CT Detection
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VICTOR
of Demyelinated
M. HAUGHTON,’
KHANG-CHENG
Plaques HO,2 ALAN
CT images and anatomic slices of two brains containing numerous demyelinated plaques were correlated. Demyelinated plaques smaller than 0.7 cm were not detected by CT. Some larger plaques were misinterpreted as normal structures. These and other considerations suggest that chronic cerebral demyelination cannot be excluded by negative nonenhanced CT scan.
too
the radiologist factors
affect
correlated cadavers
for
resolution,
reviewing
the images.
CT detection
53226.
of Radiology, Address
To determine
reprint
College
requests
2Department
of Pathology, February
1979
Medical
Roentgen
Ray Society
November of Wisconsin
brains
multiple
of
0.
and
were
removed
and
container
or container
filled
with
holder
of
a clinical immediately
physiologic
was extracted
head
ELDEVIK’
Methods with
the brain
the
PETTER
cadavers
polyethylene in
Sclerosis
two
sclerosis
placed
a
saline.
diagnosis placed Air
(12] and the container General
scanner. Consecutive CT sections were parallel to the base of the brain. Technical mm cut thickness, 9.6 sec scan time, 600 radiologists studied the display console and tried to identify the location and size
Electric
CT/T
of in a within
was 8800
made at 5 mm intervals factors included a 5 mA, and 120 Ky. Three and hard copy images, of any low attenuation
abnormality.
The brains were subsequently fixed and sectioned with an electric slicer into 5 mm thick axial sections parallel to the base of the brain. The pathologist then identified the location and size of each demyelinated plaque visible on the surface of the sections and the pathologically identified lesions were correlated with those identified radiographically. To compare these
what we
from
AND
Materials
by
plaques,
in brains
after revision
Medical
AJR 132:213-215,
1979 American
recognized
of demyeiinated
July 25, 1978; accepted
‘Department
©
or not
CT and anatomic findings with multiple sclerosis.
Received Wisconsin
small
L. WILLIAMS,’
The
Computed tomography (CT) demonstrates focal abnormalities in one-third of patients with clinically diagnosed multiple sclerosis [1-11]. in two-thirds of these patients, cerebral demyelinated plaques are either not present, isodense,
in Multiple
two
6, 1978. and
Milwaukee
County
Medical
Complex,
8700
West
Wisconsin
Avenue,
Milwaukee,
to V. M. Haughton.
College
of Wisconsin
and Milwaukee
County
213
Medical
Complex,
Milwaukee,
Wisconsin
53226.
o361-8o3x/79/i322-o213
$0.00
214
HAUGHTON TABLE CT-Detected Lesion
Brain
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TABLE Attenuation
Plaques
Location
Detection
Paraventricular
2.1 xO.7 1.5x0.9
3.0 x 0.8 1.2x0.6
3.2xi.6 2.1 xO.5 1.7x0.6 1 .6 x 1 .1
i.2x0.4 i.2x0.2
.
2 (of 39 lesions): x 0.7 x 0.3 x 0.6
Number
plaques
of
detected
observations
AJR:132,
1979
2
in Brain
No. 1
Attenuation No.
-
February
SD
Area (cm’)
27.2 23.6
2.4 2.8
0.30 0.44
43.8 45.0
3.8 2.6
0.43 0.39
34.8 35.8
2.4 2.4
1.68 1.47
31 lesions):
2.8 x 0.6
Brain 0.6 0.7 1 .4
AL.
1
Demyelinated
Size (cm)
1 (of
ET
radiologists
Epiventricular Paraventricular Subcortical (of
retrospectively
with
three)
who
detected
3 3
Lesion: Area 1
3 2 2 A A A A A A
Area2
Gray matter: Areal Area2 White matter: Areai Area2
3
2 demyelinated
plaques
or
to
(R)
in vivo
imaging,
demyeiinated plaques in the patients with presumed multiple a region-of-interest cursor.
attenuation
cadaver sclerosis
brain were
numbers
images
of the
and
measured
in
with
Results in the first brain, 31 demyeiinated plaques were found (table 1). Five of these plaques, all larger than 1.0 cm, were initially detected by one or more of the radiologists. Six additional lesions 1 .6-3.2 cm in greatest diameter and located immediately adjacent to the ventricle, were detected only after the anatomic specimens and the CT images were compared (fig. 1). The remaining 20 lesions, 0.2-1 .6 cm in greatest diameter, were not detected prospectively or retrospectively. All lesions in this brain were paraventniculan (near the ventricle) or epiventnicuiar coven the ventricle). In the second brain, 39 demyeiinated found on pathologic examination. Only plaques, 0.6-1 .4 cm in greatest in the CT images (table 1). The
diameter,
Fig. 2.-Two white matter, in
were
contrast
coefficients
were
mea-
detected
Fig.
3.-Attenuation
in periventricular
lesions (arrows) measured 16-23 units presumed disseminated sclerosis.
