3. Contents:
First Speaker (AbdulAziz AlMahmoud)
A. Introduction
B. Radiopharmaceuticals
Second Speaker (AbdulRahman AlZaydi)
C. Gamma Camera
Third Speaker (Abdullah AlWeleyi)
D. Single Photon Emission Computed
Tomography (SPECT)
E. Conclusion
4. What is radiation?
Radiation is a type of energy,
which exists in our environment in
many forms and comes from both
natural and man-made sources.
Light that allows us to see and the
warmth we get from the sun or
from nature are natural forms of
radiation.
5. e.g. of man-made radiation
include the microwave radiation
that is used for cooking and radio
waves for communication over
long distances ionizing radiation
comes from both natural and
man-made sources.
6. What is nuclear medicine ?
This is a branch of medicine that
uses radiation from radioactive
tracers to provide information
about the function of specific
organs.
In some cases, radioactivity can
be used to treat certain conditions
such as an overactive thyroid.
7. Follow..
Nuclear medicine studies use ionizing radiation,
as do x-ray studies.
radioactive tracers or radiopharmaceuticals
commonly used are quickly eliminated from the
body through its natural functions.
In addition, the tracers used rapidly lose their
radioactivity.
In most cases, the dose of radiation necessary for
a scan is very small.
For example, a patient having a lung scan is
exposed to the same dose of radiation they
would receive from eight return air flights
between Sydney and London.
8. What is pharmaceutical?
The radioactive materials administered to
patients are known as radiopharmaceuticals.
These consist of :
Chemical molecule which determines the
behavior of the radiopharmaceutical in the
body a radionuclide.
The radiation emitted by the radionuclide may
be detected from outside the body by a
radionuclide imaging device (a gamma
camera) or may be detected
In a sample of a body fluid (e.g. plasma or urine)
9. Radiopharmaceuticals
Diagnostic radiopharmaceuticals must
deliver the minimum possible radiation
dose to the patient while still obtaining
the required diagnostic information.
Therapy radiopharmaceuticals must
deliver the maximum radiation dose to
the diseased organ or tumor, while
minimizing the radiation dose to non
target tissues such as the bone marrow.
Ensure minimal irradiation of other parts.
10. What is a half-life?
Nuclear medicines used for diagnosis
or treatment generally have short half-
lives.
A half-life is the time it takes for the
level of radioactivity to drop to half the
starting level.
Nuclear medicines typically have a
half-life of several hours or days.
This means they rapidly lose their
radioactivity level within the
predetermined half-life.
11. GAMMA CAMERA
1-Principle:
The Gamma or Scintillation Camera is an imaging device
that is most commonly used in nuclear medicine. It is also
called the Anger Camera.
Gamma Cameras detect radiation from the entire field
of view simultaneously and therefore are capable of
recording dynamic as well as static images of the area
of interest in the patient.
The gamma cameras usually consists of several
components: a detector, a collimator, PM tube, a
preamplifier, an amplifier, a pulsed-height analyzer
(PHA), an X-, Y-positioning circuit, and display or
recording device.
12.
13.
14.
15. GAMMA CAMERA
2-Operation:
The gamma rays emitted by the
radiopharmaceutical (in the patient)
are first collimated (by a specific
collimator) and then detected by a
detector (usually scintillator)
16.
17. Single Photon Emission
Computed Tomography
(SPECT)
Tomograms: a series of views
(profiles) are acquired at different
angles around
Filters: Fourier transform "Sampling
and correction
18. (SPECT)
SPECT is also widely used and the
process of injecting a radioactive tracer
is the same as the PLANAR technique.
Instead of being stationary, the gamma
camera moves around the body
providing a series of images. This takes
about 20-30 minutes.
SPECT and PLANAR imaging are highly
convenient technologies as they use
radiopharmaceuticals, which can be
easily distributed, stored and mixed
ready for use at nuclear medicine clinics
and hospitals.
19.
20. Collimator
A collimator is a device that narrows a beam of
particles or waves. To "narrow" can mean either
to cause the directions of motion to become
more aligned in a specific direction (i.s.,
collimated or parallel) or to cause the spatial
cross section of the beam to become smaller.
