carotid blood flow

8/13/2019 Carotid Blood Flow

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B lo o d F lo w in th e C a ro tid A rte rie s :Q ua n tif ic a tio n b y U s in g P h a s e -S e n s it iv eM R Im ag in g

P ete r B en de l1 2E dw ard B uo noco re3

A ndre as B ock isch4M y r w o o d C . B es oz zi3

R e ce ived S e p te m b er 2 3 , 1 988 ; a cc ep ted a fte rre v is io n F e bru a ry 3 , 1 98 9 .

I Ins t itu te o f B iom ed ica l Im a g ing , U n iv e rs ity o fT en ne sse e M ed ic a l C en te r, 1 9 24 A lco a H w y.,K no xv ille , T N 3 792 0 a nd E lsc in t M ag ne tic R eso -n an ce Im a gin g C en te r, H erz ila , Is ra el.

2 P re sen t ad d ress : D ep t. o f Iso top e R es ea rch ,T h e W e izm an n Ins titu te o f S c ie nc e , R e h o v o t761 00 , Is rae l. A dd res s rep rin t requ es ts to P .B e n d e l .

3 D e p a rt m e n t o f R ad io lo gy , U nive rs ity o f T e nne s-see M ed ica l C en te r, 1 92 4 A lc oa H w y., K n ox v ille ,T N 3 79 20 .

4 D e pa rtm en t o f C lin ica l an d E x pe rim en ta l N u -c le a r M ed ic in e , U n ive rs ity o f B o nn , S igm un d F re udS tras se 25 , 5 00 0 B o nn 1 , W e st G erm an y. F romM ay to A ug ust 1 9 88 , A . B o ck isch w as a v is it ings c ie n tis t in th e D e p t. o f R ad io lo gy a t th e L k v e rs ityo f T en ne ss ee M ed ic al C en te r. R 1 52 :1 30 7 1 31 0 J un e 1 98 9036 1-80 3x/89 /1 52 6-13 070 A me ric an R oe ntg en R ay S oc ie ty

Th e fe a s ib ility o f M R p h a se -s en s itive im ag in g fo r th e q u an tific a tio n o f b lo o d f lo w inth e c aro tid ar te rie s w a s stu d ie d in tw o nor ma l v o lu n tee rs a n d s ix pa tie n ts w ith c aro tidar tery an d /o r ce re b rov a sc u la r d ise a se . T h e te c hn iq u e c on s is ts o f s en s itiz in g th e p h a seo f th e M R s ig n a l to b lo o d flo w ve lo c ity g a te d to d iffe re n t tim e s in th e c a rd iac c yc le . F lo wveloc it ies an d v o lu m e s w ere m e as u re d b y u s in g tra n s ve rs e p la n es in th e c o m m o n ,in te rn a l, an d e xte rn a l ca ro tid a rte r ie s , an d flo w c u rv e s w e re g e n era te d . M e a su rem en tsm ad e b y u s in g flo w p h a n to m s c o rre la ted w e ll w ith ca lcu la ted re s u lts . T h e M R m ea su re -m en ts y ie ld e d v a lu e s be tween 2 50 a n d 58 0 m I/m m fo r th e to ta l f lo w th ro u g h ea c h o f th ec o m m o n c a ro tid ar te r ies in th e tw o n o r m a l v o lun tee rs . M arke d ly red u c ed flo w (a b o u t5 0% b e lo w n o rm a l) w as d ete c ted in a p a tien t w h o s e arte rio g ra m s h o w ed se ve reo cc lu s io n o f th e in te rna l ca ro tid ar tery . In a se c o nd p a tie n t, w ho h a d a la rg e fro n ta lIn tra c ra n ia l a r te r io ve n o u s m alfo rm a tio n n o te d b y a rte rio g ra p h y , th e M R -q u an tifie d f lo ww a s a b n orm ally h ig h (ab o u t 1 lite r /m m ). In th e rem a in in g fo ur p a tie n ts , th e f in d in g s o np h as e-sen s itiv e q u a n t ific a tio n w e re c o n s is te n t w ith th o s e e xp e cted fro m c lin ica l an do th e r la b o ra to ry s tu d ie s (inc lu d ing a rte r iog rap h y an d so n o g rap h y ).

