Magnetic resonance imaging and personalised medicine for aortic dissection

Rachel Clough

Rachel Clough, London, UK, writes that personalised medicine applied to aortic dissection has the potential advantage of precise prediction of outcome for individual patients. 

The US Personalized Medicine Coalition uses the term “personalised” broadly to refer to the effects of new developments in medical profiling. This produces what the coalition calls a “new healthcare paradigm”, with new methods for prediction and prevention of disease as well as the development of targeted medicines. Technologies that are personalised allow better delivery of individualised management (prediction, prevention and treatment), customised to each person’s specific genetic, physiological or psychological characteristics. We have developed a range of new magnetic resonance (MR) imaging methods to allow more personalised treatment for patients with aortic dissection.

The management and long-term outcome of patients with type B aortic dissection is challenging and in some series only 50% are alive at five years. The main late complication of type B aortic dissection is progressive enlargement of the false lumen resulting in aneurysm formation, rupture and death.

Patient characteristics, aortic morphological and false lumen characteristics based on computed tomography (CT) image data have been suggested to risk stratify patients with aortic dissection. These parameters have been investigated in small studies which have demonstrated inconsistent results. Although widely used the ionising radiation dose from a CT scan is clinically significant and there is evidence of an increased risk of radiation-induced death. The UK-based Committee on Medical Aspects of Radiation in the Environment (COMARE) reported in 2007 that the incidence of radiation-induced fatality is 240 per 100,000 for a 10mSv CT scan performed every five years between the ages of 40 to 70 years.

MR imaging uses magnetic fields to produce images of tissues and organs. It is therefore radiation-free and ideally suited to aortic dissection, where patients are often young and require multiple surveillance scans. MR also has superior soft tissue contrast compared with CT and is able to provide functional in addition to anatomical information.

The new MR imaging techniques that we have developed allow us to understand aortic dissection by the measurement of patient-specific haemodynamics and biomechanics. These techniques include sequences that are able to measure the elasticity and displacement of tissues, blood flow characteristics, wall shear stress, relative pressure and more accurate assessment of false lumen components. These techniques have been shown in small cohorts to have the potential to identify patients with aortic dissection at high risk of aneurysm formation. We now plan to prospectively evaluate the predictive value of these MR imaging parameters in a multicentre study. The integration of imaging data with detailed patient and environmental factors on a large scale would identify important factors relevant to the biological mechanisms of this disease.

Personalised medicine applied to aortic dissection has the potential advantages of prompt early intervention, surveillance tailored to each patient and reassurance if nothing of clinical significance is found. The key to the future application is to ensure that the information provided is useful and medically appropriate to allow precise prediction of outcome for individual patients.

Rachel Clough is an NIHR Academic Clinical Lecturer in the Division of Imaging Sciences and the Department of Vascular Surgery at King’s College London and Guy’s and St Thomas’ NHS Foundation Trust