Patent Number: 061371149
Section: summary

The invention relates to an irradiation apparatus having at least one exchangeable radiation source that can be moved between at least one non-operative position and at least one radiating position by means of a transport cable, the apparatus further having a transport container for transporting radiation sources to be exchanged. An irradiation apparatus of this type is known from, for example, EP-B1-0 138 088, the content of which is incorporated by reference into the disclosure of the present description. The object of this known irradiation apparatus, which includes a plurality of radiation sources, is to simultaneously insert a predeterminable number of radiator holding elements into the corresponding number of hollow probes by means of a single drive device. In one specific embodiment, the irradiation apparatus is equipped with only as many radiation sources as are necessary for the therapy to be performed in each treatment situation. For this purpose, the radiation sources are accommodated in small, easy-to-handle, flat cassettes that contain a radiation-source shield in addition to a drive-cable storage drum. The individual cassettes are manually inserted with their flat sides close together into an easily-accessible cassette compartment such that the cassette housing latches with the irradiation apparatus in a closely-adjacent arrangement. Therefore, for an individual radiation therapy, it is only necessary to click the correct cassette combination into the irradiation apparatus. This relieves the treatment technician of the task of transferring the radiator to be used from shielded storage containers into the irradiation apparatus and back as needed using the transport cable, as was formerly the case. Because the flat cassettes must be compact and must be able to be coupled among themselves in the irradiation apparatus, they are not readily suitable for long-distance transport, for example from and to the manufacturer/disposer. Hence, irradiation apparatuses of this type additionally necessitate a radiation-source transport container. More stringent safety requirements are placed on generic irradiation apparatuses that are intended for use in intra-arterial irradiation to prevent a post-angioplasty restenosis. An irradiation apparatus of this type and a treatment method are described in, among other publications, EP-A1-0 633 041. This publication is incorporated by reference into the disclosure of the present patent application. The known irradiation apparatuses are especially subject to a certain risk of operator's error during exchange of the radiation source, so that the radiation source can only be exchanged by specially trained personnel. The radiation sources are supplied to the user in a transport container that typically has two channels. The one channel serves to receive the old radiation sources, that is, the sources to be exchanged, while the other channel serves to receive the fresh radiation source. The irradiation apparatus is connected to the empty channel of the transport container by way of a transport hose. The transport cable subsequently moves the radiation source to be exchanged into the transport container. The drive-side end of the transport cable is detached by the drive after the radiator-side end has been secured against sliding in the transport container. The transport hose is subsequently connected to the channel containing the fresh radiation source, and the fresh radiation source is transferred into the irradiation apparatus in reverse order with respect to the old radiation source. The exchange of radiation sources is a critical situation, because the radiation source is forced to exit the shield of the irradiation apparatus via the transport hose during the process, and because the transport cable must be completely detached and recoupled. In particular, any arbitrary radiation source can be drawn into the irradiation apparatus, so confusion or errors can occur over the whereabouts of old or new radiation sources. It is therefore the object of the invention to provide an irradiation apparatus in which the risk of an operator's error is reduced. The solution is an irradiation apparatus having the features of claims 1, 3 and/or 4. In irradiation apparatuses of the invention, the user stores the radiation source in a shield block when the source is in its position of non-use (non-operative position), and--as a standard practice--the source is moved into the radiating position by means of a transport cable. The shield surrounds the irradiation apparatus such that the transmitted radiation of the irradiation apparatus then meets the specifications for radiation-source containers regarding storage and use of the radiation sources. In accordance with the invention, the radiation-protection container (transport container) used for long-distance transport of the radiation source between the supplier and the user (client) serves as a component of the irradiation apparatus that is or can be integrated. It is therefore inserted much like a key (transport container) into a lock (remaining part of the irradiation apparatus), for which purpose corresponding interface means are provided. This feature creates a usable unit (irradiation apparatus) (claim 1). This prevents the radiation source from leaving its shield at the user's (client's) location during the exchange, for example, for a fresh radiation source. Furthermore, this feature can prevent confusion about used or fresh radiation sources remaining in the apparatus, because a radiation source is associated with exactly one long-distance transport container. These properties of the apparatus are especially advantageous for the user in that he can work with sources of different specifications (with respect to activity, energy and geometry) without difficulty. Thus, it is readily possible to change from HDR to PDR (Pulse-Dose Rate) mode and to use a source that is optimally adapted to the application. To avoid having to excessively increase the transport weight of a transport container of the invention, the transport container can include a shield that meets the specifications for long-distance radiation-source transport containers, and the remaining part of the irradiation apparatus can have a shield that surrounds at least parts of the transport container such that, with respect to the non-operative position of the irradiation apparatus, the