Small animal CT and MRI Flashcards
The orbital ligament is visible as a
a. hyperattenuating structure on CT images and a hypointense structure on T1 and T2 images on MRI
b. hypoattenuating structure on CT images and a hypointense structure on T1 and T2 images on MRI.
c. hyperattenuating structure on CT images and a hyperintense structure on T1 and T2 images on MRI.
d. hypoattenuating structure on CT images and a hyperintense structure on T1 and T2 images on MRI.
a. hyperattenuating structure on CT images and a hypointense structure on T1 and T2 images on MRI
MRI is less sensitive than CT for the evaluation of the orbital bone and mineralized tissue, but is superior in the assessment of the globe, optic nerve, and/or optic chiasm. False or True
True
Which is the correct answer:
a. On a T1W image, fluid are dark (hypointense), fat is bright (hyperintense) and have a high anatomical resolution
b. On a T1W image, fluid are bright (hyperintense), fat is dark (hypointense) and have a high anatomical resolution
c. On a T2W image, fluid are bright (hyperintense), fat is dark (hypointense)
d. On a T2W image, fluid are dark (hypointense), fat is bright (hyperintense) and have a high anatomical resolution
a. On a T1W image, fluid are dark (hypointense), fat is bright (hyperintense) and have a high anatomical resolution is the correct answer.
On a T2W image, both fluid and fat are bright (hyperintense) and other soft tissues are dark (hypointense). They have a poorer anatomical resolution then TW images
On CT, areas of increased and decreased X-ray attenuation are referred to as ‘hyperdense’ and ‘hypodense’. True - False
True. On CT the lens has the highest attenuation of the globe (more white then the other structures)
Cellulitis or myositis results in increased soft‐tissue attenuating material or T2 hyperintensity of the orbital tissues. True - False
True. The volume of the tissues appears greater, and there is loss of definition of the normal fat and extraocular muscle.
Which orbital tumor has a predilection to the orbit in dogs, with CT and MR imaging characteristics of extensive, fluid‐filled cavities within the orbit and surrounding fascial planes? They can extend to the temporomandibular joints and mimic a salivary mucocele.
Myxosarcoma
Which tumor typical for cats, is an invasive, low-grade neoplasm affecting the orbital tissues. CT and MR images show diffuse thickening of the orbital tissues, sclera, and eyelids with intense contrast enhancement. The disease often affects both eyes and/or the oral cavity
Restrictive orbital myofibroblastic sarcoma (which was previously named idiopathic sclerosing orbital pseudotumor)
Which is the wrong answer?
a. The pterygoid muscle lies medial to the zygomatic salivary gland
b. The optic chiasm is visible within the calvarium
c. The optic nerve is hyperattenuating and travels toward the optic canal
d. The lacrimal gland is ventral to the orbital ligament and is contrast enhancing
C. The optic nerve is hypoattenuating (fig 1.5.1 pg 81)
What is the MR characteristic of most melanoma ?
Hyperintense on TW1 and hypointense on T2W
How does appear cataract on CT and MRI
On CT : hyperattenuating
On MRI : decreased intensity
On CT if hyperattenuating material is seen caudal to the detached retina, what does it represent ?
Proteinaceous cells or hemorrhage
