Problem of study
Nowadays, Nuclear medicine represents one of the most important imaging
methods and components of modern medical practice, using unsealed sources to
give diagnostic information about diseases such as thyroid tumors. Besides
imaging the internal state of a patient’s body, it also provides both
anatomical and biological functional information of organs within the body.
Significantly, a regular quality control
testing and calibration of gamma cameras must be performed constantly to obtain
good quality images without abnormalities and artifacts. Although most nuclear
medicine departments perform routine quality controls in accordance with
National Electrical Manufactures Association NEMA (NU 1-2007) standard protocol
and International Electrotechnical commission IEC, in most cases the assessment
in terms of validity and applicability of these tests is not performed.
Specifically, in developing countries, imaging instruments can installed with
little or no funding for maintenance, quality control and the provision of
adequate scientific support. In such circumstances commercially made phantoms
may be prohibitively expensive and as a result quality controls may not be
implemented. Even when phantoms are available there are other restrictions to
its use, such as: many of the previously published and described quality
control procedures are complicated, time consuming or require a specialized
test environment and specific softwares. On top
of that, linearity, uniformity, and special resolution should be monitored
every morning. Due to the lack of seller independent quality control software,
the NEMA performance standard which is considered a major issue for running a
NEMA quality control test.
Consequently, a research worker
thinks it is necessary to develop a phantom that is user friendly for routine
gamma camera SPECT testing and with an inexpensive cost in this research.
Purpose of the thesis
Complete quality control of gamma cameras
involves the performance of a variety of sophisticated system function tests;
many of which demand expensive specialized equipment 13. The purpose of this
work is to develop a quality control phantom to optimize the quality control
process that checks the performance of the gamma camera. The procedure can be
done through developing and improving phantom techniques.
The main aim of this study is to develop a cost-effective, locally made and
easy to use quality control phantom for gamma cameras and to test its validity
relative to the standard results of the gamma camera.
The aim of quality control is to detect performance changes in a gamma
camera system that may affect the interpretation of results in clinical
studies. Obviously, we have a lot of factors contributing to the final image
quality. Including special resolution, uniformity, collimation and hardcopy
devices. On top of that, for certain types of studies other factors, such as
the count rate ability come into play. Additional tomographic imaging adds an
additional set of parameters that can affect the clinical image, which
includes: system center of rotation, gantry and collimator hole alignement,
rotatioal stability of the detector head, amplification of the photomultiplier
and intigrity of the reconstruction algorithms. On a daily basis there is a
limited amount of time that can be meaningfully used for system quality
control. Therefore, the main objective of a quality control programs should be
to monitor parameters that are sensitive to change in system performance and
most likely to affect clinical studies.
To generate a multipurpose quality control phantom to assess the linearity,
uniformity and resolution at the same time adjust, calibrate and quantify the perfomance
of gamma camera.
To offer an alternative to the gamma camera quality control phantom (based
on the protocols proposed by manufacturers and user associations) with local
materials easily accessible.
To evaluate the efficiency of the locally manufactured phantom in detection
of gamma camera malfunctions with comparison to standard ones, .
Quality Control is required to ensure that gamma cameras are functioning
properly and to detect problems before they impact on clinical studies.
Importance of the thesis
Quality control is an important procedure in nuclear medicine imaging.
The device of interest for this work is the gamma camera SPECT that is most used in the service of
nuclear medicine worldwide. A more detailed description of this work will be
developed throughout this research in order to achieve a multipurpose phantom
to test the special resolution, linearity and consistency of the gamma camera.
Thus it is necessary to perform quality control tests in the gamma camera
before running the experiment to prevent false results. Such tests generally
use radioactive material inside phantoms for evaluation of gamma camera
parameters in quality control procedures.
A general phantom used for quality assurance can be expensive and not
easily accessible. In addition, due to the fact that there are different gamma
camera configurations and detector sizes, different phantoms will be required
during tests. Thus it will be of great benefit to nuclear medicine departements
to have an alternative and cheaper way to manufacture phantoms according to
their own needs.
A phantom provides consistent perfomance information for quality control of
gamma camera systems. This work will describe the methodolgy of developing a
new phantom and its comaprisson to the conventional phantom’s assessment of the
performance of the gamma camera.