Abstract
More than 1000 laboratories worldwide use phosphorimager systems for radioisotopic gel and blot quantification. This method is extraordinary sensitive and has a wide dynamic range, and it is therefore often preferred to conventional filmโbased analysis. We checked the accuracy of our storage phosphor screen by exposing the same ^32^Pโlabelled blot in different positions on the same screen. The first exposure took place at the top of the screen, an area used more often; the second exposure at a relatively littleโused area of the screen. As the screens are said to last indefinitely, regardless of how often they are used, we did not expect a difference in the results. In fact, we found a significant impact of the position of the gel on the results. The position that was used more often gave inaccurate results; in contrast, the unused area of the screen gave data that were confirmed by Xโray film autoradiography. We conclude that, contrary to described properties, a deterioration of the phosphor screens takes place with repeated use. To avoid obtaining invalid data, we recommend frequent checks of the screens. Copyright ยฉ 2002 John Wiley & Sons, Ltd.