Special issue on patient specific modelling (PSM)

This special issue of the journal includes nine papers on patient specific modelling (PSM)—five related to cardiovascular modelling, three on the simulation of musculoskeletal systems and one on brain biomechanics. Typically in PSM, anatomy and other data specific to an individual are fed into a computer programme, which calculates and delivers information relevant to the specific individual to enable provision of patient-specific diagnoses, treatment or prognosis. Examples include information on the following: blood flow and related quantities such as wall shear stress obtained using computational fluid dynamics, strain and stress in soft tissues or bone using computational solid mechanics or electrical activity in the heart using electrical models. The medium to long-term aim in this field is the provision of information that is clinically useful, to predict the risk of clinical events such as aneurysm rupture or stress fracture, to categorise patients for surgery, to aid surgical planning and in the prediction of post-surgery events. The area of PSM has its origins in two-dimensional numerical modelling studies using idealised geometries [1–4]. Advances in high-resolution three-dimensional (3D) medical imaging have allowed acquisition of geometries suitable for PSM. The first reports that can be classified as being subject specific in cardiovascular modelling were of blood flow in arteries [5–8]. For musculoskeletal modelling, automated procedures to generate 3D finite element meshes from scans provided a major boost to PSM [9, 10]. In this special issue three cardiovascular modelling papers describe applications in abdominal aortic aneurysms: Doyle et al. [11] investigated the effect of different material properties on the model outputs, Hardman et al. [12] investigated inlet flow data and Morris et al. [13] investigated the effect of different stent configurations. Different treatment options to improve hemodynamics in patients with total cavopulmonary connections are described by Mirabelle et al. [14], and Smith et al. [15] described a framework for simulation of cardiac perfusion. Pankaj [16] reviewed the challenges associated with assigning material properties and boundary conditions in the PSM of bone and bone implant systems, whereas a review on the constitutive behaviour of trabecular bone is provided by Carretta et al. [17]. Taylor et al.[18, 19] considered the PSM of the hip and knee, pre-implantation and post-implantation. A fuzzy mesh-free framework for the PSM of the brain is described by Zhang et al. [19]. The current state of PSM is reflected by the papers in this special issue in that there remains an emphasis on the development of methodology and optimisation of the processing chain, whereas a few observational studies have been published comparing data from different patient groups. Clinical trials whose aim is to establish the clinical utility of PSM have yet to be published, whereas several studies are in progress at the time of writing. General reviews of PSM are provided by several authors [20, 21].