WO2004017833A1

WO2004017833A1 - Positioning system for directional x-ray source relative to a detector

Info

Publication number: WO2004017833A1
Application number: PCT/NO2003/000272
Authority: WO
Inventors: Edgar Schriwer
Original assignee: Edgar Schriwer
Priority date: 2002-08-21
Filing date: 2003-08-11
Publication date: 2004-03-04
Also published as: AU2003256175A1; NO319348B1; EP1549219A1; NO20023987D0

Abstract

The invention relates to a positioning system for aligning of a directional x-ray source relative to a detector,the source being mounted on a carrier and the detector being adapted to be positioned inside a patients mouth for providing an x-ray image of the patients teeth. The system comprises detector holding means for keeping the detector in a predetermined position, said holding means also being provided with a reference feature for indicating the orientation and position of the detector inside the mouth, the reference feature being positioned at a chosen distance from the centre of the detector, alignment means coupled to the source at a chosen distance from the source centre for alignment relative to the reference feature, the alignment means being rotatably coupled to the carrier so as to adapt the position of the source to the orientation of the detector holding means.

Description

Positioning system for directional x-ray source relative to a detector.

This invention relates to positioning system for aligning of a directional x-ray source relative to a detector, the source being mounted on a carrier and the detector being adapted to be positioned inside a patients mouth for providing an x-ray image of the patients teeth

Current dental X-ray photo technique is based on the dental X-ray unit, known by most of us from dentist visits, in combination with a special X-ray film located between the patient's teeth. Increasingly more dentists are today using digital equipment including an x-ray detector to be positioned in the patients mouth in stead of the film.

During the dental X-ray examination, a so-called X-ray cone is positioned to the cheek, just outside the supposed position of the film. The diameter of the cone is approximately

50 mm, which open area is similar to that area supposed to exposure the film.

If the dentist, for some reason, aim at a slightly wrong position, the X-rays will miss the film, and all the teeth will not be exposed or will get a insufficient exposure, e.g due to the wrong angle of the x-ray source relative to the film or detector. There is a further risk of error if the X-ray cone is directed wrong in relation to the extension of the teeth, so that the x-ray beam does not hit the interesting areas and relevant information is lost.

The relevance of these problems have increased because of the digital sensors, which are more sensitive to misalignments of the source.

Optical systems for aligning the x-ray source are available, e.g. as described in patent publications Nos. JP 9313482, US 5553115, US 4887286 and FR 2614491. These publications, however, relates to systems for indicating the centre of the film or detector. As the film is positioned inside the patients mouth the centre is hidden, so that the positioning requires guessing of the orientation, which is not sufficiently accurate.

The existing digital x-ray equipment being manufactured by Op-d-op Inc under the name "sensor-pro" is provided with mechanicle means for aligning the x-rays source relative to the detector. This alignment means is, however, large and uncomfortable for the patient, and complicated for the dentist to assemble and use. It also requires a fairly large distance between the teeth when the patient closes his or her mouth over the sensor. Thus the relevant parts of the teeth are not all within the detector area.

It is an object of this invention to provide an inexpencive system for obtaining correct positioning and alignment of an x-ray source and a detector in an x-ray imaging system for teeth, the system comprising simple and small elements being easy to apply in the daily work of a dentist, and being comfortable for the patient.

The system according to the invention involves a number of components, which can simply be adapted to the dentists existing X-ray unit. This includes equipment for X-ray cone positioning in relation to the X-ray film, as well as a set of adapters for exact positioning of the X-ray sensor or film in the patients mouth. More specifically the system according to the invention is described in the accompanying claims.

The invention will be described below with reference to the accompanying drawings, illustrating the invention by way of example.

Figure 1 illustrates the system being utilized in a patients mouth.

Figure 2 illustrates a longitudinal section of the situation in figure 1. Figure 3 illustrates the outer rim of the cone of the source in one embodiment of the invention. Figure 4 illustrates the position of the x-ray cone opening and the detector relative to the patients teeth. Figure 5a,b illustrates holding means according to the invention. Figure 6 illustrates an alternative holding means according to the invention.

Figures 1 and 2 shows an x-ray source 1 being positioned in a carrier 2. Usually x-ray sources for dental uses are provided with a cone 3 for aiming the x-ray beam 12 toward the film or detector being positioned in the mouth of the patient. The source or cone will of course comprise means for emitting the x-ray beam during exposure and otherwise closing it for x-ray emissions. In the drawings the detector 7, as is usual with film according to the known art, is positioned in a holder 8 (see figure 5 a and 5b) being adapted to keep the detector in position in the patients mouth.

According to a preferred embodiment of the invention the invention the cone 3 is provided with at least one alignment means 4,5, one of which 4 being adapted to indicate the direction of the source by pointing at a reference feature 9 on the detector/film holding means 8.

The alignment means according to the invention is preferably a laser 4 attached to the cone 3 with a direction being essentially parallel to the x-ray beam and with a distance from the x-ray beam axis being indicative of the width of the x-ray beam. Although a laser is preferred an extendible rod may also be used, having the disadvantage of having to touch the reference feature 9 of the holding means 8, thus requiring cleaning and sterilization, or replacement of the tip 10 of the rod for each new patient.

