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BACKGROUND AND OBJECTIVES: Linear metrics for ventricular volume play a large role in the rapid, approximate evaluation of ventricular volume. In this article, we automatically extract linear measures of ventricular volume to explore their correlation with lateral ventricular volume (LVV) in the healthy adult population and comprehensively define normal values. METHODS: We automatically extract Evans' ratio (ER), Frontal-Occipital Horn Ratio (FOHR), and anteroposterior lateral ventricle index (ALVI) from an open MRI data set of healthy adults (https://brain-development.org/ixi-dataset/). Indices have been correlated with corresponding LVVs and lateral ventricular volumes divided by supratentorial brain volumes. Spearman rank correlation was used to compare strength of correlation. RESULTS: ER shows correlation with lateral ventricle volume based on sex (r = 0.58; men, r = 0.65; women P < .001), including when controlling for supratentorial volume (r = 0.57; men, r = 0.63). ER did not profoundly correlate with age (r = 0.29, men; r = 0.35, women; P < .001) and seemed normally distributed around 0.25. ALVI showed strong correlation with LVV with only slight gender differences (r = 0.83, men; r = 0.84, women) and LVV to supratentorial cortical volume ratio (r = 0.9, men; r = 0.86, women). FOHR was also normally distributed around a value of 0.37 and showed moderate correlation with LVV (r = 0.68, men; r = 0.73, women) and LVV to supratentorial cortical volume ratio (r = 0.69, men; r = 0.74, women). CONCLUSION: ALVI is a newer index with strong correlation with LVV and has strong potential for clinical use. Both FOHR and ER show moderate correlation with LVV. Reference values for linear estimates of ventricular volume may help clinicians better identify patients with pathological ventriculomegaly.
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BACKGROUND: The ClearPoint neuronavigation system affords real-time magnetic resonance imaging (MRI) guidance during stereotactic procedures. While such information confers potential clinical benefits, additional operative time may be needed. METHODS: We conducted a retrospective analysis of procedural time associated with ClearPoint Stereotaxis, with hypothesis that this procedural time is comparable with that associated with frame-based biopsy. RESULTS: Of the 52 patients evaluated, the total procedural time for ClearPoint stereotactic biopsy averaged 150.0 (±40.4) minutes, of which 111.5 (±16.5) minutes were dedicated to real-time MRI acquisition and trajectory adjustment. This procedural time is within the range of those reported for frame-based needle biopsies. Approximately 5 minutes of the procedural time is related to the mounting of the MRI-compatible stereotactic frame. Based on the procedural time, we estimate that four cases are required in the learning curve to achieve this efficiency. Efficient algorithms for distortion corrections and isocenter localization are keys to ClearPoint stereotaxis. Routine quality assurance/control after each MRI software update and institutional information technology maintenance also contribute to efficiency. Real-time MRI is essential for definitive diagnosis in select cases. CONCLUSIONS: ClearPoint stereotactic needle biopsy can be achieved in time frames comparable to frame-based stereotaxis. However, procedural efficiency requires 4 "learning curve" cases as well as vigilance in terms of MR distortion correction and information technology maintenance.