Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a...
Transcript of Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a...
![Page 1: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/1.jpg)
Magneticka rezonance (3)
J. Kybic, J. Hornak1, M. Bock, J. Hozman
April 28, 2008
1http://www.cis.rit.edu/htbooks/mri/
![Page 2: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/2.jpg)
MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 3: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/3.jpg)
Co noveho se dozvıme?
• Zname 90◦ sekvenci ≈ “gradient (recalled) echo” sekvence
• Nove sekvence: spin echo, inversion recovery
• Multislice imaging (pro zrychlenı)
![Page 4: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/4.jpg)
MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 5: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/5.jpg)
Delka snımanı pro 90◦ FID sekvenci
TR =1 s cas na jednu excitaci
×256 excitacı na rez
×20 rezu
=1 h 25min
To je prılis mnoho.
![Page 6: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/6.jpg)
Multislice imaging
Casovy diagram 90◦ FID sekvence
• Vetsina casu je nevyuzita, ceka se na odeznenı oscilace
• −→ Zatımco se ceka, je mozne excitovat jine rezy.
![Page 7: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/7.jpg)
Multislice imaging
Casovy diagram 90◦ FID sekvence
• Vetsina casu je nevyuzita, ceka se na odeznenı oscilace
• −→ Zatımco se ceka, je mozne excitovat jine rezy.
![Page 8: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/8.jpg)
Multislice imaging — excitace
• Excitace rezu se nesmı ovlivnovat
• −→ Nemenıme Gf
• −→ Pouzijeme jine frekvence RF impulsu
• Frekvence RF pulsu musı byt dostatecne vzdalene
![Page 9: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/9.jpg)
Multislice imaging — casovy diagram
![Page 10: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/10.jpg)
Multislice imaging — casovy diagram
![Page 11: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/11.jpg)
Multislice imaging — casovy diagram
![Page 12: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/12.jpg)
Multislice imaging — casovy diagram
![Page 13: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/13.jpg)
Multislice imaging — casovy diagram
![Page 14: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/14.jpg)
Multislice imaging — casovy diagram
![Page 15: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/15.jpg)
Multislice imaging — casovy diagram
![Page 16: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/16.jpg)
Multislice imaging — casovy diagram
![Page 17: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/17.jpg)
Multislice imaging — casovy diagram
![Page 18: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/18.jpg)
Multislice imaging — casovy diagram
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Multislice imaging — casovy diagram
![Page 20: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/20.jpg)
Multislice imaging — casovy diagram
Umoznuje vyrazne zrychlenı snımanı ∼ 10 min
![Page 21: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/21.jpg)
MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 22: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/22.jpg)
Sikme zobrazovanıOblique imaging
• Chceme-li sikmou rovinu rezu. . .
• −→ Pouzijeme linearnı kombinaci gradientu
![Page 23: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/23.jpg)
Sikme zobrazovanıOblique imaging
• Chceme-li sikmou rovinu rezu. . .
• −→ Pouzijeme linearnı kombinaci gradientu
![Page 24: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/24.jpg)
Sikme zobrazovanıOblique imaging
• Chceme-li sikmou rovinu rezu. . .
• −→ Pouzijeme linearnı kombinaci gradientu
![Page 25: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/25.jpg)
Sikme zobrazovanıOblique imaging
• Chceme-li sikmou rovinu rezu. . .
• −→ Pouzijeme linearnı kombinaci gradientu
![Page 26: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/26.jpg)
Sikme zobrazovanı (2)
Casovy diagram:
Gradientnı cıvky jsou zapnute soucasne.
![Page 27: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/27.jpg)
MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 28: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/28.jpg)
Spinove echo (sekvence)Spin echo
(jiz probrano — pripomenutı a rozsırenı)
• FID signal zavisı na T1
• Spin echo (spinove echo) signal zavisı i na T2
• Nektere tkane a patologie majı podobne T1, ale lisı se T2
Intenzita signalu
S ∝ %(1− e−
TRT1
)e−
TET2
![Page 29: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/29.jpg)
Spinove echo (2)
Casovy diagram:
![Page 30: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/30.jpg)
Spinove echo (3)
V casovem diagramu si vsimnete:
• Gφ mohl by byt az po 180◦ pulsu. . .
