Measurement and Evaluation of the Acoustic Noise of A 3 Tesla MR Scanner

2007-01We measured the sound level and frequencies of the acoustic noise generated by a 3 Tesla (T) MR scanner, and investigated the subjective sound level for 30 healthy volunteers with either earplugs, headphones or both. The sound level of 3T was found to be higher than that of 1.5T in all sequences. The peak sound pressure level of 3T ranged from 125.7 dB for MR angiography to 130.7 dB for single shot EPI on the linear scale. The equivalent noise level was from 110.0 dB for FLAIR to 115.8 dB for T1-IR on the A-weighted scale, which exceeded 99 dB, the level regulated by the International Electrotechnical Commission (IEC). The study of the subjective sound level showed that the effect of noise reduction was not significantly different between earplugs and headphones. However, the use of both devices could reduce the subjective sound level significantly better than either one alone (P<0.01). Thus we propose wearing both devices for ear-protection during 3T examinations.departmental bulletin pape

Osseous Lesions of the Hand and Foot in Diabetes Mellitus: Correlation between Magnification Roentgenographic Findings and Clinical Findings

1986-03Twofold magnification radiograms of hands and feet in 384 diabetic cases were reviewed to determine the correlation between clinical findings and osseous lesions, especially early changes. A small, well-demarcated, round radiolucent lesion (small lytic lesion) was the most frequent finding in 87.2% of the 384 patients. In particular, a small lytic lesion of less than 1 mm in diameter was encountered in 85.9% of all cases by magnification radiography. A small lytic lesion can be thought of not only as a specific finding but also as one of the prodromic findings of diabetic osteoarthropathy. Localized osteopenia was also specific for diabetes, with a fairly high frequency (39.1%). Multivariate analysis revealed significant correlation between osseous lesions, especially small lytic lesions, and retinopathy. Significant correlation between retinopathy and osseous lesions was also identified by clinical follow-up cases. These facts suggest that microangiopathy may play an important role in the development of osseous involvements.departmental bulletin pape

The Elastic Constant of Tissue in the Body Estimated from Computerized Tomography and Ultrasonography : Theoretical Analysis

1981-11This paper describes a method for calculating the elastic constant of tissue. Length measurements obtained from Ultrasonograms (US) are different from the results obtained from Computerized Tomograms (CT) when the velocity of sound is compared to standardized water measurements. The density of tissue ρt can be approximated by the equation. ρt = 1-Nc/Nair, where Nc and Nair are the CT-values of tissue and air respectively. The elastic constant (bulk modulus) Kt, sound velocity V, and density ρt are related through the following equation, V= (Kt/ρt)^0.5. The elastic constant Kt is then calculated by, Kt = Kw (Lc/Lu)^2・(1 - Nc/Nair), where Kw is the bulk modulus of water, and Lc and Lu are the measured distances from CT and US images respectively.departmental bulletin pape

AN EVALUATION OF THE BIOLOGICAL EFFECTS OF THREE DIFFERENT MODES OF MAGNETIC FIELDS ON CULTURED MAMMALIAN CELLS

1995-12-25The biological effects of static magnetic fields, and their combined effects with ionizing radiation, were studied using a cultured mammalian cell line (FM3A). The three different modes of magnetic fields evaluated in this report were the 0.3 Tesla (T) field with a gradient of 0.3T/m, the 0.7T field with a gradient of 0.7T/m and the 6.34T field with no gradient. Exposure to the 0.3T and 0.7T fields had no effect on cell survival. Exposure to the 6.34T field decreased cell survival. Survival curves showing the combined effect of the 0.3T and 0.7T fields with radiation had a smaller mean lethal dose (D37) value. The survival curve of the 6.34T field was influenced by the interval between magnetic exposure and ionizing irradiation. When the interval was 6 or 12 h, the survival curve showing the combined effect of the 6.34T field had smaller D37 and quasithreshold dose (Dq) values, indicating the potentiation of the radiation effect. Flow cytometric analysis indicated that exposure to the 0.3T and 0.7T fields showed no change and that exposure to the 6.34T field showed an increase in the percentage of G1 phase cells. Our conclusions were as follows: 1) magnetic fields decreased the colony-forming abilities of cultured mammalian cells; 2) magnetic fields can affect the cell cycle; 3) a stronger magnetic field strength does not always have stronger biological effects and 4) the gradient of a magnetic field may be an important factor when combined with ionizing radiation. Despite the foregoing analysis, the biological effects of magnetic fields on mammalian cells remains a complex phenomena.departmental bulletin pape