1. MRI magnets have advanced to routinely use 3T systems for clinical use and up to 17T for research use. Higher field strengths provide improved image quality but also introduce disadvantages like increased chemical shift effects. 2. Gradients and RF coils have also advanced, allowing for faster imaging sequences through increased amplitude/rise time of gradients and use of parallel imaging from multiple coil elements. 3. Echo planar imaging is a fast MRI technique that acquires a whole image within a fraction of a second, enabling imaging of rapid physiological processes. It is used for diffusion weighted imaging, perfusion imaging, and functional MRI.

1. Upakar Paudel (B.Sc MIT)
UCMSTH BHAIRAHAWA
NEPAL

2. 1.Advancement in Magnets.
 It is the biggest, most expensive, and most demanding and
controlling aspect of an MRI system.
 To produce homogeneous magnetic field high field magnet
required.
 Cylindrical systems have been designed with ever
increasing aperture size.
 3Tesla system is now routinely used, Some are using up to
7T for clinical use. About 17T are using in research.
 “mission specific” magnets designed to fill specialized
needs.(interventional suite) Some magnet ability image in
sitting position.
2

3. Disadvantage of High field (3T)imaging
 Increase in excitation frequency (ω) .
 Decrease wavelength which are near to natural body
temp and cause shielding effect and interferences and
effect on RF homogeneity.(body imaging) which can
be solved by RF shimming and improved coil design.
 More chemical shift, corrected with increasing
bandwidth.
 Decreased T1 tissue contrast, and increased
susceptibility effects.
3

4. 2.Advancement in Gradients.
 With greater max amplitude and faster rise time.
 Reduced duration of RF result reduced minimum TR and TE
which increases spatial resolution by increasing matrices.
 To reduce eddy currents, it is now commonplace to have self-
shielded gradient.
 gradient tube is placed in a vacuum tube in effort to lower
acoustic noise
 Rotating gradient tube where the gradients remained on and
provided spatial encoding while it rotated.
 “Dual”gradients .(reduce dB/dt) –enable max amplitude and
rise time.
 High performance gradient enable EPI.
 Incresed cardiac imaging by faster acquisition 4

5. 3.RF Transmit and receive.
 Coils at specific parts of body.
 Using multiple receiving coil elements, the phased
array coil.(this technology is applied to other region in
addition to spine and body)
 Quadrature circular polarized coil with resulting
increased SNR.
 Tim coils are designed for Parallel Imaging from head
to toe in all 3 spatial directions.
5

6. 4.Image processing computer.
 Increased in computing power.
 Rapid imaging strategies can easily produce hundred
of image per exam.
 Dedicated array processor can perform thousands of
Fourier transformation per second.
 Innovative technique for manipulating k-space
acquisition(half Fourier and partial echo acquisition)
6

7. Dedicated peripheral “phased-array” RF surface coil for the
acquisition of multistation MR angiography
7

8. 5.Sequence advances.
 1.Single shot acquisition of breath hold T2 sequence
with half Fourier K-space filling (HASTE) –MRCP.
 2.Echoplanar imaging sequence-
8

9. Echo planar imaging.
 Echo-planar imaging is a very fast magnetic
resonance (MR) imaging technique capable of
acquiring an entire MR image in only a fraction of a
second. In single-shot echo-planar imaging, all the
spatial-encoding data of an image can be obtained
after a single radio-frequency excitation.
 echo-planar imaging offers major advantages over
conventional MR imaging, including reduced
imaging time, decreased motion artifact, and the
ability to image rapid physiologic processes of the
human body.
9

10.  Echo-planar imaging can be performed by using single
or multiple excitation pulses (“shots”). The number of
shots represents the number of TR periods required to
complete the image acquisition.
 Clinical applications of EPI:
 Diffusion weighted MR
 Perfusion weighted MR
 Functional MR.
 Heart imaging.
 GI motility imaging.
10

