Physical Principles and Equipment of Intravascular Optical Coherence Tomography
Optical coherence tomography (OCT) is an emerging imaging modality analogous to intravascular ultrasound imaging but uses light instead of sound. The integration of a fiber-optic probe with frequency domain OCT enables video images that display the locati
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Jinyong Ha
Optical coherence tomography (OCT) is an emerging imaging modality analogous to intravascular ultrasound imaging but uses light instead of sound. The integration of a fiber-optic probe with frequency domain OCT enables video images that display the location and changes of coronary plaques and stent apposition in live patients. This chapter details the basic principles of intravascular optical coherence tomography (IV-OCT) in clinical practice. The system architecture and catheter structure consisting of an optical probe and a protective sheath are discussed in detail. Also, recent technology advances in IV-OCT are briefly introduced.
filling a gap between microscopy and ultrasound in comparison with resolution and imaging depth as shown in Fig. 10.1 [5]. Microscopy performs very high-resolution (~1 μm) imaging of en face tissue plane, but imaging depth in biological tissues is limited up to only a few hundred micrometers due to the signal attenuation from large optical scattering. The resolution of medical ultrasound imaging varies 0.1–1 mm depending on the sound wave frequency. It is, however, possible to see internal organs even if the imaging depth is limited to only millimeter ranges at high frequencies of ultrasound waves [6]. Compared with ultrasound imaging, OCT has the same operation principle, echo signal detection, but utilizes infrared light instead of 10.1 Introduction to OCT ultrasound. In general, imaging is performed by measuring the magnitude and time delay of Optical coherence tomography (OCT) is a high- backscattered or backreflected signal from interresolution imaging modality that provides real- nal biological tissues. As a sound wave travels time cross-sectional images of tissue at 340 m/s in air, the echo signal can be meamicrostructures using the near-infrared light [1]. sured with a time resolution of ~100 ns, which As OCT has common features with ultrasound is within the limits of the electronic detection imaging and microscopy in medical applications, process. However, it is impossible to electrically it has been clinically adopted in ophthalmology, measure echoes of backscattered light due to dermatology, and cardiology [2–4]. In most tis- the light speed of 3 × 108 m/s in air, and optical sues, OCT imaging plays an important role in interferometric techniques were then proposed [7–9]. Optical interferometers are widely used in science and engineering to measure small displacements and spatial irregularities by measurJ. Ha ing interference patterns. To achieve microscale Department of Optical Engineering, Sejong resolutions of the optical sectioning ability, University, Seoul, South Korea low- coherence interferometry, using the short e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2018 M.-K. Hong (ed.), Coronary Imaging and Physiology, https://doi.org/10.1007/978-981-10-2787-1_10
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J. Ha
98 Resolution (log) 1 mm Standard clinical ultrasound (Res: 0.1-1 mm @3~40 MHz) 100 µm High frequency Ultrasound (Res: 15-20 µm, Depth: a few mm @ ~100 MHz) 10 µ
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