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PubMed · 6610037

Two algorithms for use with an orthogonal-view coded-aperture system.

R G Paxman·W E Smith·H H Barrett
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Abstract

ohe goal of single photon emission computerized tomography is to map out a three-dimensional distribution of a radionuclide that is concentrated in a structure of interest. There are a number of imaging modalities that achieve this goal with varying degrees of success. In this study, computer simulation is used to explore a novel imaging modality, orthogonal-view coded-aperture imaging. Furthermore, a comparison is made between two reconstruction algorithms, one being an iterative back-projection algorithm and the other a Monte Carlo algorithm. Finally, evidence is presented suggesting that a deficiency in the projection data due to multiplexing is less disturbing than that due to limited angular range.

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Evaluation Studies as TopicImage EnhancementMathematicsMonte Carlo MethodTomography, Emission-ComputedComparative StudyJournal ArticleResearch Support, U.S. Gov't, P.H.S.

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R G Paxman, W E Smith, H H Barrett. 1984. Two algorithms for use with an orthogonal-view coded-aperture system.. https://pubmed.ncbi.nlm.nih.gov/6610037/

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[Value of endorectal ultrasonography in the treatment of rectal tumors].

OBJECTIVES: To determine the diagnostic accuracy of endosonography and to appreciate its influence on the therapeutic strategy. METHODS: Sixty-two patients referred to the gastroenterology unit between April 1990 and February 1995 for a rectal tumor. Thirty-two patients did not receive any preoperative treatment (group A) and 30 were treated by radiotherapy or chemoradiotherapy before surgery (group B). Transrectal ultrasonography was performed with a Bruel and Kjaer device. RESULTS: Diagnostic accuracy for parietal infiltration was 84% for the entire series, 94% for group A and 73% for group B. Diagnostic accuracy of lymph node invasion was 71% for the entire series, 81% and 60% for groups A and B, respectively. It is highly probable that a histopathologic down-staging due to preoperative treatment explained the results in the group B. Using a pragmatic approach which combined the results for parietal infiltration and for lymph node invasion, transrectal ultrasonography would have correctly selected 20 among the 25 patients who could have been treated by local excision. The use of this same pragmatic approach in patients with high risk of local recurrence enabled correct selection of 26 among the 32 exposed patients. CONCLUSION: We conclude that transrectal ultrasonography: 1. is a reliable technique for the pretherapeutic staging of rectal cancer, especially for the assessment of parietal infiltration. Progress is needed for the diagnosis of lymph node invasion; 2. selects well the patients who can be treated by local excision; 3. is a reliable technique for the selection of patients who need preoperative treatment.

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