Monte Carlo Techniques in radiation therapy - mcneg
Monte Carlo Techniques in radiation therapy - mcneg
Monte Carlo Techniques in radiation therapy - mcneg
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<strong>Monte</strong> <strong>Carlo</strong> <strong>Techniques</strong><br />
<strong>in</strong> <strong>radiation</strong> <strong>therapy</strong><br />
Henry Lawrence<br />
Ipswich Hospital
History of M/C<br />
<br />
Calculate π us<strong>in</strong>g method of Buffon and Laplace<br />
Throw a stick of length L onto a surface ruled with parallel<br />
l<strong>in</strong>es d apart.<br />
Buffon (1777) suggested that the probability of the stick cross<strong>in</strong>g the l<strong>in</strong>e<br />
p=2L/(π *d)<br />
Laplace (1886) suggested calculate π.<br />
Lawrence (2013) gave it a go, and got to<br />
~ 2 % after 3000 ‘throws’
Development of EGS/MCNP<br />
1949 von Neumann and Ulam<br />
1960 Etran and ITS<br />
1978 EGS3<br />
Step size artifacts <strong>in</strong> e- transport<br />
1985 EGS4<br />
PRESTA (Bielajew) solved step size problem<br />
2000 EGSnrc
Splitt<strong>in</strong>g<br />
Variance reduction<br />
– Uniform,dir. brems…<br />
Russian Roulette<br />
Range rejection<br />
Interaction forc<strong>in</strong>g
Dosimetry applications<br />
Stopp<strong>in</strong>g power ratios<br />
– Calculate fluence us<strong>in</strong>g m/c<br />
Detector response<br />
– Subtract components<br />
(4.4.1)<br />
– Position<strong>in</strong>g uncerta<strong>in</strong>ty<br />
(4.4.4)
Modell<strong>in</strong>g external photon beams<br />
1978 Patau<br />
– Target, flatten<strong>in</strong>g filter<br />
1981 Nilson and Brahme<br />
– Transparent components<br />
1988 Udale<br />
– Modular Philips l<strong>in</strong>ac<br />
1995 Rogers et al (BEAM)<br />
– General purpose code
Where do the photons come from?<br />
Chaney et al (1994)<br />
Centre of mass 6cm
Details of l<strong>in</strong>ac components<br />
Flatten<strong>in</strong>g filter<br />
– Different material
Multileaf collimator model<br />
Tongue and groove<br />
– [a] &[c] use ray trace<br />
– [c] <strong>in</strong>cludes t & g<br />
Intensity map<br />
M/C
kV cone beam CT<br />
Calibrat<strong>in</strong>g M/C calculated dose (D<strong>in</strong>g, 2008)<br />
– Wrt chamber <strong>in</strong> phantom ,then apply to image.
MatrixX<br />
– Chamber array<br />
– Limited resolution<br />
EPID<br />
– portal imager dose<br />
TPS<br />
– Analytical model<br />
IMRT verification
Tomo<strong>therapy</strong><br />
Rotat<strong>in</strong>g source<br />
Sterp<strong>in</strong>(2008)<br />
– TomoPen<br />
– PENELOPE code<br />
3 phase spaces<br />
– Each jaw sett<strong>in</strong>g<br />
Weight PSF<br />
– For each angle<br />
– Interpolate angles
Conclusion<br />
Excellent overview of M/C <strong>in</strong><br />
radio<strong>therapy</strong><br />
Helpful summary of computational<br />
issues<br />
Radiation physics concisely described
Thank you for your attention