Modern Medical Imaging Thanks To Tungsten Collimators

While the function of a CT scanner remains a mystery to most people, no one would doubt its usefulness. The machine can focus X-rays in a way that creates multiple slices of a person, effectively allowing doctors and technicians to view a high-contrast 3D image of their body.

CT scanners were introduced in the 1970s and have played an important diagnostic tool ever since. CT scans are used to monitor the growth of tumors, to identify bone trauma and bleeding in the head, and to determine the presence of blood clots, fractures and other injuries throughout the body.

The trick to getting these high-resolution images from x-rays requires that only the rays traveling parallel to a specified direction are allowed through an object. The short wavelengths emitted by x-rays are too short to be focused by a lens, so something else has to be used instead—a collimator. By definition, a collimator is simply a device that narrows the flow of tungsten alloy particles or beams, and the first collimators were invented in the field of optics to help focus light for experiments. In the medical and industrial fields, tungsten collimators are most often used.

Collimators channel incoming radiation through tiny holes bored through its surface. Rays that travel parallel to the holes will pass through them— but the majority of them will be absorbed by hitting the plate surface or the side of one of the holes. Only the particles that make it through the collimator are recorded. By selecting that particles are let through, a clear image is formed. Without the collimator, the x-rays would scatter as they passed through the object being scanned and create a blurred picture.

Their ability to direct and block radiation is so important a collimator is rated by how many half-layer values it contains, that is, how many times it can reduce undesirable radiation by half. The way a collimator is shaped allows the radiographer to direct the radiation to the film and away from the rest of the patient’s body. This ability has been harnessed to use collimators in linear accelerators for radiotherapy treatments. The collimator shapes the beam of radiation emerging from the machine and limits its maximum size. This is important because prolonged or high-intensity exposure to radiation can cause cancer.

High-quality tungsten collimators have helped to create an exceptional imaging tool that has advanced the treatment and diagnosis of patients for forty years. There is no doubt that the next forty years will bring even more breakthroughs.

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