magnetic resonance imaging of the orbit

8/8/2019 Magnetic Resonance Imaging of the Orbit

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1015

0 .6 T M agne tic R esonanceIm ag ing o f th e O rb it

Jon H . E dwa rd&R oge r A . H ym an1

S . J . Vac irca1M ichae l A . B oxe r2

Sam ue l P acke r2Ira H . K au fm an2H a rry L . S te in1

T h is a rt ic le appea rs in the March /Apr i l 1985is su e o f AJNR and th e M ay 1985 is su e o f AJR .Rece iv ed Ju ly 2 5, 1 98 4: a cc ep te d a ft er r ev is io nO cto be r 10 , 1984 .P res en ted a t th e a nn ua l m ee tin g o f th e A mer ica nSoc ie ty o f N eu ro rad io logy , B oston , J un e 1984 .I Depa r tmen t o f R ad io lo gy , C o rn e ll U n iv e rs it y

Med ic a l C olleg e , N ew Y ork , N Y 10021 , an d N orthSho re U nive rs ity H o sp ita l, 3 0 0 Com mun ity D r.,M an hass et, N Y 1 1 030 . Ad dre ss re p rin t re qu es ts toJ . H . E dw ard s.2 Ophtha lmo logy , C orn ell U niv ers ity M ed ic al C ci-

le ge , N ew Y ork , N Y 10021 , a nd Nor th S ho re U ni-v er si ty H o sp it al , M an hass et, N Y 11 030 .AJR 144 :1015-1020 , M ay 19850361-8 03X /8 5 /1 4 45 -1 01 5C A mer ica n R oen tge n R ay S oc ie ty

M ag ne tic re so na nce (M R ) im ag in g o f th e o rb it w as pe rfo rm ed w ith a 0 .6 T s up erc on -du c tin g im ag in g system in 100 pa tien ts w ith no rm al orb i ts w ho w e re be ing eva lua tedfo r b ra in pa tho logy and in 21 add itio n a l p a tie n ts with a va rie ty o f o rb ita l les io n s tode te rm in e th e e ffic ac y o f M R im ag ing in d isp lay ing o rb ita l abno rm a lities . U sua lly , M Rs tud ie s we re per fo rmed us in g a m u ltis lice techn iq ue w ith m ultip le sp in -echo pu lsesequences and 30 , 60 , and 90 m sec echo tim es and 500 , 1500 , an d 2000 m s ec r ep et it io nt imes . Us ing sec tio n th ic knesses o f abou t 8 mm , im ag ing w as per fo rmed in th e tran s -a xia l, c oro na l, a nd sag itta l p ro je c tio n s . P ixe l s ize w as 0 .9 x 1 .8 m m , an d t h e e x am i n at io ntook abou t 30 mm . The MR find ings w ere compa re d w ith com pu ted to mo grap hic (C T)fin d ings in a ll ca s es . E ith e r comb ined ax ia l a nd co rona l s tud ie s o f 5 -m m-th ic k sec tionso r a th in ax ia l s tu dy o f 1 -m m -th ick sec tio ns fo llow ed by re fo rm a thng techn iq ues toob ta in m uftip lana r im ages w as used . C on tr as t e nh an ce me nt was used in the C T s tud ies .Both MR and C T c lea rly d em ons tra ted the so ft-t issue abnorm alfty in a ll cases excep ttwo , in w h ich M R fa ile d to de te c t th e abno rm a lity . In one , M R fa iled to de tec t a sm a llre trob ulb ar h em orrh ag e tha t occurred a fte r a su rg ic al procedure fo r r etin al d et ac hm e nt .In th e second case , ra th e r e xte ns ive ca lc ifica tio n in the pos te rio r cho ro ida l laye rs andlens w as no t de tec ted by M R im ag ing . In seve ra l o th e r cases , M R p rov id ed in fo rm atio nbe yond tha t obta ined w ith CT . M R has th e advan tage o f p ro v id ing exqu is ite ana tom icd eta il in m uftip la na r images , an d ft appea rs to be m o re sen s it ive th an C T i n d e te c ti ngsm all, su bacu te and chron ic hem orrha ge w ith in so ft-tissu e m asses in th e orb i t an d inde tec ting ischem ia o f the g lobe . C T is super io r to M R im ag ing in por tray in g fine bonedeta i l .

