A Finnish multicentre quality assurance project in bone scintigraphy and brain SPET: a phantom study

We examined all routinely used bone scintigraphy and brain single photon emission tomographic (SPET) systems in 19 laboratories in Finland. Physical performance of bone scintigraphy systems was measured with a 57Co flood source and with a NEMA resolution phantom. Total performance of the systems was evaluated with a transmission phantom simulating bone imaging of the thorax. It was acquired both with the protocol used in a given laboratory and with a fixed protocol. The participant laboratories were asked to report all accumulations on a diagrammatic thorax drawing. Tomographic uniformity, contrast and resolution (i.e. physical performance) of the SPET systems were evaluated with a special phantom. In addition, a Hoffman brain phantom was measured with routinely used acquiring and reconstruction protocols (total performance). All measurements were performed with the same test objects supervised by the same physicist. Manufacturer, age or the collimator of the camera did not correlate with the physical performance of the imaging systems (r < 0.65). This is probably due to lack of regular quality control of the gamma cameras in some laboratories. Comparison of the physical and the total performance shows that the detector itself is not necessarily responsible for inaccurate findings from the test object. Use of dual intensity and digital images in both scintigraphy could certainly increase the sensitivity of the findings: sensitivity of single intensity images was 65% (33-89%), dual 73% (28-100%), analog 65% (28-100%) and digital 74% (50-94%). Standardization of acquisition and reconstruction protocols will improve quality of brain SPET images and comparability between laboratories. This study showed the need for objective audit tests of bone scintigraphy and brain SPET systems in Finland.