transmitted radiation of the apparatus meets (more rigorous) specifications for radiation-source storage containers (claim 2). Of course, the shield of the long-distance transport container can meet the specifications for radiation-source storage containers in certain spatial directions, while it is not sufficiently strong in other spatial directions. This is a compromise between the transport, weight and the operator's comfort in inserting the transport container into the irradiation apparatus. The design of an irradiation apparatus of the invention can be simplified if the transport container has a spiral-shaped transport channel that extends through, inside which the storage position is located. The transport cable can enter at one end of the transport channel, and be connected to an upstream drive, such as a storage drum. The transport cable pushes the radiation source from behind through the transport channel to transfer the source from its non-operative position into its radiating position. The irradiation apparatus shield that surrounds the transport container in the operating position can include a shield hood, preferably one that swings open. This simplifies the exchange of radiation sources, and ensures that, after the transport container has been inserted into the irradiation apparatus, the entire shield meets the specifications for radiation-source storage containers. As a further measure for avoiding operator's errors, means can be provided for automatically locking the radiation source or the transport cable in a transport position during transport of the transport container. This measure can prevent personnel from forgetting to lock the radiation source prior to transport. The radiation source or transport cable is preferably automatically locked when the transport container is removed from the irradiation apparatus. A transport-cable storage element, preferably a storage drum, onto or from which the transport cable is wound and unwound, respectively, can be provided on the transport container. so the transport container and a transport-cable storage element, particularly a storage drum, are combined to form a transport module (claim 3). With this measure, the transport cable need not be separated from its drive unit for transporting the radiation source, a procedure during which a wide variety of errors, particularly operator's errors, could occur. Of course, the transport module can include further transport-cable drive means. It can be advantageous, however--especially with regard to weight--to provide transport-cable drive means, such as a mechanical drive, in the other part of the irradiation apparatus, which means are connected to the transport module or transport-cable storage element through suitable couplings when the transport module is inserted into the other part of the irradiation apparatus. Of course, this coupling can preferably be effected automatically. The modular unit comprising the transport container and the transport-cable storage element also has the advantage of increased precision in the determination of the radiator's position, because any manufacturing tolerances can be taken into account as unalterable correction values, for example. To increase safety, the transport module can include means for locking the storage drum, preferably automatically, during transport of the transport module. This prevents an actuation of the transport-cable drive during transport of the radiation source. The locking means are preferably enabled automatically prior to the initiation of movement of the radiation source from its non-operative position into the radiating position (claim 5). This prevents damage to the assemblies of the irradiation apparatus of the invention, including the transport container or transport module. The locking means are preferably enabled automatically upon the insertion of the transport module or transport container into the irradiation apparatus. Extremely thin transport cables are required for gamma or beta radiation sources, particularly for irradiation in the vicinity of the heart. Flexible sources having a highly flexible lead wire are advantageous in allowing radiation sources to be pushed through catheters having extremely small bending radii (FIG. 15). To prevent the transport cable from collapsing, for example, a transport-cable drive is proposed, with which even extremely thin transport cables can be driven without collapsing or looping. In this instance, the transport cable is wound onto or unwound from a storage drum known per se and having a cable-receiving groove that is covered at least partially by a pressing band; a novel pressing band on the part of the transport cable that is wound in spiral fashion onto the storage drum is wound onto the storage drum, extensively parallel to the transport cable (claim 4). The pressing band is comparatively narrow; the extension of its width only covers one winding of the transport cable. Thus, the transport cable can be wound in spiral fashion, in the axial or radial direction, onto the storage drum. Consequently, the pressing band presses the transport cable until it occupies a very small region directly in front of the point from which the transport cable is lifted from the storage drum into the cable-receiving groove. In contrast to the pressing bands known from the prior art, in this case the entire length of the transport cable that is wound onto the storage drum is pressed onto the storage drum, that is, into the cable-receiving groove, with practically negligible interruptions. To ensure that the cable is also guided without collapsing or looping in the region around the lifting point of the transport cable from the storage drum, a pressing roller and/or a cable-guiding part with which the transport cable can be lifted from the storage drum can be provided in this region. Of course, a pressing-band guidance of this type can be employed advantageously, independently of the use of a cable-receiving groove. Thus, a transport-cable drive is created that can reliably drive extremely thin transport cables, for example those that are necessary for preventing post-angioplasty restenosis through intra-arterial irradiation. In the region around the lifting point of the transport cable from the storage drum, the pressing band can be guided, for example by means of deflection rollers, around the storage drum in the opposite direction of the winding direction