Coronary angiography is routinely used to assess the extent and severity of coronary artery disease and for decision-making during percutaneous coronary interventions (PCI). However, angiography may sometimes be inadequate for deciding a treatment strategy and defining optimal stenting outcomes.  Intravascular imaging-guided PCI (intravascular ultrasound [IVUS] and optical coherence tomography [OCT]) has emerged as an effective alternative to coronary angiography-guided PCI.¹  Both IVUS and OCT are analogous in that they send out energy waves (OCT uses light and IVUS uses sound waves) into the vessel wall and the energy that is sent back to the catheter is used to reconstruct an image.^2,3 However, each technique has its own advantages and limitations.

Intravascular ultrasound has been established as a reliable imaging tool to guide stenting of complex lesions, including coverage of ostial lesions, bifurcation lesions, left main stenting, and chronic total occlusions. Further, it is useful in determining the cause of stent failures, including in-stent restenosis. IVUS examinations have also significantly increased our understanding of the mechanisms of balloon angioplasty, stent implantation, and restenosis.⁴ A major advantage of IVUS over OCT is its penetration of 4-8 mm inside the vessel wall. The light-based OCT technology can only penetrate about 2-3 mm. If a vessel has significantly remodelled due to plaque burden, the outline of the true lumen disappears on the OCT image and it may be difficult for the interventionalist to assess the extent of the plaque.³ Despite its benefits, the use of IVUS has been noted to be limited to <20% of percutaneous coronary intervention (PCI) procedures.⁴

On the other hand, OCT has greater spatial resolution than IVUS^2,5,6 and studies have shown that it provides more details regarding the microstructure of the vessel wall than IVUS.^2,7 Specifically, OCT has been shown to identify thin-cap fibroatheroma (TCFA), a feature that may not be possibly detected with precision by IVUS.^8-11 Further, intimal hyperplasia, internal and external elastic laminae, echolucent regions corresponding to large lipid pools, tissue protrusion, edge dissection, and incomplete stent apposition may be more frequently identified by OCT- versus IVUS-imaging.^8,12,13  

Considering the benefits of IVUS and OCT over angiography, and the individual limitations and advantages of IVUS and OCT, it may be important to understand the comparative reliability of each of these techniques for coronary measurements and treatment decision-making and assess interindividual variability, if any of the coronary measurements by these methods.

1. Buccheri S, Franchina G, Romano S, et al. Clinical outcomes following intravascular imaging-guided versus coronary angiography-guided percutaneous coronary intervention with stent implantation: A systematic review and Bayesian network meta-analysis of 31 studies and 17,882 patients. JACC Cardiovasc Interv. 2017;10(24):2488-2498.

2. Prati F, Regar E, Mintz GS, et al. Expert review document on methodology, terminology, and clinical applications of opticalcoherence tomography: Physical principles, methodology of image acquisition, and clinicalapplication for assessment of coronary arteries and atherosclerosis. Eur Heart J. 2010;31(4):401-15.

3. Fornell D. The advantages and disadvantages of OCT vs. IVUS.  DAC, 2011. Available at: https://www.dicardiology.com/article/advantages-and-disadvantages-oct-vs-ivus. Accessed on: 22 Sep 2019

4. Waksman R, Kitabata H, Prati F, et al. Intravascular ultrasound versus optical coherence tomography guidance. J Am Coll Cardiol. 2013; 62 (17): Suppl S

5. Mintz GS, Nissen SE, Anderson WD, et al. American College of Cardiology Clinical Expert Consensus Document on Standards for Acquisition, Measurement and Reporting of Intravascular Ultrasound Studies (IVUS). A report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents. J Am Coll Cardiol. 2001;37:1478–92. 

6. Garcìa-Garcìa HM, Gogas BD, Serruys PW, et al. IVUS-based imaging modalities for tissue characterization: similarities and differences. Int J Cardiovasc Imaging. 2011;27:215–224.  

7. Prati F, Guagliumi G, Mintz GS, et al. Expert review document part 2: Methodology, terminology and clinical applications of optical coherence tomography for the assessment of interventional procedures. Eur Heart J. 2012;33(20):2513-20.

8. Jang IK, Bouma BE, Kang DH et al. Visualization of coronary atherosclerotic plaques in patients using optical coherence tomography: Comparison with intravascular ultrasound. J Am Coll Cardiol. 2002;39:604–609. 

9. Jang IK, Tearney GJ, MacNeill B et al. In vivo characterization of coronary atherosclerotic plaque by use of optical coherence tomography. Circulation. 2005;111:1551–5.

10. Tanaka A, Imanishi T, Kitabata H, et al. Lipid-rich plaque and myocardial perfusion after successful stenting in patients with non-ST-segment elevation acute coronary syndrome: an optical coherence tomography study. Eur Heart J. 2009;30:1348–55.

11. Rathod KS, et al. Intravascular ultrasound versus optical coherence tomography for coronary artery imaging – Apples and oranges? International Cardiol Rev. 2015;10(1):8-15.

12. Kim IC, Yoon HJ, Shin ES, et al. Usefulness of frequency domain optical coherence tomography compared with intravascular ultrasound as a guidance for percutaneous coronary intervention. J Interv Cardiol. 2016;29(2):216-24.

13. Maehara A, Ben-Yehuda O, Ali Z, et al Comparison of stent expansion guided by optical coherence tomography versus intravascular ultrasound: The ILUMIEN II study (Observational Study of Optical Coherence Tomography [OCT] in Patients Undergoing Fractional Flow Reserve [FFR] and Percutaneous Coronary Intervention). JACC Cardiovasc Interv. 2015;8(13):1704-14. 

14. Kubo T, Akasaka T, Shite J, et al. OCT compared with IVUS in a coronary lesion assessment: the OPUS-CLASS study. JACC Cardiovasc Imaging. 2013;6(10):1095-1104