ADDED COPPER FILTRATION IN DIGITAL PEDIATRIC DOUBLE-CONTRAST COLON EXAMINATIONS - EFFECTS ON RADIATION-DOSE AND IMAGE QUALITY

Paediatric double-contrast barium enema examinations are usually perfo rmed at high tube voltage, 102-105 kV. The aim of this study was to in vestigate how much the effective dose to the child could be reduced by increasing the X-ray energy further by adding copper filter in the be am, and if this dose reduction could be achieved without endangering i mage quality. Organ doses to an anthropomorphic phantom simulating a 1 -year-old child was measured using thermoluminescence dosimetry for as sessment of the effective dose and this value was compared with the en ergy imparted which was obtained from kerma-area product measurements. To verify that the image quality achieved with this added filtration was still diagnostically acceptable, the study included 15 patient exa minations. Since the increased X-ray energy will most probably affect low-contrast objects, image quality was also evaluated with two differ ent phantoms containing low-contrast objects. Effective dose for a com plete examination can be decreased 44 % and energy imparted 77 % when a 0.3-mm cop,per filter is inserted in the beam at tube voltage 102 kV . The patient study did not show any significant deterioration of imag e quality, whereas phantom mea surements of contrast-detail resolution and signal-to-noise ratio was marginally impaired by the added copper filtration. This technique is now in clinical practice for paediatric colon examinations.