Dose Course 2018_Flipping book

Uncertainty in entrance dose measurements

18 MV X-rays

Physical quantity of procedure

Relative standard uncertainty (%)

TLD Ans Swinen PhD thesis 2005

1.7% 1.0% 0.5%

TLD calibration with IC

TLD reading of “unknown detector”

Non-lineality

Fading

<0.5%

Combined standard uncertainty of step 1

2.1%

Step 2: Correction factors Field correction factor

1.5% 1.5% 2.1%

SSD correction factor

Combined standard uncertainty of step 2

Step 3: measure on the patient Reading of the in vivo detector 1

1.2% 1.2%

Combined standard uncertainty of step 3

Combined standard uncertainty of steps 1+2+3

3.2%

1 reproducibility on positioning on patients was not tested.