Perez Ch 35: Imaging and Anatomy Flashcards
Images are displayed within a matrix composed of voxels, each representing a
volume of radiodensity that is quantified by a linear attenuation value called a
Hounsfield unit (HU). Each voxel is assigned an HU in the range of −1,000 to
1,000 corresponding to a shade of gray that represents the attenuation difference
between a given material and water
air is the least dense
material with an HU value of −1,000, whereas water has an HU value of 0. Soft
tissues have a range of attenuation with typical HU values as follows: fat (−120),
blood (30), muscle (40), and bone (>300).
IV contrast agents are excreted through the kidneys, are nephrotoxic, and are
not typically administered to patients with impaired renal function
glomerular
filtration rate [GFR] < 60, creatine [Cr] < 2.0, though institutional policies vary
TR and TE dramatically affect image
contrast and determine which tissue properties are selected. T1-weighted images,
in which fluid is dark and fat is bright, are generally good at depicting anatomy;
T1-weighted images are generated by selecting
short TR (typically ≤800 ms) and
short TE values (≤30 ms).
T2-weighted images, in which fluid is bright and fat is
dark, are fluid-sensitive and can depict areas of pathology; T2-weighted images
are generated by selecting
long TR (≥2,000 ms) and long TE values (≥60 ms)
The central nervous system consists of the brain and spinal cord. Both are
covered with three meningeal layers—the dura mater, arachnoid mater, and pia
mater. Meningiomas are the most common tumors arising from the meninges.
They arise from ________ but are typically affixed to the underside of the
dura mater
arachnoid cells
The arachnoid mater and pia mater are considered the ______with the
intervening space (subarachnoid space) filled with cerebrospinal fluid (CSF).
leptomeninges
Leptomeningeal
involvement occurs most frequently with
pediatric brain tumors (e.g.,
medulloblastoma), acute lymphoblastic leukemia, and some solid cancers (e.g.,
breast cancer, melanoma, and lung cancer in particular).
The
diencephalon includes the ____
thalamus, hypothalamus, and third ventricle
originates in the ventral aspect of the brainstem, ascends on the clivus, and
crosses the internal carotid artery near the superior aspect of foramen lacerum
before entering the cavernous sinus. It then exits the skull through the superior
orbital fissure.
CN VI
The motor and sensory nerve roots of CN V exit the pons and
pass underneath the free edge of the tentorium cerebelli into the Meckel cave,
forming the trigeminal (gasserian) ganglion. From the ganglion, V1 and V2 enter
the cavernous sinus and subsequently exit the skull through the ______ respectively. V3 exits the skull through foramen
ovale.
superior orbital
fissure and foramen rotundum,
Four cranial nerves, including two branches of CN V, pass
through the cavernous sinus. Within the sinus, _____) is
located most superiorly, whereas the ____
) is located most
inferiorly.
the oculomotor nerve (CN III
maxillary nerve (CN V2
The anterior skull base includes the cribriform plate (consisting of portions of the frontal and ethmoid bones), which is perforated by branches of the _____ and roofs of the orbits (formed from portions of the frontal and sphenoid bones). The central portion of the sphenoid bone, the basisphenoid, contains the sella turcica. The basisphenoid and basiocciput are joined by a spheno-occipital synchondrosis, which eventually fuses and forms a structure known as the clivus. Between the basisphenoid and the lesser wing of the sphenoid bone is the optic canal ______ and between the basisphenoid and the greater wing of the sphenoid is the superior orbital fissure _______. Within the greater wing of the sphenoid bone is an anteriorly directed canal known as the foramen rotundum ______(, and an inferiorly directed canal known as the foramen ovale. Posterolateral to the foramen ovale is the foramen spinosum, which carries the _______
(cranial nerve [CN] I)
(carrying CN II),
(carrying CN III, IV, V1, and VI)
carrying V2)
middle meningeal artery.
Within the petrous temporal bone is the internal auditory canal, which carries _____ Between the portion of the temporal bone containing the inner ear and the clivus is the apex of the petrous temporal bone, a structure that can occasionally be pneumatized
CN VIII to the structures of the inner ear and acts as a conduit for the facial nerve (CN VII).
The jugular foramen is located between the petrous and mastoid portions of the temporal bone and the occipital bone, and carries the jugular bulb, which is the transition between the sigmoid sinus and the internal jugular vein. The jugular foramen is parcellated into the posterior pars vascularis ______, and the smaller anteromedial pars nervosa ______ Within the exoccipital portion of the occipital bone are the hypoglossal canals, carrying the _____
(carrying CN X and XI)
(carrying CN IX).
right and left hypoglossal nerve (CN XII).
The vertebral column typically consists of _____
33 bones (7 cervical, 12 thoracic, 5
lumbar, 5 sacral, and 4 coccygeal).
In adults, the spinal
cord typically ends at the _____interspace (termed the conus medullaris). In an
infant, the spinal cord terminates at L2 or L3. However, the spinal nerves
continue to descend within the spinal canal (termed the ______).
L1-2
cauda equina
The subarachnoid space, containing CSF, typically extends to the _____. At this level, the meninges fuse together and extend caudally as
the_____ which anchors the spinal cord to the coccyx.
second sacral vertebral body
filum terminale,
The hallmark
spectroscopic pattern of brain tumors is an increase in ___-containing
compounds and a decrease in ___relative to normal brain tissue
Cho
NAA
Neck Node Level II is subdivided into anterior (level IIA) and posterior (level IIB)
regions, as defined by the ______. Level II contains
the jugulodigastric node at the level of the jugular vein as it crosses the ________ and is a common lymphatic pathway for the
majority of the upper aerodigestive tract.
posterior border of the jugular vein
posterior belly of the digastric muscle
Neck Node Level V contains the posterior triangle of the neck, boarded by _______, and is at particular risk for nasopharyngeal primaries.
the trapezius posteriorly, the SCM anteriorly, and the
clavicle inferiorly