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DYNAMIC MR IM AGING IN THE DETECTION OF

PITUITARY MICROADENOMA*

Gazanfer Ekinci, M.D.** / Feyyaz Baltacıoğlu, M.D.** / İlhan Elmacı, M.D.***

Necmettin Pamir, M.D.*** / Canan Erzen, M.D.**

* *

D e p artm en t o f Radiology, S chool o f M edicine, Marmara University, Istanbul, Turkey.

* * * D e p artm en t o f neurosurgery, S chool o f Medicine, Marmara University, istanbul,

Turkey.

ABSTRACT

Objective:

In th is s tu d y o u r p u rp o se w as to co m p a re e ffic ie n c y in d e te c tin g m icro a d e n o m a b e tw e e n c o n v e n tio n a l u n e n h a n c e d M RI and c o n tra s t-e n h a n c e d M RI w ith d y n a m ic fa s t spin- echo m ethod.

Methods:

T h irty -tw o p a tie n ts w ith su s p e c te d p itu ita ry m ic ro a d e n o m a h ad u n e n h a n c e d , d y n a m ic fa s t sp in -e c h o c o n tra s t e n h a n ce d and c o n v e n tio n a l c o n tra s t-e n h a n c e d M R im aging of the p itu ita ry gland. All M R stu d ie s w e re review ed fo r the p re se n ce o r a b s e n c e of any p ituitary focal p a th o lo g ic a l in te n s ity c o n s is te n t w ith m icro a d e n o m a .

Result:

A p itu ita ry le s io n c o n s is te n t in a p p e a ra n c e w ith a m ic ro a d e n o m a w as dete cte d on d y n a m ic fa s t s p in -e c h o im a g e s in 17 of the 32 p atients, on u n e n h a n c e d im a g e s in 8 patients, and on co n v e n tio n a l c o n tra s t-e n h a n c e d im ages in 11 patients.

Conclusion:

D yn a m ic fa s t s p in -e c h o im aging is a u se fu l s u p p le m e n ta l s e q u e n c e in p a tie n ts un d e rg o in g M R im a g in g b e c a u se of pituitary e n d o c h rin o p a th y . It m ay s h o w le sio n s th a t m ight o th e rw ise e sc a p e d e te ctio n .

Key Words:

M agnetic resonance im aging, P ituitary m icroadeno m a , D ynam ic MRI

INTRODUCTION

T he d e tection of pituitary m icro a d e n o m a s on MR im aging strongly d e pen ds on the im age contrast b etw een the m icro a d e n o m a and norm al pituitary tissue. C o n tra st-e n h a n ce d MR im aging has been e xte n sive ly used to im prove im age contrast and hence the d e tection of m icroadeno m a s. Rapid d y n a m ic M R im a g in g m ay in c re a s e im age co n tra s t beyond that of conventio nal contrast- e n h an ced im aging (1-4). It has been reported th a t better co n tra st betw een the norm al pituitary g la n d and m icro a d e n o m a s can be seen on im ages obtained shortly after the adm inistration of g a d o p e n te ta te d im e g lu m in e , as it accum ulates in m icro a d e n o m a s slightly m ore slow ly than in the norm al pituitary gland; this co n tra s t m ay be lost on later im ages (5-6).

In this study; our pu rp o se w as to co m pare how fre q u e n tly a m icro a d e n o m a could be detected w ith con ve n tio n a l u n e n h a n ce d MRI, w ith contrast enhan ced MRI and w ith d yn a m ic fast spin-echo (FSE) MRI.

* T h i s s t u d y w a s p r e s e n t e d a t t h e E u r o p e a n C o n g r e s s o f R a d i o l o g y , M a r c h 7 - 1 2 1 9 9 9 , V i e n n a , A u s t r i a .