11.  Conventional SE imaging. Within each TR period, the pulse
sequence is executed and one line of imaging data or one phase-
encoding step is collected. The frequency-encoding gradient
(Gx), phase-encoding gradient (Gy), and section-selection
gradient (Gz) are shown during one TR period. RF = radio
frequency. 11

12.  Echo-planar imaging. Within each TR period, multiple
lines of imaging data are collected.Gx = frequency-
encoding gradient, Gy = phase-encoding gradient, Gz =
section-selection gradient.
12

13. A. Diffusion weighted MRI.
 Term to describe random thermal motion of molecule.
 Restricted by boundaries.
 Sometime restriction in diffusion is directional depending
on structure of tissue.
 DWI sequences are acquired with ultrafast sequence ,EPI
with two large gradient pulses applied after excitation.
 Gradient pulse cancel each other if spins do not move,
while moving spins experienced phase shift.
 So in DWI sequences signal attenuation occur in normal
tissue with random diffusion and bright signal appear
in tissue with restricted diffusion (e.g ischemia)
13

14. 14

15. 15

16.  A gradient pulse unrelated to the imaging gradients and at a
certain duration ( ) is applied to the spins. This gradient
causes net dephasing of the spins. Now, after a certain time
(∆), the spins are rephased by applying either an equal and
opposite gradient or, if a 180 degree pulse has been applied in
the interim, an equal and same polarity gradient.
 All spins that were stationary will be rephased, however,
spins that moved during the time(∆) will feel a different
rephasing gradient than that encountered during the
dephasing pulse and thus will not be rephased.
 Extremely prone to motion.
16

17. 17

18. 18

19.  If multi-shot sequences are used for DWI phase
change will be different for different lines of k-space
and strong artifact will appear along phase direction.
 Additional echoes called navigator echo is generated
and used to correct artifact during post processing.
 Stroke imaging by DWI –can show irreversible
and reversible ischemic lesion.
19

20.  The amount of attenuation depends on amplitude and
direction of diffusion gradient.
 Diffusion gradient in X,Y,Z direction are combined to
produce diffusion image.
 When diffusion gradient are applied only in X, and Y
direction slight signal change may reflect direction of axon.
 Diffusion gradient most be long and strong for enough
DWI weighting.
 Diffusion sensitivity “b” –It determines diffusion
attenuation by modification of duration and amplitude of
diffusion gradient. (b-S/mm2 )
20

21. Contains contribution from spin density and relaxation times T1 and
T2; therefore, the hyperintense lesion on a diffusion-weighted image
may reflect a strong T2 effect (T2 "shine-through" effect) instead of
reduced diffusion.
21

22. 22

23.  Because the ADC values of gray and white matter
are similar, typically there is no contrast between
gray and white matter on the exponential image
or ADC map. The contrast between gray and white
matter seen on the DW image is due to T2-
weighted contrast.
 This residual T2 component on the DW image makes
it important to view either the exponential image or
ADC map in conjunction with the DW image.
 In lesions such as acute stroke, the T2-weighted and
DW effects both cause increased signal intensity on
the DW image. Therefore, we have found that we
identify regions of decreased diffusion best on ADC
images.
23

24.  An ADC map shows parametric images containing the apparent
diffusion cofficient of diffusion weighted image
 Term apparent refers to the dependence of these coefficients on
factors other than prior molecular mobility. Also called diffusion
map.
 The ADC is actually a tensor quantity or a matrix:
 The diagonal elements of this matrix can be combined to give
information about the magnitude of the apparent diffusion:
(ADCxx + ADCyy + ADCzz)/3.
24

25. Anisotropic nature of diffusion in the brain.
Schaefer P W et al. Radiology 2000;217:331-345
©2000 by Radiological Society of North America 25

26. 26

27.  To remove T2 contrast transverse DWI image is
divided with images having same parameter except
different b value.
27