A pp lica tion o f m agne tic re sonance (M A ) im ag ing to the o rb it is a ttrac tiv e becausem u ltip lana r te chn iques can be pe rfo rm ed w ithou t add itiona l pos ition ing and therisks o f ion iz ing rad ia tion and con tra s t adm in is tra tion a re e lim ina ted . C om pa redw ith com pu ted tom og raphy (C T ), M A appea rs pa rticu la rly advan tageous in p rov id -ing exce llen t ana tom ic de ta il o f the in tra cran ia l pa rt o f the op tic ne rve and ch iasmin the sag itta l p lane and p rov ides in fo rm a tion conce rn ing its a lte ra tion by pa tho log icm asses . W e eva lua ted M A im ages o f the o rb its in 21 pa tien ts w ith known o rb ita lle s ions to de te rm ine its c lin ica l e ffic acy .

S ub jec ts and M e thodsW e eva lua ted the M A im ages o f the o rb its in 1 00 pa tien ts who we re be ing exam ined fo r

b ra in p a th o lo g y. Tw en ty -o n e add itio na l p a tie n ts w ith kn ow n orb ita l le s ion s w er e e va lu ate dwith M R . S ix te en tu mo ro us cond i t ions in vo lv ing the o rb its , fou r cases o f in flam ma to ry le s ions ,and one re trobu lba r hem orrhage w ere exam ined (ta ble 1 ). F ou r p atie nts h ad s pa ce -o cc up yin gle s ions o f the g lo be and 17 had ex traocu la r m asses in vo lv ing the orb i t . Age range o f thepa tien ts w as 21 -84 yea rs .

O ur find ings w ere co rre la ted w ith su rg ic a l and pa tho log ic fin d ings and , in som e cases ofin flamm a to ry d isease , w ith response to m ed ica l the rapy . T he M A im ages w ere com pa redw ith CT s can s . A CT s tud y o f e ach pa tien t w a s perfo rm ed w ith a P ick e r 1200 scanne r us in ge ith er co mb in ed ax ia l and co rona l s tud ie s o f 5 mm sec tion th ickness o r a th in ax ia l s tudy o f


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Resu l ts

1 mm sec t ions fo llo we d b y re fo rm a ttin g techn iques to ob ta in m ulti-p lana r im ages. MR w as per fo rmed on a 0 .6 T supe rconduc ting im -ag ing sys tem (T echn ica re , S olon , O H). The p rin ci pl es u nd er ly in g pu lsesequen ce s and the techn ique o f M R im ag ing have been desc r ibed[1 -4 ]. In m ost cases , the exam ina tion was per fo rmed u s in g m u lt is li cete ch n iqu e w ith m u ltip le sp in -e cho (SE ) pu lse sequen ces w ith e chotim es (TE s) o f 30 , 60 , and 90 m sec and repe tition tim es (TR s) o f 500 ,1 500 , and 2000 m sec . In a ll cases im ag ing was pe rfo rm ed in trans-ax ial, co rona l, and sag itta l p ro je c tions . W ith th is te chn ique the sec tionth ickness o f each im age p lane w as abou t 8 mm . T he p ixe l s iz e was0 .9 mm in the x ax is and 1 .8 mm in the y a xis . G en er ally , c om p le teexam ina tion w as pe rfo rm ed in abou t 30 m m.

In ou r expe rience the SE 500 /30 pu lse sequence w ithm u ltis lice te chn ique a ffo rded op tim a l con tra s t be tw een pa th -o log ic m asses and no rm a l ana tom ic s tru c tu res and a llow edgood spa tia l re so lu tion w ith a h igh s igna l- to -no ise (S /N ) ra tio .The longe r T 2 -w e igh ted SE pu lse sequences p rov ided in -c reased spa tia l b lu rr ing w ith a le ss favo rab le S /N ra tio ; andcon tra s t be tw een patho log ic m asses and no rm a l tissue w aslos t in m any cases , so tha t the pa tho log ic m ass w as unde -

TABLE 1 : Pa tho log ic L es ions in Pa tien ts with Known Orb i t a lLes ion s W ho W ere Eva lu a ted b y M R Im ag ing________ T yp e o f L es io nTumo r :

O ptic n e rve g liom aO ptic n erv e m en in giom aL ymph omaMe lanomaMetas tas isMen in g iomaD ire c t e x te ns ion from para nasa l s inu se s b y m u -

coep ide rm oid ca rc inom a (1 ), squamous -ce ll ca rc inom a (1 ), a nd o ss ify in g fib rom a(1 )

