CT or MRI??

A common question presented when considering advanced imaging options is whether it is more appropriate to pursue a CT or an MRI.  The images below present a comparison of brain/skull imaging.  CT’s will show brain changes (tumors, cysts, hydrocephalus) but not as clearly as an MRI.  That said, MRI has it’s own “cons”.  More detailed information explaining the difference is below the examples.  The and the best option should be discussed with your primary veterinarian based on

Brain MRI

A post-contrast MRI of the brain.  The view is a sagittal cross section of a dog. The nose is to the left, and the spinal cord can be seen coursing to the right under the cerebellum. More specific detail is visible within the regions of the brain.

Brain CT

A post-contrast CT scan of a dog skull.  Axial, sagittal, and coronal views are present on the left with the sagittal view present in the larger image to the right.  Contrast is visible but the x-ray technology is only able to provide general details in the brain.

 

 

 

 

 

 

 

 

CT of brain

The above image shows another post-contrast CT of the brain. Sagittal and axial cross sections are on the left, and a coronal view is on the right. A tumor (green arrows) is highlighted by the contrast, but more precise details are not able to be appreciated.

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An MRI (Magnetic Resonance Imaging) utilizes magnetic properties to produce images.  When the unit (the giant magnet) is turned on it polarizes all the molecules present.  When it is turned off, the energy released by the cells is collected and reconstructed by a computer to demonstrate the body in three dimensions.  The rule of thumb is, the higher the water content (i.e. brain and spinal tissue in particular) the better it is to choose MRI.  PRO’s include the tremendous detail they provide and the use of a magnet (vs. radiation); CON’s include the increased cost of the studies (the technology is much more expensive), increased time under anesthesia (it takes longer to do the studies), and availability (the nearest sites with MRI are at the Veterinary Specialists of Rochester or Cornell University).

CT scans (Computed Tomography) obtain images using X-ray technology.  A series of X-rays are taken in multiple planes and are then reconstructed by a computer to demonstrate the body in three dimensions.  The resulting images are based on gray-scale as it would normally be seen in a traditional X-ray image.  Variations within tissue are based on the density of the location.  CT can still be used (and frequently is!) for brain and spinal imaging, but it will not provide the same degree of detail.  PRO’s include the decreased cost of the imaging studies, decreased time under anesthesia, and local access in WNY.  CON’s include the lack of detail provided by the MRI technology and exposure to radiation (although the Vimago produces significantly less compared to traditional units).