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Phantom Study (phantom + study)
Selected AbstractsMRA of intracranial aneurysms embolized with platinum coils: A vascular phantom study at 1.5T and 3TJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2008Shingo Kakeda Abstract Purpose To analyze the influence of matrix and echo time (TE) of three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) on the depiction of residual flow in aneurysms embolized with platinum coils at 1.5T and 3T. Materials and Methods A simulated intracranial aneurysm of the vascular phantom was loosely packed to maintain the patency of some residual aneurysmal lumen with platinum coils and connected to an electromagnetic flow pump with pulsatile flow. MRAs were obtained altering the matrix and TE of 3D TOF sequences at 1.5T and 3T. Results The increased spatial resolution and the shorter TE offered better image quality at 3T. For the depiction of an aneurysm remnant, the high-spatial-resolution 3T MRA (matrix size of 384 × 224 and 512 × 256) with a short TE of ,3.3 msec were superior to the 1.5T MRA obtained with any sequences. Conclusion 3T MRA is superior to 1.5T MRA for the assessment of aneurysms embolized with platinum coils; the combination of the 512 × 256 matrix and short TE (3.3 msec or less) seems feasible at 3T. J. Magn. Reson. Imaging 2008;28:13,20. © 2008 Wiley-Liss, Inc. [source] False-positive analysis of functional MRI during simulated deep brain stimulation: A phantom studyJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2008Ho-Ling Liu PhD Abstract Purpose To investigate the false-positive activations/deactivations in functional MRI (fMRI) of deep brain stimulation (DBS) using a phantom. Materials and Methods fMRI experiments were performed on a 1.5T scanner using a single-shot gradient-echo echo-planar imaging (GE-EPI) sequence (TR/TE/FA = 6000 msec/60 msec/90°) on an agar-gel phantom inserted with DBS electrodes. During the experimental blocks, two-second stimuli were delivered during the interscan waiting time (ISWT), which was adjusted by changing the number of slices acquired within the TR (3500 msec with 30 slices and 5160 msec with 10 slices). Data were analyzed using SPM2 software, and the false-positive voxels were detected with five different P-value thresholds. Results The number of false-positive voxels in experimental conditions had no significant differences from those in control conditions with either long or short ISWT, which increased with the P-value threshold from zero at P < 0.0001 to approximately 40 at P < 0.05. The pattern of increasing number of false-positive reactions along with P-value was similar between all conditions. Conclusion False-positive findings from fMRI with similar experimental design can be well controlled with a statistical threshold of P < 0.001 or tighter. The short ISWT of 3500 msec did not increase false-positive reactions compared to the long ISWT of 5160 msec. J. Magn. Reson. Imaging 2008;27:1439,1442. © 2008 Wiley-Liss, Inc. [source] Magnetic resonance image registration in multiple sclerosis: Comparison with repositioning error and observer-based variabilityJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2002I Leng Tan MD Abstract Purpose To study the use of image registration in the analysis of multiple sclerosis (MS) lesion volume and compare this with repositioning error and observer-based variability. Materials and Methods The normalized mutual information (NMI) algorithm is evaluated in an accuracy study using a phantom, followed by a validation study on magnetic resonance (MR) data of MS patients. Further, using scan-rescan MR data, the effect of registration on MS lesion volume compared with repositioning error and observer-based variability is assessed. Results The registration accuracy was near perfect in the phantom study, while the in vivo validation study demonstrated an accuracy on the order of 0.2,0.3 mm. In the scan-rescan study, quantification accounted for 15.6% of the relative variance, repositioning for 44.4%, and registration for 40.0%. Conclusion NMI resulted in robust and accurate alignment of MR brain images of MS patients. Its use in the detection of changes in MS using large serial MR imaging (MRI) data warrants future evaluation. J. Magn. Reson. Imaging 2002;15:505,510. © 2002 Wiley-Liss, Inc. [source] Effect of lateral target motion on image registration accuracy in CT-guided helical tomotherapy: A phantom studyJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 3 2010J Medwig Summary Optimisation of imaging modes for kilovoltage CT (kVCT) used for treatment planning and megavoltage CT (MVCT) image guidance used in ungated helical tomotherapy was investigated for laterally moving targets. Computed tomography images of the QUASARÔ Respiratory Motion Phantom were acquired without target motion and for lateral motion of the target, with 2-cm peak-to-peak amplitude and a period of 4 s. Reference kVCT images were obtained using a 16-slice CT scanner in standard fast helical CT mode, untagged average CT mode and various post-processed 4D-CT modes (0% phase, average and maximum intensity projection). Three sets of MVCT images with different inter-slice spacings of were obtained on a Hi-Art tomotherapy system with the phantom displaced by a known offset position. Eight radiation therapists performed co-registration of MVCT obtained with 2-, 4- and 6-mm slice spacing and kVCT studies independently for all 15 CT imaging combinations. In the investigated case, the untagged average kVCT and 4-mm slice spacing for the MVCT yielded more accurate registration in the transverse plane. The average residual uncertainty of this combination of imaging procedures was 0.61 ± 0.16 mm in the longitudinal direction, 0.45 ± 0.14 mm in the anterior,posterior direction and insignificant in the lateral direction. Manual registration of MVCT,kVCT study pairs is necessary to account for a target in significant lateral motion with respect to bony structures. [source] Use of the NeuroMate stereotactic robot in a frameless mode for functional neurosurgery,THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 2 2006T. R. K. Varma Abstract Background The aim of this paper is to describe the use of the NeuroMate stereotactic robot for functional neurosurgery with a novel frameless ultrasound registration system. Methods A retrospective review of the evaluation and clinical use of the NeuroMate stereotactic robot in a frameless mode for functional neurosurgery. Results Prior to its clinical use a phantom study was undertaken to demonstrate an application accuracy of 1.29 mm. Subsequently the robot has been used in 153 functional neurosurgical procedures including 113 deep brain stimulator implantations. Conclusions The NeuroMate stereotactic robot in a frameless mode has sufficient accuracy for a range of functional neurosurgical procedures, including movement disorder surgery. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||