( A c c e p t e d 2 2 O c to b e r , 2 0 0 0 ) M a r m a r a M e d ic a l J o u r n a l 2 0 0 1 ; 1 4 (1 ) : 2 3 - 2 6

Correspondance to: Gazanfer Ekinci, M.D. - e.mail address: gazanfere@hotmail.com

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Gazanfer Ekinci, et al

MATERIAL AND METHODS

T h irty-tw o p a tients w ith c lin ica l and bio ch e m ica l evidence of s u sp e cte d p itu ita ry a d e n o m a s m ade up th e s tu d y g ro u p . A ll e x a m in a tio n s w e re perform ed w ith 1.5-T s u p e rc o n d u c tiv e MR units. T he im aging te c h n iq u e w a s the sam e in all p atients. For initial im a g in g , an un e n h a n ce d coronal T 1 -w e ig h te d m u ltislice co n ve n tio n a l spin- echo s e q u e n ce (T R /T E = 4 0 0 /1 1 ) and fa st spin- e c h o T 2 -w e ig h te d (T R /T E = 3 0 0 0 /9 5 , E T = 1 6 ) sequ e n ce w e re used. T hen, co ro n a l d yn a m ic FSE im a g in g (T R /T E = 3 5 0 /1 1, E T=4) sta rte d s im u lta n e o u s ly w ith th e b o lu s in je c tio n of co n tra st m aterial (g a d o p e n te ta te d im e g lu m in e , 0.1 m l/k g ). Six sets of d y n a m ic im ages, each co n sisting of three slice lo ca tio n s, w e re acquired at 2 4 -se c intervals. Im m e d ia te ly a fte r co m p le tio n of the d yn a m ic scan, the c o ro n a l T1 -w eighted con ve n tio n a l s p in -e ch o s e q u e n ce w a s repeated. All scans had 3-m m slice th ic k n e s s and 0.3-m m

gap-MR im ages of the p a tie n ts w e re film e d in an identical form at. R egion-of-interest m easurem ents of p itu ita ry /a d e n o m a co n tra s t w ere don e in all d y n a m ic FS E im a g e s . An e x p e rie n c e d ne u ro ra d io lo g ist re vie w e d all the unenh anced, co n tra st-e n h a n ce d , and d y n a m ic FSE im ages for the p resence or ab se n ce of any p itu ita ry focal p a th o lo g ic a l in te n s ity c o n s is te n t w ith m icroadenom a.

RESULTS

A pituitary lesion c o n s is te n t in a p p e a ra n ce w ith a m icro a d e n o m a w a s d e te c te d on d yn a m ic FSE im ages in 17 of the 32 patients, on u n e n h anced im a g e s in 8 p a tie n ts , a nd on c o n v e n tio n a l c o n tra s t-e n h a n c e d im a g e s in 11 p a tie n ts . D ynam ic FSE im ages s h o w e d all m icro a d e n o m a d e te c te d by c o n tra s t-e n h a n c e d im a g e s and u n e n h a n c e d im a g e s . D y n a m ic FS E im a g e s s h o w e d m ic ro a d e n o m a s in 17 p a tie n ts . C o m p a re d to u n e n h a n c e d a nd c o n v e n tio n a l co n tra st-e n h a n ce d MR, d y n a m ic FSE im ages detected 6 a d d itio n a l m icro a d e n o m a s. T he range of m icro a d e n o m a s ize s w a s 3-10 mm. Illustrative e x a m p le s of d y n a m ic FS E im a g e s and unenh anced and co n tra s t e n h a n ce d im ages of m icro a d e n o m a s are show n in fig u re 1. and figure 2. R e g io n -o f-in te re s t m e a s u re m e n t of p itu ita ry/ a deno m a co n tra s t is seen in fig u re 3.

c

F i g . l : Unenhanced (a), enhanced (b) and dynamic FSE (c) images of the pituitary gland: All sequences show microadenoma.

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Dynamic MR imaging in the detection of pituitary microadenoma

C

F i g . 2 : Unenhanced (a), enhanced (b) and dynamic FSE (c) images of pituitary gland: Microadenoma is seen best on early phase of dynamic FSE image.

DISCUSSION

T o d a y MR im aging has largely replaced CT as th e p re fe rre d te c h n iq u e fo r in itia l im a g in g eva lu a tio n of susp e cte d p a th o lo g ic condition s of the pitu ita ry gland. O ptim al MR im aging protocol has not yet been u n ifo rm ly accepted and will also be expected to vary according to the precise clinical problem being investigated.

