Note: This is a virtual presentation. Here is the link for where the presentation will be taking place.
Title: Optical coherence tomography (OCT) – guided ophthalmic therapy
Abstract: Optical coherence tomography (OCT), which provides cross-sectional images noninvasively with a micro-scale in real-time, has been widely applied for the diagnosis and treatment guidance for various ocular diseases.
In the first part of this work, we develop a hand-held subretinal-injector actively guided by a common-path OCT (CP-OCT) distal sensor. Subretinal injection is becoming increasingly prevalent in both scientific research and clinical communities as an efficient way of treating retinal diseases. It delivers drug or stem cells in the space between RPE and photoreceptor layers and, thus, directly affect resident cell and tissues in the subretinal space. However, the technique requires high stability and dexterity of surgeon due to fine anatomy of the retina, and it is challenging because of physiological motions of surgeons like hand tremor. We mainly focus on two aspects of the CP-OCT guided subretinal-injector: (i) A high-performance fiber probe based on high-index epoxy lensed-fiber to enhance the CP-OCT retinal image quality; (ii) Automated layer identification and tracking: Each retinal layer boundary, as well as retinal surface, is tracked using 1D convolutional neural network (CNN)-based segmentation on A-scans for accurate localization of a needle. The CNN model is integrated into the CP-OCT system for real-time target boundary distance sensing, and unwanted axial motions are compensated based on the target boundary tracking. The CP-OCT distal sensor guided system is tested on ex vivo bovine retina and achieves micro-scale depth targeting accuracy, showing its promising possibility for clinical application.
In the second part, we propose and demonstrate selective retina therapy (SRT) monitoring and temperature estimation based on speckle variance OCT (svOCT) for dosimetry control. SRT is an effective laser treatment method for retinal diseases associated with a degradation of the retinal pigment epithelium (RPE). The SRT selectively targets the RPE, so it reduces negative side effects and facilitates healing of the induced retinal lesions. However, the selection of proper laser energy is challenging because of ophthalmoscopically invisible lesions in the RPE and variance in melanin concentration between patients and even between regions within an eye. SvOCT quantifies speckle pattern variation caused by moving particles or structural changes in biological tissues. SvOCT images were calculated as interframe intensity variance of the sequence, and they show abrupt speckle variance change induced by laser pulse irradiation. We find that svOCT peak values have a reliable correlation with the degree of retinal lesion formation. The temperature at the neural retina and RPE is estimated from the svOCT peak values using numerically calculated temperature, which is consistent with the observed lesion creation.
Jin U. Kang, Department of Electrical and Computer Engineering
Israel Gannot, Department of Electrical and Computer Engineering
Mark Foster, Department of Electrical and Computer Engineering