Sub to ta lIn f lammato ryHemor rhag ic

To ta l

1016 EDW ARDS E T A L . AJR :14 4 , M ay 1 985

te c ted . A s show n in a case of an in traocu la r m e lanom a (fig .1 ), th e tum o r m ass w as dem ons tra ted bes t on th e T i -w e igh ted pu lse sequence whe re the tum o r had a sho rt T ire la tiv e to the ad jacen t v itreous , p rov id ing sha rp con tra s t andgood ana tom ic d e fin it io n . H oweve r, o n th e 12 -w e igh ted pu lsesequence , as th e s igna l in ten s ity from the v itre ous in c re aseddue to its long T2 , con tra s t be tw een the tum or and thev itreo u s was le ss , and the tum o r w as no t as read ily v is ib le .

O f the 21 les ions s tud ied w ith bo th M R and C T , M R fa iledto de tec t the abno rm a lity in on ly tw o cases . In the firs t, asm a ll re trobu lba r hem o rrhage on the r igh t ( fig . 2 ) fo llowed asu rg ica l p rocedu re fo r re tina l de tachm en t. B ecause o f theh igh -s igna l re trobu lba r fa t, con tra s t be tw een the h igh -s igna lsm a ll hem o rrhage and fa t w as no t su ffic ien t to de tec t theabno rm a lity . T he second pa tien t dem onstra ted ra the r ex ten -s ive ca lc ific a tion in the pos te r io r cho ro ida l laye rs and lens o fthe le ft e ye tha t w as no t de tec ted on the M R im age . In theo ther 1 9 cases , bo th M R and CT de tec ted the so ft- tis sueabno rm a lity . In m any case s , ad d itio n a l in fo rm a tion was p ro -v ided by MR . In a case o f K im u ra d isease o f the o rb it ( fig . 3 ),w h ich is a h igh ly vascu la r in flamm a to ry cond ition cha rac te r-ized patho log ica lly by ang io lym pho id hype rp la s ia [5 ], MRdem ons tra ted a reas o f in c reased s igna l w ith in a la rge so ft-tissue m ass, ind ica ting a reas o f hem o rrhage in to the m ass ,pa tho log ica lly p roven to be subacu te and ch ron ic hem o r-rhage . C T dem onstra ted m e re ly a hom ogeneous ly densem ass in w h ich the a reas o f hem o rrhage w e re no t de tec ted .In a case o f dev ita liza tion o f the le ft g lobe (fig . 4 ), s igna l

N o. o f C ase s in tens ity from bo th the v itreous and cho ro ida l la ye rs o f thedev ita lized g lobe w as d ram a tica lly d iffe ren t from the no rm a lg lobe, and C T fa iled to dem onstra te any asymm e try in ap -pea rance o f the g lobes . P a tho log ica lly , the v itreous had

2 unde rgone lique fac tion accoun ting fo r its pro longed T 2 . In acase o f oss ify ing fib rom a o f the spheno id s inus , bo th M R and

3 C T dem onstra ted a la rge so ft-tissue m ass fil lin g the spheno ids inus , e rod ing th rough the floo r o f the an te r io r c ran ia l fo ssa .M R dem ons tra ted the tum o r to have long T i and long 12cha rac te ris tics . E ncroachm en t on the op tic ne rve by the tum o r

3 m ass w as seen w e ll on the M R sag itta l p ro je c tion , w here a1 6 change in s igna l in tens ity in the op tic ne rve was de tec ted a t4 the po in t o f tum o r in vo lvem en t; th is w as no t de tec ted on C T .

In ou r se r ie s o f fou r m e lanom as, add itiona l in fo rm a tion w as21 ob ta ined w ith M R , a lthough a ll w e re de tec ted w ith bo th M R

and C T . T hese tum ors usua lly appea red to have re la tive ly

F ig . 1 .-C ho ro id a l m ela nom a. S E 5 00 /3 0 ( A) an dS E 2 00 0/6 0 (B ). L ar ge tum or m ass (t) o cc up ie s p os -te no r pa rt o f le ft g lob e . w hich is o p tim ally dem ons tra -te d o n T i -w e ig h te d pu ls e se qu ence (A ) , w h ere tum orhas short T i re la t ive to ad jacen t v it re ou s, p ro vid in gsha rp co n tras t. H owe ve r, o n T 2-w eigh ted pu lse s e-q uence (B ), c on tras t b e tw een tum or and v itre o us isle ss , an d tu mo r is n ot rea dily v is ib le .