CT-detected abnormalities in multiple sclerosis patients include: (1) nonspecific findings such as atrophy [1, 3, 9]; (2) transient focal contrast-enhancing or lowdensity lesions [2, 5, 6, 8-10]; and (3) chronic low without
attenuation
plaques were three of these
Discussion
lesions
average
sured.
other 36 lesions, all less than 1 cm in diameter, were missed by CT scanning both prospectively and retrospectively. Of the 39 plaques in brain 2, 36 were panaventnicu Ian. Pathologic examination showed the plaques in both brains to be old, except for two plaques that were undergoing organization. The two largest demyeIinated plaques in the first brain had average attenuation numbers of 27.2 and 23.6 units (table 2, fig. 2). A living patient with multiple sclerosis (fig. 3) had plaques measuning 16-25 units. Attenuation of white matter in cadaver brains averaged 35.3 units compared to 32.6 units in the living patient with multiple sclerosis.
attenuation
which
regions of gray matter, two regions of and two regions of demyelinated plaque
enhancement
[3,
5,
11].
The
third
abnormality,
presumably
low
density
in patient
an
with
organized
demyelinated plaque, is the subject of this study. The Resolving capacity of the scanner affects detection of small low-contrast lesions, such as demyelinated
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AJR:132,
February
CT
1979
OF
PLAQUES
IN MULTIPLE
plaques. A 3 mm diameter cylindrical phantom differing by 5 units from the surrounding substance may be detected in a CT/T 8800 tomognaphic slice obtained perpendicular to the cylinder [13]. However, a 3 mm chronic demyelinated plaque differing from cerebral white matter by 5 units is not distinguished in the same scanner. in fact, plaques smaller than 7 mm were not detected in vitro. These undetected demyelinated plaques are probably hypodense (since their pathologic and histologic appearance is identical to the larger hypodense plaques), yet presumably they are not detected by CT because of irregular, rounded margins that result in partial volume averaging. Whether xenon contrast enhancement of cerebral white matter permits more accurate detection of these plaques is under investigation
[14,
15]).
Plaques larger than 7 mm are sometimes disregarded on a CT scan if they simulate normal structures. Paraventnicular plaques in the occipital lobe may simulate occipital horn, and plaques in the corpus callosum may simulate lateral ventricle; confluent paraventnicular iesions may appear as enlargement of the ventricle; subcortical
lesions
may
simulate
sulci
or
fissures,
or
when
detected as an abnormality on CT may suggest infarct rather than a demyelinating process. The study would have been more valuable if the brains had also been scanned when living. However, differences in CT appearance between cadaver and living brains are mainly related to the cortex. The attenuation numbers of cadaver white matter and demyelinated plaques agree well with in vivo measurements by the same scanner and with published data [1 6] We conclude that the minimum size of chronic cerebral demyelinated plaques detectable with the CT techniques we used is 7 mm, and that plaques larger than 7 mm may be missed
computerized transaxial tomograms. Neurology (Minneap) 27:890-891, 1977 3. Gyldensted C: Computer tomography of the brain in multipie sclerosis. A radiologic study of 110 patients with special reference to demonstration of cerebral plaques. Acta Neurol Scand 53 : 386-389, 1976 4. Jacobs L, Kinkel WA: Computerized axial tomography in multiple sclerosis (abstr). Neurology (Minneap) 26:390391,
they
simulate
a normal
bral involvement cannot presumed demyelination, negative.
structure.
be ruled out even though
Therefore,
cere-
in a patient with the CT scan is
1 Cala IA, Mastaglia FL: Computerized axial tomography multiple sclerosis. Lancet 1 :689, 1976 2. Cole M, Ross RH: Plaques of multiple sclerosis seen .
rosis.
Paper
presented
Society
RJ, Rothner
computed
DA, Duchesneau
tomography
at the annual
of North America,
PM,
in multiple
meeting
Chicago,
scle-
of the Radio-
November,
1977
6. Aita JF, Bennett DA, Anderson RE, Ziter F: Cranial appearance of acute multiple sclerosis. Neurology (Minneap) 28: 251-255, 1978 7. Robertson WC, Gomez MR, Reese EF, Okazaki H: Comput-
erized
tomography in demyeiinating disease of the young. (Minneap), 27 : 837-842, 1977 8. Aita JF, Bennett D, Anderson R, Ziter F: Cranial CT appearance of multiple sclerosis. Neurology (Minneap) 28:251Neurology
255, 1978 9. Campbell BA, Pedley TA: Computerized tomography in cerebral diseases of white matter. Neurology (Minneap) 28: 534-544, 1978 1 0. Aita JF: Cranial CT and multiple sclerosis: contrast enhancing lesions (letter). Arch Neurol 35 : 183, 1978 ii. Eyerman DL, Archer CR. Mayer B Jr: Multiple sclerosis in
brain and optic nerves seen by standard and high resolution CT (abstr). Neuroradiology 1 2 : 52, 1976 12. Binder GA, Haughton VM, Ho DC: Computed tomography
13.
of anatomic specimens. 508, 1978 Di Bianca FA, Edelheit
J Comput LS, Eisner
Assist AL, Glover
Tomogr
ida, March
16. Radue
T, DiChiro
G, Brooks
differentiation Tomogr
RA,
in computed
1 :437-442,
EW, Kendall
computed roradiology
GS:
of CT image Symposium Beach, Fior-
1978
14. Haughton V. Harrington G, Schmidt contrast enhancement for computed in multiple sclerosis (abstr). J Comput 1977 Arimitsu
2:506-
GH, Keyes
The contrast-detail-dose diagram as a measure quality. Paper presented at the International and Course on Computed Tomography, Miami
Assist
on
D: Cranial
logical
matter in
MN, Lederman
Norman
15.
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1 :271,
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