R outine use of m a gnetic resonance im aging has not a lw a ys p ro v id e d a c c u ra te and s u ffic ie n t inform ation for the surgical tre a tm e n t of pituitary a d e n o m a s d e s p ite a p p lic a tio n o f h ig h -fie ld s u p e rco n d u ctive MR units. In som e patients, routine MR im aging m ay not reveal a b n orm alitie s in th e p re s e n c e o f d e fin ite h o rm o n a l abnorm alitie s.

T he optim al im aging stra te g y fo r evaluatin g a p atient with a susp e cte d p ituitary m icro a d e n o m a depen ds largely on the tre a tm e n t p h ilosop hy of the referring e n d o c rin o lo g is t o r surgeon. At m any in s titu tio n s , s m a ll p ro la c tin o m a are tre a te d m edically; here, the role of im aging is to exclude a m a c ro a d e n o m a o r o th e r c e n tra l p ro c e s s causing increased prolactin level. C onversely, at in s titu tio n s w h e re m o s t m ic ro a d e n o m a s are treated surgically, p re o p e ra tive know ledg e of the p ro bable size and location of the ad e n o m a is m ore im portant; im aging stra te g ie s th a t allow

F i g .3 : Dynamic FSE images of pituitary gland: Region-of- interest measurements of pituitary/adenoma contrast is seen. Immediately after contrast injection, normal pituitary gland enhances more than adenoma.

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Gazanfer Ekinci, et al

even a sm all fra ctio n of a d d itio n a l m icro a d e n o m a to be identified m ay be crucial.

C onspicuity of m ic ro a d e n o m a s va rie s from case to case, and th e re fo re no sin g le MR se q u e n c e is co n siste n tly b e st fo r im aging. O n un e n h a n ce d MR im ages, the d iffe re n c e s in c o n s p ic u o u s n e s s are m ost likely due to in h e re n t d iffe re n c e s in MR re la x a tio n b e tw e e n a d e n o m a s . O n c o n tra s t e n h a n c e d im a g e s , d iffe re n c e s in co n s p ic u o u s n e s s arise from v a ria tio n s in tissue perfusion, the size of the e x tra c e llu la r space, and the p e n e tra tio n o f c o n tra s t a g e n ts in to th e e x tra c e llu la r s p a c e . T h e s e tis s u e p ro p e rtie s c a n n o t be p re d ic te d ; th e re fo re , if c lin ic a l c irc u m s ta n c e s n e c e s s ita te lo c a lis in g th e adeno m a , m ore th a n one se q u e n c e m ust be used in ord e r to co v e r all po ssib ilitie s. T o im prove the d ia g n o s tic u s e fu ln e s s o f MR im aging in pituitary a deno m a s, g a d o p e n te ta te d im e g lu m in e - enhan ced d yn a m ic MR im aging w a s in tro d u ce d to increase the co n tra s t b e tw e e n norm al p ituitary tissue and p ituitary a d e n o m a s. A n u m b e r of in ve stig a to rs used d y n a m ic M R m e th o d s for exam ination of the pitu ita ry gland. S a ka m o to et al. (1) used c o n v e n tio n a l s p in -e ch o im ages for d ynam ic MR im aging but reduced the m atrix size and n um ber of s ig n a ls a v e ra g e d in o rd e r to im prove te m p o ra l re so lu tio n . T he n u m b e r of m icro a d e n o m a s visu a lis e d in creased, but the spatial resolution and s ig n a l-to -n o is e ratio of the im ages w e re c o n s id e ra b ly re d u ce d co m p a re d to those of the usual d ia g n o s tic se q u e n ce s. S tadnik et al. (4) use d a g ra d ie n t-e c h o m e th o d . S u sce p tib ility a rte fa cts from the skull base and a ir-c o n ta in in g s p h e n o id s in u s a re in h e re n t d isa d va n ta g e s to th is a p p ro a ch . M o st recently, T- 1 w eig h te d FSE m e th o d s have been used. FSE im aging is in h e re n tly fa s te r than c o n ve n tio n a l spin-echo im aging. In o u r study, d y n a m ic FSE MR im a g e s in 32 p a tie n ts w ith p itu ita ry e n d o c rin o p a th ie s s h o w e d 17 fo c a l p itu ita ry lesions w hich w e re c o n s is te n t in a p p e a ra n ce w ith m icroadeno m a s. Six of 17 m ic ro a d e n o m a s w ere not visible on e ith e r c o n v e n tio n a l un e n h a n ce d or