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F ig . 3 .-K im ura d is ea se o f o rb it. S ag itta l S E 5 00 /30 . L a rge so ft-t is sue m ass oc cup ie s superio r p a rt o fle ft o rb it. Sm all a re as o f in c re ased s ign a l (a r row-head s ) indicate area s o f hemor r hage in to m ass th a twe re no t d e te c te d o n C T .

F ig . 4 .-D e v ita liz a tion o f le ft g lobe. SE 500 /3 0 (A ) a nd S E 2000 /9 0 (B ). S ig na l in ten s ity o f v itre o us o fdev ital ized g lobe is m arke d ly in cre ased due to its p ro lo nge d T 2, p rod uc ed by liqu efa ctio n o f th e v itre ous .C om ple te re p lac em en t o f o rb ita l fa t on le ft an d opa c ifica tio n o f e th mo id a ir c ells b ila te ra lly b y s o ft -t is s u em eta sta tic a de no ca rc in om a, w hic h had resu lted in ischemia of l ef t g lo b e.

AJR: i44 , M ay 1985 MR IM AG ING OF THE O RB IT 1017

F ig . 2 .-R etro bu lb ar h em orrh ag e. A , C on tra st-e n-hanced C T scan . Sm a ll area o f in cr ea se d dens i t yre p rese n ts hem orrh ag e in re tro bu lba r sp ace . A ssoc i-a ted p ro p to s is o f rig h t g lo be . B , S E 500 /30 . R e tro -bu lb a r reg ion a ppears s ligh t ly i n homogeneous , bu th em o rr ha ge i s no t def initely identif ied b ec au se c on -t ra st b e tw e en h ig h -s ign a l sm all hem orrh ag e and h igh -s ign a l fa t w a s no t s u ff ic ie n t to d is tin gu ish be tw eenth e tw o.

h igh s igna l on the T i -w e igh ted im ages, and in crease in s igna lw as no ted in th ree o f fou r o f the m e lanom as on the T 2 -w e igh ted im ages. These find ings ag ree w ith those o f De -LaPaz et a l. [6 ] in M R o f hem o rrhag ic le s ions in c lud ingm e lanom as . S ince three o f fou r m e lanom as show ed a sho rtT i and long 12 (un lik e the e ffe c t o f a pa ram agne tic subs tancesuch as m e lan in , w h ich w ou ld be expec ted to sho rten bo thre laxa t ion tim es ), they appea r to be com pa rab le to othe rsubacu te o r ch ron ic hem o rrhag ic tissue in s igna l cha rac ter is -tics , w ith no c lea r ly d isce rn ib le pa ram agne tic e ffe c t o f m elan in .The one m e lanom a tha t dem ons tra ted sho rt T i and sho rt T2m os t lik e ly had these cha rac te r is tics because o f the pa ra -m agne tic e ffe c ts o f m e lan in . In a ll fou r m e lanom as, C Tshow ed a nonenhanc ing hype rdense les ion tha t cou ld havebeen in te rp re ted as e ithe r tum o r o r hem o rrhage . In a 4 mmm e lanom a (fig . 5 ) lo ca ted in the m ed ia l quad ran t o f the le ftg lobe , both M R and CT de tec ted the abno rm a lity equa lly we ll,a lthough the m a rg in s o f the le s ions w ere seen m o re c lea r lyon C T .

P a tho log ic m asses cou ld be read ily lo ca liz ed re la tive to andd is tingu ished from the op tic ne rve , som e tim es because o fd iffe rence in s igna l in tens ity be tw een the m ass and the nerve ;

th is w as true fo r a la rge m e lanom a m ed ia l to the op tic ne rve(fig . 6 ). In o the r cases , m asses cou ld be d is tingu ished fromthe op tic ne rve because o f the de tec tion o f a la ye r o f fa tbe tween the m ass and nerve on the co rona l o r sag itta lp ro je c tion , w h ich w as no t poss ib le in the transax ia l p lane (fig .7 ). M ultis lice te chn ique in the sag itta l p ro je c tion cons is ten tlydem onstra ted exce llen t ana tom ic de linea tion o f the 1 .0 -1 .5 -cm -long pa rt o f the in tra c ran ia l op tic ne rve and op tic ch ia sm(fig . 8 ). Im ag ing in the co rona l and transax ia l p lanes a lsocons is ten tly show ed good v isua liz a tion o f the op tic ch ia sm .W hen the ch ia sm was in trin s ic a lly in vo lved w ith tum or, theex tent o f tum o rous in vo lvem en t w as be tte r app rec ia ted byapp lica tion o f m u ltip lana r im ag ing (fig . 9 ). A com bina tion o ftra ns ax ia l, co ron a l, an d sag itta l p ro je c tions c lea r ly dem on -s tra ted the in vo lvem en t o f the in tra cran ia l op tic ne rve . S ag itta land co rona l pro je c tions dem onstra ted the supe rio r and in fe -r io r e x ten t o f the tum o r, w h ile in vo lvem en t o f the op tic tra c tspos ter io r ly cou ld be app rec ia ted on the transax ia l p ro je c tion .M R sag itta l p ro je c tions a lso prov ided add itiona l in fo rm a tionconce rn ing pa tho log ic a lte ra tion of the op tic ne rve and ch iasmby m asses erod ing th rough the floo r o f the an te rio r c ran ia lfo ssa (fig . 10 ).


