ABSTRACT
Accurate calibration of polarization-dependent optical elements is often necessary in optics experiments. A versatile polarimeter device to measure the polarization state of light is a valuable tool in these experiments. Here, we report a rotating waveplate-based polarimeter capable of complete Stokes vector analysis of collimated light. Calibration of the device allows accurate measurements over a range of wavelengths, with a bandwidth of >30 nm in this implementation. A photo-interrupter trigger system supplies the phase information necessary for full determination of the Stokes vector. An Arduino microcontroller performs rapid analysis and displays the results on a liquid crystal display. The Arduino can also be interfaced with a computer to store time series of Stokes vectors. The optical measurement apparatus of the polarimeter is compact and can be placed anywhere on an optical table on a single standard post. The components to construct the device are only a fraction of the cost of commercially available devices, while the accuracy and precision of the measurements are of the same order of magnitude.
ABSTRACT
OBJECTIVE: The purpose of this study was to evaluate the usefulness of a tissue marker clip in patients undergoing preoperative chemotherapy for breast carcinoma. MATERIALS AND METHODS: Between June 1996 and July 1998 (26 months), a tissue marker clip was placed in 29 patients with breast carcinoma who showed significant clinical response to preoperative chemotherapy. In these patients, 13 clips were placed stereotactically and 16 clips were placed using sonographic guidance. A retrospective review of these cases was made to evaluate helpfulness of the clip during preoperative needle localization. RESULTS: One patient relocated to another city, so surgical follow-up was available in 28 patients. Twenty-four of these 28 patients required preoperative wire localization and four still had a palpable tumor at the time of surgery. Preoperative wire localization would have been possible without any difficulty in eight patients (28.6%), possible but with some difficulty in six patients (21.4%), and impossible in 10 patients (35.7%) without the clip. Thus, clip placement was valuable in 16 (57.1%) of 28 patients at the time of preoperative needle localization. CONCLUSION: With the newer chemotherapeutic agents, the response of breast carcinoma to preoperative chemotherapy may be dramatic. In some patients, the tumor is no longer visible either on mammography or sonography, thus making the preoperative needle localization difficult or even impossible. By placing a radiopaque marker before the lesion becomes unidentifiable, one can confidently localize the tumor bed at surgery.
