
kanthika anuranana imajinginte bhauthikashaasthram

magnetic resonance imajinginte (emm. aarr. aii) bhauthikashaasthram emm. aarr. aii saankethikavidyakaludeyum emm. aarr. aii upakaranangalude saankethika vashangaludeyum adisthaana bhauthika parigananakalekkurichaanu. shareerathinte shareeraghadanayum shareeraghadanayum anweshikkunnathinum tumours, veekkam, strock polulla neurological avasthakal, peshikaludeyum sandhikaludeyum vaikalyangal, hridayathileyum rakthakkuzhalukalileyum asaadhaaranathakal ennivayulppedeyulla rogangal kandethunnathinum radiology, nuclear medisin ennivayil kooduthalum upayogikkunna oru medical imaging saankethikathayaanu emm. aarr. aii. chithram mechappeduthunnathinum roganirnayam sugamamakkunnathinum kontraast ejantukal sirakalilo joyintilo kuthivaykkaam. sidi, ex-reey ennivayil ninnu vyathyasthamayi, emri ionizing radiation upayogikkunnilla, athinaal, kuttikalil roganirnayathinum aavarthichulla oottathinum anuyojyamaaya oru surakshithamaaya prakriyayaan ithu. nirddishta noonn-ferro magnetic mettal implaantukal, cochlear implaantukal, cardiac pays makerukal ennivayulla rogikalkku sakthamaaya kaanthikakshethrangalude phalangal undaayirunnittum innu emri undayirikkaam. ithu pazhaya upakaranagalil baadhakamalla, koodaathe medical professionalukalkulla vishadaamshangal upakaranathinte nirmmaathaav nalkunnu.
chila aattomik nucleusukalkku oru baahya kaanthikakshethrathil sthaapikkumbol radio freekwansi oorjjam agiranam cheyyaanum purappeduvikkaanum kazhiyum. klinikkal, research emaarkalil, hydrajan attangal palappozhum parishodhikkunna shareeraghadanaykku sameepam aantinakalkk labhikkuna oru kandethaavunna radio-freekwansi signal srishtikkaan upayogikkunnu. manushyarilum mattu jaiva jeevikalilum, prathyekichu vellathilum kozhuppilum hydrajan attangal swaabhaavikamaayi dhaaraalamaayi kaanapedunnu. ekkaaranathaal, mikka emm. aarr. aii. skaanukalum shareerathil vellathinteyum kozhuppinteyum sthaanam adisthaanaparamaayi mapp cheiyunnu. radio tharamgangalude pulsukal nuclear spin energy traansishane uthejippikkunnu, kaanthikakshethra gradiantukal bahiraakaashath signal praadeshikamaakkunnu. pulse seekvansinte paaraamettarukal maattunnathiloode, athile hydrajan aattangalude vishrama gunangale adisthaanamaakki tissukalkkidayil vyathyastha vairudhyangal srishtikkappedaam.
scaanarinte kaanthikakshethrathinulla ("bii" 0), protonukalude kanthika nimishangal feeldinte dishaykku samaantharamaayo samaantharamaayo vinyasikkunnu. oro protonin rund vinyasangalil onnu maathrame undaakoovenkilum, protonukalude shekharam avaykku eathenkilum vinyaasam undakaan kazhiyumennu thonnunnu. ithu kuranja oorjjaavasthayaathinaal mikka protonukalum "bii" 0 nuu samaantharamaayi vinyasikkunnu. oru radio freekwansi pulse prayogikkunnu, ithu samaantharamaayi aanti-paralal vinyaasathil ninnu protonukale uthejippikkaan kazhiyum, randaamathethu maathrame backie charchaykku prasakthamaakoo. avaye avayude santhulithaavasthayilekku thirike konduvarunna balatthinu marupadiyaayi, protonukal guruthwaakarshanathinte phalatthil oru karangunna chakram pole oru karangunna chalanathinu (munkoor) vidheyamaakunnu. spin-laattis relaxation prakriyayiloode protonukal kuranja oorjjaavasthayilekku madangum. ithu oru kaanthikapravaahamaayi kaanapedunnu, ithu signal nalkunnathinu reseiver koyilukalil maarunna volteju nalkunnu. oru voxalile oru prottoon allengil protonukalude koottam prathidhwanikkunna aavruthi protonino protonukalude koottatthino chuttumulla praadeshika kaanthikakshethrathinte sakthiye aasrayichirikkunnu, sakthamaaya oru feeld valia oorjja vyathyasathinum uyarnna aavruthi photonukalkkum anuyojyamaanu. sthalathinanusarichu rekheeyamaayi vyathyaasappedunna adhika kaanthikakshethrangal (gradiantukal) prayogikkunnathiloode, imej cheyyenda nirddishta sliceukal thiranjedukkaanum signalinte speshyal freekwansikalude ("k"-space) 2-d forrier parivartthanam edukkunnathiloode oru chithram nedaanum kazhiyum. gradient koyilukalil ozhukunna vaidyuthadhaarayil "bii" 0 ll ninnulla kanthika laurence balam kaaranam, gradient koyilukal uchathilulla muttal shabdangal srishtikkaan sramikkum, ithinaayi rogikalkku kelvi samrakshanam aavasyamaanu.
charithram.
nuclear magnetic resonansinekkurichulla gaveshanathe thudarnnu professor reymond andrew efrs efrs 1975 muthal 1977 vare nottingham sarvakalashaalayil emri scanner vikasippichu. 1978laanu phul body scanner nirmmichathu.
