Applications of optical coherence tomography in cardiovascular medicine, Part 2

Optical coherence contrast imaging using gold nanorods in living mice eyes

BACKGROUND

Optical coherence tomography (OCT) is a powerful imaging modality to visualize tissue structures, with axial image pixel resolution as high as 1.6 μm in tissue. However, OCT is intrinsically limited to providing structural information as the OCT contrast is produced by optically scattering tissues.

METHODS

Gold nanorods (GNRs) were injected into the anterior chamber (AC) and cornea of mice eyes which could create a significant OCT signal and hence could be used as a contrast agent for in vivo OCT imaging.

RESULTS

A dose of 30 nM of GNRs (13 nm in diameter and 45 nm in length) were injected to the AC of mice eyes and produced an OCT contrast nearly 50-fold higher than control mice injected with saline. Furthermore, the lowest detectable concentration of GNRs in living mice AC was experimentally estimated to be as low as 120 pM.

CONCLUSIONS

The high sensitivity and low toxicity of GNRs brings great promise for OCT to uniquely become a high-resolution molecular imaging modality.

High-resolution coronary imaging by optical coherence tomography: Feasibility, pitfalls and artefact analysis

BACKGROUND

Optical coherence tomography is an imaging method that enables cardiologists to study atheromatous plaques, and to check the implantation and evolution of coronary stents. It is an invasive technique, providing high-resolution (10 microm) in vivo images, but with limitations and artefacts that need to be understood before the field of application can be extended.

AIM

To determine the feasibility and limitations of optical coherence tomography coronary imaging from a single-centre experience.

METHODS

We analysed the first 301 optical coherence tomography (version M2, LightLab Imaging) sequences obtained in our department from examination of 73 patients.

RESULTS

Results showed that 92% of sequences for selected lesions were usable, with a mean examination time of 17 min. Only one complication occurred (ventricular fibrillation, reduced by external electroshock). In our registry, sequence quality depended on operator experience (improving after 20 examinations), and was impaired by artefacts, especially in right coronary analysis and in arteries of greater than 3.5 mm calibre.

CONCLUSIONS

Proximal coronary occlusion and the distal flush quality currently required for quality imaging should no longer be indispensable with the new generation of optical coherence tomography systems.

Effect of glitazones on the progression of coronary artery disease in type 2 diabetes patients

The effect of thiazolidinediones (TZDs) on the progression of atherosclerosis in diabetes patients remains unclear. There has been heightened interest in recent years in this class of diabetes medications due to the non-glycemic lowering effects, such as altering lipids, inflammation and hematologic profiles. There have been several exciting studies over the past few years focused on the mechanism of action of the TZDs with respect to alteration in the cardio-metabolic profile in diabetes patients. New tools such as intravascular ultrasound have been used to follow plaques characteristics over time on a much more sensitive scale than has ever been possible in the past by coronary angiograms. These advances have enabled researchers to follow closely the macrovascular effects of different anti-atherosclerotic medications such as statins and TZDs. This article reviews the pathophysiology of atherosclerosis in diabetes, the role that TZDs play in this process and the imaging trials looking at the progression or regression of atherosclerosis in patients treated with TZDs.