Gamma Camera, is a device used in nuclear medicine that implies a
radioactive material as a photon source and is coupled with a specially
designed computer, which aids in the collection and interpretation of data1.
Since the gamma camera’s invention in 1957 by H.O.Anger 2,3 it remains an
important and broadly used molecular imaging instrument in nuclear medicine. It
images the distribution of gamma ray emitting radionucleides and provides
detailed information of the biological processes occuring in the human body at
cellular and molecular levels and can also detect disease in its earlier stages
Today, it is one of the most important modalities and components of modern
medical practice. It uses open sources(unsealed sources) to provide diagnostic
information and treat diseases such as tumors. Besides visualizing the internal
state of a patient’s body, it also provides both anatomical and biological
functional information about the subjects being imaged.
The patient is injected with a radiopharmaceuticals (medicine to which a radioactive material has
been attached) which emits gamma rays that can be captured by the head of a gamma camera
that is connected to a computer that
processes the information into a two dimensional image of a
cross-section. These cross-sectional images can be reassembled to form a 3D
image of the patient’s body.
There are several types of different
radiopharmaceuticals, otherwise known as tracers, available to study the
different parts of the human body. According to the condition to be diagnosed
or treated the most appropriate tracers will be determined for use.
The gamma camera is frequently
called Anger camera, because it detects gamma rays. When it is designed for
tomography, it is also called a SPECT camera. There has been a great deal of progress in the
development and improvement of methods to accurately quantify images in nuclear
medicine including: the development of tomography exams in the mid-1980s, a
growing clinical exploitation, thanks to the production of the first generators
used to obtain metastable technetium (99mTc) in 1964 with its subsequent
developments of pharmaceutical radio, the beginning of 1970s was marked by
continuous progress which lead to the
invention of Positron Emission
Tomography (PET) and by the end of 1970s the 3D image rendering Single Photon
Emission Computerized Tomography (SPECT) device was invented5.
Nowadays, such techniques measure the
occurrence of the two annihilated photons that follow positron decay in the
organ of interest to diagnostic pathologic evidence and the determination of
myocardial viability 6, 7.
Due to the constant
development in the field of computer programs and quality assurance technologies
developing and improving the gamma camera, SPECT has been possible throughout
the years. As a result the gamma camera SPECT’s performance was optimized, nonetheless SPECT has
well-known limitations in spatial resolution and statistical quality (Cherry
SR. ea.al. 2003, Jaszczak RJ 1980). The
performance parameter most commonly evaluated as a part of a routine gamma
camera quality control program include uniformity, spatial resolution, spatial
linearity, and energy resolution and peaking (Zanzonico,2008) 8.
Therefore, Nuclear Medicine is the
basis of diagnostic and therapeutic medicine, which is both a privilege and
advantage for doctors. Implementing a quality control within a medical imaging
center is essential to ensure quality and provide safe care; thus reliable
results. Based on scintigraphic imaging for the detection of radiation and the
location of photons emitted by radioactive decays in the patient’s body, a need
to evaluate and monitor the performance of the imaging system: the Gamma
In quality assurance process, it is
important that all the equipment used must be subject to a quality control
program. Ideally the quality control should be established by a group of
qualified personnel: a radio-physicist, technician or maintenance engineer
(trained on the device by the manufacturer), laboratory technician, and a
Maintaining and improving the health
and well-being of patients by providing the best health care through: competent
medical personnel and reliable the diagnostic equipment brings about patient
Thereby, the process of implementing a quality
protocol has become a way of regulating the health system to achieve a defined
level of security, conformity and reliability, ensuring the absence of failure.
The camera test protocols have been constantly updated in hand with
technological and software developments. Some standardized procedures (National
Electrical Manufactures Association NEMA, International Electrotechnical
Commission IEC) 9,10 are primarily intended for manufacturers, while other
protocols (American Association of Physicists in Medicine-Nuclear AAPM, International
Atomic Energy Agency IAEA, European Association for Nuclear Medicine EANM) 11
are written by professional boards and are intended for the user.
In the medical field it is necessary
to use test objects or phantoms to adjust, calibrate and quantify the
performance of imaging equipment. In order to carry out the mentioned
procedures, phantoms with different geometrical forms are used. In nuclear
medicine, where an emission image is made, the phantoms used are generally
composed of sealed containers that can be filled with radioactive liquid
solution of variable concentrations 12.