Optical Confirmation of Nasogastric Tube Placement with Early Photon Imaging
Lead Research Organisation:
Heriot-Watt University
Department Name: Sch of Engineering and Physical Science
Abstract
Placement of enteral feeding tubes (nasogastric tubes/NGTs) is a standard medical procedure, yet misplacement is a serious issue (e.g. food entering the lungs with consequent death and disability from pulmonary complications). Current practice relies heavily on ionising X-ray radiation to localise medical devices during procedures causing significant disruption given the need to protect staff as well as waiting for the availability of, or transport to, X-ray equipment. There are therefore significant clinical drivers to develop alternative placement confirmation methods. We have developed an optical technology (no X-rays) to augment and guide NGT placement using a compact bed-side system.
We have demonstrated a ground-breaking approach to track and show correct NGT stomach placement (or misplacement in the lung) using single photon imaging. Our approach exploits the fact that if a point source of light is placed inside the body, a tiny fraction of the light will emerge from the body effectively in a straight line. Crucially, these line-of-sight photons (particles of light) hold precise information about the spatial location of the point source inside the tissue. We can utilise this information as the line-of-sight photons exit the body faster than the more diffuse photons that have been scattered along a longer path to exit the body - we are able to use a technique known as time-correlated single-photon counting (TCSPC) to detect and specifically observe and use the fast photons.
In contrast to "normal" cameras, which do not record the arrival time of the photons, TCSPC-based imaging relies on using a light source that produces short pulses at precisely known times, together with a single-photon sensitive detector that records arrival times. Therefore, TCSPC imaging allows us to design an imaging system that can selectively detect and image the location of the line-of-sight photons before the diffuse scattered photons start to emerge, allowing us to precisely locate the source.
Although we have initially demonstrated the potential of this technique to locate NGTs, we are increasing the detection speed to provide real time tracking using the newest detectors - similar to those in development for self-driving cars. We have also combined our technique with new optical fibres optics placed in the NGTs, which have light sources spaced along their length allowing observation of the full NGT path during placement or reconfirmation.
We now intend to finalise the clinical prototype device and complete preclinical validation, including determining diagnostic accuracy. We will then move to evaluating feasibility and safety of the devices' ability to guide NGT placement in patients.
Our goal is to reduce significant adverse events associated with NGT placement (and reconfirmation), make placement faster, enhance clinical workflows (removing need for x-rays), improve patient outcomes through initiating feeding/medication earlier and reduce overall costs.
We have demonstrated a ground-breaking approach to track and show correct NGT stomach placement (or misplacement in the lung) using single photon imaging. Our approach exploits the fact that if a point source of light is placed inside the body, a tiny fraction of the light will emerge from the body effectively in a straight line. Crucially, these line-of-sight photons (particles of light) hold precise information about the spatial location of the point source inside the tissue. We can utilise this information as the line-of-sight photons exit the body faster than the more diffuse photons that have been scattered along a longer path to exit the body - we are able to use a technique known as time-correlated single-photon counting (TCSPC) to detect and specifically observe and use the fast photons.
In contrast to "normal" cameras, which do not record the arrival time of the photons, TCSPC-based imaging relies on using a light source that produces short pulses at precisely known times, together with a single-photon sensitive detector that records arrival times. Therefore, TCSPC imaging allows us to design an imaging system that can selectively detect and image the location of the line-of-sight photons before the diffuse scattered photons start to emerge, allowing us to precisely locate the source.
Although we have initially demonstrated the potential of this technique to locate NGTs, we are increasing the detection speed to provide real time tracking using the newest detectors - similar to those in development for self-driving cars. We have also combined our technique with new optical fibres optics placed in the NGTs, which have light sources spaced along their length allowing observation of the full NGT path during placement or reconfirmation.
We now intend to finalise the clinical prototype device and complete preclinical validation, including determining diagnostic accuracy. We will then move to evaluating feasibility and safety of the devices' ability to guide NGT placement in patients.
Our goal is to reduce significant adverse events associated with NGT placement (and reconfirmation), make placement faster, enhance clinical workflows (removing need for x-rays), improve patient outcomes through initiating feeding/medication earlier and reduce overall costs.
Technical Summary
Placement of enteral feeding tubes (nasogastric tubes/NGTs) is a standard medical procedure, yet misplacement is a serious issue (e.g. food entering the lungs, with consequent death and disability from pulmonary complications). Current practice relies heavily on ionising X-ray radiation for medical device localisation, causing significant disruption due to the dual requirements to protect staff and waiting for the availability of, or transport to, X-ray equipment. Current X-ray based techniques for NGT localisation often yield ambiguous and difficult-to-interpret results, resulting in (at best) delays to feeding whilst the procedure is repeated or (at worst) inappropriate commencement of feeding and subsequent severe harm to the patient.
We have developed a compact bedside system capable of providing a practitioner with real-time guidance/feedback/visualisation when placing NGTs. This device utilises an imaging implementation of the technique known as time-correlated single-photon counting (TCSPC). When a point source of light is placed inside the body, a tiny fraction of the light will emerge from the body with a near line-of-sight / direct path. These initial photons can be differentiated from later-arriving photons (which have been subject to scattering by tissue) by a time resolved single-photon sensitive camera positioned outside of the patient. The direct path photons hold precise information about the location of the point source inside the tissue. In combination with a custom NGT/insert that controllably emits light at distinct points along the tube, we can therefore detect the complete path of inserted medical devices. The path is visually projected back onto the patient, in real-time, during placement or reconfirmation. This device has the potential to improve clinical workflows, increase safety and shorten time to feeding (linked with improved clinical outcomes).
We now aim to clinically translate and evaluate our device in a first-in-human study.
We have developed a compact bedside system capable of providing a practitioner with real-time guidance/feedback/visualisation when placing NGTs. This device utilises an imaging implementation of the technique known as time-correlated single-photon counting (TCSPC). When a point source of light is placed inside the body, a tiny fraction of the light will emerge from the body with a near line-of-sight / direct path. These initial photons can be differentiated from later-arriving photons (which have been subject to scattering by tissue) by a time resolved single-photon sensitive camera positioned outside of the patient. The direct path photons hold precise information about the location of the point source inside the tissue. In combination with a custom NGT/insert that controllably emits light at distinct points along the tube, we can therefore detect the complete path of inserted medical devices. The path is visually projected back onto the patient, in real-time, during placement or reconfirmation. This device has the potential to improve clinical workflows, increase safety and shorten time to feeding (linked with improved clinical outcomes).
We now aim to clinically translate and evaluate our device in a first-in-human study.
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