Method of forming energy distribution

Details Method of forming energy distribution Method of forming energy distribution

1998-06-09

2001-07-03

Wachsman, Hal (Department: 2857)

Data processing: measuring, calibrating, or testing

Measurement system in a specific environment

Electrical signal parameter measurement system

C702S065000, C250S492300, C250S363040

Reexamination Certificate

active

06256591

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method of forming an energy distribution by determining an energy source to be given to a system so that an energy distribution created in the system coincides with a desired distribution.
BACKGROUND ART
A conventional energy distribution forming method disclosed in, for example, “Denki Gakkai Magunetikkusu Kenkyukai Shiryo”, MAG-94-26, pp. 63-69 (1994) is called a sampled pattern matching method (hereinafter abbreviated to “SPM method”).
The SPM method is employed for determining a distribution pattern of an energy source forming a desired field when a distribution (electric field distribution, magnetic field distribution, radiation intensity distribution, temperature distribution or the like) in the desired field is given. To put it concretely, the SPM method arranges lattice points in a space and makes sequential search to find a point which makes an energy source assumed to be at that point form a pattern close to the distribution of the desired field. Search is terminated upon the increase of the coincidence degree of the pattern created by the energy source with the distribution of the desired field to a maximum.
The pattern coincidence degree is evaluated by an angle &thgr; made between a measured distribution pattern vector V and a calculated distribution pattern vector U. Concretely, pattern coincidence degree is defined by the following equality (1):
&ggr;=cos &thgr;=
U·V
/(|
U||V|
)  (1)
where U·V is inner product, and |U| and |V| indicate the respective magnitudes of the vectors U and V.
FIG.
1
(
a
) shows a desired magnetic field distribution
101
, and FIG.
1
(
b
) shows an arc-shaped coil
102
having the shape of a circular arc for creating a magnetic field distribution close to the desired magnetic field distribution estimated by the SPM method. FIG.
1
(
c
) shows a magnetic field distribution
103
formed by the arc-shaped coil
102
in FIG.
1
(
b
). The size of the circle is illustrated to be proportional to magnetic field intensity. The magnetic field distribution
103
realizes approximately the same as the magnetic field pattern shown in FIG.
1
(
a
), which proves the effectiveness of the SPM method. It should be noted that constant current must be supplied to the coil because the foregoing method only distributes unit current sources and is unable to vary the amplitude of the current in principle.
Since the conventional method of forming an energy distribution is thus constructed, the position of an energy source having a fixed intensity can be determined, but there remains a problem the intensity of the energy source is invariable.
The present invention has been made to solve the foregoing problem and it is therefore an object of the present invention to provide an energy distribution forming method capable of varying the intensity of energy source distribution.
DISCLOSURE OF THE INVENTION
The present invention comprises a first step of determining a minimum value q
min
and a maximum value q
max
for energy source density, a second step of setting the minimum energy source density q
min
at m energy source density setting positions x
i
(i=1, . . . , m), a third step of increasing by a predetermined value &Dgr;q an energy source densities q
i
at the positions x
i
(i=1, . . . , m) excluding the energy source density setting positions x
i
where q
i
+&Dgr;q>q
max
, thereby calculating energy distribution vectors U
i
, a fourth step of calculating pattern coincidence degree &ggr;
i
from the calculated energy distribution vectors U
i
and a desired energy distribution vector V, a fifth step of changing the energy source density at the position x
i
which gives the largest pattern coincidence degree to q
i
+&Dgr;q, a sixth step of repeating the third step to the fifth step until the energy source densities at all the positions x
i
reach the maximum energy source density q
max
and searching out an energy source density distribution P which gives the largest pattern coincidence degree, and a seventh step of calculating the ratio a between an energy distribution vector U
P
calculated by using the density distribution P searched out in the sixth step, and the desired energy distribution vector V to obtain an energy source density distribution P/a. Thus, input energy which gives a desired energy distribution can be efficiently obtained.
The present invention comprises a first step of determining a minimum value q
min
and a maximum value q
max
for energy source density, a second step of setting the maximum energy source density q
max
at m energy source density setting positions x
i
(i=1, . . . , m), a third step of decreasing by a predetermined value &Dgr;q an energy source densities q
i
at the positions x
i
(i=1, . . . , m) excluding the positions x
i
where q
i
−&Dgr;q<q
min
and calculating energy distribution vectors U
i
, a fourth step of calculating pattern coincidence degrees &ggr;
i
from the calculated energy distribution vectors U
i
and a desired energy distribution vector V, a fifth step of changing the energy source density at the position x
i
which gives the largest pattern coincidence degree to q
i
−&Dgr;q, a sixth step of repeating the third step to the fifth step until the energy source densities at all the positions x
i
reach the minimum energy source density q
min
and searching out an energy source density distribution P which gives the largest pattern coincidence degree and a seventh step of calculating the ratio a between an energy distribution vector U
P
calculated by using the density distribution P searched out in the sixth step, and the desired energy distribution vector V to obtain an energy source density distribution P/a. Thus, input energy which gives a desired energy distribution can be efficiently obtained.
The present invention selects one of an electric charge density distribution, a particle beam intensity distribution, a current density distribution, a voltage source distribution, an electromagnetic field source distribution, a radiation source distribution, a heat source distribution, a light source distribution, a load distribution, a sound source distribution and a magnetization distribution as an energy source distribution. Thus, an energy source can be easily selected.
The present invention selects one of an electric field distribution, a particle dose distribution, a potential distribution, an electromagnetic field distribution, a stress distribution, a displacement distribution, a temperature distribution, a flow velocity distribution, a sound pressure distribution and a radiation intensity distribution as energy distribution. Thus, energy distribution can be easily selected.
The present invention uses the cosines of the angles between calculated energy distribution vectors U
i
and the desired energy distribution vector V as pattern coincidence degrees. Therefore, input energy which gives the desired energy distribution can be efficiently obtained.
The present invention uses the sines of the angles between calculated energy distribution vector U
i
and the desired energy distribution vector V as pattern coincidence degrees. Therefore, input energy which gives the desired energy distribution can be efficiently obtained.
The present invention selects a proton dose distribution as a particle dose distribution, and a proton beam intensity distribution as a particle beam intensity distribution. Therefore, an energy intensity distribution having a sharp rising characteristic and a sharp falling characteristic can be easily obtained.
The present invention selects a particle dose distribution as an energy source distribution, and selects an internal particle dose distribution as an energy distribution. Therefore, a desired internal radiation dose distribution can be set. For example, the interior of an tumor can be irradiated with radiation in a uniform dose distribution limiting radiation dose in normal tissues around the t

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