Repeatability and reproducibility of cerebral 23Na imaging in healthy subjects

Abstract Background Initial reports of 23Na magnetic resonance imaging (MRI) date back to the 1970s. However, methodological challenges of the technique hampered its widespread adoption for many years. Recent technical developments have overcome some of these limitations and have led to more optimal conditions for 23Na-MR imaging. In order to serve as a reliable tool for the assessment of clinical stroke or brain tumor patients, we investigated the repeatability and reproducibility of cerebral sodium (23Na) imaging in healthy subjects. Methods In this prospective, IRB approved study 12 consecutive healthy volunteers (8 female, age 31 ± 8.3) underwent three cerebral 23Na-MRI examinations at 3.0 T (TimTrio, Siemens Healthineers) distributed between two separate visits with an 8 day interval. For each scan a T1w MP-RAGE sequence for anatomical referencing and a 3D-density-adapted, radial GRE-sequence for 23Na-imaging were acquired using a dual-tuned (23Na/1H) head-coil. On 1 day, these scans were repeated consecutively; on the other day, the scans were performed once. 23Na-sequences were reconstructed according to the MP-RAGE sequence, allowing direct cross-referencing of ROIs. Circular ROIs were placed in predetermined anatomic regions: gray and white matter (GM, WM), head of the caudate nucleus (HCN), pons, and cerebellum. External 23Na-reference phantoms were used to calculate the tissue sodium content. Results Excellent correlation was found between repeated measurements on the same day (r2 = 0.94), as well as on a different day (r2 = 0.86). No significant differences were found based on laterality other than in the HCN (63.1 vs. 58.7 mmol/kg WW on the right (p = 0.01)). Pronounced inter-individual differences were identified in all anatomic regions. Moderate to good correlation (0.310 to 0.701) was found between the readers. Conclusion Our study has shown that intra-individual 23Na-concentrations in healthy subjects do not significantly differ after repeated scans on the same day and a pre-set time interval. This confirms the repeatability and reproducibility of cerebral 23Na-imaging. However, with manual ROI placement in predetermined anatomic landmarks, fluctuations in 23Na-concentrations can be observed

Crossed cerebellar diaschisis in acute isolated thalamic infarction detected by dynamic susceptibility contrast perfusion MRI.

PURPOSE: Crossed cerebellar diaschisis (CCD) is a state of neural depression caused by loss of connections to injured neural structures remote from the cerebellum usually evaluated by positron emission tomography. Recently it has been shown that dynamic susceptibility contrast perfusion weighted MRI (PWI) may also be feasible to detect the phenomenon. In this study we aimed to assess the frequency of CCD on PWI in patients with acute thalamic infarction. METHODS: From a MRI report database we identified patients with acute isolated thalamic infarction. Contralateral cerebellar hypoperfusion was identified by inspection of time to peak (TTP) maps and evaluated quantitatively on TTP, mean transit time (MTT), cerebral blood flow and volume (CBF, CBV) maps. A competing cerebellar pathology or an underlying vascular pathology were excluded. RESULTS: A total of 39 patients was included. Common symptoms were hemiparesis (53.8%), hemihypaesthesia (38.5%), dysarthria (30.8%), aphasia (17.9%), and ataxia (15.4%). In 9 patients (23.1%) PWI showed hypoperfusion in the contralateral cerebellar hemisphere. All of these had lesions in the territory of the tuberothalamic, paramedian, or inferolateral arteries. Dysarthria was observed more frequently in patients with CCD (6/9 vs. 6/30; OR 8.00; 95%CI 1.54-41.64, p = 0.01). In patients with CCD, the median ischemic lesion volume on DWI (0.91 cm³), IQR 0.49-1.54 cm³) was larger compared to patients with unremarkable PWI (0.51 cm³, IQR 0.32-0.74, p = 0.05). The most pronounced changes were found in CBF (0.94±0.11) and MTT (1.06±0.13) signal ratios, followed by TTP (1.05±0.02). CONCLUSIONS: Multimodal MRI demonstrates CCD in about 20% of acute isolated thalamic infarction patients. Lesion size seems to be a relevant factor in its pathophysiology

Laser-guided cervical selective nerve root block with the Dyna-CT: initial experience of three-dimensional puncture planning with an ex-vivo model.

