Automated non-rigid registration and mosaicing for robust imaging of distinct retinal capillary beds using speckle variance optical coherence tomography

201

124

Abstract:We analyze the benefits and problems of in vivo optical coherence tomography (OCT) imaging of the human retina at A-scan rates in excess of 1 MHz, using a 1050 nm Fourier-domain mode-locked (FDML) laser. Different scanning strategies enabled by MHz OCT line rates are investigated, and a simple multi-volume data processing approach is presented. In-vivo OCT of the human ocular fundus is performed at different axial scan rates of up to 6.7 MHz. High quality non-mydriatic retinal imaging over an ultra-wide field is achieved by a combination of several key improvements compared to previous setups. For the FDML laser, long coherence lengths and 72 nm wavelength tuning range are achieved using a chirped fiber Bragg grating in a laser cavity at 419.1 kHz fundamental tuning rate. Very large data sets can be acquired with sustained data transfer from the data acquisition card to host computer memory, enabling high-quality averaging of many frames and of multiple aligned data sets. Three imaging modes are investigated: Alignment and averaging of 24 data sets at 1.68 MHz axial line rate, ultra-dense transverse sampling at 3.35 MHz line rate, and dual-beam imaging with two laser spots on the retina at an effective line rate of 6.7 MHz. 58. R. Huber, D. C. Adler, V. J. Srinivasan, and J. G. Fujimoto, "Fourier domain mode locking at 1050 nm for ultrahigh-speed optical coherence tomography of the human retina at 236,000 axial scans per second," Opt. Lett. ©2013 Optical Society of America

Section: The Simple "Acquire-align-average" (Aaa) Processing Approachmentioning

confidence: 99%

Multi-MHz retinal OCT

Klein

Wieser

Reznicek

et al. 2013

201

124

“…A Gabor filter was used to segment vessel-like features [28]. Briefly, a Gabor filter is a cosinusoidal modulated Gaussian, which acts as a directional low-pass filter.…”

Section: Image Quantificationmentioning

confidence: 99%

In vivo hyperspectral imaging of microvessel response to trastuzumab treatment in breast cancer xenografts

McCormack¹,

Walsh²,

Sit³

et al. 2014

HER2-amplified (HER2 + ) breast cancers are treated with the anti-HER2 monoclonal antibody trastuzumab. Although trastuzumab reduces production of the angiogenic factor VEGF in HER2 + tumors, the acute and sustained effects of trastuzumab on the tumor vasculature are not understood fully, particularly in trastuzumab-resistant tumors. We used mouse models of trastuzumab sensitive and trastuzumab-resistant HER2 + breast cancers to measure dynamic changes in tumor microvessel density and hemoglobin oxygenation (sO 2 ) in vivo using quantitative hyperspectral imaging at 2, 5, 9, and 14 days after antibody treatment. Further analysis quantified the distribution of microvessels into low and high oxygenation groups, and monitored changes in these distributions with trastuzumab treatment. Gold standard immunohistochemistry was performed to validate complementary markers of tumor cell and vascular response to treatment. Trastuzumab treatment in both responsive and resistant tumors resulted in decreased sO 2 5 days after initial treatment when compared to IgG-treated controls (p<0.05). Importantly, responsive tumors showed significantly higher vessel density and significantly lower sO 2 than all other groups at 5 days post-treatment (p<0.05). Distribution analysis of vessel sO 2 showed a significant (p<0.05) shift of highly oxygenated vessels towards lower oxygenation over the time-course in both trastuzumab-treated responsive and resistant tumors. This study suggests that longitudinal hyperspectral imaging of microvessel sO 2 and density could distinguish trastuzumabresponsive from trastuzumab-resistant tumors, a finding that could be exploited in the post-neoadjuvant setting to guide post-surgical treatment decisions. Udove, A. Ullrich, and et, "Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer," Science 244(4905), 707-712 (1989). 3. J. S. Ross and J. A. Fletcher, "The HER-2/neu oncogene in breast cancer: prognostic factor, predictive factor, and target for therapy," Stem Cells 16(6), 413-428 (1998) ©2014 Optical Society of America

“…On en face angiograms, the projection artifact causes superficial vascular networks to be duplicated on deeper slabs. One clinical problem caused by this artifact is the duplication of normal inner retinal vascular pattern onto the outer retinal slab, which clutters the deeper slab and interferes with the detection and measurement of choroidal neovascularization (CNV) [9,[12][13][14][15][16][17]. Since CNV is the most serious complication of age-related neovascularization (AMD), the leading cause of blindness in the US [18][19][20], the flow projection artifact is a problem of great clinical significance.…”

Section: Introductionmentioning

confidence: 99%

Projection-resolved optical coherence tomographic angiography

Zhang

Hwang

Campbell

et al. 2016

301

265

Shadowgraphic projection artifacts from superficial vasculature interfere with the visualization of deeper vascular networks in optical coherence tomography angiography (OCT-A). We developed a novel algorithm to remove this artifact by resolving the ambiguity between in situ and projected flow signals. The algorithm identifies voxels with in situ flow as those where intensity-normalized decorrelation values are higher than all shallower voxels in the same axial scan line. This "projection-resolved" (PR) algorithm effectively suppressed the projection artifact on both en face and cross-sectional angiograms and enhanced depth resolution of vascular networks. In the human macula, the enhanced angiograms show three distinct vascular plexuses in the inner retina and no vessels in the outer retina. We demonstrate that PR OCT-A cleanly removes flow projection from the normally avascular outer retinal slab while preserving the density and continuity of the intermediate and deep retinal capillary plexuses.