Intracranial meningiomas

Neuroradiology(1990) 32:12-18

Neuro -radiology 9 Spfinger-Verlag1990

Intracranial meningiomas Comparison of plain and contrast-enhanced examinations in CT and MRI W. Sch6rner 1, P. Schubeus 1, H. Henkes 1, C. Rottacker 1, B. H a m m 2, and R. Felix 1 DepartmentsofRadiology,UniversityClinics i RudolfVirchow/Charlottenburgand 2 Steglitz,Free UniversityofBerlin, Federal Republicof Germany Received: 7 September 1989

Summary. Fifty patients with intracranial meningiomas underwent plain and contrast-enhanced examinations with CT and MRI. Each of the MR studies consisted of three plain (T1, proton density and T2-weighted) and a post-contrast series (0.1 mmol Gd-DTPA/kg body weight). All techniques (plain CT, plain MRI, contrastenhanced CT, contrast-enhanced MRI) proved to be highly efficient as regards tumour detection: depending on the technique, an intracranial lesion was demonstrated in 47-50 cases. The image contrast was assessed as good or excellent in 21 cases having plain CT and in 33 cases having plain MRI, but in 46 and 50 of the contrast-enhanced CT and MRI studies respectively. Adequate tumour delineation was achieved in 18 cases with plain CT, in 35 cases with plain MRI and in 46 and 50 cases of the contrast-enhanced CT and MRI examinations. The contrast-enhanced studies proved to be superior to the plain CT and MRI studies as regards image contrast and tumor delineation. Because of the methodological advantages of the MR/technique, contrast-enhanced MRI was judged to be slightly superior to contrast-enhanced CT. Key words: Meningioma- Computed tomography- Magnetic reconance imaging- Contrast-enhanced studies

Computerised tomography (CT) is a highly efficient procedure in the diagnosis of intracranial meningiomas. In meningioma patients, plain CT and contrast-enhanced CT are reported to demonstrate an intracranial lesion in 85% and 95% of cases, respectively [1]. So far, plain magnetic resonance imaging (MRI) has disappointed in the diagnosis of intracranial meningiomas. Relatively poor image contrast between meningioma and the adjacent tissues often resulted in inadequate demonstration of the tumour [2-4]. At the same time, contrast-enhanced CT - in which an intensely contrast accumulating tumour regularly led to a high level

of image contrast between tumour and surrounding tissues - appeared to be superior to the plain MRI studies [5-7]. The introduction of the paramagnetic MRI contrast medium gadolinium-DTPA (Gd-DTPA) has resurrected the question of the value of MRI in the diagnosis of meningiomas. Consequently, we compared 50 cases for whom both plain and contrast-enhanced examinations with CT and MRI were available in respect of the diagnostic value of the methods.

Patients and methods Patients 48 patients (5 female, 43 male, 27-81 years) with a total of 50 intracranial meningiomas were included in the study. The diagnosis was confirmed by histology in 43 cases and was based on the CT findings in 7.

Me~o~ All patients underwent both a plain and a contrast-enhanced CT examination. The CT studies were done on various scanners, but mainly with a Siemens Somatom DR2. The slice thickness was usually 8 mm. In most cases, the contrast medium was administered as a rapid drip infusion with 100 ml of a renal contrast agent. The MRI examinations were performed on a wholebody imager (0.35 or 0.5 Tesla Magnetom, Siemens) using a head coil (internal diameter: 30 cm). Three plain and one contrast-enhanced series were done for each patient. The plain MRI examination consisted of a T1, a proton density and a T2-weighted sequence. The T1weighted scans were obtained using either the spin-echo (SE) or gradient-echo (GE) technique; the pulse repetition time (TR) and the echo time (TE) were 400 ms and

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Fig. 1 a-f. Superiority of plain MRI over plain CI': While demonstration of the tumour is inadequate in plain CT, it is excellent in plain MRI and in the contrast-enhanced Cr and MRI (38 years, male, meningioma of the frontal convexity), a, b Plain and contrast-enhanced CT: The tumour appears isodense in the plain CT scan (a); indirect signs of tumour exist in the form of perifocal oedema. Homogeneous accumulation and good tumour demonstration after

contrast administration (b). e, d Plain MRI, SE 1600/30 and SE 1600/90: Poor (c) and good image contrast (d) between tumour and cerebral tissue in plain MRI. e, f Plain and contrast-enhanced MRI, SE 400/30: Excellent demonstration of the tumour even in the plain MRI scan (e). Intense contrast uptake and excellentimage contrast and tumour delineation after Gd-DTPA (ft

