I-MRI Homogeneity

Ukufana kwendawo yemagneti (homogeneity), okwakwaziwa njengokufana kommandla wemagnethi, ibhekisa kulwazi lwendawo yemagnethi ngaphakathi komda womthamo othile, oko kukuthi, ingaba imigca yomhlaba wemagnethi kuwo wonke ummandla weyunithi iyafana. Umthamo othile apha udla ngokuba sisithuba esingqukuva. Iyunithi ye-magnetic field uniformity yi-ppm (inxalenye yesigidi ngasinye), oko kukuthi, umahluko phakathi kowona mandla aphezulu entsimi kunye nowona mandla asezantsi ommandla wemagnethi kwindawo ethile eyahlulwe ngomndilili wamandla entsimi aphindaphindwe ngesigidi esinye.

I-MRI idinga iqondo eliphezulu le-uniform yamagnetic field, emisela isisombululo sesithuba kunye nomlinganiselo wesignali-kwingxolo yomfanekiso kuluhlu lwemifanekiso. Ukungahambelani kakuhle kwemagnethi kuya kwenza umfanekiso ube mfiliba kwaye ugqwetheke. I-magnetic field uniformity imiselwe yi-design yemagnethi ngokwayo kunye nokusingqongileyo kwangaphandle. Ubukhulu bendawo yomfanekiso wemagnethi, kokukhona ukufana kwemagnethi kusezantsi kunokufezekiswa. Ukuzinza kwemagnethi sisalathiso sokulinganisa iqondo lokukhukuliseka kwemagnethi yamandla kunye nexesha. Ngexesha lokulandelelana kwemifanekiso, ukukhukuliseka kokuqina kwemagnethi kuya kuchaphazela isigaba somqondiso we-echo olinganisiweyo ophindaphindiweyo, okukhokelela ekugqwethekeni komfanekiso kunye nokuncipha komlinganiselo we-signal-to-noise. Ukuzinza kwemagnethi kuhambelana ngokusondeleyo nohlobo lwemagnethi kunye nomgangatho woyilo.

Amalungiselelo omgangatho wokufana wemagnethi anxulumene nobungakanani kunye nokumila kwesithuba somlinganiselo esithathiweyo, kwaye ngokuqhelekileyo kusetyenziswa isithuba esingqukuva ngedayamitha ethile kunye nombindi wemagnethi njengoluhlu lomlinganiselo. Ngokuqhelekileyo, ukumelwa kwe-magnetic field uniformity kwimeko yendawo ethile yokulinganisa, uluhlu lotshintsho lwemagnethi yamandla kwindawo enikiweyo (ixabiso le-ppm), oko kukuthi, isigidi esinye samandla ombane oyintloko (ppm) njengeyunithi yokutenxa ukuchaza ngokobungakanani, le yunithi yotenxa ibizwa ngokuba yi-ppm, ebizwa ngokuba luphawu olupheleleyo lwexabiso. Ngokomzekelo, ukufana kwendawo yamagnetic ngaphakathi kwe-cylinder ye-scan yokuvula i-aperture yi-5ppm; I-magnetic field uniformity kwisithuba se-sphere ye-40cm kunye ne-50cm concentric kunye neziko lemagnethi yi-1ppm kunye ne-2ppm, ngokulandelelanayo. Isenokuthi ibonakaliswe ngolu hlobo: ukufana komhlaba wemagnethi kwisithuba setyhubhu kwi-cubic centimeter nganye kwindawo yomzekelo ophantsi kovavanyo yi-0.01ppm. Ngaphandle komgangatho, phantsi kwesiseko sokuba ubungakanani besphere yomlinganiselo buyafana, ixabiso elincinci le-ppm libonisa ukuba ngcono ukufana kwemagnethi.

Kwimeko yesixhobo se-1.5-tMRI, i-drift fluctuation yamandla amagnetic field amelwe yiyunithi enye yokuphambuka (1ppm) yi-1.5 × 10-6T. Ngamanye amazwi, kwinkqubo ye-1.5T, ukufana kwemagnethi ye-1ppm kuthetha ukuba indawo enkulu yamagnetic ine-fluctuation ye-drift ye-1.5 × 10-6T (0.0015mT) ngokusekelwe kwimvelaphi ye-1.5T yamandla magnetic. Ngokucacileyo, kwisixhobo se-MRI esinamandla ahlukeneyo entsimi, ukuhluka kwamandla amagnetic field amelwe yiyunithi nganye yokuphambuka okanye i-ppm eyahlukileyo, ukusuka kulo mbono, iinkqubo zentsimi eziphantsi zinokuba neemfuneko eziphantsi zokufana kwamagnetic field (jonga iThebhile 3-1) . Ngolungiselelo olunjalo, abantu banokusebenzisa umgangatho wokufanisa ngokulula ukuthelekisa iinkqubo ezinamandla ahlukeneyo entsimi, okanye iinkqubo ezahlukeneyo ezinamandla omhlaba ofanayo, ukwenzela ukuvavanya ngokufanelekileyo ukusebenza kwemagnethi.

