• Journal of radiological science and technology
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• v.29 no.2
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• pp.63-69
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• 2006

In diagnostic ultrasound, the quality of image affect to diagnose. To maintain suboptimal imaging uniformly, Quality Assurance of Ultrasound equipment should take periodically. This is article about examination the quality of image in diagnostic ultrasound to understand conditions of probes in hospitals. There is comparative study of convex and linear probes on ultrasound using tissue-mimicking phantom included simulated cysts, echogenic structures. The ultrasonic attenuation coefficient versus frequency of 0.5 dB is representative of normal liver and 0.7 dB is representative of fatty liver condition in ultrasound phantom. There are results of convex probe, 0.5 dB, vertical group, cystic masses, high contrast masses are mostly shown but 0.7 dB, mid level in vertical group, cystic masses and high contrast masses are nearly visible. In linear probe, 0.5 dB, mid level in vertical group, two or four of them are shown in cystic masses and high contrast masses but there are not visible in 11 of cases. 0.7 dB, there are mostly appear under 6 in vertical group, two or four of them show in cystic masses and high contrast masses and there are not shown in 40 of cases, besides. Linear probes in fatty liver condition of ultrasound instrument are not good in the quality of image practically. So there needs to be replace and fix of probes. Actually management of ultrasound probes is inadequate in hospitals. So if there are program of evaluation to check probes periodically in hospitals from establishment of the ultrasound equipment, there will get better image and have a suitable condition of instruments further more.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.60-66
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• 2006

Three differing sandstones, two synthetic and one field sample, have been tested ultrasonically under a range of confining pressures and pore pressures representative of in-situ reservoir pressures. These sandstones include: a synthetic sandstone with calcite intergranular cement produced using the CSIRO Calcite In-situ Precipitation Process (CIPS); a synthetic sandstone with silica intergranular cement; and a core sample from the Otway Basin Waarre Formation, Boggy Creek 1 well, from the target lithology for a trial $CO_2$ pilot project. Initial testing was carried on the cores at "room-dried" conditions, with confining pressures up to 65 MPa in steps of 5 MPa. All cores were then flooded with $CO_2$, initially in the gas phase at 6 MPa, $22^{\circ}C$, then with liquid-phase $CO_2$ at a temperature of $22^{\circ}C$ and pressures from 7 MPa to 17 MPa in steps of 5 MPa. Confining pressures varied from 10 MPa to 65 MPa. Ultrasonic waveforms for both P- and S-waves were recorded at each effective pressure increment. Velocity versus effective pressure responses were calculated from the experimental data for both P- and S-waves. Attenuations $(1/Q_p)$ were calculated from the waveform data using spectral ratio methods. Theoretical calculations of velocity as a function of effective pressure for each sandstone were made using the $CO_2$ pressure-density and $CO_2$ bulk modulus-pressure phase diagrams and Gassmann effective medium theory. Flooding the cores with gaseous phase $CO_2$ produced negligible change in velocity-effective stress relationships compared to the dry state (air saturated). Flooding with liquid-phase $CO_2$ at various pore pressures lowered velocities by approximately 8% on average compared to the air-saturated state. Attenuations increased with liquid-phase $CO_2$ flooding compared to the air-saturated case. Experimental data agreed with the Gassmann calculations at high effective pressures. The "critical" effective pressure, at which agreement with theory occurred, varied with sandstone type. Discrepancies are thought to be due to differing micro-crack populations in the microstructure of each sandstone type. The agreement with theory at high effective pressures is significant and gives some confidence in predicting seismic behaviour under field conditions when $CO_2$ is injected.