Download Imaging Findings - lms.manhattan.edu

CT or MRI?
Deciding
What Test
to do.
Acute Cerebral Infarction
• KEY FACTS
• Pathology
• Second most common worldwide cause of death
• Number one cause of US morbidity
• Clinical Issues
• Most common symptom: Focal acute neurologic deficit
• Clinical diagnosis inaccurate in 15-20% of "strokes"
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Imaging Findings
Best diagnostic clue: Diffusion restriction with correlating ADC map
Best imaging tool: MR + T2*, DWI
CT w/o contrast if MR not available
DSA with thrombolysis in selected patients
--57-year-old woman with right cerebral infarct
Stuckey, S. L. et al. Am. J. Roentgenol. 2007;189:913-921
Copyright © 2008 by the American Roentgen Ray Society
Hypertensive Intracranial
Hemorrhage
• If older patient with HTN and high suspicion for hICH,
NECT
• If hyperacute ischemic "stroke" suspected, MR with
T2* and DWI
• If MR shows classic hematoma + co-existing
multifocal "black dots," stop
• If MR shows atypical hematoma, CTA
• If CTA inconclusive, consider DSA
• Protocol advice
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Initial screen = NECT in patients with HTN
Otherwise MRI (include T2* sequences, DWI, +
MRA; T1 C+ optional)
Subdural Hematoma
• Acute (± 6 hrs-3 days) hemorrhagic
collection in subdural space
• NECT initial screen for aSDH
• MRI more sensitive for SDH & additional
findings of traumatic brain injury; most
appropriate in subacute phase
Acute Subdural Hematoma
• Best diagnostic clue: Crescent-shaped,
homogenously hyperdense on CT, extra-axial
collection that spreads diffusely over affected
hemisphere
• May cross sutures, not dural attachments
• May extend along falx & tentorium
• Compresses & displaces underlying brain
• Recurrent, mixed-age hemorrhage common → in
a child raises suspicion of nonaccidental trauma!
• CT density & MR signal intensity vary with age &
organization of hemorrhage
Figure 2d. Complication associated with subdural hematoma
Kiyosue, H. et al. Radiographics 2004;24:1637-1653
Copyright ©Radiological Society of North America, 2004
Cerebral Contusion
• Injury to brain surfaces involving superficial gray matter
• Best imaging tool: MR > CT in detecting presence, delineating extent
of lesions
• Imaging Findings
• Best diagnostic clue: Patchy superficial hemorrhages within
edematous background
• Occur in characteristic locations where brain is adjacent to bony
protuberance or dural fold
• Focal contusions may also occur at site of depressed skull fracture
• FLAIR best demonstrates hyperintense cortical edema
• FLAIR may show hyperintense SAH
• Acute: Hypointense hemorrhagic foci "bloom" on GRE (often not
seen on other sequences)
Aneurysmal Subarachnoid
Hemorrhage
• Best imaging tool: NECT + multislice CTA
• Best diagnostic clue: Hyperdense CSF on NECT
• Imaging Findings
• Location: Interhemispheric SAH suggests ACoA
aneurysm, sylvian correlates with MCA
• Pathology
• Most common cause of SAH is trauma (not aneurysm
rupture)
• aSAH causes 5% of "strokes"
• 85% of nontraumatic SAH caused by ruptured
aneurysm
Figure 4a: (a, c) Unenhanced CT images obtained in two patients with SAH
Waaijer, A. et al. Radiology 2007;242:832-839
Copyright ©Radiological Society of North America, 2007
Brain Metastases
• Best imaging tool: Contrast-enhanced MRI > > CECT
• Imaging Findings
• Best diagnostic clue: Discrete parenchymal mass(es) at gray-white interface
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Pathology
Prevalence of metastases vs primary CNS neoplasms increasing
Now account for up to 50% of all brain tumors
Seen in 25% of cancer patients at autopsy
• Clinical Issues
• Median survival with whole brain XRT = 3-6 months
• Diagnostic Checklist
• Use contrast-enhanced scans
Solitary Pulmonary Nodule
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KEY FACTS
Terminology
Round or oval opacity, < 3 cm in diameter
Imaging Findings
< 3 cm; > 90% of nodules < 2 cm are benign
Nodules approaching 3 cm, more likely to be malignant
Prior radiographs critical for nodule detection
Benign calcification: Central nidus, laminated, popcorn, diffuse
Hamartomas, 1/3 show popcorn calcification
Growth: Much overlap between benign and malignant nodules
Mixed solid/part solid, up to 50% < 1.5 cm in diameter are malignant
Pathology
90% represent (in order) granuloma, bronchogenic carcinoma, hamartoma, solitary metastasis,
carcinoid
Imaging Recommendations
Best imaging tool
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CT with sequential thin cuts for presence of calcification or fat
PET for nodules with high likelihood for malignancy
MIP increases conspicuity for nodules
Biliary System
• Best imaging tool
• Helical NE + CECT, MR + MRCP
--48-year-old woman with liver disease
Yu, J. et al. Am. J. Roentgenol. 2006;187:1544-1553
Copyright © 2006 by the American Roentgen Ray Society
Hepatic Neoplasm (primary and
metastatic)
• Imaging Recommendations
• Multiphase CT (NE, arterial, venous,
delayed phases) or CEMR.
