X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
2000-08-23
2002-09-10
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S147000
Reexamination Certificate
active
06449335
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a radiation emitting device, and more particularly, to a system and method for efficiently delivering radiation treatment.
BACKGROUND OF THE INVENTION
Radiation emitting devices are generally known and used, for instance, as radiation therapy devices for the treatment of patients. A radiation therapy device generally includes a gantry which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located within the gantry for generating a high energy radiation beam for therapy. This high energy radiation beam may be an electron beam or photon (x-ray) beam, for example. During treatment, the radiation beam is trained on a zone of a patient lying in the isocenter of the gantry rotation.
In order to control the radiation emitted toward the patient, a beam shielding device, such as a plate arrangement or collimator, is typically provided in the trajectory of the radiation beam between the radiation source and the patient. An example of a plate arrangement is a set of four plates which can be used to define an opening for the radiation beam. The collimator is a beam shielding device which may include multiple leaves (e.g., relatively thin plates or rods) typically arranged as opposing leaf pairs. The plates are formed of a relatively dense and radiation impervious material and are generally independently positionable to delimit the radiation beam.
The beam shielding device defines a field on the zone of the patient for which a prescribed amount of radiation is to be delivered. The usual treatment field shape results in a three-dimensional treatment volume which includes segments of normal tissue, thereby limiting the dose that can be given to the tumor. The dose delivered to the tumor can be increased if the amount of normal tissue being irradiated is decreased and the dose delivered to the normal tissue is decreased. Avoidance of delivery of radiation to the healthy organs surrounding and overlying the tumor limits the dosage that can be delivered to the tumor.
The delivery of radiation by a radiation therapy device is typically prescribed by an oncologist. The prescription is a definition of a particular volume and level of radiation permitted to be delivered to that volume. Actual operation of the radiation equipment, however, is normally done by a therapist. The radiation emitting device is programmed to deliver the specific treatment prescribed by the oncologist. When programming the device for treatment, the therapist has to take into account the actual radiation output and has to adjust the dose delivery based on the plate arrangement opening to achieve the prescribed radiation treatment at the desired depth in the target.
The radiation therapist's challenge is to determine the best number of fields and intensity levels to optimize dose volume histograms, which define a cumulative level of radiation that is to be delivered to a specified volume. Typical optimization engines optimize the dose volume histograms by considering the oncologist's prescription, or three-dimensional specification of the dosage to be delivered. In such optimization engines, the three-dimensional volume is broken into cells, each cell defining a particular level of radiation to be administered. The outputs of the optimization engines are intensity maps, which are determined by varying the intensity at each cell in the map. The intensity maps specify a number of fields defining optimized intensity levels at each cell. The fields may be statically or dynamically modulated, such that a different accumulated dosage is received at different points in the field. Once radiation has been delivered according to the intensity map, the accumulated dosage at each cell, or dose volume histogram, should correspond to the prescription as closely as possible.
In such intensity modulation radiation treatments, multiple fields are often used to deliver radiation to a treatment area. The different intensity fields may involve different locations (i.e., ports) of the multi-leaf collimator relative to the treatment area or different shaped fields created by repositioning leaves of the multi-leaf collimator. The sequence of the treatment fields within each port is typically randomly chosen with no attention given to the sequence that occurs in going from one port to the next and how the step between ports affects the sequencing within a port. The segments are often arranged to travel from left to right within a port, without regard to leaf positions within adjacent ports. Thus, when the collimator moves to a new port, the leaves are already positioned to the right from the last treatment field for the previous port and the leaves must travel back to the left before starting delivery of the first treatment field at the next port. This sequencing of treatment fields results in unnecessary leaf travel, thus, increasing treatment time and wear on the leaves and equipment.
Accordingly, there is therefore, a need for a method and system for optimizing radiation treatment with a multi-leaf collimator to increase the life of the collimator or reduce treatment time.
SUMMARY OF THE INVENTION
A method and system for optimizing radiation delivery with a multi-leaf collimator are disclosed.
A method of the present invention is for sequencing treatment fields defined by leaves of a multi-leaf collimator positioned to block radiation from a radiation source and define an opening between the radiation source and a treatment area. The multi-leaf collimator is operable to rotate relative to the treatment area to define a plurality of treatment ports, each port having one or more treatment fields. The method generally comprises ordering the collimator ports based on direction of travel of the collimator relative to the treatment area such that each port has at least one corresponding adjacent port and selecting a sequence of treatment fields for each collimator port based on the treatment fields within adjacent ports to optimize delivery of radiation.
In another aspect of the invention, the treatment fields for each of the ports are configured to treat generally the same region within the treatment area. The method generally includes ordering the collimator ports based on direction of travel of the collimator relative to the treatment area such that each port has at least one adjacent port and selecting a sequence of the treatment fields for each collimator port such that the leaves are moved from one treatment field to the next within a port in opposite longitudinal directions for adjacent ports to optimize delivery of radiation.
The radiation treatment may be optimized to reduce total radiation treatment time or reduce the overall leaf travel between treatment fields. The treatment fields may be sequenced independently for each port. The order of the treatment fields within each port may then be modified based on the position of leaves for the last treatment field of the previous port or the first treatment field of a subsequent port. Alternatively, the treatment fields may be sequenced for a first collimator port and the first treatment field for the second port selected based on the leaf positions of the last treatment field for the first port. The sequence of treatment fields for the second port is then optimized based on the first treatment field. This process is continued until the sequence of treatment fields for each port is selected.
The above is a brief description of some deficiencies in the prior art and advantages of the present invention. Other features, advantages, and embodiments of the invention will be apparent to those skilled in the art from the following description, drawings, and claims.
REFERENCES:
patent: 5663999 (1997-09-01), Siochi
patent: 5724403 (1998-03-01), Siochi et al.
patent: 5726400 (1998-03-01), Swerloff et al.
patent: 6052436 (2000-04-01), Huttner et al.
patent: 6188748 (2001-02-01), Pastyr et al.
patent: 6240161 (2001-05-01), Siochi
patent: 6240162 (2001-05-01), Her
Kiknadze Irakli
Kim Robert H.
Siemens Medical Solutions USA , Inc.
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