Ways To Test Medical Procedures

The Wall Street Journal is profiling researchers at Rensselaer Polytechnic Institute and the FDA who are building virtual computer patients to study things like how far X-ray radiation penetrates obese patients, where to place implants in children, and how best to spot vascular occlusions.  By studying the human body and encoding the many variables into a computer simulation, studies that would otherwise be dangerous to perform on live subjects can be done on the computer.CT scan.

Virtual patients could allow medical-device companies to test new products earlier, helping the devices get to market more quickly and cheaply, according to the Food and Drug Administration.

Virtual technology also someday could provide opportunities for doctors and medical students to train for certain surgical procedures by seeing and feeling organs virtually while using real tools. Doctors could be able to calculate the probability of a pregnant woman having a high-risk delivery, based on synthesized, three-dimensional images of the pelvic region and fetus, researchers say.

X. George Xu leads a team of nuclear engineers at Rensselaer Polytechnic Institute in Troy, N.Y., studying how radiation interacts with the human body. Computerized tomography, or CT, scans are frequently used in medicine to image tissues and bones in the body. But repeated exposure to radiation from the scans is believed to raise the risk for cell damage that may cause cancer and other health problems. Such risks also can exist for patients receiving radiation to treat tumors.

The researchers recently created an obese virtual patient to demonstrate what happens to radiation in this body type. Because fat can disperse the waves, overweight people usually need a higher dose of radiation in medical procedures. The aim is to administer sufficient radiation to achieve an image scan of adequate quality, but not too much to cause harm to the patient. Currently, some doctors may use existing computer software to estimate how much additional radiation is required based on factors such as weight, height and age of the patient.

Dr. Xu’s team showed that the virtual patient, using more sophisticated modeling such as how fat is distributed in the body, can provide more accurate calculations of how much additional radiation an overweight person requires. The work was presented early this year at a conference of the American Nuclear Society and has been submitted for publication at a peer-reviewed journal, according to Dr. Xu.

In related work, supported by a $1.2 million government grant, researchers developed computer software that provides readings about how much radiation each organ of the body receives after radiation exposure from a medical procedure, says Aiping Ding, a Rensselaer Polytechnic research associate who is spearheading the project.

The researchers recently tested the new software, called VirtualDose, in a simulation of an abdominal CT scan of a woman in her sixth month of pregnancy. They found that although the fetus did absorb radiation, the dose was 40% less than that calculated by a more rudimentary software tool that is currently in use.

The team hopes that calculations from virtual patients will help guide doctors in targeting tumors or making clinical decisions, like figuring out if the benefits to the mother in getting a CT scan outweigh the risks to the fetus.

Dr. Xu began decades ago creating models of human patients to understand how radiation affects the body. His first-generation designs were models that could be touched and felt. They were built of substances meant to mimic biological materials and had radiation sensors embedded throughout the torso.

Karl, a faceless, putty-colored model Dr. Xu created 20 years ago, still sits on a desk in his lab. It contrasts sharply with the strikingly vivid and anatomically correct virtual patients on the computer screen nearby.

Additional work is being done at the Center for Devices and Radiological Health, part of the FDA. Researchers there have created a “virtual family” of adults and children in order to study how best to implant medical devices in children, such as heart defibrillators. Defibrillators have been mainly studied for adult use, although children’s heart anatomy is different from that of adults.

The FDA also is exploring improved diagnostic techniques using virtual patients. In a virtual catheterization lab, scientists are inserting virtual blockages in blood flow into the heart. They then run a series of scans aimed at determining which images best detect the locations and size of the blockages. The research mimics a clinical trial, but can be performed more quickly and without risk to real patients, says Kyle Myers, director of the Division of Imaging and Applied Mathematics at the FDA division. She says researchers hope in the future to use the techniques to investigate potential treatments.


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