RADIATION MONITORING DEVICE PROVIDED WITH MEANS TO MEASURE AN ADMINISTRATED DOSE IN A TARGET AREA

Technical field

The present invention relates to a radiation monitoring device for locating a target area and measure an administered dose, provided from a radiation source, in the target area.

Background to the invention

Today the administered dose is normally only measured on the outside of the human body during radiotherapy. Due to the lossy nature of the human body the radiation starts to disperse.

There already exists a directive in Denmark with the object to ensure that it should be possible to measure the dose if an irradiation source is used. This regulation is projected to be adopted by other countries, such as France, and it could also become a standard regulation for radiation treatment.

In an article with the title "An implantable radiation dosimeter for use in external beam radiation therapy", by Charles W. Scarantino et al., published in American Association of Physicists in Medicine, September 2004, pages 2658 - 2670, a method for measuring administered dose in a target area is disclosed. An implantable radiation dosimeter is introduced into a living body and telemetrically read using inductive power on a daily basis, i.e. before and after a radiotherapy session. A disadvantage with the disclosed system is that it is not possible to monitor the administered dose during each radiotherapy session and therefore can not be used to control the amount of radiation the patient is subjected to during radiotherapy. Another disadvantage is that the dosimeter can not be removed from the patient after completion of the radiotherapy without a surgical operation.

Summary of the invention

An object with the present invention is to provide a radiation monitoring device that is provided with means to determine a position of a target area and that measures the administrated dose of radiation during a radiotherapy session in the target area, and therefore may achieve a more accurate level of radiation in the target area of a patient compared to prior art.

The object is achieved by a device which is fixated relative a target area within a living body. The radiation monitor device comprises in addition to a dose measuring device an internal element used to track variations of a position of the device in relation to a radiation source arranged outside the target area. The purpose of the dose measuring device is to detect an administered dose in the target area from the radiation source.

An advantage with the present invention is that the actual administered dose inside a target area could be more or less continuously detected, depending on the sampling rate of the measuring equipment.

Another advantage with the present invention is that a cumulative administered dose can be calculated for a patient which will increase the possibility to monitor the administered dose during a series of radiation treatments.

Still another advantage is that the present invention is cheap and easy to implement. Furthermore, the quality of the treatment may be documented and also improved.

In a further embodiment the radiation monitoring device is implemented as an implant, wherein the administered dose in a target area inside a living body may be monitored.

In an alternative embodiment, the radiation monitoring device is implemented as a skin adhering item, such as a plaster, wherein the

administered dose in a target area situated close to the skin of a patient may be monitored.

Further objects and advantages will be apparent for a skilled person from the detailed description and the drawings.

Brief description of the drawings

Fig. 1 shows a schematic view of a first embodiment of a radiation monitoring device in a living body.

Fig. 2 shows a block diagram of a first embodiment of a dose measuring unit in the implant of figure 1.

Fig. 3 shows a cross-sectional view of a second embodiment of a radiation monitoring device in a living body.

Fig. 4 shows a block diagram of a second embodiment of a dose measuring unit in the radiation monitoring device of figure 3.

Fig. 5 shows a cross-sectional view of a third embodiment of a radiation monitoring device.

Fig. 6 shows a cross-sectional view of a fourth embodiment of a radiation monitoring device.

Fig. 7 shows a cross-sectional view of a fifth embodiment of a radiation monitoring device.

Fig. 8 shows a perspective view of a sixth embodiment of a radiation monitoring device.

Fig. 9 shows a system implementing a monitoring device according to the invention.

Fig. 10 shows a plot illustrating the near field effect of electromagnetic signals.

Fig. 11 shows a system with an alternative implementation of a monitoring device according to the invention.

