Researchers at ENG have added a new twist to a three-dimensional diagnostic imaging technique known as optical coherence tomography (OCT). This technology is widely used in ophthalmology and in creating cross-section images of biological tissue for noninvasive optical biopsy.

By replacing the broadband light source used in traditional OCT with pairs of entangled photons, Bahaa Saleh and Malvin Teich, ENG professors of electrical and computer engineering, Alexander Sergienko, an ENG associate professor of electrical and computer engineering, and graduate students Ayman Abouraddy, a postdoctoral researcher, and Magued Nasr (ENG’04), from the department of electrical and computer engineering, have increased the axial resolution of the resulting images by a factor of five.

The investigators produce photon pairs by passing laser light through a nonlinear optical crystal, in this case a krypton-ion laser beam directed at a crystal made of lithium iodate. The twin photons that emerge continue to be linked even as they are directed along different paths—one toward the sample under investigation, the other toward a mirror. Both ultimately reach photon detectors. The differences in the amount of time that it takes for the photons in the pair to reach the detector are used to generate a highly accurate image of the interior of the sample under investigation.

The researchers used both techniques to image a piece of fused silica sandwiched between two zinc selenide windows. The improved resolution of the new technique, dubbed QOCT (quantum optical coherence tomography), results from enhanced sensitivity of the photon pairs as a depth probe and from the elimination of dispersion effects created by the wider bandwidth needed in conventional OCT.

This research has been a centerpiece of the Boston University National Science Foundation Engineering Research Center CenSSIS (Center for Subsurface Sensing and Imaging Systems) and earned Nasr the Berman Future of Light Award at Science and Technology Day 2003. For more information about quantum imaging, see http://www.bu.edu/qil.

Schizophrenia, a chronic, severe, and disabling brain disease, affects more than two million Americans in any given year, just more than one percent of the population. While genetic vulnerability is known to be a risk factor, recent studies of twins, including studies by Cassandra Smith, an ENG professor of biomedical engineering, point to the interplay of genetic and nongenetic factors, such as environmental stresses during fetal development, as possible key forces in the development of the disease.

Over the course of many years, Smith has studied the DNA of identical (monozygotic) twins and discovered minor but significant differences in their genomes. In a recent study, she specifically looked for DNA differences relevant to schizophrenia. She examined the DNA of twelve pairs of twins and eighteen unrelated pairs of siblings. Among the twins, eight pairs were affected by schizophrenia, four concordantly (both twins had the disease), and four discordantly. (Only one twin was ill).

Smith developed genetic profiles of the subjects, using a method developed in her laboratory known as targeted genomic differential display (TGDD). It allows multiple occurrences of a variety of DNA sequences to be compared. In this case, repeated sequences of the base pairs’ CAG (cytosine, adenine, and guanine) were examined. The researchers also compared “fragile sites,” areas on the chromosomes that have been identified as especially prone to breaking under adverse conditions.

The profiles of the discordant pairs of twins revealed significantly more genomic differences than did the concordant pairs. Also, the data established a link between the chromosomal abnormalities associated with schizophrenia and fragile site locations.

Smith speculates that overall genome instability, especially expressed at fragile sites, is associated with schizophrenia. She suspects that there may be a window of susceptibility during embryonic brain development during which stresses at fragile sites can produce genetic abnormalities associated with schizophrenia. She notes that cancer is also associated with genetic instability at fragile sites and proposes that similar mechanisms may be at work.

Cassandra Smith’s study will be published in an upcoming issue of the American Journal of Medical Genetics.

Muscle is composed of cells that contract in response to stimulus. They lie within a matrix of other cells that connect them and make up the shape of the muscle mass. Understanding how the muscle cells bind, spread, and contract within this matrix has important implications for developing better treatments for diseases, such as asthma and high blood pressure, that involve malfunction of smooth muscle tissue.

While working at Johns Hopkins, Joe Tien, an ENG assistant professor of biomedical engineering, was one of a team of scientists who engineered a microdevice to precisely measure the minute forces exerted by individual muscle cells interacting with the surrounding extracellular scaffolding.

The researchers fabricated tiny beds, each made up of thousands of silicone microneedles. Fibronectin, a protein that forms part of the natural scaffolding of muscle tissue, was precisely applied to the tips of the needles, providing a surface to which the muscle cells could attach. Since each of the needles could move independently, and the force needed to move the needle was known, the scientists were able to measure the direction and magnitude of deflection for each needle. They could then use this information to calculate the cellular forces exerted as the muscle was stimulated to contract.

