The Neuroradiology Journal 20: 574-579, 2007
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Diffusion Tensor Imaging and 3D Tractography of the Cervical Spinal Cord Using the ECG-Gated Line-scan Technique. A Feasibility Study
M. HORI*,**, K. ISHIGAME**, S. AOKI***, H. KUMAGAI**, T. ARAKI** * Radiology Department, Toho University; Ota, Tokyo, Japan ** Radiology Department, University of Yamanashi; Chuou, Yamanashi, Japan *** Radiology Department, University of Tokyo; Bunkyo, Tokyo, Japan Key words: MR imaging, diffusion tensor imaging, spinal cord
SUMMARY – Diffusion tensor (DT) magnetic resonance (MR) imaging in addition to conventional MR images provide valuable information on the brain. This study compared line scan DT imaging with and without the ECG-gating technique to estimate clinical usefulness of the line scan diffusion tensor image (LSDTI) with ECG-gating in evaluating spinal cord diseases in vivo. First, five healthy volunteers participated in the comparison study. LSDWI was performed in three to five sagittal sections with a pulsed-field-gradient diffusion preparation pulse employing two different b-values (0 and 700 s/mm2) along six directions. Apparent diffusion coefficient (ADC) maps and fractional anisotropy (FA) were calculated and three-dimensional tract reconstruction and color schemes of the spinal cord were obtained. Image quality and the acquisition time of each LSDTI were compared. Second, LSDTI with ECG-gating was performed in eighteen patients with cervical spinal cord disorders and evaluated by two neuroradiologists. Images with the ECG-gated technique were all superior to those without ECG–gating. Mean extended time for LSDTI with ECGgating was approximately two minutes. In clinical use, the ADC and FA of spinal cord in patients with cervical spondylotic myelopathy statically changed. Moreover, demonstration of fibers was correlated with clinical symptoms. ECG-gating technique is preferable to LSDTI. The ADC and FA measurements and 3D fiber tracking of LSDTI with ECG-gating are promising methods to estimate cervical spinal cord pathology in clinical use.
Introduction Diffusion tensor (DT) magnetic resonance (MR) imaging in addition to conventional MR images provide valuable information on the brain. Recently, some diffusion-weighted or DT imaging of cervical spinal cord has been reported 1-18 in clinical use and this technique has become an important tool to estimate cervical spinal cord disorders. However, the quality of DT images of the spinal cord remains unsatisfactory compared with those of the brain. Difficulties of DT imaging of the spinal cord in vivo involve technical problems, such as susceptibility artifacts and motion due to cerebrospinal fluid (CSF) pulsation. Among several DT imaging sequences for 574
the spinal cord, line scan diffusion tensor image (LSDTI) is the simple spin-echo based image and the feasibility of LSDTI has been reported 2,7,10,15,17,18. This technique has usually been acquired without cardiac gating because of its relatively longer acquisition time than those of other methods. However, pulsation of CSF surrounding spinal cord may affect quantitative measurements of diffusion parameters (apparent diffusion coefficient [ADC] and fractional anisotropy [FA]) and description of three-dimensional tractography because they were based on a voxel based procedure. Data acquisition with echocardiogram (ECG) gating has the potential to reduce this effect. The purposes of this study were to compare line scan diffusion tensor imaging with and
M. Hori
Diffusion Tensor Imaging and 3D Tractography of the Cervical Spinal Cord Using the ECG-Gated Line-scan Technique
without ECG-gating technique and to estimate the clinical feasibility of LSDTI with ECG-gating in evaluating spinal cord diseases in vivo. Methods All examinations were performed on a clinical MR system (Signa Lx CV/NV 1.5 Tesla, GE Healthcare, Milwaukee, Illinois USA). The line scan technique has been described in detail 18,19. In brief, the characteristics of the technique, low sensitivity to magnetic field susceptibility, chemical shift and eddy currents results in good image quality with minimal distortions because it is a simple spin-echo based method. Volunteer Study
