Ragnar Olafsson

Emotion regulation in pathological skin picking: findings from a non-treatment seeking sample.

Pathological skin picking (PSP) is characterized by excessive picking of the skin, resulting in significant distress or functional impairment. The aim of the present study was to investigate the emotion regulation hypothesis of PSP. University students with PSP (n = 55) and without history of PSP (n = 55) were asked to retrospectively rate the intensity of affective states before, during, and after skin picking episodes. The results showed that for a majority of the PSP sufferers, intensity of certain negative affective states (i.e. anxiety, tension or boredom) was pronounced just before picking, and diminished significantly in the period from before to after picking. Relief and gratification increased during picking whereas guilt increased afterwards. A similar pattern emerged in the control group, although a much lower level of intensity was reported. Participants were also asked to fill out questionnaires concerning emotion regulation difficulties, emotion reactivity, depression, anxiety and worry. Hierarchical logistic regressions demonstrated that emotion regulation difficulties as well as emotion reactivity predicted PSP diagnosis after depression, anxiety and worry were controlled for. Furthermore, emotion regulation difficulties statistically mediated the relationship between emotion reactivity and PSP. Overall, the findings support an emotion regulation model of PSP.

Ultrasound Current Source Density Imaging

Surgery to correct severe heart arrhythmias usually requires detailed maps of the cardiac activation wave prior to ablation. The pinpoint electrical mapping procedure is laborious and limited by its spatial resolution (5-10 mm). We propose ultrasound current source density imaging (UCSDI), a direct 3-D imaging technique that potentially facilitates existing mapping procedures with superior spatial resolution. The technique is based on a pressure-induced change in resistivity known as the acoustoelectric (AE) effect, which is spatially confined to the ultrasound focus. AE-modulated voltage recordings are used to map and reconstruct current densities. In this preliminary study, we tested UCSDI under controlled conditions and compared it with conventional electrical mapping techniques. A 2-D dipole field was produced by a pair of electrodes in a bath of 0.9% NaCl solution. Boundary electrodes detected the AE signal while a 7.5-MHz focused ultrasound transducer was scanned across the bath. UCSDI located the current source and sink to within 1 mm of their actual positions. A future UCSDI system potentially provides real-time 3-D images of the cardiac activation wave coregistered with anatomical ultrasound and would greatly facilitate corrective procedures for heart abnormalities.

Real-time photoacoustic and ultrasound imaging: a simple solution for clinical ultrasound systems with linear arrays

Recent clinical studies have demonstrated that photoacoustic imaging (PAI) provides important diagnostic information during a routine breast exam for cancer. PAI enhances contrast between blood vessels and background tissue, which can help characterize suspicious lesions. However, most PAI systems are either not compatible with commercial ultrasound systems or inefficiently deliver light to the region of interest, effectively reducing the sensitivity of the technique. To address and potentially overcome these limitations, we developed an accessory for a standard linear ultrasound array that optimizes light delivery for PAI. The photoacoustic enabling device (PED) exploits an optically transparent acoustic reflector to help direct laser illumination to the region of interest. This study compares the PED with standard fiber bundle illumination in scattering and non-scattering media. In scattering media with the same incident fluence, the PED enhanced the photoacoustic signal by 18 dB at a depth of 5 mm and 6 dB at a depth of 20 mm. To demonstrate in vivo feasibility, we also used the device to image a mouse with a pancreatic tumor. The PED identified blood vessels at the periphery of the tumor, suggesting that PAI provides complementary contrast to standard pulse echo ultrasound. The PED is a simple and inexpensive solution that facilitates the translation of PAI technology to the clinic for routine screening of breast cancer.

Do self-statements enhance the effectiveness of virtual reality exposure therapy? A comparative evaluation in acrophobia.

There is a clear need for more detailed analysis of the role of cognitive self-statements in virtual reality exposure therapy (VRET). To date, no research on this topic has been done. The primary aim of this study was to investigate whether coping self-statements would enhance the effectiveness of VRET. In a randomized crossover design, 26 patients with acrophobia (DSM-IV diagnosis of specific phobia) were randomly assigned to two sessions of VRET followed by two sessions of VRET plus coping self-statements, or the other way around: first two sessions of VRET plus coping self-statements followed by two sessions of VRET. Results showed that VRET, regardless of addition of coping self-statements, decreased anxiety of heights, decreased avoidance of height situations, and improved attitudes towards heights. However, at 6-month follow-up, most gains during treatment were not fully retained.

Real-time, contrast enhanced photoacoustic imaging of cancer in a mouse window chamber.

A clinical ultrasound scanner and 14 MHz linear array collected real-time photoacoustic images (PAI) during an injection of gold nanorods (GNRs) near the region of a mature PC-3 prostate tumor in mice implanted with a skin flap window chamber. Three dimensional spectroscopic PAI (690-900 nm) was also performed to investigate absorption changes near the tumor and enhance specific detection of GNRs. Whereas GNRs improved PAI contrast (+18 dB), the photoacoustic spectrum was consistent with the elevated near infrared absorption of GNRs. The versatile imaging platform potentially accelerates development of photoacoustic contrast agents and drug delivery for cancer imaging and therapy.

