RADIOLOGY FOR CRANIAL STEREOTAXY

1. Imaging for cranial stereotaxy
Structural to Functional
Dr Kanhu Charan Patro
HOD, Radiation Oncology
MGCHRI, Visakhapatnam
M +91 9160470564, drkcpatro@gmail.com 1

2. What a radiation oncologist wants?
• Clear identification
• Target
• OAR
• Good resolution
2

3. Situation
• Metastasis
• Vestibular schwannoma
• Meningioma
• AVM
• Pituitary
• Reirradiation
• Trigeminal neuralgia
• Glomus jugular
• Cavernomas
• Hamartomas
• Cysts
• Spine
3

4. Ammunitions
• CT
• Plain
• Contrast
• Cisternography
• CT Angio
• MRI
• Plain
• Contrast/Double Contrast/Triple contrast
• Cisternography
• MR Angio
• MRS
• Other Functional sequences
• Nuclear imaging
• DSA-Digital Subtraction Angiogram
4

5. Basics
• Slicing
• Windowing
• CT number
• Measuring the density
• Contrast
• FOV vs BORE
5

6. Slicing
6

7. Sagittal[s-s] Coronal[A-P] Axial[S-I]
Side view Front view Bottom up view
7

8. Slicing
8

9. Imaging planes
9

10. 10

11. A. Brightness refers to the overall lightness or
darkness of the image.
B. Contrast is the difference in brightness between
objects in the image.
11

12. Brightness- window level Contrast- window width
12

13. 13WIDTH
LEVEL

14. 14

15. Bore
15

16. FOV
• (FOV) The field of view is the
maximum diameter of the
area of the scanned object that is
represented in the reconstructed
image.
• FULL FOV
16

17. Describing the tissues/organs
Procedure Like brain Less than brain
Darker
More than brain
Whiter
CT SCAN Isodense Hypodense Hyperdense
MRI Isointense Hypointense Hyperintense
17

18. 18

19. Hounsfield unit
• CT number
• Different for different tissue
• Related to composition of tissue
19

20. 20

21. 21

22. 22

23. Contrast
23

24. MRI BRAIN SEQUENCES IN STEREOTAXY
24

25. Images
• Structural imaging refers to approaches that are specialized for the
visualization and analysis of anatomical properties of the brain.
• Functional magnetic resonance imaging, or fMRI, is a technique for
measuring brain activity. It works by detecting the changes in blood
oxygenation and flow that occur in response to neural activity
• Tractography is a 3D modeling technique used to visually represent nerve
tracts using data collected by diffusion MRI. It uses special techniques of
magnetic resonance imaging and computer-based diffusion MRI.
25

26. What is a Sequence?
• Sequence of events in MRI
machine
• By varying the sequence of RF
pulses applied & collected,
different types of images are
created
• PHILIPS
• GE
• TOSHIBA
• SIEMENS
• HITACHI
26

27. Playing with TR and TE and RF
• TR
• Repetition time
• The time between two
excitations
• TE
• Echo time
• The time interval in which
signals are measured after RF
excitation
27

28. Playing with TR and TE and RF
28

29. 29

30. T1 sequence
•T1
•Fat bright[white]
•Water black
•Normal anatomy
•Vascular changes
30
w w

31. T1 contrast
• T1 contrast • T1 contrast
• Vessels -hyperintense
31

32. T2 sequence- Flip side of T1
•T2
• CSF, AQ/VT HUMOR WHITE
•Fat black/white mater
•Water white
•Blood vessel dark
•CSF study
•Lesions in brain
32

33. Flair sequence
• Fluid attenuation inversion
recovery
• Flair-ventricular ooze
• CSF black
• Pathological fluid white
33

34. T2 vs FLAIR- Flip side of T2
34

35. Identify-T1 VS T2 VS FLAIR
35

36. MR Diffusion
• Ghost sequence
• Diffusion weighted image
• DWI
• Fluid restriction
• Whiter
36

37. ADC MAP
• Apparent diffusion coefficient
• Statistical measure of restriction
• ADC measuring the diffusion
• ADC without T2 effect –black
• Hyperintense on DWI
• Hypointense in ADC
• More malignant –lower the
value
37

