Joachim Schmidt

Fundamentals and applications of magnetic particle imaging

Magnetic particle imaging (MPI) is a new medical imaging technique which performs a direct measurement of magnetic nanoparticles, also known as superparamagnetic iron oxide. MPI can acquire quantitative images of the local distribution of the magnetic material with high spatial and temporal resolution. Its sensitivity is well above that of other methods used for the detection and quantification of magnetic materials, for example, magnetic resonance imaging. On the basis of an intravenous injection of magnetic particles, MPI has the potential to play an important role in medical application areas such as cardiovascular, oncology, and also in exploratory fields such as cell labeling and tracking. Here, we present an introduction to the basic function principle of MPI, together with an estimation of the spatial resolution and the detection limit. Furthermore, the above-mentioned medical applications are discussed with respect to an applicability of MPI.

Perspectives on clinical magnetic particle imaging

Abstract After realizing the worlds’ first preclinical magnetic particle imaging (MPI) demonstrator, Philips is now realizing the worlds’ first whole-body clinical prototype to prove the feasibility of MPI for clinical imaging. After a brief introduction of the basic MPI imaging process, this contribution presents an overview on the determining factors for key properties, i.e., spatial resolution, acquisition speed, sensitivity, and quantitativeness, and how these properties are influenced by scaling up from preclinical to clinical instrumentation. Furthermore, it is discussed how this scale up affects the physiological compatibility of the method as well as hardware parameters such as power requirements for drive field generation, selection and focus field generation, and the design of the receive chain of the MPI device.

Human PNS and SAR study in the frequency range from 24 to 162 kHz

In order to identify suitable operating conditions for future clinical Magnetic Particle Imaging, peripheral nerve stimulation (PNS) and specific absorption rate (SAR) experiments have been performed by exposing volunteers to sinusoidally time-varying magnetic fields along and transverse to the body axis at frequencies from 24 kHz to 162 kHz. The findings show that future clinical MPI can advantageously be performed at elevated drive-field frequencies, with PNS restriction actually relaxed at higher frequencies, and with still acceptable SAR exposure.

MPI Safety in the View of MRI Safety Standards

In assessing the safety aspect of future clinical magnetic particle imaging (MPI), this novel imaging technique can refer to expertise that is cumulated in the IEC standard for magnetic resonance imaging (MRI) safety. Both imaging techniques employ strong dynamic magnetic fields and therefore have to take caution to refrain from physiological effects such as peripheral nerve stimulation (PNS) or excessive tissue heating. This paper starts with an outline of the differences between MPI and MRI. Then, the basics of PNS and tissue heating are reviewed and applied to the specific MPI case. Finally, sequences for MPI are presented that will allow rapid MPI imaging at 150 kHz while being safe for the patient.

Business process integration for distributed applications in radiology

Distributed object technologies offer access to data and services virtually everywhere in a distributed application system and introduce a high degree of freedom in application design. In order to retain flexibility even during business process re-engineering, the explicit modelling of business process aspects separately from the application system components is desired. The most prominent technology to serve this purpose is workflow management, which is a groupware technology and mainly focuses on the collaboration of people. Recently developer of distributed object platforms start to provide services that initially aimed at managing distributed transactions but also allow for the modelling and enactment of communication sequences between distributed objects. We have applied the workflow management approach practically within a heterogeneous laboratory environment integrating typical radiology application systems. Here, we compare our experiences with what can be expected from such a distributed object platform taking Microsofts BizTalk as example.

Medical Picture Base Systems

Various diagnostic techniques in medicine are promarily based on pictorial information. In a hospital up to a million pictures are generated every year and, after evaluation, filed in archives. Present film archives are expensive due to their physical size, and fast and reliable retrieval is impossible. Minification systems are lacking in image quality and ease of use. Novel technologies for information storage (digital optical disc), peripheral devices for picture input and output, and fast digital picture processing lead to decentralized computerized picture information systems, which are the logical complement to hospital data base systems. They will potentially integrate the different types of modern equipment for digital picture generation or processing.

Continuous Focus Field Variation for Extending the Imaging Range in 3D MPI

The imaging volume that is rapidly encoded by drive fields in 3D magnetic particle imaging is limited by power dissipation and nerve stimulation thresholds. Additional coils have been implemented to generate so-called focus fields that operate at lower frequencies and extend the accessible imaging range. This contribution presents the possibility of sweeping the rapidly encoded imaging volume along an arbitrary 3D path using continuous focus field variations. This technique can be useful for following a tracer bolus, for tracking devices, or for dynamically moving the image focus to different regions of interest.

Fast continuous motion of the field of view in magnetic particle imaging

When shifting the FOV during imaging, artifacts arise when the shift per volume encoding time is larger than the resolution. Up to shift velocities of about 1 m/s, these can be removed by compensating the system function for the rapid translation. Fast continuous FOV shifts may be used to rapidly steer a single imaging volume to a region of interest or to achieve large spatial coverage by repeatedly sweeping the FOV through a volume of interest.

Workflow Management Systems—A powerful means to integrate radiologic processes and application systems

This presentation describes a research project investigating the suitability of model-based Workflow Management Systems (WfMS) to support radiological process. The following aspects are covered: process modeling, process enactment, and architecture of workflow-enabled application systems.

Workflow management systems in radiology

In a situation of shrinking health care budgets, increasing cost pressure and growing demands to increase the efficiency and the quality of medical services, health care enterprises are forced to optimize or complete re-design their processes. Although information technology is agreed to potentially contribute to cost reduction and efficiency improvement, the real success factors are the re-definition and automation of processes: Business Process Re-engineering and Workflow Management. In this paper we discuss architectures for the use of workflow management systems in radiology. We propose to move forward from information systems in radiology (RIS, PACS) to Radiology Management Systems, in which workflow functionality (process definitions and process automation) is implemented through autonomous workflow management systems (WfMS). In a workflow oriented architecture, an autonomous workflow enactment service communicates with workflow client applications via standardized interfaces. In this paper, we discuss the need for and the benefits of such an approach. The separation of workflow management system and application systems is emphasized, and the consequences that arise for the architecture of workflow oriented information systems. This includes an appropriate workflow terminology, and the definition of standard interfaces for workflow aware application systems. Workflow studies in various institutions have shown that most of the processes in radiology are well structured and suited for a workflow management approach. Numerous commercially available Workflow Management Systems (WfMS) were investigated, and some of them, which are process- oriented and application independent, appear suitable for use in radiology.