I-MRI ubuchwepheshe bokuthwebula obungahlanyisi obukhiqiza izithombe ezintathu ezinemininingwane ye-anatomical.Ngokuvamile isetshenziselwa ukuhlonza izifo, ukuxilongwa, nokuqapha ukwelashwa.Isekelwe kubuchwepheshe obuyinkimbinkimbi obujabulisa futhi obubona ushintsho ekuqondeni kwe-axis ejikelezayo yama-proton atholakala emanzini akha izicubu eziphilayo.
Isebenza kanjani i-MRI?
Ama-MRIs asebenzisa omazibuthe abanamandla akhiqiza insimu enamandla kazibuthe ephoqa ama-protons emzimbeni ukuthi ahambisane naleyo nkambu.Lapho i-radiofrequency current ishaywa esigulini, ama-proton ayavuselelwa, futhi ajikeleze ngaphandle kokulingana, abhekane nokudonsa kwamandla kazibuthe.Uma inkambu ye-radiofrequency icishiwe, izinzwa ze-MRI ziyakwazi ukubona amandla akhululwa njengoba ama-proton ehlangana kabusha nenkundla kazibuthe.Isikhathi esisithathayo ukuze ama-proton ahambelane kabusha nenkundla kazibuthe, kanye nenani lamandla akhululwayo, liyashintsha kuye ngendawo ezungezile kanye nemvelo yamakhemikhali yama-molecule.Odokotela bayakwazi ukuhlukanisa phakathi kwezinhlobo ezihlukahlukene zezicubu ezisekelwe kulezi zakhiwo kazibuthe.
Ukuze uthole isithombe se-MRI, isiguli sifakwa phakathi kukazibuthe omkhulu futhi kufanele sihlale singanyakazi phakathi nenqubo yokuthwebula izithombe ukuze singafiphali isithombe.Ama-ejenti wokuqhathanisa (ngokuvamile aqukethe isici i-Gadolinium) angase anikezwe isiguli ngomthambo ngaphambi noma phakathi ne-MRI ukuze kukhuliswe isivinini lapho ama-proton aphinde ahlangana khona nenkundla kazibuthe.Lapho ama-proton eshintshashintsha ngokushesha, isithombe siyakhanya.
Yiziphi izinhlobo zozibuthe ezisetshenziswa ama-MRIs?
Izinhlelo ze-MRI zisebenzisa izinhlobo ezintathu eziyisisekelo zozibuthe:
-Ozibuthe abangavimbeli benziwa ngamakhoyili amaningi ocingo asongelwe kusilinda lapho kudlula khona amandla kagesi.Lokhu kukhiqiza insimu kazibuthe.Lapho ugesi ucisha, amandla kazibuthe ayafa.Lawa mazibuthe anezindleko eziphansi ukuzenza kunozibuthe we-superconducting (bheka ngezansi), kodwa adinga amanani amakhulu kagesi ukuze asebenze ngenxa yokumelana okungokwemvelo kocingo.Ugesi ungabiza uma kudingeka ozibuthe bamandla aphezulu.
-Uzibuthe unomphela yilokho nje -- unomphela.Insimu kazibuthe ihlale ikhona futhi ihlale inamandla aphelele.Ngakho-ke, akubizi lutho ukunakekela insimu.I-drawback enkulu ukuthi lezi zidonsa zinzima kakhulu: ngezinye izikhathi eziningi, amathani amaningi.Amanye amasimu aqinile angadinga ozibuthe abanzima kangangokuthi kungaba nzima ukuwakha.
-Ozibuthe be-Superconducting yibo abasetshenziswa kakhulu kuma-MRIs.Ozibuthe abakhulu bayafana nozibuthe abangazi lutho - amakhoyili ocingo anamagesi adlulayo akha insimu kazibuthe.Umehluko obalulekile ukuthi kumagnethi we-superconducting ucingo luhlale lugezwa nge-helium ewuketshezi (emakhazeni angama-452.4 degrees ngaphansi kweziro).Lokhu kubanda okucishe kucabangeke kwehlisa ukumelana kwentambo kuqanda, kunciphisa kakhulu isidingo sikagesi ohlelweni futhi kwenze kube ukonga kakhulu ukusebenza.
Izinhlobo zikazibuthe
Idizayini ye-MRI inqunywa ngokuyisisekelo uhlobo nefomethi kazibuthe oyinhloko, okungukuthi i-MRI evaliwe, yohlobo lomhubhe noma i-MRI evulekile.
Ozibuthe abasetshenziswa kakhulu ama-superconducting electromagnets.Lokhu kuhlanganisa ikhoyili eyenziwe yaba yi-superconductive ngokupholisa uketshezi lwe-helium.Akhiqiza amandla kazibuthe aqinile, afanayo, kodwa ayabiza futhi adinga ukunakekelwa okujwayelekile (okungukuthi ukugcwalisa ithangi le-helium).
Uma kwenzeka ukulahlekelwa kwe-superconductivity, amandla kagesi achithwa njengokushisa.Lokhu kushisisa kubangela ukubilisa okusheshayo kwe-Helium ewuketshezi eguqulwa ibe umthamo ophezulu kakhulu wegesi ye-Helium (ukucisha).Ukuze uvimbele ukushisa okushisayo kanye ne-asphyxia, ama-superconducting magnets anezinhlelo zokuphepha: amapayipi okukhipha igesi, ukuqapha iphesenti le-oxygen kanye nezinga lokushisa ngaphakathi kwegumbi le-MRI, umnyango ovulekile ngaphandle (ukucindezela ngokweqile ngaphakathi kwekamelo).
Ozibuthe beSuperconducting basebenza ngokuqhubekayo.Ukuze unciphise imingcele yokufaka uzibuthe, ucingo lunesistimu yokuvikela engaba yi-passive (insimbi) noma esebenzayo (ikhoyili ye-superconducting yangaphandle lapho indawo yayo iphikisana naleyo yekhoyili yangaphakathi) ukuze kwehliswe amandla enkundla elahlekile.
I-MRI yensimu ephansi nayo isebenzisa:
-Ama-electromagnets aqinile, ashibhile futhi kulula ukuwagcina kunozibuthe abakhulu.Lezi zinamandla amancane kakhulu, zisebenzisa amandla amaningi futhi zidinga uhlelo lokupholisa.
-Ozibuthe baphakade, bamafomethi ahlukene, akhiwe izingxenye zensimbi ze-ferromagnetic.Nakuba zinenzuzo yokungabizi futhi kulula ukuzinakekela, zinzima kakhulu futhi zibuthakathaka ngokuqina.
Ukuze uthole inkambu kazibuthe ehluke kakhulu, uzibuthe kufanele ushunwe kahle (“icwebezele”), noma ngokunganyakazi, kusetshenziswa izingcezu zensimbi ezihambayo, noma ngokuqhubekayo, kusetshenziswa amakhoyili amancane kagesi asakazwe ngaphakathi kuzibuthe.
Izici zikazibuthe oyinhloko
Izici eziyinhloko zikazibuthe yilezi:
-Uhlobo (ama-electromagnets anamandla noma aphikisayo, odonsa unomphela)
-Amandla ensimu ekhiqizwayo, elinganiswa ku-Tesla (T).Emisebenzini yamanje yomtholampilo, lokhu kuyahlukahluka kusuka ku-0.2 kuya ku-3.0 T. Ocwaningweni, omazibuthe abanamandla we-7 T noma ngisho ne-11 T nangaphezulu bayasetshenziswa.
-Homogeneity