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F ig . 7 .-O rb ita l p se ud otu mo r. SE 500 /30 . A , C oro na l image . G oo d d elin ea ti on o f op tic n erve ( a r r ow-heads) fro m la rg e in fla mm ato ry m ass superio r ly by la ye r o f h ig h -s ig na l fa t be tween m ass and ne rve . B ,Sag i t t a l im ag e. G oo d d elin ea tio n o f o ptic ne rve ( a r r owheads ) from la rge in flam ma to ry m as s sepa ra te d byla ye r o f h ig h-s ig na l fa t.

1018 EDW ARDS ET AL . AJR:144 , M ay 1985

F ig . 5 .-C ho ro id a l m e la nom a . A , Con t r as t - en -han ced C T scan show s 4 mm hype rd en se le s io n inmed ia l quad ra n t o f le ft g lo b e th a t cou ld rep res en te ithe r h em o rrha ge or tum o r. Le s io n had sam e ap -pea ra n ce on unenhan ced C T . B . SE 500 /30 . The 4m m m elanom a is w ell im aged in m e dia l q ua dran t o fl e ft g l ob e .

F ig . 6 .-M e ta s ta tic m e lan om a. SE 500 /30 . A ,T ra nsax ia l im age . La rge tum o r m ass (t) s itua te d m e-d ia l to rig ht op t ic ne rve an d g lo be i s w ell d elin ea te dan d d is ting uish ed fro m a djac en t op tic n erve b eca useo f d i ff e re n c e in s ig na l in te ns ity b e tw een m ass andnerve . Me lanoma is o f h igh s ign a l b ecau se o f its sho r tT i , mos t l ik el y p ro d uc ed by he mo rrh ag e in to tu mo r.O p ti c n e rv e is v ery c le arly de l inea ted bo th f rom t umo rm ass a nd retroorbital fa t la te ra l to n er ve . P ro sth eticde vice is in p lac e in le ft o rb it. B , C oron al im age a ga indemons t ra te s la rge h igh -s ign a l tum or m ass (t) in m e-d ia l p a rt o f righ t g lo be , p rod uc in g m arked la te ra lde via tio n an d proptos is o f rig ht g lo be . M ed ia l re ctusand in fe rio r rec tu s m usc les canno t b e d is t ingu is hedfro m th is m as s.

F ig . 8 . -No rma l sagit tal S E 5 00 /3 0 im ag e. Exce l -len t ana tom ic de l inea t ion of in tra cra nia l p ar t o f o pt icnerv e and op tic ch ia sm . T he 1 .0 - i .5 -cm -lon g par t ofop t ic ner ve (a r rows) can be w ell se e n i n s u pr a se l la rr eg io n , f or m in g o ptic c hi as m p os te rio rly a tjun ctio n o fan te r io r w all a nd flo or o f th ird v en tric le . S ig na l in ten -sity of op tic n e rv e an d ch iasm is s im ila r to th a t ofa dja ce nt n or ma l b ra in t iss ue , b u t is w e ll d e fin ed be -c au se o f g oo d c on tr as t w it h l ow -s ig n al ce reb rosp ina lflu id a dja ce nt to it.

