PT - JOURNAL ARTICLE AU - Tiwari, Ashok AU - Andriotty, Matthew AU - Agasthya, Greeshma AU - Sunderland, John AU - Osborne, Dustin AU - Kapadia, Anuj TI - <strong>Assessment of impact of activity extravasation of radiopharmaceuticals in PET imaging</strong> DP - 2024 Jun 01 TA - Journal of Nuclear Medicine PG - 242321--242321 VI - 65 IP - supplement 2 4099 - http://jnm.snmjournals.org/content/65/supplement_2/242321.short 4100 - http://jnm.snmjournals.org/content/65/supplement_2/242321.full SO - J Nucl Med2024 Jun 01; 65 AB - 242321 Introduction: The usage of nuclear medicine procedures in the clinic has been increasing steadily, leading to a renewed interest in the extravasation of radiotracers. To our knowledge, this topic is understudied but holds great potential for enhancing our understanding of extravasation in PET imaging within clinical settings. This work has two primary objectives: (1) to quantify the absorbed doses resulting from radiotracer extravasation in PET imaging, both locally at the site of extravasation and with the extravasation location as a source of exposure to organs throughout the body, and (2) to investigate the biological impact of extravasation within the injection site at the cellular level.Methods: A radiation dosimetry simulation was performed using a whole-body 4D Extended Cardiac-Torso (XCAT) phantom embedded in the GATE Monte Carlo platform. A 10 mCi dose of 18F-FDG was chosen to simulate a typical clinical PET scan scenario, with 10% of the activity extravasated in the antecubital fossa of the right arm of the phantom. The extravasation volume was represented by a cylinder measuring 4 cm in diameter and 5 cm in length. Absorbed dose contributions were calculated for the first two half-lives, while the remaining half-lives were assumed to clear biologically. Organ-level absorbed doses were estimated by considering photon emissions from positron annihilation, optimizing computational efficiency. Energy deposition was simulated both at the local extravasation site and in multiple organs of interest and converted to absorbed dose based on their respective masses. Each simulation was repeated ten times to estimate Monte Carlo uncertainties. Biological impacts on cells within the extravasated volume were evaluated by randomizing cells and exposing them to a uniform radiation source of 18F and 68Ga. Particle types, their energies, and direction cosines were recorded in phase space files using a separate Geant4 simulation to characterize their entry into the nucleus of the cellular volume. Subsequently, the phase space files were imported into the TOPAS-nBio simulation to assess the extent of DNA damage, including double-strand breaks (DSBs) and single-strand breaks (SSBs). Results: Organ-level dosimetric estimations are presented for 18F and 68Ga radionuclides in various organs of interest. The total absorbed dose in the extravasated volume with 10% extravasation was 0.29±0.01 Gy using 18F and 0.17±0.01 Gy using 68Ga. When 18F was present in the extravasated volume, the average absorbed dose per nucleus was 0.034±0.002 Gy, with 0.71±0.05 DSBs/nucleus and 19.34±1.85 SSBs/nucleus. Additionally, with 68Ga, the absorbed dose per nucleus was 0.013±0.0016 Gy, with 0.26±0.04 DSBs/nucleus and 7.32±1.05 SSBs/nucleus. Absorbed doses in the other organs of interest were on the order of micro-gray (μGy).Conclusions: Our results indicate that the absorbed dose resulting from activity extravasation in PET imaging is unlikely to cause deterministic effects, as the simulated absorbed doses remain below the threshold that triggers such effects. Moreover, the extravasated organ-level absorbed doses were found to be clinically insignificant across various simulated organs. Minimal DNA damage was estimated at the extravasation site, suggesting that long-term harm, such as radiation-induced carcinogenesis, is highly unlikely.