L 12

1
L 12

• SPECT/CT
• TECHNOLOGY FACILITY DESIGN

2
Answer True or False

• The most common isotope used in SPECT/CT scans is
  18F
• SPECT scanners work by detecting coincidences of
  two 511 keV gamma rays
• The facility design concepts are almost identical
  to those used in designing PET/CT facilities

3
Objective
To become familiar with basic SPECT/CT
technology, and review considerations in
establishing a new SPECT/CT facility
4
Content

• SPECT cameras
• Image Quality Camera QA
• SPECT/CT scanners
• Design of SPECT/CT facilities

5
12.1 SPECT cameras
6
Scintillators

Density
Z

Decay
Light
Atten
.

(g/cc)

time
yield

length
(ns)

( NaI)

(mm)

Na(Tl)
I

3.67

51

230

100

30

BGO

7.13

75

300

15

11

LSO

7.4

66

47

75

12

GSO

6.7

59

43

22

15

• Na(Tl) I works well at 140 keV, and is the most
  common scintillator used in SPECT cameras

7
Scintillation detector
Amplifier
PHA
Scaler
8
Pulse height analyzer
Pulse height (V)
UL LL
Time
The pulse height analyzer allows only pulses of a
certain height (energy) to be counted.
counted
not counted
9
Pulse-height distributionNaI(Tl)
10
Semi-conductor detector as spectrometer

• Solid Germanium or Ge(Li) detectors
• Principle electron - hole pairs (analogous to
  ion-pairs in gas-filled detectors)
• Excellent energy resolution

11
Comparison of spectrum from a Na(I)
scintillation detector and a Ge(Li)
semi-conductor detector
Knoll
12
Gamma camera
Used to measure the spatial and temporal
distribution of a radiopharmaceutical
13
Gamma camera(principle of operation)
Position X Position Y Energy Z
PM-tubes Detector Collimator
14
GAMMA CAMERA
15
PM-tubes
16
Gamma camera collimators
17
Gamma cameraData acquisition

• Static
• Dynamic
• ECG-gated
• Wholebody scanning
• Tomography
• ECG-gated tomography
• Wholebody tomography

18
ECG-gated acquisition
R
Interval n
Image n
19
Scintigraphy seeks to determine the distribution
ofa radiopharmaceutical
20
SPECT cameras are used to determine the
three-dimensional distribution of the radiotracer
21
Tomographic acquisition
22
Tomographic reconstruction
23
Tomographic planes
24
Myocardial scintigraphy
25
ECG GATED TOMOGRAPHY
26
12.2 Image Quality Camera QA
27
Factors affecting image formation

• Distribution of radiopharmaceutical
• Collimator selection and sensitivity
• Spatial resolution
• Energy resolution
• Uniformity
• Count rate performance
• Spatial positioning at different energies
• Center of rotation
• Scattered radiation
• Attenuation
• Noise

28
SPATIAL RESOLUTION
Sum of intrinsic resolution and the collimator
resolution Intrinsic resolution depends on the
positioning of the scintillation events
(detector thickness, number of PM-tubes, photon
energy) Collimator resolution depends on the
collimator geometry (size, shape and length of
the holes)
29
SPATIAL RESOLUTION
Object
Image
Intensity
30
Resolution - distance
High sensitivity
High resolution
FWHM
31
SPATIAL RESOLUTION - DISTANCE
Optimal Large distance
32
Linearity
33
NON UNIFORMITY
34
NON UNIFORMITY
Cracked crystal
35
NON-UNIFORMITY
(Contamination of collimator)
36
NON UNIFORMITYRING ARTIFACTS
Good uniformity Bad
uniformity
Difference
37
NON-UNIFORMITY
Defect collimator
38
COUNT RATE PERFORMANCE
(IAEA QC Atlas)
39
Spatial positioning at different energies
Intrinsic spatial resolution with Ga-67 Point
source (count rate lt 20k cps) quadrant bar
pattern 3M counts preset energy window widths
summed image from energy windows set over the 93
keV, 183 keV and 296 keV photopeaks. (IAEA QC
Atlas)
40
Spatial positioning at different energies
41
Center of Rotation
42
Tilted detector
43
Scattered radiation
Scattered photon
photon
electron
44
The amount of scattered photons registered
Patient size Energy resolution of the
gammacamera Window setting
45
PATIENT SIZE
46
Pulse height distribution
Full energy peak
Scattered photons
The width of the full energypeak (FWHM) is
determined by the energy resolution of thegamma
camera. There willbe an overlap between
thescattered photon distributionand the full
energy peak,meaning that some scatteredphotons
will be registered.
FWHM
Overlappingarea
47
Window width
20
10
40
Increased window width will result in an
increased number ofregistered scattered photons
and hence a decrease in contrast
48
SCATTER CORRECTION
49
ATTENUATION
Register 1000 counts Origin of
counts
II0 exp(-µx)
50
ATTENUATION
Contrast (2cm object)
23 7
2
51
ATTENUATION CORRECTION
52
ATTENUATION CORRECTION