The reference feature 9 indicates the position of the detector inside the patients mouth, e.g. by being positioned at the outer limits of the detector having a known size. It is also provided with a shape, which indicates the orientation of the detector or film in the mouth. In figures 1 ,2 and 4 the reference feature 9 is shaped as a flat part which also keeps the detector in position when the patient bites his or her teeth 6 together. Thus it also may indicate the occlusal plane 13 of the patients teeth. The flat part extends from the outer edge of the detector toward the centre of the detector and thus both indicates the detector orientation and secures the detector position so that an image of teeth both both in the upper and lower jaws is provided.

The reference feature 9 may of course have any other asymmetric shape indicating the orientation of the film or detector.

In order to improve the alignment the alignment means must be rotateable relative to the carrier, so that the source may be provided with the right position relative to the centre of the detector. The alignment will then comprise the steps of aligning the position of one alignment means 4 with the reference feature 9 of the holding device 8, and then to rotate the carrier relative to this axis so that the position of the source corresponds to the indicated position of the detector of film 7. Usually the source will be mounted directly to the carrier, but solutions in which the source rotates with the alignment means are also possible.

For improving the alignment the system may be provided with a second alignment means 5, preferably being position on the opposite side of the x-ray beam axis, also being essentially parallel to the beam. As the second alignment means is positioned on the opposite side of the x-ray beam centre it is easy to position and orient the x-ray beam. This is especially advantageous if the reference feature of the holding device 8 indicates the centre with a radial line, as is the case with the reference feature 9 in figures 1,2 and 4, since the line between the alignment means will correspond to the line indicated by the reference feature. In figures 3 and 4 the alignment means 4,5 are mounted on the outer rim of the cone having an orientation essentially parallel to the x- ray beam, thus indicating the outer borders of the x-ray beam.

Preferably this second alignment means 5 has a position which indicates the width of the x-ray beam at the patients chin.

In the preferred embodiment the alignment means are position on a cone being rotary relative to the source.

This equipment will cover all relevant types of dental X-ray pictures. Locating the X- ray cone to the cheek, it allows a precise direction orientation, using either the mechanical pointers 4,5, directed to the actual tooth, or using the optical aiming device describing two laser points or a laser line indicating the diameter of the X-ray cone. The at least one optical aiming devices may alternatively be adapted to project patterns other than dots or a line indicating the position and extension of the detector, such as lines or circles with known orientation relative to the aiming device.

The method allows a high degree of precision, and makes it possible to position the diameter of the X-ray cone exactly according to the occlussal plan or line 13. The method improves dental X-ray picture quality and increases diagnostic safety. More relevant information is being recorded, reducing the number of re-examinations. Time is saved and the patient is exposed to reduced X-ray doses.

According to another embodiment of the invention the holding means, as is illustrated in figure 6 is adapted to provide measurements of the roots of the teeth. Then the centre of the detector will not be positioned in the occlusal plane, as the e.g. will be positioned mainly in the upper or lower parts of the mouth in order to obtain sufficient coverage. In this case the reference features of the holding means will have another shape, essentially any asymmetric shape indicating clearly the direction from the reference feature to the centre of the detector. In the embodiment shown in figure 6 the reference feature 9 also constitutes a protection for the conductors 11 coupled to the detector 7. In this embodiment, the vertical or end face of the cone will lie in a plane parallel with the sensor when the first alignment means 4 corresponds to the position of feature 9.

It is an important aspect of this invention that the detector holding means 8 may be made in one piece, thus reducing the cost of the part of the system which is to be replaced after each use. These parts may be made using any suitable form of production method such as plastic moulding or similar.

The method may also be used for those still using film based analogue X-ray techniques, wherein the holding means is adapted to hold film.

Claims

C l a i m s

1. Positioning system for aligning of a directional x-ray source relative to a detector, the source being mounted on a carrier and the detector being adapted to be positioned inside a patients mouth for providing an x-ray image of the patients teeth, comprising: detector holding means for keeping the detector in a predetermined position, said holding means also being provided with a reference feature for indicating the orientation and position of the detector inside the mouth, the reference feature being positioned at a chosen distance from the centre of the detector, at least one alignment means coupled to the source at a chosen distance from the source centre for alignment relative to the reference feature, and wherein the alignment means are rotatably coupled to the carrier so as to adapt the position of the source to the orientation of the detector holding means.

2. System according to claim 1, comprising a second alignment means is positioned on the opposite side of the source.

3. System according to claim 1, wherein the alignment means is an extendible rod being adapted to make contact with the reference feature.

4. System according to claim 1, wherein the alignment means is a laser adapted to be aimed toward the reference feature.

5. System according to claim 1, wherein the source is provided with a cone for directing the x-rays from the source in a predetermined direction, the cone thus extending along the direction of the resulting x-ray beam, and that the alignment means are mounted on the outer rim of the cone having an orientation essentially parallel to the x-ray beam.

6. System according to claim 1, wherein the detector holding means is made in one piece.