Download Ring Enhancing Lesions in a Patient with AIDS

Jonathan Waks, MSIII
Gillian Lieberman, MD
March 2007
Ring Enhancing Lesions in a
Patient with AIDS
Jonathan Waks, Harvard Medical School Year III
Gillian Lieberman, MD
Jonathan Waks, MSIII
Gillian Lieberman, MD
Agenda
•
•
•
•
•
•
Background: CNS complications of AIDS
Patient presentation
Menu of radiologic tests
Differential diagnosis: ring enhancing lesions
Differentiating CNS lesions
Summary
2
Jonathan Waks, MSIII
Gillian Lieberman, MD
AIDS and the CNS
• 10% of patients have neurological signs and symptoms
when they first present with AIDS.
• 30-60% of patients with AIDS will develop neurological
complications during the course of their illness.
• 70-90% of patients with AIDS show CNS involvement at
autopsy.
Understanding and recognizing the appearance of
CNS complications in patients with AIDS is
important in promptly recognizing, diagnosing and
initiating proper treatment.
Thurnher MM. Eur Radiol 1997;7(7):1091-7
3
Jonathan Waks, MSIII
Gillian Lieberman, MD
DDx. of CNS complications of AIDS:
1.
2.
HIV encephalitis
Opportunistic Infections:
•
•
•
•
•
•
•
3.
Toxoplasmosis
Cryptococcosis
CMV
TB
PML (JC virus)
Bacterial
Fungal
Neoplasm
•
•
HIV-1 Virus
http://www.niaid.nih.gov/factsheets/howhiv.htm
Primary CNS lymphoma
Kaposis Sarcoma
Thurnher MM. Eur Radiol 1997;7(7):1091-7
4
Jonathan Waks, MSIII
Gillian Lieberman, MD
Index Patient – “JL”
• 49 year old man with AIDS (last CD4=17, on
HAART) who presented to an OSH for unsteady
gait, lower extremity weakness, headache, vomiting,
dysarthria and seizures.
• PE:
– Temp: 102.4ºF
– Multiple CN deficits
• Head CT showed multiple ring enhancing lesions
• Started on broad spectrum antibiotics with coverage
for toxoplasma.
• No improvement Æ Brain biopsy: non diagnostic
• Transferred to BIDMC for further management.
5
Jonathan Waks, MSIII
Gillian Lieberman, MD
Before we discuss the imaging that
was obtained when JL arrived at
BIDMC, let’s first review the radiologic
modalities that can be used to
evaluate the CNS in a patient with
AIDS.
6
Jonathan Waks, MSIII
Gillian Lieberman, MD
Menu of Radiologic Tests
Primary Modalities:
• CT (w/wo contrast)
• MRI (w/wo contrast)
– T1, T2, FLAIR
– DWI/ADC Maps
Adjunctive Modalities:
• FDG-PET
• Thallium 201 SPECT
• Special MRI protocols
– MR Spectroscopy
– Perfusion MR
http://www.southernhealth.org.au/imaging/images/mr_ge.jpg
7
Jonathan Waks, MSIII
Gillian Lieberman, MD
Menu of Radiologic Tests
Primary Modalities:
• CT (w/wo contrast)
• MRI (w/wo contrast)
– T1, T2, FLAIR
– DWI/ADC Maps
Adjunctive Modalities:
• FDG-PET
• Thallium 201 SPECT
• Special MRI protocols
– MR Spectroscopy
– Perfusion MR
These adjunctive modalities are
not used in the routine imaging or
evaluation of CNS lesions in
patients with AIDS. They are
primarily used when the identity
of a lesion is in question and
additional non-invasive imaging
would potentially alter treatment.
PET and SPECT scanning are
used most frequently. MR
spectroscopy and perfusion MR
are not routinely used and will not
be discussed in this presentation.
