This document discusses various equipment used in nuclear medicine and their quality control, including: - Ionization chambers such as dose calibrators which measure radiation exposure rates. - Gamma cameras which detect gamma rays and form images using collimators, scintillation crystals, photomultiplier tubes, and computers. - SPECT which provides 3D tomographic images using gamma cameras to acquire multiple 2D images from different angles. It also covers quality control procedures for dose calibrators and gamma cameras including geometry, accuracy, linearity, and constancy tests to ensure proper functioning and accurate measurements.

1. equipment AND QUALITY CONTROL
BY MUMBA CHILIMBOYI

2. EQUIPMENT USED IN NUCLEAR MEDICINE
AND QUALITY CONTROL
IONIZATION CHAMBER
DOSE CALIBRATOR
GAMMA SCINTILLATION CAMERA
COMPUTERS
SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT)
RADIATION MONITOR GEIGER-MUELLER COUNTER
DETECTORS

3. IONIZATION CHAMBER
• Ionization chambers are handheld survey instruments used to measure low or
high exposure rates.
• They have an air or gas-filled chamber but a low efficiency for detection of
gamma rays.
• These instruments have a relatively low applied voltage from anode to cathode;
as a result, there is no avalanche effect and no dead time problem.
• Ionization chambers typically are useful at exposure rates ranging from 0.1 mR
(2.5 x 10-8 C/kg)/hour to 100 R (2.5 x 10-2 C/kg)/hour.
• A dose calibrator is a special form of an ionization chamber.

4. DOSE CALIBRATOR AND GAMMA CAMERA
• DEFINITION
• COMPONENTS
• PRINCIPLES OF OPERATION
• QUALITY CONTROL

5. DOSE CALIBRATOR
• The dose calibrator is an ionization chamber used to assay the
amount of activity in vials and syringes
• This includes the assay of individual doses before
administration to patients, as required by regulation.
• The dose calibrator operates over a very wide range of
activities, from hundreds of kilobecquerels (10s of μCi) to tens
of gigabecquerels (up to a curie).
• Displayed units are mCI millicurie or Megabecquerel

6. DOSE CALIBRATOR COMPONENTS1
3
2

7. OPERATION OF DOSE CALIBRATOR
• The chamber is cylindrical and holds a
defined volume of pressurized inert gas
(usually argon).
• Within the chamber is a collecting
electrode. As radiation emanates from the
radiopharmaceutical in the syringe, it enters
the chamber and interacts with the gas,
causing ionization.
• If no voltage is applied to the electrodes, the
ion pairs recombine.
• If an electrical differential applied between
the chamber and the collecting electrode is
applied it causes the ions to be captured and
measured. This measurement is used to
calculate the dose contained in the syringe.

8. QUALITY CONTROL FOR DOSE CALIBRATORS
• The dose calibrator is used to assay the activity administered
to the patient, and thus a comprehensive quality control
program is necessary.
• This program comprises four basic quality control tests:
-Geometry
-Accuracy
-Linearity
-Constancy

9. THE GEOMETRY PROTOCOL TESTS
• This test of the dose calibrator provides the same reading for the same
amount of activity irrespective of the volume or orientation of the
sample.
• A reading of a certain amount of activity in a 0.5-mL volume is
obtained. The volume is then increased by augmenting the sample with
amounts of nonradioactive water or saline and taking additional
readings. The subsequent readings should not vary from the original
readings by more than 10%.
• The geometry test is performed during acceptance testing and after a
major repair or movement of the equipment to another location.

10. ACCURACY
• For accuracy, calibrated sources (typically cobalt-57
and 137Cs) are analysed.
• The resultant reading cannot vary by more than 10%
from the calibrated activity decay corrected to the day
of the test.
• The accuracy test should be performed during
acceptance testing, annually thereafter, and after a
major repair or move.

11. LINEARITY PROTOCOL TESTS
•This test of the dose calibrator operates appropriately over
the wide activity range to which it is applied. The device
is tested from 10 μCi (370 kBq) to a level higher than that
routinely used in the clinic and perhaps as high as 1 Ci
(37 GBq).
•The activity readings are varied by starting with a sample
of radioactivity of Tc-99m at the highest value to be tested
(e.g., tens of gigabequerels).

12. LINEARITY PROTOCOL TESTS Cont.…
• The activity readings are then varied by either allowing the
source to radioactively decay over several days or using a set
of lead shields of varying thicknesses until a reading close to
370 kBq is obtained. Each reading should not vary by more
than 10% from the line drawn through the calculated activity
values.
• The linearity test should be performed during acceptance
testing, quarterly thereafter, and after a major repair or move.