BACKGROUND: Cervical selective nerve root block (CSNRB) is a well-established, minimally invasive procedure to treat radicular cervical pain. However, the procedure is technically challenging and might lead to major complications. The objective of this study was to evaluate the feasibility of a three-dimensional puncture planning and two-dimensional laser-guidance system for CSNRB in an ex-vivo model. METHODS: Dyna-CT of the cervical spine of an ex-vivo lamb model was performed with the Artis Zee® Ceiling (Siemens Medical Solutions, Erlangen, Germany) to acquire multiplanar reconstruction images. 15 cervical nerve root punctures were planned and conducted with the syngo iGuide® laser-guidance system. Needle tip location and contrast dye distribution were analyzed by two independent investigators. Procedural, planning, and fluoroscopic time, tract length, and dose area product (DAP) were acquired for each puncture. RESULTS: All 15 punctures were rated as successful with 12 punctures on the first attempt. Total procedural time was approximately 5 minutes. Mean planning time for the puncture was 2.03 (±0.39) min. Mean puncture time was 2.16 (±0.32) min, while mean fluoroscopy time was 0.17 (±0.06) min. Mean tract length was 2.68 (±0.23) cm. Mean total DAP was 397.45 (±15.63) µGy m(2). CONCLUSION: CSNRB performed with Dyna-CT and the tested laser guidance system is feasible. 3D pre-puncture planning is easy and fast and the laser-guiding system ensures very accurate and intuitive puncture control

Value of dynamic susceptibility contrast perfusion MRI in the acute phase of transient global amnesia.

Transient global amnesia (TGA) is a transitory, short-lasting neurological disorder characterized by a sudden onset of antero- and retrograde amnesia. Perfusion abnormalities in TGA have been evaluated mainly by use of positron emission tomography (PET) or single-photon emission computed tomography (SPECT). In the present study we explore the value of dynamic susceptibility contrast perfusion-weighted MRI (PWI) in TGA in the acute phase.From a MRI report database we identified TGA patients who underwent MRI including PWI in the acute phase and compared these to control subjects. Quantitative perfusion maps (cerebral blood flow (CBF) and volume (CBV)) were generated and analyzed by use of Signal Processing In NMR-Software (SPIN). CBF and CBV values in subcortical brain regions were assessed by use of VOI created in FIRST, a model-based segmentation tool in the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FSL).Five TGA patients were included (2 men, 3 women). On PWI, no relevant perfusion alterations were found by visual inspection in TGA patients. Group comparisons for possible differences between TGA patients and control subjects showed significant lower rCBF values bilaterally in the hippocampus, in the left thalamus and globus pallidus as well as bilaterally in the putamen and the left caudate nucleus. Correspondingly, significant lower rCBV values were observed bilaterally in the hippocampus and the putamen as well as in the left caudate nucleus. Group comparisons for possible side differences in rCBF and rCBV values in TGA patients revealed a significant lower rCBV value in the left caudate nucleus.Mere visual inspection of PWI is not sufficient for the assessment of perfusion changes in TGA in the acute phase. Group comparisons with healthy control subjects might be useful to detect subtle perfusion changes on PWI in TGA patients. However, this should be confirmed in larger data sets and serial PWI examinations

Demographic characteristics, ischemic lesion size and localization on diffusion-weighted images (DWI) as well as frequency of clinical symptoms in isolated thalamic infarction patients with crossed cerebellar diaschisis (CCD) and normal PWI.

<p>Demographic characteristics, ischemic lesion size and localization on diffusion-weighted images (DWI) as well as frequency of clinical symptoms in isolated thalamic infarction patients with crossed cerebellar diaschisis (CCD) and normal PWI.</p

Two examples of crossed cerebellar diaschisis.

<p>1. A 75-year-old female patient with reduced vigilance, dysarthria, and right-sided hemihypaesthesia: <i>A</i> Trace diffusion-weighted image shows an acute ischemic lesion (arrow) in the territory of the left tuberothalamic artery with <i>B</i> matching hypoperfusion (arrow) on the time to peak (TTP) map. <i>C</i> In the cerebellum trace DWI is unremarkable while <i>D</i> TTP demonstrates hypoperfusion in the contralteral cerebellar hemisphere. 2. A 65-year-old female patient with right-sided hemiparesis: <i>E</i> Trace DWI shows an acute ischemic lesion (arrow) in the territory of the left paramedian artery with <i>F</i> minor hypoperfusion (arrow) on TTP. <i>G</i> In the cerebellum trace DWI is unremarkable while <i>H</i> TTP demonstrates hypoperfusion in the contralateral cerebellar hemisphere.</p

Pre-interventional interventional table positioning and laser-guided puncture.

<p>Correct pre-interventional positioning of the free-floating interventional table shown as three lines properly positioned in the indicated triangle (<b>B</b>). Correct laser-guided puncture along the planned trajectory indicated by the needle in-line with the 2D laser cross (<b>B</b>).</p

Detailed data for cervical selective nerve root block using Dyna-CT with syngo iGuide® laser-guidance.

1<p>DAP: dose area product.</p