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Abstract:Tissue harmonic imaging (THI) and compound imaging have been reported clinically to improve contrast resolution, tissue differentiation and overall image quality.However, there have been limited studies to date to quantify objectively the improvements in image quality achieved with these new imaging techniques. The aim of this study was to quantify differences in image quality which exist between conventional Bmode imaging, harmonic imaging, compound imaging and harmonic compound imaging. An ATL HDI 5000 scanner with three probes (C52, L74 and L125) was tested with two different types of test object, the GammexRMI model 404 GS LE and the GammexRMI 403 GS LE. The measurement limitations associated with subjective analysis methods were not present in this study, since an automated image analysis program was used to determine the image quality parameters therefore, subtle differences between the four imaging modes could be detected. Significant improvements in lateral resolution and slice thickness as a function of depth were found with THI. Contrast resolution and anechoic target detection improved with compound imaging, while harmonic compound imaging improved lateral resolution, slice thickness as a function of depth and contrast resolution. (Email: Jacinta.browne@northglasgow.scot.nhs.uk) 2

The accuracy of a transient elastography liver-scanning ultrasound system was assessed using a novel application of PVA-cryogel as a tissue-mimicking material with acoustic and shear elasticity properties optimized to best represent those of liver tissue. Although the liver-scanning system has been shown to offer a safer alternative for diagnosing liver cirrhosis through stiffness measurement, as compared to the liver needle biopsy exam, the scanner's accuracy has not been fully established. The Young's elastic modulus values of 5-6wt% PVA-cryogel phantoms, also containing glycerol and 0.3μm Al 2 O 3 and 3μm Al 2 O 3 , were measured using a 'gold standard' mechanical testing technique and transient elastography. The mechanically measured values and acoustic velocities of the phantoms ranged between 1.6-16.1kPa and 1540-1570m/s, respectively, mimicking those observed in liver tissue. The values reported by the transient elastography system overestimated the Young's elastic modulus values representative of the progressive stages of liver fibrosis by up to 32%. These results were attributed to the relative rather than absolute nature of the measurement arising from the singlepoint acoustic velocity calibration of the system, rendering the measurements critically dependent on the speed of sound of the sample under investigation. Given the wide range of acoustic velocities which exist in the liver, spanning healthy tissue to cirrhotic pathology, coupled with the system's assumption that the liver is approximately elastic when it is rather highly viscoelastic, care should be exercised when interpreting the results from this system in patient groups.2

A force platform is a technical method of quantitatively assessing balance indirectly. The use of force platforms in physiotherapy departments has become more prominent over the last few years. However, the main drawback in the use of force platforms is the lack of comprehensive calibration procedures, which casts doubt on the results obtained with these systems. Existing calibration tests are limited to testing the spatial accuracy of the force platform. This paper describes a comprehensive quality control test procedure which was developed. It is proposed that the developed quality control test procedure could be used to test all types of force platform and it includes a description of how the tests should be carried out, the frequency with which they should be carried out and the expected performance for each of the tests as recommended for the most part by the Association Francaise de Posturologie.

This paper is a review of the balance assessment methods currently used to evaluate standing balance. Most of the presently available instrumentation appears to be more suited to research laboratories than to routine clinical situations. Functional assessments of balance appear to be the quickest test to administer and do not require expensive equipment however only gross changes in balance can be detected making them suitable as a screening tool for identifying subject's needing more thorough evaluation. Force platforms appear to be most suited balance assessment instrumentation to the clinical situation since it produces a real time display and can detect small changes in subject's ability to maintain their balance making them suitable for thorough evaluations of balance and for monitoring patient's progress.