Attenuation is the reduction of intensity of a radiation beam as it passes through an object. Attenuation depends on the atomic density, the incident object’s atomic number of the absorber, and the energy of the incident photon.
Beam geometry describes the shape of the x-ray beam as it leaves the x-ray tube housing and strikes the detectors. As the number of detector rows increases, the beam becomes wider to cover the detector array.
Multidetector CT scanners (MDCT) utilize a cone beam during image acquisition. The cone beam is utilized in order to expose the entire row of detectors evenly to radiation.