When studying diffusion weighted imaging(DWI), it is important to create a phantom that has a reliably controlled diffusion coefficient. In this study, we investigated phantoms to control both the diffusion coefficient and the T2-value by changing the concentration of gelatin or sucrose and MnCl2, respectively. The results showed that the diffusion coefficient decreased linearly with increases in the gelatin or sucrose concentration, and decreasing of their relaxation times was observed. By properly adjusting the MnCl2 concentrations, we were able to equalize the T2-values between phantoms having different gelatin or sucrose concentrations. Temperature dependence of the diffusion coefficient was also revealed. This phantom can be made stable for a few months by adding a small amount of NaN3 as an antiseptic agent, has a diffusion coefficient similar to that of neural tissue or clinical tumor, and is able to control the T2-value properly. We consider this phantom suitable for studying SE-type DWI and contributes to elucidation of this technique.
The definitional equation of the distortion of echo planar imaging(EPI)was examined. We compared measured values with calculated values by using the definitional equation of the chemical shift of the EPI method that first composed the diffusion-weighted image, and examined the possibility of applying it to the distortion. The results showed that the chemical shift with the definitional equation and the measurement corresponded, and the correlation between the chemical shift and the distortion was acquired. Next, the distortion of each images that composed DWI with the increase and the sign acceptable method difference of b value. The difference in the distortion between each image has increased with the increase in b value. It was assumed that the influence of the eddy currents was due to the high motion probing gradient.
In a field of contrast-enhanced magnetic resonance imaging of the liver, attention has been focused on evaluation of liver function using gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid(EOB). In this study, we examined the possibility of obtaining liver function in only one hepatobiliary phase 60 minutes after injection. First, in regard to the difference between the signal intensity of two materials, we examined the effects of slice gap, surface coil intensity correction(SCIC), and others. Secondly, we compared the difference between liver and spleen signal intensity with biochemical laboratory tests, Child-Pugh class, liver damage class, and the two indices(HH15 and LHL15)calculated by 99mTc-DTPA-galactosyl-human serum albumin hepatic scintigraphy in patients with chronic liver diseases. Finally, we designated the “Liver EOB uptake index(L-EOB60)” from those results, compared with HH15 and LHL15. The results demonstrated that the difference between the signal intensity of two materials increased in the lack of slice gap explained by cross talk, and decreased with SCIC. The difference between liver and spleen signal intensity decreased with worsened liver and kidney function. In the case of slice gap >20% and direct bilirubin <0.5 mg/dL without SCIC, the correlation coefficient between L-EOB60 and LHL15 was 0.97. L-EOB60 was strongly proportional to LHL15. We conclude that L-EOB60 meeting the above conditions can be employed as a useful index to determine liver function.
Variation in the luminance ratio of a cathode ray tube(CRT)monitor and the ultrasonographic images at different levels of ambient light(0–150 lux)was investigated to obtain optimum ambient light in the ultrasonography suite. The maximum and minimum luminances of test patterns and ultrasonographic images were measured after three technicians independently optimized the brightness and contrast of the CRT monitor and ultrasonographic images at different levels of ambient light. Furthermore, the luminance ratio was calculated from the maximum luminance divided by the minimum luminance. When ambient light increased, it was difficult for the technicians to optimize the brightness and contrast settings of the CRT monitor to maintain a high luminance ratio at 0 lux. The luminance ratio decreased rapidly as ambient light increased up to 20 lux. However, the luminance ratio decreased gradually when ambient light was higher than 20 lux. It is necessary to take into consideration the ambient light to maintain a high luminance ratio of ultrasonographic images.
Diffusion weighted imaging(DWI)is rapidly becoming widespread in MRI, with many reports of the differential diagnosis using the Apparent Diffusion Coefficient(ADC)being seen. We examined the influence of scan parameter on ADC in PROPELLER-DWI. Neither the TR nor T1 value had a major influence on the ADC value. Number of MPG pulse, effective TE, and T2 value were the factors in which the ADC value was changed. In addition, the ADC value has been changed by the scan sequence. The factor that influenced the ADC value was able to be confirmed by this experiment. It is necessary to understand the influence that an individual factor has on ADC.
We surveyed the actual conditions of mammography with regard to image quality and radiation dose at 44 facilities in Kagoshima prefecture in 1999. In April 2004, guidelines for mammography newly included the standard of digital mammography. From September to October 2005, the survey was conducted at 48 facilities, and the results of the survey were compared with that in 1999. We visited 44 of the 48 facilities, and visually evaluated the image quality of mammograms for RMI156 and clinical mammograms. In addition, we measured average mammary gland dose at each facility. The number of the mammography device that satisfied the specified guideline criterion was larger than that in 1999. Image quality for the RMI156 mammograms improved. However, the results of the present survey revealed several problems. First, the number of facilities that had quality control instruments for mammography are few. Second, radiological technologists, medical doctors, and nurses did not share knowledge or information regarding mammography. Finally, there were differences in devices and image quality for mammography among the facilities. We achieved an understanding of the actual conditions of mammography in Kagoshima prefecture by visiting many facilities, evaluating image quality, and communicating with many staff members. Our results may be useful for the development of mammography examinations.