CA2002051A1

CA2002051A1 - Device for interfacing mri with other imaging modalities

Info

Publication number: CA2002051A1
Application number: CA002002051A
Authority: CA
Inventors: William L. Giese
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-11-03
Filing date: 1989-11-02
Publication date: 1990-05-03
Also published as: JPH03502658A; AU638953B2; WO1990005313A1; EP0409920A1; AU4620489A

Abstract

ABSTRACT
A grid system for interfacing MRI with other imaging modalities. The system includes a grid of contrast material which is compatible with MRI and other imaging modalities and a means to reproducibly position the subject in relation to the grid. The grid system is also used to plan radiotherapy and surgical biopsy procedures.

Description

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~VI~ ~OR I~ O~ H~
IN~ ~OD~ IB~
~ECHNICA~ ARE~
The inven~ion xalat~ to the are~ o~ d~agnoRti~ n~ and more speci~icall~ to a me~hod and devicQ ~or inter~aalng MRI with variou~
o~her diagn~stic ima~ing modaliti~ and ~xentment dQvic2.
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S ~IACXGROUND O~ T~E I~VBNq!:l:ON
~ agnetio reson~noe i~aging ~MRI) i5 a ~ecent but axtremely power~ul noninvasive ~iagnosti~ ~ool. MRI utll~zes a co~binat$on o~
a power~ul ~tatic magnetic ~i~ld and radio ~q~ency pulse~ whiah gather in~o~mation concerning ~he location and interrelation o~ atomic ~O nuclei wh~¢h pOBSeSS unpa~ red ~l e~tron ~pin within the body. As hydrogen is th~ most pr~v~l~n~ element to po~e~ unp~ired ~pin, M~X
mainly lmage~ hydrogen lon conç~ntration. Based upon thi~ ~n~orma-tion, a comput~r i~ able to ~ener~te an anatom~ ~ma~e o~ the ~ub~ect~
For partic~lar studie~, MRI h~ a dl~inct adv~n~age over computed 15 tomograp~y ~C~) ~¢an~. Por ~x~mple, $t 1~ pre~en~ly ~',abli~hed tha~
MRI is th~ diagnostic tool o~ ch~ice:in evaluatlng ths p~ster~or ~o~sa, an ana~omical location that i5 poorly visualized by ~r. M~I
is also superior to C~ in delineatiny ext~emity soft-ti~sue tumor~ and primary bone malignanaie~. Whereas cr scan~ a region o~ ~n~eres~ in ~o one plane, M~I perm~ts imaging in any de~ired plan~, ~hus more Qa~ily p~rm~ttin~ multidim~nsional m~pping o~ tumors.
The~e advan~ages o~ M~I maXo ~t attractive ~or u~e ln ~adlatien trea~men~ plunning~ Over ~h~ pa~t ~everal~ ye~ar~, CT has been used ~or ~hi~ purpo~e Qnd has revolutionized ra~ lon treatm~3nt by ma~In~
2S ~va~la~le mo~e det~iled ln~ormation concerntng tumor 'localization than WA~3 evar be~or~ possible: ~Eo Har~ h~ Ro~a c~ the CT Scarlner ~n Planning~ 5~ ~613) ~<ad,~ 0, 1g8~. ) Stlll, as sugges~ced abova, certAin anatom~cal ~tudies are better suited to M~I, and ~hu3, hould potent~ally complemen~ CT in radia~l~n t~ea~men~ planning,.
30 ~ has also been sugge~ted that ~RI ma~ be ~n~rgi~ia wi~h C~ in ~he de~inition o~ tumo~ voluma ~or ~ number of di~a~e sta~es~ ~A. h~chter and B. Fraas~ Rec:ant Advanc~ In ~a~ioth~rapy ~rQatment Pl~nning"
On~oloy, May 1988, p. 43) :

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In order ~or the~ expe¢tations to be met, there ;s a need to develop a mean~ to accura~ely in~er~ace M~I w~th other diagnostia imag~ng ~odalities ~uch a~ CT or posi~ron emi~Qion tomography (PE~) and to krans~r tumor locali~akion d~a obtalned from M~ flnd the 5 other ima~ing modalities ~o radia~ion ~rea~ment d¢vices. I~ is important to realize thak due to ~patial and temporal magnet~c ield flUCtUA~ionS within the MRI ~ield, ~he displayed image ~ R di~torted to varying degrees $n a non-uniSorm manner. Th~e ~luctuat~ons a~s dependent on multlple factors 3uch a~ ambient temperature, and 10 extraneous m~netic ~elds in th~ ~mmedlate scanne~ vicinit~. Imaga~
appear~ng on the v~ewing ~areen (CRT), and ultima~ely ~n the fll~
hardcopy, are the result o~ system so~tware manipulat~on~ intended ~or viewer aesthet-ics. Further, the bony 6k~1ston which is o~t~n used a~
a refarence in determining tumor locat~on and size with other imaging ~S modalitie~ is n~t well visu~lized on M~I. Thu~, MRI does n~t pe~mit dl~ec~ tumor ~e~u~ement with ~h~ de~eo o~ con~ls~ency ~nd prec~lon d~manæe~ in a treatment planning etting.

