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NOVEL SOFTWARE MODULES FOR
TREATMENT PLANNING OF 106RU EYE
PLAQUE BRACHYTHERAPY
Gerd Heilemann, Lukas Fetty, Matthias Blaickner, Nicole Nesvacil, R.
Dunavölgyi, and Dietmar Georg
ESTRO 35 Forum 29 April - 03 May 2016, Turin
Treatment planning aspectsESTRO 35 29 April – 03 May 2016, Turin2
BEBIG Plaque Simulator
106Ru treatment planning:
Good local control, rel. low morbidity
Current practice in planning:
BEBIG eyephysics (Mac only)
1D – depth dose based
Shortcomings/limitations -> motivated development of software modules
Goal: in-house software tool for treatment planning
(+ tool for pro- /retrospective studies)
The 3D eye and tumor modelESTRO 35 29 April – 03 May 2016, Turin3
Houdini, SideFX (Toronto, Canada)
Tumor model
Dome shaped tumor
Apex 3-8 mm
Basal diameters 5-20 mm
Eye model
Anatomical model, adjustable tumor location
OARs
lens, ciliary body, optic nerve, macula as well as the retina and sclera
Tumor location
Distance to opt. nerve/macula
The 3D eye and tumor modelESTRO 35 29 April – 03 May 2016, Turin4
Houdini, SideFX (Toronto, Canada)
Tumor model
Dome shaped tumor
Apex 3-8 mm
Basal diameters 5-20 mm
Eye model
Anatomical model, adjustable tumor location
OARs
lens, ciliary body, optic nerve, macula as well as the retina and sclera
Tumor location
Distance to opt. nerve/macula
The 3D eye and tumor modelESTRO 35 29 April – 03 May 2016, Turin5
Houdini, SideFX (Toronto, Canada)
Tumor model
Dome shaped tumor
Apex 3-8 mm
Basal diameters 5-20 mm
Eye model
Anatomical model, adjustable tumor location
OARs
lens, ciliary body, optic nerve, macula as well as the retina and sclera
Tumor location
Distance to opt. nerve/macula
Dose calculation & uncertaintyESTRO 35 29 April – 03 May 2016, Turin6
Benchmark
MCNP6
Film dosimetry (diode, µ-Diamond)
Manufacturer
Uncertainties/Robustness
MC dose calculation
Eye model voxelization
imperfect positioning of plaque
Treatment plan optimizationESTRO 35 29 April – 03 May 2016, Turin7
A. Switching from larger plaque
to smaller plaque type
B. Shifting plaque on relatively
small tumors away from the
critical structures
(for different tumor locations)
RobustnessESTRO 35 29 April – 03 May 2016, Turin8
Naturally larger tumors induce larger dose change
Ant: lens
Post: opt. nerve & macula
Cent: similar effect on lens and opt. nerve + retina mean dose
Examples:
20 Gy
6 Gy
104 Gy
34 Gy
Central position, 3mm apex
Central position, 8mm apex
Plan optimization Pt. 1ESTRO 35 29 April – 03 May 2016, Turin9
Objective: Tumor coverage must
not be compromised!
Threshold base diameters (w.r.t.
positional accuracy)
Example:
OAR
name
Apex
(mm)
Dose reduction (in Gy)
D2% Dmean
ant cent post ant cent post
Lens
3 32.3 9.0 1.2 11.4 2.0 0.2
5 47.9 14.1 1.9 17.5 3.1 0.3
8 124.7 41.2 5.8 49.3 9.2 0.9
Optic
nerve
3 0.0 2.2 14.2 0.0 0.7 3.2
5 0.1 3.5 19.4 0.0 1.2 4.2
8 0.2 10.6 38.3 0.0 3.6 7.3
Retina
3 35.8 6.0 7.0 7.3 11.9 20.5
5 35.5 -15.9 -14.5 10.8 17.1 30.4
8 -11.3 -205.6 -201.9 28.0 40.0 77.3
Type Shift Maximum base diameter
CCA
0 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 10 𝑚𝑚+ 0.57 ∗ A𝑎𝑝𝑒𝑥
1 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 6.5 𝑚𝑚 + A𝑎𝑝𝑒𝑥
2 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 3.5 𝑚𝑚 + A𝑎𝑝𝑒𝑥
CCB
0 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 13.4 𝑚𝑚+ 0.75 ∗ A𝑎𝑝𝑒𝑥
1 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 12 𝑚𝑚+ 0.86 ∗ A𝑎𝑝𝑒𝑥
2 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 13 𝑚𝑚+ 0.57 ∗ A𝑎𝑝𝑒𝑥
(apex 5mm with CCA)
Max. base diameter for
different shifts:• 1 mm : 11.5 mm
• 0 mm : 12.9 mm
Max dose reduction:
• Lens (D2%): 124.7 Gy
• Optic (D2%): 38.3 Gy
• Retina (Dmean): 77.3 Gy
1 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 6.5 𝑚𝑚 + A𝑎𝑝𝑒𝑥2 mm 𝐷𝑏𝑎𝑠𝑎𝑙 ≤ 3.5 𝑚𝑚 + A𝑎𝑝𝑒𝑥
32.3
47.9
125.7
14.2
19.4
38.3 20.5
30.4
77.3
Plan optimization Pt. 2 ESTRO 35 29 April – 03 May 2016, Turin10
Linear fits to express dose
change ΔD with respect to
introduced shifts Δs:
Example:
𝐺 = ∆ Τ𝐷 ∆ 𝑠
Apex height OAR
Dose change per shift (Gy/mm)
anterior middle posterior
3mm lens 6.24 0.7 0.0
D25mm lens 11.3 1.2 0.1
8mm lens 42.1 4.6 0.3
3mmmakula 0.0 0.4 4.9
D2
optic nerve 0.0 0.4 7.5
5mmmakula 0.0 0.6 8.8
optic nerve 0.0 0.8 13.5
8mmmakula 0.0 2.4 32.8
optic nerve 0.0 3.0 50.2
3mm retina 1.0 1.2 0.5
mean5mm retina 1.9 2.1 0.9
8mm retina 6.9 8.0 3.5
5mm apex, 6 mm diameter,
anterior tumor with CCA,
shift away from lens by 3 mm
Dose change: • Reduce Dmax lens: > 33 Gy
• Increase Dmax opt. nerve < 0.5 Gy
11.3 Gy/mm
0.004 Gy/mm
ConclusionESTRO 35 29 April – 03 May 2016, Turin11
Novel software modules for 3D treatment planning of 106Ru eye plaque brachytherapy of uveal melanomas.
Application:
daily treatment planning
research on plan optimization
performing pro- and retrospective studies
provide further information on dose-response relationships
prognostic values for treatment morbidity and local control.
Future works involves the registration of pre- or post-application MR images as well as a quantitative evaluation on the basis of retrospective data.
12
Thank you for your attention!
Supported by the Austrian Science Fund (FWF), project P25936