Th e se p re lim in a ry find in gs s u g g es t th a t M R p h as e m ap p in g m a y b e a fe as ib le to o lfo r th e n on in v as ive q u a nt if ic a tio n o f c aro tid b lo o d flo w .

In o rd e r to e n h a n ce th e va lu e o f M R im a g in g o f th e ca ro tid a rte rie s , a p h a se -se n s itiv e m e th o d o f q u a n tita tiv e a n a lys is o f flo w in th e a x ia l p ro je c tio n w a s a p p lie dto the stu dy o f tw o n o rm a l vo lu n te e rs a n d s ix p a tie n ts w ith c a ro tid a n d /o r c e re b ro -v a scu la r d ise a se . T h e m eth o d u se s a g ra d ie n t-e ch o se q u e n ce w ith a sh o rt T R a n dlo w flip an g le tha t is a pp lied in a ca rd iac -ga te d synch ron ize d c ine m od e . F lowin fo rm a tio n te m p o ra lly re s o lve d o ve r th e ca rd ia c cy c le w a s p ro v id e d [i ]. P re v io u sq u a n tita tive M R flo w -ve lo c ity s tu d ie s [2 -4 ] in h u m a n s h a ve b e e n m ade w ith sp in -e c h o se q u e n ce s w ith o u t te m p o ra l re so lu tio n d u rin g th e ca rd ia c cy c le . O th e r re p o rts[5 , 6 ] in c lu d e c in e m o d e m e a su re m e n ts o f flo w m a d e b y u s ing a n g io g ra p h y [6 ].T h e p u rp o se o f th is re p ort is to v a lid a te th e a cc u ra c y o f p h a se -se n s itiv e im a g in gfo r q uan tita tive flo w in p han tom e xpe rim e n ts a nd its a pp lica tion to th e s tud y o fc aro tid a rte rie s.

M ate ria ls a nd M e th o d sE xp e rim en ts w ere p e rfo rm ed o n a co m me rc ia l w ho le -b o d y G y r e x 2 T T M M R im a ge r, (Elsc int ,

In c ., H erz lia , Is rae l) o p e ra t in g a t 1 .9 T . T h e p u lse tec h n iq u e c o n s is te d o f th e in te rle av edapp l i c a t ion of tw o s equenc es , w h ich d iffe red in th e am o u n t o f p ha se -ve loc ity en co d in g a lon gt he d ire cti on o f th e s lice -s e le c t g rad ie n t (a ls o th e p r in c ip a l d ire c tio n o f th e flo w ). In on e sca n ,th e g rad ie n t w a ve fo rm s com pe n sa te d fo r p ha se s h ifts in trod uc ed by flow a t c on s tan t ve lo c ity ,w h e re a s in the a lte rna te s eq ue nce , a p ha se p rop o r tion a l to ve lo c ity w a s in tro du ce d . B o ths equenc es w ere p h as e co m p en sa te d fo r flo w a lo n g th e v iew - o r freq u e n c y-en c o d in g d irec tio n .

E xc ita tio n p ulse s w ith 3 0 {1 76 }lip a n g le w e re a p p lie d w ith T R = 30 m se c, a nd th e s ign a l w asde tec ted w ith T E = 1 8 m se c . T h e in cre m en t o f th e p h a s e -e n co d in g g ra d ie n t w a s tr ig g e re db y th e h e a rtb e at. B e ca u se th e ve lo c ity m ea su rem en ts a re d e rive d fro m d iffe re n ce im ag e sinvo lv ing tw o success ive sc an s , a ve lo c ity m eas u re m en t e ve ry 6 0 m se c th ro u g h th e c a rd ia c


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i 3 08 B E N D E L E T A L . A JR :15 2, Ju ne 1 989

c yc le w as o b ta in e d . T he to ta l m ea su rem en t tim e fo r a 2 5 6 x 2 56a cq u is itio n w as a b ou t 5 m m , de p en d ing on th e h ea rt ra te o f th ep a tien t. S lice w id th w a s 6 m m , fie ld o f v ie w w as 2 2 c m , an d ve lo c itye nc od ing w as 3 {17 6 } /cm /se c . S ign a ls w ere d e tec ted b y the s tan da rds p ine co il o f th e s ys tem .

