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

The development and acoustical characterisation of a range of novel agar-based tissue mimicking material (TMMs) for use in clinically relevant, quality assurance (QA) and anthropomorphic breast phantoms are presented. The novel agar-based TMMs described in this study are based on a comprehensive, systematic variation of the ingredients in the International Electrotechnical Commission (IEC) TMM. A novel, solid fat-mimicking material was also developed and acoustically characterised. Acoustical characterisation was carried out using an in-house scanning acoustic macroscope at low (7.5 MHz) and high frequencies (20 MHz), using the pulse-echo insertion technique. The speeds of sound range from 1490 to 1570 m. s -1 , attenuation coefficients range from 0.1 to 0.9 dB. cm -1 . MHz -1 and relative backscatter ranges from 0 to -20 dB. It was determined that tissues can be mimicked in terms of independently controllable speeds of sound and attenuation coefficients. These properties make these novel TMMs suitable for use in clinically relevant QA and anthropomorphic phantoms, and would potentially be useful for other high frequency applications such as intra-vascular and small animal imaging.

A device for the training and quantitative assessment of the competency of trainee radiologists in the technically challenging area of breast sonography was developed and evaluated. Currently, suitable commercially available devices are lacking, and there is a growing realization that the reliance on direct exposure to patients for learning may not represent best practice from either the trainees' or patients' perspective. Three devices (PI, PII and PIII) were designed to produce very realistic sonographic images of breast morphology with a range of embedded pathologies. The pilot evaluation used a case study research design to evaluate the role of the anthropomorphic breast sonography training device in training and assessment in a clinical environment. Through the case study, it was possible to evaluate the process and relationships when using this type of training intervention for a small group of radiology resident trainees. The investigation involved a baseline assessment of trainees' (n = 4) ability to detect and characterize all lesions in PI, followed by a 4-wk training period on PII and a post-training assessment using PIII. The evaluation revealed an improvement of 30% ± 8% in the trainee's performance from pre- to post-training. It was expected that the performance of the trainees would improve as the training phantom described in this study aligns with the learning theory of constructivism and fits the ideal specifications of a medical training device in terms of its realism and facilitation of self-directed learning and deliberate practice of the trainees. The device provides a useful platform upon which training and assessment can be facilitated.

No abstract

No abstract