20 8~MMARY OF ~ INV~TIO~
~ ~he p~e~ent i.nvention provides an inexpensive bUt ef~Rc~ive mean~ ~o interface MnI with other dia~nostic imagin~ ~od~lities and radiation`treatm~nt da~ces in a reprodu~ible manner. ~he inventlon here~n d~scribe~ ~nd claimQd avoid~ ~he inter~aclng pro~lem~ wi~h MRI
25 oth~rwiss caus~d ~y di~tortion and poor vi~ualiz~tion o~ ~one ~y emplo~$n~ a ~rid ~y~tem. Fo~ MRI, the ~ystem uses a gr~d ~tructure o~ me~bers o~ ~ontr~t mate~1~1 visualized on ~ nd a mean~ for r~produ~i~ly posit~onlng ~aid grid ~tructure relative to a body part bein~ imaged. With the grld properl~ po~itloned, the image ta~en with 3~ th~ ~I ~ill include both data ~lative tQ the body p~rt and a~t~fAct cau~ed ~y the contrast ~gent of ~he grid. AB thQ ~rue ~pa~
relaticnshlp o~ tha grid memb~r~ iB ~nown, and khe ~au~e~ ~
dlstortion affect the ~rid and ths body p~r~ ~im~l~rly, ~u~h grid arti~act ~unct$on~ x~erence in the ~am~ nn~r that th~ ~ony 35 -~k~ on ~erves as a re~erence with other im~ging mod~litie~. ~hu~, if a tumor ~ the struo~u~e o~ ln~re8~ being im~g~d, determinatlon~
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: 3 . o~ location and ~ize of the tumor ~re mada ~y re~erence to ~,he known spatial relation~hip of ~he grtd.
Wh~n the ~ubjec~ is ~udied u~ing oth~r im~ginq mo~litie~, the sy~tem is again employ~d changing enly the contrast material as S re~uired. Using the positioning mean~, ~he subject an~ the qrid structure are aligned in the same m~nner as when the MRI im~ges were . made. With th~ grid as a re~er~nce one can r~adily and accurately ~ompa~e MRI images with imaqes made with the other i.ma~ing modalitie~.
Thus, by sRlection of eontrast material, and a means to precisely and 10 consi~tently po~ition the grid and the patient in relation one to th~
other, the inven~ion functio~s to reproduoibly in~Qrface MRI wi~h other ~odalities such as CT, PET and radi~tion treatment devices.
Localiza~ion ~rids h~ve been d~scribed for use with CT, P~T and MRI
applicatio~s: ~S. Goer~s, et al: ~ ~omputeriz~d Tomo~raphi~
~5 st~reotactic Adap~ation SyRtem, 10 ~e~ro~urgery 375-37~ 82s P.~. ~aiek, et. al., Lo~alization Gr~d ~or MR guided Biopsy. 163(3) Radiology 825-826, 1~8?; S. Miura, et. al. Anatomical Adjus~ment~ in i Brain Positron Emission Tomography U~ing ~T Images. 12t2) ~ournal o~
Computer A~ ted Tomography 3~3-67, 1988; U.S. ~atent No. 4,5~3,538.) 20 ~o v~rying degrees, these grids are eikher diffiault ~o u~, expen~iYe to manu~acture, not aonduaive to BXaCt repositioning from ~can to scan or not rQadily in~erchangeable be~ween MRI a~d the va~iou~ other diaghostic modalitie~.
Ac~rdingly, it i~ an objeot o~ this inven~iDn to provide a m~hod and appa~atus whi~h may be used to interfaae MRI wi~h o~her imaging do~ices as well as with ~adio~her~py trea~ment unit~.
Anoth~r ob~ect o~ thi~ invention i~ to provid~ a method and apparatus to int~r~ace MRI with other ima~ng devices ~ well a~ wi~h . ~ur~ical intorvention techniquas.
Yet Ano~her obje~t o~ the invention i~ to ~a~ y ~he above ~tated ob~ctive~ in an unco~plicated and inexpen~ive ma~ner.
The novel features which ar~ belie~ed to be cha~cteris~ f `the invention both ~ to its or~anization and meth4~ o~ op~xation, ~oqe~'cher with furth~r objec~ive~ ~nd a~v~ntag~; thereo~, wil3. be 35 better under too~ ~rom the ~ollowing drawin0~ in which a pre~ently pre~erred embodiment o~ the ihv~ntion i~ illustra~ed ~y way o~

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~xample. It is tc~ he expxes~ly unders~ood, howev~r, that the drawing~
are gor the purpo~e c~ illu~tration and de~ription c~nly and ~e not intend~d as a deiinition o~ ~h~ limlt6 o~ ~h~ inven~cion.