P ha se in ten s ities w e re co rre c te d b y a s im p le lin e a r so ftw a re op -e ra tio n w ith va r ia b les de riv ed from th e re q u irem en t tha t th e in te ns itys ho u ld hav e an a ve rag e o f z e ro in a re as c on ta in ing on ly no n flo w ingm ate ria l. F lo w d ire c tio ns a n d ve lo c itie s w e re re ad d irec tly o ff th eim a ge s on a p ixe l-by -p ixe l ba s is , and the p rop o r tion a li ty con s tan tb e tw e e n v e lo c ity a n d p h a s e w a s d e te rm in e d b y flo w -ph a n to m ca li-b ra t ion s , d esc rib ed la te r in the tex t . T he p ha se im ag es w e re c o rre -la ted w ith the m a gn itu de im a ge s , an d a p ha se va lue o f z e ro w asa ss ig ne d to a ll p ixe ls w h o se m ag n itud e in ten s ity w as b e low a ce rta inth resho ld .

V o lu m e flow ra te s w e re d e rive d by d ra w in g a re g ion o f in te res ta ro un d th e ves se l. T h e a re a c on ta ine d in th e re g ion w a s m u ltip lie db y th e a ve ra ge im ag e in ten s ity . T h e pro du c t o f th e se tw o va luesy ie ld ed the vo lum e flo w ra te .Sub jec t s

T w o yo un g , he a lthy v o lun tee rs a nd s ix p a tie n ts w ith ca ro tid a r te rys ten os is o r va rio us de grees o f in trac e reb ra l vas cu la r d ise as es w eres tud ied (T ab le 1 ). O f the s ix p a tie n ts , tw o ha d ca ro tid a rte ry o cc lus ived is ea se , o n e d iag no se d b y a rte rio g ra p hy a n d the o th e r by ca ro tidso n og ra ph y a n d D o pp le r te ch n iqu e . T h e re m a in in g fo u r pa tie n ts ha dn o e v id en ce o f c a ro tid -a r te ry na rro w ing b y a rte rio g rap hy . O f the sefo u r pa tien ts , tw o h ad a d iag nos is o f a rem ote s tro ke , an d e ac h ha dn orm a l c a ro tid a nd ce reb ra l a ng io g ram s an d w a s c lin ica lly n o rm a l. O fth e re m a in in g tw o p a tie n ts , on e ha d a la rge a rte riove no us m a lfo r-m atio n an d th e o th e r w a s eva lu a te d fo r n eck p a in a n d fo un d to b enor ma l b y a rte rio gra ph y a nd fu rth er c lin ica l a sse ssm en t.D at a C olle ctio n

A su rve y co ro n a l M R im a g e w a s o b ta in e d to ch o o se th e p o s itio no f th e tran sve rse p la ne s u sed fo r th e an a lys is o f b lo od flo w in the

T A B L E 1: C a ro t id Artery F lo w R ate s (m I/m in )

co m m o n , in te rna l, o r ex te rn a l ca ro tid a rte ries . In th ese tw o p la n e s ,p h a se m ap p in g w a s p e rfo rm e d , a s d e s cr ib e d . A n a lys is o f th e d a tay ie lde d th e a r te ria l f lo w a t e ig h t to 1 1 p o in ts o f th e h e art c yc le , w h ic hm a d e it p os s ib le to c a lc u la te th e to ta l flo w by in te g ra tin g the a reau n d e r th e flo w -tim e g ra p h , o r b y in te rp re tin g th e line sh a p e o f th eg ra ph its elf.

Calibrat ionM e a surem en ts w ere m a d e by u s ing ph a n to m s in w h ic h co ns ta n t-

ve lo c ity flow w as g en era ted in tu be s an d m e as ure d b y tim ing theflo w in to g ra dua te d c on ta in e rs to c a lib ra te ou r pu lse s equ en ce an dfo r su bse q ue n t da ta p ro ce ss in g . W e tes te d tw o se q u e n ce s th a td iffe re d in the am ou n t o f flow en co d ing . In on e se q ue nc e , th e flo w -i nduc ed p ha se w as 2 {1 76 }/cm /se c,a n d in th e o th e r (w h ich w a s th ese q u e n ce u se d in th e c a ro tid a rte ry s tu d y), th e p h a se e n co d in g b yf lo w w as 3 {1 76 }/c m/s ec .

