Study Search Patterns: CT Head (Non-Contrast)

OVERVIEW

This page will cover a search pattern that can be used to read an head CT scan (specifically a non-contrast scan).

Disclaimer: It is important to remember that many different versions of a search pattern for a CT scan of the head without contrast. Factors that may influence a search pattern may include: the preference of the person interpreting the scan, the amount of time available to read the scan, the study question, the software being used for image interpretation, the amount of monitors being used during the reading, as well as many others.

This page just provides one example in a specific context of how to apply a specific search pattern. The goal is to provide a foundation to learners so that they will be in a better position to craft their own search pattern(s).

BEFORE YOU START BE FAMILIAR WITH WINDOWING

This page, and the associated videos, assume that the reader is familiar with the concept of CT windowing and how to use different types of windowing settings for image interpretation. This page provides a good review of CT windowing if needed.

OUTLINE OF SEARCH PATTERN

This particular search pattern follows the “outside in” approach and the major sections are as follows below:

  1. Scout Images
  2. Soft Tissues 
  3. Bones
  4. Intracranial Contents Part 1 (Dependent Portions)
  5. Intracranial Contents Part 2 (Ventricular System)
  6. Intracranial Contents Part 3 (Extra-Axial Pathology)
  7. Intracranial Contents Part 4 (Brain Parenchyma)
STEP 1 SCOUT IMAGES

It is important to realize that most all CT scans will include scout images that essentially are equivalent to plain film radiographs of the scanned region. It can be useful to look at these scout images first as they can provide some information that may be heard to appreciate on the cross sectional imaging (for example some hardware or fractures may be most easily appreciated on the scout images).

SETTING UP MULTIPLE ORIENTATIONS

After finishing looking at the scout images, it can be very helpful to set up multiple orientations of the scan so you can co-localize findings and anatomy on multiple views easily. The video below shows how this can be done easily and how reference lines can be turned on so that you know on multiple views where exactly you are looking on a scan.

STEP 2 SOFT TISSUES

The first area to look at in the outside in approach (after the scout images, and after you have configured your viewing settings) is the soft tissues. It can be useful to divide the soft tissues into 4 sections: anterior, posterior, right, and left. When scanning up and down the head, one can begin with the anterior soft tissues and then alternate between other sections as the scan up and down the scan. Make sure to use an appropriate window like the abdominal window to evaluate the soft tissues. 

STEP 3 BONES

After finishing the soft tissues, the bones can be evaluated from the top of the scan to the bottom. The video below shows how to evaluate the bones in multiple planes. Make sure to utilize the bone windows and thinner slices/bone reformats/bone kernels when looking at the bones particularly in the axial orientation (if available). 

STEP 4 INTRACRANIAL CONTENTS (PART 1 DEPENDENT PORTIONS)

After finishing the bones, it is time to evaluate the intracranial contents on the head CT scan. This is a big area to cover so this portion of the search pattern has been broken down into four parts each that cover a different category of intracranial contents. The first part goes over looking through the dependent portions of the intracranial contents for things like blood, mass effect, and in certain cases vascular pathology. For this step a fairly standard brain window is utilized. 

STEP 5 INTRACRANIAL CONTENTS (PART 2 VENTRICULAR SYSTEM)

Next the ventricular system can be evaluated starting from the lateral ventricles to evaluate for pathology like hydrocephalus or intra-ventricular blood. For this step a fairly standard brain window is utilized. 

STEP 6 INTRACRANIAL CONTENTS (PART 3 EXTRA-AXIAL PATHOLOGY)

Next the extra-axial space can be interrogated for the presence of collections, bleedings, masses, or other extra-axial pathology. For this step a fairly standard brain window is utilized in addition to an epidural window that is around the W130 L50 setting. 

STEP 7 INTRACRANIAL CONTENTS (PART 4 BRAIN PARENCHYMA)

Finally the brain parenchyma itself can be evaluated for any pathological findings. For this step a fairly standard brain window is utilized as well as a stroke window which makes visualizing hypodensities easier. 

 

 

 

 

Page Updated: 01.20.2020