nuclear magnettism.
upa aattomik kanangalkk spinninte kwaandam mechanical property undu. 1h (protonukal), 2h, 3he, 23na allengil 31p polulla chila nucleusukalkku poojyamallaatha karakkamund, athinaal oru kanthika moment undu. 1h polulla spin-nucleus ennu vilikkappedunnavayude kaaryatthil, rund spin avasthakalundu, chilappol "upp", "daun" ennu vilikkunnu. 12sii polulla nucleusukalkku jodiyaakkaatha neutronukaloo protonukaloo illa, nettu spin illa; ennirunnaalum, isotope 13sii cheiyunnu.
eee spinukal sakthamaaya baahya kaanthikakshethrathil sthaapikkumbol avaa feeldinte dishayiloode oru achuthandinu chuttum sanjarikkunnu. protonukal rund oorjja aijanstettukalaayi (seeman prabhavam) vinyasikkunnu onnu kuranja oorjjavum oru uyarnna oorjjavum, avaa valare cheria vibhajana oorjjathaal verthirikkappedunnu.
anurananm, vishramam.
orotta protoninte swabhaavam krithyamaayi maathrkayaakkaan kwaandam mechanics aavasyamaanu. ennirunnaalum, protonukalude oru koottatthinte swabhaavam vendathra vivarikkan classical mechanics upayogikkaam. mattu spin formula _ 1 kanangaleppole, orotta protoninte spin alakkumbozhellaam athinu saadhaaranayaayi samaantharavum virudha samaantharavum ennu vilikkunna rund phalangalil onnu maathrame undaakoo. oru protoninteyo protonukaludeyo avasthayekkurichu charcha cheyyumbol, samaantharavum virudhavumaaya avasthakalude rekheeya samyojanamaaya aaa protoninte tharamgapravarthanatheyaanu nammal paraamarshikkunnath.
kaanthikakshethramaaya b0-nte saannidhyathil, kanikayude gyro-magnetic anupaathavum feeldinte shakthiyum nirnnayikkunna larmer freekwansiyil protonukal preproses cheiyunnathaayi kaanapedum. emariyil saadhaaranayaayi upayogikkunna staatik feeldukal oru radiophrequency (rf) photonumaayi poruthappedunna presession undaakkunnu.
kuranja oorjjaavasthayil protonukalude oru cheria adikamaanu thermodynamic santhulithaavasthayile nettu longityoodinal magnettaiseshan. ithu baahya feeldinu samaantharamaayi oru nettu polaraiseshan nalkunnu. oru rf pulse prayogikkunnathu eee nettu polaraiseshan vektarine vashathekku (i upayogichu) tipp cheyyaan kazhiyum.iii.90° pulse ennu vilikkappedunna), allengil athu vipareethamaakkuka (180° pulse ennu vilikkappedunna). protonukal rf pulsinoppam ghattathilekku varum, athinaal parasparam.
rekhamsha kaanthikavalkkaranathinte veendedukkaline rekhamsha allengil "tii" 1 relaxation ennu vilikkunnu, ithu samaya sthiraankamaaya "tii" 1-ll exponentialaayi sambhavikkunnu. transwers playinile ghatta poruttham nashtappedunnathine transwers allengil "tii" 2 relaxation ennu vilikkunnu. "t" 1 athinaal spin sisttathinte enthalpiyumaayi allengil samaantharavum samanthara virudhavumaaya spinninodulla nucleusinte ennavumaayi bandhappettirikkunnu. "maruvashathu, "t" 2 sisttathinte entropy allengil ghattatthile nucleusinte ennavumaayi bandhappettirikkunnu.
radio freekwansi pulse oof cheyyumbol, transwers vekttar ghadakam oru andolana kaanthikakshethram srishtikkunnu, ithu reseiver koyililekku oru cheria vaidyuthadhaaraye prerippikkunnu. eee signaline free induction deyy (phidu) ennu vilikkunnu. oru aadarshaparamaaya nuclear magnetic resonance pareekshanatthil, samaya sthiraankamaaya "t" 2 upayogichu phidu ekadesham exponentialaayi kshayikkunnu. ennirunnaalum, praayogika emariyil vividha speshyal lokkeshanukalil ("inhomogenitykal") staatik magnetic feeldil cheria vyathyaasangalund, ithu shareerathiludaneelam larmer freekwansi vyathyaasappedaan kaaranamaakunnu. ithu vinashakaramaaya edapedal srishtikkukayum ithu phidu kuraykkunnu. fidinte nireekshicha kshayam samaya sthiraankathe "tii" relaxation samayam ennu vilikkunnu, ithu ellaayppozhum "tii" 2 nekkaal cheruthaanu. athe samayam, rekhamsha kaanthikavalkkaranam "tii" 1 enna samaya sthiraankathode exponentialaayi veendedukkaan thudangunnu, ithu "tii" 2 nekkaal valare valuthaanu (chuvade kaanuka).
