n.154 – A MODEL FOR OPTIMIZATION AND PERSONALISATION OF INJECTED ACTIVITY IN DIAGNOSTIC NUCLEAR MEDICINE



Abstract

BACKGROUND-AIM
Radiation dose for all nuclear medicine procedures should be optimized and the right test with the right dose should be given to the right patient at the right time to provide appropriate diagnosis, far outweigh the potential risks, too.
METHODS
Deviation from the administered activities according to consensus guidelines should be considered appropriate when clinically indicated and if implemented equipment and/or software allows it. In our Department, since 2012, we began a route of personalization of the injected activity. First, we evaluated the prescribed activity for each diagnostic nuclear medicine procedure, following the prescriptions reported in our SOP, and we compared these values with corresponding LDR reported in Italian law. From LDR values, referred to a standard person, we calculated activity to inject as function of patient’s body weight. Then, we decided to introduce a factor based on body surface area, calculating with Mosteller standard formula. Finally, considering theoretical estimates, clinical assessment and acquired experience, we further personalized the formula, introducing a factor of activity for unit of body surface area (MBq/m2) for each diagnostic procedure and radiopharmaceutical. We evaluated the following of ALARA principle through the estimation of effective dose values to patients. At every step, a well experienced physician confirmed the reasonable diagnostic value of images by direct comparison with previous scans, too.
RESULTS
We created and introduced in clinical routine an electronic worksheet in which operators type out age, weight, height and for each examinations and radiopharmaceuticals it returns the value in MBq of personalized, optimized activity that has to be injected to the patient.
In the table 1 below the effective dose values obtained before and after the optimization route (median ± st).
In the graph 1 below the injected activity/effective dose values as function of body surface area (year 2013-2014) for Cardiac Gated SPECT (rest and stress).
CONCLUSION
Nowadays, in clinical routine, we personalize all the administered radiopharmaceutical activities which have to be injected in patients.We demonstrated the effectiveness of applying the ALARA principle to individuals, especially to children and to adults with a BSA lower than that of the standard person, without losing our diagnostic quality.

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