• . . .Gφ mezi 90◦ a 180◦ pulsy −→ kratsı TE
• FID signal (po 90◦ pulsu) nenı pouzit
• Aktivace desynchronizacnıho Gf spolu s Gφ . . .
• . . .−→ maximalnı synchronizace spinu uprostred snımacıhookna echa
• Frekvence je opakovana pro vsechny Gφ
![Page 31: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/31.jpg)
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MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 33: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/33.jpg)
Inversion recovery (sekvence)“Obnovenı inverze”
• Vhodnou volbou TI lze potlacit signal s urcitym T1
• Na zacatku sekvence je 180◦ impuls
• Ukazeme variantu inversion recovery + spin echo, s impulsy180◦, 90◦, 180◦
• Existuje i varianta inversion recovery + 90◦ FID
Intenzita signalu
S ∝ %(1− 2e−
TIT1 + e−
TRT1
)
![Page 34: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/34.jpg)
Inversion recovery (2)
Casovy diagram:
![Page 35: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/35.jpg)
Inversion recovery (3)
V casovem diagramu si vsimnete:
• Vsechny RF impulsy jsou selektivnı (jen rez), aplikovany spolus Gs
• Gφ nemuze byt po prvnım 180◦ pulsu (nenı transversalnımagnetizace) . . .
• . . . je aplikovano po 90◦ pulsu
• od 90◦ pulsu je spin-echo sekvence, vcetne desynchronizacnıhoGf
![Page 36: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/36.jpg)
MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 37: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/37.jpg)
Uplna a castecna relaxace
• Pro maximalnı signal cekame s dalsı excitacı na odeznenı(T1 ≈ 1 s) — dlouhe snımanı
• Mensı flip uhel −→ slabsı signal + lze kratsı cas
![Page 38: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/38.jpg)
Uplna a castecna relaxace
• Pro maximalnı signal cekame s dalsı excitacı na odeznenı(T1 ≈ 1 s) — dlouhe snımanı
• Mensı flip uhel −→ slabsı signal + lze kratsı cas
![Page 39: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/39.jpg)
Gradientnı echo
Casovy diagram:
![Page 40: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/40.jpg)
Gradientnı echo (2)
• Flip angle 10◦ ∼ 90◦
• Desynchronizacnı Gf soucasne s Gφ . . .
• . . .−→ resynchronizace (maximalnı echo) v case TE
• Gf kodujıcı frekvenci ma opacne znamenko nezdesynchronizacnı Gf (chybı 180◦ impuls)
• Kratka doba TR , i jen desıtky ms
![Page 41: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/41.jpg)
Gradient echo × spinove echoGE × SE
• Synchronizace spinu:• RF impuls u SE• gradient u GE
• Citlivost na nehomogenitu pole:• Mensı u SE, nehomogenity kompenzovany• GE mnohem citlivejsı
• Rychlost• SE pomala metoda• GE mnohem rychlejsı, zvlast pro male flip uhly
−→ GE se pouzıva je-li potrebna rychlost, napr. rychle 3D snımanı−→ SE dava kvalitnejsı obrazky (vıce signalu, mene sumu, mensıvliv nehomogenit)
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MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
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Kalibracnı cykly
• Prubehy M se stabilizujı az po nekolika cyklech
• Vlozıme nekolik kalibracnıch cyklu na zacatek snımanıkazdeho rezu
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MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
![Page 45: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/45.jpg)
KontrastJak nastavit parametry
• Parametry tkane (co chceme zobrazovat,v poradı dulezitosti)• Mrızkova relaxacnı konstanta T1 (spin-lattice)• Spinova relaxacnı konstanta T2 (spin-spin)• Hustota spinu % (spin density, proton density)• Kombinovana relaxacnı konstanta T ∗
2 (molekularnı pohyb anehomogenita)
• Parametry zobrazovanı (co muzeme ovlivnit)• Opakovacı perioda TR (repetition time)• Cas do merenı TE (echo time)• Cas inverze TI (inversion time)• Uhel φ (flip angle)• T ∗
2 (lze ovlivnovat)