S BR19 :F DJ3~ IPTION 43~ ~IE l>~WING
El~l~ Per~p~c:tlve view~3 o~ a vari~3ty of grid strut::t~res, F~aur~ lA: P~r~pec~tlvf3 v~ew o~ a grid struot:urs havlng a portion o~ it~ 3ide wall c:u~ away l:o expos~ tubing ~mbeddad in said Lo wall.
Fi<:lur~ ~: Partial p~r~p~at~v2 V~QW o2~ a grid RtrUcture h~in~ removable wall~.
Fiqure ~: P~r~pec:~ive v4 ew o~ ~h~ corn~r portion6 o~ a grid stru~tur~ i~lu~trating khe 1 nterconne~ted 'cubing network ~mbedd~d 15 within said wall, and ~p~cl~i~ally ~lowing the h~glnning and ~erm~nu~
por~ions whi¢h ~pen ~ th~ ~ame ~dge and are able ~o l~e cApped.
Eig~2~: Pa~tial per3pective view D~ the corner ~e ::tion o~ the grid 8~CrUCtUrQ Oe ~lgt~re lr~, 41~ u~tratlnq the u~e o~ a ~Grow plug a~ ~uch corn~r section.
~: P~r~p~c; tlva view ~howlng the r~l~tivn Or th~
patient pla~îo~T to th~3 pat~ent bed o~ an im~lng unit.
~ w~ e~nbodlm~nt~ o~ ~ patient plat~orm wi~h grid ~ructure ~lidably attach~d.
Fi~ur~s 7~ an~ 7B: Perspec~ive view illu~trating the use 25 of saggltal and ~ransv~r~e la6~ers to align the pat~en~ plat~orm and ~ub~ nc~ .
Fiç~ ~A a~d ~: P~rsp~ctive view o~ ~he sulojec~c on th~
pati~nt plat~orm with grid structure ~l$dably attached being mov~d into the g~n~ry o~ an imaqinq unit~ .
E~: Perf3p~at~v~ view and diA~rE.m~nat~c ~epresen-tation of the ~2~a of a comput~r algorithm to correck ~maç~e dis~cortion.

P~:~AI~ED DEl~oRlprIoN 0~ ~H~ EF~RP~E~ E~iBODIME27~
While ~hls invent$on is su~oeptibl~ o~ embo~iment ln many dif~er~n~ ~orm~, it ~ shown in th~ drawing~ ~nd wll~ here~n ~e .

