Every day, ionizing radiation is used in hospitals and clinics to perform diagnostic imaging procedures in forms of X-Ray, MRI, CT and PET. Procedures using radiation are performed for accurate diagnosis of disease and injuries. They provide important information about patients’ health and ensure doctors that patients are receiving appropriate care.
However, each of the diagnostic imaging techniques used in modern medicine present some negative aspects.
For example, it is known that high doses of radiation used in some diagnostic imaging procedures are linked to an increased risk of cancer. Many diagnostic exposures are similar to that received from natural background radiation. In the United States, such ambient exposure is about 3.0 mSv (300 mrem) every year1. However, radiation doses estimated for some common diagnostic X-ray and nuclear medicine studies are much greater than ambient exposure. Radiation doses vary for each person because of factors such as differences in x-ray machines and their settings, the amount of radioactive material used in a nuclear medicine procedure, and the patient’s metabolism2.
Other imaging technologies, such as MRI’s, exhibit their own negative aspects. In this case, it is the application of an exceedingly high magnetic field.
Furthermore, none of the existing imaging technologies can be considered truly man-portable.
Consequently, there is a growing need to develop new and improved technologies, which will overcome these short fallings. That need has inspired the research outlined in this paper. The goal is to achieve effective, efficient, portable and safe detection of tissue anomalies, including those caused by diseases such as cancer.
In order to develop this new imaging technology, specific areas investigated by this research were the electromagnetic properties of biomaterials at radio frequency (RF) frequencies, variations of such properties caused by disease, methods of non-contact, non-invasive coupling of RF energy to biomaterials, attenuation scattering and reflective effects of biomaterials.
Prior research indicates that each biomaterial has its own unique electromagnetic properties. These properties are based mainly on the water content of the biomaterial. For example, Figure 13 indicates that permittivity, which is a significant electrical property of materials, varies with biomaterial.
This means that different biomaterials absorb electromagnetic energy differentially. Similarly, biomaterials exhibit thermal properties that allow them to emit electromagnetic energy differently. This use of different parts of the electromagnetic spectrum is considered to be a multispectral application.
The net result is that the temperature of biomaterials can change depending on differential absorption and emission rates of energy. Figure 24 shows how the temperature of water increases depending on its ability to absorb and re-emit electromagnetic energy.
By capitalizing on the water-based electromagnetic properties of biomaterials, a totally novel medical technology can be developed.
It is known that the frequency of the reorientations of the water dipole occurs millions of a time each second. As a result, the electric field produced by microwave ovens is just about right to reinforce the tendency of the dipole to reorient itself, thereby maximizing the friction generated. Because food is comprised mostly of water, microwave ovens heat food equally well on the inside because of the penetration of electromagnetic energy. This depth of penetration not only depends on the power level, but its frequency of operation as well. Fortunately, human patients are also comprised of mostly water-containing biomaterials.
So, for the purposes of the research, biospecimens were obtained and irradiated at specific power densities and exposure time. The frequency utilized for irradiation was 2450 MHz (FCC approved), the operating frequency of commercial microwave ovens. This equates to a wavelength of approximately 122,448 microns (one micron equals one millionth of a meter). A contrast discriminator was inserted into the biospecimens and then irradiated, also at the same power densities and exposure times.
The biospecimen were then removed from microwave exposure and imaged with an infrared imaging system at 7-14 microns. This equates to a frequency range of 4.3 to 12.5 Petahertz. A Petahertz is 1015 Hertz or a thousand times more than the Terahertz frequency range.
The radiation of the biospecimen at microwave frequencies raised the temperature of the biospecimen because the material absorbs the energy. This is a simple expectation, evident in everyday use of such appliances in our own homes. This absorption of microwave energy is a function of the electromagnetic properties of the specimen. As stated above, one of the most influential such property is permeability or dielectric constant. Different biomaterials have different permittivity, which would result in differential absorption of electromagnetic energy
It would also be expected that examining these irradiated biospecimens at infrared frequencies should result in thermal images. The reradiation of this absorbed energy would depend on the biomaterials, which have different thermal emission properties.
