Content-addressable data storage by use of volume holograms.

Data stored as volume holograms--optical interference patterns imprinted into a photosensitive storage material--can be accessed both by address and by content. An optical correlation-based search compares each input query against all stored records simultaneously, a massively parallel but inherently noisy analog process. With data encoding and signal postprocessing we demonstrate a holographic content-addressable data-storage system that searches digital data with high search fidelity.

[Endoscopic Therapy of Early Colorectal Cancer (pT1) - A Prospective Study]. / Prospektive Studie zur endoskopischen Therapie des kolorektalen pT1-Karzinoms.

INTRODUCTION: In a prospective study initiated in 1982, we have been investigating the question as to whether - and if so, which - pT1 carcinomas of the colorectum can be treated exclusively via the endoscope. METHOD: In the period between February 1, 1982 and April 30, 2001, a total of 5,470 polyps were removed endoscopically at the Medical Department I of the Klinikum Ludwigsburg. Among these lesions, a total of 144 (2.6 %) pT1 carcinomas were found in 141 patients. We were able to follow 120 patients with 123 pT1 carcinomas over a mean follow-up period of 46 months (range: 1-60). In low-risk situations (definitive removal in healthy tissue, G1-G2, no lymphatic involvement), endoscopic treatment alone usually represented sufficient treatment. In high-risk cases (removal in healthy tissue uncertain or negative, and/or lymphatic vessel involvement, and/or G3/G4), subsequent surgical resection was carried out. RESULTS: 64 cases were classified as high-risk, 59 as low-risk. Nevertheless, 9 patients with 10 low-risk carcinomas were submitted to surgery (young age, patient's own request). In none of these 10 cases was residual tumour or lymph node metastasis detected in the surgical specimen. 47 patients with 49 low-risk carcinomas were treated solely by endoscopic polypectomy using the diathermy snare, and 45 patients with 47 carcinomas remained recurrence-free during the follow-up period. In a single case, a local recurrence was detected 2 months after polypectomy and underwent curative resection. In another case, peritoneal carcinosis with tumour infiltrating into the colon developed 8 months after initial treatment; this, however, was most probably a recurrence of a previously operated carcinoma of the uterus. Among the high-risk cases, 10 were not submitted to surgery on account of advanced age and/or rejection of an operation by the patient; all remained recurrence-free. Among the surgically treated high-risk carcinomas, 3 surgical specimens contained residual tumour, while 2 revealed a lymph node metastasis. In our group of patients, no tumour-related mortality was seen among endoscopically treated patients. DISCUSSION: In the light of the fact that the reported mortality rate associated with open surgery for colorectal carcinoma is 3 % as compared with about 1 % risk of lymph node metastasis and 0,1 % mortality rate for the endoscopic modality, endoscopic removal of a pT1 tumour in a low-risk situation followed by appropriate surveillance can be considered as adequate treatment.