Resul tsT h e re su lts o fth e flo w -p h a n to m c a lib ra tio n s tu d y a re sh o w n

in F ig u re i . A s tra ig h t-line co rre la t ion w as pro duced w h enpha se in ten s ity o fthe s ign a l w as p lo tted aga ins t the m ea sure dve loc ity o f flow in th e p han tom .

F ig u re 2 illu s tra te s typ ica l m a g n itu d e im a g e s a n d d iffe r-e nc e -p h a s e m a p s o f o n e o f th e n o rm a l vo lun te e rs . F ig u re 3sho w s the flow curves fo r one o f these vo lun tee rs . F igu re s 4a nd 5 s h o w flo w cu rve s fo r tw o o the r su b je c ts , as ind ica tedin th e ca p tio n s . T h e p a tie n ts re le va n t d a ta a n d th e to ta lin te g ra te d flo w vo lu m e s a re s u m m ariz e d in T a b le i.Discuss ion

S e ve ra l M R te c h n iq u e s fo r s tu d y in g th e m orp h o lo g y a n dfu n c tio n o f th e va s cu la r s ys te m h a ve b e e n in trod uce d in th e

In te rna l

(ye s ) G e nd er C lin ica l S ta tusC o m m o n C aro ti d A rte ry C a ro tid

Artery

L e ft R ig h te ft R ig h t Le f t /R igh t

3 2 F R ig h t C V A , n o rm a l ce re b ra lang iog ram

5 6 7 5 7 2 1 .0 2 7 9 2 0 853 M Le ft C V A , se ve re n a rrow -

in g o f le ft IC A , m ild na r-ro w ing o f rig h t IC A

1 71 34 4 0 .5 0 N M 2 4 7

66 F S tro ke 1 0 mon ths a go ,c lin ic ally n orm al

5 02 41 6 1 .2 3 2 9 29 237 M La rge righ t f ron ta l A V M

fro m bo th ca ro tid s,r igh t > le ft9 59 1 1 82 0 .8 1 N D N D

59 M P e rip he ra l v as cu la r d is -e as e , R ig h t IC A, 1 00 %occ lu de d ; Le ft IC A , 80 %oc c luded

3 89 N o flo wdetec ted - - -

38 F T h roa t an d ne ck p a in ; n oce reb ra l va sc u la r d ise as e

2 65 27 5 1 .0 N M 1 652 2 M N o rm a l vo lu n te e r 3 7 3 4 45 0 .8 4 N D N D2 0 F N o rm a l vo lu n te e r 2 9 1 3 1 1 0 .9 4 2 3 1 2 4 9N o t e . - C V A = ce reb ra l va scu la r acc ide n t, IC A = in te m ai c a ro tid a rte ry , A V M = a rte rio ve no us m a ffo rm a tio n, NM =

no t m ea su red , N O = n o t d e te rm i ne d, - = n o f lo w d et ec te d.a E xp erim en ta l un ce r ta in tie s fo r the flo w v o lu m e s in th is ta ble are e s tim ate d a t 4 0 m I/m m.


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1 0 2 0 3 0V .lo c lty in F lo w P h a n to m : cm /se c

F ig . 1 .-C alib ra tio n cu rve o f p h a se-m a p p in g se q u en ce s o n flo w p h an -to m . V ertic al s ca le is a ve rag e in tra lu m ina r p has e In ten s ity in tub e ca rry ingflo w in g w ate r, d e te rm in e d b y d if fe ren c e p h a se m a p p in g , a s d e scr ib ed inte xt. H oriz on ta l co ord in ate s ar e ve lo c i t i es meas ur ed by tim in g d eliv ery o fmeas ur ed v o lu me s th ro ug h th e tu be . D ata a re p re se n te d fo r tw o d i f t e ren tpu ls ing seq ue nc es, w ith c a lc u la ted ve loc ity p ha se e nc od in g o f 3 { 1 76 } /c m / s ec( cir cle s) , a n d 2 { 1 76 }/ cm / se cx), w h ic h are a lso s lopes o f so lid an d d a sh edl in e s , r e sp e c t iv e ly .