The result is that different biomaterials say fat and muscle, may be discriminated because they absorb microwave energy and reradiate infrared energy differentially. The ability to differentiate between biomaterials and non-biomaterials was proven by further rounds of experimentation.
The depth of penetration (DOP) of electromagnetic energy also depends on a material’s permittivity as shown in Figure 33.
Overall, the experiment proves that this novel imaging technique can be employed successfully. The images obtained were capable discriminating between the different tissues and structures, thereby permitting detailed images to be generated.
Figure 4 is a sample image of in-vitro biological material with non-biological phantom inserted produced during the research. The biological material had approximate dimensions of 10cm by 5cm and approximately 2.5cm thick. The phantom was inserted approximately 1.25cm deep into the biological material. The technology was able to detect the phantom with a mean resolution of 7.5 mm with a standard deviation of 2.5 mm.
As this was a proof of concept experiment, only Commercial-Off-The-Shelf (COTS) equipment was utilized.
Based on the results above, the next step would be to develop a portable and comparatively low cost medical imaging device. When successful, such an imaging device will, for the first time, be placed in the hands of first responders and professional practitioners.
The resulting imager will be approximately a small laptop-sized device. It will have roughly the same physical footprint as a laptop but at least twice the thickness in order to accommodate imaging components. The corresponding weight goal will therefore be approximately 5 lbs. The display is anticipated to be larger than iPad but with better image resolution than the proof of concept experiment. Figure 5 represents the rendering of the product display area.
Use of COTS components will insure high quality and performance, yet low cost. The imager will also consume low power, be physically robust and simple to operate.
The goal is to develop a single, unified medical imaging platform which can obtain detailed, full body images on site, then transmit them quickly, accurately and at low cost to hospitals or other destinations without the disadvantages of more expensive medical imaging equipment, thereby, providing remote patient management. Figure 6 represents simple system diagram.
For example, physicians in rural communities would have access to patient imagery that is currently only accessible to select medical institutions, such as hospitals, which could be hours away even by medical helicopter.
Realtime imaging data could then be transmitted from a remote site directly to attending physicians at the medical facility. These transmissions would be accomplished through the use of existing wireless modalities to include satellite, cellular and WiFi. New wireless protocols, such as 5G and LiFi, would enhance such transmissions by higher data rates, better coverage footprint and more robust encryption.
Such imaging data would then be available to existing or future E-Health systems and hospital data networks. With this field-portable imaging technology, the patient’s condition could be diagnosed even before they are admitted to the medical facility for treatment.
Furthermore, telemedicine and telemonitoring treatment could begin prior to the patient arriving thereby, saving precious time.
Because of its uniqueness, patents for this technology were published by the USPTO in 2014 and 2015.
Deployment of this novel medical imaging system, which makes use of advanced information and communication technology, can only help to elevate dependable and accessible medicine to the next level.
Additionally, this technology will be positioned to seriously compete with products in both existing and future markets, thereby changing the face of medical imaging and diagnostics worldwide.
Further development of the technology will create a bench top model that will be used to conduct clinical trials for the basis of obtaining FDA approval.
Arthur Ritter, PhD, Distinguished Service Professor of Biomedical Engineering at Stevens Institute of Technology.
1United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effects of ionizing radiation, Vol. 1: Sources. New York, NY: United Nations Publishing; 2000.
2Wall BF, Hart D. Revised radiation doses for typical x-ray examinations. The British Journal of Radiology 70: 437-439; 1997. (5,000 patient dose measurements from 375 hospitals)
3Omer T Inan, Assistant Professor Bioengineering, Georgia Tech, Lecture Topic “Interactions of Electromagnetic Waves with Biological Tissue” Spring, 2005.
4Chaplin, Martin. “Water and microwaves.” London South Bank University- become what you want to be. 7 Aug. 2006.