30 ms (SE 400/30) with the SE technique and 315 ms and 14 ms (GE 315/14) with the G E technique at a flip angle of 90degrees. The proton density and T2weighted scans were each done in the SE technique with a T R of 1600 ms and a TE of 30 and 70 or 90 ms (SE 1600/30 and SE 1600/70 or SE 1600/90). A contrastenhanced scan using the above-mentioned Tl-weighted technique was obtained in all patients after intravenous administration of 0 . 1 m m o l G d - D T P A (Magnevist, Schering). A n axial imaging plane was used in most cases; a coronal plane was preferred for tumours located close to the base of the skull or in a high parietal position, while a sagittal projection was chosen for mid-line tumours. In each

case, the slice thickness was 10 mm, and the image matrix consisted of 256 • 256 pixel.

Evaluation The different examination techniques (plain CT, contrastenhanced CT, plain M R I and contrast-enhanced M R I ) were evaluated in respect of detection of an intracranial lesion, the image contrast between tumour and normal brain tissue and the quality of tumour delineation. Of the three sequences making up a plain M R examination, the sequence which showed the best result in respect of an assessment criterion was included in the evaluation.

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Fig.2 a-f. Superiority of contrast-enhanced CT and MRI over plain MRI: No tumour demonstrable in any of the plain MR sequences, but good visualization of the tumour in the plain CT scan and in the contrast-enhanced CT and MR scans (60 years, female, meningioma of the wing of the sphenoid), a, b Plain and contrast-enhanced CT: Demonstration of a hyperdense tumour even in the plain CT scan (a). After contrast administration (b), intense enhancement and

F o u r grades w e r e possible for the visual assessment of the t u m o u r contrast [extent of the difference in the density or signal intensity b e t w e e n t u m o u r and n o r m a l brain (white matter)]: 0 = no contrast, + =slight image contrast, + + = good image contrast, + + + = excellent image contrast. T h e criterion c h o s e n for the assessment of the image quality of the m e n i n g i o m a was t u m o u r delineation. This was defined as the ability to differentiate b e t w e e n t u m o u r and surroundings on the basis of a difference in the density or signal intensity b e t w e e n t u m o u r a n d adjacent tissue (e. g. n o r m a l brain tissue, perifocal o e d e m a ) and of indirect signs (e. g. t u m o u r capsule). Again, f o u r grades w e r e used for the assessment of the t u m o u r delineation: 0 = no delineation, + =poor delineation, + + = good delineation, + + + = excellent delineation. In the assessment o f the diagnostic value, the grades no o r p o o r image contrast and no o r p o o r t u m o u r delinea-

excellent tumour contrast, c, d Plain MRI, SE 1600/30 and SE 1600/70: No demonstration of a pathological finding, e, fPlain and contrast-enhanced MRI, GE 315/14: No demonstration of a tumour in the plain Tl-weighted scan (e). After administration of GdDTPA (f), intense contrast enhancement and excellenttumour demonstration

tion were r e g a r d e d as non-diagnostic, while the two o t h e r grades were defined as diagnostic.

Results Plain C T A n intracranial lesion was d e m o n s t r a t e d in 47 of the 50 plain C T examinations. O f these, direct signs of t u m o u r were recognisable in 41 cases and only indirect signs in 6. T h e turnouts were isodense in 10 cases ( = no contrast) (Fig. 1). T h e contrast b e t w e e n m e n i n g i o m a and n o r m a l brain tissue was g r a d e d aspoor in 19 cases, as good in ano t h e r 19 cases (Fig. 2) and as excellentin only two (Table 1). Turnout delineation was assessed as absent or poor in 32 cases, In the remaining 18, the delineation was g o o d or excellent (Table 2).

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Fig.3a-f. Superiority of MRI over CT because of methodological advantages: Good turnout demonstration in the MR scan, but nondiagnostic CT image of the tentorial meningioma due to streak artifacts (44 years, female, tentorial meningioma), a, b Plain and contrast-enhanced CT: Non-diagnostic demonstration of the tentorial meningioma due to beam-hardening artifacts, e, d Plain MRI,

SE 1600/30 and SE 1600/70: In both images tumour demonstration by partial filling of the cerebellar cistern. In the T2-weighted scan (d), also good tumour contrast and direct demonstration of the meningioma (arrow). e, fPlain and contrast-enhanced MRI, GE 315/14: After Gd-DTPA (f), intense contrast enhancement and good turnout demonstration

Contrast-enhanced CT

f r a t e n t o r i a l m e n i n g i o m a s (Fig.3). T h e t u m o u r c o n t r a s t a n d d e l i n e a t i o n w e r e g r a d e d as good o r excellent in t h e o t h e r 46 cases (Tables 1, 2).

