MRI inyanzvi yekufungidzira isiri-invasive inogadzira matatu mativi akadzama mifananidzo yeanatomical. Inowanzoshandiswa pakuona zvirwere, kuongororwa, uye kutarisa kurapwa. Inobva pane tekinoroji yakaomesesa iyo inonakidza uye inoona shanduko munzira yekutenderera axis yemaproton anowanikwa mumvura inoumba mhenyu tishu.
MRI inoshanda sei?
MaMRIs anoshandisa magineti ane simba anoburitsa simba remagineti rakasimba rinomanikidza mapurotoni ari mumuviri kuti aenderane nemunda iwoyo. Kana radiofrequency current ichibva yadhonzwa nemumurwere, maproton anomutswa, obva abuda mukuenzana, achinetsekana nekudhonzwa kwemagnetic field. Kana iyo radiofrequency ndima yakadzimwa, maMRI sensors anokwanisa kuona simba rinoburitswa sezvo mapurotoni anoenderana nemagnetic field. Nguva inotora kuti mapurotoni agadzirise pamwe chete nemagnetic field, pamwe chete nehuwandu hwesimba rakabudiswa, hunoshanduka zvichienderana nenharaunda uye chimiro chemakemikari emamorekuru. Vanachiremba vanokwanisa kutaura mutsauko pakati pemhando dzakasiyana-siyana dzematishu zvichienderana neaya magineti.
Kuti uwane mufananidzo weMRI, murwere anoiswa mukati megineti hombe uye anofanira kuramba akanyarara panguva yekufungidzira kuitira kuti asasvibisa mufananidzo. Contrast agents (kazhinji iine element Gadolinium) inogona kupihwa kumurwere netsinga isati yasvika kana panguva yeMRI kuti iwedzere kumhanya uko mapurotoni anoenderana nemagnetic field. Iyo inokurumidza mapurotoni anochinja, chifananidzo chinowedzera kupenya.
Ndeapi marudzi emagineti anoshandiswa neMRIs?
MRI masisitimu anoshandisa matatu emhando mhando dzemagineti:
-Resistive magineti anogadzirwa kubva kune akawanda coils ewaya akaputirwa necylinder iyo magetsi anofambiswa. Izvi zvinogadzira magnetic field. Kana magetsi akavharwa, simba remagineti rinofa. Aya magineti ane mutengo wakaderera kugadzira pane superconducting magineti (ona pazasi), asi anoda huwandu hukuru hwemagetsi kuti ushande nekuda kwekupokana kwewaya. Magetsi anogona kudhura kana magineti emagetsi epamusoro achidiwa.
-A magineti asingagumi ndizvozvo -- zvachose. Iyo magnetic field inogara iripo uye inogara iine simba rakazara. Naizvozvo, hapana chinodiwa kuchengetedza munda. Dambudziko guru nderekuti magineti aya anorema zvakanyanya: dzimwe nguva akawanda, akawanda matani. Mimwe minda yakasimba yaizoda magineti anorema zvekuti anonetsa kuvaka.
-Superconducting magineti ndiyo inonyanya kushandiswa muMRIs. Superconducting magineti akati fanane nemagineti anodzivirira - makoiri ewaya ane magetsi anopfuura anogadzira iyo magineti. Musiyano wakakosha ndewekuti mune superconducting magineti waya inogara ichishambidzwa mumvura helium (painotonhora 452.4 madhigirii pazasi zero). Uku kutonhora kusingafungidzike kunodonhedza kuramba kwewaya kusvika zero, zvichidzikisa zvakanyanya kudiwa kwemagetsi kuhurongwa uye kuita kuti iwedzere hupfumi kushanda.
Mhando dzemagineti
Magadzirirwo eMRI anonyanya kutsanangurwa nemhando uye chimiro chegineti huru, kureva kuvharwa, tunnel-mhando yeMRI kana yakavhurika MRI.
Magineti anonyanya kushandiswa ndeye superconducting electromagnets. Izvi zvinosanganisira coil yakaitwa superconductive nehelium fluid kutonhora. Dzinoburitsa yakasimba, ine homogeneous magineti minda, asi inodhura uye inoda kugara ichichengetwa (kureva kukwirisa helium tank).
Muchiitiko chekurasikirwa kwe superconductivity, simba remagetsi rinopera sekupisa. Kupisa uku kunokonzeresa kukurumidza kufashaira kwemvura yeHelium iyo inoshandurwa kuita vhoriyamu yakakwirira kwazvo yeHelium ine gasi (kudzima). Kuti udzivise kupisa kwemafuta uye asphyxia, magineti e superconducting ane masisitimu ekuchengetedza: mapaipi ekubvisa gasi, kutarisa chikamu cheokisijeni uye tembiricha mukati mekamuri yeMRI, gonhi rinovhurika kunze (kudzvinyirira mukati mekamuri).
Superconducting magineti anoshanda nguva dzose. Kudzikamisa magineti ekumisikidza zvimhingamipinyi, mudziyo une shielding system ingangoita passive (simbi) kana inoshanda (yekunze superconducting coil ine munda unopikisana neiyo yemukati coil) kuderedza simba remunda rakarasika.
Low field MRI inoshandisawo:
-Resistive electromagnets, ayo akachipa uye ari nyore kuchengetedza pane superconducting magineti. Aya ane simba shoma, anoshandisa simba rakawanda uye anoda kutonhora system.
-Magineti echigarire, emafomati akasiyana, anoumbwa neferromagnetic metallic components. Kunyange zvazvo vane mukana wokuva asingadhuri uye ari nyore kuchengeta, iwo anorema zvikuru uye asina simba mukusimba.
Kuti uwane iyo yakanyanya homogeneous magineti, iyo magineti inofanirwa kukwenenzverwa ("shimming"), kungave kusingaite, uchishandisa zvimedu zvesimbi zvinofambiswa, kana zvine simba, uchishandisa madiki emagetsi coils akagoverwa mukati megineti.
Hunhu hwemagineti makuru
Mamiriro makuru emagneti ndeaya:
-Type (superconducting kana resistive electromagnets, magineti echigarire)
-Kusimba kwemunda wakagadzirwa, kuyerwa muTesla (T). Muchiito chekiriniki chemazuva ano, izvi zvinosiyana kubva ku0.2 kusvika ku3.0 T. Mukutsvakurudza, magineti ane simba re7 T kana kunyange 11 T uye kupfuura anoshandiswa.
-Homogeneity
