Dicom Tags

Digital Imaging and Communications in Medicine (DICOM) is a standard that has been developed with a noble goal. Different manufacturers of imaging equipment and software vendors produce various hardware and software. The idea was to come up with a way to allow easy communication between various machines and software solution produced by different manufactures and vendors. If you really want to know how well this went, buy a cup of coffee or lunch for your PACS administrator, and you will get an idea of what worked and what did not very quickly.

Things got better over time, but even in 2019, it is still not uncommon for a direct human involvement to correct or reconcile things. For example, mismatches in the way patient’s name gets spelled or changes from maiden to married name result in major havoc if someone tries to automatically import outside facilities comparison studies.

In addition to routine demographic information, DICOM monster format stores all kinds of technical details. There are two common occasions when a radiologist or researcher need to dig into the labyrinths of DICOM header: to problem solve artifacts on MR images or to get detailed information for research.

DICOM tags are not as uniform as you may expect them to be. Some fields are constant among manufacturers, others are not so much. When it comes to new data such as diffusion MRI, details of acquisition may be hidden in private DICOM fields. Take a look at the table below. Some fields make sense and are fairly uniform among manufacturers, others are so new, that there is not yet uniform agreement. And, some fields like temporal resolution of dynamic MRI may or may not be recorded at all.

General

0008, 1090MR scanner model
0018, 0087Magnetic field strength
0018, 0050Slice thickness
0018, 0088Slice spacing
0018, 0024Sequence name
0020, 1041Slice location
0028, 0030Pixel spacing

Siemens (TM) DWI DICOM tags

0019, 100CB value
0019, 100DDirection
0019, 100EB vector

Phillips (TM) DWI DICOM tags

0018, 9087B value
0018, 9089Diffusion gradient orientation