System and methods of photon-based radiotherapy and radiosurgery delivery
Photon-based radiosurgery is widely used for treating local and regional tumors. The key to improving the quality of radiosurgery is to increase the dose falloff rate from high dose regions inside the tumor to low dose regions of nearby healthy tissues and structures. Dynamic photon painting (DPP) further increases dose falloff rate by treating a target by moving a beam source along a dynamic trajectory, where the speed, direction and even dose rate of the beam source change constantly during irradiation. DPP creates dose gradient that rivals proton Bragg Peak and outperforms Gamma Knife® radiosurgery.
1. A computer system method for radiosurgery, the method comprising the steps of:
determining beam curve fitting parameters of each beam of a beam source using the following curve fitting functions of a Tissue Phantom Ratio (TPR) and an Off Center Ratio (OCR):
TPR
(
d
)
=
{
∑
i
=
1
5
a
i
d
i
-
1
for
d
<
d
max
e
-
a
6
·
(
d
-
a
7
)
for
d
>
d
max
OCR
(
SAD
,
r
)
=
0.5
·
(
erfc
(
a
·
(
r
·
800
SAD
-
b
)
)
+
erfc
(
a
·
(
r
·
800
SAD
+
b
)
)
)
,
where d is the depth and r is the off-center radius of a point of a target, Source to Axis Distance (SAD) is Source Surface Distance (SSD)+d, and erfc is an error function; and
revolving a beam source in a hemispherical trajectory around the point of the target according to the beam curve fitting parameters, wherein the radiation beams of the beam source are dynamically changed to irradiate the target increasing radiation dose falloff rate.
2. The computer system method according to claim 1 , wherein the error function is:
erfc
(
x
)
=
2
π
∫
x
∞
e
-
t
2
ⅆ
t
.
3. The computer system method according to claim 1 , wherein the revolving step further comprises the step of rotating the beam source around a center of the target from a latitude angle and a longitude angle.
4. The computer system method according to claim 1 , wherein the hemispherical trajectory of the beam source is described using the following parameters: (1) latitude angular range [φ 1 , φ 2 ], (2) longitude angular range [φ 1 , φ 2 ], and (3) source to axis distance.
5. The computer system method according to claim 1 , wherein the hemispherical trajectory is a helical trajectory.
6. The computer system method according to claim 1 , wherein the radiation beams are cone radiation beams.
7. The computer system method according to claim 1 , wherein the revolving step further comprising the step of creating a plurality of does kernals.
8. The computer system method according to claim 7 , further comprising the steps of:
creating a library of kernals, wherein each kernel includes characteristics comprising a beam shape, a profile and a trajectory; and
using the library to investigate the characteristics of each kernel to produce one or more dose focusing powers.
9. The computer system method according to claim 4 , wherein φ 1 is 1° and φ 2 is 40°.
10. The computer system method according to claim 4 , wherein φ 1 is 1° and φ 2 is 50°.
11. The computer system method according to claim 4 , wherein φ 1 is 1° and φ 2 is 65°.
12. The computer system method according to claim 4 , wherein φ 1 is 5° and φ 2 is 55°.
13. The computer system method according to claim 4 , wherein φ 1 is 10° and φ 2 is 60°.
14. The computer system method according to claim 4 , wherein the source to axis distance (SAD) is 800 mm.
15. The computer system method according to claim 1 , wherein the target is a brain tumor.