TECHNIQUE FOR ADJUSTING X-RAY BEAM HARDENING

TECHNIQUE FOR ADJUSTING X-RAY BEAM HARDENING

FIELD OF INVENTION

The invention generally relates to a medical imaging X-ray beam and more particularly to a technique for adjusting X-ray beam hardening.

BACKGROUND OF THE INVENTION

Generally, X-ray beams used in medical imaging are polychromatic in nature. X-rays with energy ranges which are more easily attenuated are referred to as soft X-rays while those in ranges that are more penetrating are referred to as hard X-rays. Thus, X-Ray beam hardening technique involves selective removal of soft X-rays from the X-ray beam. As the soft X-Rays are removed, the beam becomes progressively harder or more penetrating. The amount of beam hardening depends on the initial X-ray spectrum as well as on the composition of the material or tissue traversed.

A conventional technique for X-Ray beam hardening involves metal based filters, for example, aluminium (Al) or copper (Cu) among others, are used as filter materials. The filters are fixed at top of an X-Ray tube to attenuate soft X-ray as shown in Figure 1.

Figure 1

The filters used in the technique are of uniform thickness. However, the filters are capable of separating soft X-rays of particular wavelength only. As a result, a patient undergoing examination with any such device gets more radiation dose than required.

Another conventional technique involves an X-Ray tube with several filters superposed over each other and having non-uniform thickness. The filters are superposed to get several different kinds of filtration thickness. For example, four kinds of filters are superposed to sixteen different kinds of filtration thickness as illustrated in Figure 2.

Figure 2

The alternating thickness depends on radiation exposure parameter and imaging characteristic of an organ. Thus, the thickness variation range of the filters is bigger. However, superposition of different filters with varying thickness results in t...