X-ray luggage CT is widely used in airports and railway stations for the purpose of detecting contrabands and dangerous
goods that may be potential threaten to public safety, playing an important role in homeland security. An X-ray luggage
CT is usually in a helical trajectory with a high pitch for achieving a high passing speed of the luggage. The disadvantage
of high pitch is that conventional filtered back-projection (FBP) requires a very large slice thickness, leading to bad axial
resolution and helical artifacts. Especially when severe data inconsistencies are present in the z-direction, like the ends of
a scanning object, the partial volume effect leads to inaccuracy value and may cause a wrong identification. In this paper,
an iterative reconstruction method is developed to improve the image quality and accuracy for a large-spacing multi-detector
high-pitch helical luggage CT system. In this method, the slice thickness is set to be much smaller than the
pitch. Each slice involves projection data collected in a rather small angular range, being an ill-conditioned limited-angle
problem. Firstly a low-resolution reconstruction is employed to obtain images, which are used as prior images in the
following process. Then iterative reconstruction is performed to obtain high-resolution images. This method enables a
high volume coverage speed and a thin reconstruction slice for the helical luggage CT. We validate this method with data
collected in a commercial X-ray luggage CT.
The key of analyzing the light signal transmitting in fiber is the interaction and correlation between them. At present, we
must consider the medium and the light field as one united system. Its strict physical theory is the quantum
electrodynamics (QED), to process the light field and medium to second quantization. The quantum theory is considering
both the medium and the light field as quantum wave function, so we can discuss the extreme limit frequency and
distance. In the analyzing of extreme limit frequency, we can get it by considering two situations: the first is the
photoelectric effect between light signal and fiber medium, the second is the transmission effect of high frequency
incident light. In the analyzing of extreme limit of light signal distance, we will consider the interaction of the electron
and the light field. We apply the theory and formula of scattering section. We analyze the colliding mechanism of
particles in medium. We calculate the transmitting situation of photon energy according the energy and momentum
reservation laws. According to the maximum frequency shift of light which is allowed by optical receiver, we can get the
extreme limit distance of signal transmitting.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.