emariyil, staatik magnetic feeld oru feeld gradient koyil upayogichu vardhippichu scan cheytha mekhalayiludaneelam vyathyaasappedunnu, angane vyathyastha speshyal lokkeshanukal vyathyastha presession freekwansikalumaayi bandhappettirikkunnu. presession freekwansikal rf freekwansiyumaayi poruthappedunna feeld ulla pradeshangalil maathrame eksaitteshan anubhavappedukayulloo. saadhaaranayaayi, eee feeld gradiantukal scan cheyyenda mekhalayiludaneelam thudachuneekkaan modulate cheiyunnu, koodaathe eathaandu ananthamaaya vaividhyamaarnna rf, gradient pulse seekwansukalaanu emaaraikku athinte vaividhyatha nalkunnathu. feeld gradiantinte maattam freekwansi domainil prathikarikkunna phidu signal vyaapikkunnu, ennaal ithu veendedukkaanum alakkaanum kazhiyum (gradient ekko ennu vilikkappedunna oru refoxing gradient srishtikkaan), allengil radio freekwansi pulse ("spin-ikko" ennu vilikkappedunna oru srishtikkaan), allengil spread signalinte digital poost-prosessingil. chila "tii" 1-relaxation sambhavikkukayum spinukalude taapa santhulithaavastha erekkure punasthaapikkukayum cheyyumbol muzhuvan prakriya aavarthikkaam. ore slaisinte thudarchayaaya rund aaveshangalkkidayilulla samayamaan aavarthana samayam (tii. aarr).
saadhaaranayaayi, mriduvaaya tissue "tii" 1 ll oru second aanenkil "tii" 2 umm "tii" yum eathaanum pathinaayirakkanakkin millisecondukalaanu. ennirunnaalum, eee moolyangal vyathyastha tissuekalkkum athupole thanne vyathyastha baahya kaanthikakshethrangalkkum idayil vyaapakamaayi vyathyaasappedaam. eee perumaattam emaaraikku athinte athisayakaramaaya sophtt tissue kontraast nalkunna oru gadakamaanu.
gadolinium (iii) adangiyirikkunna emm. aarr. aii kontraast ejantukal vishrama paaraamettarukal, prathyekichu "tii" 1, maattunnathiloode (cheruthaakkikkond) pravartthikkunnu.
imaging.
imaging skeemukal.
feeld gradiantukalum radio freekwansi eksaitteshanum samyojippichu oru chithram srishtikkunnathinu niravadhi padhathikal aavishkarichittundu
eee skeemukal oronnum idaykkide specialist aaplikkeshanukalil upayogikkunnundengil, innu bhooribhaagam emr emejukalum slies selakshanodukoodiya dvimaana forrier transform (2dft) saankethikavidyayo trimana forrier transform (3dft) saankethikavidyayo upayogichaanu srishtikkunnathu. 2dft mattoru peru spin-warp ennaanu. slies selakshanodukoodiya 2dii. eph. tii saankethikavidyayude vivaranamaan ivide pinthudarunnathu.
slies selection illennum ghattam-encoding rund vyathyastha dishakalilaanu nadathunnathennum ozhike 3dii. eph. tii saankethikavidya valare samaanamaan.
ekko-planner imaging.
chilappol upayogikkunna mattoru skeem, prathyekichu braine scanningle allengil chithrangal valare vegathil aavashyamullidathu, ekko-planner imaging (api) ennu vilikkunnu eee saahacharyathil, oro rf eksaitteshanum vyathyastha speshyal encodinginoppam prathidhwanikkunna gradient ekkoyude oru train pinthudarunnu. multiplexed-epi ithilum vegathayeriyathaanu, udha.jii., muzhuvan mastishka pravartthana emri (ifmr) allengil defusion emri.
imej kontraastum kontraast mechappeduthalum.
saambilinullile vividha sthalangalil ninnu veendedutha enmr signalinte shakthiyile vyathyaasangalaan imej kontraast srishtikkunnathu. ithu uthejithamaaya nucleusinte (saadhaaranayaayi jala protonukal) aapekshika saandrata, pulse seekwansinu sesham aaa nucleusinte vishrama samayangalile ("t" 1, "t" 2, "t") vyathyaasangal, palappozhum prathyeka emr skaanukalkk keezhil charcha cheiyunna mattu paaraamettarukal ennivaye aasrayichirikkunnu. mikka emr chithrangalilum kontraast yadhaarthathil eee efakttukalude oru misrithamaanu, ennaal imaging pulse seekvansinte shradhaapoorvvam roopakalppana cheiyunnathu oru kontraast samvidaanathinu oonnal nalkaanum mattullava kuraykkaan anuvadikkunnu. vyathyastha kontraast mekkaanisangal thiranjedukkaanulla kazhivu emaaraikku athisayakaramaaya vazhakkam nalkunnu. thalachoril, "tii" 1-waiting velutha dravyathinte naadi bandhangal veluthathayi kaanapedaan kaaranamaakunnu, koodaathe chaaraniratthilulla dravyathinte neuronukalude sammelanangal chaaraniramayi kaanapedunnu, athesamayam cerebrospinal draavakam (sii. ezz. eph) irundathaayi kaanapedunnu. velutha dravyam, chaaraniratthilulla dravyam, cerebrospinal draavakam ennivayude vairudhyam "tii" 2 allengil "tii" imaging upayogichu vipareethamaakkunnu, athesamayam prottoon saandrata-bharamullah imaging aarogyakaramaya vishayangalil cheria vairudhyam nalkunnu. koodaathe, cerebral blud phloo (cbf), cerebral blud vooliyam (cbv) allengil blud ooksijaneshan thudangiya pravarthanaparamaaya paaraamettarukal "tii" 1, tii "2, tii" ennivaye badhikkum, athinaal anuyojyamaaya pulse sequenceukal upayogichu encode cheyyaan kazhiyum.
