Hybrid x-space: a new approach for MPI reconstruction.

Magnetic particle imaging (MPI) is a new medical imaging technique capable of recovering the distribution of superparamagnetic particles from their measured induced signals. In literature there are two main MPI reconstruction techniques: measurement-based (MB) and x-space (XS). The MB method is expensive because it requires a long calibration procedure as well as a reconstruction phase that can be numerically costly. On the other side, the XS method is simpler than MB but the exact knowledge of the field free point (FFP) motion is essential for its implementation. Our simulation work focuses on the implementation of a new approach for MPI reconstruction: it is called hybrid x-space (HXS), representing a combination of the previous methods. Specifically, our approach is based on XS reconstruction because it requires the knowledge of the FFP position and velocity at each time instant. The difference with respect to the original XS formulation is how the FFP velocity is computed: we estimate it from the experimental measurements of the calibration scans, typical of the MB approach. Moreover, a compressive sensing technique is applied in order to reduce the calibration time, setting a fewer number of sampling positions. Simulations highlight that HXS and XS methods give similar results. Furthermore, an appropriate use of compressive sensing is crucial for obtaining a good balance between time reduction and reconstructed image quality. Our proposal is suitable for open geometry configurations of human size devices, where incidental factors could make the currents, the fields and the FFP trajectory irregular.

A preliminary health technology assessment of a guidance system for interventional radiology.

Disruptive innovation in biomedical devices have to be carefully assessed in order to be included in the clinical practice, especially when these new systems interact with the human body. In this scenario the guidance devices for interventional radiology represent an area of great interest. In this paper a CT-navigation system, SIRIO, used for percutaneous interventions such as biopsy, thermal ablation, percutaneous interventional, is tested and assessed. The technical features of the system in terms of efficacy and safety and the comparison with the traditional CT-guided biopsy are analyzed. According to the clinical evidences, biopsies carried out with SIRIO show an important reduction of number of CT scans, procedure's time and radiation dose absorbed by the patients. The analysis of the technology costs, the social impact related to the benefits to clinicians and patients are also reported. Although SIRIO does not have an appropriate reimbursement procedure, short- and long-term benefits introduced by this device are discussed.