ABSTRACT
Using near-field scanning microscopy, we demonstrate that a 15-µm zone plate fabricated in a 70-nm chromium film sputtered on a glass substrate and having a focal length and outermost zone's width equal to the incident wavelength λ = 532 nm, focuses a circularly polarized Gaussian beam into a circular subwavelength focal spot whose diameter at the full-width of half-maximum intensity is FWHM = 0.47λ. This value is in near-accurate agreement with the FDTD-aided numerical estimate of FWHM = 0.46λ. When focusing a Gaussian beam linearly polarized along the y-axis, an elliptic subwavelength focal spot is experimentally found to measure FWHMx = 0.42λ (estimated value FWHMx = 0.40λ) and FWHMy = 0.64λ. The subwavelength focal spots presented here are the tightest among all attained so far for homogeneously polarized beams by use of non-immersion amplitude zone plates.
ABSTRACT
The development of the method of complex radiation treatment at the Institute in 1946-1980 is followed. Clinical data on 2,313 patients with stage I, II and III carcinoma of the uterine cervix formed the basis of a multifactor analysis. Five-year survival rates and frequency of complications following different modalities of radiation therapy were studied. The 5-year survival rate in cases of orthovolt X-ray therapy or intracavitary gammatherapy from unfixed sources was 54.2% (all stages of carcinoma). The results were improved by 11.9% (66.3% versus 54.2%) when remote gammatherapy using increased focal doses in the zones of parametral and lymphogenic metastatic spread was employed and the exposed volume and the focus of lesion were properly aligned. The development of pretreatment X-ray topometric procedures was followed by a further improvement in the results (72.2% as compared with 60.7%), particularly in cases of stage III carcinoma. The 5-year survival rate rose to 80.1% (all stages) as a result of application of complex radiation therapy preceded by suitable topometric preparation.