28.  Creation of ADC map mathematically manipulating
exponential image.
28

29.  Diffusion-weighted EPI sequence. (a) b = 0 s
mm–1. (b) b = 500 s mm–1. (c) b = 1000 s
mm–1. Normal tissue has moderate diffusion
of water, whereas tissue under stress, such as
that at risk for a stroke, has restricted
motion of tissue water and shows increased
signal on image with significant diffusion
sensitivity (c).
29

30. Diffusion tensor imaging (DTI)
 Is rapidly evolving noninvasive MRI technique for
delineating the anatomy and pathology of white
matter tracts.
 Useful for presurgical planning in patients with intra-
axial, focal mass lesions.
 Delineation of the various tracts around a focal lesion
and knowledge of the status of infiltration vs
displacement , that help neurosurgeons decide on the
appropriate surgical approach.
30

31. DTI
 For DTI, several directions are required, as white
matter in the brain is anatomically present in different
directions.
 Diffusion in the brain is not uniform but anisotropic,
along the direction of the various fiber tracts.
 diffusion tensor (D)- measurement of water diffusion
in different directions
 At least six noncollinear directions and an image
without diffusion weighting are needed in order to
calculate D.
 From this, the tensor ‘eigen values and eigenvectors’
can be derived.The eigenvalues represent the
magnitude of diffusion, whereas eigenvectors
represent the corresponding direction.
31

32.  The anisotropic part of diffusion in a tissue is measured by
fractional anisotropy (FA).
 FA values will alter in any area where there is a focal brain
lesion, causing alteration in the white matter tract.
 Color intensity was scaled in proportion to the magnitude
of FA
 From these FA maps, DTI-based color-coded maps can be
generated.
 In these maps, colors are chosen according to the high
eigenvector associated with the largest eigenvalue. In most
MRI machines, red is assigned to the x-direction (left to
right), green to the y-direction (anterior-posterior), and
blue to the z-direction (superior-inferior).
32

33. 33

34. Fiber tractography.
 By combining the anisotropy data with the
directionality it is possible to estimate fiber
orientation.
 Fiber tractography in which three-dimensional
pathways of white matter tracts can be reconstructed.
In this algorithm, called ‘fiber assignment by
continuous tracking’ (FACT), reconstruction of the
tract is performed by sequentially piecing together
discrete and shortly spaced estimates of fiber
orientation to form continuous trajectories.
34

35. Whole brain tractography of the human in vivo data using the corpus callosum as a ROI,
with directions: left – right (red), superior –
inferior (blue), anterior – posterior (green).
35

36.  Cingulum, sagittal view. A, Illustration shows the cingulum arching over the
corpus callosum. B, Gross dissection, median view. C, Directional map. Because
DTI reflects tract orientation voxel by voxel, the color changes from green to
blue as the cingulum (arrows) arches around the genu and splenium
(arrowheads). Green indicates anteroposterior; red, left-right; blue, superior-
inferior. D, Tractogram. 36

37. DTI pattern 1: normal anisotropy, abnormal
location or orientation. A–E, T2-weighted MR
image (A), contrast- enhanced T1-weighted
image (B), directional maps in axial (C) and
coronal (D) planes, and coronal tractogram of
bilateral corticospinal tracts (E). WM tracts
are deviated anteriorly, inferiorly, and
posterolaterally by this ganglioglioma but
retain their normal anisotropy. Therefore,
they remain readily identified on DTI (C and
D) and readily traced with tractography (E).
The AC (red, arrowhead), IOFF (green, open
arrow), and CST (blue, solid arrows) are
deviated. Note the blue hue of the CST change
to red as it deviates toward the axial plane by
the tumor (arrow on coronal view [D]).37

38.  Potential patterns of WM fiber tract alteration by cerebral
neoplasms. The extent to which these patterns can be
discriminated on the basis of DTI is under investigation.
38

