Table 3.

Linear measurement accuracy and precision in QT speed of sound imaging. Note that the bias values represent the measurement accuracy calculated as difference between actual values (measured by calipers) and the value measured by QT, and the percentage bias values are calculated as percentage ratio of bias and actual values. The ‘Measurement #’ column identifies the numbered measurements in Figure 8.

Imaging Plane	Measurement #	Measured by Calipers (mm)	Measured QT (mm ± s.d.) (n=3)	% s.d. (coefficient of variation) (n=3)	Bias (mm)	% Bias
Coronal	1	5.00	5.00 ± 0.17	3.46	0.00	0.00
	2	10.00	10.07 ± 0.06	0.57	+ 0.07	0.66
	3	20.00	20.53 ± 0.75	3.66	+ 0.53	2.63
	4	75.60	76.50 ± 0.26	0.35	+ 0.90	1.18
	5	76.10	76.77 ± 0.50	0.66	+ 0.67	0.87
	6	119.70	119.23 ± 0.40	0.34	− 0.47	0.39
			Mean Coefficient of Variation = 1.51		Mean % Difference: = 0.96
Axial	1	5.00	5.13 ± 0.06	1.12	+ 0.13	2.63
	2	10.00	10.10 ± 0.40	3.96	+ 0.10	1.00
	3	20.00	19.87 ± 0.42	2.10	− 0.13	0.67
	4	60.10	60.00 ± 0.66	1.09	− 0.10	0.17
	5	60.10	59.53 ± 0.21	0.35	− 0.57	0.95
	6	76.50	75.23 ± 0.40	0.54	− 1.27	1.67
			Mean Coefficient of Variation = 1.53		Mean % Difference: = 1.18
Sagittal	1	5.00	5.17 ± 0.06	1.12	+ 0.17	3.28
	2	10.00	10.07 ± 0.06	0.57	+ 0.07	0.66
	3	20.00	20.10 ± 0.10	0.50	+ 0.10	0.50
	4	60.10	59.20 ± 0.20	0.34	− 0.90	1.51
	5	60.10	59.47 ± 0.32	0.54	− 0.63	1.06
	6	76.50	76.33 ± 0.65	0.85	− 0.17	0.22
			Mean Coefficient of Variation = 0.65		Mean % Difference: = 1.20