force)
Released
1998
Magic Bytes
49 49 2A 00 (Little-Endian) / 4D 4D 00 2A (Big-Endian)
Browser Support Comparison
| Browser | DICOM-RLE | TIFF-FX |
|---|---|---|
Chrome
|
✕ | ✕ |
Firefox
|
✕ | ✕ |
Safari
|
✕ | ✕ |
Edge
|
✕ | ✕ |
IE (Legacy)
|
✕ | ✕ |
DICOM-RLE
DICOM-RLE Strengths
- Guarantees lossless preservation of critical medical data necessary for diagnostics
- Extremely robust metadata structure containing patient information, modality, and spatial geometry
- Faster to encode and decode than complex compression schemes like JPEG 2000
Limitations
- RLE compression offers very low compression ratios compared to modern codecs like JPEG-LS or JPEG 2000
- Zero support in web browsers or standard consumer image viewers
- Strict data privacy regulations (HIPAA/GDPR) make handling DICOM files complex due to embedded PHI
TIFF-FX
TIFF-FX Strengths
- Provides a universal, standardized format for transmitting multi-page documents over IP networks and email (Internet Fax)
- Supports highly efficient telecom-centric compression algorithms (MMR, JBIG) that produce very small files for text documents
- Maintains backwards compatibility with standard TIFF parsers
Limitations
- Not supported natively by web browsers
- Requires complex parsing of TIFF IFD tags to differentiate a true TIFF-FX file from a standard TIFF file
- Usage is slowly declining as traditional faxing is replaced by secure PDF transmission and e-signature platforms
When to choose which format
DICOM-RLE
Use DICOM-RLE when…
- Medical Imaging
- Ultrasound
- X-Rays / CT / MRI
- PACS Archives
TIFF-FX
Use TIFF-FX when…
- Internet Fax (T.37)
- Enterprise Fax Servers
- Document Archiving
- Telecommunications