Three-Phase Bone Scan (Nuclear Medicine)

What it is

A standard bone scan takes one set of pictures hours after the tracer is injected, by which time the tracer has bound to bone and the image shows where bone is metabolically busy. That tells you something is going on at a spot but not what kind of something. The three-phase version adds the two earlier looks that a single delayed image throws away.

The first set of pictures is taken as the tracer is going in, and shows blood arriving — perfusion. The second is taken immediately afterward, while the tracer is still in the soft tissues around the bone — the blood pool. The third is the conventional delayed image, three to five hours later, of tracer taken up by bone itself. Reading them together is what gives the study its power: a process that lights up in all three phases behaves differently from one that lights up only on the delayed images, and that distinction is often the diagnosis.

Why it is done

• To evaluate suspected bone infection, where the pattern across the three phases helps separate infection in the bone from infection in the soft tissue over it
• To assess a painful joint replacement, where the question is whether the hardware has loosened or become infected
• To investigate unexplained bone pain, and to find fractures that do not show on plain x-rays
• To characterize an area of increased activity found on another imaging study, using the timing pattern rather than the location alone

What to expect

There is no fasting and no dietary prep. An IV is placed and you are positioned under the camera before the injection, because the first phase is recorded while the tracer goes in — so the first few minutes require lying still. The second set follows immediately. Then there is a wait of several hours while the tracer distributes and clears from soft tissue; you will usually be asked to drink fluids and to urinate frequently during it, and you may be able to leave the department and come back. The final imaging can itself take a while. Budget for most of a day. The tracer dose is small and leaves the body on its own.

Questions worth asking

• Is all three phases plus the waiting time one charge, or are the delayed images billed separately?
• If additional views or SPECT imaging are added at the radiologist's discretion, does the price change?
• Since the tracer must be ordered for a specific appointment, what is the cancellation or no-show charge?
• Does my insurer require prior authorization for nuclear medicine specifically, separate from ordinary x-ray or ultrasound?