38. ADC values
38

39. Planning MRI
39
FOV should
include body
contour

40. Disease specific MRI sequences
DISEASE SEQUENCE
 NORMAL ANATOMY 3D FSPGR
 PITUITARY ADENOMA STIR
 TRIGEMINAL NEURALGIA FIESTA
 CRANIAL NERVES CISS
 CP ANGLE TUMOR GRE
 GLIOMA DIFFUSION,PERFUSION
 AVM ANGIO
 GRADING OF TUMORS MRS
 METASTASIS DOUBLE/TRIPLE/DELAYED CONTRAST
DIFFUSION,PERFUSION 40

41. FSPGR Sequence
• [3D FSPGR (fast spoiled gradient
echo)
• More differentiation of normal
structure
• Contrast as well as non contrast
• Improves anatomical display
41

42. 42

43. FIESTA sequence
• FIRST IMAGING EMPLOYING
STEADY STATE ACQUSITION
• Clear visualization of ventricles
• Cranial nerves AT SKULL BASE
• Cisterns
43

44. STIR sequence. Fat saturated/FATSAT sequence
• Short tau inversion recovery
• These chemically selective
pulses cause the signal
from fat to be nulled (saturated)
• Packing materials
• Gel foam
• Fat
44

45. MRS
• Magnetic resonance spectroscopy
• Chemical measurement
• Grading differentiating the tumours
45

46. Chemical composition of brain-MRS
46

47. MRS-low grade vs high grade
47

48. MRS- Meningioma
48

49. MR Angio
• Magnetic resonance angiography is
used to generate images of arteries in
order to evaluate them for stenosis,
occlusions, aneurysms or other
abnormalities
49

50. MR perfusion
1. Sequence to see perfusion of
tissues
2. The acquired data are then post-
processed to obtain perfusion maps
with different parameters, such as
BV (blood volume), BF (blood flow)
3. The main role of perfusion imaging
is in evaluation of ischemic
conditions and neoplasms (e.g.
identify highest grade component
of diffuse astrocytoma help to
distinguish glioblastomas from
cerebral metastases) and
neurodegenerative diseases.
50

51. Types of MR perfusion scan
51
BEYOND OUR SCOPE

52. Gradient echo sequence
• Gradient recalled echo (GRE) (T2
WI) is a relatively new (MRI)
technique.
• GRE T2 WI can detect the
smallest changes in uniformity
in the magnetic field and can
improve the rate of small lesion
detection
• Detection and Evaluation of
Microbleeds
52

53. Planning MRI for metastasis
Planning MR
• MRI brain
• T1/T2/Flair
• 3DFSPGR contrast
• No gap
• No tilt
• Neutral neck
• 1mm slice
• 512 X 512 Matrix
• Full FOV
Specific sequences
• Contrast
• Double
• Triple
• Delayed
53

54. Double contrast-resolution changes
54

55. Double contrast- volume changes
55

56. Double/triple contrast-number changes
56

57. More tesla
57

58. Delayed contrast
NO
LESION
10min 15 min
Marina Kushnirsky/JNS/2016 58
Delayed MRI after contrast injection revealed more targets that needed treatment

59. Different contrast agent-the lesion increases
E.S. Kim/.AJNR/2010
59
DD 1.0-mol/L gadobutrol provides higher lesion conspicuity and enhances lesion
detection in brain metastasis compared with DD 0.5-mol/L gadolinium contrast agents

60. Planning MRI for trigeminal neuralgia
Planning MR
• MRI brain
• T1/T2/Flair
• 3DFSPGR contrast
• No gap
• No tilt
• Neutral neck
• 1mm slice
• 512 X 512 Matrix
Specific sequences
• FIESTA/CISS sequence
• Cranial nerve
• Brain stem
• T2 for cochlea
• MR Angio all planes/TOF
• CT/MR cisternography
• Same slice thickness for CT AND
MR
60

61. CT Cisternography procedure
• Pre contrast CT performed
• A spinal tap (lumbar puncture) is done first.
• Small amounts of contrast material are injected into the fluid within the
spine.
• The needle is removed immediately after the injection.
• Then patient placed in toted positioned with foot end elevation.
• Seral scans taken- 1 to 6 hours after getting the injection.
• Cranial nerves
• Ventricles
• Cisterns
• Brainstem
61

