The classification of substance and behavioural addictions: A preliminary investigation

The term addiction has been used to refer to impaired control over substance use for several centuries however recently there has been a shift toward using this term in the context of non-substance use disorders, such as pathological gambling. A preliminary investigation was conducted in an attempt to clarify the most appropriate classification of 'behavioural addictions'. Participants with alcohol dependence (AD, n = 24), pathological gambling (PG, n = 20) and compulsive buying disorder (CBD, n = 14) completed an Addictive Disorder Questionnaire (ADQ); the Symptom Checklist 90 Revised (SCL-90R); Barratt Impulsivity Scale II; and substance specific adaptations of the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). Although the AD group reported more severe addiction symptoms and had higher levels of depression and anxiety, there were broad similarities across the three disorders in relation to cravings, dyscontrol, impulsivity and obsessions. Despite the small sample size and the different recruitment strategies used across the groups, the findings from this preliminary study provide support for broadening addiction diagnostic definitions to include non-substance related disorders which in turn may contribute to the development of more efficacious treatments

Contrast-Enhanced Ultrasound Imaging with Chirps: Signal Processing and Pulse Compression

Contrast-enhanced ultrasound imaging creates one of the worst case scenarios for pulse compression due to depth and frequency dependent attenuation, high level of harmonic generation, phase variations due to resonance behavior of microbubbles, and increased broadband noise by microbubble destruction. This study investigates the feasibility of pulse compression with a matched filter in the existence of microbubbles with resonant behavior. Simulations and experimental measurements showed that the scattered pressure from a microbubble population excited by a chirp waveform preserves its chirp rate even for harmonic frequencies. Although, pulse compression by a matched filter was possible due to the conservation of the chirp rate, an increase on sidelobe levels were observed at fundamental and second harmonic frequencies. Therefore, using chirp excitation and a matched filter pair will increase the contrast-to-tissue ratio with a trade-off of decreased image quality

Wideband Excitation of Microbubbles to Maximize the Sonoporation Efficiency and Contrast in Ultrasound Imaging

The importance of the excitation bandwidth is well known in diagnostic ultrasound imaging. However, the effect of excitation bandwidth in therapeutic applications of microbubbles has been mostly overlooked. A majority of contrast agent production techniques generate polydisperse microbubble populations, so a wide range of resonance frequencies exist. Therefore, wideband excitation is necessary to fully utilize microbubble resonance behavior and maximize the reradiated energy from a microbubble population, both for imaging and therapy. Oscillations of sixty SonoVue microbubbles in proximity of a rigid boundary were captured on a high speed camera at 3 Mfps, excited with a peak negative pressure of 50 kPa at 1 MHz. Measurements were analyzed according to their peak radiated pressure, radial oscillations, root mean squared pressure, and shear stress generated by microbubbles. Results showed that long duration and wideband excitation at low intensity levels was preferable for sonoporation, where microbubbles can be driven in a stable oscillation state without experiencing inertial cavitation or destruction

Commentary on the detection of bubble activity generated in ex-vivo tissue by high intensity focused ultrasound (HIFU) with respect to the generation of therapeutic lesions in tissue for the treatment of cancer

Cancer treatment by extracorporeal high intensity focused ultrasound (HIFU) is constrained by the time needed to ablate relevant tumour volumes clinically. Controlled cavitation might be used to optimise HIFU treatments, but such control requires a greater understanding of its role in lesion formation, and the provision of appropriate techniques to monitor cavitation in tissue. During HIFU exposure various forms of cavitation can occur: acoustic cavitation (both non-inertial and inertial), and bubble formation due to two thermally-driven effects (the vaporisation of liquid into vapour, and the exsolution of formerly dissolved permanent gas out of the liquid and into gas spaces). Different forms of cavitation gives rise to characteristic signals that can be monitored during HIFU. Furthermore, the character of the signal can change depending on the stage of the cavitation in question (nucleation, established cavitation, population effects etc.). Prior to undertaking experiments using tissue, studies were performed by exposing degassed water. The aim of these experiments was to test a detection system in a minimally attenuating medium known to cavitate, in order to provide data for comparison with ex-vivo tissue results.This report is written in support of the journal paper “A Study of Bubble Activity Generated in Ex-Vivo Tissue by High Intensity Focused Ultrasound (HIFU)” by the same authors (McLaughlan et al. 2010). It outlines supporting material for the discussion and conclusions contained in that paper, a study involving monitoring clinically relevant HIFU exposures in degassed water and ex-vivo bovine liver. Monitoring is accomplished using a suite of cavitation detection techniques (exploiting passive and active acoustics, audible and ultrasonic emissions and electrical drive power fluctuations). The aim of the paper is to allow informed progress towards a monitoring system specifically tailored for use during clinical HIFU treatment

