MRI nubuhanga budasanzwe bwo kwerekana amashusho butanga amashusho atatu arambuye ya anatomique. Bikunze gukoreshwa mugutahura indwara, gusuzuma, no gukurikirana imiti. Ishingiye ku buhanga buhanitse bushimisha kandi bukamenya impinduka mu cyerekezo cyerekezo cyizunguruka cya proton kiboneka mumazi agize ingirabuzimafatizo.
Nigute MRI ikora?
MRIs ikoresha magnesi zikomeye zitanga imbaraga zikomeye za magneti zihatira proton mumubiri guhuza nuwo murima. Iyo umuyoboro wa radiofrequency uhita usunikwa binyuze kumurwayi, proton irashishikarizwa, kandi ikazunguruka ikaringaniza, ikarwanya gukurura umurima wa rukuruzi. Iyo umurima wa radiofrequency uzimye, sensor ya MRI irashobora kumenya ingufu zarekuwe nkuko proton ihuza numurima wa rukuruzi. Igihe bifata kugirango proton ihindurwe numurima wa magneti, kimwe nubunini bwingufu zasohotse, ihinduka bitewe nibidukikije hamwe nubumara bwa molekile. Abaganga bashoboye kuvuga itandukaniro riri hagati yubwoko butandukanye bwimitsi ishingiye kuri iyi magnetique.
Kugirango ubone ishusho ya MRI, umurwayi ashyirwa mumaseti manini kandi agomba kuguma cyane mugihe cyo gufata amashusho kugirango adahisha ishusho. Ibikoresho bivuguruzanya (akenshi birimo ibintu bya Gadolinium) birashobora guhabwa umurwayi winjiye mbere cyangwa mugihe cya MRI kugirango byongere umuvuduko proton igereranya numurima wa rukuruzi. Nibyihuta proton igaragara, niko ishusho irabagirana.
Ni ubuhe bwoko bwa magneti MRI ikoresha?
Sisitemu ya MRI ikoresha ubwoko butatu bwibanze bwa magnesi:
-Gukoresha imbaraga za magneti zikozwe mumashanyarazi menshi yizingiye kuri silinderi inyuramo amashanyarazi. Ibi bibyara imbaraga za rukuruzi. Iyo amashanyarazi azimye, umurima wa magneti urapfa. Izi magneti ziri munsi yikiguzi cyo gukora kuruta magneti arenze urugero (reba hano hepfo), ariko akenera amashanyarazi menshi kugirango akore kubera kurwanya insinga zisanzwe. Amashanyarazi arashobora kubahenze mugihe hakenewe magneti menshi.
-Urukuruzi ruhoraho nicyo gusa - gihoraho. Umwanya wa magneti uhora uhari kandi burigihe imbaraga zose. Kubwibyo, ntacyo bisaba kubungabunga umurima. Ingaruka nyamukuru ni uko izo magneti ziremereye cyane: rimwe na rimwe ni nyinshi, toni nyinshi. Imirima ikomeye yakenera magnesi ziremereye kuburyo bigoye kubaka.
-Gukoresha imbaraga za magneti nizo zikoreshwa cyane muri MRI. Imiyoboro ya superconducting isa nkaho isa na magnesi irwanya - ibitsike byinsinga hamwe numuyagankuba urengana birema umurima wa rukuruzi. Itandukaniro ryingenzi nuko mumashanyarazi arenze urugero insinga ikomeza koga muri helium y'amazi (kuri dogere 452.4 ikonje munsi ya zeru). Ubu bukonje hafi ya butagereranywa butuma insinga zirwanya zeru, bikagabanya cyane amashanyarazi asabwa muri sisitemu kandi bigatuma ubukungu bukora cyane.
Ubwoko bwa magnesi
Igishushanyo cya MRI kigenwa cyane nubwoko nuburyo bwa magneti nyamukuru, ni ukuvuga gufunga, ubwoko bwa MRI cyangwa gufungura MRI.
Imashini zikoreshwa cyane ni superconducting electromagnets. Ibi bigizwe na coil yakozwe muburyo budasanzwe no gukonjesha amazi ya helium. Zibyara imbaraga za magnetique zikomeye, ariko zihenze kandi zisaba kubungabungwa buri gihe (ni ukuvuga hejuru ya tank ya helium).
Mugihe habaye gutakaza imbaraga zidasanzwe, ingufu z'amashanyarazi zirakwirakwizwa nkubushyuhe. Ubu bushyuhe butera vuba vuba amazi ya Helium ahinduka mubunini cyane bwa gaze ya Helium (kuzimya). Mu rwego rwo gukumira inkongi y'umuriro na asphyxia, magnesi zidasanzwe zifite gahunda z'umutekano: imiyoboro yo kwimura gaze, kugenzura ijanisha rya ogisijeni n'ubushyuhe biri mu cyumba cya MRI, gukingura urugi hanze (gukabya imbere mu cyumba).
Imashini zidasanzwe zikora ubudahwema. Kugirango ugabanye imbogamizi zo kwishyiriraho magnet, igikoresho gifite sisitemu yo gukingira yaba pasiporo (metallic) cyangwa ikora (coil superconducting coil yo hanze umurima urwanya irya coil imbere) kugirango ugabanye imbaraga zumurima.
Umwanya muto MRI nayo ikoresha:
-Resistive electromagnets, zihendutse kandi byoroshye kubungabunga kuruta magnesi zidasanzwe. Ibi ntibifite imbaraga nkeya, koresha imbaraga nyinshi kandi bisaba sisitemu yo gukonjesha.
-Imashini zihoraho, zuburyo butandukanye, zigizwe nibikoresho bya ferromagnetic. Nubwo bafite ibyiza byo kuba bihendutse kandi byoroshye kubungabunga, biraremereye cyane nintege nke mubukomere.
Kugirango ubone imbaraga za magnetique nyinshi, rukuruzi igomba guhuzwa neza (“shimming”), haba muburyo bworoshye, ukoresheje ibice byimukanwa byimuka, cyangwa ukora cyane, ukoresheje amashanyarazi mato mato akwirakwizwa muri magneti.
Ibiranga rukuruzi nkuru
Ibintu nyamukuru biranga rukuruzi ni:
-Ubwoko (superconducting cyangwa irwanya amashanyarazi, magnesi zihoraho)
-Imbaraga z'umurima wakozwe, zapimwe muri Tesla (T). Mubikorwa byubuvuzi byubu, ibi biratandukanye kuva 0.2 kugeza 3.0 T. Mubushakashatsi, hakoreshejwe magnesi zifite imbaraga za 7 T cyangwa na 11 T zirenga.
-Uburinganire
