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34 Section I: Diagnostics and Planning

A B

C

D

Figure 4.6 Transverse plane CT (A) and T2* GRE MRI (B) of a Labrador Retriever with subdural hematoma and intraparenchymal hemorrhage due to coagu-
lopathy secondary to Angiostrongylus vasorum infection. The subdural hematoma (arrow in A, B) is seen clearly on both the CT and MRI but the bleeding
within the cerebellum and brainstem (arrowheads) is seen much better on the MRI. Transverse CT (C) and T2* GRE MRI (D) of a Cavalier King Charles
Spaniel with head trauma. The MRI shows intraventricular hemorrhage with blood products ventrally (arrows in D) within both lateral ventricles. No abnor-
malities are visible on the corresponding CT.

paramagnetic effects is with a GRE pulse sequence. In this sequence, magnetic gradient used for proton rephasing and image formation,
magnetic gradients are used in a critical step of proton rephasing a conspicuous artifact, called a magnetic susceptibility artifact, is
needed for image formation; this is very different from the more created [54]. The artifact essentially destroys the image in the
commonly used spin‐echo pulse sequence where refocusing mag- region of hemorrhage and creates a region of signal void [55].
netic gradients are not used. Because the paramagnetic effects of Inclusion of a GRE pulse sequence can be very useful for confirm-
hemorrhage, especially those of hemosiderin, interfere with the ing or excluding hemorrhage. A newer form of GRE imaging called