|
The investigation of the reported issue was completed by siemens experts.The detailed logfile investigation showed a sporadic issue with the collimator mfd.After patient registration it may happen that upon starting the self-test of the collimator, the current copper filter setting is 0.0 mm (rarely used under clinical conditions, occurs temporarily, when the collimator is changing filters).The collimator firmware stores the copper filter setting before the self-tests and restores it upon finishing the self-test.At the same time, the collimator controller stores the last given copper filter setting.The copper filter setting is validated between the collimator and the controller once a different copper filter setting is provided.Therefore, under these rare circumstances (patient registration while the collimator is performing a change of the copper filters) the copper filter setting stored by the collimator controller may be different vs.The actual setting applied by the collimator after a collimator self-check.This state remains in place until a different copper filter setting is requested, for example, for imaging mode changes (e.G.Dose level, switchover between fluoro/acquisition), or upon significant changes in the measured patient thickness.This deviation is not detected by the system and neither indicated to the user (e.G.User message) nor the current setting is not reflected in the cu-value ui (e.G.Display is showing the requested filter but not 0.0 mm).The dose monitoring functions of the system (measuring and indicating the dose levels and providing alerts ¿ e.G., ¿careguard¿/¿caremonitor¿, a cumulative/local dose value which is set to 2gy/1gy per default) that provide information on the cumulated local skin dose as well as exam dose to the operator remain unaffected by the error.Therefore, there would be an adequate indication available for the operator to detect excessive dose levels and the operator would be alerted several times before exposing the patient to dose levels potentially leading to deterministic dose effects or an essential increase in the probability of stochastic dose effects.Furthermore, another indication of a higher applied dose to the user is significantly better contrast of the image, resp.Lower noise than intended and expected.In the reported case, the additional dose administered was 52 mgy.Siemens is currently developing a corrective action to prevent the issue described.
|