Authors: Graham McInnis, Martin Reed MD FRCP(C), Idris Elbakri, Hayley Moffatt, Harry Ingleby
OBJECTIVE: Evaluate at what patient thickness anti-scatter grid usage becomes beneficial in children
undergoing voiding cystourethrography
METHODS: A water-based phantom was constructed with an adjustable insert to simulate three ureters
of different diameters which could be moved based on the depth of the water. The images were
acquired using a VCUG protocol. Multiple tank depths were used to simulate different patient
thicknesses with five images acquired at each depth with and without the grid in place. Images were
then randomized, and ureter visibility was assessed by two pediatric radiologists and two imaging
physicists. Images were scored on a four-point Likert scale. 1=Not visible, 2=Questionably visible,
3=Visible but indistinct, and 4=Visible and clear
RESULTS: Image quality scores were similar with both the anti-scatter grid in place and out. For the
maximum tank depth of 19.4cm, simulating a large pediatric patient, with the grid in place the four
readers gavethree scores of 2, thirteen scores of 3, and four scores of 4. With the grid removed the
scores were not substantially different with three scores of 2, ten scoresof 3, and seven scores of 4.
Formal measures of interreader reliability were not possible due to high agreement between readers.
CONCLUSIONS: Image quality did not differ substantially between images acquired with the anti-scatter
grid in place and with it removed. These results suggest that for most pediatric patients an anti-scatter
grid does not enhance ureter visibility and grid removal should be considered as a dosage saving
mechanism for VCUGs.

An investigation of the effects of anti-scatter grid usage on ureter visibility in pediatric voiding cystourethrography as a function of patient size