Cardiac activation mapping using ultrasound current source density imaging (UCSDI)

We describe the first mapping of biological current in a live heart using ultrasound current source density imaging (UCSDI). Ablation procedures that treat severe heart arrhythmias require detailed maps of the cardiac activation wave. The conventional procedure is time-consuming and limited by its poor spatial resolution (5-10 mm). UCSDI can potentially improve on existing mapping procedures. It is based on a pressure-induced change in resistivity known as the acousto-electric (AE) effect, which is spatially confined to the ultrasound focus. Data from 2 experiments are presented. A 540 kHz ultrasonic transducer (f/# = 1, focal length = 90 mm, pulse repetition frequency = 1600 Hz) was scanned over an isolated rabbit heart perfused with an excitation-contraction decoupler to reduce motion significantly while retaining electric function. Tungsten electrodes inserted in the left ventricle recorded simultaneously the AE signal and the low-frequency electrocardiogram (ECG). UCSDI displayed spatial and temporal patterns consistent with the spreading activation wave. The propagation velocity estimated from UCSDI was 0.25 plusmn 0.05 mm/ms, comparable to the values obtained with the ECG signals. The maximum AE signal-to-noise ratio after filtering was 18 dB, with an equivalent detection threshold of 0.1 mA/ cm2. This study demonstrates that UCSDI is a potentially powerful technique for mapping current flow and biopotentialsin the heart.

Imaging current flow in lobster nerve cord using the acoustoelectric effect

Ultrasound traversing a biologic fluid or tissue generates a local change in electrical conductivity known as the acoustoelectric effect. The authors exploit this interaction to image ionic current injected into the abdominal segment of the lobster nerve cord. A pair of recording electrodes detected the acoustoelectric signal induced by pulses of focused ultrasound (1.4 or 7.5MHz). The signal was linear with injected current at 2MPa (0.7μV∕mAcm2) and pressure at 75mA∕cm2 (23μV∕MPa). Acoustoelectric imaging of biocurrents potentially enhances spatial resolution of traditional electrophysiology and merits further study as an imaging modality for neural applications.

Motor Inhibition, Reflection Impulsivity, and Trait Impulsivity in Pathological Skin Picking

Pathological skin picking (PSP) is often recognized as an impulse control disorder. The current study sought to investigate the relationship between PSP and different forms of impulsivity. University students that met criteria for PSP (n = 55) and university students without history of PSP (n = 55) answered a multidimensional impulsivity questionnaire (the UPPS Impulsive Behavior Scale) and completed 2 neurocognitive tasks that assess impulsivity (the Stop Signal Task and the Information Sampling Task). The PSP group scored significantly higher than the control group on the negative and positive urgency subscales of the UPPS, but the groups did not differ on other subscales or the neurocognitive tasks. Logistic regression demonstrated that the urgency scales added to the prediction of PSP after negative affect and other forms of impulsivity were adjusted for. The results indicate that PSP sufferers are characterized by emotion-based impulsivity and do not appear to be impulsive in other ways.

3-D photoacoustic and pulse echo imaging of prostate tumor progression in the mouse window chamber

Understanding the tumor microenvironment is critical to characterizing how cancers operate and predicting their response to treatment. We describe a novel, high-resolution coregistered photoacoustic (PA) and pulse echo (PE) ultrasound system used to image the tumor microenvironment. Compared to traditional optical systems, the platform provides complementary contrast and important depth information. Three mice are implanted with a dorsal skin flap window chamber and injected with PC-3 prostate tumor cells transfected with green fluorescent protein. The ensuing tumor invasion is mapped during three weeks or more using simultaneous PA and PE imaging at 25 MHz, combined with optical and fluorescent techniques. Pulse echo imaging provides details of tumor structure and the surrounding environment with 100-μm(3) resolution. Tumor size increases dramatically with an average volumetric growth rate of 5.35 mm(3)/day, correlating well with 2-D fluorescent imaging (R = 0.97, p < 0.01). Photoacoustic imaging is able to track the underlying vascular network and identify hemorrhaging, while PA spectroscopy helps classify blood vessels according to their optical absorption spectrum, suggesting variation in blood oxygen saturation. Photoacoustic and PE imaging are safe, translational modalities that provide enhanced depth resolution and complementary contrast to track the tumor microenvironment, evaluate new cancer therapies, and develop molecular contrast agents in vivo.

Inducing and Imaging Thermal Strain Using a Single Ultrasound Linear Array

For the first time, the feasibility of inducing and imaging thermal strain using an ultrasound imaging array is demonstrated. A commercial ultrasound scanner was used to heat and image a gelatin phantom with a cylindrical rubber inclusion. The inclusion was successfully characterized as an oil-bearing material using thermal strain imaging.