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la s t fe w ye a rs [6 -8 ]. M R a n g io g ra p h y a im s to p ro v id e s ta tica n a to m ic im a g e s o f in -p la n e b lo o d flo w o f lo n g s e g m e n ts o fv e sse ls , w h e re a s o th er m e th o d s h a v e b e en d es ig n e d to p ro-v id e fun ctiona l spe c ific qu an tita t ive in fo rm a tion abo u t flo wve loc itie s , vo lum es, a nd d irec tio ns. Q ua n tita tive me a s u re -m e n t o f flo w v e lo c itie s ca n be a ch ie v e d b y so m e s o rt o fin f low-ou t f low ta g g in g te ch n iq u e [2 ] o r b y u s in g p h a s e m e a s-u re m e n ts o n c ro s s-s e c tio n a l ph a s e im a g e s [4 , 9 ].

T h e p ro p o rtio n a lity co n s ta nt b e tw e e n ve lo c ity a n d p h a seas de te rm ine d by ou r techn ique cou ld , in p rinc ip le , b e p re -d ic te d d ire c tly fro m a ca lc u la tio n o f th e g ra d ie n t w a ve fo rm -tim e in teg ra l [9 ]. O th ers h a ve p o in te d o u t th e ne e d fo r c a li-b ra tio ns w ith flow pha n tom s [8 ], so w e co ndu cte d experi-m e n ts to d e te rm in e th e a cc u ra cy o f o u r ca lcu la te d p h a se -s e n s itive tec h n iq u e (F ig . 1 ). U s in g flo w p h a n to m s, w e fo u ndth a t th e m e a su re d flo w e n co d in g o f a g ive n se q u e n ce d idin d e e d d iffe r s lig h tly fro m th e c a lcu la te d p h a se , if th e p h a sew a s ca lcu la ted in a s tra igh tfo rw ard m an ner [9 ]. T h e m ea su red

12 0

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ve rge80P h a s eIntensityD e gr s e s

40

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ig 2 .-M ag n Itu d e an d p h a se -se n -sftive M R s ca n s in n o rm a l v o lu n te er .M ag nitu de (A ) an d z o om ed p has e-d if-fe re nc e im ag e B ) o f o n e ca rd iac fram e(2 8 2 m se c a fte r R w ave ) in o ne v o lu n -tee r . P h as e -d iffe ren c e im ag e w asm ask ed b y a ss ig nin g a p ha se in te ns ityo f ze ro (g ra y ) to a ll p ixe ls w h o s e m a g -n itu de in te ns ity w a s b e lo w a cer taint hr es ho ld . D ir ec tio n o f flo w an d m ag -n i t ude a re d et er m in e d. B oth com moncarot id a n d v er teb ra l a r te r ies (d ark )a n d ju g u la r v e in s (b rig h t) a re w e ll re -s o lv ed a nd v is ua lize d. Degr ee ofb rig htn es s c orr ela te s w ith veloc ity .

d iffe re n c e in v e lo c ity p h a se e n c o d in g b e tw e e n tw o se q u e n c e sw ith s lig h tly d iffe re n t c o m p e n sa tin g g ra d ie n ts co u ld b e p re -d ic te d a cc u ra te ly by th e s im ple a n a ly tica l c a lcu la tio n .

V a lid a tio n o f o u r p h a s e -s e ns itive te ch n iq u e o f d e te rm in in gb lo o d flo w is e v id e n ce d b y n o tin g th a t th e to ta l in te g ra te dflo w vo lum e s o f no rm a l vo lun te e rs (T ab le 1 ) a re w e ll w ith inth e b ro ad ra n g e o f no rm a l va lu e s e s ta b lish e d in the lite ra tu reby o th e r m e th o d s [i 0 ]. T h e sh a p e o f th e c u rve s re s e m b le sth e e x p e c te d p h ys io lo g ic p re ss u re c u rv e s [i 1 ], e ve n su g -ge s tin g th e p re se n c e o f a d ic ro tic n o tch . F u rth e r in te rn a lco n s is te n cy o f o u r m e a s u re m e n ts is sh o w n b y co m p a rin g th eflo w ra te s in the co m m o n ca ro tid a rte ry w ith th e s u m o f th era te s in th e in te rn a l a n d e x te rn a l b ra n ch e s fa rth e r d o w n -s tre a m . T h e tw o v a lu e s sh o u ld b e e q u a l, a nd as sh o w n inF ig u re 4 , th e y in d e ed a re w ith in th e lim its o f e xp e rim e n ta luncerta in ty .