• Transmission measurements
• Sealed source
• CT

53
ATTENUATION CORRECTION
Ficaro et al Circulation 93463-473, 1996
54
NOISE
Count density
55
Gamma camera

• Operational considerations
• Collimator selection
• Collimator mounting
• Distance collimator-patient
• Uniformity
• Energy window setting
• Corrections (attenuation, scatter)
• Background
• Recording system
• Type of examination

56
QC GAMMA CAMERA
Acceptance Daily Weekly
Yearly Uniformity P T T P Uniformity,
tomography P P Spectrum display P T T P Energy
resolution P P Sensitivity P T P Pixel
size P T P Center of rotation P T P Linearity
P P Resolution P P Count
losses P P Multiple window pos P P Total
performance phantom P P P physicist,
Ttechnician
57
IAEA-TECDOC-602
IAEA-TRS-454 Quality Assurance for Radioactivity
Measurement in Nuclear Medicine 2006
IAEA QA for SPECT systems (in press)
Quality control of Nuclear medicine instruments
1991
INTERNATIONAL ATOMIC ENERGY AGENCY IAEA
May 1991
58
QC Gamma camera
59
Energy resolution
60
Linearity
Flood source or point source (Tc-99m) Bar phantom
or orthogonal-hole phantom
1. Subjective evaluation of the image. 2.
Calculate absolute (AL) and differential
(DL) linearity. AL Maximum displacement from
ideal grid (mm) DL Standard deviation of
displacements (mm)
61
UNIFORMITY
Flood source (Tc-99m, Co-57) Point source (Tc-99m)
Intrinsic uniformity Point source at a large
distance from the detector. Acquire an image of
10.000.000 counts With collimator Flood source
on the collimator. Acquire an image of 10.000.000
counts
62
Uniformity
1. Subjective evaluation of the image 2.
Calculate Integral uniformity (IU) Differential
uniformity (DU)
IU(Max-Min)/MaxMin)100, where Max is the the
maximum and Min is the minimum counts in a
pixel DU(Hi-Low)/(HiLow)100, where Hi is the
highest and Low is the lowest pixel value in a
row of 5 pixels moving over the field of
view Matrix size 64x64 or 128x128
63
UNIFORMITY/DIFFERENT RADIONUCLIDES
Tc 99m
Tl 201
I 131
Ga 67
All 4 images acquired with Matrix 256 x 256,
counts 30 Mcounts
D BOULFELFEL Dubai Hospital
64
LINEARITY AND UNIFORMITY CORRECTIONS
Dogan Bor, Ankara
65
OFF PEAK MEASUREMENTS
Dogan Bor, Ankara
66
TOMOGRAPHIC UNIFORMITY
Tomographic uniformity is the uniformity of the
reconstruction of a slicethrough a uniform
distribution of activity SPECT phantom with
200-400 MBq Tc99m aligned with the axis
of rotation. Acquire 250k counts per angle.
Reconstruct the data with a ramp filter
67
INCORRECT MEASUREMENT
Two images of a flood source filled with a
solution of Tc-99m, which had not been mixed
properly
68
Spatial resolution
Measured with Flood source or point source
plus a Bar phantom
Subjective evaluation of the image
69
SPATIAL RESOLUTION
Intrinsic resolution
System resolution
Screw clip
Polyethylene tubingabout 0.5 mm in
internaldiameter
Rigid plastic
30 mm
50 mm
500 mm
60 mm
5 mm
200 mm
Lead
Plastic shims
IAEA TECDOC 602
70
SPATIAL RESOLUTION
Tc-99m or other radionuclide in use Intrinsic
Collimated line source on the detector System
Line source at a certain distance Calculate FWHM
of the line spread function
FWHM 7.9 mm
71
TOMOGRAPHIC RESOLUTION
Method 1 Measurement with the Jaszczak phantom,
with and without scatter (phantom filled with
water and with no liquid) Method 2
Measurement with a Point or line source free in
air and Point or line source in a SPECT phantom
with water
72
Sensitivity