Adjunctive imaging modalities will be
discussed later on in the presentation
8
Jonathan Waks, MSIII
Gillian Lieberman, MD
Menu of Radiologic Tests
Computed Tomography:
Pros
Cons
1. Fast
1. Less sensitive than MRI
2. Readily available
2. Limited evaluation of
posterior fossa
3. Can scan people with
contraindications to MRI
3. Can miss some white
matter disease
4. Brain radiation
Normal Head CT
BIDMC, PACS
9
Jonathan Waks, MSIII
Gillian Lieberman, MD
Menu of Radiologic Tests
Magnetic Resonance Imaging:
Pros
Cons
1. Better than CT at determining if a
lesion truly is solitary
1. More costly, less readily
available
2. Increased sensitivity to subtle white
matter disease and posterior fossa
lesions
** MRI is the BEST test to
assess CNS lesions
3. May be able to identify small
peripheral lesions missed by CT that
are more accessible for biopsy
4. No radiation
5. Multiple imaging sequences can aid
diagnosis (DWI/ADC/FLAIR)
Normal T1 and T2 MRI
BIDMC, PACS
10
Jonathan Waks, MSIII
Gillian Lieberman, MD
Diffusion Weighted Imaging (MRI)
Diffusion Weighted Imaging (DWI): Makes use of Brownian motion to
image local water diffusion. Macromolcules and cells in the brain
restrict the diffusion of water.
Areas of restricted diffusion appear BRIGHT on DWI
Apparent Diffusion Coefficient (ADC): The signal intensity of DWI
depends on factors other than diffusion information (spin density,
TR, TE). By combining multiple DWIs, these other factors can be
eliminated. ADC also eliminates “T2-Shine through” on DWI caused
by intense T2 signals.
Areas of restricted diffusion appear DARK in ADC
Images from Fillipi. Clinical MR Neuroimaging. pg 411
Information from Stadnik et al. http://ej.rsna.org/ej3/0095-98.fin/index.htm
11
Jonathan Waks, MSIII
Gillian Lieberman, MD
Imaging: “JL”
Axial T1WI MRI
pre gadolinium
=
Multiple ring enhancing
Lesions throughout CNS
Axial T1WI MRI
post gadolinium
Images provided by Mizuki Nishino, MD; BIDMC
12
Jonathan Waks, MSIII
Gillian Lieberman, MD
Looking at additional MRI sequences
allows us to better characterize the
center of the lesion and surrounding
tissue.
13
Jonathan Waks, MSIII
Gillian Lieberman, MD
Imaging: “JL”
Axial
T1 MRI +Gad
Hypo/isointense lesion
with ring enhancement
Axial
DWI MRI
Hyperintense on DWI =
restricted diffusion
Images provided by Mizuki Nishino, MD; BIDMC, PACS
Axial
FLAIR MRI +Gad
Enhancing lesion
surrounded by
hyperintense edema
Axial
ADC Map
Hypointense on ADC =
restricted diffusion
14
Jonathan Waks, MSIII
Gillian Lieberman, MD
There is a well defined differential
diagnosis for ring enhancing lesions
in the CNS:
15
Jonathan Waks, MSIII
Gillian Lieberman, MD
DDx. Ring Enhancing Lesions (*)
•Infection:
Head T1WI w/ contrast
Head CT with contrast
•Toxoplasma
•Cystercercosis
*
•Brain abscess (bacterial, fungal)
•Neoplasms
*
•Brain tumors/metastases
•Primary CNS Lymphoma
•Demyelinating Disease
Head CT with contrast
•MS
•ADEM
•Vascular lesions
•Resolving infarction
*
*
•Hematoma
•Thrombosed aneursm
•Radiation necrosis
•Postoperative changes
Gamuts in Radiology, online edition
Images from Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66. 16
Jonathan Waks, MSIII
Gillian Lieberman, MD
DDx. Ring Enhancing Lesions (*)
•Infection:
Head T1WI w/ contrast
Head CT with contrast
•Toxoplasma
•Cystercercosis
*
•Brain abscess (bacterial, fungal)
•Neoplasms
*
•Brain tumors/metastases
•Primary CNS Lymphoma
•Demyelinating Disease
Head CT with contrast
•MS
When we consider which of these
•ADEM
entities are
common in patients with
AIDS•Vascular
(see slide
4 for a refresher),
lesions
the differential narrows, and we can
•Resolving infarction
focus on Toxoplasmosis, brain
•Hematoma
abscess and
primary CNS lymphoma
*
*
•Thrombosed aneursm
•Radiation necrosis
•Postoperative changes
Gamuts in Radiology, online edition
Images from Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66. 17
Jonathan Waks, MSIII
Gillian Lieberman, MD
We will now explore the narrowed
differential in more detail.
