The volume and the distribution of premorbid white matter hyperintensities: Impact on post-stroke aphasia

White matter hyperintensities (WMH) are a radiological manifestation of progressive white matter integrity loss. The total volume and distribution of WMH within the corpus callosum have been associated with pathological cognitive ageing processes but have not been considered in relation to post-stroke aphasia outcomes. We investigated the contribution of both the total volume of WMH, and the extent of WMH lesion load in the corpus callosum to the recovery of language after first-ever stroke. Behavioural and neuroimaging data from individuals (N = 37) with a left-hemisphere stroke were included at the early subacute stage of recovery. Spoken language comprehension and production abilities were assessed using word and sentence-level tasks. Neuroimaging data was used to derive stroke lesion variables (volume and lesion load to language critical regions) and WMH variables (WMH volume and lesion load to three callosal segments). WMH volume did not predict variance in language measures, when considered together with stroke lesion and demographic variables. However, WMH lesion load in the forceps minor segment of the corpus callosum explained variance in early subacute comprehension abilities (t = -2.59, p = .01) together with corrected stroke lesion volume and socio-demographic variables. Premorbid WMH lesions in the forceps minor were negatively associated with early subacute language comprehension after aphasic stroke. This negative impact of callosal WMH on language is consistent with converging evidence from pathological ageing suggesting that callosal WMH disrupt the neural networks supporting a range of cognitive functions.

Apnoea detection: human performance and reliability of a computer algorithm

We examined the consistency of apnoea recognition between three human experts. The hypothesis was that computer detection of apnoea could emulate human expert apnoea recognition. The aim was to detect apnoeas with the highest possible accuracy from a single breathing signal, by both human experts and computer. Three human experts independently examined recordings of breathing wave-form from overnight sleep studies from 10 infants aged 3-17 weeks. All apnoeas of 5 s or more were identified and reviewed. However, there still remained 10% disagreement. A computer apnoea detector was implemented. An algorithm analysed statistical properties of the signal to find breathing pauses. Optimal performance was 1% missed apnoeas (compared with the agreed apnoeas identified by the three experts) and 29% false detections. This computer algorithm reliably identified most apnoeas but did not replace the human expert.

The sorcerer and his apprentices: contributions of Professor R.H.T. Bates to the physical sciences and engineering in medicine

The late Professor R. H.T. Bates (Richard) left an enormous legacy of published research and launched many young researchers and engineers into their careers. In doing so he established an international network of information engineering/scientists that is in itself a laudable contribution to the global multidisciplinary scientific community. In this paper are reviewed the contributions that Professor Bates and his students made over the last two decades in the physical sciences applied to medicine. Where appropriate (i.e. where it doesn't overlap with other contributions to this issue) brief descriptions are given of current research projects in the Department of Electrical and Electronic Engineering at Canterbury, (where Professor Bates carried out most of his research, and where the authors are now ensconced) which in some way relate to the work of "the sorcerer" and his former "apprentices" (as Professor Bates liked to refer to the group).

From living being to medical image--bridging the dimensionality gap

The human body is viewed, in the context of medical imaging, as a multiplicity of three-dimensional time-varying images, coinciding in time and space. Medical imaging modalities that are well established, or are undergoing clinical trials, or are at the tentative proposal stage, are tabulated. Also listed are the types of radiation and other physical processes employed to gather the image data, the physical parameters which can be imaged, and the physiological attributes represented by these parameters. Image reconstruction algorithms are reviewed and possible improvements are assessed. The processing of multidimensional information is emphasised as of primary concern for future progress in medical imaging. Such processing is seen to be developing along two converging paths: the processing of information from coincident images of different parameter distributions, and the processing of time-sequential images of a single parameter distribution. The images referred to have three spatial dimensions, implying that a challenge for future medical imaging systems is conjectured to be the efficient distillation of useful information (which must include the most effective means of image display) from multiple sets of time-varying volume data. Medical diagnosis can always profit from improved interpretation of information provided by the multifarious types of radiation and other physical processes which are employed in established and tentative medical imaging techniques. There is a premium on parameter sets that provide independent information and on processes, such as magnetic fields, ultrasound, and low frequency electric currents, which are free of the stigma associated with ionising radiations. Promising avenues of exploration are identified.

3-D Reconstruction of the Heart from Few Projections: A Practical Implementation of the McKinnon-Bates Algorithm

The implementation of a method for improving the quality (by reducing artifacts) of images reconstructed from small numbers of projections is described. The technique is based on an algorithm originally proposed by McKinnon and Bates [1] and includes enhancements suggested by Heffernan and Robb [2]. Emphasis is placed on practical aspects of algorithm implementation, including important noise-suppressing refinements not previously incorporated into the algorithm. The efficacy of the method is demonstrated using actual X-ray projection data of the intact beating heart recorded with the Mayo Clinic's dynamic spatial reconstructor. The implications of improved "stop-action" reconstruction of the heart are considered in the context of additional objectives, including automatic object recognition and definition, and improved four-dimensional reconstruction of the beating heart.