Description:
RT&L FOCUS AREA(S): General Warfighting Requirements (GWR)
TECHNOLOGY AREA(S): Bio Medical
OBJECTIVE: Design and build a Terahertz (THz) medical imager in the form of a small, flexible, layered rectangular blanket, with internal functional components, that can be wrapped around the torso of a wounded patient and provide images of internal anatomy.
DESCRIPTION: THz radiation has a potentially game-changing role in military medical imaging because emerging technology offers the possibility to create portable, lightweight flexible THz imagers.
THz radiation has frequencies in the range 0.3-30 THz (1 THz = 1012 Hz), with wavelengths in the range 1 mm (below microwave) to 0.1 mm (above infrared). THz waves can penetrate clothing, among other solid objects, and are now used in some airports to scan passengers and detect dangerous items. THz radiation is an advantageous electromagnetic frequency band for medical imaging due to its low probability of causing tissue damage, since low energy THz photons are non- ionizing and are strongly absorbed by water. THz radiation can produce extremely high resolution images, and is able to image subtle tissue differences due to its high sensitivity to water content.
Previously, technical issues prevented construction of practical THz medical imagers. Recently, though, several critical technology advances in THz transmitters and detectors have appeared in the literature. These advances include flexible terahertz detectors using nanotube [1] and graphene [2] and nanowire technologies [3], and a flexible terahertz transmitter [4] using nanoscale technology. In combination, these technologies make it possible to design a flexible, lightweight, portable THz medical imager.
One can envision that such an imager can be easily carried and used in many situations to provide imaging capability [5,6]. The THz imager may provide medical images that can reveal acute traumatic injury, e.g. organ damage, internal bleeding, imbedded objects. THz imaging methodology challenges still exist. Scientists have devised a number of methods to extract biomedical information using different forms of THz imaging, as reviewed in [6]. THz phase contrast imaging seems the most successful [6] for biomedical imaging since it offers information about interior density, while absorption techniques are limited to surface imaging due to the strong water absorption of THz waves.
This project involves designing a THz imager in the form of a lightweight flexible blanket-like cover composed of a ‘sandwich’ of fabric or flexible plastic, and transmitter and detector components.
Imaginative design is encouraged, to minimize weight, increase signal-to-noise ratio (SNR), and guarantee robustness in demanding conditions. The imager is to be sized 60 cm long x 100 cm wide to wrap and provide medical images from the torso, showing internal organs. Smaller prototypes can be used in testing. Image reconstruction and display should occur on a handheld computer or IVAS (Integrated Visual Augmentation System) goggles. The THz imager has value in primary care, trauma care, and image-guided interventions. This project involves much innovation and state-of- the-art science, but the THz imager product has the potential to open up a new field and business in medical imaging. Military applications of the imager for trauma care also exist, presenting special challenges particularly in the rapid assessment of internal injuries and hemorrhage, and medical monitoring.
PHASE I: The main goal of Phase I is a feasibility study in the development of a flexible THz imaging device. To prove feasibility, a physical, electronics, and circuit design of the flexible THz imager product should be completed as the first deliverable. The electronic and circuit designs should include the latest in scientific components for THz transmitter and detector. It must be shown in the feasibility study that the THz imager can be fabricated. Battery power should accommodate two hours of use prior to recharging and comply with Army field battery usage. An added benefit would come from the computer simulation of the first deliverable showing expected operation. Subcontractor(s) should be identified and give written proof of abilities and cooperation if component construction is out-sourced. The second deliverable is the physical design of the imager. The physical design of the THz imager must accommodate the scientific and technical elements identified in the first deliverable. Component costs may limit the size of the demonstration product. The THz imager must be a lightweight flexible blanket-like cover composed of, for example, a ‘sandwich’ of transmitter and detector components sealed within a rugged flexible plastic or synthetic fabric cover. It must have a disposable sterilized cover or be able to be easily cleaned and sterilized. A good example is a flexible MRI receiver coil. Imaginative design and fabrication ideas are encouraged. The imager must be able to operate under normal environmental conditions but it would be an added plus if the product could be designed to operate under extreme temperature conditions experienced by the military (see [7]). The third deliverable is the technical design of the data acquisition – that is, the data acquisition methodology, image reconstruction, filtering options, display, image transmission and archiving using DICOM format. The imaging methodology must be robust and efficient, e.g. THz phase contract imaging that can acquire and display internal anatomy, i.e. organs, tissue and vessels. The imaging methodology must be designed for power deposition within FDA guidelines. Subsequent signal processing steps must be identified or designed. Image reconstruction, filtering, and display should occur on an Android handheld computer or IVAS goggles. The handheld computer must be capable of performing the image reconstruction computations at a rate of approximately 1 image per second or faster if possible, from the acquired data. This computer should also be able to transmit the images by wire or wirelessly to an external device.