1. Toxoplasmosis
2. Primary CNS Lymphoma
3. Bacterial brain abscess
18
Jonathan Waks, MSIII
Gillian Lieberman, MD
Image from http://cal.vet.upenn.edu/paraav/images/10-43.jpg
Toxoplasmosis: Background
Micrograph of T. gondii
•
•
Intracellular protazoan parasite, toxoplasma gondii
Most common opportunistic infection in HIV (CD4 < 100 per μL)
•
Symptoms are usually secondary to reactivation of latent infection
•
Signs/Symptoms: headache, fever, seizures, encephalopathy,
altered mental status, neuro. deficits
•
Important to quickly diagnose because very treatable with antibiotics
•
Toxoplasma antibody is not always useful1
•
•
Only 1/3 cases have rise in IgG
Only 1/2 produce antibodies in CSF
•
CSF PCR lacks sensitivity and specificity1
•
Response to treatment is the main method of arriving at a definitive
diagnosis.
•
Treatment: Pyrimethamine and sulfadiazine or clindamycin
Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
1. Fillipi. Clinical MR Neuroimaging, pg 420.
19
Jonathan Waks, MSIII
Gillian Lieberman, MD
Toxoplasmosis: Life cycle
Cats are the main reservoirs of infection and
become infected by ingesting tissue cysts.
The cysts reproduce inside the feline
intestinal tract.
Oocysts are shed in fecal matter and are
extremely resistant to severe environmental
conditions and disinfectants.
Humans become infected by either:
•Eating tissue cysts in undercooked meat
•Fecal-oral transmission from cat feces
•Blood or organ transplantation
•Transplacentally
Approximately 22.5% of people in the United
States are infected.
Image and information from http://www.dpd.cdc.gov/dpdx/HTML/Toxoplasmosis.htm
20
Jonathan Waks, MSIII
Gillian Lieberman, MD
Toxoplasmosis: Sites of Infection
• Most common sites of
infection are:
– Cortico-medullary junction
– Basal ganglia
– Thalamus
Image from Netter, 2004, plate 104.
Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
21
Jonathan Waks, MSIII
Gillian Lieberman, MD
Toxoplasmosis: Imaging
• CT:
– Non-contrast: isodense to gray matter, but can be detected
secondary to possible edema and mass effect
– May be hyperdense if hemorrhagic
– Contrast: 90% Ring-enhancement1 with is secondary to
inflammatory response (patients with decimated immune
systems may not show enhancement)2
– After treatment, can show areas of calcification
1. Koralnik, UpToDate
2. Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
22
Jonathan Waks, MSIII
Gillian Lieberman, MD
Toxoplasmosis: Imaging
• MRI:
– Usually shows more lesions than CT
– T1WI: hypointense or isointense to gray
matter
– T2WI/FLAIR: isointense or hyperintense to
gray matter
– ring enhancing, sometimes with a central
focus of enhancement “target sign”.
Zimmerman, RD. Clinical MR Neuroimaging. pg 365
23
Images from Thurnher MM. Eur Radiol 1997;7(7):1091-7
Jonathan Waks, MSIII
Gillian Lieberman, MD
Toxoplasmosis Lesions
Below are 2 patients with CNS lesions that were
subsequently shown to be toxoplasmosis.
Patient 2
Patient 1
Head CT w/ contrast
Hypodense, ring
enhancing lesion and
surrounding edema
T2 MRI, non-contrast
T1 MRI w/ contrast
Hyperintense,
enhancing lesion
Hypointense, ring
enhancing lesion
24
Jonathan Waks, MSIII
Gillian Lieberman, MD
Primary CNS Lymphoma: Background
• Most common AIDS related neoplasm (2-5% patients)
• After Toxoplasmosis, is second most common cerebral mass
lesion in AIDS patients.
• Almost always of B-cell, Non-Hodgkins type
• Likely related to EBV
• Presenting symptoms: neurological deficits, encephalopathy,
seizure (similar to toxoplasmosis)
• Median survival < 1 year
• Treatment: Radiation and corticosteroids
Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
25
Jonathan Waks, MSIII
Gillian Lieberman, MD
Primary CNS Lymphoma: Sites of Infection
•
Most commonly located in:
– periventricular/periependymal
white matter
– corpus callosum
Illustrations from Netter, 2004, Plates 100, 104.
Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
BIDMC, PACS
26
Jonathan Waks, MSIII
Gillian Lieberman, MD
Primary CNS Lymphoma: Imaging
• CT:
– Isodense to Hypodense
• MR:
– T1: hypointense
– T2/FLAIR: isointense to hyperintense
– Enhancement: usually irregular enhancement
or ring enhancement.
Doweiko, UpToDate
Chang. Clinical MR Neuroimaging. pg 466
27
Jonathan Waks, MSIII
Gillian Lieberman, MD
Primary CNS Lymphoma can have a
wide range of appearances:
28
Jonathan Waks, MSIII
Gillian Lieberman, MD
Primary CNS Lymphoma: Varying Lesions
2 different patients with lesions subsequently shown to be primary CNS lymphoma
Patient 3
T1WI +Gad.
Hypointense lesion with
ring enhancement
Left image from Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
Patient 4
T1WI +Gad.
Homogenously
enhancing lesion
Right Image from Doweiko, UpToDate
29
Jonathan Waks, MSIII
Gillian Lieberman, MD
Bacterial Abscess: Background
• Often presents with headache, altered mental
status, nausea, vomiting, seizures, neuro. deficits
due to expanding mass.1
• Hypointense on T1, Hyperintense on T21
• Capsule is hypointense on T21
• Ring enhancing with surrounding edema1
• Less common in AIDS patients than toxoplasmosis
or primary CNS lymphoma2
– Often associated with bacteremia
1. Fillipi, Clinical MR Neuroimaging. Pg 409
2. Koralnik, UpToDate
30
Jonathan Waks, MSIII
Gillian Lieberman, MD
Bacterial Abscess: Imaging
T1 MRI, no contrast
Hypointense lesion with
surrounding edema
T2 MRI w/ contrast
T1 MRI +Gad
Enhancing lesion with
hypointense capsule and
surrounding edema
Ring enhancing lesion with
surrounding edema
Images from Zimmerman, RD. Clinical MR Neuroimaging. pg 355
31
Jonathan Waks, MSIII
Gillian Lieberman, MD
Lymphoma vs. Toxoplasmosis
Toxoplasmosis and primary CNS lymphoma are the two most common
brain lesions in patients with AIDS, but, as has been shown, both can
have very similar clinical features and appearance on CT and MRI.
The definitive diagnosis is usually provided by brain biopsy, but biopsy
is not a benign procedures and is associated with possible morbidity
and mortality. (8.4% morbidity, 2.9% mortality)1
Delay in diagnosis while waiting to see if a patient responds to initial
therapy is a significant problem:2
• lesions can rapidly progress.
• unnecessary therapies are associated with unnecessary toxicity.
• Incorrect initial treatment may result in a biopsy that could have
potentially been prevented.
1. Doweiko, UpToDate
2. Fillipi, Clinical MR Neuroimaging. Pg 420
32
Jonathan Waks, MSIII
Gillian Lieberman, MD
Lymphoma vs. Toxoplasmosis: Patient 5
The lesion has significantly
increased in size over 2 weeks
Contrast head CT of a 38 year old woman with
AIDS and a ring-enhancing lesion presumed to
be toxoplasmosis
Images from Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
Same patient’s contrast head CT after 2
weeks of anti-Toxo antibiotics and no
improvement. Biopsy 2 days later
confirmed primary CNS lymphoma
33
Jonathan Waks, MSIII
Gillian Lieberman, MD
The appearance of a CNS lesion
may give clues as to the diagnosis:
34
Jonathan Waks, MSIII
Gillian Lieberman, MD
Lymphoma vs. Toxoplasmosis: Features
Favors Lymphoma
Favors Toxoplasma
1. Large lesion size (>4 cm)
1. Large number of lesions
2. Extensive white matter
involvement
2. Involvement of basal
ganglia
3. Periventricular location/
subependymal spread
3. Hemorrhagic lesions
4. Contrast enhancement along
ventricular surface
5. Extension across or
involvement of corpus
callosum
Provenzale JM, Radiol Clin North Am 1997;35(5):1127-66.
4. Responds to anti-Toxo
drugs, usually within 7-14
days
BUT in practice, these
features are unreliable in
making the correct diagnosis
35
Jonathan Waks, MSIII
Gillian Lieberman, MD
Diffusion Weighted Imaging is one
specific application of MRI that has
attempted to distinguish ring-enhancing
lesions:
36
Jonathan Waks, MSIII
Gillian Lieberman, MD
Diffusion Weighted Imaging
Can Diffusion Weighted Imaging be used to differentiate toxoplasmosis
from CNS lymphoma?
