Brain imaging course – 3 – How to review brain cases
This video is the third in a series of a brain imaging course. In this video, we talk about basics of how to review brain cases on your own, including some tips for how to get effective at finding abnormalities and learning your on your own.
Check out the entire course if you haven’t already.
Basics, slice thickness and reformats
When you are reviewing brain cases, you need a structured way of looking at each case to make yourself a sensitive and effective radiologist. This is called a search pattern. You also need to know the ways in which the different images you are provided are different. For example, images can be provided at different thicknesses. In general, thinner images have sharper edges but more noise. Thicker images are better for looking at the bones.
We also have different reformats. On CT, that is usually from one set of data that is displayed in a different plane. The most conventional is perpendicular to the long axis of the body, or axial. Coronal is parallel to the face. Sagittal is parallel to the long axis of the nose. Each of these views has relative strengths and weaknesses.
CT density, window, and level
CT images are standardized for the degree of x-ray absorption, which is closely tied to the density of the material. Each type of tissue has a typical expected density that will be roughly the same on different scanners.
The window and level of a set of images control what is shown on the screen at one given time. The window is the size of the range, or width of the range, of data shown. The level is the center of the range being shown, sometimes referred to as the center. These values are akin to brightness and contrast, although somewhat more exact.
Brain window is structured to see the difference between gray matter and white matter, which is very small, but is poor at seeing very dense structures like bone. For that, a much wider window, the bone window is used.
Basic search pattern
When you are looking at a CT, you need a pattern for looking at each feature in the images. I usually start from the bottom, looking at the brain and focusing on symmetry. Then I move to the bone windows, checking the calvarium, temporal bone, orbits, and sinuses. I may spend an extra minute or two looking at the orbits and soft tissues. To learn more in detail about a head CT search pattern, check out the video.
When reviewing an MRI, you have a similar strategy, but given the different strengths and weaknesses of each sequence, you use each one with a slightly different emphasis. To learn more in detail about how to review a brain MRI, check out the video overviewing MRI sequences and how to review them.
Thanks for tuning into the video about general approaches to brain imaging. On the next video, we’ll have a structured review of a normal case that you can follow along with on your own.