Measurement of human-body-window spectra using a white power light-emitting diode and its application to high-spatial-resolution computed tomography

Human body mainly consists of muscle, bone and air, and we name penetrating photons the human-body-window (HBW) rays. The HBW spectra were measured using a white power light-emitting diode (LED) and a spectrometer. The photons from the LED penetrate the human body, and reflect, refract and scatter. Therefore, we measured only penetrating HBW spectra from the human body. In the computed tomography (CT), we used a 1.0-mm-diam graphite collimator, two 1.0-mm-diam copper pinholes, and a 1.0-mm-diam aluminum pinhole. The white beam diameter is reduced using the collimator and the first copper pinhole, and the 1.0-mm-diam beam is irradiated to the object. The penetrating HBW photons are selected out using the second copper pinhole behind the object and detected by the photodiode through the aluminum pinhole. HBW-CT is accomplished by repeated translations and rotations of the object. The peak wavelength of the HBW spectra was 610 nm. The translation and rotation steps were 0.25 mm and 1.0 degrees, respectively, and the spatial resolutions were determined as 1.0x1.0 mm(2). The scanning time and a total rotation angle for CT were 9.8 min and 180 degrees, respectively.