Data is inconsistent.
In general:1
* Toxoplasmosis tends to be hyperintense on DWI and hypointense on ADC
This corresponds with RESTRICTED DIFFUSION
* CNS lymphoma tends to be hypointense on DWI and hyperintense on ADC
This corresponds with INCREASED DIFFUSION
BUT, there is a broad, overlapping range of diffusion values for both lesions,
and both conditions can show either increased or restricted diffusion. As of now,
DWI/ADC cannot accurately distinguish toxoplasmosis from CNS lymphoma.
DWI/ADC is useful for identifying pyogenic abscesses which are more
consistently hyperintense on DWI and hypointense on ADC (restricted diffusion)
1. Fillipi. Clinical MR Neuroimaging pg 408-420
37
Jonathan Waks, MSIII
Gillian Lieberman, MD
Diffusion Weighted Imaging: Examples
Patient 6:
proven Bacterial Abscess
Surrounding edema
Patient 7:
proven Toxoplasmosis
DWI
DWI
ADC
Hyperintense
Hypointense
Restricted Diffusion
Images from Zimmerman. Clinical MR Neuroimaging pg 355, 366
Lesion does NOT
show restricted
diffusion in the center
Hyperintense lesion with
restricted diffusion
Toxo. does not consistently show restricted
diffusion, even in the same patient!
38
Jonathan Waks, MSIII
Gillian Lieberman, MD
Lymphoma vs. Toxoplasmosis
Nuclear medicine offers other methods for differentiating
between infectious and neoplastic lesions
FDG-PET scan
Image from http://upload.wikimedia.org/wikipedia/commons/c/c6/PET-image.jpg
Thallium 201 SPECT
39
Jonathan Waks, MSIII
Gillian Lieberman, MD
FDG-Positron Emission Tomography
Patients are given trace amounts of FDG ([18F]
2-Fluoro-2-Deoxy-D-Glucose), a radioactive
form of glucose that enters and becomes trapped
in metabolically active cells. The concentration
of FDG in tissue is directly proportional to its
metabolic activity
FDG undergoes β-decay
β-particles collide with electrons after traveling
only a few mm. The collision produces 2
gamma rays which are detected and produce
part of an image.
http://www.biomedpet.org/howitworks.cfm
Image from http://www.scq.ubc.ca/?p=474
40
Jonathan Waks, MSIII
Gillian Lieberman, MD
FDG-Positron Emission Tomography
FDG-PET can distinguish infectious lesions from neoplastic lesions
Toxoplasmosis/other infections:
Lymphoma:
LOW metabolic activity
HIGH metabolic activity
T1 + Gad
FDG-PET
Lesion is hypometabolic on FDG-PET
Images from Love C, Radiographics 2005;25(5):1357-68.
T1 + Gad
FDG-PET
Lesion is hypermetabolic on FDG-PET
41
Jonathan Waks, MSIII
Gillian Lieberman, MD
Thallium 201 SPECT
PET scanning is not widely available and is more expensive than SPECT (Single Photon Emission
Computed Tomography) because the isotopes used in PET scanning have short half-lives.
201Tl
behaves like K+ and enters living cells via the Na+/K+ ATPase. It does not accumulate in
necrotic/dead tissue and thus provides another method of potentially differentiating neoplastic
from infectious lesions
201Tl
decays via the production of single photons which can be detected and imaged.
Patient 8:
T1 MRI of the brain
shows an
inhomogeneously
enhancing lesion
later shown to be
CNS lymphoma at
biopsy
Images from Antinori A, J Clin Oncol 1999;17(2):554-60.
201Tl
SPECT scan
shows a focal area
of thallium uptake
corresponding to the
neoplastic lesion
42
Jonathan Waks, MSIII
Gillian Lieberman, MD
Patient “JL” -- Follow-up
• Brain biopsy at OSH was not diagnostic:
– Few WBC
– No bacteria/organisms via Gram stain or culture
– No signs of lymphoma.
• Toxo antibodies negative
• Toxo PCR of CSF negative
• EBV PCR of CSF negative
• Found to have multiple abscesses throughout
body and later found to be bacteremic
43
Jonathan Waks, MSIII
Gillian Lieberman, MD
Patient “JL” -- Follow-up
• Widespread bacterial infection and restricted diffusion on
DWI/ADC suggested abscess.