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described, in detail, pre~E~rred embodlment~ o~ the inv~ntion. :rt should be understood, how~ver, ~hat the pre~3~nt dlsc: losure is ~o b~
. cons~dQred an ~xempli~ica~on o~ the prlnc~pl~e~ o~ the inven'cion and ifi no~ in~endBd ~o 1 imi~ the inven~ion to the ~pec~ f ~p embodlm~nts 5 illustrated.
The grld system o~ the pre~erred ambodimsnt has ~wo bas~c cQmponents~ Figur~ lA illu~trat~ the ~irst componQnt o~ the sy3tem, t~e grid s~ructurQ 11. ~s lllu~ra~ed, th~ grid ~tructure o~ the pra~erred embodiment ~5 a re~tan~ular ~rua~ur~ hav~ng two open end~
o 12. Th~ walls 13 of th~ grid ~truc~ur~ 11 are m~de o~ semi-rlgid non magnetic material ~uch ~ plexiglass. Embedded within th~ walls are ~u~es 16, ~lso of a non ~agn~t~a materi~l, containing con~ras~
~a~erial. ~or u~a with MRI, the p~efe~r2~ aontrast material ls Gadolinium-diethylon~trlam~nepentaacetia aaid tDPTA). Optimal lS visualizat~on on ~oth ~- and ~2-we~g~tad 6p~n-e~ho pulse sequana~s ha~ been obta~n~d ~y Ha~ek, ~t. al., ~upra, u~ing 5-mm-di~me~sr tubes f~ d with soo mM Gd-DP~A. It i~ to be un~r~ood that other paramagn~tia mat~rial may be substitu~d ~or Gd~DP~A and still co~e within th~ ~aop~ o~ the C~Aim~. For u~ wlth C~ ~aa~op~u~ aontra~t 20 materlal such a~ Bariu~ i~ d~sira~la.
~ h~ tub~s con~a~n~ng.cont~ast ma~erlal ar~ re~ularly spa~ed and arran~d ln a mutually orthegonal ~ashion. Al~o, one o~ the ~ube~
embedded ~n each ~ace o~ the ~rid structure i~ arran0ed so as to ~orm a dia~onal ~8.
~s In tha presG~ntly prere~red emhodiment, inter2~cinS~ b~tw~en dia~nostic modaliti~s i~ acaompli6hed by u~ing ~dentioally ~on~truc~ad gr~d structures hav1n~ ~UbQ~ contalnin~ ~on~ra~t ma~erl~l ~peoi~c ~or ~he parti~ular ima~ing mcd~llty belng u~ed. Thus, for example, one grid ~tructure having ~ubes cPntaining Gd-~PTA is u~ed wlth MRI and 30 an idantical ~tructure hav~ng ~u~ containing Bar~um i~ used wlth c~
and radiation treatment d~vice~.
Alternatively~ in~er~acin~ may bè acoompli~hed using a grid ~truoture, a~ ~llu~tra~ed in Figure 2, wherein the walls 2~ v~ ~aid struc~ure may b~ remov~ and re~lace~ wi~h ld~n~ically c~nstructed 35 WallB with tub~s Gon~a~ning a dlr~erent contra~ material. Thus, on~
would have a set o~ ~rid Btructu~e wall~ oont~ining con'cra~t materl~l ~ 3 ~ S~L
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: ~pecific ~or MRI, a set o~ walls containiny ~ontrast m~terial speci-:j ~ic ~or PE~, and yet another sek of walls ~pe~fic ~or CT an~
: r~diation t~eatment devices. Said grid structure walls would b~ held in pla~e by ~o~entional framing means manu~actured o~ non-magne~ic ! 5 material 23. An example of suita~le materi~l would be s~m~-r~qid nylon or plastic. Alternatively, the walls themselve~ cou~d have interlocking means at their e~qea ~uch as a mi.tered jaint type of asse~ly so as not ~o require an external ~ramQ to hold ~he wall~ in pla~e.
lo ~nke~acing be~ween M~I, CT ~nd rad~otherapy tre~tment devices is also made po~sible u~ing a grid struckure w~th ~ubes containing both paramagnetic and radiopaque contra~t material. An example would be a grid structure with tube~ containin~ a solution ~ith ~u~fici~nt amounts o~ both Gd-DPTA and Barium sul~ate, An alternative to using ~ep~rate grid struetures or removable grid structure walls ia a m~an~ to empty ~nd refill the tubing of the wall o~ contrast material. Figure 3 illustrates such an embodiment. In this embodiment, the ~ube~ o~ a wAll ~orm àn interconnQct~d n~wor~, the beginning and terminal portions (25, ~) 20 o~ which ~it ~lu~h w~th the ed~e of the wa~l. These and po~tion~ op~n t~ the outside a~e fi~ted with ~ ~appin~ means su~h as a simpl~ plug or sc~aw cap 2~. Thu~, to empty the tu~ing network o~ con~rast material on~ removes the cap ~rom t~e be~inning and terminus end o~
the tubin~ and tips the wall to le~ the mat~rial drain. To re~ill, 25 one tips the wall ~p and fill~ a~ the ~eginning un~il th~ solution runs out the terminal end~ On~e re~illed, ~he ends ar~ r~capped.
~ he ability to empky an~ re~`ill ~he ~ube~ of the ~rid ~tructure i~ pa~ticularly use~ul when using t~e g~id st~uoture to ~nte~a~e wlth P~T. Ima~iny wlth P~T is dependent on ~he ~mi~s~on R~
30 posttron~ The ma~erial~ whi~h are ~enerally u~ed a~ po~ltrRn emi~te~s have only a short hal~ life and A~e ~hu~ prepared ~hortly be~ore u~e.
~ iqure lD illustra~es ye~ another ~mbo~iment of the ~rid structure ~f the invention~ In thi~ embodi~ent the grid s~uctu~e 11 35 iQ an assembly of hollow ~u~e~ 31 joined in a gener~lly rectanyul~r ~hapo with addltional hollow tubes ~ diagonal~ ~2 ~ross ~our o~ th~