A t u m o u r was d e m o n s t r a t e d in 49 o f t h e 50 c o n t r a s t - e n h a n c e d C T studies. I n o n l y o n e case d i d t h e t u m o u r - a flat, high c o n v e x i t y m e n i n g i o m a - e s c a p e d e t e c t i o n with this m e t h o d (Fig. 4). O f t h e 49 m e n i n g i o m a s visualized, t h e t u m o u r contrast a n d d e l i n e a t i o n w e r e g r a d e d aspoor in 3 cases each. B e a m - h a r d e n i n g artifacts w e r e r e c o r d e d as t h e r e a s o n for t h e p o o r d e m o n s t r a t i o n in t h e s e cases - a f r o n t o b a s a l m e n i n g i o m a with o n l y p o o r c o n t r a s t u p t a k e and two in-

Plain M R I A n i n t r a c r a n i a l lesion was d e m o n s t r a t e d in 49 o f t h e 50 p l a i n M R I studies. I n 48 cases, a d i f f e r e n c e in t h e signal intensity b e t w e e n t u m o u r a n d b r a i n tissue was d e m o n s t r a b l e in at least o n e o f t h e t h r e e p l a i n s e q u e n c e s . I n o n e case, t h e d e m o n s t r a t i o n o f a p a t h o l o g i c a l finding was

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Fig.4a-L Superiority of MRI over CT because of methodological advantages: Excellent tumour demonstration in the contrast-enhanced MRI scan, but no CT demonstration of the high-parietal tumour (76 years, male, 1. high-parietal meningioma of the convexity, 2.meningioma of the falx), a, b Contrast-enhanced CT above the level of the cella media (a) and at a high parietal level (b): Excellent visualization of the meningioma of the falx (a), but no demonstration of the very high parietal tumour. (In higher slice, not shown here, the

tumour was also inconspicuous), e, d Plain MRI, SE 1600/30 and SE 1600/70: Indirect demonstration of the meningioma of the falx (arrow heads), indirect demonstration of the high parietal tumour, which contrasts dearly with the signal-free calvaria (arrows). e, f Contrast-enhanced MRI, axial and sagittal imaging plane: Intense contrast enhancement and good delineation of both meningio-

limited to indirect signs of tumour. I n only one case no pat h o l o g y could be f o u n d in any plain image (Fig. 2). T h e contrast b e t w e e n m e n i n g i o m a and brain tissue was g r a d e d as absent orpoor in 17 cases. In the remaining 33 cases, the t u r n o u t contrast was assessed as good or ex-

of the t u m o u r was good in 15 cases and excellent in 35 (Figs. 1-4).

cellent. D e l i n e a t i o n of 14 of the 49 turnouts d e m o n s t r a t e d was g r a d e d as non-diagnostic, while it was assessed as good or excellent in the other 35 cases (Table 2).

Contrast-enhanced MRI Direct d e m o n s t r a t i o n of an intracranial lesion was achieved in all 50 cases. T h e t u m o u r contrast was g r a d e d as good in 12 cases and as excellent in 38. T h e delineation

mas

Comparison of plain and contrast-enhanced CT and MRI Tumour demonstration. D e p e n d i n g on the technique (plain CT, c o n t r a s t - e n h a n c e d CT, plain M R I , contrast-enh a n c e d M R I ) , a pathological finding was d e m o n s t r a t e d in 47 to 50 cases. In 41 cases, the n u m b e r of turnouts d e m o n strated directly was relatively low only for plain CT, direct d e m o n s t r a t i o n of the t u m o u r being possible with the o t h e r techniques in 48-50 cases.

17 Table 1. Image contrast betweentumour andnormalbraintissueon

plain and contrast-enhanced CT and MRI studies in 50 cases Imaging technique

Image contrast

0 + ++ +++ Plain CT 10 19 19 2 Contrast-enhanced CT 1 3 14 32 Plain MRP 2 15 31 2 Contrast-enhanced MRI 0 0 12 38 Plain MRI examination included 3 pulse sequences (T1, proton density, T2-weighted images) in each case Note: 0 = no, + : poor, + + = good, + + + = excellent tumour contrast Table 2. Tumour delineation on plain and contrast enhanced CT

and MRI studies in 50 meningiomas Imaging technique

Tumour delineation 0 + § +++ Plain CT 8 24 16 2 Contrast-enhanced CT 1 3 14 32 Plain MRI a 2 13 31 4 Contrast-enhanced MRI 0 0 15 35 a Plain MRI examination included 3 pulse sequences (T1, proton density, T2-weighted images) in each case Note: 0 = no, + = poor, + + = good, + + + = excellent mmour delineation

Tumour contrast. T u m o u r contrast was much higher with the contrast-enhanced techniques than in the plain studies. Good or excellent t u m o u r contrast was achieved in plain CT and plain M R I in only 21 and 33 cases, respectively, but in 46 and 50 cases examined by contrast-enhanced CT and MRI, respectively. Tumour delineation. Plain M R I produced better results than plain CT: Good or excellent t u m o u r delineation was achieved in 18 and 35 cases with plain CT and plain MRI, respectively. The contrast-enhanced studies produced better results again than the plain examinations - g o o d or excellent delineation was achieved in 46 and 50 cases, respectively.

