This study evaluates the impact of thermoluminescent dosimeter (TLD) ring orientation on radiation dose measurements in a nuclear medicine environment. Specifically, it investigates the differences between wearing the TLD ring facing towards (inwards) versus away from (outwards) the radiation source using a simple home-made finger phantom. Results demonstrated an average difference of 94% inwards versus outwards, emphasising that incorrect ring orientation significantly reduces dosemeter effectiveness. Increased awareness on correct ring placement when handling radioactive sources is essential for accurate finger doses.
PROBLEM
Instinctive ring-wearing habits, such as placing rings with decorative elements facing outward (diamond-up), leads to incorrect TLD ring orientation. This instinct, coupled with minimal awareness, reduces the effectiveness of TLD rings. There is insufficient information in personal dosimetry regarding the impact of correct versus incorrect ring placement.
METHODS
A home-made finger phantom was constructed:
DISCUSSION/FURTHER WORK
The data consistently demonstrated a significant difference in radiation dose readings between the two orientations. On average, the inward-facing rings recorded doses 94% higher than the outward-facing rings, with specific differences ranging from 92% to 96% across the tests. Some limitations exist within this experiment including the finger phantom not being a perfect representation of human anatomy, however densities and size were matched accordingly. Only 99mTc was used within this study; further studies using a variety of radioactive sources commonly used in nuclear medicine could provide a broader understanding of dosemeter accuracy. More testing is required to establish if the significant difference observed is consistent in both simulated and real-life working environment.
Further research is currently ongoing using Monte Carlo simulation techniques within the Geant4 framework to replicate the experimental setup. Geant4 is a well-established tool for simulating radiation interactions and dosimetry in nuclear medicine. This simulation will provide a greater insight into the interactions within the phantom and TLD rings. The results will be compared with empirical data to validate the findings.
CONCLUSION
The orientation of TLD rings substantially affects the measured radiation dose when observed using a finger phantom. These findings underscore the importance of correct dosimeter placement for accurate extremity dose assessment in nuclear medicine when handling radioactive sources. It is possible that if you do not wear your ring facing the radiation source, there may be no benefit in wearing the ring at all. More testing and awareness on this issue is required.
Presented by Scott Grieve.