A systematic approach to statistical analysis in dosimetry and patient-specific IMRT plan verification measurements

Table 2 Patient specific IMRT QA absolute dose measurement analysis

Meas. num (n)	Measurement result (Gy)	Mean value (1 to n)	Result standard deviation (1 to n)	Estimated dose delivery standard deviation	Probability for the mean to be within 3% accuracy (1 to n)	Probability for the mean to be within 5% accuracy (1 to n)
a. Chamber 1: corresponding plan dose was 1.702 Gy
1	1.689	1.689	-		-	-
2	1.706	1.698	0.012	0.015	89.62%	93.73%
3	1.550	1.648	0.086	0.097	57.74%	76.25%
4	1.700	1.661	0.075	0.081	72.60%	88.76%
5	1.678	1.665	0.065	0.069	83.87%	95.41%
b. Chamber 2: corresponding plan dose was 0.546 Gy
1	0.502	0.502	-		-	-
2	0.466	0.484	0.025	0.032	43.55%	59.61%
3	0.457	0.475	0.024	0.027	59.52%	77.70%
4	0.465	0.473	0.020	0.022	75.01%	90.16%
5	0.453	0.469	0.019	0.021	82.01%	94.62%

The measurements were conducted with the QA phantom re-setup and re-aligned between each measurement and the statistical analysis was for the accuracy of measurement itself. The accuracy is defined as percent difference between the expected value and measurement mean value.

ISSN: 1748-717X