Design and analysis of a diffractive optical filter for use in an optoelectronic error-diffusion neural network

The design, fabrication, experimental characterization, and system-performance analysis of a diffractive optical implementation of an error-diffusion filter for use in digital image halftoning is reported. A diffractive optical filter was fabricated as an eight-level phase element that diffuses the quantization error nonuniformly in both the weighting and the spatial dimensions, according to a prescribed algorithm. Ten identical diffractive elements were fabricated on ten different wafers and subsequently characterized experimentally. A detailed error analysis including both fabrication and instrumentation errors was carried out to quantify the performance of the fabrication process as well as the expected system performance of the filters. Halftone system performance was evaluated by use of the experimental filter's performance and both quantitative and qualitative performance metrics. The results of this analysis demonstrate that multiple identical copies of a diffractive optical filter can be produced with sufficient accuracy that no loss in the halftoning system performance results.     

Role of carotid sonography as a first examination in the evaluation of patients with transient ischemic attacks and strokes: benefit in relation to age

PURPOSE: We studied the influence of age on the utility of carotid sonography in patients with transient ischemic attacks and strokes. METHODS: The results of Doppler ultrasound examinations of the carotid arteries in 613 consecutive patients with transient ischemic attacks (n = 450) or strokes (n = 163) were analyzed for different age groups. For each patient, the grade of stenosis was scored for the ipsilateral internal carotid artery. The results of the ultrasound examinations were correlated with angiographic findings and findings at endarterectomy. The extent of atherosclerosis for each age group was expressed as the ratio between the number of grade II-IV stenoses (> or = 50%) in the carotid arteries and the number of patients in that group ("atherosclerosis ratio"). RESULTS: Under the age of 40 years, high-grade atherosclerotic stenoses were not found. However, 3 relatively young patients had dissections of the internal carotid arteries. The atherosclerosis ratio exceeded 0.5 for age groups 65-69 years through 80+ years. Among the patients with high-grade stenoses, ischemic heart disease prevented endarterectomy in 63% of patients in age group 80+ years, 44% in age group 75-79 years, and 26% in age group 70-74 years. CONCLUSIONS: Carotid sonography did not detect any significant atherosclerotic changes in young patients but was useful for diagnosing other etiologies of ischemic cerebral disease, eg, carotid dissection. At the other end of the spectrum, the impact of carotid sonography on patient management appears to be limited in patients over the age of 70 years. Carotid sonography seems to be most useful for patients 40-69 years old.     

The possible advantage of hyperfractionated thoracic radiotherapy in the treatment of locally advanced nonsmall cell lung carcinoma: results of a North Central Cancer Treatment Group Phase III Study

BACKGROUND: A three-arm Phase III randomized trial was performed to compare response rates, time to local or distant progression, and survival for patients with unresectable (Stage IIIA or IIIB) nonsmall cell lung carcinoma treated with standard fractionated thoracic radiotherapy (SFTRT) versus accelerated hyperfractionated thoracic radiotherapy (AHTRT) with or without combination etoposide and cisplatin chemotherapy. METHODS: This trial was initiated in 1992 by the North Central Cancer Treatment Group. Patients with Stage IIIA or IIIB nonsmall cell lung carcinoma were eligible. They were randomly assigned to either SFTRT (6000 centigray [cGy] in 30 fractions) or AHTRT (150 cGy twice daily to a total dose of 6000 cGy, with a 2-week break after the initial 3000 cGy); the AHTRT was given alone or with concomitant cisplatin (30 mg/m2, Days 1-3 and 28-30) and etoposide (100 mg/m2, Days 1-3 and 28-30). RESULTS: A total of 110 patients were entered on study. Eleven patients were declared ineligible or off study on the day of study entry. This analysis was confined to the 99 eligible patients. This article reports mature follow-up, because more than 80% of the patients have died. The median follow-up of living patients was 2.5 years. There were suggestions of improvement in the rates of freedom from local recurrence and survival for patients treated with AHTRT (with or without chemotherapy) as opposed to SFTRT (P = 0.06 and P = 0.10, respectively). The improvement in survival associated with AHTRT (with or without chemotherapy) was statistically significant for the subgroup of patients with nonsquamous cell carcinoma after adjustment for other potentially confounding factors (P = 0.02). No differences in freedom from systemic progression or survival were found in a comparison of AHTRT with chemotherapy and AHTRT without chemotherapy. CONCLUSIONS: These results suggest that treatment of Stage IIIA or IIIB nonsmall cell lung carcinoma with AHTRT with or without chemotherapy may improve freedom from local progression and survival as compared with SFTRT, especially for patients with nonsquamous cell carcinoma. The statistical powers to detect the observed differences in median time to local progression and survival were approximately 55% and 35%, respectively. Therefore, further investigation comparing SFTRT with AHTRT is warranted.