Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI), is a medical diagnostic technique which can image sections of the body in arbitrary directions. Contrary to X-ray imaging, computed tomography, or nuclear medicine, the MRI technique is not based on ionizing radiation. Instead, static and time varying electromagnetic fields are used to obtain a signal from the hydrogen atom nuclei (proton) of the body.

Protons are abundantly present in the body, e.g. in water and fat. The signal obtained can be mathematically reconstructed into images. The MRI scanner is mainly used to image soft tissue and the images may be adapted to represent anatomy as well as function.

MRI is a complex technique which is still rapidly developing. Research and development are therefore critically needed to fully utilize the potentials of MRI. In Malmö there are at present five modern MRI scanners (three with magnetic field strength 1.5T and two with 3T) which are used both for routine examinations and for research projects.

In the field of MRI physics we develop new methods for image acquisition and data processing. We also work on algorithms for simulations of various phenomena in physics and physiology. The research projects that we currently focus on in Malmö are briefly described below.

 

    

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Quantitative fat measurements using MRI
   

Accumulation of fat within and around our organs play an important role in both health and disease. As not only the amount, but also the type of fat and where it is stored may impact the risk of complications of e.g. obesity and diabetes, determining our weight or body mass index (BMI) is not enough. Instead, methods are needed which non-invasively can localize, quantify and characterize fat in the human body. Such techniques would avoid the use of painful biopsies or radiation exposure through computed tomography examinations while providing improved accuracy and detail in larger volumes.

We believe that MRI can provide the solution and we work on the development and improvement of methods for measuring the amount and chemical composition of fat in various parts of the human body.

 

 

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New techniques for non-invasive early diagnosis of osteoarthritis
   

We develop and implement magnetic resonance imaging (MRI) methods for evaluation and diagnosis of musculoskeletal disease. Specifically, we focus on studies of early stage osteoarthritis (OA) which is the most common chronic condition of the joints. It is characterized by breakdown of joint cartilage but the whole joint is involved in the development of the disease. For example, damage to the menisci is a potent risk factor for future knee OA.

Our general aim is to utilize the unique properties of MRI to provide access to quantitative tools enabling non-invasive studies of OA disease at an early stage. In co-operation with our clinical collaborators, Professor Martin Englund, Professor Leif Dahlberg and Associate Professor Carl-Johan Tiderius at Lund University, our methods are implemented in longitudinal studies of patient cohorts with OA or at risk of developing OA. The main platform for our projects is the national ultra-high field 7T facility in Lund.

This is a joint project with the department of Medical Radiation Physics, Lund at Lund University.

    

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Preclinical imaging in TRISTAN
   

Side effects caused by different drugs affecting the lung tissue are observed increasingly in different patient populations, however incidence and prevalence are poorly understood. Mechanisms are not fully elucidated and several hundreds of various types of drugs are able to cause the type of toxicity and injury, called Drug-induced interstitial lung disease (DIILD). The clinical phenotype, imaging and histopathology patterns are highly variable and often difficult to distinguish from other causes of ILD. 

Lund University is one of the 21 sites within the consortium named TRISTAN (Translational Imaging in Drug Safety Assessment), that perform preclinical models and apply imaging techniques such as MRI, CT and PET to assess lesions in the lung tissue caused by drug administration. The aim of the project is to find sensitive and specific imaging biomarkers in newly developed preclinical DIILD models, to understand DIILD and also enabling early detection of signs of DIILD progression.

This project is a European IMI-funded consortium with researchers and clinicians investigating novel imaging biomarkers in DIILD. The whole consortium is dealing with drug safety with different focus on lung toxicity but also liver toxicity and drug metabolism, where studies of side effects are of interest in both clinical studies as well as preclinical experiments performed by academic partners together with pharma companies.

 

    

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MRI measurements of lung function
    

According to the World health organization (WHO), chronic obstructive lung disease, COPD, is the third largest cause of death worldwide. Together with lung cancer and respiratory infections, lung diseases are responsible for more deaths than cardiovascular disease. If we can develop MRI methods to study the lung, we would be able to study healthy individuals at repeated time points, and study the long time effects of medical treatments in patients.

