Description:
RT&L FOCUS AREA(S): General Warfighting Requirements (GWR)
TECHNOLOGY AREA(S): Bio Medical
OBJECTIVE: Design and build a non-contact Laser Ultrasound (ncLUS) imaging scanner in the form of a stand-alone lightweight handheld device. The acquired images are to be displayed in real- time using a handheld screen, archived and accessible for reviewing on demand in retrospective analyses.
DESCRIPTION: Ultrasound (US) imaging is a real-time medical imaging technique developed in the 1960’s that involves the transmission and reception of high frequency (2-15MHz) sound waves (i.e. acoustic waves) via a piezoelectric transducer located in the US probe that is moved while in contact with the patient skin. US is able to show location and movement of internal organs and blood flow through vessels in the human body by using the amplitudes and travel times of the received reflected sound waves that are reconstructed into an image. This original ‘conventional Ultrasound (US)’ approach is limited by the attenuation of the acoustic waves by air. To yield acceptable image results, conventional US requires a coupling medium (gel/water) added between the US probe and the patient skin.
Laser Ultrasound (LUS) employs a completely different signal acquisition technology, with advantages for the battlefield, compared to conventional US. LUS uses the light of two low powered lasers transmitted through air to measure acoustic vibrations. It supports rapid use as it only needs to be moved above the patient, with no connecting medium required, no physical contact. This is advantageous in cases where skin contact is prohibited due to burns or, e.g. blast debris wounds. In contrast, conventional US requires contact of a probe with the patient surface accompanied by a contact medium.
ncLUS has recently been demonstrated by Zhang et.al. [1] who acquired in vivo human ultrasound images in a laboratory setting using experimental table-top optics. Zhang et.al. used 1540 nm pulsed source laser to deliver the optical pulses to excite acoustic waves on the tissue surface, and a 1550 nm continuous wave (CW) laser Doppler Vibrometer to measure returning acoustic vibrations on the tissue surface, 1m distant. The optical source for the reported LUS system minimizes tissue penetration, specifically to convert optical energy to acoustic energy at the tissue surface. LUS uses very low power laser light and does not use ionizing radiation, so it is very safe, and safe for eyes.
With an appropriate optical design and interferometry, any exposed tissue surfaces can become viable acoustic sources and detectors. Employing skin surface photoacoustic sources in combination with laser interferometric detection (i.e. an optical detector) generates image features in human studies shown by Zhang et.al. to be comparable to images acquired with a conventional US commercial imaging system.
This project involves redesigning the ncLUS to have a compact, lightweight, portable format; a shirt- pocket-size handheld imaging scanner similar in size to a cellular phone, with visualization via a wired or wireless handheld screen. The back of the device would contain the scanning lasers. Sides of the device would have connected components, either hinged to flip down, or telescoping. These would assist operating the ncLUS to stand off the body surface as it is moved over the body surface. This project will necessitate innovative engineering. In this physical format, ncLUS can become a powerful asset to evaluate trauma and plan optimal treatment in cases of internal injury. Secondly, the ncLUS can provide a useful training device [2].
US, of all medical imaging modalities, has favorable use advantages which include: its reliance on non-ionizing radiation; its real-time cine imaging capability; and, its ability to be built into portable systems having simple power needs (e.g. [3]). ncLUS’s unique additional advantages are: no patient contact; potential for miniaturization; potential for fabrication using low cost solid state electronics; and, no requirement for probes and gels whose use and availability at the POI may be problematic. US trauma imaging includes several standard US examination techniques: Focused assessment with sonography for trauma (FAST) examination - to screen for blood around the heart or abdominal organs; and, extended FAST (eFAST) - to detect pneumothorax, hemothorax, pleural effusion, or a foreign object. Military use [4] of portable conventional US (i.e. probe with US transducer, processor and screen, gels) in the field currently includes identifying blood in the abdomen, finding fractures, skin infections, and collapsed lungs.
PHASE I: The main goal of Phase I is a feasibility study in the development of a handheld ncLUS scanning device. Initially, to prove feasibility, a physical, electronics, optical and circuit design of the final handheld ncLUS product should be completed as the first deliverable. The electronic and circuit designs should include commercially available electronic, computer and optical components, or components that can be fabricated easily and without extraordinary expense.