39.  DTI pattern : tract
unidentifiable. A–
D, T2-weighted MR
image (A),
contrast-
enhanced T1-
weighted image
(B), FA map (C),
and directional
map (D). This
high-grade
astrocytoma has
destroyed the body
of the corpus
callosum,
rendering the
diffusion
essentially
isotropic and
precluding
identification on
the directional
map (arrow).
39

40. Whole body diffusion.
 diffusion-weighted whole-body imaging with
background body signal suppression” (DWIBS) now
allows acquisition of volumetric diffusion-weighted
images of the entire body
 Thin DWI images can be
combined to form reformatted.
(coronal image with rectal
Ca and LN inversed image)
Application-Onco imaging.
40

41. B.PERFUSION WEIGHTED MR
 Although angiographic techniques visualize the vascular
network within a patient, they do not have sufficient
spatial resolution to visualize blood flow through a tissue
in bulk. However, it is possible in many instances to
observe changes in tissue signal due to the blood flow
through it, a process known as perfusion.
 Proper tissue perfusion is critical to ensure an adequate
supply of nutrients to the constituent cells as well as
removal of metabolic byproducts. It also aids in
maintenance of a stable tissue temperature.
 Abnormalities in perfusion can lead to an increased
temperature sensitivity and a loss of tissue viability
through hypoxia.
41

42. .
 It is measure of quality of vascular supply to tissue
vascular supply and metabolism are related perfusion
can be used to measure tissue activity.
 Measured by tagging the water in arterial blood during
image acquisition.
 Tagging can be done by IV GD or by saturating the
proton in arterial blood by RF inversion.
 Difference between tagged and un tagged image is
small- ultrafast imaging method are required to reduce
artifact.
 Fast scanning –before, during and after contrast
injection.
42

43. Three approach for perfusion
imaging.
 First one approach acquires a series of rapid (less
than 20 seconds per image) T1-weighted imaging
studies following the bolus administration of a
gadolinium-chelated contrast agent. These images
are typically acquired using spoiled gradient echo, T1-
weighted magnetization prepared or echo planar
techniques. An increase in tissue signal occurs as the
contrast agent infuses the extravascular spaces of the
tissue. Perfusion defects are visualized as a lack of
signal increase for the affected region of tissue.
43

44. 2.Second approach is useful if the contrast
agent remains in the blood vessels, such as in
cerebral tissue with an intact blood–brain
barrier. In this case, the paramagnetic nature
of the contrast agent increases the local tissue
susceptibility, causing increased T2*
dephasing of nearby tissues. Serial T2*-
weighted gradient echo or echo planar
sequences are acquired, and the well-perfused
tissue exhibits a reduction of signal relative to
the precontrast images or the poorly perfused
tissues.
44

45. 3.The third approach does not use contrast media
to highlight the flowing spins. Instead, two sets of
images are acquired using an EPI pulse sequence.
One set is acquired following a region-selective
inversion pulse that inverts or “tags” the spins
outside the slice of interest, whereas the other set of
images serves as a reference. A variable delay time
between the tagging pulse and the data collection
allows control of the tag position based on the flow
velocity.
45

46. Application.
 Two areas in which perfusion studies have shown
promise are the examination of abnormalities of
blood flow within tissue and the detection of
tumors.(cerebral ischemia early detection)
46

47.  43-year-old man with acute onset of left-sided weakness
and visual changes who was found to have left
homonmous hemianopsia on examination. A,
Unenhanced CT scan reveals negative finding for
cortical infarction. B, T2-weighted MR image shows
increased signal (arrow ) in right calcarine cortex. C,
Diffusion-weighted scan demonstrates larger area of
signal abnormality (arrow) involving right occipital
lobe, consistent with infarction. D, Color-coded
cerebral blood volume map obtained using dynamic
T2-weighted technique shows even larger perfusion
deficit than that seen in B and C in right occipital
lobe, including infarction core, and surrounding tissue at
risk. Red denotes high cerebral blood volume; blue, low
cerebral blood volume. E, Color-coded mean transit
time map obtained using dynamic T2-weighted
technique shows prolonged transit time in right
occipital lobe, also corresponding to infarct core, and
surrounding tissue at risk. Red denotes prolonged mean
transit time; yellow, normal mean transit time.
47

