Flashcards in hypothalamus pituitary imaging Deck (19):
MRI measures what three properties
1. proton density. 2. T1 relaxation rate: tendency to align with magnetic field. 3. T2 relaxation rate: loss of magnetization
Use of contrast in MRI
Used to detect leaky capillaries
What things show up bright on T1
fat, some proteins, blood products, paramagnetic ions such as iron, gadolinium, manganese and some complexes of Ca.
What shows up bright on T2
fluid, gliosis (from increased water content), tumors that have increased water content. Tumors with low cytoplasmic/nuclear ratios have low T2 signal (dark). Other T2 dark substances are old blood, hemosiderin, certain complexes of calcium (bone cortex), air and high concentration protein complexes.
compare the brain in T1 vs T2 images
T1: : White matter is brighter than gray matter. Fluid is generally dark. T2: White matter is darker than gray matter, fluid is bright
MRI pituitary imaging sequences
1. High resolution Sagittal and Coronal pre and post contrast T1-weighted images. 2. High resolution Coronal T2-weighted images. 3. 1st time studies usually include whole brain (for associated or incidental pathology)
Which structures of pituitary show up bright on T1, T2?
Anterior pituitary: Enhances (NoBBB) and low T2. Intermediate/septum: slightly brighter on T2. Posterior: sometimes bright on T1 due to neuropeptides, does not fat saturate
Be able to identify the following structures on MRI: adenohypophysis, neurohypophysis, mamillary body, optic chaism, tuber cinerium
what are mamillary bodies
these inferior “bumps” mark the posterior floor of the hypothalamus and receive incoming fibers from the fornix.
What is the tuber cinerium
lies at the inferior floor of the hypothalamus, posterior to the infundibulum and anterior to the Mamillary bodies. It is one of two common sites of hypothalamic hamartomas
Be able to identify the following structures on MRI: infundibulum, Dorsum sella, cingulate gyrus, corpus callosum, fornix, massa intermedia, suprasellar cistern
What is the dorsum sella
Posterior Bone of Sella Turcica, can be difficult to differentiate from neurohypophysis.
What is fornix
Connects hippocampi with the Mamillary bodies (main output of hippocampal formations)
What is the massa intermedia
(AKA intrathalamic adhesion) connects the thalami across midline
What is the suprasellar cistern
CSF-filled supraclinoid area above the diaphragma sella
Which brain structures enhance in T1 with contrast
Adenohypophysis (adenomas enhance less though), neurohypophysis is same as in non contrast, infundibulum,
What is a flow void
Flowing blood often brings non-excited fluid into the field of electromagnetic excitation. It thus has no signal and creates a “flow void”. This occurs in the cavernous sinuses on T1 and T2 images
Define pituitary microadenoma