Identify Compressed DICOM image by tag

Question

How to identify whether a dicom image is in compressed format ? And also want to know how to read compressed image pixel data ?

Answer 1

You can use command line tool to dump this type of information, eg gdcminfo:

$ gdcminfo 012345.002.050.dcm  
MediaStorage is 1.2.840.10008.5.1.4.1.1.4 [MR Image Storage]
TransferSyntax is 1.2.840.10008.1.2.4.70 [JPEG Lossless, Non-Hierarchical, First-Order Prediction (Process 14 [Selection Value 1]): Default Transfer Syntax for Lossless JPEG Image Compression]
...

Pay attention that for the case of JPEG 2000 and JPEG-LS the transfer syntax itself is not sufficient to indicate whether or not the Pixel Data stream has been lossy or lossless compressed. This could be important for your organisation as lossy compression could impact professional interpretation.

Ref: http://gdcm.sourceforge.net/html/gdcminfo.html

Answer 2

Encoding of the data set embedded in a Dicom file (or message) is specified through the transfer syntax UID tag (0002,0010). There are many types of compressed ones (JPEG, RLE, JPEG Lossless, JPEG 2000, ...)

For more info see section 10 of PS3.5.

As for reading the compressed image data, see the various DICOM libraries, it depends on the language you use of course.