An absence of normal structures on brain CT, in many cases, will lead you to the correct diagnosis, especially when the abnormalities are symmetric or subtle.Īs an analogy, if you were asked what is wrong with the image of a house after a hurricane, you would need to know that there used to be a chimney on the roof before you could recognize that it is missing. While some may think the goal when viewing a CT is to look for a focal abnormality (like a hemorrhage or mass), it is just as important to look for normal structures.
Metal and high-density tissues such as bone have high attenuation and appear as shades of white. Fluid, air, and low-density tissues such as fat have low attenuation and appear as shades of gray on a computed tomography (CT) scan. Bone and metal, on the other hand, are displayed on a CT image as white because of their high attenuation.įigure 2. Fluid, fat, and air are dark because they have low attenuation. Structures with high attenuation will limit x-ray passage and be displayed as shades of white. X-rays easily pass through structures with low attenuation, and they are represented as such on the image with a shade of gray on a CT scan. The word attenuation is used to describe how tissues interact with the x-ray beam. High and low attenuation on a brain CT scan When reading a brain computed tomography (CT), the left side of the image depicts the patient’s right side, and the right side of the image depicts the patient’s left. This means that as you look at the axial CT images, your left is the patient’s right side.įigure 1.
When you view an axial CT scan, the convention for left and right is established by imagining that you are looking at the scan while standing at the feet of the patient.
Which is right and left on sagittal ct how to#
Before going into detail about how to read and interpret brain computed tomography (CT) images, first, let’s review how axial CT images are displayed.
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