One promising approach is oxygen-enhanced MRI, which uses the magnetic properties of dissolved oxygen in the blood. When a subject breathes 100% oxygen, it is possible to see a direct increase in MR signal in the lung - the paramagnetic oxygen shortens the T1 relaxation time in the blood of the lung. This method has already been used to detect differences in oxygen uptake between various diseases as well as smoking and non-smoking healthy individuals. The work in Malmö is to improve the method, and obtain a 3D image of the oxygen-enhancement effect in the entire lung.

Today, T1-images are used to study the enhancement effect of oxygen in the lung. But the T1 itself is also an important parameter; it determines the contrast is in a normal MRI scan, and depends on physical factors in the tissue, such as blood content, iron content, the proportion of red blood cells, and as previously stated - oxygenation. By studying T1 in healthy subjects, we have been able to show that lung T1 changes with age and is different between women and men. Moreover, we have detected long term effects in the lungs after breast radiotherapy with T1-images. By increasing the knowledge about the physiological basis of T1, we hope to be able to use T1-images as a biomarker or as a measure of lung function.

More information can be found in the thesis of Simon Kindvall, PhD. Länk till ”https://portal.research.lu.se/portal/files/54271318/Simon_e_spik_ex.pdf”

The research center in Malmö is integrated with the radiology and clinical physiology clinics, which enables collaborations with university teachers, doctors and the Department of Medical Radiation Physics. In addition, we collaborate with the Department of Respiratory Medicine and Allergology in Lund. Our research is funded by, among others, Allmänna Sjukhusets i Malmö stiftelse för bekämpande av cancer and Stiftelsen för cancerforskning vid onkologiska kliniken vid Universitetssjukhuset MAS.

   

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Radiotherapy

The research is focused on the use of MRI for radiotherapy applications (MR in RT. Professor Lars E. Olsson is project manager for the National Radiotherapy project "Gentle radiotherapy". This is a consortium for developing and implementing MRI in radiotherapy process. All university hospitals and a large number of industrial partners are participating in the consortium supported by VINNOVA (www.gentleradiotherapy.com).

Geometric distortions in MR images are often of concern when the images should be used for radiotherapy, for which the geometric accuracy is of great importance. We have studied the impact of geometric distortions on the treatments for male pelvis using a dedicated phantom from Spectronic Medical AB (Grade, http://www.spectronic.se)). Assuming a dedicated MRI protocol for radiotherapy is used the distortions are of minor impact for treatment of the prostate.

A significant part of MRI in RT research relates to creating density maps, often called synthetic CT (sCT) from MRI, which can replace the CT in an MRI-only workflow. In collaboration with Spectronic Medical AB, we have developed and validated a software (MRIPlanner) for sCT generation for male pelvis. In a similar project, a software is under development for the skull. The method relies on convolution neural networks and machine learning. Using the MRIPlanner, we performed the first MRI-only clinical study using radiotherapy to treat prostate cancer in Sweden (2018-2018).

A critical part of MRI-only workflow for prostate treatments is the fiducial markers used for positioning during irradiation. Since these are made of high atomic number materials to be seen with X-rays, they are not necessarily easy to detect in MR images. A considerably part of the research from this group concerns the MRI-methods to detect and identify fiducial markers as well as QA methods of the process.

Another aspect of using MRI in radiotherapy is motion. The examination time can be extended and the anatomy may change in the pelvis during the examination. On the other hand, MRI can be used to monitor the motion. In a study of patients with prostate cancer, these aspects are investigated.

More information can be found in the thesis of Christian Jamtheim Gustafsson, PhD. Länk till ”https://portal.research.lu.se/portal/files/63059965/Christian_Jamtheim_…”

A growing area of interest is the application of artificial intelligence (AI) and machine learning to radiotherapy applications. We are working on automatic target segmentation on MR images and treatment plan optimization using AI.