Detailed description of the preferred embodiments

Radiotherapy normally contains several radiation sessions, for instance between 8 and 35, spread out during a predetermined time period for treating cancer, e.g. prostate cancer, and each radiation session comprises normally several fractions during which the patient is subjected to radiation. Prior art suggest how the administered dose can be measured between each radiation session, and the present invention also provide a means to measure the administrated dose between each fraction or even during a fraction. This will improve the possibility to more accurately monitor the administrated dose and furthermore, limit the patient's exposure to radiation, since the predetermined dose, e.g. 70-100 Gray, can be used to control the amount of radiation in a present or subsequent fraction.

Figure 1 shows a schematic view of a first embodiment of a radiation monitoring device 2, in this embodiment an implant, in a living body 10 of a patient. A bio-compatible cover 4, such as a catheter, is provided either through the tissue or through a natural opening in the body. The procedure of inserting the catheter is common knowledge of a skilled person in the art, e.g. Seldinger technique.

The catheter is inserted into, or near by, a target area 1, e.g. a cancer tumor. A dose sensor 3 is inserted into the catheter 4 and is connected through wires 5 to an externally arranged dose conversion unit 6. The dose conversion unit 6 is preferably provided with an electronic ID, or a written ID-label 7 (printed or hand written), and is described in more detail in figure 2.

The dose conversion unit 6 converts the signal from the dose sensor to an amount of administrated dose generated by the radiation source and is preferably fastened to the outside of the patient using an adhering material,

such as a plaster. The conversion unit is in turn connected to a control equipment (not shown) through a connection 8 for analyzing the measured dose by the measuring unit 6.

When the treatment of the patient is completed, the catheter including the dose sensor 3 is thereafter removed from the patient and no part of the implant 2 is left in the living body in this embodiment after completion. The catheter is constructed in such a way that it is held in place during the radiation treatment, but may easily be removed when it is completed. An example of fastening mechanisms is a multiple of tine elements such as disclosed in the published US application US 2006/0129218, assigned to

Medtronic, Inc. Such fastening mechanisms are known to a person skilled in the art and are therefore not described in more detail.

Figure 2 shows a block diagram of a first embodiment of a dose conversion unit 6 in the implant of figure 1. The dose sensor 3, such as at least one diode, is arranged inside the catheter (not shown) and is connected through wires 5 to an integrator 11 that continuously measures the administrated dose. The integrator 11 could for instance be an op-amp (operational amplifier) with a capacitor in its feedback loop, and a certain level of irradiation results in a certain level of DC (Direct Current) voltage. If a diode is used, it normally needs to be pre-radiated to create a linear response from the diode.

The integrator 11 is connected to a processing unit 12 which comprises a microprocessor μP, and an internal memory M, but an external memory may naturally be used instead. The processing unit 12 receives information from the integrator 11 regarding the administered dose during a treatment and may forward this information to a control equipment 13. The control equipment may use this information to in turn control the amount of radiation irradiated on the target area by a radiation equipment (not shown) . A cumulative value corresponding to the total measured administered dose

is also calculated and stored in the memory M. The calculations are preferably performed within the microprocessor μP,

Each dose sensor is normally tested and characterized before use and calibration information is obtained to provide a simple normalized interface between the dose conversion unit 6 and the external control and radiation equipment. This information may be stored in the memory M or stored externally, but it needs to be accessible to provide a means to interpret the measured dose and translate it into an absolute value of administered radiation in the target area 1.

An electronic ID tag may also be stored in the memory M together with information regarding the scheduled radiation treatment for the patient. This information may be used to further ensure that the right amount of radiation is given to the correct patient by comparing the entered ID on the radiation equipment and /or control equipment and comparing it with the stored ID in the memory of the dose conversion unit 6.

Figure 3 shows a cross-sectional view of a second embodiment of a radiation monitoring device 20, in this embodiment an implant, in a living body 10. The catheter 21 is in this example introduced through a natural opening and will assist in determining the administered dose when treating for instance prostate cancer. An inflatable balloon 22, which is part of the catheter 21, helps to securely position the implant relative a target area 1. A dose conversion unit 23 is arranged within the catheter 21 within the target area 1. The catheter is removed after each treatment occasion by deflating the balloon and removing the implant 20. If the catheter is provided with a through going opening, such as a lumen, the bladder may be emptied even though the catheter is maintained in position.