O u r d a ta re fle c t vo lu m e flo w ra te s , th a t is , th e p ro d u c t o flin e a r ve lo c itie s a n d cro ss-se c tio n a l a re a s . W e fo u n d th e seva lu e s to b e m o re p re c ise ( in te rm s o f e va lu a tion b y d iffe re n to b se rve rs ) th a n th e va lu e s o f a ve ra ge v e lo c ity a n d c ro s s-se c tion a l a re a se p a ra te ly , w h ich te n d to b e m o re d e p e n d e n to n th e te n d e n cy o f a n in d iv id u a l to d ra w th e co n to u r re g io no f in te re s t a ro u n d th e ve ss e l.

A p oss ib le lim ita tio n o f the accu racy o f the c lin ica l da ta m a ybe im p o se d b y a cce le ra tion , w h ic h w a s n o t p re s e n t in o u rflo w -p h a n to m c a lib ra tio n . A cce lera tio n c a n ca u se p h a se s h iftsno t co n s id e red in o u r a n a lys is . A ro u g h ca lc u la tio n u s in gtyp ica l ra te s o f ve lo c ity in c re a se o r d e c re a se a n d th e g ra d ie n ttim in g o f o u r p u lse se q u e n ce in d ica te s th a t a n in a cc ura cy o fup to 2 0 % in th e e s tim a te d flo w ra te co u ld b e ca u s e d b y th iso m iss io n d u rin g p e a k a cc e le ra tio n . T h e e rro r w o u ld ca u seo ve re s tim a tion o f th e ra te d ur in g a cc e le ra tio n a n d u n d e re s ti-m ation du rin g de ce le ra tio n . T h e ove ra ll e ffe c t m a y s im p ly b ea s lig h t te m p o ra l s h ift o f th e flo w -ra te cu rve to th e rig h t. T h isw o u ld p ro d u ce little e ffe c t o n th e in te g ra te d to ta l flo w vo lu m ea n d is p ro b a b ly o f n o c lin ica l s ig n ifica n ce .

In th e s tu d ie s o f p a tie n ts w ith n o rm a l ca ro tid arte n o g ra p h ya n d s tro ke d u e to in tra c e re b ra l va s cu la r o cc lu s io n , w e fo u n dth a t th e ca ro tid flo w w a s e sse n tia lly n o rm a l. T h e p ea k , h o w -e ve r, w a s le ss p ro n ou n c e d th a n in th e n o rm a l vo lu n tee rs (F ig .4 ), p o s s ib ly b ec a u se th e p a tie n ts w e re o ld e r th an th e vo lu n-te a rs . T h e ra tio s o f th e flo w ra te s b e tw e e n le ft a n d rig h tca ro tid a rte rie s in th e p a tie n ts w e re s im ila r to th e ra tio sca lcu la te d fo r th e v o lu n te e rs . In th e p a tie n t w ith in tra ce re b ra l


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V o l u m .f lo w ra tem I /sec io

00 0 1 0 2 0 3 0 4 0 5 0% o f C ard ia c C y c le

A R IO N T C C D IE F T C C

F ig . 3 .-G ra ph sh o w ing ca lcu la ted flow v o lu m e ra te v s tim e fram e in aca rd ia c cyc le fo r 22 -ye ar-o ld m ale vo lu nte er . S olid lin es a re s im ple c o n-nec t ions be tween e xp er im en ta l p oin ts , fo r be t te r v is u a liza tio n o f tim ede pe nde nc e .