• Expressed as counts/min/MBq and should be
  measured for each collimator
• Important to observe with multi-head systems that
  variations among heads do not exceed 3

73
SENSITIVITY
74
Multiple Window Spatial Registration

• Performed to verify that contrast is satisfactory
  for imaging radionuclides, which emit photons of
  more than one energy (e.g. Tl-201, Ga-67, In-111,
  etc.) as well as in dual radionuclides studies

75
Multiple Window Spatial Registration

• Collimated Ga-67 sources are used at central
  point, four points on the X-axis and four points
  on the Y axis
• Perform acquisitions for the 93, 184 and 300 keV
  energy windows
• Displacement of count centroids from each peak is
  computed and maximum is retained as MWSR in mm

76
Count Rate Performance

• Performed to ensure that the time to process an
  event is sufficient to maintain spatial
  resolution and uniformity in clinical images
  acquired at high-count rates

77
Count Rate Performance

• Use of decaying source or calibrated copper
  sheets to compute the observed count rate for a
  20 count loss and the maximum count rate without
  scatter

78
Pixel size
79
Center of rotation
Point source of Tc-99m or Co-57 Make a
tomographic acquisition In x-direction the
position will describe a sinus- function. In
y-direction a straight line. Calculate the
offset from a fitted cosine and linearfunction
at each angle.
Linear function
Cosine function
80
Total performance
Total performance phantom. Emission or
transmission. Compare result with reference image.
81
SOURCES FORQC OF GAMMA CAMERAS

• Point source
• Collimated line source
• Line source
• Flood source

lt1 mm
Tc99m, Co57, Ga67
82
Phantoms for QC ofgamma cameras

• Bar phantom
• Slit phantom
• Orthogonal hole phantom
• Total performance phantom

83
Phantoms for QC ofgamma cameras
84
QUALITY CONTROLANALOGUE IMAGES
Quality control of film processing base fog,
sensitivity, contrast
85
QUALITY ASSURANCECOMPUTER EVALUATION
Efficient use of computers can increase the
sensitivity and specificity of an examination.
software based on published and clinically
tested methods well documented algorithms
user manuals training software phantoms
86
Semi-conductor detectorApplications in nuclear
medicine

• Identification of nuclides
• Control of radionuclide purity

87
12.3. SPECT/CT
88
TYPICAL SPECT/CT CONFIGURATION
The most prevalent form of SPECT/CT scanner
involves a dual-detector SPECT camera with a
1-slice or 4-slice CT unit mounted to the
rotating gantry 64-slice CT for SPECT/CT also
available
89
SPECT/CT

• Accurate registration
• CT data used for attenuation correction
• Localization of abnormalities
• Parathyroid lesions (especially for ectopic
  lesions)
• Bone vs soft tissue infections
• CTCA fused with myocardial perfusion for 64-slice
  CT scanners

90
The CT Scanner

• Computed Tomography (CT) was introduced into
  clinical practice in 1972 and revolutionized X
  Ray imaging by providing high quality images
  which reproduced transverse cross sections of the
  body.
• Tissues are therefore not superimposed on the
  image as they are in conventional projections
• The technique offered in particular improved low
  contrast resolution for better visualization of
  soft tissue, but with relatively high absorbed
  radiation dose

91
The CT Scanner
X ray tube
X ray emission in all directions
collimators
92
A look inside a rotate/rotate CT
Detector Array and Collimator
X Ray Tube
93
A Look Inside a Slip Ring CT
Note how most of the electronics is placed
on the rotating gantry
X Ray Tube Detector Array Slip Ring
94
What are we measuring in a CT scanner?

