RESUMO
OBJECTIVES: Quantitative analysis of operator dose in cone-beam computed tomography guidance (CBCT-guidance) and the effect of protective shielding. METHODS: Using a Rando phantom, a model was set-up to measure radiation dose for the operator hand, thyroid and gonad region. The effect of sterile radiation-absorbing drapes and ceiling/couch shielding was measured. Using this model we calculated the dose, based on relevant clinical parameters. The procedures were divided in thoracic and abdominal group. Furthermore, dosimetry measurements were performed during clinical cases to correlate with our calculations. RESULTS: One hundred thirteen procedures were included between December 2007 and January 2010 (47 thoracic, 66 abdominal). The mean hand doses were 34.2 and 54.6 µSv (thoracic/abdominal respectively). The thyroid and gonad regions doses were 83.2 and 34.3 µSv in the thoracic, and 66.2 and 47.2 µSv in the abdominal group. Combined shielding reduced the dose by 98.2-98.9% (p<0.05). The radiation dose in clinical setting in the thoracic group (n=17) was 32.9 µSv (hand), 11.4 µSv (thyroid) and 16.0 µSv (gonad region). In the abdominal group (n=20) the doses were 43.4, 21.7 and 18.8 µSv respectively. CONCLUSION: The operator dose in CBCT-guidance without shielding is quite low, compared to the literature. Based on our data, between 375-830 cases can be performed staying below the yearly limit of 20 mSv effective whole-body dose.
