Advances in Conformal Radiotherapy. Using Monte Carlo Code to Design New IMRT and IORT
Accelerators and Interpret CT Numbers
The book presents studies the author worked on at the German National Cancer Institute
(DKFZ) in Heidelberg. These studies applied the Monte Carlo technique to investigate the
feasibility of performing Intensity Modulated Radiotherapy (IMRT) by scanning with a
narrow photon beam.
This approach represents an alternative to techniques that generate beam modulation by
absorption, such as MLC, individually-manufactured compensators, and special tomotherapy
modulators. The technical realization of this concept required investigation of the
influence of various design parameters on the final small photon beam. The photon beam to
be scanned should have a diameter of approximately 5 mm at Source Surface Distance (SSD)
distance, and the penumbra should be as small as possible.
We proposed a draft for this system based on the PRIMUS 6MV DKFZ accelerator and
investigated new geometry of the source-target-collimator system. We assessed the
influence of different collimator parameters, different target construction and various
incident electron beam characteristics. Based on this work, it was possible to define
adequate parameters for the target-collimator system and the scanning electron beam for
new a IMRT system. Examples of the intensity modulated field produced by the resulting
photon beam are shown.
Author’s Preface
1. Introduction and aim of the work
2. A new scanning photon beam system for IMRT
2.1 Intensity modulated radiotherapy (IMRT) techniques
2.1.1 Conventional MLC based IMRT technique .
2.1.2 An alternative way to do IMRT
2.2 Research objective
2.3 Monte Carlo (MC) study on a new concept of a scanning photon beam
2.3.1. Definition of requirements on the resulting photon beam
2.3.2. First draft for a target-collimator system
2.3.3 Influence of the collimator aperture
2.3.5 Influence of the incident electron beam characteristics
2.3.6 Influence of the geometry
2.4 Summary: conclusions and discussion
2.4.1 Simulated dose distribution of an intensity modulated field
2.4.2. Discussion
3 A new mobile electron accelerator treatment head for IORT
3.1 What is IORT?
3.2 Research objective
3.3 Monte Carlo study on a new model of a treatment head for a mobile electron accelerator
3.3.1. Radiation field and protection requirements
3.3.2. First draft for a foils-collimator-applicator system
3.3.3 Monte Carlo simulations
3.3.4 Dose distributions for the first draft of a foils-collimator-applicator system
3.3.5 Comparison of dose distribution for real and monoenergetic beams
3.3.6 Acceptable tolerance for displacement and rotation of applicator axis relative to
beam axis
3.3.7 Second draft for a foils-collimator-applicator system
3.4 Radiation protection studies for a new mobile IORT accelerator
3.4.1. Dose equivalent inside and outside operating room
3.4.2. Neutron DEQ
3.5 Summary: conclusions and discussion
4. A new approach to estimate the effect of CT calibration on range calculation
4.1 Treatment planning in Carbon ion therapy
4.1.1 Radiotherapy with heavy charged particles
4.1.2 CT in Carbon ion radiotherapy treatment planning
4.1.3 Image representation in CT-numbers (Hounsfield Units)
4.2 Research objective
4.3 Materials studied: CT scanner, substitutes and phantoms
4.3.1 Investigated CT scanner
4.3.2 Investigated substitutes and phantoms
4.4 MC simulation CT-numbers for a CT scanner and different phantom inserts
4.4.1 Simulation work flow
4.4.2 Optimization of parameters used in MC code.
4.4.4 Reconstructing CT-images from PHSP
4.4.5 CT-numbers of the various substitute materials
4.4.6 Accuracy of the simulated CT-numbers
4.5 Effect of X-ray voltage, phantom size and material on CT-numbers
4.5.1 Effect of filters on energy spectrum and fluence
4.5.2 Effect of voltage settings on energy spectrum , fluence and CT-numbers
4.5.3 Effect of substitute material on energy spectrum , fluence and CT-numbers
4.5.4 Effect of phantom size on CT-numbers .
4.5.5 Effect of phantom material on CT-numbers
4.6 Effect of X-ray voltage, phantom size and material on range calculation
4.6.1 CT calibration relation for ion therapy
4.6.2 Effect of CT calibration on range calculation
4.6.3 Effect of CT scanner and phantom parameters on range calculation in C-ion therapy
4.7 Summary: conclusions and discussion
References
List of Figures
Abbreviations
Appendix A
Appendix B 143
158 pages, Paperback
