Date

September 2013

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Biomedical Engineering

Institution

Oregon Health & Science University

Abstract

In the U.S. in 1996, the last year the National Survey of Ambulatory Surgery was completed, 341,000 outpatient lumpectomies were performed. Positive margins following lumpectomy in approximately 30 %, of procedures, the patient usually undergoes a second surgery to clear the margins. The long term goal of this work was to develop a simple, practical tool to improve the outcome of lumpectomy surgeries. An optical wire was developed to make the breast tissue surrounding a lesion glow red by placing a light source within the lesion.It was hypothesized that light guided lumpectomies could result in a decrease in positive margins, fewer procedures, reduced cost, and better cosmetic outcomes. The goals of the work presented here were to develop an optical wire, clinically evaluate the feasibility of light guided lumpectomies, and to quantitatively determine the distance from the tissue surface to a light source within. An optical wire was designed with a 3m optical _ber axially attached to a standard localization wire. After placement of the wire, the lumpectomy could be performed using standard methods but with the additional assistance of being able to see a red glow-ball of light surrounding the lesion. A small clinical study of light guided lumpectomy in 8 patients was conducted. During surgery, a glow-ball of red light provided immediate visualization at the end of the optical wire which the surgeon was able use to estimate proximity to the wire tip. Seven of the eight lumpectomies resulted in negative margins upon pathology review. Use of the optical wire resulted in good clinical outcomes, but it was re-designed to be more comfortable for the patient and easier to use. The intensity of the visible light during lumpectomy was variable and not a reliable indicator of distance from the light source. In addition to a visual guide, the operating surgeon also wanted to know exactly how far the dissection plane was from the lesion. It was hypothesized that the distance could be determined using the light emitted from the optical wire with frequency domain measurements. In scattering media, sinusoidally modulated light becomes demodulated and a phase lag develops between the source and the propagating wave. A multi detector probe is proposed to be used in conjunction with light-guided lumpectomy to give the operating surgeon a quick measurement of distance within the breast without a-priori knowledge of the tissue optical properties. An expected relative error of 1% from the proposed method was determined. A fiber coupled optical system was assembled to modulate the intensity of a red laser diode with a network analyzer. The detected signal was compared to the source and a phase lag between the two was measured. As expected, the phase lag measured through optical phantoms was found to be in agreement with the diffusion theory approximation and found to be linear as a function of distance from the source with a deviation from linearity of 0.1 deg/mm. Three prophylactic mastectomy specimens were also tested after surgery and before examination by pathology. During the investigations, an optical fiber was inserted stereotactically through a needle and the phase lag from the edge of the tissue to the fiber tip was measured with another optical fiber. The phase lag was used to determine the distance between the fibers. Optical measurements of the distance between source and detector were within 15% of the actual value.

Identifier

doi:10.6083/M4J38QK5

School

School of Medicine

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