Figure 4 shows a block diagram of the second embodiment of a dose conversion unit 23 in the implant of figure 3, and comprises in this example a transmitter T _x used for determining the position of the target area 1 (and

thus the dose conversion unit 23), as is disclosed in the international publication WO 2005/ 104976, which is assigned to the same applicant.

The dose conversion unit 23 further comprises a sensor S, a microprocessor μP and a memory M. The sensor includes in this embodiment at least one MOSFET preferably, but not necessarily, connected to an op-amp. The

MOSFET does not have to be pre-radiated and an integrator is not needed since the MOSFET measures the absolute dose after completed irradiation of the target area 1.

The dose conversion unit 23 is further connected to a control equipment 24 which is provided with antennas (not shown) to determine the position of the transmitter T _x . Signals are generated in the control unit 24, transmitted to the transmitter T _x which emits signals that are received by the antennas to determine the position of the target area 1. This system has been disclosed in the above mentioned WO 2005/ 104976 and is briefly described together with the present invention in connection with figure 9.

An electromagnetic signal having a frequency within the range of 5-350 MHz is generated in a control unit 71 and is thereafter transmitted from at least one transmitter 72, included in a radiation monitor device 79 according to the invention, arranged in relation to a target area 73 inside a living body 74. The electromagnetic signal is adapted to propagate with a wavelength in the body 74 and, in a first example, a phase difference of the electromagnetic signal is detected in at least three positions 78, preferably four or more positions, by a receiver 75 arranged outside the body 74. The wavelength is selected so that a distance from the transmitter 11 to each of said at least three positions 78 is within the same integer number of wavelengths of the electromagnetic signal. The distance between each transmitter 72 and the positions of the receiver 75 is preferably selected so that they operate in a near field region. In this example a radiation source 76 is arranged outside the body 74 and preferably connected to the control unit 71. The radiation beam 77 of the radiation source 76 is concentrated to a treatment area.

Furthermore, the transmitter 72 is in this embodiment arranged within the target area 73, which in this example is identical to the treatment area of the patient.

The behaviour of an electromagnetic signal in the near field region is known for a skilled person and is described in a publication with the title "Near field Phase Behavior", by Hans Gregory Schantz, IEEE APS Conference July 2005. In this publication the author presents a reprint of a plot published in "Electric waves", by Heinrich Hertz, London, Macmillian 8B CO. 1893, page 152 and a plot, shown in figure 10, was published by Q-track in 2004.

The plot describes the phase behaviour of the magnetic field (H-field) and the electrostatic filed (E-field) below one wavelength of an electromagnetic signal. In this near field region of an antenna, the magnetic field and electrostatic field phases radically diverge, and in a far field region, many wavelengths away from a transmit antenna, the magnetic and electrostatic field move with perfect synchronized phase. Figure 10 illustrates the effect of the near field region, and the phase delta between the magnetic field and electrostatic field at zero λ is 90 degrees, which decreases to a phase difference of 0 degrees at one λ.

The separation of the magnetic field and the electrostatic field in the near field region opens up a number of possibilities to construct improved measurement systems. The shape of the wave front of the electromagnetic signal may be used to determine the distance between the transmitter and the receiver. It is also advantageous to increase the sensitivity of the measurement system by introducing electrostatically shielded antennas, which is possible since the magnetic field and electrostatic field are separated in the near field region, whereby the magnetic field is used to determine the variations of the position of the transmitter.

A more detailed description of the detector system may be found in the international patent application with the publication number WO 2005/ 104976, which is hereby incorporated by reference.

