| dc.description | A safe and efficient Nuclear Medicine Services (NMS) performance depends, among
other factors, on a complete quality assurance program, mainly in the case of the
activity meters. Many elements may influence this equipment response, being the major
errors related to vials characteristics, such as volume and geometry, as presented in
other studies [1,2]. Correction factors must be applied in order to avoid patient exposure
to excessive doses.However, another aspect that should be taken into account is how
much radioactive material is lost during the radioisotope labeling, a process that
includes many recipient changes.In this study we present the estimated activity lost
during 99mTc labeling process and show how important is to add this value to the total
activity measured in a new ???in situ??? calibration procedure, in which the activity meter is
not removed from its place of use. For the radioactive residue determination99mTc
labeling procedure was reproduced under laboratorial conditions, resulting in losses of
up to 40 %. However greater errors are expected in a NMS. Activity meter calibration
using two methodologies: the first consists in a direct comparison between the two
systems with the same vial (P6-P6 and 10R-10R), and the second is a comparison
made using two different vials (P6-10R), with and without geometry and residual activity
corrections. A calibration factor of 0.999 was obtained in the reference situation. The
same procedure performed without the application of the necessary correction factors
resulted in a variation of almost 3 %, which is high considering the test was made under
controlled conditions and less residue was left inside vials. The ???in situ??? calibration
procedure worked well and was important to present the need of correction factors
application, including the residue activity measurement. | |
