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Jena University Hospital Researches RFID Tracking System for Instruments Inside the MRT

Use Cases | By PR RFID im Blick | 11 December 2013
The open construction of modern magnet resonance tomographs allows minimally-invasive surgery guided by real time imaging. The open construction of modern magnet resonance tomographs allows minimally-invasive surgery guided by real time imaging. Photo: amedo smart tracking solutions GmbH / Universitätsklinikum Jena

Minimally invasive surgery guided by real time imaging

By means of magnetic resonance tomographs (MRT), sectional images of the human body can be taken on a freely definable image plane allowing function and structure examination of tissue and organs. Modern MRTs' open construction furthermore enables minimally invasive surgery guided by real time imaging. Still usually only hydrogen atoms are detected in an MRT, instruments are invisible for imaging outside the body, which is why they need to be integrated into the imaging system using tracking solutions for instance. Previous optical solutions are time-consuming and most of all hard to handle. In a project promoted by the DFG the working group „Translationale Forschung (translational research)“ (Tra-Fo) of the centre for radiology (director Prof. Ulf Teichgräber) at Jena University hospital examines the suitability of an RFID based tracking system – with first positive results, as reports Felix Güttler, computer scientist and director of the Tra-Fo working group in the interview with „RFID im Blick“.

By Sebastian Krings, „RFID im Blick“

Disadvantages of optical systems

Currently optical systems are the common method of determining instrument positions inside the MRT. As part of this procedure infrared cameras detect markers mounted on the instrument reflecting particularly this field of light. „Although recent systems are very precise, they have a number of disadvantages“, says Felix Güttler. „The radius of optical tracking systems is very limited and as soon as visual contact between camera and marker is interfered the positioning is interrupted. This is not unusual because access to the patient is very limited anyway due to the little room inside the MRT. Furthermore the markers which are to be mounted on the instrument are often quite big and unfortunately also very unhandy because of their weight. Last but not least the markers are unsuitable for sterilization and replacement can be very expensive.“

Transponders allow instrument localization and identification

Since 2010 the team of intermediately six people directed by Felix Güttler has been testing and adapting the prototype of a UHF RFID based instrument tracking system provided by the company Amedo Smart Tracking Solutions. Based on radio wave communication between RFID transponders and transmitter the system detects the instruments' position. „We mounted four antennas in the room and installed three transponders as spacial reference point permanently on the MRT. In order to integrate the instrument imaging into the MRT imaging we converted the RFID coordinate system accordingly and determined the axis of the beam's overlap (isocentre) in a single procedure. Every instrument is equipped with three transponders which the system uses to detect the instrument's position within the whole room after one-time registration. The transponders contain an unmistakable ID inside the microchip which is linked to the respective instrument by a specifically developed middleware“, as explains Felix Güttler. Thereby, according to Amedo, besides positioning, clear allocation and identification of different instruments can be put into practice as well.

Amedo Tracking Server for UHF RFID transponder measuring
Amedo Tracking Server for UHF RFID transponder measuring

Position accuracy of up to three millimeters

With the project the working group proved successfully that RFID does not affect imaging in the MRT which is also due to the high frequency difference. Thus RFID is basically suitable for tracking system application. There are many practical advantages: „First of all, RFID tags are significantly smaller and lighter than optical markers and they do not require visual contact. The position is always detected throughout the whole room instead of only within a small radius. For hygiene reasons there's a trend towards using one-way instruments in medical environments. RFID tags can be replaced after usage without high costs or already be integrated into the one-way instruments by the industry in advance“, says Güttler. However localization precision first of all had to be increased for practical usage, Güttler continues. With regard to the current prototype the position accuracy was in the magnitude of sub-centimeters, which means that the instruments' position can be determined with a precision of less than one centimetre. „We hope that we achieve a precision of unter five millimeters in the next development step. The project was supposed to run until december 2013 but it was extended for another six months. We hope that within this period our hardware developers can provide us with a system that operates precisely with millimetre precision. We then had a clear comparability to optical systems and were able to carry out clinical tests in a follow-up project. It is the clear objective of our working group to form a bridge from basic research to practice.“

Read more articles on RFID usage in healthcase in the November issue 2013 by "RFID im Blick".

Last modified on Wednesday, 21 October 2015 17:55
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