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Transcript of RADIOLOGY TEACHING CONFERENCE - entnyc.com · RADIOLOGY TEACHING CONFERENCE John Athas, MD Monica...
RADIOLOGY TEACHING
CONFERENCE
John Athas, MD
Monica Tadros, MD
Columbia University, College of Physicians & Surgeons
Department of Otolaryngology- Head & Neck Surgery
September 27, 2007
CT SCAN IMAGING
Uses ionizing radiation to create cross-sectional images
Images separate planes based on relative density measured in Hounsfield units Bone is maximally bright [+1000 Hounsfield units],
Air is black [-1000 Hounsfield units]
Most useful to evaluate bone
KEY Point: Fat [-80 Hounsfield units] is darker than soft tissue or muscle allows any soft tissue bordered by a fat plane to be easily seen
allows displacement of a fat plane to signal pathology
Intravenous iodine contrast can be given to further stratify signal intensity among tissue planes helps many lesions become more conspicuous by identifying
vascularization of tissues
MAGNETIC RESONANCE
IMAGING
Uses a magnetic field to align protons and radiofrequency pulses to alter their precession. The protons subsequent relaxation time is used in generating an image.
Each tissue type emits a characteristic wave that corresponds to a sequence specific signal T1 sequence
T2 sequence
T1 with gadolinium sequence
FLAIR sequence
DWI sequence
Gradient-echo T2* sequence
T1 sequence
Conventionally uses traditional spin echo technique
for acquisition
Fat [blood, viscous protein] are very bright.
Muscle is gray
Fluid [CSF] is dark gray
T1 with gadolinium sequence
Gadolinium is the intravenous contrast agent
administered to identify vascularized tissues signaling
the presence of a mass
KEY Point: Gadolinium contrast sequence implies
T1 imaging
T2 sequence
Uses fast-spin echo technique for acquisition
Fluid [CSF] is very bright
Fallacy that fat is dark --fat is less bright on T2
Diffusion weighted imaging [DWI]
Surveys the movement of water within a pathologic lesion. Dark lesions are more likely fluid-filled or cystic lesions with
high diffusion.
Bright lesions on DWI are more likely solid lesions with restricted diffusion DWI is most advantageous in evaluating brain pathology and CPA
tumors
DWI is limited in determining head and neck and temporal bone pathology
Clinical Correlation: petrous apex cholesteatoma/epidermoid is a temporal bone lesion not well seen on DWI. Yet CPA epidermoid is well seen as bright on DWI therefore distinguishing it from other CPA tumors
FLuid Attenuated Inversion Recovery [FLAIR]
Surveys T2 bright lesions by suppressing free water
which is normally hyperintense on T2 images
Similar to the concept of fat suppression, FLAIR
sequence suppresses thin/mobile CSF fluid
[normally bright on T2] causing it to appear dark on
FLAIR.
Gradient-echo T2*sequence
Based on the rapid dephasing of stimulated
protons due to the presence of hemoglobin
Intracranial hemorrhage is best detected
results in hypointense (dark) lesions
This sequence has no significant application in the
head and neck.
1. On MRI, what do flow voids represent?
2. For what tumor type is this finding classic?
1- On MRI, what do flow voids represent?
2- For what tumor type is this finding classic?
High velocity blood flow causes stimulated
nuclei to leave the plane before relaxation
MRI signal appears black
This contrast – is best appreciated on
T2 sequences where fluid is normally bright
Key feature appreciated in Paraganglioma
With what sequences can fat
suppression be utilized? What is the
overall purpose of fat suppression?
With what sequences can fat suppression be utilized?
What is the overall purpose of fat suppression?
Fat suppression pulses are used on T1gad and T2 sequences to help subtract the brightness of fat that might be adjacent to a pathologic process
Clinical Correlations:
A small orbital meningioma may not be clearly delineated until the normal periorbital fat is suppressed on a T1gad sequence Prior to suppression the orbit appears all bright, after fat suppression
pulse of the T1 sequence, the periorbital fat is now dark and the meningioma can be identified as the sole bright area of pathology.
T1 gadolinium sequences surveying petrous temporal bone pathology may require fat suppression to identify enhancement that might otherwise by obscured by normal fatty marrow in the petrous bone
What imaging modality is ideal for initial
evaluation of the Temporal Bone?
What imaging modality is ideal for initial
evaluation of the Temporal Bone?
