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