Estimation of patient doses in paediatric cardiovascular interventional radiology under specific exposure conditions

Xin CHEN; Weiyuan ZHANG; Weihai ZHUO

ABSTRACT

Objective:

To estimate the organ doses and effective doses to different-age children during cardiovascular interventional radiological procedures under some specific exposure conditions, and explore the main influencing factors on the doses.

Methods:

Based on the paediatric reference computational phantoms recommended in the ICRP Publication 143, several specific exposure models of cardiovascular intervention were built, and the Monte Carlocook MCNPX 2.7.0, was used to calculate the organ doses and effective doses for 1-, 5-, 10- and 15-year-old children. To validate the simulation result , an experiment was implemented by putting the thermoluminescent dosimeters in a 5-y old phantom (ATOM 705-D) manufactured by the CIRS Inc. in the USA.

Results:

Both the height and weight of the reference children for 1-, 5- and 10-year-old provided for by Chinese national standards are nearly in consistency with those recommended by ICRP, and even for the 15-year-old, the maximum relative deviations of the height and weight are only -1.9% and -5.7%, respectively. Under the exposure condition where the focal spot to image receptor distance (SID) was 90 cm, the length of square field of view (FOV) was 30 cm with a dose area product (DAP) of 45 Gy·cm 2, the relative deviations between simulated and measured doses to main organs/tissues within the irradiation filed were within ±6.7%. Under the same exposure conditions, the younger the children, the larger the organ doses and effective doses, and the effective doses could vary by a factor of about 5 among the 4 age groups. The conversion coefficient between the organ dose and the value of DAP was not only closely related to the age of children, but also affected by the FOV.

Conclusions:

In combination with the paediatric reference computational phantoms and the exposure models of cardiovascular intervention, the Monte Carlo method can be used to calculate the doses to children undergoing cardiovascular interventional radiological procedures. The information on the values of DAP and FOV as well as the directions of projection are needed for more accurate estimation of the exposure doses.