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Table 2 Systematic and random error of 3DUS, CTV to PTV margin

From: A comparative assessment of prostate positioning guided by three-dimensional ultrasound and cone beam CT

  

Lateral mm (95% CI)

Longitudinal mm (95% CI)

Vertical mm (95% CI)

Systematic errors

   
 

3DUS

1.3 (0.8-3.3)

0.8 (0.5-2.1)

1.4 (0.9-3.6)

 

CBCT (bone-match)

1.3 (0.8-3.1)

1.9 (1.2-4.6)

1.8 (1.4-5.4)

 

Skin marks

1.6 (0.9-3.6)

2.2 (1.1-4.4)

2.3 (1.4-5.7)

Random errors

 

3DUS

2.5 (0.0-3.8)

2.3 (0.0-3.5)

2.7 (0.0-4.4)

 

CBCT (bone-match)

0.7 (0.0-1.3)

2.0 (0.0-3.6)

2.7 (0.0-4.8)

 

Skin marks

2.2 (0.0-3.8)

2.9 (0.0-4.7)

3.9 (0.0-5.7)

Resulting optimal margins

 

3DUS

5.1 (2.1-10.9)

3.7 (1.3-7.6)

5.5 (2.3-11.9)

 

CBCT (bone-match)

3.7 (2.0-8.7)

6.1 (2.9-14.0)

6.3 (2.8-14.3)

 

Skin marks

5.5 (2.4-12.2)

7.5 (3.4-16.8)

8.5 (3.6-18.1)

  1. In units of mm; the systematic error is defined as the standard deviation of all individual mean errors; the random error is defined as the root of the average of all individual variances; the optimal margin is defined as 2.5 times the systematic error plus 0.7 times the random error.
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Radiation Oncology

ISSN: 1748-717X

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