• Restarted on broader spectrum antibiotics to cover
bacteria and toxoplasmosis.
• CNS lesions began to decrease in size
• Diagnosis: favored bacterial abscess, although
toxoplasmosis could not be ruled out
BIDMC, PACS
44
Jonathan Waks, MSIII
Gillian Lieberman, MD
Patient “JL”: Imaging over the course of 2 months of treatment
Time
Admission
T1 MRI
w/ Gad
s/p treatment
for 1 month
T1 MRI
w/ Gad
s/p treatment
for 2 months
T1 MRI
w/ Gad
BIDMC, PACS
45
Jonathan Waks, MSIII
Gillian Lieberman, MD
Summary
• CNS complications are extremely common in patients
with AIDS.
• The 2 most common CNS lesions in AIDS patients are
toxoplasmosis and primary CNS lymphoma.
• Lesions are often treated empirically, but delay in
definitive diagnosis can have significant consequences.
• MRI and nuclear medicine offer non-invasive methods to
facilitate the identification of CNS lesions without
invasive biopsy
46
Jonathan Waks, MSIII
Gillian Lieberman, MD
References
1.
Antinori A, De Rossi G, Ammassari A, et al. Value of combined approach with thallium-201 single-photon emission computed tomography
and Epstein-Barr virus DNA polymerase chain reaction in CSF for the diagnosis of AIDS-related primary CNS lymphoma. J Clin Oncol
1999;17(2):554-60.
2.
Chang, Linda and Thomas Ernst. “Physciological MR to evaluate HIV-associated brain disorders.” Clinical MR Neuroimaging. Ed.
Jonathan Gillard et al. Cambridge: Cambridge University Press, 2005. 460-478.
3.
Doweiko JP, Groopman JE. “AIDS-related lymphomas: Primary central nervous system lymphoma”. UpToDate. www.uptodate.com
Accessed 3/14/07
4.
Fillipi, Christopher G. “The role of diffusion-weighted imaging in intracranial infection.” Clinical MR Neuroimaging. Ed. Jonathan Gillard et
al. Cambridge: Cambridge University Press, 2005. 408-428.
5.
“Gamut A-61 Ring-enhancing Lesion on CT or MRI.” Reeder And Felson's Gamuts In Radiology. Ed. Maurice Reeder. New
York: Springer, 2003. Accessed electronically.
6.
“How does PET work?” PET Imaging Center 2005. http://www.biomedpet.org/howitworks.cfm. Accessed 3/18/07.
7.
Koralnik, IJ, “Approach to HIV-Infected patients with central nervous system lesions”. UpToDate. www.uptodate.com Accessed 3/14/07
8.
Love, C et al. FDG PET of infection and inflammation. Radiographics. 2005; 25, 5: 1357-1367.
9.
Netter, Frank H. Atlas of Human Anatomy, 3rd Edition. Teterboro: Icon Learning Systems, 2004.
10.
Provenzale JM, Jinkins JR. Brain and spine imaging findings in AIDS patients. Radiol Clin North Am. 1997 Sep;35(5):1127-66.
11.
Stadnik, Tadeusz et al. “Diffusion imaging: from basic physics to practical imaging” 1998 RSNA Scientific Assembly.
http://ej.rsna.org/ej3/0095-98.fin/index.htm. Accessed on 3/16/07.
12.
Thurnher MM, Thurnher SA, Schindler E. CNS involvement in AIDS: spectrum of CT and MR findings. Eur Radiol 1997;7(7):1091-7.
13.
“Toxoplasmosis”. Laboratory Identification of Parasites of Public Health Concern.
http://www.dpd.cdc.gov/dpdx/HTML/Toxoplasmosis.htm. Accessed on 3/18/07.
14.
Zimmerman, Robert D. “Physiological imaging in infection, inflammation and demyelination: overview.” Clinical MR Neuroimaging. Ed.
47
Jonathan Gillard et al. Cambridge: Cambridge University Press, 2005. 353-379.
Jonathan Waks, MSIII
Gillian Lieberman, MD
Acknowledgements:
Mizuki Nishino, MD
Gillian Lieberman, MD
Pamela Lepkowski
Larry Barbaras, Webmaster
48