Spatial Resolution Phantom Research Articles

Transmission CT reconstruction for offset fan beam collimation

Offset fan beam collimation has shown to be an effective means of obtaining transmission CT (TCT) data for SPECT attenuation correction. This paper compared three methods for handling the truncation problem and reconstructing this TCT data: iterative Os-FM and filtered backprojection (FBP) with two different pre-processing approaches. The first approach (FBP1) extends the fan beam projection by sinogram interpolation, and the second (FBP2) uses parallel beam rebinning. With a TCT spatial resolution phantom, FBP2 demonstrated a small degree of resolution loss which was equalized across methods after post-reconstruction filtering. With a thorax phantom, all methods performed adequately at high count level; however, at low count level, FBPI showed degraded image quality due to its handling of zero count projection bins. This finding was corroborated in patient images. It is concluded that at practical count levels, the iterative OS-FM method offers a clear advantage in TCT image quality compared to FBP methods.

The measurement of proton stopping power using proton-cone-beam computed tomography

A cone-beam computed tomography (CT) system utilizing a proton beam has been developed and tested. The cone beam is produced by scattering a 160 MeV proton beam with a modifier that results in a signal in the detector system, which decreases monotonically with depth in the medium. The detector system consists of a Gd2O2S:Tb intensifying screen viewed by a cooled CCD camera. The Feldkamp-Davis-Kress cone-beam reconstruction algorithm is applied to the projection data to obtain the CT voxel data representing proton stopping power. The system described is capable of reconstructing data over a 16 × 16 × 16 cm3 volume into 512 × 512 × 512 voxels. A spatial and contrast resolution phantom was scanned to determine the performance of the system. Spatial resolution is significantly degraded by multiple Coulomb scattering effects. Comparison of the reconstructed proton CT values with x-ray CT derived proton stopping powers shows that there may be some advantage to obtaining stopping powers directly with proton CT. The system described suggests a possible practical method of obtaining this measurement in vivo.

分解能ファントムによる MRI 装置のスライス厚の測定

A new measurement method of MR slice thickness is proposed. In this method, a high-contrast spatial resolution phantom, which is employed to evaluate the special resolution performance of MR equipment, is used. Slice thickness is obtained from the limit special frequency where the resolution pattern of the phantom vanishes on the image. New method is able to measure slice thickness accurately even a slice as thin as 2 or 3mm.