chila saahacharyangalil imaging paaraamettarukal maathram krameekarichukondu shareeraghadanayo thaalpparyamulla pathologio vendathra kaanikkan mathiyaya imej kontraast srishtikkaan kazhiyilla, eee saahacharyathil oru kontraast ejantu nalkaam. vayarinteyum cheria malavisarjjanathinteyum imajinginaayi ithu vellam pole lalithavum vaayiloode edukkaavunnathumaanu. ennirunnaalum, emariyil upayogikkunna mikka kontraast ejantukalum avayude prathyeka kanthika gunangalkkanusarichaanu thiranjedukkunnathu. ettavum saadhaaranayaayi, oru paramagnetic kontraast ejantu (saadhaaranayaayi oru gadolinium samyuktham) nalkunnu. gadolinium mechappeduthiya tissuekalum draavakangalum "tii" 1-waited chithrangalil valare thilakkamullathaayi kaanapedunnu. ithu vascular tissukal kandethunnathinu uyarnna samvedanakshamatha nalkunnu (udha.jii.tumours) koodaathe braine perfusion vilayiruthal anuvadikkunnu (udha.jii., strockil).
gadolinium adisthaanamaakkiyulla kontraast ejantukalude vishaamshathekkurichum vrukkayude pravartthanam thakararilaaya vyakthikalil avaa cheluthunna swaadheenathekkurichum aduthide aashankakal uyarnnittund. (thaazhe "sephtti"/kontraast ejantukal kaanuka.)
aduthide, superparamagnetic kontraast ejantukal, udha.jii.irumbu ooksaid naanoparttikkilukal labhyamaayi. eee ejantukal "tii"-waited chithrangalil valare irundathaayi kaanapedunnu, saadhaarana karal tissue ejantine nilanirthunnathinaal karal imajinginu ithu upayogikkaam, pakshe asaadhaaranamaaya pradeshangal (udha.jii.paadukal, tumours) illa. dahananaalathinte drishyavalkkaranam mechappeduthunnathinum dahananaalathile vellam mattu avayavangale maraykkunnathil ninnu thadayunnathinum (udha.jii., pancreas). dahananaalathil upayogikkaan saadhyathayulla beriyam sulfate polulla diamagnetic ejantukalum padichittundenkilum avaa pathivayi upayogikkunnilla.
"keey"-space.
1983-ll, eljangren tweag swathanthramaayi "keey"-space aupachaarikatha avatharippichu, ithu vyathyastha emr imaging saankethikavidyakale ekeekarikkunnathil vilamathikkaanaavaathathaane thelinju. oru leanier magnetic feeld gradient "jii" yude saannidhyathil swathanthramaayi pree-proses cheiyunna nuclear spinukalude oru koottam thammilulla prathipravartthanathiloode srishtikkappedunna demodulated emr signal "ezz" ("tii"), oru reseiver-koyilum phalapradamaaya spin saandrathayude forrier parivarthanatthinu thulyamaanennu avar kaanichu, formula _ 2. adisthaanaparamaayi, signal faaradeyude induction niyamathil ninnaan uruthirinjathu
evide
mattoru vidhathil paranjaal, samayam purogamikkumbol signal prayogicha kaanthikakshethra gradiantinte vektarinu aanupaathikamaaya sanjaarapathathinte vegatha vektarumaayi "keey"-spacil oru sanjaarapatham kandethunnu.
phalapradamaaya spin saandrata" enna padatthiloode nammal ardhamaakkunnathu "tii" 1 thayyaareduppu, "tii" 2 kshayam, feeld asamathvam, ozhukk, vyaapanam muthalaayava kaaranam defacing ennivayude falangalkkaayi sariyaakkiya yadhaartha spin saandrata soothravaakyam _ 2 ennaanu. koodaathe sweekarikkunna koyil vaidyuthakaanthika mandalavumaayi bandhappett rf probilo athinte ghattathilo signal prerippikkunnathin labhyamaya transwers magnettaiseshante alavine badhikkunna mattethenkilum prathibhaasangalum.
adisthaana "k"-space formula ninnu, sample cheytha daattayude vipareeta forrier parivartthanam eduthu nammal oru imej formula _ 6 punarnirmmikkunnath udan thanne pinthudarunnu, athaayath.
keey"-space aupachaarikatha upayogichu, sankeernamennu thonnunna niravadhi ashayangal lalithamaayi. udaaharanathinu, ghatta encodinginte (spin-warp reethi ennu vilikkappedunna) punk manasilaakkunnath (bhauthikashaasthranjarkku, prathyekichu) valare eluppamaanu. oru staanderd spin ekko allengil gradient ekko scanil, reedt (allengil view) gradient sthiramaayirikkumbol (iii.jii.," g ")," k "-space enna orotta varii oro rf eksaitteshanum scan cheiyunnu. ghatta encoding gradient poojyamaakumbol, scan cheytha line "k" x axis aanu. rf eksaitteshanum reedt gradiantinte thudakkathinum idayil poojyamallaatha oru ghatta-encoding pulse cherkkumbol, eee varii "k"-space, i ll mukalilekko thaazhekko neengunnu.iii.nammal "k" y = sthiraangam scan cheiyunnu.
