Total flow intensity, active flow intensity and volume related flow intensity as new quantitative metrics in optical coherence tomography angiography

High-resolution/High-Speed Gap Can Distinguish Different Intraretinal Perfusion Signals by Optical Coherence Tomography Angiography

Purpose

The development of optical coherence tomography angiography (OCTA) has radically changed the diagnostic assessment of the intraretinal vascular network. Two different OCTA acquisition modalities have recently been introduced in clinical practice, namely high-resolution (HR) and high-speed (HS) scans. HR OCTA requires more acquisition time and provides higher quality data, whereas HS OCTA is faster but furnishes lower quality data. The main aim of the present study is to gauge how much extra blood flow perfusion information can be obtained through the combined use of HR and HS OCTA.

Methods

We compared HR and HS OCTA acquisitions to assess the reliability of both techniques, also putting forward a new set of quantitative metrics to measure the HR/HS OCTA gap and to highlight different perfusion information.

Results

In essence, both HR and HS OCTA acquisitions proved highly feasible in detecting the intraretinal vascular flow signal, as confirmed by the stability of quantitative OCTA metrics, thus displaying their suitability for use in clinical practice. We detected an HR/HS overlapping gap of 21.6 ± 6.5% for intraretinal capillaries, and 4.3 ± 1.2% for choriocapillaris, highlighting the greater information obtained by HR OCTA.

Conclusions

This novel HR/HS OCTA gap assessment might pave the way for the development of new quantitative metrics for retinal diseases that would focus on the earlier detection of perfusion impairment and relate it to the stage of the disease and its progression.

Translational Relevance

This study proposes a new quantitative way to detect different perfusion signals based on OCTA. The findings presented in this paper can lay the foundations for the development of new quantitative metrics focused on the separate analysis of high flow and low flow signals, enabling very early changes in intraretinal perfusion to be detected.

Quantitative approaches in multimodal fundus imaging: State of the art and future perspectives

When it first appeared, multimodal fundus imaging revolutionized the diagnostic workup and provided extremely useful new insights into the pathogenesis of fundus diseases. The recent addition of quantitative approaches has further expanded the amount of information that can be obtained. In spite of the growing interest in advanced quantitative metrics, the scientific community has not reached a stable consensus on repeatable, standardized quantitative techniques to process and analyze the images. Furthermore, imaging artifacts may considerably affect the processing and interpretation of quantitative data, potentially affecting their reliability. The aim of this survey is to provide a comprehensive summary of the main multimodal imaging techniques, covering their limitations as well as their strengths. We also offer a thorough analysis of current quantitative imaging metrics, looking into their technical features, limitations, and interpretation. In addition, we describe the main imaging artifacts and their potential impact on imaging quality and reliability. The prospect of increasing reliance on artificial intelligence-based analyses suggests there is a need to develop more sophisticated quantitative metrics and to improve imaging technologies, incorporating clear, standardized, post-processing procedures. These measures are becoming urgent if these analyses are to cross the threshold from a research context to real-life clinical practice.

The Development and Clinical Application of Innovative Optical Ophthalmic Imaging Techniques

The field of ophthalmic imaging has grown substantially over the last years. Massive improvements in image processing and computer hardware have allowed the emergence of multiple imaging techniques of the eye that can transform patient care. The purpose of this review is to describe the most recent advances in eye imaging and explain how new technologies and imaging methods can be utilized in a clinical setting. The introduction of optical coherence tomography (OCT) was a revolution in eye imaging and has since become the standard of care for a plethora of conditions. Its most recent iterations, OCT angiography, and visible light OCT, as well as imaging modalities, such as fluorescent lifetime imaging ophthalmoscopy, would allow a more thorough evaluation of patients and provide additional information on disease processes. Toward that goal, the application of adaptive optics (AO) and full-field scanning to a variety of eye imaging techniques has further allowed the histologic study of single cells in the retina and anterior segment. Toward the goal of remote eye care and more accessible eye imaging, methods such as handheld OCT devices and imaging through smartphones, have emerged. Finally, incorporating artificial intelligence (AI) in eye images has the potential to become a new milestone for eye imaging while also contributing in social aspects of eye care.