Imaging of Deep Brain Stimulation Leads Using Extended Hounsfield Unit CT

Department of Neurosurgery, University of Washington, Seattle, WA 98195, USA.
Stereotactic and Functional Neurosurgery (Impact Factor: 2.02). 04/2009; 87(3):155-60. DOI: 10.1159/000209296
Source: PubMed


Deep brain stimulation (DBS) has become a routine therapy for Parkinson's disease. Standard CT imaging, often used to evaluate DBS electrodes in patients with limited benefit or significant side effects, has limitations including inability to distinguish different metallic components of the DBS lead. CT imaging with an extended Hounsfield unit (EHU) scale allows advanced image processing techniques to detect individual electrodes. EHU-CT may be co-registered to MRI volumes to provide accurate anatomical visualization of DBS lead contacts.

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    • "Postoperatively, he was more somnolent than expected. EHU head CT done for lead placement verification[11] showed a 3 × 9 mm right thalamic hyperdensity. After overnight observation, he was fully alert and oriented, and repeat CT showed no change in the thalamic hyperdensity. "
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    ABSTRACT: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) in particular is highly effective in relieving symptoms of Parkinson's disease (PD). However, it can also have marked psychiatric side effects, including delirium, mania, and psychosis. The etiologies of those effects are not well-understood, and both surgeons and consulting psychiatrists are in need of treatment strategies. Two patients with young onset of PD and without significant prior psychiatric problems presented for bilateral STN DBS when medications became ineffective. Both had uneventful operative courses but developed florid psychosis 1-2 weeks later, before stimulator activation. Neither showed signs of delirium, but both required hospitalization, and one required treatment with a first-generation antipsychotic drug. Use of that drug did not worsen PD symptoms, contrary to usual expectations. These cases describe a previously unreported post-DBS syndrome in which local tissue reaction to lead implantation produces psychosis even without electrical stimulation of subcortical circuits. The lesion effect also appears to have anti-Parkinsonian effects that may allow the safe use of otherwise contraindicated medications. These cases have implications for management of PD DBS patients postoperatively, and may also be relevant as DBS is further used in other brain regions to treat behavioral disorders.
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    • "An extended Hounsfield unit (EHU) mode is available on commercial CT scanners to improve the resolving capacity for metallic structures (Klotz et al., 1990; Link et al., 2000). This imaging algorithm increases the maximum HU value from 2 12 HU to 2 15 HU, allowing for the resolution of different metallic radio-opacities, and is ideal for visualizing DBS electrodes (Hebb and Poliakov, 2009). DBS leads consist of four platinum/iridium exposed active contacts and platinum/iridium insulated wires. "
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    ABSTRACT: Deep Brain Stimulation (DBS) is a routine therapy for movement disorders, and has several emerging indications. We present a novel protocol to define the stereotactic coordinates of metallic DBS implants that may be routinely employed for validating therapeutic anatomical targets. Patients were referred for troubleshooting or new DBS implantation. A volumetric MRI of the brain obtained prior to or during this protocol was formatted to the Anterior Commissure-Posterior Commissure (AC-PC) coordinate system. Patients underwent a CT scan of the brain in an extended Hounsfield unit (EHU) mode. A semi-automatic detection algorithm based on a Normalized Mutual Information (NMI) co-registration method was implemented to measure the AC-PC coordinates of each DBS contact. This algorithm was validated using manual DBS contact identification. Fifty MRI-CT image pairs were available in 39 patients with a total of 336 DBS electrodes. The median and mean Euclidean distance errors for automatic identification of electrode locations were 0.20mm and 0.22 mm, respectively. This method is an accurate method of localization of active DBS contacts within the sub-cortical region. As the investigational indications of DBS expand, this method may be used for verification of final implant coordinates, critical for understanding clinical benefit and comparing efficacy between subjects.
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