Five healthy volunteers without a history of spinal disease participated in this study. To cover the whole cervical spinal cord, LSDTI was performed in three to five sagittal sections. LSDTI is a line scan spin-echo sequence with a pulsed-field-gradient diffusion preparation pulse employing two different b-values (0 and 700 s/mm2) along six directions. Imaging parameters of LSDTI were as follows: TR/ TE =800 without ECG gating, approximately 1200 with ECG gating/80 ms, matrix 128×64 (256×256 reconstructed), bandwidth = 3.92 kHz, FOV = 240×120 mm, slice thickness/gap=3/0 mm and b value of 0 and 700 s/mm2 with the maximum b value applied in six directions ((1,1,0), (0,1,1), (1,0,1), (0,1,–1), (1,–1,0), (–1,0,1)). Subsequently, apparent diffusion coefficient (ADC) maps and fractional anisotropy (FA) were calculated from the obtained LSDWI images on a pixel by pixel basis using software (Functool 2, General Electronic Medical Systems, Milwaukee, WI). Moreover, three-dimensional tract reconstruction and color schemes of spinal cord to represent the orientation of anisotropic tissues are obtained on a PC using free software (dTV 1.5, mage Computing and Analysis Laboratory, Tokyo, Japan). Spinal tracts were created with an FA threshold of 0.22 as described elsewhere 12,13,17 . Image quality of each LSDTI was qualitatively compared by two neuroradiologists, grading a three-point scale: one signified that LSDTI with ECG gating was inferior to LSDTI without ECG gating; 2, LSDTI with ECG gating was comparable to LSDTI without ECG gating; 3, LSDTI with ECG gating was superior to LSDTI without ECG gating. Mean extended time with ECG gating technique, compared with non-ECG gating was calculated.
Patient Study
For the clinical feasibility study, LSDTI with ECG-gating was performed in eighteen patients with cervical spinal cord disorders (ten men and eight women, mean age 46 years, 11 with spondylotic myelopathy, three with syringomyelia, two with spinal AVM, one with spinal cavernous angioma and one with multiple sclerosis) after conventional MR examination (T2 and T1 weighted sagittal imaging and T2 and T1 weighted para-axial imaging). Imaging parameters were the same as for the volunteer study. Informed consent was obtained from each patient. We obtained ethical approval from the institutional review board before this study. Twenty-one images (three sagittal sections, six DT images and one b=0 image per each section) of LSDTI images were obtained for each patient and sent to an independent workstation (Advantage Windows, General Electronic Medical Systems, Milwaukee, WI). ADC and FA maps were calculated and three-dimensional tract reconstruction and color schemes were created as described above. An ROI analysis for spinal cord was performed in patients with spondylotic myelopathy and syringomyelia on ADC and FA maps and the quantitative values compared with those of normal volunteers. ROIs were placed in the center of spinal cord at the spinal canal level C2 to C3, C3 to C4, C4 to C5 and C5 to C6 to exclude any cerebrospinal fluid contribution on the images obtained with a b value of 0 s/mm2 and then were projected onto FA maps and ADC maps, where ROI mean signal intensities were calculated. Demonstration of spinal cord tracts on 3D tract reconstruction was evaluated by two neuroradiologists visually, referring to clinical symptoms or other MR images. Results Volunteer Study
All LSDTI examinations were successfully imaged. Images with ECG-gated technique were all superior to those without ECG–gating in imaging quality (figure 1). Both neuroradiologists judged 3 (LSDTI with ECG gating was superior to LSDTI without ECG gating) in grading score in all volunteers’ images. The mean LSDTI durations were approximately 12 minutes without ECG-gated technique and 14 minutes with it, depending on the patients’ 575
Diffusion Tensor Imaging and 3D Tractography of the Cervical Spinal Cord Using the ECG-Gated Line-scan Technique
A
M. Hori
B
Figure 1 Normal spinal cord, ADC map without (A) and with (B) ECG gating. A pseudo-lesion (arrow) is shown in the narrowed and irregular shaped spinal cord due to CSF pulsation (A).
