All-Optical Rotational Ultrasound Imaging.

Miniaturised high-resolution imaging devices are valuable for guiding minimally invasive procedures such as vascular stent placements. Here, we present all-optical rotational B-mode pulse-echo ultrasound imaging. With this device, ultrasound transmission and reception are performed with light. The all-optical transducer in the probe comprised an optical fibre that delivered pulsed excitation light to an optical head at the distal end with a multi-walled carbon nanotube and polydimethylsiloxane composite coating. This coating was photoacoustically excited to generate a highly directional ultrasound beam perpendicular to the optical fibre axis. A concave Fabry-Pérot cavity at the distal end of an optical fibre, which was interrogated with a tuneable continuous-wave laser, served as an omnidirectional ultrasound receiver. The transmitted ultrasound had a -6 dB bandwidth of 31.3 MHz and a peak-to-peak pressure of 1.87 MPa, as measured at 1.5 mm from the probe. The receiver had a noise equivalent pressure <100 Pa over a 20 MHz bandwidth. With a maximum outer probe diameter of 1.25 mm, the probe provided imaging with an axial resolution better than 50 µm, and a real-time imaging rate of 5 frames per second. To investigate the capabilities of the probe, intraluminal imaging was performed in healthy swine carotid arteries. The results demonstrate that the all-optical probe is viable for clinical rotational ultrasound imaging.

All-optical dual photoacoustic and optical coherence tomography intravascular probe.

Intravascular imaging in percutaneous coronary interventions can be an invaluable tool in the treatment of coronary artery disease. It is of significant interest to provide molecular imaging contrast that is complementary to structural contrast provided by optical coherence tomography (OCT) and intravascular ultrasound imaging (IVUS). In this study, we developed a dual-modality intravascular imaging probe comprising a commercial OCT catheter and a high sensitivity fiber optic ultrasound sensor, to provide both photoacoustic (PA) and OCT imaging. With PA imaging, the lateral resolution varied from 18 µm to 40 µm; the axial resolution was consistently in the vicinity of 45 µm. We demonstrated the clinical potential of the probe with 2-D circumferential PA and OCT imaging, and with multispectral PA imaging.

Optical coherence tomography evaluation of pulmonary arterial vasculopathy in Systemic Sclerosis.

Our current understanding of the pathophysiology of pulmonary vascular disease is incomplete, since information about alterations of the pulmonary vasculature in pulmonary arterial hypertension (PAH) is primarily provided by autopsy or tissue specimens. The aim of this study was to compare the distal pulmonary vasculature of <2 mm in diameter in Systemic Sclerosis (SSc) patients with (n = 17) and without (n = 5) associated PAH using Optical Coherence Tomography during Right Heart catheterization. SSc-PAH patients showed significant thickening of Intima Media Thickening Area compared to patients without PAH (27 +/- 5.8% vs. 21 +/- 1.4%, p = 0.024). A good haemodynamic response to previous targeted PAH treatment was associated with a significantly greater number of small pulmonary artery side branches <300 µm per cm vessel (3.8 +/- 1.1 vs. 1.8 +/- 1.1; p = 0.010) and not associated with Intima Media thickening Area (26 +/- 5.4% vs. 28 +/- 6.7%; p = 0.6). Unexpected evidence of pulmonary artery thrombus formation was found in 19% of SSc-PAH patients. This is the first in-vivo study demonstrating a direct link between a structural abnormality of pulmonary arteries and a response to targeted treatment in PAH. Intravascular imaging may identify subgroups that may benefit from anticoagulation.