ABSTRACT
Goal: To enhance endovascular navigation using surgical guidewires and the use of ionizing radiation, we demonstrate a method for ultrasonic localization of wires with diameters less than the wavelength of ultrasound in the medium. Methods: Nitinol wires with diameters ranging from 50 µm to 250 µm were imaged ultrasonically in a 0.25-in-diameter water-filled tube in a gelatin medium. Imaging frequencies were 5 MHz, 7.5 MHZ, and 10 MHz. Results: For the full range of diameters traversing the phantom, the wires were localized successfully via visual inspection of both regular and difference ultrasound images. Similarly, two convolutional neural networks were trained, and both achieved an accuracy of over 95%. Conclusions: Wires with diameters as small as 50 µm were localized successfully in a water-based gelatin phantom, indicating the potential use of ultrasound to enhance endovascular navigation and surgical treatment.
ABSTRACT
The first (to our knowledge) III-V mid-IR vertical-cavity surface-emitting lasers (lambda = 2.9 microm) are demonstrated and show promising characteristics for chemical detection applications. The cw optical-pumping threshold is low (4 mW at 80 K) and efficiency is high (5.6% W/W). Pulsed operation is obtained up to 280 K and cw up to 160 K. Lateral-mode confinement will lead to spectrally pure, single-mode output for chemical identification.