Gamma rays are emitted isotropically (in all
directions)
Using only a detector would not result in an
image because there will be no relationship
between the position at which the gamma rays
hit the detector and the origin of the gamma
rays (in the patient)
21.
22.
23.
24. Detector
Detector, by which increase the
thickness of a detector increase
probability of Complete
absorption of gamma ray.
Detector are used in gamma
camera, but this decrease the
sensitivity Of the camera, because
many gamma rays () may escape
from the detector without
interaction.
25. Detector
٠Spatial resolution: the smallest separation
required between two small objects to be
detected and distinguished as two separated
objects
٠Energy resolution: bill width half maximum
(FWHM)
٠Non-Uniformity: the slightly different response
of different areas of the detector of the camera
to a uniform radioactive source
٠Spatial distortion: random or systematic error
of determining event location
٠Counting-rate: counts / unit of time. It is
assessed as the Observed count-rate (gamma
camera) vs. True count-rate (source activity)
٠Sensitivity: count-rate / unit of radioactivity
26. References:
Books:
1_Nuclrear Medicine and PET/CT, sixth edition.
2_The Essential Physics of Medical Imaging, third edition.
3-Physics Radiobiology of Nuclear Medicine, third edition.
Others:
1_Nuclear Medicine.ppt
2_Introduction to Nuclear Medicine.ppt
3_Imaging with Radionuclides.ppt
" In radionuclide imaging (nuclear medicine) clinical data is derived from observing the distribution of a pharmaceutical administrated to the patient
" By incorporating a radionuclide into the pharmaceutical, measurements can be made of the distribution of this radiopharmaceutical by noting the amount of radioactivity present " These measurements may be carried out either in-vivo or in-vitro
" In vivo imaging is the most common type of procedure in nuclear medicine
" It offers the potential, unique among all other imaging techniques, of demonstrating hmction rather than simply anatomy
" It is usually carried out with the so-called gamma camera
" In vitro measurements are made on samples of materials taken from the patient, such as urine, to determine the amount of the radioactivity present
٠ Half life: how quickly the radioactivity will decay
- Too short: the activity will have significantly decay before imaging has
started
- Too long: the patient will remain radioactive for a considerable time
after the examination
- Roughly, the half life should of a similar length of that of the exam
(few hrs) (99mTc has a half life of 6 hrs)
٠ Type and energy of emission:
- The higher the energy of the radiation the higher is the penetration, but
- The more difficult to be stopped (detected) by the gamma camera
- Ideally, 150 keV is preferred (99mTc emits 140 keV gamma ray)
- It is necessary to avoid those radionuclides which have a and p emissions
٠ Pharmaceutical labelling: it is the incorporation of the radionuclide with a pharmaceutical:
- Thus, the radionuclide should be chemically suitable for labling. This is not easy to achieve as all the elements of biological interest, such as C, O, N have radioisotopes which do not meet the criteria above but instead emit positron
- 99mTc has been successfully incorporated into (labelled with) a large
range of pharmaceuticals
٠ Production of radionuclides:
- The short-lived radionuclides produced by either reactor or cyclotron will decay significantly during transportation (to the hospital)
- The third mode pf production, the generator, which used to produce 99mTc, provides the answer to the transportation problem
1. Principle
٠ The gamma camera is the principal instrument for imaging in nuclear medicine
٠ It consists of a large detector in front of which the patient is positioned
٠ Dual- and triple- detector gamma camera are also available
٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as:
- The study acquisition time or the number of counts to be acquired
- The pulse height analysers (PHAs) to reject scattered radiation
- The display mode: soft-copy and/or hard-copy (photographic film)
1. Principle
٠ The gamma camera is the principal instrument for imaging in nuclear medicine
٠ It consists of a large detector in front of which the patient is positioned
٠ Dual- and triple- detector gamma camera are also available
٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as:
- The study acquisition time or the number of counts to be acquired
- The pulse height analysers (PHAs) to reject scattered radiation
- The display mode: soft-copy and/or hard-copy (photographic film)
1. Principle
٠ The gamma camera is the principal instrument for imaging in nuclear medicine
٠ It consists of a large detector in front of which the patient is positioned
٠ Dual- and triple- detector gamma camera are also available
٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as:
- The study acquisition time or the number of counts to be acquired
