Purpose: To develop and validate a three-dimensional (3D) single breath-hold, projection reconstruction (PR), balanced steady state free precession (SSFP) method for cardiac function evaluation against a two-dimensional (2D) multislice Fourier (Cartesian) transform (FT) SSFP method. Materials and Methods:The 3D PR SSFP sequence used projections in the x-y plane and partitions in z, providing 70 -80 msec temporal resolution and 1.7 ϫ 1.7 ϫ 8 -10 mm in a 24-heartbeat breath hold. A total of 10 volunteers were imaged with both methods, and the measurements of global cardiac function were compared. Results:Mean signal-to-noise ratios (SNRs) for the blood and myocardium were 114 and 42 (2D) and 59 and 21 (3D). Bland-Altman analysis comparing the 2D and 3D ejection fraction (EF), left ventricular end diastolic volume (LVEDV) and end systolic volume (LVESV), and end diastolic myocardial mass (LVEDM) provided values of bias Ϯ2 SD of 0.6% Ϯ 7.7 % for LVEF, 5.9 mL Ϯ 20 mL for LVEDV, -2.8 mL Ϯ 12 mL for LVESV, and -0.61 g Ϯ 13 g for LVEDM. 3D interobserver variability was greater than 2D for LVEDM and LVESV. Conclusion:In a single breath hold, the 3D PR method provides comparable information to the standard 2D FT method, which employs 10 -12 breath holds.

Object The availability of sophisticated neural probes is a key prerequisite in the development of future brain-machine interfaces (BMIs). In this study, the authors developed and validated a neural probe design capable of simultaneous drug delivery and electrophysiology recordings in vivo. Focal drug delivery promises to extend dramatically the recording lives of neural probes, a limiting factor to clinical adoption of BMI technology. Methods To form the multifunctional neural probe, the authors affixed a 16-channel microfabricated silicon electrode array to a fused silica catheter. Three experiments were conducted in rats to characterize the performance of the device. Experiment 1 examined cellular damage from probe insertion and the drug distribution in tissue. Experiment 2 measured the effects of saline infusions delivered through the probe on concurrent electrophysiological measurements. Experiment 3 demonstrated that a physiologically relevant amount of drug can be delivered in a controlled fashion. For these experiments, Hoechst and propidium iodide stains were used to assess insertion trauma and the tissue distribution of the infusate. Artificial CSF (aCSF) and tetrodotoxin (TTX) were injected to determine the efficacy of drug delivery. Results The newly developed multifunctional neural probes were successfully inserted into rat cortex and were able to deliver fluids and drugs that resulted in the expected electrophysiological and histological responses. The damage from insertion of the device into brain tissue was substantially less than the volume of drug dispersion in tissue. Electrophysiological activity, including both individual spikes as well as local field potentials, was successfully recorded with this device during real-time drug delivery. No significant changes were seen in response to delivery of aCSF as a control experiment, whereas delivery of TTX produced the expected result of suppressing all spiking activity in the vicinity of the catheter outlet. Conclusions Multifunctional neural probes such as the ones developed and validated within this study have great potential to help further understand the design space and criteria for the next generation of neural probe technology. By incorporating integrated drug delivery functionality into the probes, new treatment options for neurological disorders and regenerative neural interfaces using localized and feedback-controlled delivery of drugs can be realized in the near future.

Robot-assisted stereotactic neurosurgery is an emerging technology with a growing range of applications. The ROSA system is a robotic stereotactic system that has been shown to be accurate in laboratory studies and large case series. The goal of this study was to examine the accuracy of the ROSA across different registration methods as well as different clinical applications. Sixteen patients with one hundred and seventeen stereotactic trajectories were examined. Accuracy was compared by measuring the distance between the trajectory target and the actual termination of the device as determined by imaging. Entry error and angular deviation were also measured. Variables included bone fiducials vs. laser facial scanning, the clinical indication for stereotactic surgery, and the effect of lead deflection on accuracy. Bone fiducials did not offer an accuracy benefit over laser facial scanning (mean target error 4.5-3.9 mm, p = 0.34) in these clinical scenarios. Laser interstitial thermal therapy, responsive neurostimulation, and stereo electroencephalography were equally accurate when placed by the ROSA (mean target error 4.4-4.3-4.0 mm, respectively, p = 0.69). Deflection did not affect lead accuracy (mean target error 4.4-3.9 mm, p = 0.11). Similar results are seen for entry error and angular deviation. ROSA is a highly accurate stereotactic system. Laser facial scanning provides the same accuracy as bone fiducials in these stereotactic applications. The ROSA is equally accurate across a wide spectrum of applications. The ROSA is effective at limiting lead deflection, and when it does occur, it does not impact target accuracy in a significant way.

