Ramesh Raghavachari

Front Matter: Volume 7190

This PDF file contains the front matter associated with SPIE Proceedings Volume 7190, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing

Synthesis and characterization of upconversion emission on lanthanides doped ZrO 2 nanocrystals coated with SiO 2 for biological applications

Er doped and Yb-Er-Tm codoped ZrO2 nanocrystals of average 80 nm in size were prepared by a sol-gel process with the presence of nonionic (PLURONIC F-127) surfactant, and the up-conversion emission was characterized under IR (980 nm) excitation. The effect of the codoped conditions on the crystalline structure and photoluminescence properties were studied. A strong green emission was produced with 5 mol %, 0.2 mol %, 0.01 mol % of Yb3+-Er3+-Tm3+ codoped ZrO2 respectively. It was prepared Er doped ZrO2 -SiO2 core-shell and SiO2 coated Er doped ZrO2 in 2-propanol and water, respectively. The presence of the silica shell of average of 15 nm in thickness has been confirmed by transmition electron microscopy. Photolumineiscence studies show that the silica shell does not affect the emission when the nanoparticles are excited with 980 nm. The up-converting Yb3+-Er3+-Tm3+ codoped ZrO2 nanocrystal has showed to be a powerful tool to future detection techniques. The viability of the nanoparticles of codoped ZrO2 for biological imaging was confirmed by multiphotonic microscope imaging of cervix tissue with inserted codoped ZrO2 nanoparticles. The cervix tissue has a moderate dysplasia. The nanoparticles were introduced at 80 % of the tissue depth (5 μm) without being functionalized.

Depth-of-focus extended chromatic dual-foci OCT (Conference Presentation)

The depth scanning range of high-resolution OCT is limited by its depth-of-focus (DOF). To solve this problem, we developed a chromatic dual-foci technology to maintain a transverse resolution of 1-2 um over a DOF of about 300 micrometers, which is 2-3 times larger than the single-focus OCT system. In this OCT system, a supercontinuum source is used to provide illumination from 700 to 1600 nm. The interference fringe is detected by a dual-spectrometer system, which engages a Si camera and an InGaAs camera. The Si camera detects the spectral single from 700 to 950 nm, and InGaAs camera covers 1100 to 1600 nm spectral range. As the focal region for long wavelength section is deeper than the short one, the two spectral sections are processed separately to form two OCT images of different depths in the sample. After combining the two images, we obtained DOF extended OCT images.

Visibility of solid and liquid fiducial markers used for image-guided radiation therapy on optical coherence tomography: an esophageal phantom study (Conference Presentation)

Radiation therapy (RT) is used in operable and inoperable esophageal cancer patients. Endoscopic ultrasound-guided fiducial marker placement allows improved translation of the disease extent on endoscopy to computed tomography (CT) images used for RT planning and enables image-guided RT. However, microscopic tumor extent at the time of RT planning is unknown. Endoscopic optical coherence tomography (OCT) is a high-resolution (10-30µm) imaging modality with the potential for accurately determining the longitudinal disease extent. Visibility of fiducial markers on OCT is crucial for integrating OCT findings with the RT planning CT. We investigated the visibility on OCT (NinePoint Medical, Inc.) of 13 commercially available solid (Visicoil, Gold Anchor, Flexicoil, Polymark, and QLRAD) and liquid (BioXmark, Lipiodol, and Hydrogel) fiducial markers of different diameter. We designed and manufactured a set of dedicated Silicone-based esophageal phantoms to perform imaging in a controlled environment. The esophageal phantoms consist of several layers with different TiO2 concentrations to simulate the scattering properties of a typical healthy human esophagus. Markers were placed at various depths (0.5, 1.1, 2.0, and 3.0mm). OCT imaging allowed detection of all fiducial markers and phantom layers. The signal to background ratio was 6-fold higher for the solid fiducial markers than the liquid fiducial markers, yet OCT was capable of visualizing all 13 fiducial markers at all investigated depths. We conclude that RT fiducial markers can be visualized with OCT. This allows integration of OCT findings with CT for image-guided RT.

Surgical instrument biocontaminant fluorescence detection in ambient lighting conditions for hospital reprocessing and sterilization department (Conference Presentation)

Hospitals currently rely on simple human visual inspection for assessing cleanliness of surgical instruments. Studies showed that surgical site infections are in part attributed to inadequate cleaning of medical devices. Standards groups recognize the need to objectively quantify the amount of residues on surgical instruments and establish guidelines. We developed a portable technology for the detection of contaminants on surgical instruments through fluorescence following cleaning. Weak fluorescence signals are usually detected in the obscurity only with the lighting of the excitation source. The key element of this system is that it works in ambient lighting conditions, a requirement to not disturb the normal workflow of hospital reprocessing facilities. A biocompatible fluorescent dye is added to the detergent and labels the proteins of organic residues. It is resistant to the harsh environment in a washer-disinfector. Two inspection devices have been developed with a 488nm laser as the excitation source: a handheld scanner and a tabletop station using spectral-domain and time-domain ambient light cancellation schemes. The systems are eye safe and equipped with image processing and interfacing software to provide visual or audible warnings to the operator based on a set of adjustable signal thresholds. Micron-scale residues are detected by the system which can also evaluate soil size and mass. Unlike swabbing, it can inspect whole tools in real-time. The technology has been validated in an independent hospital decontamination research laboratory. It also has potential applications in the forensics, agro-food, and space fields. Technical aspects and results will be presented and discussed.

Front Matter: Volume 8573

This PDF file contains the front matter associated with SPIE Proceedings Volume 8573, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Front Matter: Volume 8215

This PDF file contains the front matter associated with SPIE Proceedings Volume 8215, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Front Matter: Volume 6867

This PDF file contains the front matter associated with SPIE Proceedings Volume 6867, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Front Matter: Volume 6849

This PDF file contains the front matter associated with SPIE Proceedings Volume 6849, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.