Outline of the module
In clinical and research settings alike, it is important to continuously ensure the proper functioning of all medical equipment. For MRI scanners, this means that the performance of the imaging hardware must regularly be evaluated against the manufacturer’s specifications, or other benchmarks that might be set internally by the user or as part of a multi-site research protocol.
After successful installation and “Tune-Up” of an MRI system, typically by the manufacturer, good practice therefore requires the regular execution of quality assurance routines. This serves to identify any malfunctioning or imperfections that might go unnoticed during the routine use but have a degrading effect on image quality or stability.
This module comprises a five day course on topics related to the topics of Quality Assurance and artifacts that are commonly encountered on MRI systems. In the first of the module, students will in detail be taken through the “Tune-Up” procedure. They will be familiarized with the adjustments needed on the different hardware components and the associated artifacts that will results from improper adjustments. Then various aspects related to ongoing quality assurance will be discussed, including the widely used FBIRN quality assurance protocols, stability testing and coil testing. The last few lectures are dedicated to a more general discussion on MR artifacts. Using actual examples, students will learn how to distinguish between artifacts caused by the scanner itself, poor scan protocol choices and the subject/patient, and they will learn how to develop elimination strategies for systematic testing and determining the cause of an observed artifact.
Learning objectives
At the end of this module, students will have expert knowledge of:
Content
MRI scanners are highly complex imaging systems in which many sophisticated hardware components have to work together to provide reliable diagnostic images. The introductory lecture sets the conceptual framework for this module by highlighting the motivations for Quality Assurance form the technical, ethical and regulatory standpoint. Oftentimes, problems with the scanner may not be immediately obvious during the routine imaging procedures and can go unnoticed. For instance, some problems may arise slowly with progressive but slow degradation of image quality over time, or other problems may arise suddenly but be too subtle in effect to be noticed by the operator. To ensure the proper operation of the scanner it as therefore vital to regularly and systematically check performance. The first part of the module will introduce the role of the different system hardware components and discuss the problems and artifacts that a malfunctioning of each of them can cause. Following a recap on the hardware infrastructure of an MRI scanner, four lectures will concentrate on the adjustment procedures needed to for the different hardware components. The topics will follow the chronological order of a typical Tune-UP procedure of an MRI system, during which hardware components are systematically adjusted one by one using appropriate tests. The tests, and possible artifacts for each system component go hand in and will and can therefore be described in an illustrative and intuitive manner. The first tune-up tests are related to the RF characteristics in which phase and amplitude settings are made. Then follows the adjustment of the gradient regulators, a procedure in which the gradient power amplifiers are matched to the gradient set so that the desired gradient wave form is achieved. This is followed by adjustments of the patient table, the stimulation monitor, and further calibration steps of the gradient controller: cross-term calibrations, eddy current pre-emphasis, measuring gradient delays and gradient sensitivity. Finally the RF receive path by adjusted by setting receiver gains and image intensity scaling.
Having discussed the role of the different system component in details, the second part of the module will describe actual Quality Assurance procedures that should be applied as part of the regular upkeep of the MR system. This includes testing of the RF transmit chain (spikes, instabilities and interference) and other tests related to system stability, and verifications tests of the gradient adjustments. Several standard procedures for routine QA have been described as part of good-practice recommendations, the most prominent one being the “FBIRN protocol”. The FBIRN protocol has been adopted by many research sites which makes it attractive for a cross-sites quality assurance. It comprises a small but effective battery of simple MRI scans and analyses which will be described in detail. Another aspect covered in this part of the module is the testing for MR compatibility of additional devices, i.e. checking for RF interference of electrical devices.
Finally, the module will provide an overview of the typically encountered artifacts. This will begin with a brief revision of imaging artifacts caused by the subject, such as susceptibility and motions artifacts and how they express themselves in the deferent types of MR sequences (e.g. signal loss, ghosting, distortion/shearing, blurring, flow artifacts, artifacts near metal implants). Other artifacts may be caused by additional equipment used in the scanner room (e.g. RF spikes or interference, noise). Some artifacts will have the same or a similar appearance as artifacts that arise due to system imperfections (e.g. ghosting, blurring). In the final two lectures, students will learn to develop strategies that allow them to systematically and efficiently identify the source of artifacts.
Overview of tasks and lectures
There will be 10 lectures à 2 hours distributed over 5 days.
Position within the programme
This is a unique module in the Master programme in which students learn about the various aspects related to MRI Quality Assurance.
Teaching format
Structure
The module is a one week-long residential module consisting of 10 lectures à 2 hours. Each day, the students will in addition solve mathematical and physical problems as well as implement computer algorithms relevant to the lecture guided by tutors. Furthermore, the residential part is combined with a preparatory reading phase and post-module marked assignments.
Grading
Passing the module requires an 85% attendance to the lectures and practical sessions, and a satisfactory completion of the practical sessions and the module assignments. The module assignments will be summarized by the students in a written form which will be evaluated by the module coordinator(s).