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Intenzita signaluShrnutı
Spinove echo
S ∝ %(1− e−
TRT1
)e−
TET2
Inversion recovery 180◦–90◦
S ∝ %(1− 2e−
TIT1 + e−
TRT1
)e−
TET2
Gradientnı echo
S ∝ %
(1− e−
TRT1
)sin φ e
−TET∗
2
1− cos φ e−TRT1
Optimalnı (Ernstuv) uhel: cos φErnst = e−TRT1
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Typicke MRI parametryTkane hlavy
Tkan T1 [s] T2 [ms] % [rel ]
Mozkom. mok 0.8 ∼ 20 110 ∼ 2000 70 ∼ 230Bıla hm. 0.76 ∼ 1.08 61 ∼ 100 70 ∼ 90Seda hm. 1.09 ∼ 2.15 61 ∼ 109 85 ∼ 125Mozk. plena 0.5 ∼ 2.2 50 ∼ 165 5 ∼ 44Sval 0.95 ∼ 1.82 20 ∼ 67 45 ∼ 90Tuk 0.2 ∼ 0.75 53 ∼ 94 50 ∼ 100
(% = 111 pro 12mM vodny roztok NiCl2)
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Kontrast (2)
Pro tkane A, B
• Definujme kontrast jako C = SA − SB , kde SA, SB jeamplituda signalu
• Zavislost kontrastu na TR (prıklad, spin-echo; contrast curve)
• Zavislost kontrastu na TE
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Kontrast (2)
Pro tkane A, B
• Definujme kontrast jako C = SA − SB , kde SA, SB jeamplituda signalu
• Zavislost kontrastu na TR (prıklad, spin-echo; contrast curve)
• Zavislost kontrastu na TE
![Page 50: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/50.jpg)
Kontrast (2)
Pro tkane A, B
• Definujme kontrast jako C = SA − SB , kde SA, SB jeamplituda signalu
• Zavislost kontrastu na TR (prıklad, spin-echo; contrast curve)
• Zavislost kontrastu na TE
![Page 51: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/51.jpg)
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Vazene sekvence
• Sekvence s kontrastem zavisejıcım na T1 nazyvame T1
(T1 weighting)
• Sekvence s kontrastem zavisejıcım na T2 nazyvame T2
(T2 weighting)
• Sekvence s kontrastem zavisejıcım na % nazyvame sekvencespinove/protonove hustoty(spin/proton density weighting, PD)
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Volba parametru
Vazenı TR TE
T1 ≤ T1 � T2
T2 � T1 ≥ T2
% (PD) � T1 � T2
• TE � T2 −→ T2 relaxace se neuplatnı (signal nestihneklesnout)
• TR � T1 −→ T1 relaxace se neuplatnı (signal vzdy klesne nanulu)
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5
Seite 5
Repetition Time TRRepetition Time TR Inversion RecoveryInversion Recovery
time
Measurement TimingMeasurement Timingz 180° rf pulse
z Signal readout at inversion delay TI
Mz
1,00
-1,00
Spin Spin Relaxation Spin Spin Relaxation T2T2
© Plewes DB, Plewes B, Kucharczyk W.The Animated Physics of MRI, University Toronto
T2 WeightingT2 WeightingMx,y
time t
1,00
0,50
0
Mz
How to Achieve a Specific Weighting ?How to Achieve a Specific Weighting ?
TR/T1
TE/T2
1
1 T2T2--ww
T1T1--ww UU--ww
Precession for BeginnersPrecession for Beginners
Z �J�Z �J�%%��
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Typicka nastavenıSpinove echo
T1 kontrast T2 kontrast PD kontrastTR = 500ms TR = 2000ms TR = 2000msTE = 20ms TE = 80ms TE = 20ms
kost ano, voda ne kost ne, voda ano kost ano, voda anokontrast tkan/netkan kontrast mekkych tkanı hustota
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Kontrast (3)
Nazvoslovı parametru pro kontrast nenı zcela jednotne. . .
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Prıklady nastavenı — spinove echoTR TE = 20ms TE = 40ms TE = 60ms TE = 80ms
250
ms
500
ms
750
ms
1000
ms
2000
ms
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5
Seite 5
Repetition Time TRRepetition Time TR Inversion RecoveryInversion Recovery
time
Measurement TimingMeasurement Timingz 180° rf pulse
z Signal readout at inversion delay TI
Mz
1,00
-1,00
Spin Spin Relaxation Spin Spin Relaxation T2T2
© Plewes DB, Plewes B, Kucharczyk W.The Animated Physics of MRI, University Toronto
T2 WeightingT2 WeightingMx,y
time t
1,00
0,50
0
Mz
How to Achieve a Specific Weighting ?How to Achieve a Specific Weighting ?