12

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420

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C O M M O N C A R O T ID *IP 4T E R N A I+ E X T E R N A L (E X T E R N A L

80

U I N T E R N A L

20

15

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0 1 0 20 30 40 5 0 60 o f C a rd iac C yc le

O G H T C A R O T ID A L E F T C A R O T ID

10

8

V o l u m e 6f lo w ra temI/sec

2

F ig . 4 .-G rap h s h o w in g flo w v o lu m e ra tes o f rig h t co m m o n , in te rn a l,an d ex te rn a l ca ro t id arte ries d e term in e d b y p h a se-se n s itiv e M R s ca n n in gin a 6 6 -y ea r-o ld w o m an w ith h is to ry o f a re m o te s tro ke a n d n o rm al a rte ri-o g ra p h y . N o te th a t ca lcu la ted s u m o f e x te rn a l an d In te rn a l c u rve s ise qu iva le n t to m ea su red flow curv e o f righ t c o m m o n c aro tid ar te ry . N o tealso lo w er a n d fla tte n ed p e ak o f c u rve s a s c o m p a re d w ith th a t o f 22 -ye ar-o ld vo lu n te er in F ig . 3 .

a rte r io ve n o u s m alfo rm atio n , ca ro tid a rte ry flo w w a s in cre a se dco n s id e ra b ly . T h e flo w v o lu m e w a s h ig h e r o n th e r ig h t s id e ,a s w o u ld b e e xp e c te d fro m th e a rte r io g ra p h ic fin d in gs .

O ur in ve s tig a tio n s o f th e tw o p a tie n ts w ith se ve re c a ro tids te n o s is w e re in a cco rd w ith th e a rter io g ra p h ic d ia g n o s is . Ino n e p a tie n t, a rte r io g ra p h y sh o w e d 9 0 % s te n o s is in th e le ftin te rn a l ca ro tid a rte ry a n d to ta l o cc lu s io n on th e righ t s id e .W ith M R p h a s e m ap p in g , n o flo w w as d e te c te d in e ith e r th er ig h t o r le ft in te rn a l ca ro tid arte r ie s . A t th e le v e l o f th e co m m o nca ro tid a rte r ie s , n o rm a l flo w w as m e asu re d in th e le ft co m m onca ro tid arte ry . F lo w in the le ft in te rn a l ca ro tid a rte ry c o u ld n o tbe de tec ted b y M R pha se m ap p in g , m ost like ly because o ftu rb u le n c e d u e to th e se v e re s te n o s is . T u rb u le n c e m a k e sp h a se a n a ly s is o f flo w im p o ss ib le . A b se n c e o f a n y e n h a n ce ds ig n a l fro m th e ve s se l o n th e m a g n itu d e im a g e s c o rro b o ra te dth e p re se n ce of tu rb u le n t flo w . O n th e rig h t s id e , n o flo w w asd e te c te d in th e co m m o n ca ro tid a rte ry .

In th e o th e r p a tien t w ith ca ro tid a rte ry o cc lu s iv e d ise a s e ,co rre la tio n o f the so n og ra ph ic fin d in gs w ith p ha se m a pp in gw a s a s fo llo w s. M ild o cc lu s io n o f th e r ig h t in te rna l c a ro tida rte ry a n d n e a rly to ta l o cc lu s io n o f th e le ft in te rn a l ca ro tida rte ry w e re fo u n d b y so n o g ra p h y . M R p h as e m a pp in g m d i-ca te d n o rm a l to ta l flo w in th e r ig h t c o m m on c a ro tid a rte ry a n d

F ig . 5 .-G ra ph sh ow in g com m o n caro tid a rte ry vo lu m e flo w ra te s in a5 3-y e ar -o ld m an w ho h a d s ev e re na rro w in g o f le f t an d m ild n a rro w in g o frig h t in te rn a l caro t id a rte rie s . F lo w -ra te ra t io o f rig h t to le f t co m mo n ca ro t ida rte rie s w as 2 :1 .

re d u c e d flo w in th e le ft c o m m o n ca ro tid a rte ry w ith a n a b n o r-m a l r ig h t/le ft ra tio o f 2 .0 (F ig . 5).