62. CT Cisternography
62

63. MRI and CT of trigeminal nerve
TRIGEMINAL NERVE MRI T2 TRIGEMINAL NERVE CT CYST. TRIGEMINAL NERVE CT CYST.
TG. NERVE MRI T2 CORONAL TG. NERVE MRI T2 CORONAL BLACK-SUP. CEREBELLAR A
ARROW HEAD-COCHLEA
Meckel's cave(white arrowhead)
TRIGEMINAL NERVE
63

64. MR Cisternography
64

65. The conflict
65

66. Planning MRI for AVM
Planning MR
• MRI brain
• T1/T2/Flair
• 3DFSPGR contrast
• No gap
• No tilt
• Neutral neck
• 1mm slice
• 512 X 512 Matrix
Specific sequences
• 3D DSA
• MRA axial slice
66

67. Digital subtraction angiography (DSA)
• Digital subtraction angiography (DSA) is a type of fluoroscopy
technique used in interventional radiology to clearly visualize blood
vessels in a bony or dense soft tissue environment.
• Etymology
• ANGIO means blood vessel And angiography is the radiological study of blood
vessel in the body after the introduction of iodinated contrast media.
• SUBTRACTION means it is simply a technique by which bone structures
images are subtracted or canceled out from a film of bones plus opacified
vessels, leaving an unobscured image of the vessels.
67

68. The machine and procedure
• The non-contrast image (mask image) of the
region is taken before injecting contrast
material and therefore shows only anatomy, as
well as any radiopaque foreign bodies
(surgical clips, stents, etc.) As would a regular
x-ray image.
• Contrast images are taken in succession while
contrast material is being injected. These
images show the opacified vessels
superimposed on the anatomy and are stored
on the computer.
• The mask image is then subtracted from the
contrast images pixel by pixel.
• The resulting subtraction images show the
filled vessels only.
• Recording can continue to provide a sequence
of subtracted images based on the initial mask
68

69. The cranial AVM
69

70. AVM on DSA the gold standard
DSA left ICA -lateral view showing
an occipital AVM
70

71. 2D/3D/4D DSA
71

72. MR Angio
• Phase-contrast MR angiography
is often useful for subtracting
the hematoma components
when an AVM complicated by an
acute hemorrhage needs to be
imaged
• You can take axial view
• Thalamic AVM
72

73. Temporal AVM-CT and Angio
Nidus (blue arrows) and enlarged middle cerebral
arteries (orange arrows).
Irregular density in the left temporal lobe, slightly
hyperdense to adjacent white matter. NCCT
73

74. Left basal ganglia AVM- CT Angio
74

75. AVM in various MRI sequences
T1 T2 T2F T1C
MRA T1C
75

76. Planning MRI for vestibular schwannoma
Planning MR
• MRI brain
• T1/T2/Flair
• 3DFSPGR contrast
• No gap
• No tilt
• Neutral neck
• 1mm slice
• 512 X 512 Matrix
Specific sequences
• FIESTA/CISS sequence
• Cranial nerve
• Brain stem
• T2 for cochlea
76

77. Vestibular schwannoma imaging
CT
• May show erosion and widening of
the internal acoustic canal (IAC).
• The density of these tumours on non-contrast
imaging is variable, and often they are hard
to see, especially on account of beam
hardening and streak artifact from the
adjacent petrous temporal bone.
• Contrast enhancement is present but can be
underwhelming, especially in larger lesions
with cystic components.
• Many cysts are loculations of CSF adjacent to
a vestibular schwannoma, others represent
cystic degeneration within schwannomas
MR
• T1
• slightly hypointense to the adjacent brain
(63%) or isointense to it (37%)
• may contain hypointense cystic areas
• T2
• Heterogeneously hyperintense to adjacent
brain 5
• Fluid intensity cystic areas
• May have associated peritumoral arachnoid
cysts
• T1 C+ (Gd)
• Contrast enhancement is intense
• However, heterogeneous in larger tumours
77

78. Vestibular schwannoma
78

79. Planning MRI for pituitary adenoma
Planning MR
• MRI brain
• T1/T2/Flair
• 3DFSPGR contrast
• No gap
• No tilt
• Neutral neck
• 1mm slice
• 512 X 512 Matrix
Specific sequences
• FATSAT/STIR sequence
• Packing material
• FIESTA/CISS sequence
• Cranial nerve
• Brain stem
79

