Simultaneous Bilateral Real-Time 3-D Transcranial Ultrasound Imaging at 1 MHz Through Poor Acoustic Windows

Abstract

Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%–29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging—the ultrasound brain helmet—and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field.

Experimental demonstration of passive acoustic imaging in the human skull cavity using CT‐based aberration corrections

“…68 Because of this, transcranial sonography is typically achieved through "acoustic windows" in the skull, regions where the bone thickness is minimal and fairly uniform, such as the temporal and suboccipital windows. [69][70][71][72] One approach to utilizing passive imaging in the brain could be to image through these windows using a narrowaperture array. 64,65 However, due to the superior resolution afforded by large apertures while employing passive imaging techniques, 48 an implementation with an array covering the entire skull surface would be optimal.…”

3-D Transcranial Ultrasound Imaging with Bilateral Phase Aberration Correction of Multiple Isoplanatic Patches: A Pilot Human Study with Microbubble Contrast Enhancement

“…5, 6, 7), though some dropout remains. While the presence of this dropout of the Doppler signal in some of the presented images indicates that this goal has not yet been achieved, the aberration correction improvement presented here (~2–3 dB) might be combined with our earlier efforts at improving sensitivity by reducing cable lengths (~7 dB) (Lindsey et al 2011) and reducing transducer frequency (~3–8 dB, patient-dependent) (Lindsey et al 2013). …”

“…One subject exhibited a window failure, present in 8–29% of the population (Hashimoto et al 1992; Seidel et al 1995; Baumgartner et al 1997; Marinoni et al 1997; Postert et al 1997; Gahn et al 2000; Krejza et al 2007; Lindsey et al 2013). In this subject, no landmarks were visible on the B-mode echo image and only noise was visible with microbubble contrast enhancement but without aberration correction (Fig.…”

“…In order to display 3D data, simultaneously acquired volumes were averaged in time and registered and fused into a single 3D visualization as described previously (Lindsey et al 2011; Lindsey et al 2013). Video recordings of the real-time display were reviewed by an author experienced (B.L.)…”

Transcranial activation and imaging of low boiling point phase‐change contrast agents through the temporal bone using an ultrafast interframe activation ultrasound sequence

“…1,2 In stroke and cerebrovascular disease, ultrasound has demonstrated the ability to image major cerebral vasculature (i.e., Circle of Willis, middle cerebral arteries). [3][4][5][6][7][8] In addition, ultrasound has been demonstrated to have therapeutic effects in ischemic stroke. 9 In cases of ICH and large clots, researchers have recently demonstrated encouraging results through the use of high intensity, short ultrasound pulses to dissolve clots.…”