48.  24-year-old woman with previously treated high-grade cerebral neoplasm (anaplastic ependymoma)
with an enhancing lesion on follow-up examination. Biopsy revealed radiation necrosis. A, Contrast-
enhanced axial T1-weighted image shows area of abnormal enhancement in right
frontoparietal deep white matter. B, Color-coded cerebral blood volume map obtained using
dynamic T2-weighted technique illustrates low cerebral blood volume in area of abnormal contrast
enhancement seen in A. Red denotes high cerebral blood volume; blue, low cerebral blood
volume. C, Overlay of color-coded cerebral blood volume map on T1-weighted image with
cerebral blood volume map thresholded so only voxels with cerebral blood volume values equal to or
higher than that of gray matter are depicted. Note that area of enhancement in right frontoparietal
deep white matter has low cerebral blood volume relative to gray matter, consistent with radiation
necrosis.
48

49. C.MRS
 MR spectroscopy provides a measure of brain chemistry.
The most common nuclei that are used are 1H (proton),
23Na (sodium), 31P (phosphorus).
 Proton spectroscopy is easier to perform and provides
much higher signal-to-noise than either sodium or
phosphorus.
 Proton MRS can be performed within 10-15 minutes and
can be added on to conventional MR imaging protocols.
 It can be used to serially monitor biochemical changes
in tumors, stroke, epilepsy, metabolic disorders,
infections, and neurodegenerative diseases.
 The MR spectra do not come labeled with diagnoses. They
require interpretation and should always be correlated with
the MR images before making a final diagnosis.
49

50.  The resonant frequencies of nuclei are at the lower end
of the electromagnetic spectrum between FM radio
and radar.
 10 MHz at 0.3 T to about 300 MHz on a 7 T.
 higher field strength are higher signal-to-noise and
better separation of the metabolite peaks.
 In a proton spectrum at 1.5 T, the metabolites are
spread out between 63,000,000 and 64,000,000 Hertz.
 The resonant frequencies expressed in in parts per
million (ppm)
 NAA at 2.0 ppm and let the other metabolites fall into
their proper positions on the spectral line.
50

51.  In MR imaging, the total signal from all the protons in
each voxel is used to make the image.
 If all the signal were used for MRS, the fat and water
peaks would be huge and scaling would make the other
metabolite peaks invisible.
 Fat and water are eliminated-
1.Fat is avoided by placing the voxel for MRS within the
brain, away from the fat in bone marrow and scalp.
2. Water suppression is accomplished with either a CHESS
(Chemical-Shift Selective ) or IR (Inversion Recovery)
technique. These suppression techniques are used with a
STEAM or PRESS pulse sequence acquisition
51

52.  STEAM (Stimulated Echo Acquisition Mode) pulse
sequence uses a 90o refocusing pulse to collect the signal
like a gradient echo.
 STEAM can achieve shorter echo times but at the expense
of less signal-to-noise.
 The PRESS (Point Resolved SpectroScopy) sequence
refocuses the spins with a 180o RF pulse like a spin echo.
 Two other acronyms are. CSI (Chemical Shift Imaging)
refers to multi-voxel MRS. SI (Spectroscopic Imaging)
displays the data as an image with the signal intensity
representing the concentration of a particular metabolite.
52

53.  Fourier transform is then applied to the data to
separate the signal into individual frequencies.
 Protons in different molecules resonate at slightly
different frequencies because the local electron cloud
affects the magnetic field experienced by the proton.
53