TR/T1
TE/T2
1
1 T2T2--ww
T1T1--ww UU--ww
Precession for BeginnersPrecession for Beginners
Z �J�Z �J�%%��
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Intenzita signaluShrnutı
Spinove echo
S ∝ %(1− e−
TRT1
)e−
TET2
Inversion recovery 180◦–90◦
S ∝ %(1− 2e−
TIT1 + e−
TRT1
)e−
TET2
Gradientnı echo
S ∝ %
(1− e−
TRT1
)sin φ e
−TET∗
2
1− cos φ e−TRT1
Optimalnı (Ernstuv) uhel: cos φErnst = e−TRT1
![Page 63: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/63.jpg)
5
Seite 5
Repetition Time TRRepetition Time TR Inversion RecoveryInversion Recovery
time
Measurement TimingMeasurement Timingz 180° rf pulse
z Signal readout at inversion delay TI
Mz
1,00
-1,00
Spin Spin Relaxation Spin Spin Relaxation T2T2
© Plewes DB, Plewes B, Kucharczyk W.The Animated Physics of MRI, University Toronto
T2 WeightingT2 WeightingMx,y
time t
1,00
0,50
0
Mz
How to Achieve a Specific Weighting ?How to Achieve a Specific Weighting ?
TR/T1
TE/T2
1
1 T2T2--ww
T1T1--ww UU--ww
Precession for BeginnersPrecession for Beginners
Z �J�Z �J�%%��
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Prıklady nastavenı — inversion recovery
TR/TI 50 ms 100 ms 250 ms 500 ms 750 ms
1000
ms
2000
ms
Tecky = kalibracnı standard.TI — potlacenı urcite tkane, TR — intenzita
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Intenzita signaluShrnutı
Spinove echo
S ∝ %(1− e−
TRT1
)e−
TET2
Inversion recovery 180◦–90◦
S ∝ %(1− 2e−
TIT1 + e−
TRT1
)e−
TET2
Gradientnı echo
S ∝ %
(1− e−
TRT1
)sin φ e
−TET∗
2
1− cos φ e−TRT1
Optimalnı (Ernstuv) uhel: cos φErnst = e−TRT1
![Page 66: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/66.jpg)
Prıklady nastavenı — gradientnı echoφ TE = 25ms TE = 50ms TE = 100ms TE = 200ms
15◦
30◦
45◦
60◦
90◦
TE = 5ms
![Page 67: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/67.jpg)
Intenzita signaluShrnutı
Spinove echo
S ∝ %(1− e−
TRT1
)e−
TET2
Inversion recovery 180◦–90◦
S ∝ %(1− 2e−
TIT1 + e−
TRT1
)e−
TET2
Gradientnı echo
S ∝ %
(1− e−
TRT1
)sin φ e
−TET∗
2
1− cos φ e−TRT1
Optimalnı (Ernstuv) uhel: cos φErnst = e−TRT1
![Page 68: Magnetická rezonance (3) - CMPcmp.felk.cvut.cz/cmp/courses/ZSL2/slidy/mri3.pdf• SE pomal´a metoda • GE mnohem rychlejˇs´ı, zvl´aˇsˇt pro mal´e flip uh´ ly −→ GE](https://reader033.fdocuments.net/reader033/viewer/2022041817/5e5b52dd7a3f8020a740698c/html5/thumbnails/68.jpg)
MRI zobrazovacı technikyMultislice imagingSikme zobrazovanıSpinove echoInversion recoveryGradient (Recalled) EchoKalibraceKontrastPrumerovanı
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SNR
SNR =σsignal
σsum=
σtkan
σpozadı
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Prumerovanı
Prumerujeme N excitacı. Potom SNR′ = SNR/√
N
N = 1 N = 2 N = 4 N = 16
(Rez lahvı s vodou.)Zvlast uzitecne u rychlych metod (gradient echo).