Adrenal Adenoma
• Imaging Findings
• Best diagnostic clue: Well-circumscribed, low density, small adrenal mass
on CT
• Homogeneous soft tissue mass of 0-20 HU
• Washout of adenoma: 10 min. post injection > 50%
• T1WI out of phase: ↑ Signal "drop-out" (lipid-rich)
• Washout value of > 50%: Sensitivity (96%), specificity (near 100%) for
adrenal adenoma
• Washout value of < 50%: Indicative of either metastases or an atypical
adenoma
• Clinical Issues
• Asymptomatic incidental CT imaging finding
• Conn syndrome: Hypertension & weakness
• Cushing syndrome: Moon facies, truncal obesity, purple striae & buffalo
hump
• Diagnosis: Clinical, biochemical, imaging, histology
Adrenal Adenoma
• CT is study of choice to confirm the diagnosis of
adrenal adenoma
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CT technique: Thin cuts
• If suspect adrenal adenoma, NECT alone
sufficient
• If CECT done, assess the following
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If lesion < 37 HU on CECT, call it adenoma
If lesion > 37 HU, on CECT, get 10 min delayed scan
to determine washout
• MR with in and out of phase imaging
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Diagnostic for lipid-rich adenomas
Renal Cell Carcinoma
• Best imaging tool
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Multiphase CT Diagnosis and staging
MR: Staging is equal or better than CT (can do
subtraction images)
• Protocol advice
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Multiphase CT
 Mandatory: Nonenhanced and parenchymal phase
(≥ 80 sec delay); optional corticomedullary (60
sec), excretory (2-5 min delay)
Figure 1. Transverse MR images in 52-year-old woman with bilateral renal masses
Hecht, E. M. et al. Radiology 2004;232:373-378
Copyright ©Radiological Society of North America, 2004
Increased Radiation
Exposure from Medical
Procedures
More than 62 million CT scans are now performed
annually in the U.S. By comparison, roughly 3 million
scans were performed in 1980.
New England Journal of Medicine for November 29, Drs. David J. Brenner
and Eric J. Hall
• This increase in CT usage is largely
responsible for the near doubling of the
average personal radiation exposure that
occurred during the same period.
• One estimate is that in the future up to 2%
of all malignancies in the U.S. could be
due to radiation from CT scans. New
England Journal of Medicine [1],
November 29, 2007,
• Reduce the CT-related radiation dose at
the patient level.
• Replace CT evaluation with assessment
by nonradiation imaging modalities, such
as MRI and ultrasound, when feasible.
• Reduce the total number of CT scans
performed.
• An effective radiation of dose of 10 mSv
can cause an increase in the lifetime
cancer risk in one in 2,000 patients.
Radiation Dose
• CT Abd. - 10 mSv (3 yrs of background
radiation)
• CT Chest - 8 mSv
• Chest x-ray - 0.1 mSv (10 days of
background radiation)
What can we do?
ALARA
• acronym for an important principle in
radiation protection and stands for "As
Low As Reasonably Achievable".
• ACR appropriateness criteria
• http://acsearch.acr.org/
• or go to acr.org and search site for
“appropriateness criteria”
Some examples
• Perform multiphase CT’s only when
needed.
• CT with and without contrast is not
needed most of the time.
• i.e. Chest CT for lung nodule, most
abdominal CT’s, most head CT’s.