MHz Swept-Source OCT for clinical applications

Abstract

Purpose : While research OCT systems with MHz A-scan rates have been presented in the past, the clinical value of such high acquisition rates is still poorly understood. Clinical studies with significant sample sizes have so far been difficult due to the complexity of such high-speed systems. We present a versatile, easy to operate clinical prototype, capable of A-scan rates up to 1.7MHz and suitable for anterior as well as posterior segment imaging with different fields of view (FOV) and spatial resolutions.

Methods : We developed a clinical 1060nm SS-OCT prototype capable of acquiring 1.7 million A-scans per second (8.5x faster than the fastest commercial OCT system) over a depth range in tissue of up to 6mm and an axial resolution of 9μm in tissue. The lateral resolution can be doubled by a beam expander at the click of a button. We designed two magnetically attachable add-on lenses to expand the FOV on the retina to up to 90 degree and to enable telecentric scanning of the anterior segment. To ensure the prototype can be operated independently by clinical staff, we added alignment aids such as a fundus view, an iris view, a motorized chin rest, reference delay and polarization control.

Results : Fig. 1a shows the enface projection of a 90deg OCT scan, a FOV comparable to that of state of the art wide field fundus cameras. A 90deg B-scan can be seen in Fig. 1b. A volume rendering of a full anterior segment is shown in Fig. 1c. In Fig. 2 we present the prototype’s wide field and microscopic OCTA capabilities. A 12mm x 12mm scan acquired within only 2.5s is shown in Fig. 2a. A 65deg FOV OCTA scan can be seen in Fig. 2b, where the blue magnification box highlights that despite the large FOV, the avascular zone can still be resolved. Fig. 2c shows OCTA acquisitions of the choriocapillaris with enhanced lateral resolution. While individual capillaries are even resolved in the 12mm x 12mm scan, the denser sampled overlaid scan in the blue box shows that contrast can still significantly improved by increasing the sampling density.

Conclusions : The versatility and ease of use of the presented prototype will enable a thorough investigation of the clinical value of MHz A-scan rates through several clinical studies.

This is a 2020 ARVO Annual Meeting abstract.

 

Fig 1. a) 90deg retina OCT enface image, b) 90deg OCT retina B-scan, c) Volume rendering of an anterior segment scan

 

Fig. 2. a) 12mm x 12mm retina OCTA scan, b) 65deg retina OCTA scan, c) 12mm x 12mm choriocapillaris OCTA scan