13. THE CONSTANCY PROTOCOL TESTS
• This tests is the reproducibility of the readings as compared to
a decay-corrected estimate for a reference reading obtained
from the dose calibrator on a particular day.
• Today’s constancy reading cannot vary from the decay-
corrected reference reading by more than 10%.
• The constancy test varies from accuracy in that it evaluates the
precision of the readings from day to day rather than accuracy.
• The constancy test should be performed on every day that the
device is used to assay a dose to be administered to a patient.

14. DOSE CALIBRATOR RADIATION PROTECTION
• Lead shielding around the ionization chamber
1. Protects the operator
2. Reduces the response background radiation
• Sample holder can be cleaned in the event of
radioactive contamination of the chamber well

15. GAMMA CAMERA
The most widely used cameras in nuclear medicine are:
1. Simple gamma scintillation (Anger) camera
2. Single-photon emission computed tomography (SPECT) capable
gamma camera.
FUNCTION OF GAMMA CAMERA
• A gamma camera converts photons emitted by the radionuclide in the
patient into a light pulse and subsequently into a voltage signal.

16. GAMMA CAMERA SYSTEM
COMPONENTS
• The collimator
• The scintillation crystal
• An array of photomultiplier tubes (PMTs)
• Preamplifiers
• A pulse height analyzer (PHA)
• Digital correction circuitry,
• A cathode ray tube (CRT)
• The control console.
• A computer and
• Picture archiving systems(PACs)

17. GAMMA CAMERAASSEMBLY

18. COLLIMATORS
• The collimator is made of perforated or folded lead and is
interposed between the patient and the scintillation crystal. It
allows the gamma camera to localize accurately the
radionuclide in the patient’s body.
• Collimators perform this function by absorbing and stopping
most radiation except that arriving almost perpendicular to the
detector face.
• Most radiation striking the collimator at oblique angles is not
included in the final image.

19. TYPES COLLIMATORS
As the energy of the radionuclide increases, the
best collimator usually has thicker and longer
septa. For a given septal thickness, spatial
resolution of a collimator increases with septal
length but sensitivity decreases.
The two basic types of collimators are pinhole and multihole

20. SEPTAL PENETRATION AND PHOTON SCATTERING
EFFECT OF SEPTAL LENGTH ON COLLIMATOR SENSITIVITY
AND RESOLUTION
EFFECT OF DIFFERENT SOURCE-TO-CAMERA DISTANCES

21. CRYSTAL AND OTHER PHOTON DETECTOR DEVICES
• Radiation emerging from the patient and passing through the
collimator interacts with a thallium activated sodium iodide
crystal.
• Crystals are made with thallium or sodium activated cesium
iodide or even lanthanum bromide are used. They convert
Gamma rays to light.
• PMTs situated along the posterior crystal face detect this light
and amplify it to an electrical pulse.

22. PHOTONMULTIPLIER TUBEs (PMTs)
• A photomultiplier tube (PMT) converts a light pulse into an electrical
signal of measurable magnitude.
• Localization of the event in the final image depends on the amount of
light sensed by each PMT and thus on the pattern of PMT voltage
output.
• VOLTAGE AMPLIFIER / VOLTAGE SUPPLY
 A High voltage supply for the PMT
 An amplifier increases the size of the pulse.

23. PULSE HEIGHT ANALYZER
• The basic principle of the PHA is to discard signals from background
and scattered radiation and/or radiation from interfering isotopes so
that only primary photons known to come from the photopeak of the
isotope being imaged are recorded
• The PHA discriminates between events occurring in the crystal that
will be displayed or stored in the computer and events that will be
rejected.

24. CONSOLE CONTROLS
• Image exposure time is selected by console control
• Its usually a preset count, a preset time, or preset information
density for the image accumulation.
Other console controls are present for orientation and allow
the image to be reversed on the x- and y-axes.
In addition, the CRT image may be manipulated by an
intensity control
Hard copy images on film may be obtained directly from the
computer, display digital images on monitors and store the
images in a picture archiving system.

25. OPERATION OF GAMMA SYSTEM
 Gamma rays emitted from within the patient pass
through the holes of an absorptive collimator to
reach the NaI crystal.
 On interaction of the gamma ray with the NaI
scintillating crystal, thousands of light photons are
emitted, a portion of which are collected by an
array of PMTs. By taking weighted sums of the
PMT signals within the associated computer
 The two-dimensional (2D) x and y location and
the total energy of the detection event deposited is
estimated. If the energy deposited is within a
prespecified energy window (e.g., within 10% of
the photopeak energy), the event is accepted and
the location of the event recorded.
 In this manner, the gamma camera image is
constructed on an event-by-event basis, and a
single nuclear medicine image may consist of
hundreds of thousands of such events.

