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R J Knowles

Publications and source records attributed to R J Knowles.

24 records · Page 2Linked to original sources
PubMedDate not supplied

Software reliability and algorithm validation for medical imaging: performance of common edge detection methods in nuclear medicine.

Ten common edge detection algorithms plus the NNA (nearest-neighbor algorithm) developed by the authors were evaluated under the conditions of low ID (information density) and low spatial resolution commonly found in nuclear images. Both phantoms and clinical images were used, and isolated regions as well as overlapping regions with variable backgrounds were analyzed at various ID's. Threshold criteria were also adaptively varied as a function of local ID. Performance was quantitated in terms of (a) accuracy of area determinations, (b) receiver operating characteristic operating points, and (c) shape preservation. With adaptive thresholding at high ID's, several of the methods performed well on isolated regions and adequately on overlapping regions, but only the NNA performed consistently at low ID's as well as at high ID's.

Humans↗
PubMedDate not supplied

Quantification of gray/white matter in neonates and adults.

Quantitation of gray/white matter is important in evaluation of cerebral blood flow, atrophy, and development of the brain. First-order statistical analysis of neonatal computed tomographic (CT) images revealed that there was only a 6 Hounsfield unit (H) difference between gray and white matter compared with the observed 3 H for the standard deviation over the field of a skull water phantom. Scene segmentation methods based on first-order statistics proved unsuccessful in separating gray and white matter. A new regional clustering algorithm based on local textural properties was developed for separation of these structures.

Adult↗
PubMedDate not supplied

Is Planorbarius metidjensis compatible with Schistosoma haematobium and S. bovis?

On the basis of laboratory snail infection experiments it is concluded that Planorbarius metidjensis is unimportant in the epidemiology of Schistosoma haematobium in North West Africa. 410 P. metidjensis Spain were exposed to 8 isolates of S. haematobium from Ghana, Kenya, Madagascar, Mauritius, Morocco, Tanzania, South Africa and Sudan. 50 P. metidjensis Morocco and 50 P. metidjensis Algarve were exposed to S. haematobium Morocco. All infections failed to develop to maturity. Serial sections of P. metidjensis Morocco infected with S. haematobium Morocco at 24 h, 48 h and 72 h post infection showed that 34% of the miracidia penetrated the snail epithelium, but young sporocysts were encapsulated and killed by an ameobocytic host response. Two hypotheses are postulated to explain the reports in the literature that P. metidjensis transmits S. haematobium. The dual infectivity of B. truncatus and B. africanus by S. haematobium from Guinea Bissau suggests that this isolate is probably an infraspecific hybrid with enhanced intermediate host infectivity. By analogy with work on Biomphalaria glabrata and S. mansoni, field observations of P. metidjensis transmitting S. haematobium could be explained if the snail had been previously infected with a compatible digenean, thus rendering a refractory snail into a susceptible snail. S. bovis Spain is compatible with P. metidjensis Morocco, Portugal and Spain with 14.3%, 29.2% and 73.3% of the snails respectively surviving the prepatent period becoming infected. P. metidjensis Spain is refractory to S. bovis Iran and Sudan. Thus, P. metidjensis may be important in the epidemiology of S. bovis in the Iberian Peninsula and North West Africa.

Animals↗