Biomedical subjects

Paul Dayton

Publications and source records attributed to Paul Dayton.

4 recordsLinked to original sources

PubMed2002

Nondestructive subharmonic imaging.

Ultrasound contrast agent microbubbles are intravascular agents that can be used to estimate blood perfusion. Blood perfusion may be estimated by destroying the bubbles in a vascular bed and observing the refresh of contrast agents back into the vascular bed. Contrast agents can be readily destroyed by traditional imaging techniques. The design of a nondestructive imaging technique is necessary for the accurate quantification of contrast agent refresh. In this work, subharmonic imaging is investigated as a method for nondestructive imaging with the contrast agent microbubble MP1950 (Mallinckrodt, Inc., St. Louis, MO). Optical observation during insonation, in conjunction with a modified Rayleigh-Plesset (R-P) analysis, provides insight into the mechanisms of and parameters required for subharmonic frequency generation. Subharmonic imaging with a transmission frequency that is the same as the resonant frequency of the bubble is shown to require a minimum pressure of insonation that is greater than the experimentally-observed bubble destruction threshold. Subharmonic imaging with a transmission frequency that is twice the resonant frequency of the bubble produces a subharmonic frequency response while minimizing bubble instability. Optimization is performed using optical experimental analysis and R-P analysis.

Blood Vessels↗

PubMed2002

Optical and acoustical interrogation of submicron contrast agents.

Unlike conventional ultrasound contrast agents with a diameter of several microns, in this paper we explore the use of submicron contrast agents for the detection and localization of lymph nodes. The submicron agents are gas-filled, double-walled microspheres that rupture when exposed to ultrasound energy at megahertz frequencies. In this study, three experimental systems are combined with model predictions to assist in understanding the response of these unique agents to a range of signal transmission parameters. Optical experimental results for each agent delineate the relative expansion as a function of acoustical peak negative pressure, pulse length, and center frequency. The optical images demonstrate an order of magnitude expansion in radius during the pulse rarefaction, in which the expansion magnitude is dependent on the transmitted pressure and frequency. Simulations using a modified Rayleigh-Plesset model predict an increasing relative expansion for the microbubbles (initial bubble radius ranging from 0.3-1.3 microm) with increasing pressure and decreasing initial radius. Acoustically recorded frequency spectra reveal the presence of harmonics for a range of transmitted pulses. In addition, in-vivo results from a normal canine model demonstrate marked contrast enhancement of first order lymph nodes. We hope to offer an alternative to present intra-operative procedures for sentinel node detection.

Animals↗

PubMedDate not supplied

Reduction of the intermetatarsal angle after first metatarsophalangeal joint arthrodesis in patients with moderate and severe metatarsus primus adductus.

A radiographic review of first metatarsophalangeal joint (MPJ) arthrodesis in patients who had preoperative intermetatarsal angles greater than 15 degrees is presented. The average reduction of the intermetatarsal angle was measured. Twenty-one patients with 22 fusions, with ages ranging from 43 to 79 years old, underwent first MPJ arthrodesis with screw or pin fixation as determined appropriate by their age and bone quality. Preoperative intermetatarsalangles averaged 17.27 degrees with a range of 15 degrees - 21 degrees. An overall reduction in the intermetatarsal angle of 6.41 degrees was noted. Mechanical factors affecting the reduction of the intermetatarsal angle following first MPJ arthrodesis are discussed.

Adult↗

PubMedDate not supplied

Use of the Z osteotomy for Tailor bunionectomy.

The authors present a unique use of the Z osteotomy in the fifth metatarsal for correction of Tailor bunion. The rotational capabilities of the Z osteotomy are exploited to provide correction of fifth metatarsal lateral bowing and to decrease intermetatarsal angles. The osteotomy is inherently stable, and the design facilitates internal fixation.

Foot Deformities↗