mri basic physics
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MAGNETIC RESONANCE
For internal use only / Copyright Sie!ens AG "##$% All rights reser&ed%
MRI 'asic
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MAGNETIC RESONANCE
Magnetivitas
++
N
S
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MAGNETIC RESONANCE
Tubuh )anusia tersusun atas
atom.atom (terutama Hidrogen&
4ang berputar pada sumbun4a
+utaran ini menimbulan medan
magnet
rah dari atom.atom ini tida
searah sehingga saling
meniadaan medan magnet satusama lain
Magnetivitas Manusia
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MAGNETIC RESONANCE
Atom dalam Medan Magnet External I
N
S
Ato! a(an )ergera( searah atau )erla*anan
arah dengan arah !edan !agnet e(sternal
+'#,
Searah - .o* Energy State
'erla*anan Arah - igh Energy State
Searah 0 'erla*anan arah
1eadaan ini dina!a(an Magnetivitas
Longitudinal
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MAGNETIC RESONANCE
Magnetivitas Longitudinal
N
S
N
S
6
78
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MAGNETIC RESONANCE
Pengaruh Gelombang RF
N
S
2e!aparan gelo!)ang RF a(an
!e!)uat Ato! 3 ato! !ela(u(an
2recession dengan Fre(uensi sesuai
hu(u! .ar!or 4
5# - 6 7 '#
'e)erapa ato! a(an !engala!i
(ele)ihan energi dan pindah (e High
Energy State
1eadaan ini yang dise)ut dengan
Magnetivitas Transversal
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MAGNETIC RESONANCE
Freuensi !"erasional MRI
. Fre(uensi .ar!or - Fre(uensi Operational dari Siste! MRI
ontoh :
% ; %
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MAGNETIC RESONANCE
Magnetivitas Transversal
N
S
N
S
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MAGNETIC RESONANCE
6
7
8
N
S
7
8
6
N
S
.ongitudinalMagneti;ation
Trans&erseMagneti;ation
Esitasi
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MAGNETIC RESONANCE
Esitasi2eru)ahan dari Magneti&itas .ongitudinal !en=adi Magneti&itas Trans&ersal
(arena proses pe!aparan terhadap gelo!)ang RF +Radio Fre>uency,
Sudut yang ter)entu( saat proses E(sitasi dina!a(an dengan Flip Angle / FA
Sela!a (eadaan !agneti&itas Tran&ersal? (arena (ele)ihan energi yang diala!i
ato!
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MAGNETIC RESONANCE
Relasasi dan Resonansi
Adalah proses (e!)alinya ato! (e (eadaan a*al +E>uili)riu!, pada
Magneti&itas Tran&ersal dan Magneti&itas .ongitudinal
2roses (e!)ali (e e>uili)riu! ini !e!a(an *a(tu
Ba(tu Rela(sasi Tran&ersal dise)ut dengan T" sedang(an Ba(tu Rela(sasi.ongitudinal dise)ut dengan T8
Sela!a proses ini ato! yang (ele)ihan energi a(an !elepas(an energinya
Energi yang dilepas(an a(an ditang(ap se)agai Resonance Signal yang
a(an di (odifi(asi !en=adi data ga!)ar
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MAGNETIC RESONANCE
Relasasi
T" Ti!e
T8 Ti!e
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MAGNETIC RESONANCE
Relasasi Tranversal
Rela(sasi Tran&ersal adalah proses )eru)ahnya
arah gera(an ato! pada )idang tran&ersal dari
hanya satu phase (e!)ali (e phase a*alsa!)il !elepas energi +2roses de phase,
Ba(tu Rela(sasi Tran&ersal dise)ut dengan T"
T" - Ba(tu yang di)utuh(an untu( !ela(u(an
de phase hingga D dari nilai a*alnya
T" adalah Tissue Specific +)er)eda untu( tiap
=aringan,
T" =auh le)ih cepat dari T8
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Transverse)agnetization ()87&
Time
Echo A
Echo 'D M7y
Tissue '
Tissue A
T" A T" '
T2 Tissue -ela"ation
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MAGNETIC RESONANCE
Transversemagnetization
Time
TE
)"4
T2 Tissue -ela"ation
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Time
Short T2 TissueLong T2 Tissue
T# $ontrast
MAGNETIC RESONANCE
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MAGNETIC RESONANCE
Time
Short T2 TissueLong T2 Tissue
.ong TE
T2 @eighted Amage
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MAGNETIC RESONANCE
TE ; 28 msec TE ; 90 msec TE ; 230 msec
TR ; 3000 msec
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MAGNETIC RESONANCE
Relasasi Longitudinal
N
S
6
78
Rela(sasi .ongitudinal adalah proses
(e!)alinya !agneti&itas (e arah su!)u setelah tere(sitasi (e tran&ersal sa!)il !elepas
energi
Ba(tu Rela(sasi .ongitudinal dise)ut dengan
T8
T8 - Ba(tu yang di)utuh(an untu(!enge!)ali(an $ !agneti&itas longitudinal
T8 adalah Tissue Specific +)er)eda untu( tiap
=aringan,
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MAGNETIC RESONANCE
Bongitudinal)agnetization ()z&
Time
T8 Tissue Rela7ation
Tissue '
Tissue A
T8 A T8 '
$ M;
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Time
Short T1 Tissue
Long T1 Tissue
T% $ontrast
MAGNETIC RESONANCE
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Time
Short T1 Tissue
Long T1 Tissue
T% &eighted Image
Short TR
MAGNETIC RESONANCE
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TR ; 150 msec TR ; 500 msec TR ; 1500 msec
MAGNETIC RESONANCE
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MAGNETIC RESONANCE
Kontras Gambaran dan Waktu Relaksasi
TE
TR
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MAGNETIC RESONANCE
#2% . /%
!% . #%
3%% . ?%% #5%% . !%%%
TR (msec)
TE (msec)
Poor contrast
Poor S/N
Poor contrast
Poor S/N
T"
2roton ensityT8 H
Kontras Gambaran dan Waktu Relaksasi
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Kontras Gambaran dan Jumlah Proton
*umlah +roton HC dalam Daringan
menentuan Dumah signal echo
*aringan dengan Dumlah proton HC
lebih ban4a aan menghasilan
signal Echo 4ang lebih besar
MAGNETIC RESONANCE
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, 0 - i 0 1 t t th
T% &eighted Image
MAGNETIC RESONANCE
< Short TE 4 2er)edaan Signal dari T" tissue Rela7ation (ecil
< Short TR 4 2er)edaan Signal dari T8 Tissue Rela7ation 'ESAR
T# &eighted Image
< .ong TE 4 2er)edaan Signal dari T" tissue Rela7ation 'ESAR
< .ong TR 4 2er)edaan Signal dari T8 Tissue Rela7ation (ecil
Proton 'ensity
< Short TE 4 2er)edaan signal dari T" tissue Rela7ation (ecil. .ong TR 4 2er)edaan Signal dari T8 Tissue Rela7ation (ecil
< 2er)edaan 1ontras ditentu(an oleh =u!lah 2roton pada =aringan