keey"-space aupachaarikatha vyathyastha scanning saankethikavidyakal thaarathamyam cheiyunnathu valare eluppamaakkunnu. single-shoat epiyil, oru sinusoidal allengil sig-sag paatha pinthudarnnu "keey"-space muzhuvan orotta shottil scan cheiyunnu. keey"-space ennivayude marimari varikal ethir dishakalil scan cheiyunnathinaal, punarnirmmaanatthil ithu kanakkiledukkanam. multy-shoat epi, phaast spin ekko teknikkukal oro eksaitteshanum "keey"-spacinte oru bhagam maathrame nedunnulloo. oro shottilum, vyathyasthamaaya interleave segment nedukayum "keey"-space vendathra nannayi moodunnathuvare shottukal aavarthikkukayum cheiyunnu. k"-space madhyathilulla daatta "k"-space arikukalile dattayekkaal kuranja speshyal freekwansikale prathinidheekarikkunnathil, "k"-space madhyathilulla "t" e moolyam chithratthinte "t" 2 kontraast nirnnayikkunnu.
imej kontraast nirnnayikkunnathil "keey"-spacinte kendratthinte praadhaanyam kooduthal noothana imaging teknikkukalil prayojanappedutthaam. atharamoru saankethikavidya sarppila ettedukkalaanu-oru karangunna kaanthikakshethra gradient prayogikkunnu, ithu "keey"-speysile paatha kendratthil ninnu arikilekku sarppilamakaan kaaranamaakunnu. tii" 2, "tii" kshayam kaaranam ettedukkalinte thudakkathil signal ettavum valuthaanu, athinaal "keey"-space aadyam mechappedunnu.
parambaraagatha sig-sag ettedukkalukalumaayi thaarathamyappeduthumbol shabda anupaathathinu (cnr) vipareethamaayi, prathyekichu druthagathiyilulla chalanatthinte saannidhyathil.
formula _ 8 umm formula _ 9 umm konjugettu veriyabilukalayathinaal (forrier transfomumaayi bandhappett) "k"-spacile oru ghattam chithratthinte kazhcha feeld nirnnayikkunnuvennum (sariyaaya sample cheytha paramavadhi aavruthi) sample cheytha k-nte paramavadhi moolyam resolution nirnnayikkunnuvennum kaanikkan namukk naikvist sidhaantham upayogikkaam; i.iii.,
pulse seekvansinte udaaharanam.
samayarekhayil thirashcheena aksham samayathe prathinidheekarikkunnu. lamba aksham prathinidheekarikkunnath (mukalile varii) radio freekwansi pulsukalude amplitude; (madhya varikal) moonnu oorthoogoonal magnetic feeld gradient pulsukalude aamplityoodukal; (thaazhathe varii) reseiver analog-tuu-digital kanverttar (edisi). imej cheyyenda nucleidinte larmer freekwansiyilaanu radio freekwansikal prakshepanam cheiyunnathu. udaaharanathinu, 1 tiyude kaanthikakshethrathil 1 manikkoorin, <aii. dii. 1> emm. echu. echsinte aavruthi upayogikkum. moonnu feeld gradiantukalkku "jii" ex (saadhaaranayaayi oru rogiyude idathuninnu valathottu dishaykku anusrithavum rekhaachithrathil chuvapp niramullathum), "jii" vaii (saadhaaranayaayi rogiyude munvashathe dishayumaayi poruthappedukayum rekhaachithrathil pacha niratthilaakukayum cheiyunnu), "jii" isad (saadhaaranayaayi oru rogiyude thala muthal calviral dishayumaayi poruthappedukayum rekhaachithrathil neela niratthilaakukayum cheiyunnu) ennu label cheythittundu. negatteevu-goying gradient pulsukal kaanikkumbol, avaa gradient dishayude vipareethathe prathinidheekarikkunnu, i.iii., valathuninn edathottu, munnilekko calviralilekko. manushya scanninginaayi, 1-100 mt/m-nte gradient shakti upayogikkunnu uyarnna gradient shakti mikacha resolution vegathayeriya imajing anuvadikkunnu. ivide kaanichirikkunna pulse sequence oru transwers (axial) chithram srishtikkum.
pulse seekvansinte aadya bhagam, ss, "slies selection" kaivarikkunnu. aakruthiyilulla pulse (sink moduleshanodoppam ivide kaanichirikkunnu) oru slabinullilo slicenullilo 90° longityoodinal nuclear magnettaiseshan undaakkukayum transwers magnettaiseshan srishtikkukayum cheiyunnu. pulse seekvansinte randaam bhagam, peey, slies thiranjeduttha nuclear magnettaiseshanil oru ghatta maattam nalkunnu, ithu y dishayilulla athinte sthaanathinanusarichu vyathyaasappedunnu. pulse shreniyude moonnaam bhagam, mattoru slies selection (athe sliceinte) mattoru aakruthiyilulla pulse upayogichu slicenullil 180 digri transwers nuclear magnettaiseshan karakkunnu. eee transwers magnettaiseshan oru "t" e samayat oru spin ekko roopappeduthunnathinaayi refocus cheiyunnu. spin ekko samayat, oru freekwansi-encoding (phee) allengil reedt gradient prayogikkunnu, ithu nuclear magnettaiseshante resonant freekwansi x dishayilulla athinte sthaanathinanusarichu vyathyaasappedunnu. lambarekhakal prathinidheekarikkunnathu eee kaalayalavil signal "n" fe thavana ADC sample cheiyunnu. saadhaaranayaayi 128 muthal 512 vare saambilukalude "enn" phee edukkunnu.
