Tuesday, March 20, 2018

DICOM Experts, Where Art Thou?


This past month alone, I got three inquiries from high tech imaging companies looking for seasoned DICOM professionals; two are wanted on the east coast (Boston), two in rural Arkansas, and if you like skiing and hiking, there is a vacancy in Boulder, Colorado.

One of these positions does not even require US residency, as they are willing to sponsor a work visa for qualified applicants. The reason these inquiries came to me is that there are literally thousands of students who went through the OTech DICOM training over the past 25 years, and therefore, I have a large base of “alumni” among my Facebook and Linked-in friends.

This poses the question, what is an expert anyway? My first source is always the (un)-official source of truth, i.e. Wikipedia:
Historically, an expert was referred to as a sage (Sophos), was a profound thinker distinguished for wisdom and sound judgment. Informally, an expert is someone widely recognized as a reliable source of technique or skill whose faculty for judging or deciding rightly, justly, or wisely is accorded authority and status by peers or the public in a specific well-distinguished domain.
The next question would then be, how to define a DICOM “expert?” To define his or her skills, I like to refer to the official DICOM certification for professionals, which is managed and administered by PARCA. The requirements for this certification include knowing:
1.     Negotiation – How DICOM connections (Associations) are being negotiated and established, i.e. the handshake and agreement on the type of images to be exchanged and encoded such as compression. Note that “images” mean any DICOM file, including dose reports, measurements, presentation states containing overlays etc.
2.     Messages and data elements ­– How DICOM metadata (literally “data about data”), aka DICOM headers that are part of the DICOM file is encoded and can be interpreted.
3.     Storage and Image management – That DICOM protocol services include the capability to query a worklist at a modality, allow for images to be exchanged, get a commitment from an archive about its permanent storage and can communicate study status and changes to the procedure using “Modality Performed Procedure Step.”
4.     Print, Query/Retrieve and compression – There are still a lot of DICOM printers, especially in emerging and developing countries, communicating with the DICOM print protocol, while Query/Retrieve is the interface to a PACS database/archive. Compression specifies what compression schemes are supported and can be negotiated such a JPEG, JPEG2000, MPEG, and others.
5.     DICOM Media – Reliable CD interchange is still a major headache and pain point for many institutions, if only everyone would follow the DICOM standard closely, it would be much easier. One should be familiar with how images are stored on a CD i.e. as so-called “part-10” files and how the DICOMDIR or directory is structured.
6.     Image quality and Structured Reports – DICOM defines a so-called pixel pipeline which specifies all the steps that the pixel data is going through prior to being displayed such as different greyscale/color schemes, annotations, Look-Up Tables, etc. Displaying the images on a monitor that is calibrated using the DICOM defined standard greyscale and color mapping is critical to ensuring that every discreet pixel value is mapped into a distinguishable greyscale or color value. Structured Reports are used for measurements, CAD marks, dose information, key images and other information related to image metrics.
7.     VR’s and conformance – A VR or Value Representation defines the data types, i.e. maximum length and encoding of the DICOM data elements. Knowing where and how to evaluate these allows for spotting errors, the most frequent being exceeding maximum length, invalid codes in the fields, invalid characters, etc. Conformance is critical as it allows checking whether two DICOM devices can communicate using the conformance statements.
8.     Networking – This includes addressing, i.e. use of IP address, port number, and AE-Title, using tools such as DICOM network sniffers as well as interpreting the communication logs and dumps.
9.     Troubleshooting – To troubleshoot DICOM connections, one would use simulators and test tools. The most basic tool is the use of the DICOM Verification, as well as using multiple test images such as those for testing the imaging pipeline and be able to change negotiation parameters
10.  New DICOM extensions – There are several DICOM extensions, such as the specifications “for processing” aka raw data, which typically is used to perform CAD, the definition of the new multi-frame enhanced CT, MR and other image types, using the Universal Worklist and the new pathology image definition. Last but not least, is DICOMWeb, which uses RESTfull services, mostly being used for mobile access and through web browsers and is the counterpart of the HL7 FHIR services.
As you can see, there is quite a bit involved with being a “DICOM expert.” If you feel like honing your skills, you might want to check out available textbooks, training or pursue certification. If you feel you would qualify for one of the “expert positions,” feel free to forward your resume and I’ll be happy to share it with those inquiring about hiring.



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