Convolution is one of several value-added software modules in the Leksell GammaPlan

portfolio. It enables extremely accurate dose calculation for the treatment of

heterogeneous tissue.

Accurate Dose Distribution – Anywhere

Convolution provides dose calculation accuracy that approaches the quality of a true

Monte Carlo algorithm.* It is specifi cally designed to rapidly generate dose plans for

heterogeneous tissue, such as tissue-air and tissue-bone interfaces.

Flexibility for Speed and Effi ciency

Convolution gives you freedom-of-choice and superb fl exibility, allowing you

to decide which dose calculation algorithm to use for a specifi c target. You can

choose TMR (Tissue-Maximum-Ratio) or Convolution for a specifi c target or

group of targets, depending on target location. Another option is to choose

one of these algorithms for all targets.

Total Confi dence

The accuracy that is possible with Convolution helps build confi dence,

while also giving you control. Choose your settings, change them at

will and maintain full control over the fi nal solution.

Leksell GammaPlan®

ConvolutionConfi dent Dose Calculation in Heterogeneous Tissue

Why Convolution?

• Precise dose calculation in

heterogeneous tissue

• Powerful complement to TMR

• Flexibility to choose TMR or

Convolution

*Based on the results of benchmarking comparisons between Convolution and Monte Carlo calculations.

Convolution is an accelerated multi-beam convolution algo-

rithm that models build-up effects and takes heterogeneity

of material into account. It uses Monte Carlo pre-calculated

fl uence planes for each beam calculated at the center of

a water phantom. The fl uence planes are scaled according

to depth and heterogeneity. The algorithm separates the

primary and the scattered secondary contribution for

calculation of the dose.

The primary dose is calculated by convolving the TERMA

(Total Energy Released per unit MAss) obtained from the

fl uence planes with an electron-density scaled primary kernel.

Arti

cle

no. 0

1886

9.00

MAY

10 ©

2010

Ele

kta

Inst

rum

ent A

B. A

ll m

enti

oned

trad

emar

ks a

nd r

egis

tere

d tr

adem

arks

are

the

prop

erty

of

the

Elek

ta G

roup

. All

righ

ts r

eser

ved.

No

part

of

this

doc

umen

t may

be

repr

oduc

ed in

any

form

wit

hout

wri

tten

per

mis

sion

from

the

copy

righ

t hol

der.

Spec

ifi ca

tion

s su

bjec

t to

chan

ge w

itho

ut n

otic

e.

Elekta AB (publ)Box 7593, SE-103 93 Stockholm, Sweden

Tel +46 8 587 254 00Fax +46 8 587 255 00

info@elekta.com

Corporate Head Offi ce:

Asia Pacifi c

Tel +852 2891 2208Fax +852 2575 7133

info.asia@elekta.com

www.elekta.com Human Care Makes the Future Possible

North America

Tel +1 770 300 9725Fax +1 770 448 6338

info.america@elekta.com

Regional Sales, Marketing and Service:

Europe, Middle East, Africa, Eastern Europe, Latin America

Tel +46 8 587 254 00Fax +46 8 587 255 00

info.europe@elekta.com

Add-on

Inverse Planning

Convolution

Re-Treatment™

ColorPET™

Add-on

DICOM-RT

WarpSpeed™

FunctionalPlanning

ImageMerge™

LeksellGammaPlan®

Convolution – Overview

Convolution requires a full-head CT scan as input. It models build-

up effects as well as heterogeneity effects. The dose calculation is

separated into two parts: primary dose and scatter dose algorithm.

Convolution – for the Highest Calculation Accuracy in Heterogeneous Tissue

Elekta continues to add functionality to Leksell GammaPlan. Using the

latest technology, Gamma Knife® software modules bring more power to

your planning. This opens the platform for future upgrades and opportuni-

ties, while delivering on daily clinical needs for improved workfl ow, cost

effi ciency and treatment quality.

In order to gain simulation speed, the radiological lengths

are pre-calculated for many equally distributed directions at

every voxel and are used for each beam, thereby avoiding

the need to repeatedly refer to the electron density-table.

The dose due to scattering is calculated by convolving a

model-fi tted depth kernel with the TERMA at the central

axis of each beam. This scattered depth dose is then used to

scale a lateral scattering dose profi le.

Convolution relies on relative electron density defi ned from

CT images covering the entire skull. Conversion between

CT numbers and electron density values is performed via a

user-defi ned CT calibration curve (per CT scanner console).

Any electron density value outside the CT calibration curve is

truncated. While planning, truncated values can be displayed

during the defi nition of the electron density.

Dose convolution. Pfx 16mm shot

z (m

m)

AIR WATERx (mm)

High dose

Low dose

Dose comparison Convolution - Monte Carlo. Pfx 16mm shot

AIR WATER

Dos

e

90 100 110 120 130 140 150

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Convolution

Monte Carlo

x (mm)