rekhamsha kaanthikavalkkaranam kurachu veendedukkaan anuvadikkukayum oru samayam "t" r nuu sesham muzhuvan shreniyum "n" pe thavana aavarthikkukayum cheiyunnu, ennaal ghattam-encoding gradient vardhippichukondu (pacha gradient blokkile thirashcheena hatching soochippikkunnu). saadhaaranayaayi 128 muthal 512 vare aavarthanangalude "enn" peey cheiyunnu.
t" e (spin ekko maximum) samayat, ghattam y dishayilulla speshyal lokkeshan maathrame encode cheiyunnulloo ennu urappakkaan "g" x, "g" z ennivayile negatteevu-goying lobukal adichelppikkunnu.
saadhaaranayaayi "t" e ennathu 5 millimeterinum 100 millimeterinum idayilaanu, athesamayam "t" r ennathu 100 millimeterinum 2000 millimeterinum idayilaanu.
dvimaana matricks (128x128 num 512x512 num edayilulla saadhaarana alavu) nediya sesham, "keey"-space daatta ennu vilikkappedunnava uthppaadippicha sesham, parichithamaaya emr imej nalkunnathinu dvimaana vipareeta forrier parivartthanam nadathunnu. onnukil forrier parivartthanatthinte vyapthiyo ghattamo edukkaam, aadyathethu valare saadhaaranamaanu.
emm. aarr. aii scanner.
nirmmanavum pravartthanavum.
oru emm. aarr. aii scaanarinte pradhana gadakangal ivayaanu saambiline dhruveekarikkunna pradhana kantham, pradhana kaanthikakshethrathile asamathvangal sariyaakkunnathinulla shim koyilukal, emm. aarr. signal praadeshikavalkkarikkaan upayogikkunna gradient sisttam, saambiline uthejippikkukayum thathfalamaayundaakunna enn. emm. aarr signal kandethukayum cheiyunna aarr. eph sisttam. onno athiladhikamo computerukaliloodeyaanu muzhuvan samvidaanavum niyanthrikkappedunnath.
kantham.
scaanarinte ettavum valuthum chelaveriyathumaaya gadakamaanu kantham, backie scanner athinu chuttum nirmmichirikkunnu. kaanthatthinte shakti alakkunnathu teslassilaanu (tii). klinikkal kaanthangalkk saadhaaranayaayi 0.1-3.0 t shreniyil oru feeld shakti undu, manushya upayogathinu 9.4 tonn vareyum mruga samvidaanangalkku 21 tonn vareyum gaveshana samvidaanangal labhyamaan.
amerikkayil, 4 tonn vareyulla feeld shakti klinikkal upayogathinaayi fda amgeekarichittundu.
pradhana kaanthatthinte shakti pole thanne pradhaanamaan athinte krithyathayum. kaanthatthinte kendrathinullile kaanthikarekhakal (allengil saankethikamaayi ariyappedunnathupole, aiso-sentar) krithyathayodu aduthaayirikkanam. ithine homogenity ennu vilikkunnu. scan mekhalaykkullile ettakkurachilukal (feeld shakthiyile asamathvam) dashalakshathil moonnu bhaagangalil (3 ppm) kuravaayirikkanam. moonnu tharam kaanthangal upayogichittundu
mikka superconducting kaanthangalkkum avayude superconductive vayarinte koyilukal krayostaatt enna paathrathinullil draavaka heeliyathil mungikkidakkunnu. taapa insulation undaayirunnittum, chilappol draavaka naitrajan adangiya randaamathe krayostaatt ulppede, ambiyant choodu healium pathukke thilaykkaan kaaranamaakunnu. athinaal atharam kaanthangalkk draavaka healium upayogichu pathivayi topping upp aavasyamaanu. saadhaaranayaayi colled head ennum ariyappedunna oru cryocoolar, chila healium neeravi draavaka healium baathilekku veendum ghaneebhavippikkaan upayogikkunnu. niravadhi nirmmathaakkal ippol 'cryogenless' scannerukal vaagdaanam cheiyunnu, avide draavaka heeliyathil mungunnathinupakaram kanthika vayar oru cryocoolar vazhi nerittu thanuppikkunnu. pakaramaayi, draavaka healium thanthraparamaaya sthalangalil shradhaapoorvvam sthaapich kantham thanuppikkam, upayogicha draavaka heeliyathinte alavu naadakeeyamaayi kuraykkaam, allengil uyarnna thaapanila soopparkandaktarukal upayogikkaam.
kaanthangal vividha roopangalil labhyamaan. ennirunnaalum, sthiramaaya kaanthangal mikkappozhum 'sii' aakruthiyilullathum superconducting kaanthangal mikkappozhum silindar aakruthiyilullathumaanu. sii aakruthiyilulla superconducting kaanthangalum boxes aakruthiyilulla sthiramaaya kaanthangalum upayogichittundu.
