Lt Breast Case Close proximity to OARs Large Target volume - - PowerPoint PPT Presentation

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Lt Breast Case Close proximity to OARs Large Target volume - - PowerPoint PPT Presentation

Dec 04, 2023 385 likes •652 views

Mamta Mahur , M.Sc Physics, DRP Medical Physicist Delhi State Cancer Institute, Delhi, India . Lt Breast Case Close proximity to OARs Large Target volume Peripheral target closer to skin Inhomogeneity involved Criteria to

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Mamta Mahur, M.Sc Physics, DRP

Medical Physicist Delhi State Cancer Institute, Delhi, India.

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Lt Breast Case

  • Close proximity to OARs
  • Large Target volume
  • Peripheral target closer to skin
  • Inhomogeneity involved

Criteria to achieve for

  • 1. PTV_TOT_EVAL
  • 2. Heart
  • 3. Left Lung
  • 4. Right Lung
  • 5. Right Breast
  • 6. Spinal Cord
  • 7. Homogeneity index
  • 8. Conformation number
  • 9. Global maximum dose location
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Equipment and method used

  • ONCOR expression Linear Accelerator (Siemens AG,

Germany)

  • OPTIFOCUSTM Multileaf collimator with 41 leaf pairs
  • Leaf size 1cm (outer leaf pair 0.5cm)
  • 6MV Photon Energy
  • Step and Shoot IMRT Technique
  • Monaco TPS version 5.10.02 from IMPAC Medical

Systems, Elekta, USA.

  • Algorithm used – Monte Carlo
  • Nine coplanar beams
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Creating Plan in Monaco TPS

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Beam 1 Gantry angle 285 ̊ Collimator angle 10 ̊ Beam 2 Gantry angle 305̊ Collimator angle 15̊ Beam 3 Gantry angle 325̊ Collimator angle 0̊

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Beam 4 Gantry angle 110 ̊ Collimator angle 350 Beam 5 Gantry angle 150 ̊ Collimator angle 340 ̊ Beam 6 Gantry angle 130 ̊ Collimator angle 340 ̊

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Beam 7 Gantry angle 345 ̊ Collimator angle 0 Beam 8 Gantry angle 90 ̊ Collimator angle 350 ̊ Beam 9 Gantry angle 40 ̊ Collimator angle 0 ̊

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Dose Prescription

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Define Calculation properties Define sequencing parameters

Plan Parameters

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Optimization Process

  • Two stage process

– Phase I: beamlet weights are optimized using the PB Algorithm. – Phase II: segment weights are optimized using MC Algorithm.

  • Layering of structures/OARS (Monaco uses layering order to

determine voxel ownership )

  • Heart, Left Lung, Right Breast, Spinal cord, Right Lung defined

all above the body but below target

  • Define objectives for target and constraint for OARs
  • Start optimization with PTV and Body first
  • Add OARs constraint one by one in optimization
  • Analyze the results of optimization using relative impact tab

as well as dose statistics.

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Optimization constraints

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In PTV Structure optimization properties use Auto Flash Margin

Target Objectives

IMRT Parameters

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Target EUD Biological cost function Physical cost function Quadratic Overdose

Target Objectives

One more physical cost function used Target penalty (to force the min.

dose coverage)

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Define cost functions for body

  • First quadratic overdose function
  • Second quadratic overdose function
  • Maximum dose cost function
  • Conformality cost function

To limit spillage

  • f dose
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Constraints defined for heart

Biological cost function used – Parallel cost function

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Constraints defined for Left Lung

Biological cost function used – Parallel cost function

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Constraints defined for Right Breast

Biological cost function used – Parallel and Serial cost function

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Constraints defined for Spinal Cord

Biological cost function used – Serial cost function

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Constraints defined for Right LUNG

Biological cost function used – Parallel cost function

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Dose Statistics from TPS

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Plan report

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Results Summary

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47.845 49.089 51.216 54.935 3.991 5.93 19.118 1.49 2.233 7.816 1.38 10.899 18.35 28.8 52.76 Monaco results vary from Sun Nuclear Score

Monaco TPS result Sun Nuclear result

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