Technetium’s primary use is in medical imaging, where its radioactive form, technetium-99m, accounts for more than 80% of nuclear imaging procedures in the United States. It is the most widely used radioactive tracer in diagnostic medicine, helping doctors visualize organs from the heart to the bones without surgery. Outside medicine, technetium has a handful of niche scientific and industrial applications, but healthcare is where this element earns its importance.
Why Technetium Works So Well for Imaging
Technetium-99m has two physical properties that make it nearly ideal for scanning the human body. First, it emits gamma rays at an energy level of 140.5 keV, which is high enough to pass through tissue and reach a camera outside the body, but low enough to keep radiation exposure relatively small. Second, it has a half-life of just over six hours. That means half of the radioactive material in your body decays within about six hours, and within a day or two, virtually all of it is gone. This short window gives doctors enough time to capture detailed images while minimizing how long you’re exposed to radiation.
Technetium-99m is used in a type of scan called SPECT (single-photon emission computed tomography). A small amount of a technetium-based tracer is injected into the bloodstream. The tracer is chemically attached to different carrier molecules depending on which organ or tissue needs to be examined. Once it reaches the target area, a specialized camera detects the gamma rays and builds a three-dimensional picture of how that tissue is functioning, not just what it looks like structurally.
Heart Imaging
One of the most common uses of technetium-99m is checking blood flow through the heart muscle, a procedure called myocardial perfusion imaging. Patients typically undergo this scan during a stress test. The tracer is injected at peak exercise (or after a medication that simulates exercise), and the camera captures how well blood reaches every part of the heart. A second set of images taken at rest allows doctors to compare the two and pinpoint areas that aren’t getting enough blood.
This comparison reveals whether coronary artery disease is present, identifies regions of the heart that have been damaged by a previous heart attack, and measures how effectively the left ventricle pumps. In a study tracking over 1,600 outpatients, each 1% drop in the heart’s pumping efficiency detected on a technetium scan predicted a 3% increase in the patient’s risk of a future cardiac event. These scans are a frontline tool for deciding whether someone needs further intervention like a catheterization or can be managed with medication alone.
Bone Scans
Technetium-99m bone scans are the standard method for surveying the entire skeleton in a single session. The tracer binds to areas of active bone metabolism, so any spot where bone is being broken down or rebuilt lights up on the image. This makes it extremely useful for detecting cancer that has spread to bone, particularly from prostate, breast, lung, and kidney tumors. It also picks up primary bone cancers and blood cancers like lymphoma when they involve the skeleton.
Beyond oncology, bone scans help orthopedic specialists solve diagnostic puzzles. Stress fractures that don’t show up on a standard X-ray, especially in small bones like those in the wrist or foot, are often visible on a technetium scan. The same applies to insufficiency fractures in people with osteoporosis, where a hip or spinal fracture may be causing pain without an obvious break on imaging. Runners and athletes benefit from this: a bone scan can distinguish between a stress fracture and a soft-tissue injury like a tendon sprain when both produce similar symptoms. It also detects conditions like shin splints, plantar fasciitis, Achilles tendinitis, and complications around joint replacements or surgical hardware.
Mapping Cancer Spread During Surgery
In early-stage breast cancer and melanoma, surgeons need to know whether cancer cells have traveled to nearby lymph nodes. Technetium-99m plays a key role in a procedure called sentinel lymph node biopsy. Before surgery, a tiny amount of radioactive tracer is injected near the tumor. It travels through the lymphatic system and collects in the first node (or nodes) that drain the tumor site. During the operation, the surgeon uses a handheld probe that detects radioactivity to locate and remove those specific nodes for testing.
This technique has a detection rate of about 96.5% when technetium is used alone, and climbs to roughly 97% when combined with a blue dye. In a recent clinical trial comparing technetium to a newer fluorescent dye, technetium successfully identified 82 of 83 lymph nodes that contained cancer, a sensitivity of nearly 99%. By focusing on just one or two sentinel nodes rather than removing an entire cluster, the procedure reduces the risk of complications like chronic arm swelling after breast surgery.
Other Organs and Conditions
The versatility of technetium-99m comes from pairing it with different carrier molecules, each designed to concentrate in a specific tissue. Here are some of the other areas where it is routinely used:
- Thyroid: A pertechnetate scan evaluates thyroid nodules and helps distinguish overactive tissue from inactive lumps.
- Kidneys: Several technetium tracers assess kidney function, blood flow, and drainage, useful for evaluating transplant kidneys or suspected blockages.
- Lungs: A perfusion scan checks for blood clots in the lungs (pulmonary embolism) by showing which areas of the lung are receiving blood flow and which are not.
- Liver, gallbladder, and spleen: Different tracers image bile flow, liver function, and the distribution of cells in the spleen and bone marrow.
- Brain: Perfusion imaging can localize the area affected by a stroke or help evaluate blood flow abnormalities.
- Gastrointestinal tract: Technetium scans detect internal bleeding by tagging red blood cells and watching where they accumulate. A separate scan identifies Meckel’s diverticulum, a common congenital pouch in the small intestine that can cause bleeding in children.
- Infections: White blood cells labeled with technetium can track down abdominal infections and help monitor inflammatory bowel disease.
How Technetium-99m Is Produced
Hospitals don’t stockpile technetium. Its six-hour half-life means it would simply decay before anyone could use it. Instead, hospitals receive a device called a generator, sometimes nicknamed a “technetium cow.” Inside the generator is molybdenum-99, a longer-lived parent isotope with a half-life of about 66 hours. As molybdenum-99 naturally decays, it produces technetium-99m. Each day, technicians flush saline solution through the generator to collect, or “milk,” the fresh technetium. A single generator can supply a hospital for roughly a week before the molybdenum inside runs low and a new one is shipped in.
Molybdenum-99 itself is produced in nuclear reactors, and the global supply depends on a small number of aging facilities. Periodic shutdowns for maintenance have caused temporary shortages, forcing hospitals to delay or reschedule scans. Efforts to diversify production and develop reactor-free methods of making molybdenum-99 are ongoing.
Non-Medical Uses
Technetium has a few applications outside the hospital, though none come close to the scale of medical imaging. At very low temperatures, technetium-99 is an excellent superconductor, making it of interest in physics research. It also has notable anti-corrosion properties: adding just five parts per million of technetium to carbon steel protects it from rusting at room temperature. In practice, however, the radioactivity and scarcity of the element make this impractical for widespread industrial use. Technetium remains, first and foremost, a medical element.