Ngaphambi komlinganiselo wokwenyani wokufana kwemagnethi, kuyimfuneko ukumisela ngokuchanekileyo iziko lemagnethi, kwaye emva koko ulungelelanise isixhobo sokulinganisa ubungakanani bentsimi (imitha yeGauss) probe kwisithuba sesithuba seradiyasi ethile, kwaye ulinganise ubunzulu bomhlaba wemagnethi. inqaku ngenqaku (indlela yendiza engama-24, indlela yenqwelomoya eyi-12), kwaye ekugqibeleni iqhube idatha ukubala ukufana kwemagnethi ngaphakathi komthamo wonke.

Ukufana kwemagnethi kuya kutshintsha kunye nokusingqongileyo. Nokuba umazibuthe ufikelele kumgangatho othile (ixabiso eliqinisekisiweyo kumzi-mveliso) ngaphambi kokuba ushiye umzi-mveliso, Noko ke, emva kofakelo, ngenxa yempembelelo yezinto ezisingqongileyo ezifana nemagnethi (self-) shielding, RF shielding (iingcango kunye neWindows), ipleyiti ye waveguide. (ityhubhu), isakhiwo sentsimbi phakathi kwamagnethi kunye nezixhaso, izinto zokuhombisa umhlobiso, izixhobo zokukhanyisa, imibhobho yokungenisa umoya, imibhobho yomlilo, iifeni zokukhupha ngokukhawuleza, izixhobo eziphathwayo (nokuba iimoto, izinyusi) ecaleni kwezakhiwo eziphezulu nangaphantsi, ukufana kwayo kuya kutshintsha. Ngoko ke, ukuba ukufana kuyahlangabezana neemfuno ze-imaging resonance magnetic kufuneka isekelwe kwiziphumo zangempela zokulinganisa ngexesha lokuvunywa kokugqibela. Umgangatho wentsimi ye-passive kunye nomgangatho osebenzayo we-coil ye-superconducting eyenziwe yinjineli yofakelo yomenzi we-magnetic resonance kwifektri okanye esibhedlele yimilinganiselo ephambili yokuphucula ukufana kwendawo yamagnetic.

Ukuze kufunyanwe indawo imiqondiso eqokelelweyo kwinkqubo yokuskena, isixhobo se-MRI sikwafuna ukongamela umhlaba othambekileyo wemagnethi △B ngotshintsho oluqhubekayo nolwandisiweyo olusekelwe kumhlaba ongundoqo wemagnethi B0. Kuyacingeleka ukuba umhlaba wokuthambeka △B obekwe phezulu kwivoxel enye kufuneka ube mkhulu kunomhlaba wemagnethi ukutenxa okanye ukuphambuko okubangelwa yimagnethi engundoqo B0, kungenjalo iya kutshintsha okanye itshabalalise isignali yokuma yendawo engentla, ibangele izinto zakudala kunye ukunciphisa umgangatho womfanekiso.

Okukhona ukutenxa okukhulu kunye nokuguquguquka okukhulu kommandla wemagnethi oveliswa ngowona mmandla mkhulu wemagnethi engu-B0, kokukhona ukufana kwemagnethi kumbi, kokukhona usezantsi umgangatho womfanekiso, kunye nokunxulumana ngokuthe ngqo kulandelelwano loxinzelelo lwelipid (umahluko weresonance frequency phakathi amanzi kunye namafutha emzimbeni womntu yi-200Hz kuphela) kunye nempumelelo yokuhlolwa kwe-magnetic resonance spectroscopy (MRS). Ngoko ke, ukufana kwemagnethi yenye yezona zibonakaliso eziphambili zokulinganisa ukusebenza kwezixhobo zeMRI.

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Isitofu semidiya esinoxinzelelo oluphezulus zikwabaluleke kakhulu izixhobo ezincedisayo kwinkalo yomfanekiso wezonyango kwaye ziqhele ukusetyenziswa ukunceda abasebenzi bezonyango ukuhambisa imidiya eyahlukileyo kwizigulana. I-LnkMed ngumvelisi obekwe e-Shenzhen ogxile ekwenzeni ezi zixhobo zonyango. Ukusukela ngo-2018, iqela lobuchwephesha benkampani beligxile kuphando kunye nokuveliswa kwee-ejenti zoxinzelelo oluphezulu. Inkokeli yeqela ngugqirha oneminyaka engaphezu kweshumi yamava e-R&D. Olu lwazi luhle lweCT isitofu esisodwa,CT isitofu sentloko kabini,Isitofu seMRIkwayeI-Angiography yoxinzelelo oluphezulu(Isitofu seDSA) eveliswe yi-LnkMed ikwaqinisekisa ubuchwephesha beqela lethu lobugcisa – uyilo olubambeneyo noluluncedo, imathiriyeli eyomeleleyo, ukusebenza ngokugqibeleleyo, njl. njl., ziye zathengiswa kwizibhedlele ezinkulu zasekhaya nakwiimarike zangaphandle.