co n tra s t e n h a n ce d M R im ages. O n e a rly -p h a s e d y n a m ic MR im ages, m ic ro a d e n o m a s w e re w ell vis u a lis e d w ith c le a r borders. T h e d iffe re n tia tio n b e tw e e n a n o rm a l p itu ita ry g la n d a nd th e m icro a d e n o m a , how ever, w a s not e v id e n t on the la te -p h a s e d y n a m ic im ages.

D ynam ic FSE im aging is a useful s u p p le m e n ta l se q u e n c e in p a tie n ts u n d e rg o in g M R im aging beca u se of pitu ita ry e n d o c rin o p a th y . It m ay show lesions th a t m ight o th e rw is e e sc a p e d e te c tio n . If the la b o ra to ry re sults s u g g e s t the p re s e n c e o f an a d eno m a , and if p re fe rre d tre a tm e n t stra te g y is g e n e ra lly su rg e ry, d y n a m ic im a g in g m ay be p e rfo rm e d as a su p p le m e n ta l s e q u e n c e to o th e r c o n v e n tio n a l u n e n h a n c e d a nd c o n tra s t e n h a n ce d M R im aging.

REFERENCES

1 . S a k a m o t o Y , M u t s u m a s a T , K o r o g i Y , B u s s a k a i f , U s h i o Y. n o r m a l a n d a b n o r m a l p i t u i t a r y g l a n d s : g a d o p e n t e t a t e d i m e g i u m i n - e n h a n c e d M R i m a g i n g . R a d i o l o g y 1 9 9 1 ; I 7 8 : 4 4 1 - 4 4 5 . 2 . M i k i Y, M a t s u o M , S a d a h i k o H , e t a l . P i t u i t a r y a d e n o m a s a n d n o r m a l p i t u i t a r y t i s s u e : e n h a n c e m e n t p a t t e r n s o n g a d o p e n t e t a t e - e n h a n c e d M R i m a g i n g . R a d i o l o g y 1 9 9 0 ; 1 7 7 : 3 5 - 3 8 . 3 . F i n e l l i D A , K a u f m a n n B . V a r i e d m i c r o c i r c u l a t i o n o f p i t u i t a r y a d e n o m a s a t r a p i d , d y n a m i c , c o n t r a s t - e n h a n c e d M R i m a g i n g . R a d i o l o g y 1 9 9 3 ; 1 8 9 : 2 0 5 - 2 1 0 . 4 . S t a d n i k T , S t e v e n n a e r t A , B e c k e r s A , L u y p a e r t R , B u i s s e r e t T , O s t e a u x M . P i t u i t a r y m i c r o a d e n o m a s : d i a g n o s i s w i t h t w o - a n d t h r e e - d i m e n t i o n a l M R i m a g i n g a t 1 . 5 T b e f o r e a n d a f t e r i n j e c t i o n o f g a d o i i u m . R a d i o l o g y 1 9 9 0 ; 1 7 6 : 4 1 9 - 4 2 8 . 5 . D a v i s P C , H o f f m a n J C J r , S p e n c e r T , T i n d a l l G T , B r a u n I F . M R i m a g i n g o f p i t u i t a r y a d e n o m a : C T , c l i n i c a l , a n d s u r g i c a l c o r r e l a t i o n . A J R 1 9 8 7 ; 1 4 8 : 7 9 7 - 8 0 2 . 6 . H e w t o n D R , D i l l o n W P , H o r m a n D , H e w t o n T H , W i l s o n C B . G d - D T P A - e n h a n c e d M R i m a g i n g o f p i t u i t a r y a d e n o m a s . A J H R 1 9 8 9 ; 1 0 : 9 4 9 - 9 5 4 . 26

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