Furthermore, the influence of the PGC on the quantification and image quality is evaluated. Each sphere was filled with the same activity concentration measured by an independently cross-calibrated dose calibrator. Acquisition times were 2 min for F and Ga, and 10 min for I For reconstruction an OSEM algorithm was applied. For I the images were reconstructed with and without PGC. For the calculation of the RCs the activity concentrations in each sphere were determined; in addition, the influence of the background correction was studied.
There was lower background activity in the I images without PGC, which probably originates from an overcorrection of the scatter contribution. As a consequence PGC should be used for I For I there is only a slight influence on the quantification depending on the use of the PGC. However, there are considerable differences with respect to I image quality. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Frequently, radioiodine therapy is the treatment of choice in patients suffering from differentiated thyroid cancer DTC [1]. It is defined as the systemic administration of I sodium or potassium iodide for selective irradiation of thyroid remnants, microscopic DTC or other non-resectable or incompletely resectable DTC, or both purposes [1].
The determination of the I biokinetics of iodine-avid lesions for individualized treatment planning suffers from severe shortcomings of the quantification process using gamma-cameras mainly because of the high I photon energies [2]. With the long half-life of I of 4.
Due to the complex decay scheme of I see fig. Low energy photons cause strong geometry and vial dependency when measuring I in dose calibrators. This fact requires additional efforts for correct activity quantification [7]. Furthermore, prompt gamma photons with an energy of Most of their energy spectrum lies within the standard energy window of a modern LSO PET-scanner typically — keV including those events scattered with a small angle; therefore additional and wrong prompt coincidences are detected.