heart rate. Mean extended time for LSDTI with ECG-gating was approximately two minutes, which were permissible for clinical use. Patient Study
Except for one patient, LSDTI was successfully imaged. LSDTI failed in the patient with multiple sclerosis because of the patient’s motion. In clinical use, The ADC value of spinal cord in patients with cervical spondylotic myelopathy increased (P
www. centauro. it
Diffusion Tensor Imaging and 3D Tractography of the Cervical Spinal Cord Using the ECG-Gated Line-scan Technique. A Feasibility Study
M. HORI*,**, K. ISHIGAME**, S. AOKI***, H. KUMAGAI**, T. ARAKI** * Radiology Department, Toho University; Ota, Tokyo, Japan ** Radiology Department, University of Yamanashi; Chuou, Yamanashi, Japan *** Radiology Department, University of Tokyo; Bunkyo, Tokyo, Japan Key words: MR imaging, diffusion tensor imaging, spinal cord
SUMMARY – Diffusion tensor (DT) magnetic resonance (MR) imaging in addition to conventional MR images provide valuable information on the brain. This study compared line scan DT imaging with and without the ECG-gating technique to estimate clinical usefulness of the line scan diffusion tensor image (LSDTI) with ECG-gating in evaluating spinal cord diseases in vivo. First, five healthy volunteers participated in the comparison study. LSDWI was performed in three to five sagittal sections with a pulsed-field-gradient diffusion preparation pulse employing two different b-values (0 and 700 s/mm2) along six directions. Apparent diffusion coefficient (ADC) maps and fractional anisotropy (FA) were calculated and three-dimensional tract reconstruction and color schemes of the spinal cord were obtained. Image quality and the acquisition time of each LSDTI were compared. Second, LSDTI with ECG-gating was performed in eighteen patients with cervical spinal cord disorders and evaluated by two neuroradiologists. Images with the ECG-gated technique were all superior to those without ECG–gating. Mean extended time for LSDTI with ECGgating was approximately two minutes. In clinical use, the ADC and FA of spinal cord in patients with cervical spondylotic myelopathy statically changed. Moreover, demonstration of fibers was correlated with clinical symptoms. ECG-gating technique is preferable to LSDTI. The ADC and FA measurements and 3D fiber tracking of LSDTI with ECG-gating are promising methods to estimate cervical spinal cord pathology in clinical use.
Introduction Diffusion tensor (DT) magnetic resonance (MR) imaging in addition to conventional MR images provide valuable information on the brain. Recently, some diffusion-weighted or DT imaging of cervical spinal cord has been reported 1-18 in clinical use and this technique has become an important tool to estimate cervical spinal cord disorders. However, the quality of DT images of the spinal cord remains unsatisfactory compared with those of the brain. Difficulties of DT imaging of the spinal cord in vivo involve technical problems, such as susceptibility artifacts and motion due to cerebrospinal fluid (CSF) pulsation. Among several DT imaging sequences for 574
the spinal cord, line scan diffusion tensor image (LSDTI) is the simple spin-echo based image and the feasibility of LSDTI has been reported 2,7,10,15,17,18. This technique has usually been acquired without cardiac gating because of its relatively longer acquisition time than those of other methods. However, pulsation of CSF surrounding spinal cord may affect quantitative measurements of diffusion parameters (apparent diffusion coefficient [ADC] and fractional anisotropy [FA]) and description of three-dimensional tractography because they were based on a voxel based procedure. Data acquisition with echocardiogram (ECG) gating has the potential to reduce this effect. The purposes of this study were to compare line scan diffusion tensor imaging with and
M. Hori
Diffusion Tensor Imaging and 3D Tractography of the Cervical Spinal Cord Using the ECG-Gated Line-scan Technique
without ECG-gating technique and to estimate the clinical feasibility of LSDTI with ECG-gating in evaluating spinal cord diseases in vivo. Methods All examinations were performed on a clinical MR system (Signa Lx CV/NV 1.5 Tesla, GE Healthcare, Milwaukee, Illinois USA). The line scan technique has been described in detail 18,19. In brief, the characteristics of the technique, low sensitivity to magnetic field susceptibility, chemical shift and eddy currents results in good image quality with minimal distortions because it is a simple spin-echo based method. Volunteer Study
