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We present the absorption spectroscopy and continuous-wave laser operation of Tm:YLF at cryogenic temperatures. At 100 K, a maximum output power of 2.55 W corresponding to a maximum slope efficiency of 22.8% is obtained using 15% output coupling transmission. The output laser wavelength is centered at 1877 nm for Elc.

Influence of the prominent charging effect on the precision of measuring EUV mask features using CD-SEM was studied. The dimensions of EUV mask features continuously measured by CD-SEM gradually varied because of the charging. The charging effect on the measured CD variation mainly consists of three factors: 1) shift of the incident points of primary electrons deflected by the surface charge, 2) distortions of the profiles of secondary electron signal intensity caused by the deflection of the secondary electrons, 3) deviation of the maximum slope points of the secondary electron signal intensity due to the variation of the image contrast. For those three factors described above, how the material constant affect the CD variation measured by CD-SEM is discussed.

A recently introduced dynamic T1 mapping technique was used to investigate changes of tumor microcirculatory parameters in 16 patients with clinically staged T3) primary rectal carcinoma during a course of preoperative combined chemoradiation. For dynamic T1 mapping an ultra-fast snapshot FLASH T1 mapping sequence was implemented on a 1.5T whole body MR scanner. Acquiring a series of T1 maps contrast media (CM) uptake and washout over an examination time of 40 min was monitored. From the obtained series of T1-maps perfusion-indices (PI) were calculated as the ratio of maximum slope of the tumor CM curve and the maximum of the arterial CM curve. Using pathologic classification of the resected tumors after therapy the patient group could be divided into patients with and without response to therapy. It was found that mean pre-therapy PI values of tumors showing therapy-response were significantly lower than for tumors without no therapy-response. In addition a different behavior of PI distributions within tumors for both groups was observed. The presented study indicates that PI values and their distributions within a tumor seem to be of predictive value for therapy outcome of preoperative therapy in patients with primary rectal carcinoma.

The purpose of this paper is to present results of a study comparing CT brain perfusion image calculated using the maximum slope and deconvolution method on data from 32 patients. The 32 patients were organized into two groups. One group was obtained using a 4cc/sec contrast injection rate and 10 sec injection period; the other group was obtained using a 6cc/sec injection rate and 7 sec injection period. All clinical data were analyzed using both the maximum slope and deconvolution methods. Perfusion maps computed from the two methods were reviewed by radiologists. The contrast enhanced CT data were noisy, especially in the white matter area. Our results showed that, for both methods, perfusion maps from 4cc/sec injection were noisier than those using a 6cc/sec injection. However, both 4cc/sec and 6cc/sec produced useful diagnostic images. Our qualitative side-by-side studies also showed that perfusion images from the maximum slope and deconvolution are both clinically useful and substantially equivalent.

We report the operation of a passively Q-switched diode end pumped Nd3+:KGW laser, which was obtained by using a Cr4+:YAG or Cr4+:GGG saturable absorbers in the multi-kHz frequency domain. The free-running (with maximum slope efficiency of 46%), and the passively Q-switched characteristics of Nd:KGW were investigated and the use of Nd:KGW as microlasers will be discussed.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The IDS Summation model was used to explain the perception of defocused symbols. Twelve different computer-generated words were used as stimulus for sharpness evaluation by a group of observers and the result compared with themodel response. obtained by software implementation. The symbol luminance slope was used as parameter. The correlationcoefficient is greater than 0.99.1. INTRODUCTION The border definition of a visual object is an important parameter to characterise the performance of the visual system. The maximum slope of the border profile has proved to be an appropriate physical parameter to evaluate it. and hasbeen used to study the response of the visual sysleni to a set of defocused symbols' . In addition to other models2 based on the superposition of excitatory and inhibitory zones of the receptive field. the use of the Cornsweet &Yellot's "Intensity- dependent Spatial Summation (IDS)" model3 is proposed in this paper. The IDS model is based on a single assumption: the output image is the sum of the nonnegative point spreadfunction generated around each input point. whose height is directly proportional to image intensity. In spite of the