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Experimental validation of Monte Carlo based treatment planning system in bone density equivalent media

Djeni Smilovic Radojcic
Djeni Smilovic Radojcic
, 
Bozidar Casar
Bozidar Casar
, 
David Rajlic
David Rajlic
, 
Manda Svabic Kolacio
Manda Svabic Kolacio
, 
Ignasi Mendez
Ignasi Mendez
, 
Nevena Obajdin
Nevena Obajdin
, 
Dea Dundara Debeljuh
Dea Dundara Debeljuh
 and 
Slaven Jurkovic
Slaven Jurkovic
   | Sep 16, 2020
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Article Category: Research Article
Published Online: Sep 16, 2020
Page range: 495 - 504
Received: Jun 10, 2020
Accepted: Jul 09, 2020
DOI: https://doi.org/10.2478/raon-2020-0051
© 2020 Djeni Smilovic Radojcic, Bozidar Casar, David Rajlic, Manda Svabic Kolacio, Ignasi Mendez, Nevena Obajdin, Dea Dundara Debeljuh, Slaven Jurkovic, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

Photo of the semi-anthropomorphic CIRS Thorax phantom with interchangeable rod inserts (left) and its CT image (right). Positions of 10 interchangeable rod inserts are marked with numbers from 1 to 10. Five measuring points are in the water equivalent part of the phantom (grey area), four points are in the lung density equivalent material (black area), and one point is in the bone density equivalent part of the phantom (white area).
Photo of the semi-anthropomorphic CIRS Thorax phantom with interchangeable rod inserts (left) and its CT image (right). Positions of 10 interchangeable rod inserts are marked with numbers from 1 to 10. Five measuring points are in the water equivalent part of the phantom (grey area), four points are in the lung density equivalent material (black area), and one point is in the bone density equivalent part of the phantom (white area).

Figure 2

CT image of the CIRS Thorax phantom: water equivalent insert inside BDE part of the phantom (A); a BDE insert inside bone density equivalent (BDE) part of the phantom (B) and cross-section of small “water cylinders” of different dimensions delineated inside BDE part of the phantom to find limits for calculating geometry where cavity theory applies (top right).
CT image of the CIRS Thorax phantom: water equivalent insert inside BDE part of the phantom (A); a BDE insert inside bone density equivalent (BDE) part of the phantom (B) and cross-section of small “water cylinders” of different dimensions delineated inside BDE part of the phantom to find limits for calculating geometry where cavity theory applies (top right).

Figure 3

Mean percentage dose differences δD¯m${{\overline{\delta D}}_{m}}$and δD¯w${{\overline{\delta D}}_{w}}$between calculated and measured doses in different parts of the CIRS Thorax phantom (water, lung, and bone density equivalent materials) for both calculation options built in the Monaco TPS: dose-to-medium Dm and dose-to-water Dw. Error bars represent corresponding combined uncertainties.
Mean percentage dose differences δD¯m${{\overline{\delta D}}_{m}}$and δD¯w${{\overline{\delta D}}_{w}}$between calculated and measured doses in different parts of the CIRS Thorax phantom (water, lung, and bone density equivalent materials) for both calculation options built in the Monaco TPS: dose-to-medium Dm and dose-to-water Dw. Error bars represent corresponding combined uncertainties.

Figure 4

Average differences δD¯m${{\overline{\delta D}}_{m}}$and δD¯w${{\overline{\delta D}}_{w}}$between calculated and measured doses in the bone density equivalent (BDE) part of the CIRS Thorax phantom, as a function of the volumes of the simulated “water cylinders” (see Figure 2 and Table 3). δD¯m${{\overline{\delta D}}_{m}}$and δD¯w${{\overline{\delta D}}_{w}}$are presented as individual values/points calculated using Eqs. [1] to[4], and in the form of two analytical functions from Eqs. [9] and [10]. Error bars represent corresponding uncertainties within 95% confidence limits.
Average differences δD¯m${{\overline{\delta D}}_{m}}$and δD¯w${{\overline{\delta D}}_{w}}$between calculated and measured doses in the bone density equivalent (BDE) part of the CIRS Thorax phantom, as a function of the volumes of the simulated “water cylinders” (see Figure 2 and Table 3). δD¯m${{\overline{\delta D}}_{m}}$and δD¯w${{\overline{\delta D}}_{w}}$are presented as individual values/points calculated using Eqs. [1] to[4], and in the form of two analytical functions from Eqs. [9] and [10]. Error bars represent corresponding uncertainties within 95% confidence limits.

