Introduction to DICOM - Chapter 4 - DICOM Objects Explained: IODs, Modules, and How to Create a Secondary Capture Image (SC IOD) in C#

Chapter 4 – DICOM Objects

In chapter 3 we’ve learned about DICOM elements. Every element is one piece of typed data with a pre defined, well specified meaning. There are thousands of DICOM elements (See chapter 6 of the standard) from the very basic attributes of patient name and birth date to the most esoteric uses of 3D surface vortices. In this chapter we’re going to collect elements into image object that is called Secondary Capture Image. 

The guys at DICOM did a lot of very good work and created well defined classes for a very detailed Data Model. This is why I always advise to dig in the DICOM standard before designing your imaging device software because there’s a very good chance that the DICOM technical committees already did the work for you and you can save a lot of expansive design time this way. 

In a way DICOM objects definitions are similar to object oriented programming. I prefer though the analog to interfaces specifications. The motivation to adhere to a standard is to enable interoperability. By detailing information object definitions (IOD’s) DICOM enables us to exchange virtual objects between applications without knowing in advance anything about the application we are going to interface with. 

In this chapter I'm going to complete chapter’s 3 examples by adding elements to the object until it’s a valid Secondary Capture Image according to the DICOM standard. Secondary Capture Image is the simplest DICOM image object. Secondary Captures is not related to any specific device. It has the very basic set of elements that a DICOM application needs in order to display and archive a DICOM image properly.

Getting Oriented using the Image Plane Module

 Just before diving into how to get oriented using the DICOM Image Plane Module, so we can put the letters right in our viewer, I want to get equipped with few more latin words so we understand what Radiologists are mumbling. If you're a Doctor, please be patient with us programmers. 

Cuts! Three major cuts we have (or planes): 

Transverse (AKA Axial) divides head from feet

Axial Cut

Sagittall Cut - right between the eyes

Sagittal Cut

and Coronal Cut - the Filet

Coronal Cut

And now that we're done with Anatomy let's do some Geometry. In this post I'm going to start explaining the use of the Image Plane Module. To refresh on Modules read chapter 4 of the DICOM Tutorial. The Image Plane module is part of the CT Image IOD and the MR Image IOD and any other object that have a frame of reference, i.e. that has a spatial coordinates system related to the patient or in other words is a 3D scan of the body.