chithratthinte gunanilavaaram nirnnayikkunnathil kaanthikakshethrathinte shakti oru pradhana gadakamaanu. uyarnna kaanthikakshethrangal signal-tuu-noys anupatham vardhippikkukayum uyarnna resolutiono vegathayeriya scanningo anuvadikkukayum cheiyunnu. ennirunnaalum, uyarnna feeld shakthikalkk uyarnna attakuttappanikalulla kooduthal chelaveria kaanthangal aavasyamaanu, koodaathe suraksha aashankakal vardhippikkukayum cheythu. 1.0-1.5 t enna feeld shakti pothuvaaya medical upayogathinulla chelavum prakadanavum thammilulla oru nalla othutheerppaanu. ennirunnaalum, chila prathyeka upayogangalkk (udha.jii.braine imaging) uyarnna feeld shakti abhikaamyamaanu, chila aashupathrikal ippol 3 tii scannerukal upayogikkunnu.
shims.
emr scanner aashupathriyilo klinikkiloo sthaapikkumbol, athinte pradhana kaanthikakshethram scanningin upayogikkaan paryaapthamalla. athukondaanu oru sample upayogichu feeldinte mikacha tuning cheiyunnathinu munbu, kaanthikatthinte kaanthikakshethram alakkukayum shim cheyyukayum cheyyendathu.
oru sample scanneril sthaapichathinushesham, pradhana kaanthikakshethram aaa saambilinullile samvedanakshamatha athirukalaal valachodikkappedunnu, ithu signal droptinum (signal kaanikkaatha pradeshangal) nediya chithrangalil speshyal valachodikkalinum kaaranamaakunnu. manushyareyo mrugangaleyo sambandhichidatholam sainasukal (vaayuvile paragnetic ooksijan kaaranam) polulla vaayu-tissue athirthikalil prabhavam prathyekichum prakadamaanu, udaaharanathinu, thalachorinte munbhaagathe lobukal chithreekarikkaan prayaasamaan. feeld homogenity punasthaapikkunnathinu oru koottam shim koyilukal scanneril ulppeduthiyittundu. golaakrithiyilulla haarmoniksinte niravadhi kramangalayi vitharanam cheyyappedunna feeld thiruthalukal ulppaadippikkaan kazhivulla iva saadhaaranayaayi ooshmaavil resisteevu koyilukalaanu.
sample scanneril sthaapicha sesham, shim koyilukalile vaidyuthadhaarakal krameekarichukondu "bii" 0 feeld 'shim' cheiyunnu. feeld gradiantukalude abhaavathil oru phidu signal parishodhichu feeld homogenity alakkunnu. moshamaayi shimming cheytha saambilil ninnulla phidu palappozhum niravadhi koombukalulla oru sankeernamaaya kshayam envalappu kanikkum. shim vaidyuthadhaarakal pinneedu krameekarikkukayum oru valia amplitude exponentialaayi shayikkunna phidu srishtikkukayum cheiyunnu, ithu oru ekeekritha "bii" 0 feeldine soochippikkunnu. eee prakriya saadhaaranayaayi automated aanu.
gradiantukal.
imaging voliyathiludaneelam kaanthikakshethram rekheeyamaayi maattikkond protonukalude sthaanangal speshyalaayi encode cheyyaan gradient koyilukal upayogikkunnu. larmer aavruthi pinneedu "x", "y", "z"-aaksukalile sthaanathinte pravartthanamaayi vyathyaasappedum.
gradient koyilukal saadhaaranayaayi avayude feeld shakthiyilum dishayilum vegathilum krithyamaayum krameekarikkaan anuvadikkunna noothana amplifierukalaal pravartthikkunna prathirodhikkunna vaidyuthakaanthangalaanu. saadhaarana gradient samvidaanangalkku 20 muthal 100 meter/meter (i.iii.oru 1.5 tonn kaanthatthil, oru paramavadhi "z"-axis gradient prayogikkumbol, feeld shakti 1 meter neelamulla borinte oru attathu 1.45 tonn, maruvashathu 1.55 tonn aakam). imajinginte thalam nirnnayikkunnath kanthika gradiantukalaanu-oorthoogoonal gradiantukal swathanthramaayi samyojippikkaan kazhiyunnathinaal, imajinginaayi eathu thalavum thiranjedukkaam.
scan vegatha gradient sisttathinte prakadanatthe aasrayichirikkunnu. sakthamaaya gradiantukal vegathayeriya imajingino uyarnna resolutiono anuvadikkunnu; athupole, vegathil switch cheyyaan kazhivulla gradient systengalkku vegathil scanning anuvadikkaanum kazhiyum. ennirunnaalum, naadi uthejanathekkurichulla suraksha aashankakalaal gradient prakadanam parimithamaanu.
