Statistically based postprocessing of phylogenetic analysis by clustering.

Motivation: Phylogenetic analyses often produce thousands of candidate trees. Biologists resolve the conflict by computing the consensus of these trees. Single-tree consensus as postprocessing methods can be unsatisfactory due to their inherent limitations.

Precise measurement of vertebral bone density using computed tomography without the use of an external reference phantom.

Bone density measurement by quantitative computed tomography (QCT) commonly uses an external reference phantom to decrease scan-to-scan and scanner-to-scanner variability. However, the peripheral location of these phantoms and other phantom variables is also responsible for a measurable degradation in accuracy and precision. Due to non-uniform artifacts such as beam hardening, scatter, and volume averaging, the ideal reference phantom should be as close to the target tissue as possible.

The influence of modulation transfer function shape on computed tomographic image quality.

The influence of modulation transfer function (MTF) shape on computed tomographic (CT) image quality was studied by computer simulation of a recently proposed x-ray detector with a nonuniform, shaped response to radiation. The shaped detector, while maintaining a high value of limiting spatial resolution, was shown to depress MTF and signal-to-noise ratio values at moderate spatial frequencies. This led to a significant loss of sharpness on noise-free images.