Publications by authors named "Thomas Riis"

Emerging neurostimulation methods aim to selectively modulate deep brain structures. Guiding these therapies has presented a substantial challenge, since imaging modalities such as MRI limit the spectrum of beneficiaries. In this study, we assess the guidance accuracy of a neuronavigation method that does not require taking MRI scans.

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Article Synopsis
  • Severe depression is associated with high activity in the subcallosal cingulate (SCC), and while surgical stimulation can help, existing noninvasive methods haven't targeted deep brain areas effectively.
  • A study involving 22 participants tested a new technique using low-intensity focused ultrasonic waves to stimulate the SCC while also measuring brain activity and mood changes.
  • Results showed that this stimulation reduced SCC activity and led to significant improvements in mood and depression scores compared to a sham treatment, suggesting potential for new therapeutic approaches targeting deep brain circuits.
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Direct interventions into deep brain circuits constitute promising treatment modalities for chronic pain. Cingulotomy and deep brain stimulation targeting the anterior cingulate cortex have shown notable improvements in the unpleasantness of pain, but these interventions require brain surgeries. In this study, we have developed an approach that can modulate this deep brain affective hub entirely noninvasively, using low-intensity transcranial-focused ultrasound.

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Transcranial focused ultrasound enables precise and non-invasive manipulations of deep brain circuits in humans, promising to provide safe and effective treatments of various neurological and mental health conditions. Ultrasound focused to deep brain targets can be used to modulate neural activity directly or localize the release of psychoactive drugs. However, these applications have been impeded by a key barrier-the human skull, which attenuates ultrasound strongly and unpredictably.

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: Transcranial focused low-intensity ultrasound has the potential to noninvasively modulate confined regions deep inside the human brain, which could provide a new tool for causal interrogation of circuit function in humans. However, it has been unclear whether the approach is potent enough to modulate behavior.: To test this, we applied low-intensity ultrasound to a deep brain thalamic target, the ventral intermediate nucleus, in three patients with essential tremor.

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Background: Severe forms of depression have been linked to hyperactivity of the subcallosal cingulate cortex. The ability to stimulate the subcallosal cingulate cortex or associated circuits noninvasively and directly would maximize the number of patients who could receive treatment. To this end, we have developed an ultrasound-based device for effective noninvasive modulation of deep brain circuits.

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Low-intensity focused ultrasound provides the means to noninvasively stimulate or release drugs in specified deep brain targets. However, successful clinical translations require hardware that maximizes acoustic transmission through the skull, enables flexible electronic steering, and provides accurate and reproducible targeting while minimizing the use of MRI. We have developed a device that addresses these practical requirements.

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Systems that emit electromagnetic or sonic waves for diagnostic or interventional applications often have constraints on the size of their aperture, and thus produce an elongated focus in the axial dimension. This extended depth of focus limits imaging resolution and spatial specificity of the delivered energy. Here, we have developed a method that substantially minimizes the depth of focus.

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Transcranial ultrasound is emerging as a noninvasive tool for targeted treatments of brain disorders. Transcranial ultrasound has been used for remotely mediated surgeries, transient opening of the blood-brain barrier, local drug delivery, and neuromodulation. However, all applications have been limited by the severe attenuation and phase distortion of ultrasound by the skull.

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Objective: Low-intensity ultrasound can stimulate excitable cells in a noninvasive and targeted manner, but which parameters are effective has remained elusive. This question has been difficult to answer because differences in transducers and parameters-frequency in particular-lead to profound differences in the stimulated tissue volumes. The objective of this study is to control for these differences and evaluate which ultrasound parameters are effective in stimulating excitable cells.

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Leprosy was a well-recognized and dreaded disease in medieval Europe. The disease is reported to have reached Germany with the Roman invasion and it was present in Scandinavia in the first centuries AD. This paper estimates and analyzes the frequency of leprosy among adult people buried in one of five medieval cemeteries in the city of Schleswig.

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