CT best visualizes presence of bone erosion in the bony external auditory canal, the ossicles, the mastoid, tegmen, semicircular canals, and facial nerve canal.
CT best demonstrates temporal bone and skull base fractures
Contrast enhanced CT helps delineate fluid of the inner ear with its surrounding otic capsule and demineralization of the otic capsule in cochlear otosclerosis
CT is useful in diagnosis of congenital anomalies of the cochlea, semicircular canals and vestibular aqueduct
What imaging modality is useful for
early detection of internal auditory
canal tumors and lesions of the
petrous apex?
What imaging modality is useful for early detection of internal
auditory canal tumors and lesions of the petrous apex?
MRI is more useful in detecting small IAC tumors.
CT depends on an expansile lesion in the bony canal
to permit detection and may miss smaller tumors
The variability of petrous apex lesions requires
MRI sequence characteristics to narrow the
differential diagnoses.
Which imaging modality is best for evaluation
of soft tissue tumors of the head and neck?
Both effective in evaluation of soft tissue tumors of the head and neck
Both can define tumor from adjacent fat planes equally well
Both can detect perineural spread by nerve enlargement or violation of adjacent fat planes, but MRI is superior within the skull base and cavernous sinus
CT or MRI can define extent of laryngeal tumors and preepiglottic or paraglottic invasion by distortion of fat planes.
MRI has an advantage in distinguishing tumor from muscle, making MRI more advantageous in evaluation of tumors of the tongue base which lack a fat plane interface
CT has an advantage in defining cortical bone erosion such as in tumors where there is question of mandibular invasion
CT can identify calcifications which may represent chondroid lesions
An 11-year-old boy with left neck mass
Based on the axial CT images, which category of disease is most
likely?
Neoplasm
Trauma
Infection/inflammation
Congenital
reloadme
A 28-year-old man with facial pain and double vision.
1. Select the relevant findings on review of the images (check all that apply)
Mastoiditis
Sphenoid dysplasia
Otitis media
Ossicular erosion
Enlargement of the facial canal
Temporal bone fracture
Enlargement of the foramen ovale.
2. What part of the temporal bone is involved? What disease process does this patient have?
15-year-old boy w/ history of chronic swelling around left eye.
Based on the images
what is the most likely
diagnosis?
A Esthesioneuroblastoma
B Allergic fungal sinusitis
C Juvenile nasal
angiofibroma
D Acute bacterial sinusitis
E Mucocele
Temporal Bone
Squamous
forms lateral wall of middle cranial fossa
Mastoid
Petrous
contains inner ear, internal auditory canal (IAC), petrous apex
Tympanic
forms most of bony external ear
Styloid process
Temporal
Bone:
Is it Normal?
15yo female presents with:
Hemotympanum
EAC laceration
Raccoon eyes
Battle’s sign-what artery?
Facial nerve weakness
What is highest on your differential?
Temporal Bone Fractures – Classify?
Temporal Bone Fracture: What type?
Temporal Bone Fracture: What type?
What deformity?
Acquired or Congenital?
What deformity?
What is your differential diagnosis?
Axial CT
T1 MRI- Noncontrast
How does this case differ?Axial CT
T1 MRI Noncontrast
30 yo male with painful vesiclular ear lesions
and facial paralysis. Diagnosis?
45 yo female w/ chronic sinusitis and
ballotable frontal collection
What complications might you be concerned about?
15 year-old boy with expansile mass
Speckled high attenuation represents what?
Noncontrast CT
See next slide-MRI
MRI
T1
T1
T1
w/
gad
T1
w/ gad
1- Describe the
findings.
2- What is your
differential
diagnosis?
30 year old female presents w/ pale fleshy
nasal mass
T1 Sagittal
T2
T2
See Next Slide
FLAIR DARK T2 BRIGHT
Differential
DIAGNOSIS
T1 T1 w/ Gad T2 FLAIR
Meningo-
encephalocele
Dark Rim
Enhancing/
central dark
Bright Dark
Mucocele Variable
[dept on
inspissated
sec]
Rim
Enhancing/
central dark
Iso/
Bright
Iso/
Bright
Polyp/Sinus
Inflammation
Dark Rim
Enhancing/
central dark
Bright Bright
Neoplasm Iso/
Dark
Homogen.
Enhance-
ment
Bright Bright
Describe the findings.
20 year-old male presents with hearing loss
Based on the MRI findings, what condition might this patient have?
What is the pattern of inheritance?