PHASE II: The overall objective of Phase II is to produce a fully operational prototype of the flexible THz imager, scaled in size, that can acquire in vivo human images in tests, archive and display the images on external devices, retrieve the images from the archive and redisplay them.. Experimental proof of power deposition will be required to show compliance with FDA guidelines. The first goal of Phase II is to produce scaled prototype imager hardware based on the 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 prototype of the THz imager that acquires signals from an inanimate phantom that can be observed on an oscilloscope. Testing of improvements and changes is then encouraged in order to take advantage of the state-of-the-art in electronics, computers and other components of the prototype. Next the focus should be expanded to the programming and testing of software for the imager operation, data acquisition and image reconstruction. Produce a second deliverable that is a modified form of the first deliverable, except replete with fully operational software for transmission, detection, and reconstruction of 2D projection greyscale images, and, if possible, 3D tomographic image data (i.e. signals containing depth information). Demonstrate transmission of the images to an external handheld computer and IVAS. The third and final deliverable is the (perhaps modified) prototype THz imager, with handheld computer and all software needed for operation, used to acquire in vivo images from a human limb and torso. Images should be acquired under an IRB-approved research protocol. The fully functional prototype should be accompanied by validation test reports and other relevant reports and designs. Document and deliver a proposed regulatory strategy. Initiate pre-submission discussions with the FDA regarding approval for use. Deliver an FDA proposed regulatory strategy, and a manufacturability plan.
PHASE III DUAL USE APPLICATIONS: Develop software, sample input and manuals for the imager so that it can be disseminated to medical professionals and training provided for its use. Due to the imager’s flexibility, portability and (likely) ease of use, private sector commercial potential can be initially directed at facilities and medical professionals lacking available standard Radiology modalities. The contractor should refine and implement their regulatory strategy for obtaining FDA approval of their technology for use as medical imaging 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.
REFERENCES:
- D. Suzuki, S. Oda, Y. Kawano, A flexible and wearable terahertz scanner, Nature Photonics, 10, 809-813 (2016).
- X. Yang, A. Vorobiev, A. Generalov, M. A. Andersson, J. Stake, A flexible graphene terahertz detector, Appl. Phys. Lett. 111, 021102 (2017);
- K. Peng, D. Jevtics, F. Zhang, S. Sterzl, D.A. Damry, M.U. Rothmann, B. Guilhabert, M.J. Strain, H.H. Tan, L.M. Herz, L. Fu, M.D. Dawson, A. Hurtado, C. Jagadis, M.B. Johnston, Three-dimensional cross-nanowire networks recover full terahertz state, Science 368, 510-513 (2020).
- M. Samizadeh Nikoo, A. Jafari, N. Perera, M. Zhu, G.Santoruvo, E. Matioli, Nanoplasma- enabled picosecond switches for ultrafast electronics, Nature, 579, 7800, 534-539, Mar 25 2020.
- M. Jacoby, Medical Imaging Turns to Oft-Neglected Part of Light Spectrum, Chemical & Engineering News 93(44), 10-14 (2015).
- M. Wan, J. Healy, J.T. Sheridan, Terahertz phase imaging and biomedical applications. Optics and Laser Technology 122, 1-12 (2020).
- Department of Defense Test Method Standard: Environmental Engineering Considerations and Laboratory Tests (15-APR-2015) MIL-STD-810G.
