Record power, ultra-broadband supercontinuum source based on highly GeO2 doped silica fiber

We demonstrate highly germania doped fibers for mid-infrared supercontinuum generation. Experiments ensure a highest output power of 1.44 W for a broadest spectrum from 700 nm to 3200 nm and 6.4 W for 800 nm to 2700 nm from these fibers, while being pumped by a broadband Erbium-Ytterbium doped fiber based master oscillator power amplifier. The effect of repetition frequency of pump source and length of germania-doped fiber has also been investigated. Further, germania doped fiber has been pumped by conventional supercontinuum source based on silica photonic crystal fiber supercontinuum source. At low power, a considerable broadening of 200-300 nm was observed. Further broadening of spectrum was limited due to limited power of pump source. Our investigations reveal the unexploited potential of germania doped fiber for mid-infrared supercontinuum generation. These measurements ensure the potential of germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being by pumped a 1060 nm or a 1550 nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized supercontinuum light source based on silica and germania fiber ever demonstrated to the date.

Freestanding sample holder for ultrafast optical spectroscopy at low temperatures

Ultrafast optical spectroscopy techniques are often employed to gain information about samples that are liquid at room temperature and frozen at cryogenic temperatures. However, the measurements suffer from the presence of unwanted, non-resonant signals originating in the sample cell walls. Most of these artifacts can be avoided in the measurements performed at room temperature by using liquid jet systems, i.e., by removing the sample cell. However, these systems cannot be used in low temperature measurements, when the sample is frozen. Herein we describe a freestanding sample holder that allows low temperature ultrafast spectroscopy measurements free of artifacts caused by the sample cell.

Abstract P5-14-04: Preoperative single-fraction partial breast radiotherapy – Initial results from a novel phase I dose-escalation protocol with exploration of radiation response biomarkers

Purpose/Objectives(s): Women with biologically favorable early stage breast cancer are increasingly treated with accelerated partial breast techniques. However, many alternative techniques require costly specialized equipment not routinely available in most radiation oncology facilities. In addition, suboptimal cosmetic outcomes have been reported with the external beam technique, possibly related to large post-operative treatment volumes. To address these issues, we designed a phase I dose-escalation protocol to determine the maximally tolerated dose (MTD) of a single radiosurgery treatment delivered preoperatively to the intact tumor plus a small margin.

Materials/Methods: Women aged 55 or older with clinically node negative, ER and/or PR+, HER2-, T1 invasive carcinomas were enrolled (n = 26). Patients with low/intermediate grade in situ disease <2cm were also included (n = 6). Breast MRI was required for target volume delineation. An intensity-modulated treatment plan was designed to deliver 15, 18, or 21Gy in a single fraction. An additional breast MRI, including T1-weighted, T2-weighted, diffusion-weighted and dynamic-contrast enhanced imaging, was obtained prior to lumpectomy which took place within 10 days of radiation treatment. Acute toxicity was assessed 3-4 weeks after radiation and any grade 3/4 toxicity possibly, probably, or definitely related to treatment was considered dose limiting.

Tumor tissue was obtained from diagnostic and lumpectomy specimens. Immunohistochemistry (IHC) for Fas was performed on paraffin-embedded samples before and after radiation. A histoscore was created using the average membrane and cytoplasmic staining intensity multiplied by the percentage of positive cells.

Results: Thirty-two women were treated, 8 each at the 15, 18, and 21Gy dose levels with an additional expansion cohort at the final 21Gy dose level. The maximally tolerated dose was not reached. Three patients required post-operative conventional radiation due to high-risk tumor features (ex. larger primary, nodal involvement).

At a median follow-up of 6.8 months, primarily mild toxicities (grade 1-2 dermatitis, fibrosis, and pain) were noted. At 6 months (n = 20), all reported cosmetic outcomes are excellent or good. At 12 months (n = 10), 80% are excellent or good. Both patients with a fair/poor cosmetic outcome received radiosurgery plus post-operative conventional treatment; one experienced grade 3 breast atrophy. There have been no local or distant recurrences to date.

Post-treatment MRIs were obtained in 20/32 patients, with early indicators of decreased cell density and increased vascular permeability. Sixteen patients had evaluable paired IHC and six demonstrated significant Fas up-regulation after radiation. The mean combined post-treatment histoscore was about twice as high as the mean pre-treatment score.

Conclusion: Preoperative stereotactic radiotherapy to the intact breast tumor can be delivered with widely available clinical tools in a convenient single fraction, and provides a unique opportunity to study breast cancer radiation response. 21Gy did not yield dose-limiting toxicity and will be utilized for future studies.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-14-04.