(Sunday, 7/12/2020) 11:30 AM - 12:30 PM [Eastern Time (GMT-4)]
Room: Track 1
Purpose: quantify the effect of lead shielding on patient dose in digital radiography with Automatic Exposure Control (AEC) driven imaging systems
Methods: anthropomorphic pelvis phantom was imaged using an abdomen protocol (81 kV, HVL = 3.04 mm Al, mAs determined by central AEC cell) on a Philips Diagnost radiographic system. Exposures were made with varying lead shielding coverage (LSC) equal to 0, 10, 15, 25, 33, 40, 45 and 66% of the field of view introduced from the pelvic region. A calibrated radiation dosimeter measured the entrance surface air kerma (ESAK) of the phantom at the edge of the open field. The central ray ESAK was estimated from the edge measurement to correct for heel effect variations. Transmitted air kerma under the lead was also measured. A personal computer program (PCXMC 2.0) calculated organ doses and effective dose from the ESAK, kV, and HVL using Monte Carlo photon transport. PCXMC organ dose evaluations and risk assessments were based on ICRP-103 organ weighting factors.
Results: lead shielding in the beam, ESAK and radiographic techniques increased steadily and spiked around 45% LSC when shielding impinged on the central AEC cell. Dose Area Product and total effective body, colon and small intestine doses were observed to lower as more lead shielding was introduced but sharply increased after 45% LSC. Testicle dose lowered substantially with LSC of the gonadal region and fractionally increased beyond 45% LSC. Ovaries, uterus, urinary bladder, prostate and bone marrow doses increased and spiked after 45% LSC.
Conclusion: protective effect was observed for ovaries, uterus and abdominal organs by using lead shielding. Due to the relative isolation of the testicles from abdomen-pelvis organs, a protective effect was observed with LSC. In most cases, use of lead shielding in AEC driven radiographic system increased organ doses and total effective body dose.
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