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fac~ o~ said rec:tan~l e. The hollo~ tube~ o~ this embodiment are formed of a non~magn~tic mat~rial Buch as a r~id pl~ti~ an~ ~illed with a ~olution o~ con~ra3~ materi~l. A~ ln~iaa~ed abov~, the con~rast material would be ~ele~d with regard to ~he parti~ular 5 imaging moda~ity being u~d. Fur~he~, as ~llustra~ed in ~igure 3, ~he corners o~ the grid ~tr~c~ure o~ ths embodimen~ o.~ Figure lD contain a ~crewable plug 33 whi~h allow~ emptylng and r~illing the hollow - tubes (31, 3~) such that ~olu~ions con~aining other pre~erred types of contra~t matQrial ar~ readily subskitutQd as the need arises.
Figu~es lB and lC illustra~e other suit~le configurations o~ the qrid structu~e. A~ will be appreciated, the exact configuration o~ a grid ~ructure lfi nQt important to the e~sense o~
th~ invention. In ~he same manner, the invention may also be carried ou~ by using contrast ma~erial in s~lid rather ~han liquid form. ~or example, contra~t ma~erial ln a ~eflned pattern could ke embedded in a matrix o~ nonmagnetic material or emb~ded wi~hln s41id rods or baræ
- that are arran~ed so as ~o ~orm a grid.
Although the ~xact con~iguration o~ the grid structure i~
unimportant, as illu~trated in Fi~ur~ ~ ~he ~rid structur~ 11 must be 20 og a ~ize su~fi~ient to ~it about the body ~ th~ sub~ec~ 2~ being imaged but within th~ ~ntry ~7 o~ the dia~nostlc ~m~ing ma~hine 28 b~ing used.
The ~ec~nd component of the grid SystQm i~ a means f~r reproducibly positionin~ th~ grid sy~tem xela~$ve to the body pa~t 25 bQing im~ged. ~n the preferr~d ~mbodiment, t~$s is accomplished by usin~ a grid lo~ating means and a cro~ed laser ~ystem. As lllu~trated in Figur~3 ~A and 6B, the grid ~ocating means of the pre~errQd Qmbodimen~ i~ a patient platPorm 41 ~o whi~h ths yrid 11 is ~lid~bly attached ~uch ~ha~ i~ may be mo~ed horizontally along the 30 lQngth of said platform and posi~ion~d at the app~opriAt~ place about ~h~ sub~ect be~ng l~aged. Located on the ~op ~ur~ace o~ the pla~orm and at either side of the gr~d i8 a ~cale in the ~o~m ~ regula~ly spaced and numbered de~ar¢ation~.
Slidabl~ attachmen~ mean~ ~ttac~ing the ~rid ~ruc~ure to 3s the plat~orm may be acccmplished by a ~ongue ~nd groove mechani~m, a roll~r and ~ac~ mechanism or o~h~r aon~n~ion~l mean~.

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: In the pre6ently preferred embodiment ~ig~ 6A, the platform ! con~i~tS of an upper member 43 and a lower member 44. The ~ppar member i~ ~u~ iently narrow ~o pas~ betwe~n th~ ~id~ walls of the ~rid struature, but sufficientl~ wlde so a~ not t4 allow lateral . 5 movement o~ the ~rid s~ruc~ure. As c~n be ~een in Figure 6A, at each ! end the members ar~ joined to a ~p~cer 4~ such th~t the upper memhe~
is separated f~om the lower member by a ~pace su~ ient ~o : ar~ommodAt~ the ~otto~ w~ll 4~ o~ the qrid stru~ture. The ~it o~ the : bottom w~ll in this ~pace ~hould be suoh that ~lidin~ o~ the grid : 10 b~C~ and for~h 1~ ac~ompli~hed without dif~ culty hut ik ~hould not : be 80 ~reat as ~o allow ver~ical mov~men~ of the gri~ s~ruc~ure. It : is de~ira~le to have ~u~icient horizontAl movement of the grld etructure such tha~ it can be mov~d the entire length o~ an average ~ized ~ubject centered on the p~at~orm~ Using the above described . 15 ~onst~uction, the horizon~al movement o~ ~he grid s~ructure ls ! dictated b~ the strength and rigidity o~ th~ upper member. I~ is : desirable that the upper me~ber support the sybject ~ithout ! defoxmat~on 80 that the gri~ ~tructure i~ not pinched and prev~ted : from horizontal movement. Thus, ~h~ ~ron~er and more rigid th~
20 upper ~embe~, the ~ea~er the ~pan between ~he ~upporting ~pas~r~ 4~, ~ and the greater ~he ho~xontal movement of the grid ~tructure. As : with the ~rid strUctUr~ 11, the plat~orm must ~ manufactu~ed of nonmagnetic material.
: Figure 5 illu~rat~s the rela~ionship of the platform 41 to : 25 the patient bed 30 of an imaging uni~ 2~. A~ illus~rated in ~igure 5, the p~ient pl~tform 41 approximat~ ~h~ dimen~ion~ ~ the patien~ bed ~ 30 in t~rms o~ leng~h an~ wid~h aha res~s on top o~ ~ai~ p~ient bed~

3 ThQ patien~ ~ed for ~h~ conven~ional M~Y unit as well a~ for the conven~ional ~ unit has a ~enerally oonvex ~rf~oe 36. ~he provision~
SO o~ a pati~n~ pla~orm a~ illu~ra~ed in Figure 5 tran~orms ~he ~n~ra}ly canvex ~ur~ac~ o~ the pa~i~nt b~d ~o a Eia~ ~urfa~e. Means may ~e provided to oonform the bottom sur~ace oP ~he pa~ient platform 41 to the concavity 3fi of the pa~ient ~e~ ~o as ~o pr~ven~ ~aid patient pla~orm from mo~ing abou~ wh~le it rests on ~h~ ~ur~a~ oP
3s the patient bed. Commer~ial patient plat~orm~ are avai~able ~rom su~h I manufa~urers as Pi¢k~ring and General Elec~ria M~ l Sy~tems. S~id ' ~` . ` ;,: , :; ` ~ ~: :

