X-ray or gamma ray systems or devices – Accessory – Alignment
Reexamination Certificate
2000-09-08
2002-12-10
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Accessory
Alignment
C378S206000, C378S197000, C378S198000
Reexamination Certificate
active
06491429
ABSTRACT:
The invention relates to a method of automatic guiding a C-arm X-ray device according to the concept of claim
1
.
A C-arm X-ray device (in the following called C-arm) is used routinely today for the intraoperative control of length and axial and rotational alignment of bones or bone fragments in osteosynthesis. In order to point out the task of the method according to the invention the step “intraoperative imaging” is described as technical regulatory process in the following section.
In conventional, open operative technique the surgeon receives his visual feedback partly via direct vision without radiography. Therefore, a separate operative step ‘intraoperative imaging’ cannot be delineated. In order to obtain a particular view of a fracture, the surgeon may have to alter his own position relative to the patient or the position of the retractor on the patient. The desired view of the fracture corresponds to the target value and the patient can be identified as the controlled system. The surgeon records with his eye (measuring unit) the current view of the fracture and compares it with the desired view. From the difference (control deviation), the surgeon (controller) determines, on the basis of his experience, the type and extent of the necessary positional alteration. As a result the surgeon achieves a new view of the fracture which is expressed in regulatory terms as the actual value. In a block diagram, this situation may be expressed as a simple control circuit with only three elements. An optimal regulatory behavior is achieved on the basis of direct visual feedback and a simple control circuit. This model can be applied to the description of soft tissue interventions and of those open osteosynthesis procedures at which the C-arm is not used.
If the surgeon obtains his visual feedback by intraoperative imaging with the C-arm, then intraoperative imaging can be delineated as an individual operative stage. This will be expressed in the following as a technical regulatory process for the constellation intraoperative imaging with the C-arm and image guidance with the combination C-arm/surgical navigation system.
lntraoperative imaging with the C-arm
For this constellation the external C-arm operator and the C-arm as a device must be taken into account as well as the patient and the surgeon in order to be expressed in regulatory terms. The representation in a block diagram therefore requires additional elements. The intraoperative positioning procedure can be described as a serial connection of one outer and one inner control circuit.
The outer control circuit includes all persons and appliances participating in the process, i.e. the surgeon, the C-arm operator, the patient, and the C-arm. Adjustment to the desired projection, in other words, the target value, is regulated by the outer control circuit. The current projection (actual value) is shown on the monitor of the image intensifier. The surgeon (controller) compares the desired and the current projection.
A projection is defined by the orientation of the rays relative to the object being imaged. For any desired projection, the C-arm must therefore take up a specific position relative to the imaged fragment. The surgeon can only tell his description of the desired position in somewhat inexact terms and this depends upon his experience (interpreter). He communicates the position to the C-arm operator. The operator of the C-arm, the patient and the C-arm correspond to the outer control circuit as the controlled system which the surgeon influences as controller.
On the other hand, the interaction between the operator of the C-arm, the patient and the C-arm can be described as a second, inner control circuit with which the correct position of the C-arm is achieved. The operator tries to move the C-arm to the position stipulated by the surgeon. The C-arm operator acts as a controller in that he compares the position stipulated by the surgeon (target value) with the existing position of the C-arm (actual value). On the basis of his experience (interpreter), he plans suitable corrective movements. These may or may not be possible due to circumstances such as limited space or concerns for sterility (=disturbance factors). The actual position is constantly registered by the C-arm operator by eye (measuring unit), i.e. he receives continuous direct visual feedback. Only when the operator is satisfied with the position of the C-arm and the regulatory process in the inner control circuit is completed does the surgeon receive his first, delayed, visual radiographic feedback (measuring unit C-arm). Before the desired projection appears on the screen, the above procedure may have to be repeated several times.
The entire process has to be repeated in the same manner in order to reproduce a projection.
Intraoperative imaging with the combination C-arm/Surgical Navigation System
Surgical navigation systems make possible continuous image guidance based on stored data. This is done by representing the spatial relationships between surgical instruments and anatomical objects of interest on the screen. A surgical navigation system includes a facility for recording the position of the instruments in the operation room as well as the software and corresponding hardware components. This operates on a transceiver principle: on each surgical instrument transmitters tuned to the receivers are permanently mounted. Their position in the operating theater tracked by the receiver and positional information transmitted to the navigation system. Before each application of the surgical navigation system digital images of the patient are copied from an imaging unit (CT, C-arm) to the navigation system. The positional data on surgical instruments and anatomical objects in the OR make it possible to generate a simulated projection of the current position of the instruments on the recorded digital images.
The combination of surgical navigation system and C-arm can be applied during trauma surgery in the modes “positioning of the C-arm” and “image guidance”. In the “positioning” mode the navigation system helps the surgeon to place the C-arm correctly for a previously defined projection. To do this, the relative position of the C-arm with which the desired projection will be achieved and the object to be imaged (implant or fragment) are stored in the navigation system. lntraoperatively, the actual positions of C-arm and object to be imaged are tracked and from them the relative positions are calculated. Consequently, the target and the actual relative positions are imaged on the monitor of the navigation system.
To express this situation in terms of automated control engineering, the navigation system has to be taken into account. In the ‘positioning’ mode, it functions to set the target value for the surgeon. He can thus give more exact positional commands to the external operator of the C-arm. The navigation system is however not linked into the inner control circuit with which the positioning of the C-arm is controlled.
Even in this configuration the total process must be repeated as described if a previously set projection is to be reproduced.
In order to achieve an optimal handling procedure, the surgeon must be able to alter the position of the C-arm - and thus the visible image—independently and immediately. This requirement is not fulfilled if a C-arm is used with the usual equipment available today for intraoperative imaging: the device is operated and positioned by a third person. This procedure takes time, is open to error, and leads to additional difficulties:
The entire procedure for setting up a projection has to be repeated if the projection needs to be reproduced, for example, when checking a reduction manoeuvre.
The radiographic checks necessary for positioning represent an additional exposure to radiation for the patient and the team in the operation room.
The person operating the C-arm has to be available more or less throughout the operation even though assistance may only be required occasionally after long waits.
These problems
AO-Development Institute Davos
Kao Glen
Kim Robert H.
Rankin, Hill Porter & Clark LLP
LandOfFree
Method of automatic guiding a C-arm X-ray device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of automatic guiding a C-arm X-ray device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of automatic guiding a C-arm X-ray device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2992284