Aims and objectives
The purpose of this study was to evaluate the effect of gantry angulation,
scanning techniques (spiral vs sequential) and barium eye shielding on radiation dose to the eye lens during head CT examinations.
Methods and materials
An anthropomorphic phantom was scanned with a routine head CT protocol using a 16-slices CT equipment (Fig. 1).
Three exposures were performed for each of the following settings with different combinations:
spiral and sequential scanning techniques
with and without barium shields (Fig. 2)
gantry angulation at 12°,
0°,
-12°and -22°(Fig. 3) using the orbitomeatal line as reference.
Thermoluminescent dosimeters (TLD) were used to measure the entrance skin dose (ESD) in eye lens.
Results
An ESD reduction range from 15% to 21% was verified in all configurations with barium shields (Fig. 4).
The lower ESD value was observed in configuration with barium shields and gantry angulation at -12°(28,86mGy).
In terms of effective dose,
it was found that the sequential scanning technique at 0°with no barium shield presents the higher value (0.43mSv),
although below the dose threshold.
The lower effective dose (0.29mSv) was verified with the use of barium shield in combination with -12°of gantry angulation (Fig. 5).
Conclusion
Comparing the differents results we concluded:
An ESD reduction range from 15% to 21% was verified in all configurations with barium shields.
In a similar study,
Mourão,
Silva,
& Alonso (2013) with a bismuth shield verified a redution of 37%;
The sequential scan presents higher values than spiral,
with or without protection,
because the eye lens is continuously irradiated,
despite the back scatter of the radiation (Batista,
2011).
Gantry tilt (between -10° and -12°) shows higher dose reduction in the ESD on eye lens,
as...
Personal information
Mónica Reis (BSc),
Professor in the Medical Imaging and Radiotherapy Department,
Health School - University of Algarve,
Portugal.
E-mail:
[email protected]
Sónia Rodrigues (MSc),
Professor in the Medical Imaging and Radiotherapy Department,
Health School - University of Algarve,
Portugal.
Radiographer in Centro Hospitalar Universitário do Algarve,
Portugal.
E-mail:
[email protected]
António Abrantes (PhD),
Professor in the Medical Imaging and Radiotherapy Department,
Health School - University of Algarve,
Portugal.
Researcher in CICS.NOVA.UÉvora (Interdisciplinary Centre of Social Sciences – Évora Centre) and Member of Studies Center in Healthcare (CES-ESSUALG)....
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