Handheld ultrahigh speed swept source optical coherence tomography instrument using a MEMS scanning mirror

Abstract

Abstract:We developed an ultrahigh speed, handheld swept source optical coherence tomography (SS-OCT) ophthalmic instrument using a 2D MEMS mirror. A vertical cavity surface-emitting laser (VCSEL) operating at 1060 nm center wavelength yielded a 350 kHz axial scan rate and 10 µm axial resolution in tissue. The long coherence length of the VCSEL enabled a 3.08 mm imaging range with minimal sensitivity roll-off in tissue. Two different designs with identical optical components were tested to evaluate handheld OCT ergonomics. An iris camera aided in alignment of the OCT beam through the pupil and a manual fixation light selected the imaging region on the retina. Volumetric and high definition scans were obtained from 5 undilated normal subjects. Volumetric OCT data was acquired by scanning the 2.4 mm diameter 2D MEMS mirror sinusoidally in the fast direction and linearly in the orthogonal slow direction. A second volumetric sinusoidal scan was obtained in the orthogonal direction and the two volumes were processed with a software algorithm to generate a merged motion-corrected volume. Motion-corrected standard 6 x 6 mm 2 and wide field 10 x 10 mm 2 volumetric OCT data were generated using two volumetric scans, each obtained in 1.4 seconds. High definition 10 mm and 6 mm B-scans were obtained by averaging and registering 25 B-scans obtained over the same position in 0.57 seconds. One of the advantages of volumetric OCT data is the generation of en face OCT images with arbitrary cross sectional B-scans registered to fundus features. This technology should enable screening applications to identify early retinal disease, before irreversible vision impairment or loss occurs. Handheld OCT technology also promises to enable applications in a wide range of settings outside of the traditional ophthalmology or optometry clinics including pediatrics, intraoperative, primary care, developing countries, and military medicine.

Review of intraoperative optical coherence tomography: technology and applications [Invited]

“…Galvanometer scanning mirrors were subsequently incorporated into HHOCT and allowed greater speed and flexibility for optical scanning at the cost of increased size and weight of the probe [67]. More recently, the introduction of microelectromechanical (MEMS) devices as compact optical scanners [74,75] to replace galvanometer scanners has resulted in smaller and lighter HHOCT probes [76][77][78]. In general, however, mirror-based optical scanning probes are larger in size and more suitable for non-invasive surgical imaging (Section 2.1), while fiber-based scanning probes can be made compact enough to be integrated into surgical needles (Section 2.2) and instruments (Section 2.3).…”

“…1(b)). A key feature demonstrated in [91] was the incorporation of MEMS scanner [74,75], which had been previously employed in catheter-based OCT systems [92,93] and other HHOCT probes for non-intraoperative use [76][77][78]. The intraoperative HHOCT probe's size was significantly decreased by using the MEMS scanner, and the probe's functionality was tested during anastomosis performed in vivo in a mouse surgical model [91].…”

FDOCT imaging processor for portable OCT systems with high imaging rate

“…However, the recent trend has been toward small-scale apparatus for mobile medical applications. This has led to the development of microelectromechanical systems (MEMS) [7] and the photonic-integrated circuit (PIC) [8] technology for the FDOCT opticalmechanical front end. Thus, an FDOCT imaging scheme based on an area-and energy-efficient processor, such as field programmable gate array (FPGA) or application-specific integrated circuit (ASIC), could be of considerable practical value in the development of small-scale handheld FDOCT devices.…”

Handheld optical coherence tomography angiography

“…In 2013, Lu et al used swept source (SS) OCT technique and MEMS to build handheld OCT probes. Wide-field en face images (10 × 10 mm 2 ) of the human retina were retrieved from the handheld OCT instrument [15]. Besides, a series of research works on the development of handheld scanning laser ophthalmoscopy (SLO) and OCT probe have demonstrated by researchers at Duke University [16,17].…”