A very-low-irradiating localization device for interventional radiology – NEWLOC

Interventional radiology (IR) procedures expose the staff (and of course also the patient) to ionizing radiations (up to 60 minutes of irradiation during complex but classical procedures). More than 500,000 IR procedures are performed each year in France. Although the progresses of fluoroscopy have reduced the dose, the level of delivered irradiation remains a problem, especially for physicians working intensively under X-ray. Continuous fluoroscopy is required to localize in real time the position of the tip of the tools with respect to patient’s anatomy.

We propose to demonstrate the feasibility of a novel (recently patented) method to localize the tip of the inserted tools. Preliminary results show that the amount of irradiation should be reduced by more than 10 times. This would be an alternative to magnetic localization of tools, which increases the complexity of the intervention and is subject to artifacts, thus limiting its wide use. We propose to place a miniaturized X-ray sensor at the tip of the tool. When localization of the sensor is required, a “rotating collimator” (a rotating disk made of radio-opaque material with one or several non-radio-opaque linear slits) is positioned just in front of the X-ray source, converting the X-ray beam geometry from cone-beam to fan-beam. The sensor receives X-rays only when one of the fan-beams, i.e. planes defined by the X-ray focus and a slit, passes through the sensor. Thus, by signal processing, the sensor position can be projected on the detector image plane and registered on the fluoroscopic image taken before the localization step. Since the surface of the slits represents less than 1% of the surface of the radio-opaque collimator, the irradiation is very significantly decreased with respect to the classically emitted dose.

We plan to build a demonstrator combining: i) a miniaturized X-ray sensor integrated at the tip of an intra-vascular guide-wire, with the corresponding chain of signal acquisition and processing, synchronized with the X-ray source; ii) a rotating collimator and a method to calibrate it and to synchronize it with the signal from the X-ray sensor; iii) a localization software to process all the incoming data, to transform them into localization of the miniaturized X-ray sensor, and to overlay this localization information in the classical X-ray image; iv) the integration of the complete system in an operational X-ray room for its characterization on a representative phantom enabling measurements of the accuracy of our approach and of the obtained dose-reduction; v) refined clinical specifications for the dissemination of the method, with a risk-analysis, so that clinical trials can easily be launched at the end of the project; vi) preparation of the industrial exploitation of the virtual fluoroscopy concept to transform our results into widely disseminated results.

All these steps raise scientific and technological challenges. Our consortium is built to master the associated risks. Localizing interventional tools is a typical issue of Computer Assisted Medical Interventions (CAMI). This expertise is brought by 3 actors grouped in a Labcom (TIMC-IMAG - a CNRS Unit, CIC-IT – an INSERM Unit dedicated to demonstration of medical benefit of CAMI tools, SurgiQual Institute – a company devoted to designing CAMI solutions in the respect of regulatory issues). Designing novel miniaturized X-ray sensors is the expertise of INL (a CNRS Unit) and of Thales (a major industrial actor in this domain). Several clinical experts of Interventional Radiology of Grenoble University Hospital’s CIC-IT, are already working with us and will help prepare clinical validation. Thales and SurgiQual Institute are in charge of industrial dissemination of the results.

Reducing by more than 10 times the delivered dose during the most demanding phases of IR procedures should have a major impact, thus facilitating wide dissemination of the results.