Hyperspectral phasor analysis enables multiplexed 5D in vivo imaging.

Time-lapse imaging of multiple labels is challenging for biological imaging as noise, photobleaching and phototoxicity compromise signal quality, while throughput can be limited by processing time. Here, we report software called Hyper-Spectral Phasors (HySP) for denoising and unmixing multiple spectrally overlapping fluorophores in a low signal-to-noise regime with fast analysis. We show that HySP enables unmixing of seven signals in time-lapse imaging of living zebrafish embryos.

Association of Complete Radiologic and Pathologic Response following Locoregional Therapy before Liver Transplantation with Long-Term Outcomes of Hepatocellular Carcinoma: A Retrospective Study.

PURPOSE: To evaluate long-term outcomes of patients with hepatocellular carcinoma (HCC) who show a complete response (CR) vs non-CR on pretransplantation imaging studies or pathologic evaluation of liver explants after locoregional therapy (LRT) before liver transplantation. MATERIALS AND METHODS: Patients listed for liver transplantation for HCC (March 1998 to December 2010) undergoing LRT with available multiphase MR/CT imaging before transplantation were included. Pathologic response was evaluated based on liver explant pathology. A total of 108 patients (17 women; 16%) met the inclusion criteria. RESULTS: Radiologic CR was achieved in 65 patients (60%) vs non-CR in 43 (40%), and pathologic CR was achieved in 36 patients (33%) vs non-CR in 72 (67%). Mean 5-year overall survival (OS) from the time of listing and recurrence-free survival (RFS) after liver transplantation were significantly better for patients with pathologic CR vs non-CR on explant pathology (OS, 83.3% vs 65.2% [28% difference; P = .046]; RFS, 80.6% vs 62.5% [29% difference; P = .045]). Mean 5-y OS and RFS were not significantly different between patients with radiologic CR or non-CR on pretransplantation imaging (OS, 75.4% vs 65.1% [P = .12]; RFS, 74% vs 62.8% [P = .17]). CONCLUSIONS: Achievement of a pathologic CR vs non-CR in response to LRT before liver transplantation for HCC is associated with improved OS from time of listing and improved RFS after liver transplantation. However, current imaging paradigms fall short of accurate delineation of response to LRT, resulting in poor correlation of outcomes between pathologic and radiologic CR.

Deep and fast live imaging with two-photon scanned light-sheet microscopy.

We implemented two-photon scanned light-sheet microscopy, combining nonlinear excitation with orthogonal illumination of light-sheet microscopy, and showed its excellent performance for in vivo, cellular-resolution, three-dimensional imaging of large biological samples. Live imaging of fruit fly and zebrafish embryos confirmed that the technique can be used to image up to twice deeper than with one-photon light-sheet microscopy and more than ten times faster than with point-scanning two-photon microscopy without compromising normal biology.

Patient-Centered and Specialty-Specific Case Work-Up: An Effective Method for Teaching Appropriateness of Imaging to Medical Students.

RATIONALE AND OBJECTIVES: Our institution has developed a mini-course program within the diagnostic radiology elective curriculum that promotes active learning, using patient cases specifically tailored to students' future specialties. The purpose of this study is to evaluate the effectiveness of this mini-course on medical student knowledge of imaging appropriateness and attitude toward radiologist consultation. MATERIALS AND METHODS: During each month-long radiology elective course, students were divided into teams of up to four students based on their specialty interest and assigned recent patient cases with imaging findings relevant to their specialties. The students researched their customized patient cases, integrated pertinent clinical and imaging findings, and presented their findings in a final preceptor-led session. A five-point Likert-type item preprogram and postprogram survey assessing knowledge of imaging appropriateness and attitude toward radiologist consultation was sent to the enrolled medical students. RESULTS: Out of 36 medical students, 33 (92%) completed the preprogram survey and 31 (86%) completed the postprogram survey. Students reported improved confidence in knowledge of imaging appropriateness, such as indications for intravenous contrast (p < 0.0005) and oral contrast (p < 0.0005). Furthermore, students reported an improved understanding of how to utilize radiologists (p < 0.005) and how to provide pertinent clinical historical information when requesting a radiology exam (p < 0.0005). Students reported that researching the patient's historical and clinical information in conjunction with the radiology images made them more invested in the case. CONCLUSION: Assigning customized patient cases to medical students on diagnostic radiology elective, tailored to their future specialties, is an effective and active way to teach imaging appropriateness and to improve attitudes toward radiologist consultation.

Electrically pumped two-dimensional Bragg grating lasers.

We demonstrate electrically pumped InGaAsP two-dimensional Bragg grating (2DBG) lasers with two line defects. The 2DBG structure uses a weak 2D index perturbation surface grating to control the optical modes in the plane of the wafer. Measurements of the 2DBG lasers show that modal control in both the longitudinal and transverse directions is due to the gratings and defects. The 2DBG lasers are promising candidates for single-mode, high power, and high efficiency large-area lasers.

Ring fiber resonators based on fused-fiber grating add-drop filters:application to resonator coupling.

We introduce a fiber ring optical resonator based on adiabatic fused-fiber grating couplers. The coupling of a through fiber to the resonator is controlled by the strength of the fiber Bragg gratings. By using two of these couplers and incorporating erbium-doped (ED) fiber in the ring, we control the internal loss of the ring by pumping the ED fiber. The transmission spectra of the through port and the drop port of a four-port configuration, a ring coupled to two waveguides, are measured. We show that the loss/coupling ratio of the ring-fiber system can be changed and thus that the transmission properties of the fiber can be controlled.

Engineering transverse Bragg resonance waveguides for large modal volume lasers.

We recently analyzed a new class of laser amplifier based on transverse Bragg reflection. We show that the unique properties of Bragg confinement make it possible through modal loss discrimination to achieve single-transverse-mode operation with transverse modal size that is an order of magnitude larger than in lasers that depend on total internal reflection for transverse confinement.

Loss optimization of transverse Bragg resonance waveguides.

Coupled-mode theory was used to analyze guiding in a transverse Bragg resonance (TBR) waveguide structure composed of a GaAs substrate with air holes. This analysis predicts that propagation loss will be minimized for discrete widths of the waveguide core. Although the coupled-mode theory is normally applied to structures with small index perturbations, two-dimensional finite-difference time-domain simulations of the TBR waveguide show good quantitative agreement with the coupled-mode predictions, and these results corroborate the previously predicted existence of discrete core widths for low-loss propagation.