In a second example, amplitude difference of the electromagnetic signal is detected instead of the phase difference as described above in connection with figure 9. At least one transmitter 72 arranged in relation to a target area 73 inside a body 74 transmits a signal having a frequency within the range of 1 kHz-350 MHz and an amplitude difference from the transmitted signal is detected by a receiver 75 at three, or more, positions 78 to track variations in position of the transmitter 72. The amplitude of the magnetic field is preferably measured when operating in near field, for instance by measuring absolute value or mean value of the magnetic field.

It is of course possible to combine the above described examples and use both phase and amplitude difference to determine variations of the position of the transmitter 72 in relation to the positions 78 of the receiver 75.

The receiver 75, comprising a multiple of antennas in at least three separate positions 78 (in this example four positions), is positioned on the outside of the body and is also connected to the control unit 71 , and a very accurate tracking of the transmitter 72, and thus the target area 73, may be performed.

In an alternative embodiment signals are transmitted from at least one externally arranged transmitter, and the electromagnetic signal is received by a receiver inside the radiation monitoring device. The receiver comprises three antennas in at least three separate positions. The separate position of the antennas of the receiver may be accomplished by moving the antenna in a predetermined pattern, or by providing three or more antennas.

Fig. 5 shows a cross-sectional view of a third embodiment of a radiation monitoring device 30, in this embodiment an implant, comprising a catheter 31 provided with a mechanical guide 32 and a marker 33. The marker 33 is visible when the implant is subjected to x-ray radiation. The implant further comprises a combined dose and positioning unit 34 having a transmitter T _x used to determine the position of the target area in a patient, and a dose sensor 35 used to detect the amount of administered dose in the target area.

The combined dose and positioning unit 34 is provided with a guide element 36 that is arranged to be able to mate with the mechanical guide 32 and will ensure that the unit 34 is held in the correct position during radiation treatment. The combined dose and positioning unit 34 is connected to an externally arranged integrated circuit 37 through wires 38, and may also be withdrawn from the catheter 31 between the treatment occasions. The integrated circuit 37 includes the functionality needed to perform the dose conversion as previously described in connection with figures 1-4.

In an alternative embodiment, the transmitter T _x is omitted and the marker 33 is used as a positioning device during radiation, since the marker 33 is visible when the monitoring device is subject to x-ray radiation. A positioning system using implanted markers has been proposed by Initia Medical Technologies.

Fig. 6 shows a cross- sectional view of a fourth embodiment of a radiation monitoring device 40, in this embodiment an implant, and comprises a catheter 41 provided with an electrical guide 42 and an electrical marker 43. The marker 43 comprises a transmitter T _x used to determine the position of the target area in a patient and an identification ID of the patient. The implant further comprises a combined dose and identification unit 44 having a dose sensor 45 used to detect the amount of administered dose in the target area and a dose identification Dose/ ID.

The combined dose and identification unit 44 is provided with a connector 46 that is arranged to be able to connect to the electrical guide 42 and will ensure that the correct unit 44 is connected by comparing the dose identification Dose/ ID and the ID of the patient in the electrical marker 43, and verify that it is held in the correct position during radiation treatment since the transmitter T _x is powered through the combined dose and identification unit 44. The combined dose and identification unit 44 is connected to an externally arranged integrated circuit 47 through wires 48, and may also be withdrawn from the catheter 41 between the treatment

occasions. The integrated circuit 47 includes the functionality needed to perform the dose conversion as previously described in connection with figures 1-4,

Figure 7 shows a cross-sectional view of a fifth embodiment of a radiation monitoring device 50, in this embodiment an implant, which comprises of an insertable member 51 arranged to be inserted inside a living body 10 and an external communication unit 52. The insertable member 51 may have any desired shape as long as it can supply certain functions, and in this embodiment it has an elongated shape. In a first end 53, positioned inside a target area 1, the member 51 is provided with a dose conversion unit 54 including a dose sensor S and a transceiver T _x / R _x for tracking variations of a position of the implant relative to at least one externally arranged antenna element (not shown), an example of such a system is disclosed in the international publication WO 01/34049.