• We are measuring the average linear attenuation
  coefficient µ between tube and detectors
• The attenuation coefficient reflects how the x
  ray intensity is reduced by a material

95
Conversion of ? to CT number

• Distribution of ? values initially measured
• ? values are scaled to that of water to give the
  CT number

96
12.5 Design of SPECT/CT facilities
97
Nuclear medicine applicationaccording to type of
radionuclide
Radionuclide
Diagnostics
Therapy

• Pure ? emitter ? (?)
• e.g. Tc99m, In111, Ga67, I123
• Positron emitters (ß) ? ?
• e.g. F-18
• ?, ß- emitters ? ?
• e.g. I131, Sm153
• Pure ß- emitters ? ?
• e.g. Sr89, Y90, Er169
• ? emitters ? ?
• e.g. At211, Bi213

98
Sealed sources in nuclear medicine
Sealed sources used for calibration and quality
control of equipment (Na-22, Mn-54, Co57, Co-60,
Cs137, Cd-109, I-129, Ba-133, Am-241). Point
sources and anatomical markers (Co-57, Au-195).
The activities are in the range 1 kBq-1GBq.
99
99Mo-99mTc GENERATOR
87.6
99mTc
99Mo
? 140 keV T½ 6.02 h
12.4
ß- 442 keV ? 739 keV T½ 2.75 d
99Tc
ß- 292 keV T½ 2105 y
99Ru stable
100
Technetium generator
Mo-99 Tc-99m Tc-99
66 h 6h
NaCl AlO2 Mo-99 Tc-99m Tc-99m
101
Technetium generator
102
Technetium generator
103
Technetium generator
104
Technetium generator
105
Technetium generator
106
Radiopharmaceuticals
Radionuclide Pharmaceutical Organ
Parameter

colloid Liver
RES Tc-99m
MAA Lungs
Regional

perfusion DTPA
Kidneys Kidney

function
107
RADIOPHARMACEUTICALS

• Radiopharmaceuticals used in nuclear medicine can
  be classified as follows
• ready-to-use radiopharmaceuticals
• e.g. 131I- MIBG, 131I-iodide, 201Tl-chloride,
  111In- DTPA
• instant kits for preparation of products
• e.g. 99mTc-MDP, 99mTc-MAA, 99mTc-HIDA,
  111In-Octreotide
• kits requiring heating
• e.g. 99mTc-MAG3, 99mTc-MIBI
• products requiring significant manipulation
• e.g. labelling of blood cells, synthesis and
  labelling of radiopharmaceuticals produced in
  house

108
Laboratory work with radionuclides
109
Administration of radiopharmaceuticals
110
Categorization of hazard
Based on calculation of a weighted activity using
weighting factors according to radionuclide used
and the type of operation performed. Weighted
activity Category lt 50 MBq Low hazard 50-50000
MBq Medium hazard gt50000 MBq High hazard
111
Categorization of hazardWeighting factors
according to radionuclide
Class Radionuclide Weighting factor A 75Se,
89Sr, 125I, 131I 100 B 11C, 13N, 15O,
18F, 51Cr, 67Ga, 99mTc, 111In, 113mIn, 123I,
201Tl 1.00 C 3H, 14C, 81mKr 127Xe,
133Xe 0.01
112
Categorization of hazardWeighting factors
according to type of operation
Type of operation or area Weighting
factor Storage 0.01 Waste handling, imaging
room (no inj), waiting area, patient bed area
(diagnostic) 0.10 Local dispensing, radionuclide
administration, imaging room (inj.), simple
preparation, patient bed area (therapy) 1.00 Co
mplex preparation 10.0
113
Categorization of hazard
Administration of 11 GBq I-131 Weighting factor,
radionuclide 100 Weighting factor, operation
1 Total weighted activity 1100
GBq Weighted activity Category lt 50 MBq Low
hazard 50-50000 MBq Medium hazard gt50000
MBq High hazard
114
Categorization of hazard
Patient examination, 400 MBq Tc-99m Weighting
factor, radionuclide 1 Weighting factor,
operation 1 Total weighted activity
400 MBq Weighted activity Category lt 50
MBq Low hazard 50-50000 MBq Medium
hazard gt50000 MBq High hazard
115
Categorization of hazard
Patients waiting, 8 patients, 400 MBq Tc-99m per
patient Weighting factor, radionuclide 1 Weighti
ng factor, operation 0.1 Total weighted
activity 320 MBq Weighted
activity Category lt 50 MBq Low
hazard 50-50000 MBq Medium hazard gt50000
MBq High hazard
116
Category of hazard(premises not frequented by
patients)Typical results of hazard calculations
High hazard Room for preparation and dispensing
radiopharmaceuticals Temporary storage of
waste Medium hazard Room for storage of
radionuclides Low hazard Room for measuring
samples Radiochemical work (RIA) Offices
117
Category of hazard(premises frequented by
patients) Typical results of hazard calculations
High hazard Room for administration of
radiopharmaceuticals Examination room Isolation
ward Medium hazard Waiting room Patient
toilet Low hazard Reception
118
Building requirements
Category Structural shielding Floors
Worktop surfaces of hazard walls,
ceiling Low
no cleanable
cleanable Medium no
continuous cleanable

