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Table 5 Uncertainty Analysis

From: Dose calibration of Gafchromic EBT3 film for Ir-192 brachytherapy source using 3D-printed PLA and ABS plastics

I. Uncertainty in Determining Dose from NOD

 

Low Dose

High Dose

Uncertainty Description

Type A (%)

Type B (%)

Type A (%)

Type B (%)

Scanning Consistency

0.1

 

0.1

 

Film uniformity

 

1.0

 

1.0

ROI Size

 

1.5

 

1.5

Calibration Curve Fit

 

4.8*

 

0.8*

Combined Uncertainty

0.1

5.1

0.1

2.0

Total Uncertainty

5.1

2.0

II. Uncertainty in Film Exposure

 

Low Dose

High Dose

Uncertainty Description

Type A (%)

Type B (%)

Type A (%)

Type B (%)

Repeatability

0.1

 

0.10

 

Distance to Source

 

4.0

 

4.0

Lack of Scatter Equilibrium

 

5.0

 

5.0

Source Strength

 

1.5

 

1.5

Exposure Time

 

0.8*

 

0.1*

Combined Uncertainty

0.1

6.6

0.10

6.6

 

6.6

6.6

III. Total Uncertainty

8.4

6.9

  1. *Indicates differences between high and low dose uncertainty
  2. Individual sources of uncertainty were determined for Dose from NOD Procedure (I) and consequential Film Exposure (II). Both random, statistical (Type A) and non-random, systematic (Type B) errors were determined. A root sum of squares is calculated to obtain combined, and total uncertainties