X-Rays Get a Lift with Robotic Arms

Known as the Multitom Rax, the scanner, which was recently introduced at the Universitätsklinikum in Erlangen, Germany, offers several benefits. Its automatic movement saves time and provides for a safer environment, because its arms position themselves at the correct angle to one another,, thus obviating the need to shift the patient. Instead, the detector and tube are repositioned. These elements automatically move to their destinations along the shortest, fastest, and safest path while ensuring that they are always at the right distance and angle to one another. This saves time and minimizes the risk of incorrect positioning.

No need to move patients to different beds.
The scanner is also highly versatile. In addition to radiographic- examinations, fluoroscopic imaging (video sequences), selected angiographic applications, and even three-dimensional images are possible. This saves time because patients do not need to be moved from room to room or bed to bed for different exams.

The new scanner thus allows small hospitals to cover a broader range of examinations with just one machine. On the other hand, it allows large hospitals to reduce the load on their special-purpose equipment, or even cut down on the number of rooms and systems they use.

Imaging a weight-bearing knee.
X-ray systems that have a moving X-ray tube mounted on the ceiling are already available. With such systems, however, an operator often has to place the detector in a special fixture by hand and then adjust its position manually. Multitom Rax performs most of these examinations at the push of a button.

And with the freely moveable detector, even more is possible. If necessary, for example, one can perform a 3D examination of a knee. With its cone beam technology, the tube emits a defined cone of rays, and each detector segment registers an X-ray value corresponding to one beam angle. The tube and detector circle the target and record an image sequence that is then combined to form a 3D representation. Using this technique, Multitom Rax even enables 3D examinations to be carried out under natural weight-bearing conditions for the first time. In the case of the knee, for instance, an examination can be performed while the patient is standing – something that is not possible with conventional CT scanners.

Multitom Rax is also suitable for fluoroscopic examinations, in which doctors observe processes in the body in real time during X-ray imaging. One typical application is the examination of swallowing and digestive processes, for which the patient swallows a contrast agent. The X-ray detector used in the Multitom Rax operates with sufficient speed to permit real-time recordings of this kind and is already being used in other machines for this purpose.

High-precision robotics.
With a view to optimizing the movements of the robotic arms, Siemens developed navigation software in which typical settings for the tube and detector are defined, or can be defined by hospital personnel, for various X-ray examinations. A record of the spatial conditions is kept for the individual sites at which the system is used. This includes information about stationary obstacles such as cabinets or posts. As soon as the operator at selects a given examination, the robotic arms calculate the fastest path to the required position and go to it by themselves.

The arms travel at a speed of 0.6 meters per second, and each controls its five axes simultaneously, instead of executing one movement after the other, as is common in many systems. Once they have arrived at their positions, only fine adjustments are required by the operator. Servomotors in the robotic arms ensure that this is possible without great effort. One special feature is that the robotic arms can go to a new location from any position without having to first go back to a defined initial position. This enables the machine to switch from one examination to the next more quickly.

The arms only move when the operator has his or her hand on the control panel or the remote control. This prevents collisions with people. Furthermore, the robot immediately detects when it encounters an obstacle and stops automatically. In order to minimize the system’s structural requirements, the robotic arms have an extremely lightweight design In addition, the arms use special, built-in strain wave gears that have practically no play and allow extremely precise positioning. This is especially important for 3D imaging, where the placement of tube and detector must be accurate to within a tenth of a millimeter.

Mr. Dr Norbert Aschenbrenner
Editorial Office
Siemens AG

Original Internet Article:

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