Discussion

Plain M R I is a very sensitive procedure for the demonstration of cerebral lesions. It has b e e n shown to be superior to contrast-enhanced CT in the visualization of gliomas, infarcts and loci of inflammation and demyelinisation [8]. On the other hand, contrast-enhanced CT offers advantages over plain M R I in individual cases in the demonstration of benign, extra-axial tumours such as meningiomas and neurinomas [5-7, 9]. Measurements of the relaxation times of meningiomas have shown that the T1 and T2 times of these tumours differ only slightly f r o m those of healthy cerebral tissue [2-4, 10, 11]. In keeping with this, most plain M R images - particularly T2-weighted SE scans, which are nowadays used as a screening sequence - showed only p o o r turnout contrast in the case of meningiomas. The relatively p o o r

image contrast in plain M R scans has m e a n t that the clarity of detail in the case of larger meningiomas and the detection rate in the case of smaller meningeal tumours has lagged behind that of the contrast-enhanced techniques [5-7, 12]. Quantitative evaluations of M R scans of intracranial tumours have revealed a significantly higher signal-tonoise ratio between t u m o u r and normal brain tissue in contrast-enhanced T l - w e i g h t e d scans in comparison to plain T2-weighted M R images [13]. In our own study population, a difference in the signal intensity between the meningiomas and normal brain tissue was demonstrable in 48 out 50 plain M R I studies. However, the tumour contrast in the three plain sequences examined was often poor. Good or excellent image contrast between tum o u r and adjacent tissue was observed in only 33 of the 50 cases. By way of comparison, good or excellent image contrast was achieved in 46 and 50 of the 50 cases after contrast administration in CT and MRI, respectively. E v e n more pronounced were the differences between plain M R I and the contrast-enhanced procedures when only the studies with excellent image contrast and therefore excellent clarity of detail were considered: while the image contrast provided by plain M R I was graded as excellent in only two cases, it was given this grade in 32 and 38 cases examined with contrast-enhanced CT and MRI, respectively. This similarity is not surprising as enhancement is based on the same pathomechanism: while the intact blood brain barrier of healthy cerebral tissue does not permit any extravasation of x-ray contrast material or GdDTPA. In the case of meningiomas which do not present a blood brain barrier contrast m e d i u m regularly leaks into the interstitial space of the tumour with a corresponding effect on the image in contrast-enhanced CT and M R I [14, 15]. With the exception of completely calcified meningiomas, which were already demonstrabe in plain CT scans as very hyperdense lesions, contrast enhancement of the meningiomas was observed in all cases in our study population. Although the administration of contrast m e d i u m in CT and M R I leads to a similar effect on the imaging of meningiomas, G d - D T P A - e n h a n c e d M R scans were considered to be of a slightly higher diagnostic value than the contrast-enhanced CT studies. The advantages of contrast-enhanced M R I over contrast-enhanced CT stem f r o m the methodological benefits of the M R I technique itself. The qualitative better demonstration of cerebral structures at the borders between bone and soft tissue and the possibility of avoiding partial volume effects by the use of additional imaging planes made contrast-enhanced M R I seem to be the better imaging technique. Thus, particularly infratentorial, ffontobasal and high-convexity meningiomas - sites of predilection for this type of t u m o u r - are demonstrated better by contrast-enhanced M R I than by contrast-assisted CT [2]. To summarize, the four imaging techniques analysed can be placed in the following ascending order of diagnostic value as regard the tumour detection, the image contrast and tumour delineation: plain CT, plain MRI, contrast-enhanced CT and contrast-enhanced MRI. In general, the contrast-assisted procedures are superior to

18 the plain techniques in respect of sensitivity because of the higher image contrast which t h e y provide. H o w e v e r , the differences b e t w e e n c o n t r a s t - e n h a n c e d C T and contraste n h a n c e d M R I are slight as regards the detection rate of t u m o u r s and b e c o m e relevant only in the case of t u m o u r s in u n f a v o u r a b l e sites of d e m o n s t r a t i o n by CT.

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