Reproducibility of brain metabolite concentration measurements in lesion free white matter at 1.5 T.

BACKGROUND: Post processing for brain spectra has a great influence on the fit quality of individual spectra, as well as on the reproducibility of results from comparable spectra. This investigation used pairs of spectra, identical in system parameters, position and time assumed to differ only in noise. The metabolite amplitudes of fitted time domain spectroscopic data were tested on reproducibility for the main brain metabolites. METHODS: Proton spectra of white matter brain tissue were acquired with a short spin echo time of 30 ms and a moderate repetition time of 1500 ms at 1.5 T. The pairs were investigated with one time domain post-processing algorithm using different parameters. The number of metabolites, the use of prior knowledge, base line parameters and common or individual damping were varied to evaluate the best reproducibility. RESULTS: The protocols with most reproducible amplitudes for N-acetylaspartate, creatine, choline, myo-inositol and the combined Glx line of glutamate and glutamine in lesion free white matter have the following common features: common damping of the main metabolites, a baseline using only the points of the first 10 ms, no additional lipid/macromolecule lines and Glx is taken as the sum of separately fitted glutamate and glutamine. This parameter set is different to the one delivering the best individual fit results. DISCUSSION: All spectra were acquired in "lesion free" (no lesion signs found in MR imaging) white matter. Spectra of brain lesions, for example tumors, can be drastically different. Thus the results are limited to lesion free brain tissue. Nevertheless the application to studies is broad, because small alterations in brain biochemistry of lesion free areas had been detected nearby tumors, in patients with multiple sclerosis, drug abuse or psychiatric disorders. CONCLUSION: Main metabolite amplitudes inside healthy brain can be quantified with a normalized root mean square deviation around 5 % using CH3 of creatine as reference. Only the reproducibility of myo-inositol is roughly twice as bad. The reproducibility should be similar using other references like internal or external water for an absolute concentration evaluation and are not influenced by relaxation corrections with literature values.

A novel Laser Navigation System reduces radiation exposure and improves accuracy and workflow of CT-guided spinal interventions: a prospective, randomized, controlled, clinical trial in comparison to conventional freehand puncture.

PURPOSE: Phantom model evaluation and prospective randomized clinical trial to assess the clinical feasibility and benefit of using a novel Laser Navigation System (LNS) in CT-guided epidural and perineural injections in comparison to the conventional freehand procedure. METHODS: The LNS guided puncture technique was compared to the standard CT-guided freehand treatment using a phantom model and a randomized clinical trial. Spinal injections were administered by an experienced interventional team to evaluate needle placement accuracy, treatment time and radiation exposure. RESULTS: In the LNS group of the phantom model study, the needle entrance point accuracy of 0.5mm (freehand 3.1mm), needle target point accuracy of 2.0mm (freehand 3.5mm), number of control CT slices of 1.4 (freehand 2.7) and needle placement time of 5min 4s (freehand: 9min 18s) showed significant improvements compared to freehand in 60 punctures. In the clinical trial the LNS group achieved needle entrance point accuracy of 1.3mm (freehand 4.6mm), needle angulation accuracy of 0.4° (freehand 2.3°), number of control CT slices of 1.1 (freehand 1.8) and needle placement time of 6min 54s (freehand 9min 00s), showing significant improvements compared to freehand in a total of 58 CT-guided interventions. CONCLUSION: The LNS group showed significantly improved results in both study designs. Both the phantom model evaluation and the clinical trial of spinal injections showed feasibility and efficacy of using the novel LNS. Even an experienced interventional team worked with it more precise, faster and with reduced radiation exposure.

Saline as the sole contrast agent for successful MRI-guided epidural injections.

PURPOSE: To assess the performance of sterile saline solution as the sole contrast agent for percutaneous magnetic resonance imaging (MRI)-guided epidural injections at 1.5 T. METHODS: A retrospective analysis of two different techniques of MRI-guided epidural injections was performed with either gadolinium-enhanced saline solution or sterile saline solution for documentation of the epidural location of the needle tip. T1-weighted spoiled gradient echo (FLASH) images or T2-weighted single-shot turbo spin echo (HASTE) images visualized the test injectants. Methods were compared by technical success rate, image quality, table time, and rate of complications. RESULTS: 105 MRI-guided epidural injections (12 of 105 with gadolinium-enhanced saline solution and 93 of 105 with sterile saline solution) were performed successfully and without complications. Visualization of sterile saline solution and gadolinium-enhanced saline solution was sufficient, good, or excellent in all 105 interventions. For either test injectant, quantitative image analysis demonstrated comparable high contrast-to-noise ratios of test injectants to adjacent body substances with reliable statistical significance levels (p < 0.001). The mean table time was 22 ± 9 min in the gadolinium-enhanced saline solution group and 22 ± 8 min in the saline solution group (p = 0.75). CONCLUSION: Sterile saline is suitable as the sole contrast agent for successful and safe percutaneous MRI-guided epidural drug delivery at 1.5 T.