S. Donatiello

A novel method for CT dosimetry with a suspended phantom setup

PURPOSE This work presents a method for estimating CT dosimetric indices with a prototype designed for suspending the phantom/ion chamber system fixed at the CT isocenter. The purpose of this study was to validate the proposed methodology, which can be used to provide a direct assessment of dosimetric indices in helical scans. METHODS The method is based on a reference setup in which the measuring system for CT dosimetry is in a stationary configuration, i.e. not bound to the CT table, and on a mathematical formalism developed for the proposed reference system. The reliability of the method was demonstrated through a set of experimental measurements. Firstly, dosimetric indices were measured with the new method and compared with the indices obtained with the procedure currently used for CT dosimetry (measuring system bound to the CT table). Secondly, dosimetric indices measured with the new method were compared with those displayed on the CT console. RESULTS There is good agreement between the dosimetric indices obtained with the standard setup and those obtained with the suspended phantom setup, within the expected range of errors. The difference between dosimetric indices estimated with the proposed method and those displayed on the CT console is below 2%. CONCLUSIONS The method enables CT dosimetry to be performed with the dose detector in a stationary longitudinal position thanks to the newly introduced suspended phantom setup. Using this approach, CT dose can be assessed for high pitch helical scans, acquisitions without complete tube rotation and for cases where dynamic collimation is used.

Computational study of mechanical support to the failing total cavopulmonary connection

The performance of an axial flow blood pump in an idealized total cavopulmonary connection (TCPC) model was intravascularly evaluated. This blood pump was inserted within a modified Fontan surgery using a reinforced Gore-Tex conduit, to be connected to the caval veins with the pulmonary arteries. Two different computational models were examined (i) the new geometric model without a pump and (ii) with the pump. Computational fluid dynamics analyses of these models were performed to assess the hydraulic performance under varying pump’s operating conditions. Numerical simulations indicate that the pump generates a pressure distribution which could prove to be beneficial for the univentricular patient with failing Fontan circulation, allowing to provide a possible intervention, at least as bridge to heart transplantation or as end-stage pump implant.