Referencing device including mouthpiece

Details Referencing device including mouthpiece Referencing device including mouthpiece

1998-04-07

2001-04-24

Casler, Brian L. (Department: 3737)

Surgery

Diagnostic testing

Detecting nuclear, electromagnetic, or ultrasonic radiation

C606S130000, C378S170000, C378S205000

Reexamination Certificate

active

06223067

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a referencing device for mapping the position of bodily surgical or examination target points comprising at least three reflectors, the position of which can be localized by a computer-assisted position tracking and/or a CT scan, and an adapter connected to the reflectors, by means of which the referencing device is attachable to a part of the body, wherein said adapter comprises a mouthpiece securable to said upper jaw by means of vacuum pressure.
The invention relates furthermore to a method for referencing bodily surgical or examination target points. The device in accordance with the invention is employed in radiotherapy and neurosurgery.
2. Description of the Prior Art
Referencing devices which make visible the current position of the patent as well as the three-dimensional position of surgical instruments and hardware on a computer monitor or which contribute towards directly mapping positions in radiosurgery are known. They serve to reference the anatomical data obtained for example by a CT scan in a fiducial system, i.e. permitting three-dimensional assignment of the patient anatomy to the referencing device in each case which in turn can be tracked by a position tracking system for monitoring in the operating room. Position tracking systems of this kind comprise for example an infrared emitter and two infrared cameras which “see” the three-dimensional position of reflectors attached to the patient or to the surgical instruments and hardware. In this arrangement a computer assigned to the position tracking facility computes from the information on the reflector position the up-dated or current position of the patient as well as that of the surgical instruments and hardware and assigns this information to the patient data from the CT scan thus making image-assisted navigation in the operating room or computer-assisted radiotherapy possible.
To enable the anatomy of the patient as established from the CT scan in the above systems to be mapped as precisely as possible artifical landmarks are attached to the patient prior to scanning, the images of which are mapped in the CT. In actual surgery the positions of such landmarks are tracked by a position tracking system as described above, for instance, and thus due to the fixed assignment of the patient anatomy to the position of the landmarks the current position of the surgery target points is also known via the known position of the landmarks.
The landmarks can be principally attached to the patient invasively or non-invasively. Invasive methods of attachment, for example, trephining and securing the landmarks in the holes are highly accurate but extremely stress the patient. Noninvasive methods involve, for example, attaching the landmarks to the skin by means of surgical plaster. The drawback here is that the skin is prone to being slightly shifted which in a worst case condition may amount to a few centimeters resulting in position tracking with such bonded landmarks being inaccurate.
Known from German Patent 19 619 761 A1 is a locating device for the human head in which an upper jaw impression mold is applied to the patient which can be affixed to the upper jaw by vacuum pressure. Applying this upper jaw impression mold in the mouth of the patient merely serves to precisely locate the head of the patient; however, the upper jaw impression mold for locating the head is totally rigid and unmovable in use.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a referencing device for mapping the position of bodily surgical or examination target points featuring high positional fidelity, it also being an object to provide a corresponding referencing method.
This object is achieved in accordance with the invention by the adapter, by means of which the referencing device can be applied to a part of the body, comprising a mouthpiece attachable to the upper jaw by vacuum pressure.
The advantage of the present invention lies particularly in the possibility of referencing surgery target points precisely reproducible without excessive patient stressing. Securing the adapter and thus the reflectors via a mouthpiece to the upper jaw allows high position fidelity every time the mouthpiece is returned in place due to the characteristical shape or each upper jaw or dental impression of the patient. This means that the reflectors attached to the mouthpiece can be relocated highly accurately in the same spacing and locational relationship to the patient anatomy every time the referencing device is returned in place.
Having to put up with a major displacement as is the case with landmarks attached to the skin is now obviated.
In addition, locating the mouthpiece by vacuum pressure is relatively pleasant for the patient and although the attachment is sufficiently rigid it can be released at any time without any injury to the patient.
In one advantagous aspect the adapter comprises an upper jaw impression mold which is filled with a settable impression compound. This known impression mold permits relatively fast and highly accurate modelling of an upper jaw or dental impression. Such an upper jaw impression mold can be reinserted in the mouth of the patient at any time in a reproducible location, the upper jaw impression mold preferably covering the dental area and the hard palate of the upper jaw.
A dental impression provides a highly characteristical anatomical image of the patient for reproducible attachment. When, in addition, an impression of the hard palate is made this enhances, on the one hand, the stability with which the mouthpiece is secured to the patient and, on the other, opens up the possibility of making use of the mouthpiece also in the case of patients having no teeth (due to age or an accident).
In a preferred embodiment of the referencing device in accordance with the invention scallops are provided in the surface region of the set impression compound which leave an air space between the hard palate and the surface of the impression compound with the mouthpiece in place, this air space permitting a vacuum pressure to be applied. Due to such an air space which may be produced, for example, by implanting an insert in the impression compound during setting, the possibility of vacuum pressure securement is easily created. When the air space is brought into connection outwardly with a vacuum pump the air can be exhausted from the air space with the mouthpiece in place, as a result of which the mouthpiece comes into intimate, firm contact with the upper jaw.
Preferably the reflectors of the referencing device are removably appliable in a characteristic array.
Removable reflectors permit, on the one hand, the facilitated replacement of the reflectors for a CT scan by the reflectors which can be localized by a navigational means in the operating room, they on the other hand permitting simple means of sterilization at no great expense by presterilized reflectors being applied, for example, just before commencement of an operation.
A characteristic reflector array existing only on the mouthpiece enables the navigating means in the operating room to explicitly differentiate this reflector array from other reflector arrays (for example on surgical instruments and hardware), here too, it being possible to explicitly assign the location of the surgery target relative to the characteristic reflector array on the mouthpiece.
In the method in accordance with the invention for referencing bodily surgical or examination target points the position of at least three reflectors is tracked by computer-assisted position tracking and/or a CT scan whereby the reflectors are attached by means of an adapter to the part of the body concerned. The referencing device is secured via a mouthpiece serving as the adapter and locatable on the upper jaw by means of vacuum pressure.
The method in accordance with the invention can be implemented with all of the embodiments of the referencing means as discussed above.
The invention relates also to the use o

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