Voxel-based dose calculation in radiocolloid therapy of cystic craniopharyngiomas

Very high doses are administered in radiocolloid therapy of cystic craniopharyngiomas. However individual dose planning is not common yet mainly due to insufficient image resolution. Our aim was to investigate whether currently available high-resolution image data can be used for voxel-based dose calculation for short-ranged beta-emitters (P-32,Y-90,Re-186) and to assess the achievable accuracy. We developed a convolution algorithm based on voxelized dose activity distributions and dose-spread kernels. Results for targets with 5-40 mm diameter were compared with high-resolution Monte Carlo calculations in spherical phantoms. Voxel size was 0.35 mm. Homogeneous volume and surface activity distributions were used. Dose-volume histograms of targets and shell structures were compared and gamma index (dose tolerance 5%, distance to agreement 0.35 mm) was calculated for dose profiles along the principal axes. For volumetric activity distributions 89.3% +/- 11.9% of all points passed the gamma test (mean gamma 0.53 +/- 0.16). For surface distributions 33.6% +/- 14.8% of all points passed the gamma test (mean gamma 2.01 +/- 0.60). The shift of curves in dose-volume histograms was -1.7 Gy +/- 7.6 Gy (-4.4 Gy +/- 24.1 Gy for Re-186) in volumetric distributions and 46.3% +/- 32.8% in surface distributions. The results show that individual dose planning for radiocolloid therapy of cystic craniopharyngiomas based on high-resolution voxelized image data is feasible and yields highly accurate results for volumetric activity distributions and reasonable dose estimates for surface distributions

Dysarthria in pallidal Deep Brain Stimulation in dystonia depends on the posterior location of active electrode contacts: a pilot study

Background: Pallidal Deep Brain Stimulation (GPi-DBS) is an efficient treatment for primary dystonia. We investigated stimulation-induced dysarthria, which is the most frequent side-effect of GPi-DBS. Methods: Speech was recorded while reading a standard text, and performing rapid syllable repetitions ON and OFF DBS in ten dystonia patients (6 men; 3 cervical, 4 segmental, 3 generalized, unselected for DBS-related speech impairments). Speech and articulation rate, pauses, and syllable repetition rates were extracted via acoustic analysis. Locations of active stimulation contacts and volumes of tissue activated (VTA) were calculated. Results: The number of pauses increased significantly ON vs. OFF stimulation (Wilcoxon test, p < 0.05). More posteriorly localized active contacts were associated with slower syllable repetition (Pearson correlation, p < 0.05). VTA size did not correlate with any measure of dysarthria. Conclusion: Using quantitative acoustic signal analysis, this study demonstrates that GPi-DBS alters motor aspects of speech. Both inadvertent stimulation of parts of the internal capsule, or interference with GPi function and outflow are possible causes. Understanding causes of GPi-DBS-induced speech changes can improve DBS programming. (C) 2017 The Authors. Published by Elsevier Ltd

Frame-based stereotactic biopsy of deep-seated and midline structures in 511 procedures: feasibility, risk profile, and diagnostic yield

Objectives We evaluated the feasibility, safety, and diagnostic yield of frame-based stereotactic biopsies (SB) in lesions located in deep-seated and midline structures of the brain to analyze these parameters in comparison to other brain areas. Patients and methods In a retrospective, tertiary care single-center analysis, we identified all patients who received SB for lesions localized in deep-seated and midline structures (corpus callosum, basal ganglia, pineal region, sella, thalamus, and brainstem) between January 1996 and June 2015. Study participants were between 1 and 82 years. We evaluated the feasibility, procedural complications (mortality, transient and permanent morbidity), and diagnostic yield. We further performed a risk analysis of factors influencing the latter parameters. Chi-square test, Student t test, and Mann-Whitney rank-sum test were used for statistical analysis. Results Four hundred eighty-nine patients receiving 511 SB procedures (median age 48.5 years, range 1-82; median Karnofsky Performance Score 80%, range 50-100%, 43.8% female/56.2% male) were identified. Lesions were localized in the corpus callosum (29.5%), basal ganglia (17.0%), pineal region (11.5%), sella (7.8%), thalamus (4.3%), brainstem (28.8%), and others (1.1%). Procedure-related mortality was 0%, and permanent morbidity was 0.4%. Transient morbidity was 9.6%. Histological diagnosis was possible in 99.2% (low-grade gliomas 16.2%, high-grade gliomas 40.3%, other tumors in 27.8%, no neoplastic lesions 14.5%, no definitive histological diagnosis 0.8%). Only the pons location correlated significantly with transient morbidity (p < 0.001). Conclusion In experienced centers, frame-based stereotactic biopsy is a safe diagnostic tool with a high diagnostic yield also for deep-seated and midline lesions