Phase-contrast X-ray Imaging (PCI)
X-ray technology has been facing issues of imaging soft tissue since its invention for 100 years. Dr./Prof. Atsushi Momose (Tohoku University) has successfully solved this issue that enable to image beast cancer tissues or cartilaginous tissue clearly. Its resolution is very high quality, and its been expected to use not only medical fields but also other non-destructive inspection fields.
The X-ray double bare refractive indexes generally display as .
Here, indicates X-ray amplitude decrement (absorption), and indicates an X-ray phase shift.
In the hard X-ray area, an X-ray phase shift becomes bigger than decrement of the amplitude (it becomes around 1,000 times for the weak absorption object in particular). Therefor, it can get images with the high sensitivity using a phase shift for the object consisting of light elements.
The phase technique of CT software, TomoShop® can apply to experiment environment using the following Talbot interference.
In the case of using Talbot interferometer for a diffraction grating, it can gain phase images with the X-ray source for laboratories. Therefor, it can be said that it is high utility method.
Midorino Research Co., ltd (The developer of TomoShop®) has been conducting algorithm study based on the theory of Prof. Atsushi Momose that achieving optimal quality of imaging results of X-ray CT with reducing the number of times of x-ray photography to several times from dozens of times without reducing the quality.
As an advantage, the quantity of X-ray radiation exposure decreases, reducing the degree of expectation of having highly sophisticated level of precision of the machine operation by hardware and reducing the entire cost of developing the CT system.
- The photography number of times is used to four times from dozens of times. Therefore quantity of X-ray radiation exposure largely decreases.
- Distance to move a diffraction grating becomes big around several times. Therefore operation becomes simple.
- Operating image reconstruction in phase CT is that calculations are done with high precise level, so that it out put the results with less artifacts.
Like Fig.1 above, fix the distance from a detector to a diffraction grating at Talbot distance to form a self-image. Divides the N period of the diffraction grating equally and decides movement distance. Then, Move a diffraction grating at movement distance laterally and photograph it afterwards.
Fig. 2 shows a phase sample. Fig. 3 shows one peace of image of the simulation.
It processes N images which photographed and can restore the phase difference image of the sample. Fig. 4 and Fig. 5 is the phase difference images restored by using the captured image of the four steps (N = 4).
 Momose A, Takeda T, Itai Y and Hirano K, Phase−contrast X−ray computed tomography for observing biological soft tissues, Nature Medicine 2, 473—475, 1996.
 Yashiro W, Harasse S, Takeuchi A, Suzuki A, Momose A, Hard-x-ray phase-imaging microscopy using the self-imaging phenomenon of a transmission grating, Physical Review A, vol. 82, Issue 4, 2010.