Contrast medium INDEX

Acute reduction in renal perfusion is considered important in the pathophysiology of contrast agent-induced nephrotoxicity. Color-coded duplex sonography has been used in assessing intrarenal vascular resistance in 10 patients (mean age 51 years) after intravenous injection of 100 ml of the low-osmolar contrast medium iopamidol (iodine 300 mg/ml) (182). The resistive index was measured at 1-minute intervals over 10 minutes after injection in each patient. There was a statistically significant rise in resistive index at 2, 3, 4, and 5 minutes after injection, mean values 0.74, 0.75, 0.72, and 0.75... 

To evaluate its capability for refractive index measurement, the fiber FPI device was tested using various liquids including methanol, acetone, and 2-propanol at room temperature. The interference spectra of the device immersed in various liquids are shown in Fig. 7.12 for comparison. The signal intensity dropped when the device was immersed in liquids as a result of the reduced refractive index contrast and thus lowered Fresnel reflections from the cavity endfaces. However, the interference fringes maintained a similar visibility. The spectral distance between the two adjacent valleys also decreased, indicating the increase of refractive index of the medium inside the cavity. Using (7.4), the refractive indices of the liquids were calculated to be nmethanoi = 1 -3283, acetone = 1 -3577, and n2-propanoi = 1.3739, which was close to the commonly accepted values. 

This provides a better contrast than the phase-contrast method by utilizing a phase difference to improve contrast. However, separation and recombination of the light beam into two beams is accomplished using prisms. DIC microscopy generates interference colours, and the contrast effects indicate the refractive index difference between the particle and medium. 

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