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:commercial pa~ien~ pla~or~.s ~an be ~dapted to re~eive the grid stru~ture a~ lllu~:~ra~ed in Fi~ure 5 and w~uld fall Wit~in the s~::ope o~ the claims oP thi~ invent~on.
:~igu~es 7~ and 7~ illu~tra e the çrossed laser syst~m :S which, toge~her with tile grid locating means, is u~ed to reproduoibly :position the su~ect ~n relatiqn to t~Q ~id. A~ illustratQd in :FigurQs 7A and 7B, the .~ag~al laser 51 ali5ns ~he platform and subjeot in the X and Z ~o~rdinates whereas the tr~nsverse l~ser 5~
aligns the subjec~ and plat~!rm in ~he Y and Z coordinates. Crossed 10 laser sy~tems are available cr.~.~ercially and can be readily adapted to the use descri~ed her~in. ~n example of a commercial~y available system is the ~ t Po~i.oninq ,Sy~m~ rom Gammex Inc., P.O. Box 2~708 Milwau~e, Wi~con~in 53226.

15 ~E~HOD OF U~2 -In ~ig. ~A, the pa~i~nt platform 41 wi~h grid struGture 11 :is mounted on the patient bed o~ th~ imagin~ unit 2~. ~he pa~ient plat~orm is then aligned v~a the c~ossed la~er sys~em utilizing :sagittal 51 and transv~rse 52 l~ers. ~he use of a oros~ed las~r 20 techniqu~ to align structurea in ~chree dimensional ~pace i~ known in the art. In relation to the pregen~ invention, the sagittal and ~ransvers~ lasers ~re ixed and define a point in X, Y and Z
coordina~es to which the patiant platform is rela~. The sagi~al laser de`~ines the X and 2 c:oordinate~; of the patient p~at~orm ~1 in 25 relation to the imaging unit table 30, while the transv~rse laser allows ~or a~justments ln the Y and Z coordinates. By recording the X~ Y and Z coordinates o~ ~he imaging unit ta~le with respe~t to ~ome init~al point o~ laser int~rsection on the table, ~he location of the pa~ient platPorm 41 i~ rRproduaible ~rom room ~o room, or ~rom imag~ng ~0 dovlce to imaging device.
Wi~h the ~ub~ect 2~ ~or ima~in~ stationed on the pa~ient plat~Qrm ~ ndard body immobiliæa~ion te~hniques such as body ~sting or pleximold# can be employed. As i~lustxated in ~i~. 7B, ~he sag~tal and transver~e laser~ are then used ~o po~ition ~he sub~ac~
35 with relat~on to the table and the desired X, Y and Z coordinate~.
Position~ng of the sub~e~t ~9 i~ aacomplished by employing marks o~

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ink tattoo:~ 94 on e~ther the ~Ub~ec~ or immobili~atiorl devi~es.
:~he ~rid structure 11 i5 then posi~ioned so a6 to ~lank the re~ion of intere~t of ~h~ ~;ubject 29 which i~ to be i~aged. In the S pre~erred e~nbodiment, the loaa~ion o~ the ~rid s~cructure, once po~itioned, i~ indicated by the number~d demarcations ~2 provided on :ea~h ~ide o~ the pla~orm. ~he3e numbered demarcations are ~ecorded, :and the table with the grid structure plat~orm an~ eubje~t is then :passed into th~ gantry 27 o~ the im~ging deviaP 28 and ~he r~gion o~
10 interest is scanned as illus~rate~ in Figure~ ~A and 8~.
~~hen the subjec~ is s~udied with imaging modalities ot~er !than MRI the appropriate contrast material i~ selected ahd ~he aho~e dQsGribed proc~dure is repeated. For exa~ple, if ~he subjeot is al~o to be s~udied using CT, a grid s~ruc~ure and pa~lent pl~t40rm 1S ldentical but for the contrast materlal con~Ained within the tube~ i~
m~unted on thR CT patient bed. In the case o~ ~T, baxium or other radiopaque ¢ontrast material is used. The pl~form is all~ned u~lng the orosB laBer s~tem ~s desçribed ab~ve; the sub~ect is ~t~oned on the plat~orms the subje~t is l~ser ali~ned and the grid stru~ture 20 ic then positioned over the region of intere~t using the num~red demara~tion ~sin~ the above mRthod, the re~ion ~f interest ~s stud~ed :wi~h MRI is de~ined in t~rm~ of the ~rid, As the grid pat~ern and the position of ~he subject rela~ive to the grid i~ identical ~n ~he CT
. 25 studies as with the MRI s~udie~ direct ~mp~rison hetween the studies f the two dif~erent modali~ies can ~e made in ~pite of the disto~tion o~ained wi~h NRI.
A8 sho~ld be app~eciate~, the ~ove-d&sc~ibed gri~ sy~em !and pro~edure can ~ u5ed to in~erfac~ MRI wi~h ~n~ other imagin~
: 30 modality in~luding PE~ and D.igit~l Subtractlon An~ raphy.
~ h~ ~rid s~tem and procedure also provides a means to mor~
accurately ~0114w the cour~e ~ A di~ease ~t~te and to ~udg~ th~
e$~e~tiveness g~ a t~eatment plan on th~t d~eaæ~ st~te. For example, :if one is trea~in~ a tumor with radio~herapy, i~ i~ desirable to : 35 periodi~ally repeat MRI and ~T ~can~ o~ the tu~or in order to moni~or the trea~ment. Because o~ the di~r~ion obtained wi~h M~I, it i~