These studies revealed that the shape of a cell was significant—cells that were confined to a small area (grown on a bed where fibronectin was applied to a small number of needles that were surrounded by untipped needles) were shown to exert very little force. They also found a correlation between the size of the area grasped and the force exerted—the greater the area, the greater the force—although there was a specific area below which this did not hold true.

The next steps for the device include measuring the effects of various proteins thought to stimulate or reduce contraction of muscle cells and experiments with different types of cells. This research was reported in the January 28 issue of the Proceedings of the National Academy of Science.

Remanufacturing takes worn, defective, or discarded products and makes them new again—in some cases, better than new. It preserves much of the original value of the product, conserving a good deal of the material, labor, and energy invested in the original product, contrasted with recycling, which transforms the product back into raw material. And according to a new report by Manufacturing Engineering faculty members Robert T. Lund, an adjunct professor, and William Hauser, an adjunct assistant professor, remanufacturing is a huge and growing industry.

In order to be remanufactured, a product must be made of standard interchangeable parts so that it is technically possible to rebuild and restore it to commercial value. Products such as automotive parts, compressors, electrical apparatus, machinery, office furniture, truck tires, and toner cartridges make up the bulk of the industry. Remanufactured products are most often sold to commercial and industrial customers, although toner and ink-jet cartridges are making inroads into the broader consumer market. The authors surveyed hundreds of industry executives over a two-and-a-half-year period. Their 179-page report summarizes previous research on the industry and profiles some of the most successful firms.

An earlier study by Lund, published in 1996, found about 70,000 remanufacturing firms in the United States, with annual sales totaling $53 billion, directly employing 480,000 people, with perhaps twice that number indirectly employed. Because companies tend to be small, and the range of products so broad, the remanufacturing industry remains largely invisible to the general public, despite the well-recognized names, such as Caterpillar, Lucent Technologies, and Pitney-Bowes, that engage in remanufacturing.

The industry’s challenges include inexpensive new products and sharply improved new-product durability. Nevertheless, firms in the current study, “Remanufacturing Industry: Anatomy of a Giant,” report an aggregate sales increase of 20 percent between 1997 and 2000. Firms are most often privately owned, and companies with sales of $25 million or more account for 68 percent of all sales in the survey.

Overall, the authors conclude, remanufacturing sales are as large as those of consumer appliance manufacturing or the steel products industry, and remanufacturing employment is six times as large as that of the petroleum products industry. According to the report, “In addition to its direct contributions to our economy as tax-paying, income-producing firms, remanufacturers are environmentally beneficial. They conserve materials, energy, and manufacturing capacity. Further, they dispose of hazardous or noxious waste safely.” More information is available online at www.bu.edu/reman.

More than 250 million people worldwide suffer from osteoporosis, a disease that causes the bones to lose mass, leaving them weak and susceptible to fracture. Postmenopausal women are particularly at risk—nearly 35 percent of them will fracture a hip, vertebra, or wrist, injuries that can have enormous medical costs and serious impact on quality of life.

Traditionally, bone density has been measured by a process known as X-ray densiometry, where the density of the bones is assessed through X rays. Although highly accurate, the procedure is expensive and exposes the patient to ionizing radiation.

Emmanuel Bossy, a new postdoctoral research associate in the Department of Aerospace and Mechanical Engineering at the College of Engineering, has developed a new ultrasound technology to detect osteoporosis. The technology is nonionizing, portable, and inexpensive, and holds the promise not only of revealing bone density, but potentially of revealing elasticity, geometry, and internal architecture as well—all indicators of bone strength and health.

In a series of in vitro experiments, Bossy first identified how differing characteristics of bone, and the soft tissue that surrounds it, influence the speed of a sound wave moving axially (along the length of the bone). By eliminating variations in speed that result from the sound waves passing through soft tissue of varying density, he was able to develop a prototype ultrasound device able to produce accurate measurements in human subjects. A clinical study is now being conducted using this prototype, which is designed for easy use in early diagnosis of osteoporosis during a routine checkup in a doctor’s office.

Bossy began working on this technology at the Laboratoire d’Imagerie Paramétrique, Centre National de la Recherche Scientifique/Université de Paris, where he received his Ph.D. He is continuing to refine the technology as a researcher at the Center for the Study of Subsurface Sensing and Imaging Systems (CenSSIS), applying methods used in bone characterization to problems such as assessing density in corals.