54. TE affect information obtained in MRS.
 With a short TE of 30 msec, metabolites with both short
and long T2 relaxation times are observed.
 With a long TE of 270 msec, only metabolites with a long
T2 are seen, producing a spectrum with primarily NAA,
creatine, and choline.
 Single voxel, short TE technique is used to make the
initial diagnosis, because the signal-to-noise is high and
all metabolites are represented.
 Multi-voxel, long TE techniques are used to further
characterize different regions of a mass and to assess
brain parenchyma around or adjacent to the mass,
assess response to therapy and to search for tumor
recurrence
54

55. Each metabolite appears at a specific ppm, and each one reflects specific
cellular and biochemical processes.
55

56.  NAA is a neuronal marker and decreases with any
disease that adversely affects neuronal integrity.
 Creatine provides a measure of energy stores.
 Choline is a measure of increased cellular turnover and
is elevated in tumors and inflammatory processes.
 The observable MR metabolites provide powerful
information.
56

57. gray matter has more creatine
57

58. Hunter's angle is the line formed by the
metabolites on the white matter
spectrum
58

59.  Normal MR spectra
obtained from gray
matter and white matter
are shown on the right.
The predominant
metabolites, displayed
from right to left, are
NAA, creatine, choline,
and myo-inositol.
 The primary difference
between the two spectra
is that gray matter has
more creatine.
 Hunter's angle is the
line formed by the
metabolites on the
white matter spectrum.
 The common way to
analyze clinical spectra is
to look at metabolite
ratios, namely NAA/Cr,
NAA/Cho, and Cho/Cr.
59

60. Application.
 MRS can be used to determine the degree of malignancy.
 As malignancy increases, NAA and creatine decrease, and
choline, lactate, and lipids increase.
 To get an accurate assessment of the tumor chemistry, the
spectroscopic voxel should be placed over an enhancing region
of the tumor, avoiding areas of necrosis, hemorrhage,
calcification, or cysts.
 Multi-voxel spectroscopy is best to detect infiltration of
malignant cells beyond the enhancing margins of tumors.
 Cerebral glioma, elevated choline levels are frequently
detected in edematous regions of the brain outside the
enhancing mass.
 MRS can direct the surgeon to the most metabolically active
part of the tumor for biopsy to obtain accurate grading of the
malignancy.
60

61.  To distinguish-radiation necrosis and tumor
recurrence-(Recurrence-elevated choline and
radiation necrosis low NAA choline and creatine with
elevated lipid and lactate).
 cerebral hypoxia and ischemia- elevated lactate.
 brain abscesses destroy or displace brain tissue, so
NAA is not present.
61

62. D.fMRI
 Functional MRI (fMRI) is a magnetic resonance
imaging (MRI)-based neuroimaging technique which allows us
to detect the brain areas which are involved in a task, a
process or an emotion.
 CBF change induced by stimulation has been used for
mapping brain functions.
 In 1990, Ogawa and colleagues at AT&T Bell Laboratories
reported that functional brain mapping is possible by using the
venous blood oxygenation level-dependent (BOLD)
magnetic resonance imaging (MRI) contrast. The BOLD
contrast relies on changes in deoxyhemoglobin (dHb), which
acts as an endogenous paramagnetic contrast agent. Therefore,
changes in the local dHb concentration in the brain lead to
alterations in the signal intensity of magnetic resonance images
(MRI).
62

63.  Oxygenated hemoglobin is diamagnetic, with a
very small magnetic moment.
 deoxygenated hemoglobin has a significant
paramagnetic moment.
 Concentrations of deoxygenated hemoglobin shorten
the T2* relaxation time of the tissue and result in a
decrease in signal compared to tissue with oxygenated
hemoglobin.
 High magnetic field strengths (1.5 T or greater) are
necessary to increase the change in T2* between
activated and nonactivated tissue.
63