In s um m ary , a lth o u g h o n ly a lim ite d n u m b e r o f p a tie n tsh a ve b e e n s tu d ie d , w e fo u n d th a t a cc u ra te m e a su re m e n t o fb lo o d flow b y M R p h a se m a p p in g is fe a s ib le in ca ro tid a rte r ie sw ith n o rm a l flo w . A p rinc ip a l lim ita tio n o f th e te c h n iq u e is th elo s s o f s ig n a l in tu rb u le n t flo w , w h e th e r s lo w o r ra p id . T h isp ro b le m m a y b e o v e rco m e by m e a su rin g flo w p ro x im a lly o rd is ta lly to th e re g io n s o f tu rb u le n t flo w . B e ca u s e th e p la n e sd e te c te d b y M R e a s ily ca n b e o rie n te d a t a n y a n g le a n dd e te c tio n ca n re a ch a n y d ep th w ith in th e b o d y , M R p h a sem a p p in g o f flo w ra te s m a y b e co m e p a rticu la rly va lu a b le ind ee p- ly ing v ess e ls (e .g ., re n a l o r m e se n te r ic a rte r ie s ), w h icha re n o t re a d ily a cc e ss ib le b y o th e r te ch n iq u e s (e .g ., s o n o g -ra p h y ). A lth o u g h th e m o rp h o lo g ic in fo rm a tio n p ro v id e d b y M Rim a g in g m a y n o t b e a s fle x ib le a s th a t p ro v id e d b y d ig ita lsu b s tra c tio n a n g io g ra p h y , th e M R e x a m in a tio n d e s cr ib e dh e re co m b in e s a d e ta ile d a n a to m ic im a g e w ith q u a n tita tivefu n c tio n a l in fo rm a tio n , w ith o u t th e u se o f co n tra s t a g e n ts .

R E F E R E N C E S1 . N ay le r G L, F irm in O N, L ong mo re O B. B loo d flo w im ag ing by c ine m ag ne tic

r es onanc e . J C om pu t s s is t T om ogr 1986 ;10 :715 -7222 . S in g e r JR . C ro o ks LE . N uc lea r m ag ne tic re so nan ce b lood flo w m eas ure -

m e n ts in the h um an b ra in . Sc ienc e 1 98 3;2 21 :6 54 -6 563 . F e m n be rg D A , C ro oks LE , H oe nn ing e r J , A rak aw a M , W a tts J . P u ls a tile

b lo od ve loc ity in hum an ar te r ies d is p la yed by m agne tic re so na nce im ag ing .Rad io logy 1 9 84 ;1 5 3 :1 7 7- 18 0

4 . B ry an t O J, P a yn e J A , F irm in O N , L on gm ore O B . M ea surem en t o f flo w w ithN MR im ag in g u s ing a g ra d ien t pu lse a nd p ha se d iffe re nc e te chn iq u e . JC o m pu t ss is t T om og r 1984 ;8 :588 -593

5 . F irm in O N, N ay le r G L, K lip s te in R H, Under wood S R. R ees R SO , L on gm oreO B . In v iv o va lid a tion o f M R ve loc ity im a g in g . J C om pu t s s is t T o m o gr1 98 7; 1 1 : 75 1 7 56

6 . W a lke r M F , S ou za S P , O u m ou lin C L . Q ua n t ita t ive f low m ea su rem e n t inph ase c on tras t M R a ng iog rap hy . J C om pu t ss is t T o m o gr 1 98 8;1 2 :304- 313

7 . S in ge r JR . B lo od flo w ra tes b y n uc le ar m agn etic re son ance m eas ure me nts . ien e 1 9 59 ;1 3 0: 1 6 52 -1 6 53

8 . Le nz G W , H a ac ke E M , M a sa ryk T J , La ub G . In -p la ne v asc u la r im ag ing :p uls e s eq ue nc e d es ig n a nd s tr ate gy . Rad io logy 1988 ;166 :875 -882

9 . M o ran P R , M ora n R A , K ars tae d t M B . V er ific a tio n a nd eva lu a tio n o f in te rn a lflo w a nd m otio n. Rad io logy 1985; 1 54 :433 - 441

10 . A ckroyd N , G ill R , G riffi ths K , K o ss o ff G , A pp leb e rg M . Q u an tita tiv ec om m on c aro tid a rte ry b loo d f low : p red ic tion o f in te rn al ca ro tid ar terys tenos is . J V a sc S u rg 1986 ;3 :846 -853

1 1 . B u rto n A C. P hys io lo gy an d b io ph ys ics o f the c ircu la t ion 2 nd e d. C hic ag o:Y ea r B ock M ed ica l, 1 9 7 2

carotid blood flow

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