From biomedical engineering and medical device development to genetic research
and biological process technology, IT researchers play a major role in the growing
field of biotechnology. Here is a look at 13 of the most innovative projects
underway.
In a cavernous building tucked below campus on the Mississippi
River flats, researchers at the University's Center for Interdisciplinary
Applications in Magnetic Resonance are working to integrate two
very different tools that allow medical experts to probe the inner
workings of the human brain.
Led by center director Bruce Hammer, an associate professor of
radiology and biomedical engineering, and Priscilla Cushman, an
associate professor of physics, the research team is developing
a device that will perform simultaneous magnetic resonance imaging
(MRI) and positron emission tomography (PET) scans.
Used separately, the two techniques have provided important insights
into brain functions. Combining them, says Hammer, will enhance
their strengths and minimize their limitations—opening the door
to further insights and discoveries.
PET scans are used to study physiological functions of the brain
and to diagnose anatomic anomalies such as strokes, brain tumors,
and aneurysms. The technique measures positrons emitted during the
decay of radioactive elements injected into the body. The positrons
combine with electrons to produce two energetic photons. These energetic
protons are converted into visible light by a ring of scintillation
crystals through which the patient's body is passed.
During a PET brain scan, for example, a patient is injected with
glucose treated with radioactive tracers. Because glucose is the
primary source of energy for the brain, regions with high levels
of activity correspond to higher levels of glucose, hence high tracer
concentrations. Therefore, regions of high gamma radiation detection
coincide with regions of high metabolic activity in the brain.
In contrast, MRI scans use radio waves and a strong magnet to produce
detailed cross-sectional images of a patient's anatomy. Unlike other
types of medical scanners, MRIs provide very good soft tissue resolution
and are used extensively to diagnose a wide variety of diseases
and injuries.
A hybrid scanner would allow medical experts to correlate the two
types of images, says Hammer. For example, a magnetic resonance
image obtained at precisely the same location and time as a PET
image could be used to determine the precise structural location
of metabolic activities.
"Simultaneous PET and MRI scans would also be more accurate
and less troublesome for doctors and patients alike,” says
Hammer. Simultaneous scans also eliminate the need to transfer patients
from one piece of equipment to another.
Moreover, Hammer's earlier research suggests that PET images could
be sharpened by acquiring them in a magnetic field. A strong magnetic
field perpendicular to the positron's path causes the positron to
spiral, thus limiting the distance it can travel and improving the
scan's resolution.
"You want to detect the energy where it was created, not where
it ends up,” says Cushman.
Higher resolution images would clearly make the technique more
useful, adds Hammer, and resolutions could be further improved by
using smaller scintillation crystals, low-noise detectors, and smaller-diameter
detector rings.
But combining the two techniques presents significant challenges.
The technology needed for magnetic resonance techniques can adversely
affect the performance of the PET detector, and vice versa.
In particular, the photomultipliers that PET scanners use to convert
photon energy into electrical signals do not work in a strong magnetic
field. Conversely, some photomultipliers with magnetic components
can distort the uniform magnetic field that is essential for clear
magnetic resonance imaging.
To overcome these obstacles, Cushman turned to technology she had
developed in 1994 for use in high-energy physics experiments.
Using that technology, she developed a PET detector based a photodiode
potted inside a proximity-focused image intensifier called a hybrid
photomultiplier tube. Unlike conventional photomultipliers, the
new detector will function in a strong magnetic field.
According to Cushman, the key is turning the hybrid tube at a 90-degree
angle with respect to the scintillating crystals to align it with
the field. But that also requires the use of fiber-optic material
to direct the light produced by the crystals around the 90-degree
bend and into the tube.
"We will lose some energy [in the transition],” says
Cushman. “The question is, how much?"
Because hybrid scanners based on this technology can be made in
a relatively compact size, they have many potential research applications,
including the study of metabolic functions in small laboratory animals,
says Cushman.
This summer, she and Hammer plan to build one segment of a MRI/PET
ring at the center and test its effectiveness by scanning a radioactive
source embedded in material that simulates human tissue and by analyzing
the resulting image. Once the initial tests are completed, they
will apply to the National Institutes of Health for further funding
to build and test a full-scale prototype.
Cushman is hopeful that the NIH will share her team's enthusiasm
for the project.
"Our scanner has the potential to go to sub-millimeter resolution,”
she says. “That represents a significant advance."
