A proposal for phosphor imager acceptance testing procedure and routine quality controls in nuclear pharmacy practice

The digital autoradiography system is currently used in nuclear medicine for quantitative imaging of radioactivity distribution (thin layer chromatography samples, tissue sections, and cell cultures). The aim of this study was to define a set of tests for setting up a specific acceptance testing procedure and routine quality controls for this instrument.

Over a 3-month period, we analyzed the active components of the instrument (phosphor screen and photometer) by using suitable self-manufactured equipment (phantoms, lead plate, lead cylinder, and photographic paper) required to realize, in a routine quality program, the following tests: integral uniformity (IU) and differential uniformity (DU) in a useful field of view (UFOV) and a central field of view (CFOV), resolution, geometric linearity, and sensitivity.

Screen IU was 19.7 ± 2.3% (UFOV) and 11.1 ± 3.7% (CFOV). Screen DU ranged between 1.6 ± 1.1 and 1.8 ± 0.9% for UFOV and between 1.2 ± 0.4 and 1.4 ± 0.6% for CFOV. Screen resolution measured as full-width at half-maximum was 1.94 ± 0.08 mm. Screen sensitivity was 505.1 ± 10.4 digital light units and ranged between -3.15 and +3.49% with reference to the mean of measured values. Photometer IU was 17.4 ± 0.2% (UFOV) and 13.7 ± 1.1% (CFOV). Photometer DU ranged between 1.9 ± 0.9 and 2.3 ± 1.2% for UFOV and between 1.9 ± 0.8 and 2.1 ± 1.1% for CFOV. Photometer resolution was good (full-width at half-maximum =0.5 ± 0.076 mm).

Our results suggest that the methodology we propose could be an easy, accurate, quick, and low-cost tool to guarantee the correct instrument basic function.