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The undersampled radial acquisition has been widely employed for accelerated (by a factor R ‫؍‬ N r /N p ) cardiac imaging, but the resulting reduction in image quality has not been well characterized. This investigation presents a method of measuring these artifacts through synthetic undersampling of high SNR images (SNR ≥ 30). After validating the method in phantoms, the method was applied to a study of short-axis, long-axis, and coronary MRI imaging in healthy subjects. For 60 projections (60 N p ), the total artifact is ϳ10% for short and long-axis imaging (R ‫؍‬ 2.1) and ϳ15% for coronary MRI (R ‫؍‬ 3.7). For 60 N p , the SD of artifact in the region of the heart is 2% for short-and long-axis imaging (R ‫؍‬ 2.1) and 3.5% for coronary MRI (R ‫؍‬ 3.7). The artifact content is less in the region of the heart than in the periphery. The artifact is very reproducible among subjects for standard views. A study of coronary MRI at progressively fewer projections (at constant scan time) showed that right coronary MRI images were acceptable if total artifact was <6. Many investigators have demonstrated the value of undersampled radial acquisition for accelerated imaging (1-6). There have been efforts to measure and assess the impact of radial undersampling on image quality (6 -10). Notably, Pipe et al. observed that by Parseval's theorem for the Fourier transform, the artifact power for undersampled imaging is proportional to the signal power that resides in the misrepresented Fourier coefficients (7). Nevertheless, the impact of radial undersampling on image quality is still not well understood, compared to the understanding for other fast imaging methods, e.g., parallel imaging (11,12), variable rate k-space sampling schemes (13) (14 -16), half Fourier (17), echo-planar imaging (18) or simply imaging with high receiver bandwidth imaging (19,20). The important question is, at what undersampling level, for each application, does the image begin to deteriorate rapidly due to artifacts, beyond the typical SNR loss with square-root of acquisition time? It is not possible to provide a general rule for the permitted radial undersampling level for all applications, since artifacts depend on anatomy and spatial frequency content. Yet it is not currently known for each application what level of undersampling is acceptable. Furthermore, because the radial undersampling artifact is so dispersed, artifacts are often judged visually to be acceptable (12), while producing unacceptable levels of noise-like diffuse spray (1,6,21), which effectively reduces the signal-to noise-ratio (SNR). And low SNR images (e.g., delayed enhancement imaging) will permit very little undersampling, but this is due to SNR limitations and not undersampling artifact.The purpose of this study is to validate a method for measuring artifacts and to determine the aliasing signal present for many levels of undersampling for typical cardiac applications. This allows determination of the artifact signal in percentages for each application. This level of artifa...

BACKGROUND Deep brain stimulation (DBS) has been used for chronic pain for decades, but its use is limited due to a lack of reliable data about its efficacy for specific indications. OBJECTIVE To report on 9 patients who underwent DBS for facial pain, with a focus on differences in outcomes between distinct etiologies. METHODS We retrospectively reviewed 9 patients with facial pain who were treated with DBS of the ventral posteromedial nucleus of the thalamus and periventricular gray. We report on characteristics including facial pain etiology, complications, changes in pain scores using the visual analog scale (VAS), and willingness to undergo DBS again. RESULTS Nine patients underwent DBS for either poststroke, post-traumatic, postherpetic, or atypical facial pain. Eight patients (89%) were permanently implanted. Seven patients had sufficient follow-up (mean 40.3 mo). Of these 7 patients, average VAS scores decreased from 9.4 to 6.1 after DBS. The average decrease in VAS was 55% for post-traumatic facial pain (2 patients), 45% for poststroke (2 patients), 15% for postherpetic neuralgia (2 patients), and 0% for atypical facial pain (1 patient). Three of the 8 implanted patients (38%) had complications which required removal of hardware. Only 2 of 7 (29%) patients met classical criteria for responders (50% decrease in pain scores). However, among 4 patients who were asked about willingness to undergo DBS again, all expressed that they would repeat the procedure. CONCLUSION There is a trend towards improvement in pain scores following DBS for facial pain, most prominently with post-traumatic pain.

BACKGROUND When evaluating deep brain stimulation (DBS) for newer indications, patients may benefit from trial stimulation prior to permanent implantation or for investigatory purposes. Although several case series have evaluated infectious complications among DBS patients who underwent trials with external hardware, outcomes have been inconsistent. OBJECTIVE To determine whether a period of lead externalization is associated with an increased risk of infection. METHODS We conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses compliant systematic review of all studies that included rates of infection for patients who were externalized prior to DBS implantation. A meta-analysis of proportions was performed to estimate the pooled proportion of infection across studies, and a meta-analysis of relative risks was conducted on those studies that included a control group of nonexternalized patients. Heterogeneity across studies was assessed via I2 index. RESULTS Our search retrieved 23 articles, comprising 1354 patients who underwent lead externalization. The pooled proportion of infection was 6.9% (95% CI: 4.7%-9.5%), with a moderate to high level of heterogeneity between studies (I2 = 62.2%; 95% CI: 40.7-75.9; P &lt; .0001). A total of 3 studies, comprising 212 externalized patients, included a control group. Rate of infection in externalized patients was 5.2% as compared to 6.0% in nonexternalized patients. However, meta-analysis was inadequately powered to determine whether there was indeed no difference in infection rate between the groups. CONCLUSION The rate of infection in patients with electrode externalization is comparable to that reported in the literature for DBS implantation without a trial period. Future studies are needed before this information can be confidently used in the clinical setting.

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