Inverse Treatment Planning Method

• US 20090060130A1
• Filed: 02/02/2007
• Published: 03/05/2009
• Est. Priority Date: 02/09/2006
• Status: Active Grant

• Current Assignee: Deutsches Krebsforschungszentrum Stiftung Des Oeffentlichen Rechts
• Original Assignee: Deutsches Krebsforschungszentrum Stiftung des Offentlichen Rechts
• Inventors: Oelfke, Uwe, Wilkens, Jan
• Granted Patent: US 8,183,541 B2
• Time in Patent Office: Days
• US Class Current: 378/65
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 5/1031 using a specific method of dose optimization
• CPC Class Codes: A61N 5/1042 with spatial modulation of the radiation beam within the treatment head

Abstract

The invention relates to a radiation treatment apparatus and an inverse treatment planning method for intensity modulated particle therapy for the treatment of a target within a biological system using at least two fields, each field comprising a plurality of Bragg peaks, the at least two fields being planned to place a defined number of beam spots j from different directions with certain weights w_j within the target. The inverse treatment planning method optimizes the weights w_j of the beam spots for the at least two fields simultaneously in order to produce a prescribed biological effect within the target by minimizing an objective function based on biological effects ε, the biological effects ε being treated in a linear-quadratic model, which describes the biological effects in the target by two parameters α and β, where ε=αD+βD², D denoting a dose, and wherein the two parameters α and β for each voxel i of the target (α_i and β_i) are calculated as dose-averaged mean values of α_i,j- and √{square root over (β_i,j)}-components, which relate to all beam spots j contributing to a total dose D_i in the voxel i.

Claims

1-10. -10. (canceled)

11. An inverse treatment planning method for intensity modulated particle therapy for the treatment of a target within a biological system using at least two fields, each field comprising a plurality of Bragg peaks, the at least two fields being planned to place a defined number of beam spots j from different directions with certain weights w_j within the target, characterized in that the inverse treatment planning method optimizes the weights w_j of the beam spots for the at least two fields simultaneously in order to produce a prescribed biological effect within the target by minimizing an objective function based on biological effects ε

, the biological effects ε

being treated in a linear-quadratic model which describes the biological effects in the target by two parameters α and

β

, where ε

=α

D+β

D², D denoting a dose, and wherein the two parameters α and

β

for each voxel i of the target α

_i and β

_i are calculated as dose-averaged mean values of α

_i,j- and √

{square root over (β

_i,j)}-components, which relate to all beam spots j contributing to a total dose D_i in the voxel i.

12. The inverse treatment planning method according to claim 11, wherein an objective function is minimized, which is based on the formula

$F_{\varepsilon }$



( w →

) = ∑

i ∈

T 

( ɛ

i 

( w →

) - ɛ

T ) 2

with ε

_i denoting the biological effect in the voxel i of the target, {right arrow over (w)} the weights of the beam spots and ε

_T the prescribed biological effect of a reference radiation.

13. The inverse treatment planning method according to claim 11, wherein an objective function is minimized, which is based on the formula

$F_{\varepsilon }$



( w →

) = ∑

i ∈

T 

( α

i 

( w →

) 

D i 

( w →

) + β

i 

( w →

) 

D i 2 

( w →

) - ɛ

T ) 2

with D_i denoting the total dose of the at least two fields in voxel i and α

_i and β

_i the α

- and β

-values at voxel i, wherein

$D_i=\underset{j=1}{\overset{N}{\sum <br><br>}}<br><br>w_j<br><br>D_{i,j}$

with D_i,j denoting a dose contribution of beam spot j at voxel i for unit fluence, N beam spots contributing to the dose D_i at voxel i, and w_j denoting a weighting factor of beam spot j and wherein the prescribed biological effect ε

_T is given by

ε

_T=α

_T^XD_T+β

_T^XD_T²

with α

_T^X and β

_T^X being X-ray response parameters of the target and D_T denoting a prescribed photon dose.

14. The inverse treatment planning method according to claim 11, wherein an objective function is minimized, which includes constraints relating to minimum and maximum biological effect levels for the target and maximum effect levels for organs at risk or normal tissue within the biological system.

15. The inverse treatment planning method according to claim 11, wherein the two parameters α

and β

for each voxel i of the target (α

_i and β

_i) are calculated as dose-averaged mean values of the form

${\mathrm{\alpha <br><br>}}_i=\frac{1}{D_i}<br><br>\underset{j=1}{\overset{N}{\sum <br><br>}}<br><br>w_j<br><br>D_{i,j}<br><br>{\mathrm{\alpha <br><br>}}_{i,j}<br><br><br><br>\mathrm{and}$ $\sqrt{{\mathrm{\beta <br><br>}}_i}=\frac{1}{D_i}<br><br>\underset{j=1}{\overset{N}{\sum <br><br>}}<br><br>w_j<br><br>D_{i,j}<br><br>\sqrt{{\mathrm{\beta <br><br>}}_{i,j}}$

for D_i>

0,

$D_i=\underset{j=1}{\overset{N}{\sum <br><br>}}<br><br>w_j<br><br>D_{i,j}$

with N beam spots contributing to the total dose D_i in voxel i.

16. The inverse treatment planning method according to claim 11, wherein the α

_i,j- and √

{square root over (β

_i,j)}-components are derived from a radiobiological model or from measured data for α and

β

as a function of depth in a single Bragg peak.

17. The inverse treatment planning method according to claim 11, wherein a constant value β

_i,j=β

_i is set, which depends only on a tissue type at voxel i.

18. The inverse treatment planning method according to claim 11, wherein the α

_i,j-components are assumed to be laterally constant and are extracted from a single curve as a function of residual range, independent of an initial beam energy.

19. Use of an inverse treatment planning method for intensity modulated particle therapy for the treatment of a target within a biological system using at least two fields, each field comprising a plurality of Bragg peaks, the at least two fields being planned to place a defined number of beam spots j from different directions with certain weights w_j within the target, characterized in that the inverse treatment planning method optimizes the weights w_j of the beam spots for the at least two fields simultaneously in order to produce a prescribed biological effect within the target by minimizing an objective function based on biological effects ε

, the biological effects ε

being treated in a linear-quadratic model which describes the biological effects in the target by two parameters α and

β

, where ε

=α

D+β

D², D denoting a dose, and wherein the two parameters α and

β

for each voxel i of the target α

_i and β

_i are calculated as dose-averaged mean values of α

_i,j- and √

{square root over (β

_i,j)}-components, which relate to all beam spots j contributing to a total dose D_i in the voxel i for planning the treatment of a tumor with an ion beam containing ions with an atomic number≧

2.

20. A radiation treatment apparatus for delivering a radiation treatment to a target within a biological system comprising means for generating at least two fields, each field comprising a plurality of Bragg peaks, the at least two fields being provided to place a defined number of beam spots j from different directions with certain weights w_j within the target and characterized by means for inverse treatment planning being provided for optimizing the weights w_j of the beam spots for the at least two fields simultaneously before the radiation treatment in order to produce a prescribed biological effect within the target by minimizing an objective function based on biological effects ε

, the biological effects ε

being treated in a linear-quadratic model, which describes the biological effects in the target by two parameters α and

β

, where ε

=α

D+β

D², D denoting a dose, and wherein the two parameters α and

β

for each voxel i of the target (α

_i, β

_i) are calculated as dose-averaged mean values of α

_i,j- and √

{square root over (β

_i,j)}-components, which relate to all beam spots j contributing to a total dose D_i in the voxel i.