Assessment of optical localizer accuracy for computer aided surgery systems

Figures & data

Figure 1. Setup of the camera systems on the CMM.

Figure 2. The seven test lengths for the evaluation of the Length Measurement Error.

Figure 3. Configurations of the four pointers and two reference frames used to estimate clinical accuracy.

Figure 4. Static measurements: chronological sequence (hh:mm:ss) of 3D error (mm).

Table I.  Results of the relative static measurements. Warm-up time was defined as the time after which no value differed by more than 0.1 mm from the mean value for the final 30 min of the measurement period.

Camera	Max. 3D error (mm)	Warm-up time (h : min)
Polaris P4	0.610	0 : 42
Spectra passive	0.157	0 : 01
Spectra active	0.198	0 : 01
Stryker	0.107	0 : 01

Figure 5. Volumetric single marker measurements: volumetric distribution of trueness throughout the measurement volume.

Figure 6. Error distribution of single marker volumetric measurements.

Table II.  Results of the volumetric single marker measurement.

		Precision (mm)
Camera	Trueness (mm)	x	y	z	RMS (mm)	95% CI (mm)	99% CI (mm)	Max. error (mm)
Polaris P4	0.272 ± 0.394	0.009	0.012	0.042	0.478	0.862	2.222	4.035
Polaris Spectra passive	0.170 ± 0.090	0.008	0.006	0.028	0.192	0.349	0.417	0.759
Polaris Spectra active	0.089 ± 0.061	0.009	0.005	0.025	0.108	0.182	0.285	1.528
Stryker	0.058 ± 0.033	0.002	0.002	0.007	0.067	0.152	0.204	0.217

Figure 7. Length Measurement Error: LME diagram (upper portion of each quarter) and histogram of LMEs.

Table III.  Results of the Length Measurement Error evaluation.

Camera	LME (mm)	LME max. (mm)
Polaris P4	0.146 ± 0.181	0.917
Polaris Spectra passive	0.133 ± 0.141	0.514
Polaris Spectra active	0.067 ± 0.070	0.324
Stryker	0.051 ± 0.036	0.142

Figure 8. Volumetric tool measurements: volumetric distribution of trueness throughout the measurement volume.

Table IV.  Results of the volumetric tool measurements: translation.

		Precision (mm)
Camera	Trueness (mm)	x	y	z	RMS (mm)	95% CI (mm)	99% CI (mm)	Max. error (mm)
Polaris P4	0.214 ± 0.316	0.007	0.010	0.042	0.381	0.724	2.523	2.916
Polaris Spectra passive	0.132 ± 0.098	0.007	0.004	0.028	0.165	0.271	0.513	1.214
Polaris Spectra active	0.087 ± 0.057	0.007	0.004	0.022	0.104	0.185	0.270	0.864
Stryker	0.070 ± 0.032	0.002	0.002	0.005	0.077	0.134	0.162	0.191

Table V.  Results of the volumetric tool measurements: rotation.

Camera	Precision (°)	95% CI (°)	99% CI (°)	Max. error (°)
Polaris P4	0.146	0.551	2.181	3.400
Polaris Spectra passive	0.019	0.237	0.515	1.305
Polaris Spectra active	0.013	0.156	0.399	1.199
Stryker	0.005	0.104	0.128	0.166

Figure 9. Estimation of the clinical accuracy of different tool/reference configurations for a tool-tip distance of 1 to 400 mm from the center of gravity of the reference frame.