Radiant energy – Radiation controlling means
Reexamination Certificate
2001-11-20
2003-07-22
Lee, John R. (Department: 2881)
Radiant energy
Radiation controlling means
C250S492300, C315S505000
Reexamination Certificate
active
06597005
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of checking emergency shutdown of an ion beam therapy system which, in particular, is operated with heavy ions.
BACKGROUND OF THE INVENTION
Ion beam therapy systems are preferably used for the treatment of tumors. They have the advantage that when a target is irradiated, the major part of the energy of the ion beam is transferred to the target, while only a small amount of energy is transmitted to sound tissue. Therefore, a relatively high irradiation dose can be used to treat a patient. By contrast, X-rays transmit their energy to the same extent to the target and to sound tissue, so that, for health reasons in order to protect the patient, a high irradiation dose cannot be used.
U.S. Pat. No. 4,870,287, for example, discloses an ion beam therapy system in which proton beams are generated by a proton source, it being possible for its protons to be fed to various treatment or irradiation stations via an accelerator device. At each treatment station there is a rotating frame with a patient couch, so that the patient can be irradiated with the proton beam at different irradiation angles. While the patient is located physically at a fixed point within the rotating frame, the rotating frame rotates about the body of the patient in order to focus the irradiation beams at different irradiation angles onto the target, located at the isocenter of the rotating frame. The accelerator device comprises the combination of a linear accelerator (LINAC) and a synchrotron ring, as it is known.
In H. F. Weehuizen et al, CLOSED LOOP CONTROL OF A CYCLOTRON BEAM FOR PROTON THERAPY, KEK Proceedings 97-17, January 1998, a method of stabilizing the proton beam in proton beam therapy systems is proposed, the treatment beam being controlled actively in such a way that, at two measurement points spaced apart from each other in the longitudinal direction, it lies on the center line of the corresponding beam feed system. The first measurement point is located between a pair of deflection magnets and is formed by a multiwire ionization chamber. Depending on the current value, supplied by this multiwire ionization chamber, of the beam position with respect to the center of the beam path, the PI control of further deflection magnets, which are arranged upstream of the first-named pair of deflection magnets, is produced. The second measurement point is located shortly upstream of the isocenter and is formed by an ionization chamber subdivided into four quadrants. Depending on the current position value from this ionization chamber, again PI control signals are generated, but these are intended for the first-named deflection magnets. The intention of this control is to permit both angular stability with respect to the center line of the beam feed system and lateral positional stability of the proton beam.
When carrying out heavy ion irradiation, that is to say an irradiation using ions which are heavier than protons, large and heavy equipment is required, however, so that here there is the tendency to avoid the use of rotary frameworks and, instead, to move the patient or the patient couch. Corresponding therapy systems are described, for example, in E. Pedroni: Beam Delivery, Proc. 1st Int. Symposium on Hadrontherapy, Como, Italy, Oct. 18-21, 1993, page 434. These systems are accordingly eccentric systems.
Since, however, fundamentally isocentric systems are preferred by oncologists, a heavy ion beam therapy system has been proposed in which, although rotary frameworks are used at the treatment stations, the radii of the rotary frameworks can be reduced by the treatment beam fed to each rotary framework horizontally along its axis of rotation being guided, with the aid of suitable magnetic and optical arrangements, in such a way that it firstly runs away from the axis of rotation and subsequently crosses the axis of rotation again at the isocenter in order to irradiate a target. In order to irradiate the target, a raster scanner is provided, which comprises vertical deflection means and horizontal deflection means which each deflect the treatment beams at right angles to the beam axis, so that an area surrounding the target is scanned by the treatment beams. This system therefore substantially provides beam guidance in only one plane of the rotary framework.
The irradiation by means of the raster scanner is carried out with the aid of irradiation dose data, which are calculated by the control system of the ion beam therapy system automatically, depending on the patient to be irradiated or to be treated.
Since, in principle, high operational safety and operational stability with regard to the treatment beam are required of ion beam therapy systems, in the case of the heavy ion beam therapy system described previously, a monitoring device is provided to monitor the treatment beam supplied by the raster scanner. This monitoring device is arranged between the last deflection magnet of the aforementioned magnet arrangement and the isocenter, and may comprise ionization chambers for monitoring the particle flux and multiwire chambers for monitoring the beam position and the beam width.
During the operation of medical electron accelerators, various DIN standards have to be complied with for reasons of safety. These relate firstly to acceptance testing, that is to say checking the operational readiness, and secondly testing the constancy, that is to say checking the operational stability, of the system. For ion beam therapy systems, in particular for heavy ion beam therapy systems, such safety standards developed specifically for ion beam therapy systems are not yet known. However, in the case of ion beam therapy systems there is also the requirement for the greatest possible operational safety and operational stability.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention is therefore based on the object of proposing a method of checking emergency shutdown of an ion beam therapy system, in order to improve the operational safety and operational stability, in particular as referred to emergency shutdown. At the same time, the intention is for the method to be suitable in particular for use with heavy ions.
According to the present invention, this object is achieved by a method having the features of claim 1. The dependent claims in each case define preferred and advantageous embodiments of the present invention.
According to the present invention, an ion beam therapy system is operated which has at least one ion source, an accelerator device and a beam guidance system, a check of emergency shutdown being carried out.
For this purpose, a check is carried out of manual and automatic emergency shutdown with automatic monitoring of all the safety-relevant device parameters and with a display of all the safety-relevant states on consoles of a technical therapy control room and a main control room for the entire system of an ion beam therapy installation.
This check of the serviceability of an interlock unit or emergency shutdown of an ion beam therapy system is of a very high relevance in terms of safety.
For example, all the safety-relevant device parameters have to be checked upon the triggering of an emergency shutdown of the system in the event of an interlock case or an interlock condition being present. Shutdown of the treatment beam can be carried out only when an interlock case has been detected. Therefore, all sources which can lead to an interlock case must be simulated individually in a test, and the triggering of the interlock, that is to say the generation by the interlock unit of the signals that lead to the emergency shutdown of the treatment unit, must be checked. During operation, the interlock unit preferably monitors the signals from the limit switches of the moving parts in the beam guidance, the states of the magnetic network devices of the raster scanner magnets, the ionization chambers with regard to the voltage supply, a data overflow in the data transmission, compliance with intensity limiting values and synchronism of the ind
Badura Eugen
Becher Wolfgang
Brand Holger
Essel Hans-Georg
Haberer Thomas
Frommer & Lawrence & Haug LLP
Gesellschaft fuer Schwerionenforschung mbH
Gurzo Paul M.
Lee John R.
Santucci Ronald R.
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