of the storage drum. This can prevent unnecessary crossings or deflections of the pressing band or the transport cable, and both the pressing band and the transport cable are extensively guided in a plane extending perpendicular to the shaft of the storage drum. For gentle handling of the radiation source and the transport cable in the presence of obstacles in the transport cable, and particularly in the event of operator's errors, the irradiation apparatus can include an impact sensor for monitoring the shearing force exerted on the transport cable (claim 9) a detection of obstacles in the transport channel is already known per se from EP-A1-0 278 829. Of course, this impact sensor can also be used advantageously, independently of the other features of the aforementioned irradiation apparatus. While the impact sensor can include any means for monitoring shearing force exerted on a cable, it is nevertheless advantageous for the impact sensor to include a region of the transport cable that is guided along a curve, as well as means for detecting a dislocation of the transport cable toward the outside of the curve (claim 8). Within the scope of this disclosure, the outside of the curve is understood to be the side of the cable facing radially outwardly from the curve. Any sensors, for example optical or electrical sensors, for detecting a dislocation can serve as means for detecting the dislocation of a cable. The use of a mechanical switching contact and/or a proximity switch is especially advantageous, however. If the radiation source or the transport cable impacts an obstacle as the radiation source advances, the transport cable in the region of the curve is dislocated toward the outside of the curve. The natural elasticity of the transport cable can suffice to prevent a dislocation of the transport cable toward the outside of the curve during normal operation, so the means for detecting a dislocation are not dislocated during normal operation. It can be advantageous, however, for the impact sensor to include elastic means that counteract a dislocation of the transport cable toward the outside of the curve. The shearing force to be exerted on the transport cable can be set by the selection of the spring constant. Examples of such elastic means include elastic-bending tubes that guide the transport cable. These tubes can also be rigid, but movable with respect to the rest of the transport cable, and can be connected to a retaining spring, for example a tension spring disposed on the inside of the curve. Of course, in a similar manner, a tensile-force sensor can be provided that monitors a dislocation of the transport cable toward the inside of the curve, for example. In such a case, elastic means can advantageously be provided that counteract the dislocation of the transport cable toward the inside of the curve. In the use of a sensor that supplies an analog output signal for deflecting the curved transport cable, it is possible to use a servo amplifier to drive an electromagnet as a restoring force such that the deflection can be kept as small as desired. In this case, the servo amplifier supplies the signal necessary for monitoring the shearing force. Of course, the transport-cable impact monitoring of the invention that has an impact sensor can also advantageously be used in irradiation apparatuses other than those described in claims 1, 3 and/or 4. A sensor having an analog output signal further permits a dynamic speed regulation: The shortest possible extension time (&lt;5 s) is necessary for minimizing the stress due to radiation. As the extension time increases, however, the frictional forces between the transport cable and the guide hose also increase, especially when the guide path has small radii of curvature. The nominal value of the extension speed of the transport cable can be regulated with the analog sensor signal, corresponding to the frictional force, such that the shearing force exerted on the cable does not exceed a (cable-dependent), specific maximum value. Thus, an overstressing of the transport cable and the guide hose is prevented at the highest-possible extension speed. The advancing movement is only interrupted if the maximum permissible shearing force is exceeded at the minimum permissible extension speed. This dynamic speed regulation can also advantageously be used in irradiation apparatuses other than those described in claims 1, 3 and/or 4. To prevent erroneous switches of the radiation sources, the transport container can include means, particularly electronic means, for identifying its associated radiation source (claim 9). Of course, these identification means can also be used advantageously, independently of the other features of the irradiation apparatus. In particular, these identification means can include an electronic memory, preferably a serial EEPROM (claim 10). Notably, it is possible to connect the rest of the irradiation apparatus with these identification means, particularly automatically, so the present radiation source can be identified by the irradiation apparatus, namely by its electronics. The identification means can also contain other data relating to the radiation source, such as initial activity and starting date, or the like. The identification means can also contain data relating to the transport container or the transport module. These data can be, for example, the length or strength of the transport cable. The identification means can likewise include data relating to the storage drum or the transport-cable drive, such as its radius or the number of path-indicator pulses per mm of extension path. In this way, high positioning precision is possible, despite low-cost production of the drive mechanics, which usually includes certain manufacturing tolerances, because the mechanical data can be compensated or settled by data contained by the identification means. The shield can include assemblies comprising tungsten for meeting even higher shield requirements and increasing export opportunities, because this material possesses no characteristic radiation. The aforementioned components are claimed and described in the exemplary embodiments, and are to be used in accordance with the invention, are not subjected to any exceptional conditions with regard to their size, shape, material selection and technical conception, so the selection criteria known in the respective field of use can be used without limitations.