80. 80

81. 81

82. 82

83. Differentiating from packing material
83

84. Planning MRI for meningioma
Planning MR
• MRI brain
• T1/T2/Flair
• 3DFSPGR contrast
• No gap
• No tilt
• Neutral neck
• 1mm slice
• 512 X 512 Matrix
Specific sequences
• Delayed contrast
• FATSAT/STIR sequence
• Packing material
• FIESTA/CISS sequence
• Cranial nerve
• Brain stem
• DOTATOC-PET/CT/SOS
84

85. Fontal meningioma
85

86. DOTATOC-PET/CT
• Meningioma cells strongly express somatostatin receptor subtype 2
(SSTR 2) which offers an additional positron emission tomography
(PET) based imaging for tumor delineation with the somatostatin-
receptor ligand [68Ga]- DOTA-D Phe1-Tyr3-Octreotide (DOTATOC).
• DOTATOC-PET/CT shows a high meningioma to background ratio
which can be used to improve target volume definition .
• DOTATOC-PET/CT information may strongly complement patho-
anatomical data from MRI and CT in cases with complex meningioma
and is thus helpful for improved target volume delineation especially
for skull base manifestations and recurrent disease after surgery
86

87. Skull base meningioma
87

88. REIRRADIATION
PNR
• PSEUDOPROGRESSION
• NECROSIS
• RECURRENCE
88

89. Ammunition
• MRS
• PERFUSION SCAN
• PSMA SCAN
89

90. Perfusion based algorithm glioma vs metastasis vs necrosis
90

91. 91

92. 92

93. PSMA SCAN
Fahad Marafi/Clinical Nuclear Medicine / January 2020 93

94. Other rare
Glossopharyngeal schwannoma Jugular schwannoma
94

95. Other rare
Cavernomas Hypothalamic hamartomas
95

96. Response assessment
DISEASE SEQUENCE
 NORMAL ANATOMY 3D FSPGR
 PITUITARY ADENOMA STIR
 TRIGEMINAL NEURALGIA FIESTA
 CRANIAL NERVES CISS
 CP ANGLE TUMOR GRE
 GLIOMA DIFFUSION,PERFUSION
 AVM ANGIO
 GRADING OF TUMORS MRS
 METASTASIS DOUBLE/TRIPLE/DELAYED CONTRAST
DIFFUSION,PERFUSION 96

97. MRI spine and sequences
97

98. 98

99. 99

100. 100
Clock wise

101. 101

102. 102

103. 103

104. 104

105. Spine sequences
• T1
• T2
• STIR
• T1C
• DIXON
• DWI
• SWI
105

106. MRI sequences
Basic sequences
1. T1
2. T2
3. Inversion recovery (IR)
4. Post contrast T1
Advanced sequences
1. DWI (Functional sequence)
2. SWI
3. Multi-point Dixon
4. Dynamic Post contrast T1
Thanks to Dr C Seetharaman 106

107. 107

108. T1W
1. Morphology of bones and soft tissue
2. Most pathological lesions appear
hypo intense against
normal fatty marrow
Thanks to Dr C Seetharaman 108

109. T1C
1. Gives details about
cellularity and necrosis
2. Dynamic post contrast
will assess vascularity
of bone metastasis
(EGFR status)
3. Response assessment
Thanks to Dr C Seetharaman 109

110. T2W
1. Adds information about morphology of
bones and soft tissue.
2. Most pathological lesions appear
hyper intenseagainst
normal marrow
Thanks to Dr C Seetharaman 110

111. IR sequence
1. Fat suppressed T2W sequence
2. More clear
3. Differentiate from T2 by back FAT[arrow]
1. Bright on T2
2. Darker on IR
4. Most pathological lesions appear
more hyper intenseagainst normal
marrow
Thanks to Dr C Seetharaman 111
T2 SEQUENCE IR SEQUENCE

112. 112

113. Susceptibility-weighted MRI spine
113
Susceptibility-weighted MRI enables the reliable differentiation between predominantly osteoblastic and
osteolytic spine metastases with a higher accuracy than standard MRI sequences

114. 114

115. Summary
• CT and MR should be same slice thickness
• Flat couch
• Discuss with radiologist
• Fuse properly
• Delineate with radiologist
• Get the result
115

116. Special thanks
116

117. Thanks to ICRO
117

118. 118