Fetal radiation dose in computed tomography.

Area of Science:

• Medical Physics
• Radiological Imaging
• Radiation Dosimetry

Background:

• Accurate estimation of fetal dose (Df) during Computed Tomography (CT) examinations is crucial for risk assessment.
• The relationship between volumetric CT dose index (CTDI vol) and Df requires precise characterization across various protocols and gestational ages.

Purpose of the Study:

• To investigate the correlation between CTDI vol and mean Df using metal-oxide-semiconductor field-effect transistor measurements.
• To evaluate Df in different pregnancy stages and CT protocols, considering fetal position relative to the primary beam.

Main Methods:

• Utilized an anthropomorphic female phantom at four gestational stages on a 64-slice CT scanner.
• Employed metal-oxide-semiconductor field-effect transistor dosimetry to measure Df.
• Analyzed data from trauma, abdomino-pelvic, and pulmonary angiography protocols with automated tube current modulation.

Main Results:

• Automated tube current modulation maintained relatively constant mean Df across pregnancy stages for trauma (4.4-4.9 mGy) and abdomino-pelvic (2.1-2.4 mGy) protocols.
• Pulmonary angiography protocol showed an exponential increase in mean Df as the distance from the scan range end decreased (0.01-0.09 mGy).
• Relative mean Df compared to CTDI vol ranged from 0.80-0.97 (trauma), 0.57-0.79 (abdomino-pelvic), and 0.01-0.05 (pulmonary angiography).

Conclusions:

• CTDI vol serves as a reliable upper estimate for fetal dose when the fetus is within the primary CT beam.
• For fetuses outside the primary beam, Df estimation necessitates incorporating the distance from the scan range.
• These findings aid in optimizing CT protocols to minimize radiation exposure to the fetus.