- The pulse height analysers (PHAs) to reject scattered radiation
- The display mode: soft-copy and/or hard-copy (photographic film)
1. Principle
٠ The gamma camera is the principal instrument for imaging in nuclear medicine
٠ It consists of a large detector in front of which the patient is positioned
٠ Dual- and triple- detector gamma camera are also available
٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as:
- The study acquisition time or the number of counts to be acquired
- The pulse height analysers (PHAs) to reject scattered radiation
- The display mode: soft-copy and/or hard-copy (photographic film)
٠ The gamma rays emitted by the radiopharmaceutical (in the patient) are first collimated (by a specific collimator) and then detected by a detector (usually scintillator)
٠ At the detector, the gamma rays are converted into visible light by the scintillation crystals
٠ This light is, in turn, transformed into electronic signals by an array of photomultiplier tubes (PMT) placed at the rear face of the crystals
٠ The output from the PMT is converted into three signals: X and Y (gives the spatial location of the scintillation) and Z which represents the energy deposited in the crystal
٠ The Z-signal passes through a pulse height analyzer (PHA) to check whether the energy is within the range of interest before display
٠ The gamma rays emitted by the radiopharmaceutical (in the patient) are first collimated (by a specific collimator) and then detected by a detector (usually scintillator)
٠ At the detector, the gamma rays are converted into visible light by the scintillation crystals
٠ This light is, in turn, transformed into electronic signals by an array of photomultiplier tubes (PMT) placed at the rear face of the crystals
٠ The output from the PMT is converted into three signals: X and Y (gives the spatial location of the scintillation) and Z which represents the energy deposited in the crystal
٠ The Z-signal passes through a pulse height analyzer (PHA) to check whether the energy is within the range of interest before display
"Tomograms: a series of views (profiles) are acquired at different angles around
the patient
"Back-projection: reconstructs each profile at the appropriate angle
" Filters: Fourier transform "Sampling and correction
٠ Gamma rays are emitted isotropically (in all directions)
٠ Using only a detector would not result in an image because there will be no relationship between the position at which the gamma rays hit the detector and the origin of the gamma rays (in the patient)
٠ Therefore, a collimator must be employed
٠ The typical collimator consists of a lead plate through which runs an array of small holes
٠ Only those gamma rays which travel a long a hole axis will pass into the scintillation crystals, while the angled radiation will be absorbed by the lead
٠ The two parameters describing collimator performance are:
- Spatial resolution: the minimum separation needed between two small objects if they are to be distinguished (typically: 7mm)
- Sensitivity: the proportion of those gamma rays incident on the collimator which pass through to the detector (typically: 0.1%)
٠ The performance of the collimator depends upon its dimensions
٠ It is not possible to optimise the both two parameters of a collimator
٠ The choice must be made depending upon the type of investigation
٠ Also different collimators are available for the deferent energy used
- low energy: < 140 keV
- Medium energy: < 260 keV - High energy: < 400 keV
" However, there are different types of collimator, based on sensitivity, resolution and energy:
- Low energy - high resolution
- Low energy - general purposes
- Low energy - high sensitivity
- Medium energy - general purposes
- High energy - general purposes
3. Collimator
٠ Also, collimator is classified based on its design into four types:
- Parallel-hole collimator: used for most studies
- Converging collimator: for magnification
- Diverging collimator: to minify a large object
- Pin-hole collimator: a lead cone with a small hole for small object e.g. thyroid gland
" While the collimator modifies the gamma ray flux so as to create an image, it is the fltnction of the detector to convert the gamma rays into a usefltl image
" This can be done in two stages:
- The first stage is the conversion of the gamma rays into visible light by means of a scintillation crystals which is usually made of sodium iodide with thallium added NaI(Tl)
- The second stage is these scintillations are turned into electrical signal by the PMTs
" The effectiveness of NaI(Tl) at stopping the gamma rays (the efficiency) depends not only on its density and Z number but also on the thickness of ctystal used " The scintillator ctystals are the most expensive part of the gamma camera
" However, scintillation detector has lower energy resolution than the semiconductor detectors " These detectors need, however, cooling system