In a second end 55 the insertable member 51 is provided with an internal communication unit 56 having an energy source, such as a battery, which provide energy to the dose conversion unit 54. The internal communication unit 56 is connected to the dose measuring unit 54 by wires 57 and the insertable member 51 is provided with a protective cover 58, preferably a coating made of silicon, which surrounds all the parts of the insertable member 51. Instead of having an energy source provided in the internal communication unit, an electromagnetic coupling to an external energy source may be used.

The external communication unit 52 is provided with means to wirelessly communicate with the internal communication unit 56, whereby a noninvasive measurement of the dose and tracking of the implant may be achieved. The external communication unit 52 is connected to an external control unit 59. A memory (not shown) provided with information regarding calibration information and ID of the patient may naturally be provided both in the insertable member, e.g. in the internal communication unit 56, and in

the external communication unit 52 to further simplify the interpretation of the measured dose and to ensure that the correct patient is subjected to radiotherapy.

Figure 8 describe a sixth embodiment of a radiation monitoring device 60, such as a skin adhering item, e.g. plaster. A similar device has been disclosed in the co pending Swedish patent application SE 0502273-6, filed October 14, 2005 and assigned to the same applicant. The plaster 60 may be fastened on the skin of a patient very close to the area where the target area is situated, and comprises in this embodiment two transmitters 61 and 62 in a central part of the plaster 60 and two adhesive portions 63 to securely attach the plaster to the skin. The transmitter 61, 62 are connectable to a control Equipment through wires 64. The central portion of the plaster is further provided with a dose measuring device 65, comprising a dose sensor, a dose conversion unit and a memory similar to the devices described in connection with figures 1-4.

The plaster could, for instance, be used when a patient having breast cancer is exposed to radiotherapy treatment. The plaster 60 is then attached to the breast in such a way that a relative distance between a target area in the breast and each transmitter 61 and 62 is established. The breathing of the patient, and thus the movement of the breast due to the breathing, can be tracked, and the radiotherapy treatment can now be controlled more accurately by adapting the exposure dose to the position of the target area and the measured administrated dose. More than one plaster, each having a dose measuring device and positioning means, may naturally be used to more accurately control the radiotherapy treatment. Furthermore, it is of course possible to have more than one dose measuring devices, without deviating from the scope of the invention as defined in the claims.

Figure 11 shows a system with an alternative implementation of a monitoring device according to the invention. The hardware of the system could be identical to the system described in connection with figure 9, but a

system adapted for brachytherapy is shown in figure 11. The radiation source, in the form of seeds 82, is configured to be introduced inside a treatment area 81 using catheters 83, or needles, instead of exposing the treatment area 81 to x-ray radiation using an externally arranged radiation source 76 as shown in figure 9. The radiation monitoring device 79 is in this implementation arranged in a target area 84, which is a vital organ adjacently arranged to the treatment area 81. The vital organ in the target area 84 should be exposed to a minimal radiation dose, and by monitoring the administered dose in the target area 84 when treating the treatment area 81 the amount of radiation emitted from the radiation source 82 may be controlled. In other words, the vital organ is arranged in a non-treatment area. A positioning device 85, which controls the actual position of the tip of the catheter 83, and thus the radiation source 82, is preferably connected to the control unit 71.

Other types of sensors may naturally be added in the radiation monitoring device to further monitor other data from the target area, such as pressure, pH, temperature, oxygen saturation, drug concentration, etc. which implementations are obvious for a skilled person in the art and will therefore not be described in more detail.

In the above described embodiments, electromagnetic signals have been described to determine the position of the radiation monitoring device, but the scope of the invention should not be limited to this. A magnetically excitable internal element that communicates with at least one externally arranged detector is also possible.

The above described embodiments of the invention exemplifies the inventive concept any combination of the described embodiment is conceivable. Thus, the scope of the invention should not be limited to the specific embodiments.