Spatial Resolution and Contrast Enhancement in Photoacoustic Imaging with Filter Delay Multiply and Sum Beamforming Technique

Photoacoustic imaging is used to differentiate between tissue types based on light absorption. Different structures, such as vascular density of capillaries in human tissue, can be analysed and provide diagnostic information to detect early stage breast cancer. Delay and sum (DAS) beamforming is the traditional method to reconstruct photoacoustic images. However, for structures located deep in the tissue (>10 mm), signal to noise (SNR) of the photoacoustic signal drops significantly. This study proposes using filter delay multiply and sum (FDMAS) beamforming technique to increase the SNR and enhance the image quality. Experimental results showed that FDMAS beamformer improved the SNR by 6.9 dB and the lateral resolution by 48% compared to the DAS beamformer. Moreover, the effect of aperture size on the proposed method is presented as the sub-group FDMAS, which further increased the improvement in image quality

Elevation resolution enhancement in 3D photoacoustic imaging using FDMAS beamforming

Photoacoustic imaging is a non-invasive and non-ionizing imaging technique that combines the spectral selectivity of laser excitation with the high resolution of ultrasound imaging. It is possible to identity the vascular structure of the cancerous tissue using this imaging modality. However, elevation and lateral resolution of photoacoustic imaging is usually poor for imaging target. In this study, three dimension filter delay multiply and sum beamforming technique (FDMAS(3D)) is used to improve the resolution and enhance the signal to noise ratio (SNR) of the 3D photoacoustic image that is created by using linear array transducer. This beamforming technique showed improvement in the elevation by 36% when its compared with three dimension delay and sum beamforming technique (DAS(3D)). In addition, it enhanced the SNR by 13 dB compared with DAS (3D)

Simultaneous trapping and imaging of microbubbles at clinically relevant flow rates

Mechanisms for non-invasive target drug delivery using microbubbles and ultrasound have attracted growing interest. Microbubbles can be loaded with a therapeutic payload and tracked via ultrasound imaging to selectively release their payload at ultrasound-targeted locations. In this study, an ultrasonic trapping method is proposed for simultaneously imaging and controlling the location of microbubbles in flow by using acoustic radiation force. Targeted drug delivery methods are expected to benefit from the use of the ultrasonic trap, since trapping will increase the MB concentration at a desired location in human body. The ultrasonic trap was generated by using an ultrasound research system UARP II and a linear array transducer. The trap was designed asymmetrically to produces a weaker radiation force at the inlet of the trap to further facilitate microbubble entrance. A pulse sequence was generated that can switch between a long duration trapping waveform and short duration imaging waveform. High frame rate plane wave imaging was chosen for monitoring trapped microbubbles at 1 kHz. The working principle of the ultrasonic trap was explained and demonstrated in an ultrasound phantom by injecting SonoVue microbubbles flowing at 80 mL/min flow rate in a 3.5 mm diameter vessel

Gallium Nitride Based High-Power Switched HIFU Pulser with Real-Time Current/Voltage Monitoring

High-Intensity Focussed Ultrasound (HIFU) techniques make use of ultrasound transducers capable of delivering high powers to be delivered at high frequencies. Real-time monitoring of power delivered can avoid damage to the transducer and injury to patients due to overexposure. This paper demonstrates the real-time current and voltage monitoring capabilities of a new Gallium-Nitride (GaN) based switched mode transmit pulser developed for the University of Leeds High-Intensity Focussed Ultrasound Array Research Platform (HIFUARP) system, which uses a novel approach of using an Analog Front End (AFE) floating on the transmitter output to provide high bandwidth current measurement