4. A mobile x-ray imaging system has an output intensity of 0.04 mGy at 100 cm. Conditions require that a particular examination be conducted at 75 cm SID. What will be the output intensity at this distance?

3.2 (a) Determine the absorption coefficient for Si illumination form radiation with wavelength equal to 0.5 μm. (b) Calculate the thickness of Si that will absorb 60, 70, 80 and 90% of the photon energy/cm²s

5. Assume an MRI scanner imaging 'H with the following specifications: Bo = 3.0 T. Assume that with the Z-gradient on, the magnetic field strength is B0 at location Z = Zc: a. With a bandwidth of 1500 Hz, what is the gradient strength (G2) that would allow us to image a slice with 0.75 mm thickness? b. Using the gradient calculated in (a), we need to acquire an MR slice with the same slice width and positioned at 2.5 cm above the Z. position (Z = Z. +2.5 cm). What is the required RF excitation pulse center frequency (in MHz) for the slice selection pulse?

In relation to x-ray imaging, which of the following statements is true? Choose one answer.   a. The linear attenuation coefficient of a material is directly proportional to its half value thickness.     b. For clinically useful x-rays, lead has a greater half value thickness than soft tissue.     c. The intensity of an x-ray beam decreases exponentially as it passes through tissue.     d. The intensity of an x-ray beam increases exponentially as it passes through tissue.     e. Good contrast media are generally poor absorbers of X-rays.     and Why??