64.  Activation-Stimulated tissue undergoes an increase in
blood flow ( oxygenated hemoglobin).
 As deoxygenated hemoglobin decreases within the
tissue. reducing the concentration of paramagnetic
molecules. This condition reduces the amount of
susceptibility dephasing induced and thereby increases
the T2* time for the stimulated tissue relative to
unstimulated.
 As a result, the stimulated tissue appears higher in
signal on T2*-weighted images. This phenomenon is
known as the blood oxygenation-level-dependent
effect or BOLD effect..
64

65.  In fMRI –use to perform a large series of
measurements in the presence and absence of the
stimulus and subtract the images, leaving pixels
presumably from the activated region of tissue.
 Correction for patient movement between
measurements must be performed.
 The correlation coefficient of the voxel intensity and
the time variation of the stimulus is also calculated to
ensure that the observed variation is in response to the
stimulus
65

66. Ac | Functional
MRI (fMRI) during finger tapping identifies the brain
regions associated with hand movement.. d | fMRI
with sensory stimulation of the left foot identifies
regions that, if injured during tumour resection, could
be expected to lead to greater functional impairments 66

67. Application of fMRI
 Presurgical mapping of eloquent brain areas (motor,
language,...)
 Assessment of plasticity after a brain injury.
 Assessment of patients with disorders of consciousness
(coma, vegetative state, minimally conscious state, locked-in
syndrome)
 Mapping of complex functions (emotions, motor control,
specialized language functions,...) in normal and pathological
conditions
 Monitoring of treatment response
 Neuromarketing
 Lie detector
 Mind reading.
67

68. Parallel Imaging Technique.
 Parallel acquisition techniques combine the signals of
several coil elements in a phased array to reconstruct
the image.
 combining the signal of several coil arrays. The spatial
information related to the phased array coil elements is
utilized for reducing the amount of conventional Fourier
encoding.
 To improve the SNR or to accelerate acquisition and reduce
scan time.
 A shorter scan time enables breath-hold sequences or
improves the temporal resolution of dynamic scans.
 Improve image quality(better spatial resolution, reduced
artifacts).
68

69. Two type recon algorithm.
 Algorithms that reconstruct the global image from the
images produced by each coil (reconstruction in the
image domain, after Fourier transform): SENSE
(SENSitivity Encoding), PILS (Partially Parallel
Imaging with Localized Sensitivity), ASSET (Array
Spatial Sensitivity Encoding Technique)
 Algorithms that reconstruct the Fourier plane of the
image from the frequency signals of each coil
(reconstruction in the frequency domain, before
Fourier transform): GRAPPA (GeneRalized Auto-
calibrating Partially Parallel Acquisition)
69

70. Application.
 Echo-planar (Diffusion imaging, diffusion tensor and
perfusion imaging): enhanced spatial resolution,
reduced artifacts (related to the sensitivity of the echo-
planar to magnetic susceptibility artifacts)
 Cardiac, abdominal imaging
 Magnetic resonance angiography
 Ultra high field MRI
70

71. Whole body MRI screening.
 High performance gradient linked to automated table
movements enable rapid imaging covering whole
body.
 Fast T1W and T2W sequence can be planned with
automated sequential movement of patient through
MR scanner.
 Images taken whole body sag/cor plane.
 Whole body STIR for nodal assessment in tumor.
71

72. 72

73. Whole bod MR
angiography
(A) combined
from five 3D
data sets,
which were
acquired over a
total period of
72
seconds
73

74. Future.
 Higher strength and RF power system with RF safety
mechanism.
 Drug delivery monitoring and therapeutic application
of MR.
 MR linking with digital fluoroscopy single
exam/operating room allowing easy patient movement
between modalities.
74

75. Refrences.
 Article Pamela W. Schaefer, MD, P. Ellen Grant, MD
and R. Gilberto Gonzalez, MD, PhD.
 MRI principle and application-Mark K.Brown.
 MRI in practice Catherine westbrook.
75

76. Thank you.
76