Upgrading to 3Dicom Pro which gives users the ability to access many more features and further improve analysis of medical scans. Upgrading to Pro has allowed us to access features such as bulk exporting images, measuring scans and annotating. One of the most significant features that Pro allows us to do is access DICOM meta-tags. So what exactly are DICOM meta tags?
Just as ordinary digital images now contain hundreds of meta-tags with location, aperture size, zoom level and much more, so too do medical images. In fact, Digital Imaging and Communication in Medicine (DICOM) files which are used for radiological imaging, from X-rays through to PET scans, can contain more than thousand meta-tags. DICOM meta-tags provide us with an understanding on the file we have imported itself. Each different scan we upload to DICOM will have different information within the meta tags as each scan is different.
While many of the DICOM tags are highly technical and relate to specific settings on the device, there are also numerous fields which are highly informative for referring physicians and patients themselves.
Viewing meta-tags in the DICOM viewer is very simple. To begin, simply load the scan in and click the ‘connect’ button on the left tab shown below. This feature is only available for Pro or Surgical users. Lite users of 3Dicom will be unable to use this feature. For a guide on how to upgrade from Lite to Pro, follow this in-depth guide.
To view the different meta tags, we can scroll down with our mouse or use the scroll bar on the side to make our way down and view the different meta-tags in the list. To compliment this, the software has also implemented a search bar in which we can enter any meta-tag name. This makes it easier for us if we would like to find a certain meta-tag without scrolling through them all.
Whilst the DICOM meta-tags provide us with plethora of information about our scan, from file name to the amount of pixels, this amount of information can be very daunting for new users or those with a limited medical background.
Next, we will uncover what some of the meta-tags do and how to interpret them. This will help those who have limited knowledge about the DICOM software or scan interpretation.
There is over 70 different types of meta-tags within the DICOM viewer that provide us with an extensive amount of information on the scan. The guide below will uncover a number of the DICOM meta-tags and what they mean.
FilePath is the first meta-tag that is shown in our list. ‘FilePath’ is the location in which our scan is located on our computer. Common locations include our desktop, downloads or custom folder we have nominated.
SpecificCharacterSet refers to the language DICOM uses to encode information within the scan. Different languages within DICOM will have a different character set correlating with a specific tag. One of the more common SpecificCharacterSet meta tags will be ISO_IR 192 which is a meta-tag for the popular UTF-8 unicode which is used across most platforms online.
StudyDate refers to the date the study was performed. The StudyDate runs on a Gregorian Calendar with the year, month and day respectively. For example, if our StudyDate meta-tag was 20180615, our study was performed on the 15th of June, 2018.
StudyTime is the time the study was performed. This meta-tag follows the form of a 24 hour clock. For example, if our StudyTime was 145800, our study was performed at 2:58 pm.
‘Modality‘ is the type of scan we are analysing. There are many different types of scans we can load into the DICOM viewer. The more popular modes include CT (Computed Tomography) MR (Magnetic Resonance) , US (Ultrasound) or ES (Endoscopy).
‘Manufacturer’ refers the equipment used to perform the scan. This meta-tag will list which companies equipment was used. Some common manufacturers include ‘NewTom’, ‘SIEMENS’ and ‘Phillips Medical Systems.
‘PatientName’, ‘PatientID’ and ‘PatientSex’ are all meta-tags that directly relate to the subject that the scan was performed on. The ‘PatientName’ will list the subjects name, ‘PatientID’ will list the subject’s identification number and ‘PatientSex‘ will either list M (male) or F (female).
These meta-tags will often be listed as ‘Anonymized’ or not listed at all if the subject would like to remain anonymous or unlisted.
SliceThickness is the size of each slice within a scan. A slice is each different image within a scan, and when loaded up into DICOM, the scan should comprise of hundreds to thousands of slices (images). The SliceThickness is measured in millimeters (mm).
For example, if our SliceThickness was 0.3, each slice would be 0.3mm in size. Larger parts of the anatomy such as the chest or lungs would be better analysed with larger slices, however, smaller parts of the anatomy with finer details such as the jaw or brain would better analysed with thinner slices.
PixelSpacing refers to the physical distance of each pixel within the subject measured in millimetres (mm). The first value is the row spacing in ‘mm’ and the second value is the column spacing in ‘mm’ between each pixel respectively.
For example, if our PixelSpacing was 0.3/0.3, each pixel, both horizontally and vertically would be 0.3 mm apart. ‘PixelAspectRatio’ is linked to our PixelSpacing. The PixelAspectRatio is the ratio of our horizontal and vertical pixels. With our PixelSpacing of 0.3/0.3, our PixelAspectRatio would be 1/1.
Let’s say our PixelSpacing was 0.3 mm/0.2 mm, our correlating PixelAspectRatio would be 6/5.
Congratulations. You have just learnt how to view your scan’s meta-tags in the 3Dicom viewer. For any questions or queries on other meta-tags, please do not hesitate to contact us.
Please note that this blog is purely for educational and marketing purposes and doesn’t not purport to be medical advice. 3Dicom is currently registered as a TGA Class 1 Visualisation device and is not approved for diagnostic purposes.