Discuss ionC T is w e ll k nown to be an e ffec tiv e and re liab le m eans o f

exam in ing the o rb it [7 - i 3 ]. R epo rts on the e fficacy o f MR in

d iagnos ing ce reb ra l and o rb ita l abno rm a litie s have been en -cou rag ing [1 4 -21 ]. A pp lic a tion o f MR to the o rb it is a ttra c tivein tha t m u ltip lana r te chn iques m ay be pe rfo rm ed , p rov id ingadd itiona l in fo rm a tion w ithou t add itiona l pos ition ing ; and the


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A BF ig . 9 .-O p tic g liom a . A , T ra nsa x ia l SE 500 /3 0 im age . G ood ana tomic d efin it io n o f o ptic ch ias m(a r rowheads) , w h ich is en larged by tum or in filtra tion . G oo d co ntra st d isc rim in atio n be tw een o ptic ch ias m

an d su rro un din g low -s ign al c e re bro sp ina l f lu id in s up ras e lla r a s te rn . O ptic trac ts w ere seen w ell, a ndap pea re d n orm al on tran sa xia l im ag e ju st s upe rio r to th is c ut. B , S ag itta l S E 2 00 0/9 0 im ag e. E xte n t o ftum oro u s invo lv em en t o f in tra cra nia l p ar t o f o ptic ne rve and op tic ch iasm (a r rows) is seen to goodadvan tage , w ith m a rk ed ly th ic kened and en la rge d op tic ne rve and ch ia sm . S ig na l in te ns ity of tum or iss lig htly inc rea se d d ue to p ro lo ng ed T 2.

F ig . 1 0.-E xtrin sic m a ss a lte rin g o pt ic a pp ara tu s.Sag i t t a l S E 5 00 /3 0 image . Larg e tum or mas s (t),pa tho log ic a l l y co nfirm ed as o ss ify ing fib rom a, fillss ph en o id s in us , e ro de s th rou gh flo o r of a n te r io r c ra -n ia l fos sa , a n d encroa ches on op tic n e rve a t po in t( a r r ow-head) jus t a nte rio r a nd s up erio r t o s al le tur -c ica.

A JR :144 , M ay 1985 MR IM AG ING OF THE ORB IT 1019

risks o f ion iz ing rad ia tion and con tra s t adm in is tra tion a ree lim ina ted . In ou r ser ie s , MR c lea rly dem onstra ted the orb ita labno rm a lity in a ll bu t tw o cases ; in seve ra l cases , M R ap -pea red m o re sens itive than C T in p rov id ing add itiona l in fo r-m a tion conce rn ing the le s ions . M uch o f the in fo rm a tion addedby M R w as p rov ided by its ab ility to d ire c tly p roduce im agesin the co rona l and sag itta l p ro je c tions w ithou t add itiona l p0-s itio n ing o f the patien t, a ffo rd ing exce llen t de ta il conce rn inga lte ra tion o f the op tic ch ia sm and op tic ne rve by pa tho log icm asses . M R appeared to be m o re sens itive in de tec ting sm a lla reas o f subacu te and ch ron ic hem o rrhage w ith in so ft- t issuem asses in the o rb it, w h ich m ay be im po rtan t in m anagem en to f the pa tien t. In our pa tien t w ith K im u ra d isease , the a reaso f hem o rrhage w ith in the o rb ita l m ass tha t we re de tec tedon ly w ith M R suggested tha t the m ass had a ve ry vascu la rna tu re . B iopsy dem onstra ted an ex trem e deg ree o f ang ioge-nes is assoc ia ted w ith an in flamm a to ry in filtra te , and subse -quen t the rapy cons is ting o f com p le te loca l su rg ica l e xc is ionw as ins titu ted . P atho logy con firm ed a reas o f subacu te andch ron ic hem orrhage in the h igh ly vascu la r m ass . O n the othe rhand , as show n by D eLaP az e t a l. [6 ], ve ry recen t hem o rrhagem ay go unde tec ted on M R s ince it m ay show s igna l in tens itys im ila r to no rm a l b ra in tis sue , and in these cases C T m ay bem o re sens itive . M R appea rs to be m o re sens itiv e than CT inde tec ting vascu la r ischem ia o f the g lobe , w ith s igna l in tens ityin c reas ing in the v itreous as it undergoes lique fac tion second -a ry to ischem ia ; as a resu lt the v itreous has a long T2 re la tiveto the no rm al v itreous .

