purpose: to report a case who had undergone lasik in his right eye and prk in the fellow eye for correction of equivalent myopia but developed progressive post-operative keratectasia only in the right eye. patient and findings: a 30-year-old man had undergone lasik in right eye 3 years ago for correction of refractive error of -1.75  -1.50@48° and prk in left eye 2 years ago for correction of r...

A fast algorithm termed the direct iterative search (DE) is proposed to design the optimal phase-only filters (F’OFs) with a high Homer efficiency and high-signal-to-noise ratio ( SNR) . The DIS optimizes the phase and passband of POF in the sense of maximizing the correlation peak of the signal image and minimizing the noise passage. Simulation results show the capability of the DIS for achiev...

in present pet/ct scanners, pet attenuation correction is performed by relying on the information given by ct scan. in the ct-based attenuation correction methods, dual-energy technique (dect) is the most accurate approach, which has been limited due to the increasing patient dose. in this feasibility study, we have introduced a new method that can implement dual-energy technique with only a si...

In most primal-dual interior point methods, a sequence of weighted normal equations are solved, where the only change from one problem to the next are the weights and the right hand side. Solving the normal equations alternating between a direct method and an iterative method was introduced in Wang and O'Leary 11]. A class of preconditioners based on a low-rank correction of a Cholesky factoriz...

Background Coronary atherosclerosis is not necessarily stenotic, due to outward remodeling of the vessel wall. Plaque burden correlates with risk of coronary disease (Kubo et al, J Am Coll Cardiol 2007) and direct visualization is desired. A 3D flow independent approach for vessel wall imaging was proposed recently (Andia et al, MRM 2013), based on subtraction of data with (T2prep(+)) and witho...

Aberration correction leads to a substantial improvement in the interpretable resolution of Transmission Electron Microscopes. Electron optical correctors based on two strong hexapole elements linked through a round lens transfer doublet enables direct correction of all axial aberrations to third order. Subsequent, indirect computational analysis of a focal or tilt series of images offers the p...

Data correction is probably the least favourite activity amongst users experimenting with small-angle X-ray scattering: if it is not done sufficiently well, this may become evident only during the data analysis stage, necessitating the repetition of the data corrections from scratch. A recommended comprehensive sequence of elementary data correction steps is presented here to alleviate the diff...