hypothalamus pituitary imaging

Question 1

MRI measures what three properties

Answer 1

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

Question 2

Use of contrast in MRI

Answer 2

Used to detect leaky capillaries

Question 3

What things show up bright on T1

Answer 3

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

Question 4

What shows up bright on T2

Answer 4

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.

Question 5

compare the brain in T1 vs T2 images

Answer 5

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

Question 6

MRI pituitary imaging sequences

Answer 6

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)

Question 7

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

Answer 7

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

Question 8

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

Answer 8

T1

Question 9

what are mamillary bodies

Answer 9

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

Question 10

What is the tuber cinerium

Answer 10

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

Question 11

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

Answer 11

T1

Question 12

What is the dorsum sella

Answer 12

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

Question 13

What is fornix

Answer 13

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

Question 14

What is the massa intermedia

Answer 14

(AKA intrathalamic adhesion) connects the thalami across midline

Question 15

What is the suprasellar cistern

Answer 15

CSF-filled supraclinoid area above the diaphragma sella

Question 16

Which brain structures enhance in T1 with contrast

Answer 16

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

Question 17

What is a flow void

Answer 17

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

Question 18

Define pituitary microadenoma

Answer 18

<1cm

Question 19

define macroadenoma

Answer 19

> 1cm