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di*ficult to assess minute ~hanges in tumo:~ location and ~ize. Using the qrid sys~em and proc~dure de~;cribed above, ona avoid~; the lnheren'c distortion obtained with ~~ ecau6e the sy!3t~m and procedu~e permit : exa~t repositioning o~ th~ ~u~ect relative to th~ g~id structure S durin~ repeate~ scan and ~e~au~e the ~umor i~ defined in terms of'the : grid, small changes in tumor size or ~oca~ion can ~e monitored.
: ~or radioth~rapy purpos~s, using the metho~6 and.apparatus : of the present inven~ion, a ~umor de~ined ~y MRI ~includin~ coronal and sagittal se~ion~) may thu~ b~ more a~Gurat~ly t~an~lated to C5t 10 imaye~ (which are ~y neces~ity transverse), wi~h a resultant i~pro~ement in ~ar~et volume ~etermination. In the ca~e of computer , enhanced do~i~etry, CT imaging çannot b~ bypa~ed a~ it provides ; important eleatron den~lty ~nforma~ion, ~n ~h* o~e o~ ooplaner : radiation, a tumor may b~ de~ined in X, Y and Z a~ordinate~, and a ! 15 simpler conne~-the-dn~ me~hod 4~ target volume de~rmination is employed. The accUr~cy of thi~ can bq ~a~ily ~hea~ed at ~ th~rap~
! s$mu~ato~ or treatm~nt ~chine u~in~ an ~r~ay of laad w~ re~ instead o~ thQ ~adolinium chlor~d~ or barlum ~ulfate which a~e well visuali2ed via M~ and C~ respectively. ~h~ lnv~ntion i~ al~o adaptable to MRI-20 guided ne~dle ~iop~y, or PE~-gui~ed ~lopsy.

M~HOP ~F USTNG ~HE GRID SYS~EM TO CORRE~T MRI DISTORTIo~
Althou~h ~he in~entiun herein de~cr~ed can be used inspite of the distor~ion caused by maqnetic field fluctuatians in MRI, it may 25 also be u~ed as a mean~ to ~orreot such distor~ion. A~ before mentioned, th~ ~agn~tia ~ield ~luctuations di~tort ~h~ image of the ~ grid art~aat ~n the same manner as ~uah magnetic ~ield ~luc~uations : ~stort the ima~e of the sub~ec~. The gr~d arti~act6 whi~h can be diroatly relat~d to the known spatia~ rela~ion~hip of the ~rid ~hu~
! 30 a~t as indices of th~ de~re~ of aistor~ion p~ent in a par~icul~r image. B~ manipulatin~ the ~mage ~o a~ to bring the ~rid art~fact~
into proper relatlon to one another, the ~mage di~tortion of ~he subject would be simul~aneously corrected. Suoh ~anipulation ~an ~e done using ~onven~ional mathema~ical ~omput~tion~ which ar~ known in 35 the art.

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Sl As illu~tra~ed in Fi~ure Bs, the ~ove described method can be accomplished by usin~ a ~omputer ~lgorithm which ~pplies ~che r~quired ma~hematical prooedure~ to remove image distortion. In ~his manner, the aomputer algori~hm means can })e incorporated with ~he ~of~ware of 5 ~he ME~I 'co recogni~ the misalignment o~ grid artifact: 54, manipula~e the unoorrected imag~ to hring the qri~ arti~act lnto prc~per alignment and thus produc:e a c::orrected ima~e.

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Claims

What I claim is:

1. A grid structure for use in making an image of a body part with MRI and other imaging means, comprising:
regularly spaced members containing contrast material;
means for fixedly holding said regularly spaced members.

2. A grid structure as claimed in claim 1, wherein said members comprise hollow tubes.

3. A grid structure as claimed in claim 2, further comprising a means for emptying and refilling said hollow tubes of contrast material.