26. GAMMA CAMERA QUALITY CONTROL
•This involves acceptance testing of the device before its
initial use and a program of routine tests and evaluations
applied on a regular basis.
•It is essential that the performance be evaluated regularly to
ensure that the images adequately demonstrate the in vivo
distribution of the administered radiopharmaceutical and
that any quantitation performed with the camera yields
values that are accurate and precise

27. GAMMA CAMERA QUALITY CONTROL SUMMARY
PARAMETER COMMENT
DAILY
• UNIFORMITY
• WINDOW SETTING
• FLOOD FIELD; INTRINSIC (WITHOUT COLLIMATOR) OR EXTRINSIC (WITH COLLIMATOR)
• CONFIRM ENERGY WINDOW SETTING RELATIVE TO PHOTOPEAK FOR EACH
RADIONUCLIDE USED WITH EACH PATIENT
WEEKLY OR MONTHLY
• SPATIAL RESOLUTION
• LINEARITY CHECK
• REQUIRES A “RESOLUTION” PHANTOM SUCH AS THE FOUR-QUADRANT BAR
• QUALITATIVE ASSESSMENT OF BAR PATTERN LINEARITY
The purpose of quality control is to detect changes in the performance of a gamma camera and below summary:

28. GAMMA CAMERA QUALITY CONTROL SUMMARY Cont....
PARAMETER COMMENT
ANNUALLY
• SYSTEM UNIFORMITY
• MULTI-WINDOW REGISTRATION
• COUNT RATE PERFORMANCE
• ENERGY RESOLUTION
• SYSTEM SENSITIVITY
• HIGH COUNT FLOOD WITH EACH COLLIMATOR
• FOR CAMERAS WITH CAPABILITY OF IMAGING MULTIPLE ENERGY
WINDOWS SIMULTANEOUSLY
• VARY COUNTS USING DECAY OR ABSORBER METHOD
• EASIEST IN CAMERAS WITH BUILT IN MULTICHANNEL ANALYZERS
• COUNT RATE PERFORMANCE PER UNIT OF ACTIVITY FOR EACH
COLLIMATOR

29. EFFECT OF INCREASING THE PATIENT-TO-DETECTOR FACE DISTANCE
ON CLINICAL IMAGES

30. SINGLE PHOTON EMISSION COMPUTED
TOMOGRAPHY (SPECT)
•SPECT is a nuclear medicine tomographic
imaging technique that uses gamma rays.
•It is very similar to conventional nuclear
medicine planar imaging using a gamma camera.
•It is able to provide true 3D information..

31. SPECT

32. SPECT CONT.…
•SPECT imaging is performed by using a gamma
camera to acquire multiple 2-D images from multiple
angles.
• A computer is then used to apply a tomographic
reconstruction algorithm to the multiple projections,
yielding a 3-D dataset.
•The dataset may then be manipulated to show thin
slices along any chosen axis of the body.

33. IMAGE RECONSTRUCTION
• SPECT acquire raw data in the form of projection data at a
variety of angles about the patient.
• Image reconstruction involves the processing of these data to
generate a series of cross-sectional images through the object
of interest.

34. PROJECTION DATA

35. APPLICATION OF SPECT
• Cerebral Blood flow imaging
• Myocardial perfusion imaging with thalium-201 or technetium-99
perfusion agents
• Imaging of tumors or infections with agents such as gallium-67 or 111
WBCs
• Certain Cases of Bone Imaging
• Brain studies
• Liver/ Spleen Imaging
• Renal Imaging

36. FOURIER TRANSFORM
• Image data may be best represented in either spatial (real) or frequency
space.
• The mathematician Joseph Fourier noted in 1807 that any arbitrary
signal can be generated by adding a large number of sine and cosine
signals of varying frequencies and amplitudes.
• The plot of amplitude as a function of frequency is referred to as the
Fourier transform, and it defines the components of the image at each
frequency.
• The low frequencies provide the overall shape of the object, whereas the
high frequencies help define the sharp edges and fine detail within the
image.

37. APPLICATIONS OF FOURIER TRANSFORM
• The Fourier method is often used on images from astronomy,
microbiology, images of repetitive structures such as crystals and so on.
• Fourier transform is good for identifying a periodic component or lattice
in an image.
• Identifying regular patterns on an image has other advantages like
removing regular dirty spots or noise from an image
• Components of higher frequency can be removed to achieve anti-aliasing
effect, i.e. removing ugly zaggy edges.

