ORINS Standard Thyroid Uptake Phantom (late 1950s)

This is a Lucite thyroid uptake phantom developed by Marshall Brucer at the Oak Ridge Institute for Nuclear Studies (ORINS) sometime around 1956. By the late 1950s a commercial version was being produced by Abbott Laboratories (they had a facility a few hundred feet away from the ORINS Medical Division). The phantom was intended facilitate the calibration of instrumentation used at hospitals for thyroid uptake studies.

By measuring the percentage of the ingested radioactive iodine that goes to the thyroid, one can determine the condition of the thyroid. In the 1950s, iodine-131 was used for this type of study.

The detector was usually a NaI scintillator positioned 10 inches away from the neck.

Brucer commented: "There are a number of necessary characteristics in the phantom. First of all it must emit the same spectrum as that emitted by the neck of most patients. Such a phantom will not be useful in any other part of the body. Second, the phantom should be adaptable to not only thyroids shaped standards but to the test-tube and the capsule standards also. Third, from each standard source the same number of counts per minute per microcurie should result no matter what the size or shape of the standard."

The phantom is not perfectly round—it has three flattened sides that help stabilize it when it is laid down. A five-inch diameter was chosen because it is more or less equivalent to the thickness of a typical neck and because the phantom would still be small enough to pick up in one hand. Plastic was used because its effective atomic number is similar to that of human tissue, this means the attenuation of gamma rays is similar for plastic and tissue, and because the phantom needed to be clear to facilitate precise positioning.

The two large interconnected holes towards the front (bottom) are used to hold the mock 25 ml thyroid. The large single hole to the upper left is used to hold a mock 2 ml test tube and the smaller hole to the upper right is used to hold a mock 0.4 ml capsule. The latter holes simulate blood vessels. Read about the ORINS mock iodine calibration kit used with the neck phantom.

Reference

Marshall Brucer. Thyroid Radioiodine Uptake Measurement: A Standard System for Universal Intercalibration. ORINS 19. June 1959.