M ost o f the tum o rs in ou r se rie s show ed long T i and longT2 cha rac te r is tics , w ith the gene ra l e xcep tion o f m e lanom asand m ost m en ing iom as . T he fou r m e lanom as in ou r se rie susua lly appea red to have re la tive ly h igh s igna l on the T i -w e igh ted im ages , in con tra s t to m ost o the r tum o rs , w h ichhad re la tive ly long T i s . In c rease in s igna l w as no ted in th reeo f fou r m e lanom as on the T 2 -w e igh ted im ages, w h ile in oneo f the in traocu la r m e lanom as, the re w as low s igna l from thele s ion . S in ce th ree o f fou r m e lanom as show ed a sho rt T i and

long 12 , un like the e ffe c t o f a pa ram agne tic subs tance suchas m e lan in , they appea r to be com pa rab le to othe r subacu teo r ch ron ic hem o rrhag ic tissue in s igna l cha rac te ris tic s . Theone m e lanom a tha t dem onstra ted sho rt T i and sho rt T2 d idso m os t like ly because o f the pa ram agne tic e ffe c ts o f m e lan in .In a ll fou r cases o f m elanom a , C T showed a nonenhanc ing ,h yperdense le s io n tha t co u ld h ave been in te rp re ted as e ithe rtum o r o r hem o rrhage . T he m en ing iom as cons is ted o f oneop tic -ne rve -shea th m en ing iom a and th ree spheno id -w ing m e -n ing iom as w ith ex tens ion in to the o rb it. In gene ra l, theseshow ed low s ig na l o n bo th T i - an d T2 -w eig h ted im ages ,a lthough a ll w e re de tec ted w ith bo th M R and CT . T he op tic -ne rve -shea th m en ing iom a w as in the apex o f the r igh t o rb itand ex tended in to the op tic fo ram en ; sepa ra tion o f the tum o rfrom the op tic ne rve w as no t poss ib le , a s s igna l cha rac te r is -tic s w e re s im ila r. T he op tic -ne rve g liom a w as con fined to thein tra cran ia l op tic ne rve and ch iasm , had long T i and long T 2cha rac te r is tics , and appeared s lig h tly b rig h te r o n the T2 -w e ig h ted im ages than the no rm a l ch iasm be cau se o f its long12 ch a rac te r is tics . O ur expe rien ce w as s im ila r to tha t o fD an ie ls e t a l. [21 J in tha t the op tic -ne rve g liom as and op tic -ne rve m en ing iom as p roduced re la tive ly weak s igna ls tha tm ade them d ifficu lt to d is tingu ish from the no rm a l op tic ne rve .

The o the r tum o rs in ou r se rie s in c luded tw o lym phom as ,tw o m etas ta tic adenoca rc inom as, and th ree tum ors ex tend -ing d ire c tly in to the o rb it from ad jacen t pa ranasa l s inuses ,pa tho log ica lly con firm ed as m ucoep ide rm o id ca rc inom a ,squam ous-ce ll ca rc inom a , and oss ify ing fib rom a , a ll o f w h ichhad bo th long T i and long 12 cha rac te ris tics . A ll o f thesem ass les ions w e re de tec ted w ith bo th M R and CT .

In ou r se ries , M R exh ib ited th ree lim ita tions in im ag ing theorb i t : (1 ) its inab ility to im age ca lc if ica tio ns w ith in ana tom ics tru c tu res o r in m asses ; (2 ) the la ck o f con tra s t d isc r im ina tionbe tw een the h igh -s igna l re trobu lba r fa t and sm a ll hem o r-rhages w ith s im ila r h igh s igna l in tens ity ; and (3 ) the la ck o fcontras t be tween the cortic a l bony m a rg in s o f the o rb it andad jacen t a ir in the e thm o id and m ax illa ry s inuses , w h ich m ade


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1020 EDW ARDS ET A L . AJR: i44 , M ay 1985

eva lua tion o f the floo r and m ed ia l w a ll o f the orb it d iffic u lt,even though the la te ra l and supe rio r w a lls o f the o rb it cou ldbe ad equa te ly exam in ed due to good con tra s t be tw een thebone and ad jacen t so ft t issue o r fa t.

In conc lu s ion , a lthough MR s till h as lim ita tions as com pa redw ith CT , it can p rov ide add itiona l in fo rm a tion in exam ina tiono f the o rb it tha t m ay be im po rtan t in ea r ly d iagnos is . Fu rthe rte chn ica l im p rovem en ts , in c lud ing su rfa ce co ils [22 , 23 ] ap -p lied c lo se to the o rb its and the ava ilab ility o f th inne r sec tions[24 , 2 5 ], w ill no doub t in c rease the in fo rm a tion ob ta ined .