gradient amplifierukaludeyum gradient koyilukaludeyum chila pradhana savisheshathakal slute rettum gradient shakthiyumaan. neratthe soochippichathupole, oru gradient koyil pradhana kaanthikakshethrathil ninnu kootticherkkukayo kuraykkukayo cheiyunna oru adhika, rekheeyamaayi vyathyaasappedunna kaanthikakshethram srishtikkum. eee adhika kaanthikakshethrathinu moonnu dishakalilum gadakangal undaakum, athaayath. "x," "y", "" "z" "; ennirunnaalum, kaanthikakshethrathiludalu ghadakam (saadhaaranayaayi" "z" "-axis ennu vilikkunnu, athinaal" "g" "z" "ennu soochippikkunnu) imajinginu upayogapradamaanu". eathenkilum achuthandil, gradient poojya sthaanathinte oru vashathulla kaanthikakshethrathilekku cherkkukayum maruvashathu athil ninnu kuraykkukayum cheyyum. adhika feeld oru gradient aayathinal, ithinu oru centimeteril gass allengil oru meettaril millittasla (mt/m) unitukal undu. emariyil upayogikkunna uyarnna prakadanamulla gradient koyilukalkku saadhaaranayaayi 1.5 tonn emaaraikku ekadesham 30 metrik tonn/meettaro athil kooduthalo ulla gradient kaanthikakshethram utppaadippikkaan kazhiyum. oru gradient sisttathinte slool rettu ennathu gradiantukal ethra vegathil oonaakkaano oof cheyyaano kazhiyum ennathinte alavaanu. saadhaarana uyarnna prakadana gradiantukalkku 100-200 t·m−1·s−1 vareyulla nirakkund. slave nirakk gradient koyilineyum (oru cheria koyilinekkaal oru valia koyiline mukalilekko thaazhekko uyarthaan kooduthal samayamedukkunnu) gradient amplifierinte prakadanatheyum (koyilinte inductance marikadakkaan dhaaraalam volteju edukkunnu) aasrayichirikkunnu, koodaathe chithratthinte gunanilavaarathil kaaryamaaya swaadheenam cheluthunnu.
radio freekwansi sisttam.
radio freekwansi (rf) transmission sisttathil oru rf synthesiser, power amplifier, traansmitting koyil enniva adangiyirikkunnu. aaa koyil saadhaaranayaayi scaanarinte bodiyilaanu nirmmichirikkunnathu. traansmittarinte shakti vyathyaasappettirikkunnu, ennaal uyarnna nilavaaramulla muzhuvan shareera scanarukalkkum 35 kilowatt vare ettavum uyarnna outtputtu power undayirikkaam, koodaathe 1 kilowatt sharashari power nilanirthaan kazhiyum. eee vaidyuthakaanthika mandalangal pathinaayirakkanakkin megaherts (palappozhum vaidyuthakaanthika spektrathinte short wave radio bhaagath) shreniyil amachwar radio upayogikkunna ettavum uyarnna shakthikale kaviyunna shakthikalilaanenkilum, emm. aarr. aii mesheen uthppaadippikkunna aarr. eph edapedal valare kuravaanu. emm. aarr. aii oru radio traansmittar allah ennathaanu ithinu kaaranam. traansmitting koyil" ll uthppaadippikkunna rf freekwansi vaidyuthakaanthikakshethram valare kurachu bandhapetta mattamulla vaidyutha mandala gadakangalulla (ellah parambaraagatha radio taranga prakshepanangalum pole) oru kanthika sameepa feeldaanu. athinaal, emm. aarr. aii traansmittar koyil uthppaadippikkunna uyarnna oorjjamulla vaidyuthakaanthikakshethram athinte aarr. eph freekwansiyil kooduthal vaidyuthakaanthika vikiranam uthppaadippikkunnil, koodaathe vaidyuthi koyil spacil parimithappedutthiyirikku, radio tharamgangalaayi vikiranam cheiyunnilla."athinaal, traansmitting koyil radio freekwansiyil oru nalla emm" "feeld" "traansmittaanu, ennaal radio freekwansiyil oru mosham emm" "radiation" "traansmittaanu".
reseaveril koyil, pree-amplifier, signal prosessing sisttam enniva adangiyirikkunnu. vishayathinullile nuclear relaxation vazhi uthppaadippikkunna rf vaidyuthakaanthika vikiranam yadhaartha emm radiationaanu (radio tharamgangal), iva vishayathe rf radiationaayi upekshikkunnu, pakshe avaa aduthulla radio tunerukalkku edukkaan kazhiyunna rf edapedalinu kaaranamaakaathathra kuranja sakthiyaanu (koodaathe, emri scannerukal saadhaaranayaayi loha mesh line cheytha murikalilaanu sthithicheyyunnathu, avaa farreday koodukalaayi pravartthikkunnu.)
rf transmission emr signal resoption vendi samyojitha koyil upayogichu scan cheyyaan kazhiyumenkilum, oru cheria pradesham imej cheiyukayaanenkil, mikacha chitra nilavaaram (i.iii.uyarnna signal-tuu-noys anupatham) aduthu gadippichirikkunna cheria koyil upayogichaanu labhikkunnath. thala, kalmut, kaithanda, nench allengil aantharikamaayi shareerathinte bhaagangalkk chuttum aduthu cherunna vividatharam koyilukal labhyamaan.jii., malaashayathil.
emm. aarr. aii. saankethikavidyayile sameepakaala vikasanam samaantharamaayi onniladhikam daatta chaanalukal nedaan kazhivulla athyaadhunika multy-elament ghattam ghattamaayulla array koyilukalude vikasanamaan. eee 'samanthara imaging' saankethikavidya accelered imaging anuvadikkunna savisheshamaaya acvisition skeemukal upayogikkunnu, kanthika gradiantukalil ninnu uthbhavikkunna chila speshyal codingukal vyathyastha koyil gadakangalude speshyal censitivity upayogichu maattisthaapikkunnu. ennirunnaalum, vardhicha thvaranam signal-tuu-noys anupatham kuraykkukayum imej punarnirmmaanatthil sheshikkunna karakaushala vasthukkal srishtikkukayum cheyyum. samaantharamaayi ettedukkunnathinum punarnirmmikkunnathinum pathivayi upayogikkunna rund padhathikale sense, grappa ennu vilikkunnu. samanthara imaging saankethikavidyakalude vishadamaaya avalokanam ivide kaanaam

