William L. Peters

Stereotactic Localization and Guidance Using a Machine Vision Technique

Machine vision techniques (video cameras) can be used to determine the three-dimensional position of objects. This transformation can be accomplished with standard mathematical algorithms. Initial accuracy tests of stereotactic localization with video cameras were performed using a standard Brown-Roberts-Wells (BRW) phantom simulator coupled with the BRW angiographic localizer. Localization accuracy was within 1.5 mm. Potential applications of machine vision techniques include freehand stereotactic localization of the position and orientation of surgical instruments. With sufficient computer speed these techniques can be used for continuous monitoring of the position of instruments within the cranial vault.

A Catalogue of the Ephemeroptera of the Indian Subregion

AbstractAll species of Ephemcroptera reported from the Indian Subregion of the Oriental Region are included in a catalogue along with pertinent references. A bibliography of literature on the mayflies of the Indian Subregion is included. Ephemera brunnea is proposed as a new name for Ephemera striata Ali, 1970 (preoccupied) and the genus Eatonia Ali, 1970 is synonymized with Isonychia Eaton, 1871.

Phylogenetic Relationships and Zoogeography of Cool-Adapted Leptophlebiidae (Ephemeroptera) in Southern South America

Twelve cool-adapted leptophlebiid genera are known to occur in southern South America. Analysis of the external morphology of both adults and nymphs indicated that cool-adapted South American leptophlebiids represent five distinct phyletic lineages, namely: the Hapsiphlebia,, Penaphlebia Atalonella, New Genus A and Meridialaris lineages. All of these, except the Penaphlebia lineage, presently include some genera from other areas of the Southern Hemisphere. Phylogenetic evidence indicates that cool-adapted South American Leptophlebiidae are related to confamilials occurring in the mountain waters of Southeastern Australia (including Tasmania), New Zealand, New Caledonia, Madagascar and South Africa. This study revealed that most genera from South America are more closely related to genera from Australia than to those occurring in the other continents.

Phylogenetic Relationships of the Leptophlebiidae of New Zealand (Ephemeroptera)

The leptophlebiid mayfly fauna of New Zealand at present consists of three named genera, of which two are clearly polyphyletic. Analysis of these elements and addition of undescribed genera indicate the presence of at least 14 genera. The genera can be divided into five lineages which exhibit varying degrees of radiation within New Zealand and which show evolutionary progression in a number of character states. Four genera appear to be most closely related to genera in New Caledonia, two to generic groups in Chile, and the remainder to other genera in New Zealand, except for one genus for which the nearest known relatives are in New Guinea.

Types and additional specimens of Ephemeroptera studied by Longinos Navás in the Museo de Zoología del Ayuntamiento, Barcelona, Spain

The types and additional specimens of Ephemeroptera which were studied by Longinos Navas and now deposited in the Museo de Zoologia del Ayuntamiento, Barcelona, are listed. For each of 97 species, full bibliographical references, collection localities, number of specimens, and type status are given.

Four New Genera of Leptophlebiidae (Ephemeroptera: Atalophlebiinae) from Southern South America

Abstract Four new monotypic genera of Leptophlebiidae, Archethraulodes, Demoulinellus, Rhigotopus and Secochela are established. Four new species are described. Three, Archethraulodes spatulus, Rhigotopus andinensis and Secochela illiesi are described from imagines. One, Demoulinellus coloratus is known from both imagines and nymph. Descriptions of the eggs of genera are included.

Three new genera of Leptophlebiidae (Ephemeroptera) from New Zealand

Abstract Three new genera—Austroclima, Mauiulus, and Cryophlebia—are established for species of Leptophlebiidae from New Zealand. The following new combinations are included: Austroclima sepia (Phillips) and Cryophlebia aucklandensis (Peters). Atalophlebioides sepia is redescribed as Austroclima sepia and a neotype is designated. Two new species, Austroclima jollyae and Mauiulus luma, are described. All life stages are described, and the relationships of each genus are discussed. Keys are given to male and female imagos, subimagos, and nymphs of each species, and to all New Zealand genera with species previously placed in Atalophlebioides.

New genera and species of Leptophlebiidae (Ephemeroptera) from New Zealand

Abstract New genera Isothraulus, Arachnocolus, and Penniketellus are established for three species of leptophlebiid mayfly from New Zealand. Each genus is monotypic and endemic to New Zealand. Isothraulus and Arachnocolus are known only from the northern North Island, and Penniketellus is known only from the Arthurs Pass area of the central South Island. The male and female imago, nymph, and egg of Isothraulus abditus n.sp., the male imago, male subimago, and nymph of Arachnocolus phillipsi n.sp., and the male and female imago, female subimago, and egg of Penniketellus insolitus n.sp. are described. The relationships of each genus and the ecology of nymphs of each species are discussed.

Three-Point Transformation for Integration of Multiple Coordinate Systems: Applications to Tumor, Functional, and Fractionated Radiosurgery Stereotactic Planning

The accuracy of an optimized three-point transformation method and its usefulness for integrating multiple independent coordinate systems has been described. Such integration can be implemented to accomplish complex stereotactic procedures which may require the use of multiple image data sets and combinations of frame-based and frameless stereotactic systems. This report details the application of an optimized transformation for intracranial lesion biopsy and/or resection, radiofrequency pallidotomy for treatment of Parkinsons disease, and fractionated stereotactic radiosurgery in a total of 68 patients. For approach to intracranial lesions, a noninvasive definition of image coordinate systems with multiple radiodense scalp markers was cross-registered with a standard stereotactic guidance system. This method allowed for elective acquisition of stereotactic image sets without requiring head frame fixation until the time of the operative procedure. In planning pallidotomy procedures, spatial cross-registration of CT and MR image coordinates were performed to target the posteroventral pallidum. CT coordinates were defined by the standard picket fence algorithm while MR images were referenced with multiple scalp markers. The addition of MR data sets improved anatomic resolution in the regions of the basal ganglia and commissures. Fractionated radiosurgery was accomplished by cross-registration of CT, MR, and plain radiographs using BRW localizers coupled with multiple scalp markers. A daily check of target positioning was performed with the BRW angiograph localizer. The average calculated error was 2.83 mm with a standard deviation of 1.66 mm which remained within the average scan slice thickness of 3.63 mm. In all cases surgical targets were reached without complication.(ABSTRACT TRUNCATED AT 250 WORDS)

Biosystematics of the Genus Massartella Lestage (Ephemeroptera: Leptophlebiidae: Atalophlebiinae) from South America

The genus Massartella and the species M. alegrettae Ulmer and M. brieni (Lestage) (= M. fruhstorfferi Ulmer, New Synonymy) are redescribed. The male subimagines of M. alegrettae and M. brieni and the nymph of the latter are described for the first time. A new species, M. venezuelensis is described from nymph and female subimago. Two immature Massartella nymphs, unassociated with adults and not identifiable to species, have been collected in Argentina. Illustrated keys for the nymphs and imagines are provided for the species.