Open Access

Does CyberKnife improve dose distribution versus IMRT and VMAT on a linear accelerator in low-risk prostate cancer?

Dorota Maria Borowicz
Dorota Maria Borowicz
, 
Agnieszka Skrobała
Agnieszka Skrobała
, 
Marta Kruszyna-Mochalska
Marta Kruszyna-Mochalska
 and 
Julian Malicki
Julian Malicki
   | Mar 28, 2022
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Article Category: Research Article
Published Online: Mar 28, 2022
Page range: 259 - 266
Received: Oct 21, 2021
Accepted: Jan 31, 2022
DOI: https://doi.org/10.2478/raon-2022-0010
© 2022 Dorota Maria Borowicz, Agnieszka Skrobała, Marta Kruszyna-Mochalska, Julian Malicki, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Example dose distributions on a transversal scan for (A) IMRT plan, (B) VMAT plan and (C) CyberKnife plan for the same patient.
Example dose distributions on a transversal scan for (A) IMRT plan, (B) VMAT plan and (C) CyberKnife plan for the same patient.

Figure 2

Gamma index for verification plans.
Gamma index for verification plans.

Figure 3

IMRT gamma index (2%/2mm) values for each patient.
IMRT gamma index (2%/2mm) values for each patient.

Figure 4

Gamma Index for IMRT for each treatment beam and all plans.
Gamma Index for IMRT for each treatment beam and all plans.

Mean conformity and homogeneity index values

VMAT IMRT CyberKnife p
CI 1.17 ± 0.04 1.25 ± 0.07 1.07 ± 0.03 p < 0.001
HI 1.07 ± 0.01 1.04 ± 0.01 1.25 ± 0.03 p < 0.001

Treatment plan acceptance criteria

Structure Criteria
PTV: IMRT and VMAT DMax:107% of the prescribed dose
DMin: 95% of the prescribed dose
Prescribed isodose: 78%–82%
PTV: Cyber Knife Total dose of prescribed isodose covering at least 95% of PTV volume
V18 Gy < 50% Vol
V29 Gy < 20% Vol
Rectum V32.6 Gy < 10% Vol
V36.25 Gy < 5% Vol
V36 Gy < 1 mm3
V18 Gy < 55% Vol
V29 Gy < 25% Vol
Bladder V32.6 Gy < 15% Vol
V36.25 Gy < 10% Vol
V37 Gy < 10 mm3
Femoral heads: left and right V25 Gy < 45% Vol

Dosimetric parameters for VMAT, IMRT and CyberKnife

VMAT IMRT CyberKnife p
D mean PTVMean ± SD 36.25 36.25 39.59±1.11 -
D min PTVMean ± SD 34.6±0.41 34.67±0.52 31.48±0.99 p < 0.001
D max PTVMean ± SD 38.76±0.47 37.57±0.4 45.89±0.94 p < 0.001
Target coverage D98%Mean ± SD 97.36±1.02 99.25±0.75 96.08±0.76 p < 0.001

Mean dosimetric parameters for the three techniques

VMAT IMRT CyberKnife p
Rectum
V18 Gy [%] 15.33 ± 2.97 15.17 ± 2.79 22.58 ± 6.6 p < 0.001
V29 Gy [%] 7.13 ± 2 7.25 ± 1.89 7.18 ± 2.82 p < 0.911

p values > 0.05 were considered non-significant
V32.6 Gy [%] 4.75 ± 1.51 4.82 ± 1.58 3.23 ± 1.66 p < 0.001
V36.25 Gy [%] 0.54 ± 0.29 0.32 ± 0.25 0.24 ± 0.25 p < 0.001
V36 Gy in mm3 591.59 ± 226.53 422.62 ± 236.64 219.78 ± 235.02 p < 0.001
Bladder
V18 Gy [%] 11.98 ± 5.33 14.93 ± 5.56 19.25 ± 8.62 p < 0.001
V29 Gy [%] 5.87 ± 2.32 8 ± 2.73 7.35 ± 3.27 p < 0.001
V32.6 Gy [%] 4.38 ± 1.72 5.7 ± 2.08 4.71 ± 2.14 p < 0.001
V36.25 Gy [%] 2 ± 0.93 1.22 ± 0.81 2.16 ± 1.09 p < 0.001
V37 Gy in mm3 1090.75 ± 610.81 4.5 ± 15.7 3256 ± 1518.84 p < 0.001
Left femoral head V25 Gy 0 0.12 ± 0.25 0 < p 0.001
Right femoral head V25 Gy 0 0.12 ± 0.3 0 < p 0.001
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