Optimización de variables temporales y dosimétricas en algoritmos ultra-rápidos para estudios de gammagrafía ósea en un tomógrafo de emisión de fotón único (SPECT)

Abstract

The following work has been made by a student with the purpose of getting to know an area which is quite an unknown for the physics students in the ULL. An area that is going through a great growth due to the investments done for supporting it and that is demanding more specialists every year. This work shows the procedure and the results of a study made with various objectives, but also serves as an introduction to the medical physics and the nuclear medicine for those who do not know about these subjects, so anyone can read and enjoy it. Coming to the point, the main aim of the study is to ascertain in which manner does the reduction of three parameters, two of them of the SPECT and the other one of the Activity introduced into the Jaszczak Phantom, independently affect to the quality of the resulting tomography. These parameters are the time in every stop of the SPECT’s detectors, the angle of rotation of the detectors between each stop and the Activity of radiopharmaceutical given to the patient before a SPECT. To achieve this goal, several tests are done changing the parameters and obtaining different tomographys corresponding to the various combinations of time, angle and dose of radiopharmaceuticals. These tomographys are analyzed using the software ImageJ, creating ROIs in the valuable areas and measuring the mean of the signal per pixel and the standard deviation. With these measures, two parameters are calculated in order to know about the resolution of the SPECT (FTC) and the quality of the results (SNR). Then, by calculating another parameter relative to the tomographys’ quality (CNR) and using the Rose criterion it is estimated whether or not the images are valid for the clinical diagnosis and also how the diminution of the mentioned parameters affect the results. The other objective of the study is to verify the result of an article that states that a SPECT can be reduced from 13 to 4 minutes without loosing its diagnostic capacity. Since in the study shown in the article, they only argue they theory with the opinion of seven doctor, it must be proven with empirical results in our study with the Rose criterion. The decrease in time per test, in addition to assuming an improvement in patient comfort, could also improve the quality of the result since in a short test the patient would be less likely to move. With a significant reduction in the duration of the SPECTs, the number of tests that are carried out per day could also be increased and, being this a diagnostic test, the fact of being able to reduce the dose of radiopharmaceutical that is supplied to the patient will also be an advantage because of the reduction of the risk of negative effects of the gamma radiation that is emitted inside the body. A reduction in the dose used would also have as a consequence a decrease in the economic costs of the SPECT.