Gamma Camera, is a device used in nuclear medicine that implies aradioactive material as a photon source and is coupled with a speciallydesigned 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 animportant and broadly used molecular imaging instrument in nuclear medicine. Itimages the distribution of gamma ray emitting radionucleides and providesdetailed information of the biological processes occuring in the human body atcellular and molecular levels and can also detect disease in its earlier stages4.Today, it is one of the most important modalities and components of modernmedical practice.
It uses open sources(unsealed sources) to provide diagnosticinformation and treat diseases such as tumors. Besides visualizing the internalstate of a patient’s body, it also provides both anatomical and biologicalfunctional information about the subjects being imaged. The patient is injected with a radiopharmaceuticals (medicine to which a radioactive material hasbeen attached) which emits gamma rays that can be captured by the head of a gamma camerathat is connected to a computer that processes the information into a two dimensional image of across-section. These cross-sectional images can be reassembled to form a 3Dimage of the patient’s body. There are several types of differentradiopharmaceuticals, otherwise known as tracers, available to study thedifferent parts of the human body. According to the condition to be diagnosedor treated the most appropriate tracers will be determined for use. The gamma camera is frequentlycalled Anger camera, because it detects gamma rays. When it is designed fortomography, it is also called a SPECT camera.
There has been a great deal of progress in thedevelopment and improvement of methods to accurately quantify images in nuclearmedicine including: the development of tomography exams in the mid-1980s, agrowing clinical exploitation, thanks to the production of the first generatorsused to obtain metastable technetium (99mTc) in 1964 with its subsequentdevelopments of pharmaceutical radio, the beginning of 1970s was marked bycontinuous progress which lead to theinvention of Positron EmissionTomography (PET) and by the end of 1970s the 3D image rendering Single PhotonEmission Computerized Tomography (SPECT) device was invented5. Nowadays, such techniques measure theoccurrence of the two annihilated photons that follow positron decay in theorgan of interest to diagnostic pathologic evidence and the determination ofmyocardial viability 6, 7.Due to the constantdevelopment in the field of computer programs and quality assurance technologiesdeveloping and improving the gamma camera, SPECT has been possible throughoutthe years. As a result the gamma camera SPECT’s performance was optimized, nonetheless SPECT haswell-known limitations in spatial resolution and statistical quality (CherrySR. ea.al. 2003, Jaszczak RJ 1980).
Theperformance parameter most commonly evaluated as a part of a routine gammacamera quality control program include uniformity, spatial resolution, spatiallinearity, and energy resolution and peaking (Zanzonico,2008) 8. Therefore, Nuclear Medicine is thebasis of diagnostic and therapeutic medicine, which is both a privilege andadvantage for doctors. Implementing a quality control within a medical imagingcenter is essential to ensure quality and provide safe care; thus reliableresults.
Based on scintigraphic imaging for the detection of radiation and thelocation of photons emitted by radioactive decays in the patient’s body, a needto evaluate and monitor the performance of the imaging system: the GammaCamera.In quality assurance process, it isimportant that all the equipment used must be subject to a quality controlprogram. Ideally the quality control should be established by a group ofqualified personnel: a radio-physicist, technician or maintenance engineer(trained on the device by the manufacturer), laboratory technician, and adoctor.Maintaining and improving the healthand well-being of patients by providing the best health care through: competentmedical personnel and reliable the diagnostic equipment brings about patientsatisfaction. Thereby, the process of implementing a qualityprotocol has become a way of regulating the health system to achieve a definedlevel of security, conformity and reliability, ensuring the absence of failure.The camera test protocols have been constantly updated in hand withtechnological and software developments. Some standardized procedures (NationalElectrical Manufactures Association NEMA, International ElectrotechnicalCommission IEC) 9,10 are primarily intended for manufacturers, while otherprotocols (American Association of Physicists in Medicine-Nuclear AAPM, InternationalAtomic Energy Agency IAEA, European Association for Nuclear Medicine EANM) 11are written by professional boards and are intended for the user.
In the medical field it is necessaryto use test objects or phantoms to adjust, calibrate and quantify theperformance of imaging equipment. In order to carry out the mentionedprocedures, phantoms with different geometrical forms are used. In nuclearmedicine, where an emission image is made, the phantoms used are generallycomposed of sealed containers that can be filled with radioactive liquidsolution of variable concentrations 12.