A slat collimator in single photon emission computed tomography consists of a set of parallel slats. As the collimator spins, the detector measures a one-dimensional projection data set. A complete data set can be obtained by rotating the detector/collimator assembly around the object (patient) while the collimator spins continuously. The measured projection data are assumed to be weighted plan...

UNLABELLED Our objective was to optimize the quality of (123)I-metaiodobenzylguanidine (MIBG) scans by using a medium-energy collimator to reduce high-energy-photon septal penetration. METHODS In addition to the 159-keV γ-ray, (123)I has a small abundance of energies above 400 keV that can compromise the image quality of MIBG studies because of septal penetration. Using a low-energy ultrahigh...

Photonic crystal PC composites are sequenced series of PCs that feature the same periods but different filling fractions. By properly tuning the filling fractions of the individual PCs and merging the working band of each PC into a continuous frequency range, wide-band self-collimation of optical signals can be realized. The band diagrams and the equal-frequency contours of the PC structures we...

Prolonged treatment execution time is a concern in CyberKnife robotic radiosurgery. Beam reduction and node reduction technique, and monitor unit optimization methods are adopted to reduce the treatment time. Usage of single collimator in the CyberKnife treatment plan can potentially reduce collimator exchange time. An optimal single collimator, which yields an acceptable dose distribution alon...

X-ray luminescence computed tomography (XLCT) is an emerging hybrid imaging modality, which is able to improve the spatial resolution of optical imaging to hundreds of micrometers for deep targets by using superfine X-ray pencil beams. However, due to the low X-ray photon utilization efficiency in a single pinhole collimator based XLCT, it takes a long time to acquire measurement data. Herein, ...

UNLABELLED We present a new rodent SPECT system (U-SPECT-II) that enables molecular imaging of murine organs down to resolutions of less than half a millimeter and high-resolution total-body imaging. METHODS The U-SPECT-II is based on a triangular stationary detector set-up, an XYZ stage that moves the animal during scanning, and interchangeable cylindric collimators (each containing 75 pinho...

PURPOSE There are two collimation systems associated with the CyberKnife system, the fixed cone collimator and the Iris collimator. The Iris collimator is used more frequently because of its superior flexibility. However, sometimes treatments have to be canceled or postponed due to Iris collimator mechanical failures. The purpose of this study is to investigate the feasibility of switching coll...

PURPOSE Hypofractionated radiotherapy can reduce treatment durations and produce effects identical to those of conventionally fractionated radiotherapy for treating prostate cancer. Volumetric arc radiotherapy (VMAT) can decrease the treatment machine monitor units (MUs). Previous studies have shown that VMAT with multileaf collimator (MLC) rotation exhibits better target dose distribution. Thu...

Treatment of small animals with radiation has in general been limited to planar fields shaped with lead blocks, complicating spatial localization of dose and treatment of deep-seated targets. In order to advance laboratory radiotherapy toward what is accomplished in the clinic, we have constructed a variable aperture collimator for use in shaping the beam of microCT scanner. This unit can image...

To develop a second generation gamma-ray camera for industrial applications, various multiple-hole collimator designs that meet high-energy, high-intensity and far-eld imaging requirements have been studied. The collection of parallel holes each parallel to one another (parallel-hole, parallel collimator) is ineeective for imaging high energy far-eld sources, whereas a collimator with parallel ...