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Flashcards in hypothalamus pituitary imaging Deck (19)
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1
Q

MRI measures what three properties

A
  1. proton density. 2. T1 relaxation rate: tendency to align with magnetic field. 3. T2 relaxation rate: loss of magnetization
2
Q

Use of contrast in MRI

A

Used to detect leaky capillaries

3
Q

What things show up bright on T1

A

fat, some proteins, blood products, paramagnetic ions such as iron, gadolinium, manganese and some complexes of Ca.

4
Q

What shows up bright on T2

A

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.

5
Q

compare the brain in T1 vs T2 images

A

T1: : White matter is brighter than gray matter. Fluid is generally dark. T2: White matter is darker than gray matter, fluid is bright

6
Q

MRI pituitary imaging sequences

A
  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)
7
Q

Which structures of pituitary show up bright on T1, T2?

A

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

8
Q

Be able to identify the following structures on MRI: adenohypophysis, neurohypophysis, mamillary body, optic chaism, tuber cinerium

A

T1

9
Q

what are mamillary bodies

A

these inferior “bumps” mark the posterior floor of the hypothalamus and receive incoming fibers from the fornix.

10
Q

What is the tuber cinerium

A

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

11
Q

Be able to identify the following structures on MRI: infundibulum, Dorsum sella, cingulate gyrus, corpus callosum, fornix, massa intermedia, suprasellar cistern

A

T1

12
Q

What is the dorsum sella

A

Posterior Bone of Sella Turcica, can be difficult to differentiate from neurohypophysis.

13
Q

What is fornix

A

Connects hippocampi with the Mamillary bodies (main output of hippocampal formations)

14
Q

What is the massa intermedia

A

(AKA intrathalamic adhesion) connects the thalami across midline

15
Q

What is the suprasellar cistern

A

CSF-filled supraclinoid area above the diaphragma sella

16
Q

Which brain structures enhance in T1 with contrast

A

Adenohypophysis (adenomas enhance less though), neurohypophysis is same as in non contrast, infundibulum,

17
Q

What is a flow void

A

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

18
Q

Define pituitary microadenoma

A

<1cm

19
Q

define macroadenoma

A

> 1cm