Forensic Imaging Bolstered by New Technology, Techniques
Forensic imaging continues to emerge as a subspecialty within radiology, with researchers in the U.S. and abroad reporting new technological developments and comparison techniques. These advances come as RSNA plans another refresher course in forensic imaging for RSNA 2008.
 Researchers at the Georgia Institute of Technology developed this narrowband filter mosaic, which could empower front-line clinicians to detect and assess the severity of bruises and erythema in real time. |
Postmortem Angiography Better with Mixed Contrast Media
Swiss researchers report the mixture of a water-soluble contrast medium and polyethylene glycol offers clearly superior quality over oily contrast medium and paraffin in postmortem whole-body CT angiography.
The researchers compared two different contrast media solutions—a lipophilic mixture consisting of lipiodol and paraffin oil and a hydrophilic mixture consisting of iohexol and polyethylene glycol. Performing minimally invasive postmortem CT angiography on 10 human cadavers via access to the femoral blood vessels, the researchers used a modified heart-lung machine for the pressure-controlled separate injection of contrast media in the arterial/venous system. Imaging was performed with a 6-slice CT scanner. The study results were reported in the May 2008 issue of the American Journal of Roentgenology.
"Our study showed a significant advantage in the group injected with the hydrophilic contrast mixture in postmortem angiography," said lead author Steffen Ross, M.D., of the Center for Forensic Imaging and Virtopsy in the Institute of Forensic Medicine at the University of Bern, Switzerland.
"Contrary to the group injected with the lipophilic contrast mixture, no unwanted extravasation through the gastrointestinal tract was seen," said Dr. Ross. "The fast parenchymal diffusion of the small iohexol molecules allowed a separate imaging of the arterial and venous system and gained good parenchymal enhancement of organs. Indeed, the quality of the images and the scope of detectable lesions surpassed our greatest expectations."
The study highlights the possibilities of minimally invasive postmortem CTA in an enormously important area of clinical and forensic pathology, opening the door to completely new diagnostic opportunities, said Dr. Ross.
"Postmortem CTA has, in combination with CT-guided biopsy, the great potential to establish a whole new way of postmortem examination in a minimally invasive and examiner-independent manner," Dr. Ross said. "The close collaboration of radiologists and pathologists essentially permits a maximum of diagnostic accuracy.
"I think the future of radiology and clinical and forensic pathology will become increasingly entwined, perhaps giving rise to the future specialty of 'forensic radiology' or 'radiologic pathology,'" Dr. Ross concluded.
Multispectral Imaging Goes Beyond What Eye Can See
 Volume rendering of cranial CT after arterial injection of contrast medium in a 50-year-old female. Widespread intraventricular extravasation (arrows) of contrast medium. Bleeding source was located on the bottom of the anterior right lateral ventricle. Subsequent neuropathologic examination revealed the rupture of a 2 mm intraparenchymal aneurysm of the anterior communicating artery. |
Researchers at the Georgia Institute of Technology have developed the narrowband filter mosaic, a single-exposure imaging aid that could empower front-line clinicians to detect and assess the severity of bruises and erythema in real time, regardless of the patient's pigmentation or the available lighting.
"This mosaic represents an opportunity to create a series of hand-held, simple, point-of-care devices that can provide optical contrasting of dermatologic conditions for use in radiology," said Stephen Sprigle, Ph.D., a professor of industrial design and applied physiology and director of Georgia Tech's Center for Assistive Technology and Environmental Access (CATEA).
"The mosaic gives a near real-time multispectral image that should have applications in a lot of environments, whether it's at a crime scene or an autopsy room, or within a clinic or hospital," added Dr. Sprigle.
CATEA personnel developed the narrowband filter mosaic as part of a project to design portable erythema and bruise detection technology with a goal of enhancing early prevention and diagnosis of pressure ulcers.
"Erythema and bruising were our targets in point-of-care technology," said Dr. Sprigle. "Erythema is a marker of incipient pressure ulcer development. The localized redness indicates the skin has been under some kind of distress and has become ischemic."
The researchers initially focused on people with dark skin, on whom erythema and bruising can be difficult to detect. The important visual indicators are masked by melanin in the skin.
"You want to image the skin well, and if you use a multispectral approach you're not just recreating what the human eye sees—you're augmenting what the human eye sees through contrasting," Dr. Sprigle explained. "Enhancing that contrast hopefully will allow clinicians to detect bruises that they might have missed."
With the mosaic, clinicians could also document changes in a bruise over time in a much more repeatable way and describe a bruise much better than can be done visually.
The challenge, said the researchers, was to design a simple, fairly affordable device that would supply answers rapidly. "Clinicians aren't going to be able to take images and post-process them," Dr. Sprigle said. "They need to take images and get the answer pretty quickly."
The novel custom filter mosaic was designed and fabricated using lithography and vacuum multilayer film technologies. It incorporates four different wavelengths within the visual to near-infrared range, each having a narrow bandwidth. The design permits acquisition of a multispectral image in a single exposure. The mosaic is configured to be compatible with existing complementary metal-oxide-semiconductor (CMOS) sensors.
RSNA 2008 Course Utilizes Real-World Examples
A course in forensic imaging was offered at the RSNA annual meeting for the first time last year and will be presented once again at RSNA 2008.
"The goal of the course is to introduce the concept of using primarily CT—and, to a lesser extent, MR and sonography—in postmortem imaging," said course presenter Angela D. Levy, M.D., COL MC, U.S. Army, and an associate professor of radiology at the Uniformed Services University in Bethesda, Md.
The presenters will illustrate for the audience how effective imaging is when used in conjunction with autopsy, describing different applications and death scenarios in which it has proven to be particularly useful.
"In our experience, imaging is most useful in deaths from penetrating and blunt trauma," said Dr. Levy. "But it is also useful in fire deaths and to screen the body prior to autopsy in nontraumatic deaths.
"Advanced imaging is very useful in determining cause of death," Dr. Levy continued. "It's a field that I think has tremendous potential and room to grow within radiology as well as within forensic medicine."
