Experimental evaluation of photoacoustic coded excitation using unipolar golay codes.

Q-switched Nd:YAG lasers are commonly used as light sources for photoacoustic imaging. However, laser diodes are attractive as an alternative to Nd:YAG lasers because they are less expensive and more compact. Although laser diodes deliver about three orders of magnitude less light pulse energy than Nd:YAG lasers (tens of microjoules compared with tens of millijoules), their pulse repetition frequency (PRF) is four to five orders of magnitude higher (up to 1 MHz compared with tens of hertz); this enables the use of averaging to improve SNR without compromising the image acquisition rate.

Transcranial sound field characterization.

In the scope of therapeutic ultrasound applications in the adult brain, such as sonothrombolysis in stroke, a better understanding of the intracranial acoustic properties during insonation through the temporal bone is warranted. Innovative ultrasound imaging techniques, like transcranial duplex sonography, may open new avenues to apply ultrasound for therapeutic purposes and to visually monitor the effect using the same device. The aim was to study the transcranial sound field aberrations and the changes of acoustic parameters, using a high-end duplex machine.

Intraoperative ultrasound using phase inversion harmonic imaging: first experiences.

Objective: To study the feasibility of intraoperative ultrasound using the phase inversion harmonic imaging (PIHI) technique.

Methods: Eight patients with intracranial middle cerebral artery aneurysms and five patients with arteriovenous malformations were studied after written informed consent. A first ultrasound study was performed through the intact dura mater after cranial trepanation to assess the pathology, its feeding artery, and downstream segments.

Intraoperative brain ultrasound: a new approach to study flow dynamics in intracranial aneurysms.

The aim was to evaluate the potential of contrast-enhanced ultrasound to visualize the hemodynamics in intracranial aneurysms during neurosurgical intervention and to quantify the ultrasound data using digital particle image velocimetry (DPIV) technique. Aneurysms were scanned through the intact dura mater, preclipping and again postclipping after closure of the dura. After intravenous injection of Optison, angio-like views of the vascular tree surrounding the aneurysm, including the aneurysm sac, were obtained.

Transcranial ultrasound angiography (T USA): a new approach for contrast specific imaging of intracranial arteries.

The goal was to develop an ultrasound contrast agent-specific imaging mode that offers an angiography-like view of the intracranial arteries and enables lower mechanical index MI settings compared to conventional transcranial duplex sonography. We studied 12 patients with transcranial ultrasound angiography (t USA) via the temporal bone window after an IV bolus injection of a perfluorocarbon-based microbubble contrast agent (Imagent). The aim was to display the intracranial vessel segments of the middle cerebral artery (M1, M2 and M3), the anterior cerebral artery (A1 and A2), the posterior cerebral artery (P1, P2 and P3) and the internal carotid artery (C1/2 and C3/4).