Results Dose calculation The energy absorption and dose distribution of microbeam in a homogenous water phantom, half-air/half-water phantom and the voxel-lung models were calculated by MC simulations. The results of all simulations are shown in this chapter. Dose distribution of microbeam in a homogeneous water phantom Figure 14.A shows the dose distribution of MRT in the simple cubic water phantom (5×5×5 mm3). The width of microbeam was 50µm with a center to center space 400 µm. therefore, it creates 14 lines of microbeam(yellow lines in figure 14.A) in the water phantom. It seems that the there is no difference among micrio-lines, and dose distribution is completely uniform in whole water phantom. As can be seen in figure 14.B, a high dose gradient between peak and valley regions was achieved. It seems that …show more content…
What will be occurred if there is a soft tissue in the vicinity of air layer? To answer the question, a water-body was added to the geometry, and dose was calculated in the whole phantom. Figure 16 shows a dose profile of water-air interface with a presence of water-body. Interestingly, a new peak but smaller than main peak was appeared in the border of air and water-body. The peak drops very fast due to the water .body region. In fact, photoelectrons travel from air-layer to the water-body and they are absorbed in the new water-air interface. It leads to a new peak in the border of air and body-water. Additionally, low energy scattered photons from the air-valley region can reach the new air–water interface and deposit their energy in the air-water interface. Hence, a new peak is created in the border of air and water (figure 16). Dose distribution of this simulation has been shown in figure 17. Figure 16. Dose profile of single microbeam in water-air interface with an extra water-layer. The x axis shows the distance from the center of phantom and y axis indicates the