mi basics 9125
, URI is variable
/configurable/flexible
noisy
based statistics
analysis on> >
modes options/alternatives
many
3 tissues
wm =>
myelinatedthan
axons
csf => clear fluid in ventricles
,
GM on T1
lighter cisterns , subara
GM darker TelFLAR
.
on
space
darhypnte
6m = neuronal cell bodies , dendrites , synapses T1-
context deep thalamus T2f
darker
nuclei
(bg ,
on T1
lighter on T2
now uRI works Heb
X
·
body has lots of H atoms
(mainly in water) ,
these It nuclei
-
like protons
act
tiny magnets
inside
strong external magnetic field (Bo), many of these
·
a
protons align either with or against the field
·
an RF pulse is applied at the "larmor frequency", which
tips the alignment from the magnetic field
proton away
this moves them into
high-energy , unstable state
after the RF pulse stops, protons return to their
original
·
alignment via 2 main processes :
the time it takes protons to
Te relaxation llongitudinal) realign with the me
T2 relaxation (transverse) >
=
the time it takes for their spins
to de-phase close coherence)
as protons relax
they emit RF
signals which are picked up
·
,
bydetectors
gradient magnetic fields, the MRI encodes spatial
using system
·
information so that the signals can be reconstructed into
which location
an
image (which noxel correspones to
·
by selecting specific timings (TE : echo time, TR : repetition time) ,
different tissue types will appeardifferently
variation contrast btw soft
pros=> ionizing
no , excellent
tissue , versatile
cons => expensive , sensitive to motion ,
relatively flow
, Sep 8 , 2025
after RF pulse
signalsdecaying lecture I
3 main quantities
(1) density of water + feet) proton density
(2) Te relaxation time to
=> sensitive D
tissue
(3) Te relaxation time type
tissue types
· molecular tumbling
Speed
cortical surfaces + thickness
↑
subcortical structure+
Snape
localM
changes
structural URL does bone from air
4 . not
distinguith
limitations : 5. Subcortical areas - poor contrast
direct measure 6 miss certain
.
1 no .
single sequence may
2 .
Not quantitative things completely
artefacts noise
.
3 Tele values vary within GM/WM 7 +
Contrast manipulated by URL Sequence timing
Th weighting
M < Th COF
[H+]
weighting Th
weighting
WM < To T2 WM( Te Gu << Te CSF
short repetition timeCTR) long TR
long TR
Short echo time (TE) Short TE
long TE
, URI is variable
/configurable/flexible
noisy
based statistics
analysis on> >
modes options/alternatives
many
3 tissues
wm =>
myelinatedthan
axons
csf => clear fluid in ventricles
,
GM on T1
lighter cisterns , subara
GM darker TelFLAR
.
on
space
darhypnte
6m = neuronal cell bodies , dendrites , synapses T1-
context deep thalamus T2f
darker
nuclei
(bg ,
on T1
lighter on T2
now uRI works Heb
X
·
body has lots of H atoms
(mainly in water) ,
these It nuclei
-
like protons
act
tiny magnets
inside
strong external magnetic field (Bo), many of these
·
a
protons align either with or against the field
·
an RF pulse is applied at the "larmor frequency", which
tips the alignment from the magnetic field
proton away
this moves them into
high-energy , unstable state
after the RF pulse stops, protons return to their
original
·
alignment via 2 main processes :
the time it takes protons to
Te relaxation llongitudinal) realign with the me
T2 relaxation (transverse) >
=
the time it takes for their spins
to de-phase close coherence)
as protons relax
they emit RF
signals which are picked up
·
,
bydetectors
gradient magnetic fields, the MRI encodes spatial
using system
·
information so that the signals can be reconstructed into
which location
an
image (which noxel correspones to
·
by selecting specific timings (TE : echo time, TR : repetition time) ,
different tissue types will appeardifferently
variation contrast btw soft
pros=> ionizing
no , excellent
tissue , versatile
cons => expensive , sensitive to motion ,
relatively flow
, Sep 8 , 2025
after RF pulse
signalsdecaying lecture I
3 main quantities
(1) density of water + feet) proton density
(2) Te relaxation time to
=> sensitive D
tissue
(3) Te relaxation time type
tissue types
· molecular tumbling
Speed
cortical surfaces + thickness
↑
subcortical structure+
Snape
localM
changes
structural URL does bone from air
4 . not
distinguith
limitations : 5. Subcortical areas - poor contrast
direct measure 6 miss certain
.
1 no .
single sequence may
2 .
Not quantitative things completely
artefacts noise
.
3 Tele values vary within GM/WM 7 +
Contrast manipulated by URL Sequence timing
Th weighting
M < Th COF
[H+]
weighting Th
weighting
WM < To T2 WM( Te Gu << Te CSF
short repetition timeCTR) long TR
long TR
Short echo time (TE) Short TE
long TE
