New technologies are providing doctors and patients with more options for treatment and improved quality of life than ever before. Procedures once entailing long recovery times and scarring may now be done almost painlessly and without significant disfigurement. Drug therapies are being tailored to target specific aspects of a disease, and donor organs can be grown from sources from which rejection is eliminated. These approaches in medicine reflect a more focused ideology when confronted with injury and disease.

Minimally Invasive Surgery

Using high-tech devices and materials such as fiber optics, physicians can perform surgery without the trauma of invasive procedures. In minimally invasive surgery, miniaturized medical instruments enter the body via existing orifices or small incisions that leave the patient with less scarring and pain, and with faster recovery times and fewer complications than previous, more invasive methods. Major procedures such as angioplasty can be done with the body remaining “sealed.” As technology reached the micro level, many procedures became non-invasive: capsule-sized robots are now used to photograph a patient’s entire digestive tract in real time and in full color, identifying gastrointestinal conditions ranging from inflammation to cancer, and doing away with exploratory surgery.

Other procedures could not be done successfully until the advent of minimally invasive technology. The Seldinger technique, in which blood vessels are punctured with a fine, hollow needle for procedures such as angiography or chest drains, is the minimally invasive descendant of a procedure that had a high incidence of complications. Use of the Seldinger technique not only resulted in more successful surgeries, but also allowed the field of interventional radiology (image guidance) to expand and become a standard surgical practice. Total hip and knee arthroplasties also have been performed using minimally invasive procedures, proving the technology’s growing value in more complex surgeries.

PET Scanning

In a PET scan (right), lymphoma (yellow arrow) is more easily identified than in a CT scan (left). Green arrows indicate normal activity. (Boca Raton Community Hospital. Dr. Jonathan Stein, Director)

All surgical procedures, even if minimally invasive, carry risks to the patient, and medicine has long relied on diagnostic tools that also do not impact the patient. Medical imaging is now a standard in aiding doctors not only as a diagnostic tool, but also to plan surgeries; as a result, such systems must be accurate. Positron emission tomography (PET) is a nuclear medicine imaging technique that produces a three-dimensional map of functional processes in the body. Today, PET scans commonly are used in detection and diagnosis of cancer because of their accuracy.

Before scanning takes place, a patient is injected with a short-lived radioactive isotope that emits a positron — the positively-charged opposite of an electron — upon decay. This isotope is also chemically incorporated into a metabolically active molecule (glucose) that during a waiting period accumulates in the tissue of interest. When the positron is emitted, it very quickly impacts an electron, and the two particles destroy each other. This event produces two highly energetic waves of gamma radiation moving in opposite directions. These rays are detected upon reaching scintillator material in the scanning device (scintillators are substances that absorb high energy radiation and fluoresce in response). This fluorescence is detected by photomultiplier tubes or silicon avalanche photodiodes to produce a 3D image.

Unlike computed tomography (CT) and magnetic resonance imaging (MRI), PET scanners capture molecular biology in sharp detail. PET scans are used to find the disease source in ontological, neurological, and cardiological applications, and also to identify dementia-inducing brain disorders. With lymphoma, PET scanning has an accuracy of 88%, while conventional techniques stand at 64%; PET’s accuracy in diagnosing cervical/uterine cancers is 87% over the 43% from conventional methods.

Gene-based Therapy

Several medical conditions such as cancer or Huntington’s chorea arise via faults at the genetic level. Many genetic processes remain unknown, and scientists have, rather than trying to replace/repair a gene outright, gained enough insight to target the specific proteins a gene produces. Targeted therapy, in which the understanding of how genes (or defective genes) work drives drug research, promises a greater level of success than screening several thousands of drug molecules at random to find one that is effective.

The drive for these “rationally designed” drugs has shown particular advancement by focusing on previously known processes of a disease. Dasatinib, for example, was developed to attack a specific protein of a specific cancer, chronic myelogenous leukemia (CML). An adult leukemia spurred by inchoate growth of white blood cells, CML occurs when a defective exchange (called a translocation) between chromosomes 9 and 22 produces an abnormal protein, tyrosine kinase. Detection of this translocation is a highly sensitive test for CML; 95% of CML sufferers have it. Chemotherapy, interferon, and bone marrow transplants are radical and carry risk of complication. Dasatinib binds to the abnormal protein and renders it inert. Such “inhibitor” drugs trigger cancer cell death or render cancer-causing genes biochemically inactive. Protease inhibitors for HIV treatment work along similar lines — not targeting the virus, but rather the enzymes it produces for viral replication.

Gene-based medicine goes beyond treatment; it also can serve as an advanced warning. Several conditions are known to develop over time or run in families — conditions that, if identified early, can be lessened or even avoided. This preventative type of gene-based therapy has led to a sharp decrease in phenylketonuria, a metabolic disorder in which the protein phenylalanine (found in artificial sweeteners) cannot break down properly, leading to severe mental retardation.

Regenerative Medicine

No amount of detection or targeted medicine can cure those conditions so genetically complex, or that accumulate to such an extent over time, that entire body systems fail. Organ transplant remains the only option, but supply, demand, compatibility, life-long monitoring, and the fragility of the patient complicate the issue. “In the last decade, the need for organ transplantation has tripled, while the amount of transplants performed has remained flat,” noted Dr. Anthony Atala of the Wake Forest Institute for Regenerative Medicine (Winston- Salem, SC). Regenerative medicine uses the patient’s own cells to create replacement organs or tissue, eliminating rejection issues.

Dr. Atala developed a process of harvesting still-functional cells from a patient and from them, fashioning a new organ. Cells are placed in a growth medium in which they are allowed to replicate. Once enough cells are available for a construct, a 3D scaffold is made in the shape and size of the organ being replaced. Cell-seeded scaffolds are then placed in an incubator mimicking conditions of a human body. Bolstered with bioreactors, cells are allowed to grow throughout the scaffold. Once the construct is complete and the cells mature, implantation takes place. The process takes four to six weeks, and the platform is absorbed harmlessly into the host’s body.

Over the past decade, Dr. Atala has successfully fashioned and implanted fully functional bladders, vascular and corpora tissue, and cartilage. Organs such as the heart or pancreas are too complex to be grown at the moment, but by repopulating them with healthy cells, the organs can be revitalized.

“You don’t want to replace a whole heart,” said Dr. Atala. “It’s a very complex organ. Heart disease is really a weakness of the muscle. One of the ways to get around that is to repopulate it with new, younger cells grown from the patient’s heart muscle.” Similarly, pancreatic beta cells, whose atrophy causes diabetes, could be replaced, leaving the pancreas and its other systems intact.

The ultimate goal of regenerative medicine is what Dr. Atala and others describe as a “universal cell.” Though still a theoretical concept, a universal cell, either synthetic or naturally occurring, would be much like a stem cell. It could be cultured to grow into any sort of tissue or organ. However, unlike stem cells, universal cells would not be recognized as foreign bodies in a recipient. It would be off-the-shelf and readily available for tissue therapies and emergencies.

NASA Tech Briefs Magazine

This article first appeared in the February, 2007 issue of NASA Tech Briefs Magazine.

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