sheet High
possibly continuous
cleanable
one sheet

folded to
walls
What the room is used for should be taken into
account e.g. waiting room
119
Building requirements
Category Fume hood Ventilation
Plumbing First aid of hazard Low
no
normal standard
washing Medium yes
good standard
washing decontamination


facilities

High yes
may need may need washing

special forced special
decontamination
ventilation
plumbing facilities
facilities
facilities
120
Design Objectives

• Safety of sources

• Optimize exposure of staff, patients and general
  public

• Prevent uncontrolled spread of contamination

• Maintain low background where most needed

• Fulfil requirements regarding pharmaceutical work

121
VENTILATION
Laboratories in which unsealed sources,
especially radioactive aerosols or gases, may be
produced or handled should have an appropriate
ventilation system that includes a fume hood,
laminar air flow cabinet or glove box The
ventilation system should be designed such that
the laboratory is at negative pressure relative
to surrounding areas. The airflow should be from
areas of minimal likelihood of airborne
contamination to areas where such contamination
is likely All air from the laboratory should
be vented through a fume hood and must not be
recirculated either directly, in combination with
incoming fresh air in a mixing system, or
indirectly, as a result of proximity of the
exhaust to a fresh air intake
122
VENTILATION
Sterile room negative pressure filtered air
Injection room
Laminar air flow cabinets
Work bench
Passage
Dispensation negative pressure
Fume hood
Corridor
123
Continous monitoring av air pressure gradients
Alarm system
124
Fume hood
The fume hood must be constructed of smooth,
impervious, washable and chemical-resistant
material. The working surface should have a
slightly raised lip to contain any spills and
must be strong enough to bear the weight of any
lead shielding that may be required The
air-handling capacity of the fume hood should be
such that the linear face velocity is between 0.5
and 1.0 metres/second with the sash in the
normal working position. This should be checked
regularly
125
Sinks
If the Regulatory Authority allows the release of
aqueous waste to the sewer a special sink shall
be used. Local rules for the discharge shall be
available. The sink shall be easy to
decontaminate. Special flushing units are
available for diluting the waste and minimizing
contamination of the sink.
126
Washing facilities
The wash-up sink should be located in a
low-traffic area adjacent to the work area Taps
should be operable without direct hand contact
and disposable towels or hot air dryer should be
available An emergency eye-wash should be
installed near the hand-washing sink and there
should be access to an emergency shower in or
near the laboratory
127
Shielding
Much cheaper and more convenient to shield the
source, where possible, rather than the room or
the person Structural shielding is generally not
necessary in a nuclear medicine department.
However, the need for wall shielding should be
assessed e.g. in the design of a therapy ward (to
protect other patients and staff) and in the
design of a laboratory housing sensitive
instruments (to keep a low background in a well
counter, gamma camera, etc)
128
Layout of a nuclear medicine department
From high to low activity
129
SUMMARY OF SPET/CT

• SPECT cameras are scintillation cameras, also
  called gamma cameras, which image one gamma ray
  at a time, with optimum detection at 140 KeV,
  ideal for gamma rays emitted by Tc-99m
• SPECT cameras rotate about the patient in order
  to determine the three-dimensional distribution
  of radiotracer in the patient
• SPECT/CT scanners have a CT scanner immediately
  adjacent to the SPECT camera, enabling accurate
  registration of the SPECT scan with the CT scan,
  enabling attenuation correction of the SPECT
  scan by the CT scan and anatomical localization
  of areas of unusually high activity revealed by
  the SPECT scan