Over the last decades, manufacturers of multi-slice CT scanners have invested tremendous efforts to maintain high image qualities while reducing patient exposure to ionizing radiation [1, 2, 3, 4]. Although various studies have proven lower patient doses on latest CT scanners, little is known about over-ranging [5, 6]. Indeed, faster CT acquisitions and larger total collimations are expected to yield greater over-ranging potentially increasing the total scan length and thereby affecting DRLs. Most manufacturers have introduced some features to limit over-ranging, but their efficiency is...

Methods and materials: CT exposure data of ~24250 patients, collected between 2013 and 2018 by 9 medical physicists in more than 150 public and private French hospitals, were retrospectively analysed. Over-ranging was calculated as the difference between total exposed scan length and total imaged scan length ( Fig. 1 ). Per each scanner, mean over-ranging ± standard deviations were calculated. Inclusion criteria were the availability of slice thickness, collimation and pitch. Over-ranging in fourteen different CT models from GE, Philips and Siemens were compared. The...

The present study showed large variability in over-ranging among manufacturers and equipment models proving that additional care is still needed to limit at best unnecessary exposure. For a same clinical indication, the difference in over-ranging exceeded 5 cm for two ~4 cm total collimation CT models from two different manufacturers. The present study may also be used to further expand local optimisation strategies and local/national DRLs defining good practices in terms of total imaged scan length accounting for over-ranging.

I. Rousselle1, L. Gonzalez1, B. Royer1, C. Mabit1, N. Rossetto1, C. Corbet1, A. Noel1,2, F. Dufay1, J. Farah3 1 Pôle de Physique Médicale, C2i santé, Cabinet de Consultants en Ingénierie de la Santé, 10 rue Paul Langevin - Parc d'Activités St Jacques II, 54320 Maxéville, France. 2 Centre de Recherche en Automatique de Nancy (CRAN - UMR 7039), Université de Lorraine - CNRS, 54500 Vandoeuvre-les-Nancy, France. 3 Hôpitaux Universitaires Paris Sud, C.H.U. de Bicêtre, 78 rue du général Leclerc, 94275 Le Kremlin Bicêtre, France. Corresponding...

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