38. APPLICATIONS OF FOURIER TRANSFORM Cont.…..
• There are other techniques associated with Fourier
transform:
convolution theory
correlation, sampling
Reconstruction
image compression, and more.

39. RADIATION MONITOR-GEIGER-MUELLER
COUNTER
• Geiger-Mueller (GM) counters are handheld,
very sensitive, inexpensive survey instruments
used primarily to detect small amounts of
radioactive contamination.
• The detector is usually pancake shaped, it may
also be cylindrical.
• The detector is gas-filled and has a high applied
voltage from the anode to the cathode. This
causes one ionization to result in an “avalanche”
of other electrons, allowing high efficiency for
detection of even a single gamma ray.

40. TYPES OF RADIATION DETECTORS
Basically three types of radiation detectors are
used in nuclear medicine
Gas detectors
Scintillators
Semiconductors

41. GAS DETECTORS
• A gas radiation detector is filled with a volume of gas that acts as the sensitive
material of the detector.
• In some cases, it is air and in others it is an inert gas such as argon or xenon,
depending on the particular detector.
• Electrodes are located at either end of the sensitive volume.
• The detector circuit also contains a variable voltage supply and a current detector.
• As radiation passes through the sensitive volume, it causes ionization in the gas.
• If a voltage is applied across the volume, the resulting ions (electrons and positive
ions) will start to drift, causing a measureable current in the circuit. The current will
last until all of the charge that was liberated in the event is collected at the
electrodes.
• The resulting current entity is referred to as a pulse and is associated with a
particular detection event.

42. SCINTILLATION AND SEMICONDUCTOR DETECTORS
• Some crystalline materials emit a large number of light
photons upon the absorption of ionizing radiation.This
process is referred to as scintillation, and materials are
referred to as scintillators.
• As radiation interacts within the scintillator, a large number
of excitations and ionizations occur. On deexcitation, the
number of light photons emitted is directly proportional to the
amount of energy deposited within the scintillator.

43. SCINTILLATION AND SEMICONDUCTOR DETECTORS Cont.…
• Thermal energy can lead to a measureable current in some
semiconductor detectors such as GeLi, even in the absence of
radiation, and thus these semiconductor detectors must be operated at
cryogenic temperatures.
• On the other hand, semiconductor detectors such as cadmium telluride
(CdTe) or cadmium zinc telluride (CZT) can operate at room
temperature. CdTe and CZT do not have the excellent energy
resolution of GeLi, but at approximately 5%, it is still significantly
better than that of sodium iodide.

44. CONCLUSION
• Radiation detection and counting is the corner stone of nuclear
medicine.
• Detectors of all types—gas detectors, scintillators, and
semiconductors—are used every day in the nuclear medicine clinic.
• Some are used for ancillary purposes that support the clinic, such as
those used in the context of radiation protection.
• Others are used to specifically acquire biological data for a particular
clinical purpose. Most notably, the gamma camera is used to obtain
images of the in vivo distribution of the administered
radiopharmaceutical from which the patient’s physiology or function
can be inferred to further define the patient’s medical picture.

45. Conclusion Cont….
• A rigorous quality control program must be maintained for all equipment
used in the nuclear medicine clinic to ensure the integrity of the data
obtained from the patient. The quality control program for the gamma
camera includes acceptance testing and tests that need to be performed on a
routine basis. The nuclear medicine image acquired with the gamma camera
provides a snapshot of the patient’s in vivo radiopharmaceutical distribution
from a certain view and at a particular point in time. These images also can
be acquired as a dynamic (time-sequence) study or in conjunction with a
physiological gate such as the ECG.
• Regions of interest can be drawn about specific features to provide regional
quantitation or TACs of dynamic processes.
• Finally, nuclear medicine instrumentation continues to evolve, including the
development of devices designed for a specific clinical task such as breast
imaging. It is expected that this development will continue in the years
ahead.

46. REFERENCES
• Essentials of nuclear medicine imaging; Fred A.Mettler 2012
• The Requisites Ziessman - Nuclear Medicine, 4th ed. FRED A. METTLER
• Camera Systems. Publication 1141. Vienna, Austria: International Atomic Energy
Agency; 2003.
• IAEA Comprehensive Clinical Audits Of Diagnostic Radiology Practices A Tool For
Quality Improvement
• Nuclear Medicine Instrumentation Lecture Notes:2005; Ghoorun S
• Operational Levels In Radiopharmacy For Realigning Our Profession With International
Guidelines Richard E. 2015
• Chandra R. Nuclear Medicine Physics: The Basics. 7th ed. Philadelphia: Williams &
Wilkins; 2011.

47. THANK YOU VERY MUCH AND GOD
BLESS YOU