Five healthy volunteers without a history of spinal disease participated in this study. To cover the whole cervical spinal cord, LSDTI was performed in three to five sagittal sections. LSDTI is a line scan spin-echo sequence with a pulsed-field-gradient diffusion preparation pulse employing two different b-values (0 and 700 s/mm2) along six directions. Imaging parameters of LSDTI were as follows: TR/ TE =800 without ECG gating, approximately 1200 with ECG gating/80 ms, matrix 128×64 (256×256 reconstructed), bandwidth = 3.92 kHz, FOV = 240×120 mm, slice thickness/gap=3/0 mm and b value of 0 and 700 s/mm2 with the maximum b value applied in six directions ((1,1,0), (0,1,1), (1,0,1), (0,1,–1), (1,–1,0), (–1,0,1)). Subsequently, apparent diffusion coefficient (ADC) maps and fractional anisotropy (FA) were calculated from the obtained LSDWI images on a pixel by pixel basis using software (Functool 2, General Electronic Medical Systems, Milwaukee, WI). Moreover, three-dimensional tract reconstruction and color schemes of spinal cord to represent the orientation of anisotropic tissues are obtained on a PC using free software (dTV 1.5, mage Computing and Analysis Laboratory, Tokyo, Japan). Spinal tracts were created with an FA threshold of 0.22 as described elsewhere 12,13,17 . Image quality of each LSDTI was qualitatively compared by two neuroradiologists, grading a three-point scale: one signified that LSDTI with ECG gating was inferior to LSDTI without ECG gating; 2, LSDTI with ECG gating was comparable to LSDTI without ECG gating; 3, LSDTI with ECG gating was superior to LSDTI without ECG gating. Mean extended time with ECG gating technique, compared with non-ECG gating was calculated.
Patient Study
For the clinical feasibility study, LSDTI with ECG-gating was performed in eighteen patients with cervical spinal cord disorders (ten men and eight women, mean age 46 years, 11 with spondylotic myelopathy, three with syringomyelia, two with spinal AVM, one with spinal cavernous angioma and one with multiple sclerosis) after conventional MR examination (T2 and T1 weighted sagittal imaging and T2 and T1 weighted para-axial imaging). Imaging parameters were the same as for the volunteer study. Informed consent was obtained from each patient. We obtained ethical approval from the institutional review board before this study. Twenty-one images (three sagittal sections, six DT images and one b=0 image per each section) of LSDTI images were obtained for each patient and sent to an independent workstation (Advantage Windows, General Electronic Medical Systems, Milwaukee, WI). ADC and FA maps were calculated and three-dimensional tract reconstruction and color schemes were created as described above. An ROI analysis for spinal cord was performed in patients with spondylotic myelopathy and syringomyelia on ADC and FA maps and the quantitative values compared with those of normal volunteers. ROIs were placed in the center of spinal cord at the spinal canal level C2 to C3, C3 to C4, C4 to C5 and C5 to C6 to exclude any cerebrospinal fluid contribution on the images obtained with a b value of 0 s/mm2 and then were projected onto FA maps and ADC maps, where ROI mean signal intensities were calculated. Demonstration of spinal cord tracts on 3D tract reconstruction was evaluated by two neuroradiologists visually, referring to clinical symptoms or other MR images. Results Volunteer Study
All LSDTI examinations were successfully imaged. Images with ECG-gated technique were all superior to those without ECG–gating in imaging quality (figure 1). Both neuroradiologists judged 3 (LSDTI with ECG gating was superior to LSDTI without ECG gating) in grading score in all volunteers’ images. The mean LSDTI durations were approximately 12 minutes without ECG-gated technique and 14 minutes with it, depending on the patients’ 575
Diffusion Tensor Imaging and 3D Tractography of the Cervical Spinal Cord Using the ECG-Gated Line-scan Technique
A
M. Hori
B
Figure 1 Normal spinal cord, ADC map without (A) and with (B) ECG gating. A pseudo-lesion (arrow) is shown in the narrowed and irregular shaped spinal cord due to CSF pulsation (A).
heart rate. Mean extended time for LSDTI with ECG-gating was approximately two minutes, which were permissible for clinical use. Patient Study
Except for one patient, LSDTI was successfully imaged. LSDTI failed in the patient with multiple sclerosis because of the patient’s motion. In clinical use, The ADC value of spinal cord in patients with cervical spondylotic myelopathy increased (P