REFERENCES1 . B rad ley W G, T osteson H . B as ic phys ics o f NM A . In : K au fm an L ,

C rooks LE , M argu lis AR , eds . N uc le a r m agne tic re so nan ce im -ag in g in m ed ic in e. N ew Y ork : Igaku -S ho in , 1981 :11 -29

2 . C rooks LE . O ve rv iew o f NM R im ag ing techn iques . In : K au fm anL , C rooks LE , M a rgu lis A R , eds . N uc le a r m agne tic re so nan ceim ag in g in m ed ic ine . N ew Y ork : Igaku -S ho in , 1981 :30 -52

3. Pyke t t IL , N ew house JH , B uonanno FS , e t a l. P rinc ip les o fn uc le ar m ag ne tic re so na nc e im ag in g. Rad io logy 1 98 2;1 43 : 1 57 -16 84 . B rad le y W G , N ew ton TH , C rooks LE . P hys ica l p rin c ip le s o fnuc lear m agne tic re sonance . In : N ew to n TH , P o tts DG , e ds .A dvan ced im ag in g techn iq ue s . San Anse lm o, C A : C lavade l,1983:15 -62

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6 . D eLaPaz R L , N ew PFJ , B uonanno FS , e t a l. N M R im ag ing o fi nt ra cr an ia l h em o rr ha ge . J C om pu t A s s is t T om ogr 1984 ;8 :599 -60 7

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9 . W eins te in M A , M od ic M T , R is iu s B , O uchesneau PM , Be rlin A J .V isua liza tion of the a rte rie s , ve in s , and ne rves o f the o rb it b yse cto r co mp ute d to mo gra ph y. Rad io logy 1 98 1; 1 3 8: 83 -8 7

10 . N ugen t R A , R oo tm an J, Robe rtson W D, Lapo in te JS , Ha rrisonP B. A cu te orb ita l p seudo tum ors : c la ss ifica tion and C T fea tu res .

AJNR 1981;2:431-436, AJR 1981;137:957-9621 1 . Fo rb e s GS , Ea rn est F IV , W aIle r R R . Com pu ted tom ograp hy o f

o rb ita l tum o rs , inc lu d in g la te -ge ne ra tion scan n in g tech n iq ue s .Radiology 1982;142:387-394

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14 . B ydde r GM , S te ine r R E , Y oung IA , e t a l. C lin ica l NM R im ag ingo f the b ra in : 140 cases . AJNR 1982 ;3 :459 -480 , AJR1 98 2;1 39 :2 1 5 -2 36

1 5. B ran t-Zaw adzk i M , Dav is P L , C rooks LE , e t a l. NM R dem onstra -t ion o f ce re b ra l a bno rm a lities : c om pa riso n w ith C T . AJNR1 9 83 ; 4: 1 1 7 -1 24 , AJR 1983;140:847-854

1 6 . S ipponen JT , K as te M , Ke tonen L , S epponen RE , K a tevuo K ,S ivu la A . Ser ia l nu c le a r m agne tic reso na nce (NM R ) im ag in g inpa tien ts w ith ce reb ra l in fa rc tion . J C om pu t A ss is t T om og r1983;7 :585 -589

17 . H aw kes AC , H o lland G N , M oo re W S , R iz k S , W o rth ing ton B S ,K ean D M. NM R im ag ing in the eva lua tion o fo rb ita l tum ors . AJNR1983 ;4 :254 -256

18 . H an JS , B enson JE , B ons te lle CT , A lfid i R J , K au fm an B , Lev ineM . M agne tic re sonance im ag ing o f the o rb it: a p re lim ina ry ex-per ience . Rad io logy 1984 ;150 :755 -759

19 . S obe l O F , M ills CM , C ha r 0 , e t a l. NM R o f the no rm a l andpa tho log ic eye and orbit. AJNR 1984 ;5 :345 -350 .

20 . B ran t-Zaw adzk i M , B a rtkow sk i HM , O rtendah l D A , e t a l. NM Rin e xpe rim en ta l ce re b ra l ed em a : va lu e o f T i a n d T2 ca lcu la tio ns .AJNR 1 98 4;5 : 1 25 -1 29 .

21 . Dan ie ls D L , H erfk in s A , G age r W E , e t a l. M agne tic reso na nceim ag ing o fthe op tic ne rves and ch iasm . Rad io logy 1 98 4; 1 5 2: 79 -83

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25 . C rooks LE , M ills CM , Hoenn inge r JC , e t a l. Th in sec tion M R I a t0 .35 T . P resen ted a t the annua l m ee ting o f the Am erican Soc ie tyo f N eu ro rad io logy , B os ton , June 1984

magnetic resonance imaging of the orbit

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