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The work embodied in this thesis describes software techniques developed to analyse digital inline holograms of suspended particle fields, particularly in aquatic environ- ments. The primary motivation behind this work has been development of tech- niques to extract useable information from individual holograms within holovideos, producing focused silhouettes of recorded plankton and other particulates with min- imal user intervention. Two automated focusing algorithms are developed and presented in this work, both of which obtain comparable results for holograms of sparse plankton populations. The first approach is based on rectangular regions of interest (ROIs), which are aligned to (x, y) dimensions, and localise particles within the two-dimensional recon- structed planes obtained from holovideo frames. Due to poor immunity to particle merging when applied to denser particle fields, a second approach was developed using arbitrary polygons with which to localise particle positions in reconstructed planes. This new approach offers a greater immunity to the merging of particles lying in close proximity in the (x, y) dimensions of the hologram, and allows better particle localisation for high density particle holograms. Both ROI and polygon based particle localisation are explored to identify strengths and weaknesses, and complete automated scanning procedures developed in both cases. Examples are provided of typical output from automated scanning algorithms when applied to a number of sample holograms, and areas of weakness highlighted for future work.

Size and species grading of fish (eg on board a fishing vessel) might in future be done entirely automatically using image analysis and pattern recognition techniques. Three methods of discriminating between pictures of seven different species of fish have been compared: using invariant moments, optimisation of the mismatch, and shape descriptors. A novel method of obtaining the moments of a polygon is described. It was found that the shape descriptors gave the best results with a sorting reliability of 90&'37. Different methods of producing symmetry lines from the shape of fish have been studied in order to describe fish bending and deformations. The simple thinning algorithm was found to work best to provide a reference axis. This axis was then used as a basis for constructing a deformation independent position reference system. Using this reference system position specific colour measurements of fish could be taken. For this to be done the video digitising system was firstly calibrated in the CIELUV colour space using the Macbeth colour chart. Colour and shape measurements were then made on 18 species of demersal and 5 species of pelagic fish. The simple shape measurements of length/width and front area/back area ratios were used to do some introductory separation of the fish. Then the variables produced by the shape descriptors and colour measurements were analysed by discriminant analysis. It was found that all of the demersal fish were sorted correctly (sorting reliability of 100&'37) and all of the pelagic fish were sorted correctly except one (sorting reliability of 98&'37). A prototype machine is now being constructed based on the methods described in this work.

The objective of this work is to investigate the prospects for parallel computing in image processing applications in medicine. The tasks involved in filtered back projection reconstruction and retinal image registration are implemented on a hardware system based on the Inmos Transputer, using the OCCAM language. A number of task decomposition methods are used and their advantages and disadvantages discussed. An example which uses a pipeline illustrates the sensitivity of such an approach to uneven computational load over the network of processors. Farm networks and methods which use simple block division of data are investigated. The design of a system of interconnected processes for efficient, deadlock-free, communication within a grid network is proposed, designed and implemented. The difference in observed performance due both to task decomposition and to network communication are discussed. An image registration technique which uses the edges of image features to reduce the amount of data involved is proposed and implemented using the parallel network. The results of tests on the performance of the registration technique are presented. Registration using the edge-based technique is successful for a significant proportion of image pairs but, because of the high likelihood of registration being required for poor quality images, improvements are worthwhile. Where the registration technique failed, the human observer had equal difficulty in manually registering the same pair of images. A number of suggestions are made for further improvements of the technique. A strategy is proposed which uses task overlapping to improve the efficiency of a multi-stage parallel system of processes. The work highlights the most important factors in the application of parallel computing in image processing using a MIMD network and suggests a number of areas where further work is needed.

Over the last decade there has been a steady increase in the size of primary data sets collected from medical imaging devices, and a correspondingly increased requirement for the computational power needed for associated image processing techniques. Although conventional processors have shown considerable advances throughout this period, they have failed to keep pace with the demands placed upon them by clinicians keen to utilise techniques such as pseudo three dimensional volume image presentation and high speed dynamic display of multiple frames of data. One solution that has the capability to meet these needs is to use multiple processors, co-operating to solve specified tasks using parallel processing. This thesis, which reports work undertaken during the period 1988-1991, shows how a network accessible parallel computing resource can provide an effective solution to these classes of problems. Starting from the premise that any generally accessible array of processors has to be connected to the inter-computer communication network, an Ethernet node was designed and constructed using the Inmos transputer. With this it was possible to demonstrate the benefits of parallel processing. Particular emphasis had to be given to those elements of the software which must make a guaranteed real-time response to external stimuli and it is shown that by isolating high priority processes, relatively simple OCCAM code can satisfy this need. Parallel processing principles have been utilised by the communications software that implemented the upper layers of the OSI seven layer network reference model using the Internet suite of protocols. By developing an abstract high level language, software was developed which allowed users to specify the inter-processor connection topology of a point to point connected multi-transputer array, built in association with this work. After constructing a flexible, memory efficient, graphics library, a technique to allow the high speed zooming of byte sized pixel data using a lookup table technique was developed. By using a multi-transputer design this allowed a 128x128 pixel image to be displayed at 256x256 pixel resolution at up to 25 frames per second, a requirement imposed by a contemporary cardiac imaging project.

One of the principal advantages of satellite data is the ability to provide terrain information over large areas, but past analyses of Landsat MSS data have tended to concentrate on developing techniques for small study areas. A method is developed for producing such large area land cover mapping from Landsat MSS data of Scotland. A stratified, interactive approach to image analysis produced the best results, incorporating a hybrid classification method involving a thorough selection process for training data pixels. Classification is implemented by either a minimum distance or a maximum likelihood technique which is further improved by post-classification editing and smoothing procedures. Results from a training and testing area produced a final classification statistically assessed as 87.3% correct. The method has subsequently been used to produce 3 maps of primary land cover types for Highland, Grampian and Tayside regions (total area 41,330 km2).

Free radicals are defined as molecules with one or more unpaired electrons in their outer orbits. They have been implicated in a large number of disease states and consequently there is increasing interest in detecting them <I>in vivo</I>. Having an un-cancelled electron spin, free radicals are amenable to magnetic resonance experiments. For reasons of sensitivity commercially available electron paramagnetic resonance (EPR) spectrometers operate in the X-band (9 GHz). Such frequencies are unsuitable for large biological samples because of excessive electromagnetic losses. This thesis describes the development of a radio frequency continuous wave (RFCW) EPR spectrometer operating around 280 MHz suitable for <I>in vivo</I> studies. The instrument is based around an existing low field NMR imager. The spectrometer includes both automatic frequency control and automatic coupling systems to combat the problems of animal motion. The instrument has been able to detect free radicals in living animals. PEDRI is a technique that can provide high resolution images showing free radical distribution in living systems. The method is based on conventional pulsed NMR imaging combined with dynamic nuclear polarisation The disadvantage of PEDRI is that it is difficult to obtain spectral information such as EPR line-width and g-factor. These parameters are easy to obtain by CW-EPR, and can give useful information. A further development was the combining of the RF CW-EPR instrument with a PEDRI imager to produce a multimodality instrument capable of sequential PEDRI and CW-EPR on the same sample. Switch-over between the two modes of operation takes less than 5 seconds. This instrument combines the advantages of the two types of free radical detection in a single instrument providing an extremely useful and flexible tool.

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