Dies ist der Titel der Präsentation - Welcome | SASRO · 2018. 2. 22. · • ICRU 58 (1997): Dose and Volume Specification for Reporting Interstitial Therapy • American Brachytherapy

Division of Medical Radiation Physics

BRACHYTHERAPY

Dario Terribilini

Dario Terribilini, Ph.D. SSRMP

Div. of Med. Radiation Physics

Inselspital - University of Berne

CH-3010 Berne

Switzerland

Phone: +41 31 632 1898

Fax: +41 31 632 2676

Email: [email protected]

www.ams.unibe.ch www.insel.ch

mailto:[email protected]

http://www.ams.unibe.ch/

http://www.insel.ch/

Dario Terribilini / Brachytherapy – FMH2011


http://www.estro.org/estroactivities/Pages/

GEC-BRACHYTHERAPYCOMMITTEEACTIVITY.aspx



http://www.estro-education.org/publications/

Documents/GEC ESTRO Handbook of Brachytherapy.html



http://www-naweb.iaea.org/nahu/dmrp/





Table of Contents

• Introduction

• Photon/Beta Source Characteristics

• Dose distribution around sources

• Dose calculation procedures

• Dose specification and reporting

• Quality Controls (Physical parameters)

• Inaccuracies

• (Clinical use and dosimetry systems)









Tiefe

Do

sis

Photonen (perkutane Therapie)

Protonen

Introduction



Tiefe

Do

sis

Photonen (perkutane Therapie)

Protonen

Introduction

Photonen (Brachtherapie)





Miniature X-Ray sources (50 kV)



Gynecological applications, rectum

HNO, lip, eyelid, mamma, rectum, prostate

or eye cornea

Bronchus, oesophagus, HNO

Single catheter or flabs















Pulsed dose rate (PDR): Simulation of a low dose rate

(LDR) treatment (50-100cGy/h) by a series of short dose

pulses separated by intervals of 1 hour to several hours



Introduction



Introduction



Introduction

Electronic X-Ray Source

• 50 kV, 0.3 mA, 15 W

• Water cooled

• Can be used as

HDR source

Rivard et al, Med Phys. 33(11), 2006















Photon Source Characteristics

Radionuclides Photons

















Dose distribution around sources – Point Source

Air

Air

Measurement: ( )

Source

XXX

d




Wasser

Air

Source

XXX

d




Wasser

Water

Source

XXX

d




Wasser

Water

Source

correction due to Bremsstrahlung

XXX

d















is

1is

p

Dose calculation procedures – Point Sources

2s

4s

3s

1s

isipspspspspp tsDtsDtsDtsDtsDD )()()()()(4321 4321





t is the thickness of the source capsule

is the attenuation coefficient for photon in the source capsule

material





Dose distributions around sources

The calculation process according

to the Sievert-integration procedure

considers the dose at a point near

the source as the summation of

point-source contributions. An

elongated source is then divided

into a series of infinitesimal source

elements.

This method is accurate to within

2%–8% for 137Cs sources but is

less accurate at low- and

intermediate-photon energies e.g.,

less than 0.4 MeV.



is

1is

p


2s

4s

3s

1s




is

1is

p

Dose calculation procedures – Line Sources

2s

4s

3s

1s












AAPM TG 43 algorithm – Formalismus



is

1is

p


2s

4s

3s

1s




is

1is

p

Dose calculation procedures – Line Sources

2s

4s

3s

1s




is

1is

p

Dose calculation procedures – AAPM TG 43

2s

4s

3s

1s




AAPM TG 43 algorithm – Assumptions & Limitations

• Dose calculation in water

– no material heterogeneities within the body

– no applicators

– no shieldings

– no source interplay

• Infinite patient

– no phantom size effect

• Azimuthal symmetry



AAPM TG 43 algorithm – Limitations

Rivard et al., Med Phys. 36, 2009.



Alternative Approaches

The goal is to take

• patient inhomogeneities

• patient shape

• source interplays

• effects of applicators and shieldings

into account which are ignored by the AAPM TG 43

protocol

Analytical Models (Convolution/Superposition, CC)

Full Monte Carlo Simulations

Deterministic solutions of the transport equations

(LBTE)







(Manchester System for gynecological applications, ect)







…for LDR!







References on dose specification & reporting

• ICRU 38 (1985): Dose and Volume Specification for Reporting

Intracavitary Therapy in Gynaecology

• ICRU 58 (1997): Dose and Volume Specification for Reporting

Interstitial Therapy

• American Brachytherapy Society (ABS) Recommendations for

Transperineal Permaent Brachytherapy of Prostate Cancer (IJROBP

1999)

• SGSMP-Bericht 18 (1996): Dosis- und Volumenspezifikationen zur

Dokumentation in der Brachytherapie

• http://www.estro-education.org/publications/Documents/GEC ESTRO

Handbook of Brachytherapy.html

Reporting in Brachytherapy: Dose and Volume Specification



Quality Control procedures of afterloading

equipment and implants – Phisical parameters HDR / PDR,

Remote

afterloading

MDR / LDR,

Remote

afterloading

LDR,

manual

afterloading

Permanent

Implant

Source calibration X X X X

Radioactive decay X X X

Source position accuracy X X

Linear uniformity of (wire) sources X X

Source length X X

Source identification X X

Length of treatment tubes X

Transit time effect X X

Timer consistency & linearity X X

Grid calibration X



Baltas (Bern, 2007)



Baltas (Bern, 2007)



Baltas (Bern, 2007)



Baltas (Bern, 2007)



Thank you

…Questions?





Seelentag, 2009











If the tandem displaces the central canal,

point A moves with the canal, but point B

remains fixed at 5 cm from the midline.















