4. A grid structure as claimed in claim 1, wherein said grid structure is rectangular in shape and sufficiently large to fit about said body part being imaged but sufficiently small so as to fit within the gantry of said MRI or said other imaging means.

5. A grid structure as claimed in claim 1, wherein said contrast material comprises a combination of Gd-DPTA or similar paramagnetic material and barium or similar radiodense material.

6. A grid structure as claimed in claim 5, wherein said paramagnetic material and said radiodense material is in sufficient amount to cause visualization of said contrast material with X-ray, computed tomography and magnetic resonance imaging systems.

7. A grid system for use in making an image of a body part with MRI and other imaging means, comprising:
a means for forming a grid of contrast material;
a means for reproducing positioning said grid means relative to said body part such that artifact relative to said contrast material is produced on said image of said body part by said MRI and said other imaging means.

8. A grid system as claimed in claim 7, wherein said grid means comprises a grid structure of regularly spaced members containing contrast material and means for fixedly holding said regularly spaced members.

9. A grid system as claimed in claim 8, wherein said members are hollow tubes.

10. A grid system as claimed in claim 9, further comprising a means for emptying and filling said hollow tubes of contrast material.

11. A grid system as claimed in claim 10, wherein said grid structure is rectangular in shape and sufficiently large to fit about said body part being imaged but sufficiently small so as to fit within the gantry of said MRI or said other imaging means.

12. A grid system as claimed in claim 7, wherein said contrast material comprises a combination of Gd-DPTA or similar paramagnetic material and barium or similar radiodense material.

13. A grid system as claimed in claim 12, wherein said paramagnetic material and said radiodense material is in sufficient amount to cause visualization of said contrast material with X-ray, computed to tomography and magnetic resonance imaging systems.

14. A grid system as claimed in claim 7, wherein said positioning means comprises:
a crossed laser means for reproducing positioning said body part;
means for locating said grid means about said body part.

15. A grid system as claimed in claim 14, wherein said locating means comprises:
a patient platform;
means for slidably attaching said grid means to said patient platform such that when slidably attached to said patient platform said grid means can be moved horizontally along the length of said patient platform;
means for determining the position of said grid means along the length of said patient platform.

16. A grid system for correcting distortion which occurs when an image of a body part is produced with a magnetic resonance imaging means, comprising:
a means for forming of contrast material a grid of predetermined shape;
a means for reproducibly positioning said grid relative to said body part such that artifact relative to said contrast material is produced on said image of said body part by said imaging means.
a means for conforming said artifact essentially to said predetermined shape of said grid thereby conforming said image of said body part to the shape of said body part.

17. A method for correcting distortion which occurs when an image of a body part is produced with a magnetic resonance imaging means, comprising:
forming a grid structure of predetermined shape from contrast material;
reproducibly positioning said grid structure relative to said body part and said imaging means such that artifact relative to said contrast material is produced on said image of said body part by said imaging means.
conforming said artifact to essentially said predetermined shape of said grid structure thereby conforming said image of said body part to the shape of said body part.

18. A method as claimed in claim 17, wherein said conforming means comprises a computer algorithm.

19. A method for interfacing the image of a body part made with MRI with the image of said body part made with other imaging means, comprising:

forming a grid of contrast material;
reproducibly positioning said grid relative to said body part such that artifact relative to said grid is produced on said image of said body part made with MRI;
positioning said grid in said reproducible position relative to said body part such that artifact relative to said grid is produced on said image of said body part made with said other imaging means.

20. A method as clalimed in claim 19, wherein said grid comprises a grid structure of regularly spaced members containing contrast material and means for fixedly holding said regularly spaced members.

21. A method as claimed in claim 20, wherein said member are hollow tubes.

22. A method as claimed in claim 21, further comprising a means for emptying and filling said hollow tubes of contrast material.

23. A method as claimed in claim 22, wherein said grid structure is rectangular in shape and sufficiently large to fit about said body part being imaged but sufficiently small so as to fit within the gantry of said MRI or said other imaging means.

24. A method as claimed in claim 23, wherein said contrast material comprises a combination of Gd-DPTA or similar paramagnetic material and barium or similar radiodense material.

25. A method as claimed in claim 24, wherein said paramagnetic material and said radiodense material is in sufficient amount to cause visualization of said contrast material with X-ray, computed tomography and magnetic resonance imaging systems.

26. A method as claimed in claim 25, wherein said positioning means comprises:

a crossed laser means for reproducibly positioning said body part;
means for locating said grid structure about said body part.

27. A method as claimed in claim 26, wherein said locating means comprises:
a patient platform;
means for slidably attaching said grid structure to said patient platform such that when slidably attached to said patient platform said grid structure can be moved horizontally along the length of said patient platform;
means for determining the position of said grid structure along the length of said patient platform.