Differences δDm$\delta {{D}.{m}}$and δDw$\delta {{D}.{w}}$between two different calculation options in the Monaco ver. 5.11. treatment planning systems (TPS) and measured data obtained in the bone density equivalent (BDE) part of the CIRS Thorax phantom, according to Eqs. [1] and [2]. Two phantom assemblies and three simple beam setups were considered for this part of the study

Irradiation geometry (field, gantry)Phantom assemblyδDm[%]$\delta {{D}_{m}}\left[ \text{%} \right]$δDw[%]$\delta {{D}_{w}}\left[ \text{%} \right]$
(6+8) x 15 cm2Gantry = 0°standard

BDE insert with the ionization chamber placed in the BDE part of the phantom

- 2.92.9
non-standard

Water equivalent insert with the ionization chamber placed in the BDE part of the phantom

- 0.7- 0.2
(3+8) x 15 cm2Gantry = 90°standard

BDE insert with the ionization chamber placed in the BDE part of the phantom

- 3.05.1
non-standard

Water equivalent insert with the ionization chamber placed in the BDE part of the phantom

- 0.7- 0.1
(4+10) x 15 cm2Gantry = 180°standard

BDE insert with the ionization chamber placed in the BDE part of the phantom

- 5.75.4
non-standard

Water equivalent insert with the ionization chamber placed in the BDE part of the phantom

0.51.3

Mean differences, δD¯m${{\overline{\delta D}}.{m}}$and δD¯w${{\overline{\delta D}}.{w}}$between calculated and measured doses in the bone density equivalent (BDE) part of the CIRS Thorax phantom for Dm and Dw calculation approaches, respectively. The absorbed doses were calculated using the Monaco ver. 5.11 treatment planning systems (TPS) in the center of delineated “water cylinders” of volume V, in the BDE part of the phantom. Corresponding combined uncertainties are denoted as uc,m and uc,w for dose-to-medium and dose-to-water calculation options, respectively

V [cm3]δD¯m${{\overline{\delta D}}_{m}}$[%]uc,m[%]δD¯w${{\overline{\delta D}}_{w}}$[%]uc,w[%]
0- 3.92.14.41.9
0.035- 2.61.52.51.9
0.141- 1.41.31.81.7
0.279- 0.31.21.21.5
0.5730.31.40.41.3

Irradiation set-ups for measurements in 6 MV photon beam used for experimental verification of the Monaco ver. 5.11 treatment planning systems (TPS) calculation algorithm in the semi-anthropomorphic CIRS Thorax phantom. Reference and measuring points (I1 to I10) are shown in the last two columns; subscripts 1 to 10 correspond to the labelling in Figure 1

Set-upIrradiation geometryField size [cm2]SSD/SADGantry angle [°]reference pointmeasuring points
1Single square fields10×10SSD0I5I1, I3, I5-10
210×10SAD0I5I, I, I135-10
34×4SAD0I5I1-9
410×10SAD90I3I2-10
5Rectangular field10× 15SAD300I1I1, I4, I6-8, I10
6Single asymmetric fields(6+8)×15SAD0I5I1-10
7(3+8)×15SAD90I5I, I15-10
8(4+10)×15SAD180I5I1-3, I5-10
9(3+7)×15SAD300I5I2-10
12×10SAD0
104 fields (box)12×10SAD180I5I2-5
12×8SAD90
12×8SAD270
4×4SAD30
113 fields16×4SAD90I5I2, I5-9
16×4SAD270
12Diamond-shaped field14×14SAD0I3I1, I3, I5-10
13Irregular L shaped field/SAD45I1I1-2, I4-6, I8-10
14MLC cylinder shaped field/SAD0I2I1,2, I5, I8,9, I10
16×4SAD90
153 non-coplanar fields16×4SAD270I5I1, I5-6, I8, I10
4×4

Couch angle = 270°

SAD30
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