Assessment of micro-dose biplanar radiography in lower limb measurements in children

Objectives To evaluate in children microdose protocol compared with low dose for lower limb alignment (LLA) measurements on biplanar radiography. Methods Children 6 years or older were included. Height, weight and hip width were measured prior to imaging. Hip width allowed classifying children into morphotype M1 (width <25 cm), M2 (25–35 cm) or M3 (>35 cm) corresponding to predefined acquisition parameters (kV, mA, tube speed). Micro- and low-dose protocols were used alternately, with simultaneous acquisition of frontal and lateral radiographs. LLA measurements were performed by two independent observers (n = 526). In 15 children per morphotype, a third observer performed measurements twice (n = 180). Intraclass correlation coefficients and the dose (delivered, absorbed) were calculated. Results 100 girls and 160 boys (mean age = 11.7 years) were investigated: 74 M1 (mean BMI, 15.7kg/m 2 ), 149 M2 (19.8 kg/m 2 ) and 40 M3 (30.2 kg/m 2 ). With microdose, inter- and intra-observer agreement was >0.90 for lengths whatever the morphotype, 0.75–0.90 (M1) and >0.90 (M2, M3) for valgus/varus and flexion/hyperextension deviations. Dose reduction reached a factor of 8.5 and 5.4 for the delivered and absorbed dose respectively. Conclusions Microdose could be used for LLA measurements in children and permits a significant dose reduction. Key points • Lower limb lengths of children can be evaluated with microdose biplanar radiography. • Valgus/varus deviations also can be evaluated with microdose biplanar radiography. • Microdose biplanar radiography significantly reduces delivered and absorbed dose in children.