Three-dimensional ultrasound volume assessment of pediatric kidneys: comparison with conventional two-dimensional ultrasound

Abstract

Objective: To evaluate the accuracy of pediatric renal volume assessment using the freehand three-dimensional (3D) ultrasound (US) technique and to validate the reliability of this technique. Materials and methods: From December 2014 to March 2015, 17 children (7 boys and 10 girls

mean age, 8.71 years

range 1 to 17 years) who underwent both 3D ultrasonography and abdominal CT examinations within one week were included in our study. Freehand 3D renal US scanning was performed using the magnetic tracking system in a total of 31 normal kidneys. The 31 3D US datasets were measured twice per kidney by two different radiologists. Conventional two-dimensional (2D) renal volume was calculated by using the ellipsoid formula. For evaluation of accuracy, the reference renal volume (in milliliters) determined with CT was compared with those measured at 2D US and at 3D US datasets. Reliability of 3D US volume measurement was estimated by evaluating the intra-operator, interobserver and intraobserver agreements. Regarding the intra-operator agreement, the renal volume measurements of two 3D US scans of each kidney (available in 18 kidneys) by the same operator were compared. The interobserver agreement was assessed by comparing the measurements by the two observers for each kidney and the intraobserver agreement was evaluated using the two measurements per kidney by the same observer. Results: The 3D US volume assessment showed the smaller standard deviation of the difference and better correlation with the standard reference (CT volume assessment) than that of 2D US technique. The intra-operator agreement in 3D US acquisition (ICC = 0.993), interobserver agreement between two radiologists (ICC = 0.997) and intraobserver agreement between two datasets of two radiologists (ICC = 0.997, ICC = 0.998) were all excellent. Conclusion: Pediatric renal volume assessment using the freehand 3D US volume acquisition technique correlated better with CT volume assessment than the 2D volume assessment and showed excellent reliability in both US acquisition and measurement.