The physical design of the ncLUS must have a form factor of approximately the width and height of a cell-phone, but may be slightly thicker. It should fit in a shirt breast pocket. Weight should be minimized. The physical design should also include fold-out sides or similar simple, easy to manipulate mechanism in order to provide the key separation between the handheld ncLUS and the body of the subject being scanned. The ncLUS should be designed to operate by battery for a minimum of one hour prior to battery recharging. The scanning device should contain an Android computer capable of performing the computations that reconstruct an image in near-real-time, i.e.>5 updates per second, from the acquired laser signals. This computer should also be able to transmit the images wirelessly or by wire to an external device for display, or use the native screen. Storage of images for replay and archiving should be accomplished using the device, and perhaps an external computer. Innovation is encouraged in each design aspect to create a lighter, more rugged, longer charged device. A second deliverable is a CAD computer model of the scanner, accompanied by a physical mock-up of the scanning device. A third deliverable is a description of the image acquisition and reconstruction methodology. This is necessary because of the innovative role of lasers in signal acquisition. A detailed software schematic must be produced to indicate the real- time computational path leading from the acquired laser signals as they are converted to greyscale image, and as the image is displayed. Specific existing software, or a plan to program new software, must be identified that can accomplish each step involved in the software path. All image data must be compliant with DICOM standards.
PHASE II: The overall objective of Phase II is to produce a fully operational prototype handheld ncLUS scanner in the specified form factor that can acquire human images in tests, archive and display the images on external devices, retrieve the images from the archive and redisplay them. The first goal of Phase II is to produce prototype hardware based on the electronics and optical design of Phase I. The emphasis should be focused on hardware integration and operation during this stage. This task will produce the first deliverable, a 2x or 4x size prototype of the ncLUS that acquires laser signals that can be observed on an oscilloscope. The prototype should initially adhere to the Phase I design except for its physical size. Testing of improvements and changes is then encouraged in order to take advantage of the state-of-the-art in electronics, computers, and optics. The signals should be acquired from an inanimate phantom at this early stage.
The next aim is to expand the emphasis to the programming and testing of software for the scanner. The aim of this stage is to produce a second deliverable that is a modified form of the first deliverable, except replete with fully operational software for the acquisition of laser signals, reconstruction of the greyscale images, and transmission of the images to an external handheld computer. Innovation in the transmission, storage and display of images is encouraged. All image data must be compliant with DICOM standards. This system and software should be tested extensively with inanimate phantoms. Power deposition must be demonstrated to not exceed FDA guidelines. Modifications to the electronics, optics and/or acquisition function should be made at this point. Next, the focus should shift to the production of a fully functional prototype ncLUS scanner in the desired form factor, complete with the computer software needed to perform signal acquisition and all functions for display, archiving and retrieving the acquired images. This scanner should be demonstrated to acquire human images, under an IRB-approved research protocol. One fully functional prototype will constitute the third deliverable, accompanied by validation test reports and other relevant reports and designs. Provide an FDA regulatory plan to illustrate the pathway to clearance.
PHASE III DUAL USE APPLICATIONS: Develop training software, sample input and manuals for the system. Due to the device’s small size and likely modest price, the main target for the product is the mass commercial market, i.e. primary care physicians, clinics, and EMT use. The contractor should refine and implement their regulatory strategy for obtaining FDA approval of their technology for use as an US device based on their initial FDA feedback. This phase should culminate in submission to the FDA of the developed technology for approval. In conjunction with FDA submission, the contractor should develop scaled up manufacturing of the technology that follows FDA quality regulations. In addition, the work may result in technology transition to an Acquisition Program managed by the Service Product Developers. The contractor can also propose use to the Services. Utility would be enhanced if the device was easily able to transmit images from phone internet application(s), enabling teleradiology and potentially integrate with artificial intelligence. The ability to provide a non-contact ultrasound device to the battlefield space will enable better visualization of injuries without the need to remove clothing and protective gear before it's necessary to treat.
REFERENCES:
- X. Zhang, J.R. Fincke, C.M. Wynn, M.R. Johnson, R.W. Haupt, B.W. Anthony, Full noncontact laser ultrasound: first human data, Light: Science & Applications (2019) 8:119.
- DC Hile, AR Morgan, BT Laselle, JD Bothwell, Is Point-of-Care Ultrasound Accurate and Useful in the Hands of Military Medical Technicians? A Review of the Literature, Military Medicine, 177, 8:983, 2012
- Medgadget Eds., Butterfly Network Expands Applications for Smartphone-Connected Ultrasound: Interview, Medgadget Nov 14, 2019.
- J.D. Crisp, Portable Ultrasound Empowers Special Forces Medics, Journal of Special Operations Medicine Volume 10, Edition 1 / Winter 10, pp.59-62 (2017).
