Showing papers by "Sarah J. Nelson published in 2003"

Multivoxel magnetic resonance spectroscopy of brain tumors.

Abstract: Magnetic resonance spectroscopy (MRS) is becoming more widely available for clinical applications and is able to provide information about the metabolic properties of regions of normal and abnormal tissue morphology. A critical question for the clinical management of patients with brain tumors is whether multivoxel MRS is able to add new information to the high-quality anatomical data provided by conventional MR imaging techniques and whether this information is relevant for the diagnosis and clinical management of such patients. In this article, the state of the art for acquiring and analyzing multivoxel MRS data is reviewed and placed in context relative to imaging findings for metastatic and primary brain tumors. The MRS data are seen to provide unique information that when combined with high-quality anatomical MR images has implications for defining tumor type and grade, directing biopsy or surgical resection, planning focal radiation or biological therapies, and understanding the mechanisms of success and failure of new treatments.

Assessment of metastatic cervical adenopathy using dynamic contrast-enhanced MR imaging.

Abstract: BACKGROUND AND PURPOSE: Morphologic assessment by conventional imaging methods of lymph node metastases in patients with squamous cell carcinoma of the head and neck is, at best, insensitive. Doppler sonography has shown that lymph node metastases exhibit alterations in the number of vessels and blood flow. We assessed the ability of dynamic contrast-enhanced MR imaging to differentiate normal from diseased nodes in this patient population. METHODS: Twenty-one patients with newly diagnosed squamous cell carcinoma and no previous treatment were studied with the use of a head and neck phased array surface coil. Anatomic imaging included high resolution T1-weighted, fat-saturated fast spin-echo T2-weighted, and contrast-enhanced T1-weighted imaging (0.99–1.32 mm3 voxels). The dynamic contrast-enhanced MR imaging was performed by using a 2D fast spoiled gradient recalled sequence with single dose bolus injection of contrast agent. Calculated values included time to peak, peak enhancement, maximum slope, and washout slope for the enhancement. All patients underwent neck dissection as part of their indicated treatment, and imaging results were correlated with pathologic findings. RESULTS: Dynamic contrast-enhanced MR imaging and pathology comparisons were obtained for 68 nodes. There was significantly longer time to peak ( P < .001), lower peak enhancement ( P < .05), lower maximum slope ( P < .01), and slower washout slope ( P < .05) in the tumor-involved nodes compared with the normal nodes. CONCLUSION: Analysis of dynamic contrast-enhanced MR imaging can differentiate normal from diseased lymph nodes in patients with squamous cell carcinoma of the head and neck.

Imaging Glioblastoma Multiforme

Abstract: Glioblastoma multiforme are infiltrative lesions that have a high degree of heterogeneity, both within and between different patients Imaging is critical for all phases in the evaluation and treatment of these lesions, but has been limited in providing information that is reliable enough to stratify patients into groups with uniform behavior and to predict outcome Although magnetic resonance imaging is the method of choice for visualizing anatomic features of the lesion, its results are ambiguous in terms of defining the functional characteristics of the lesion and distinguishing tumor from treatment induced necrosis Recent advances in magnetic resonance have made possible the routine acquisition of physiological data such as perfusion- and diffusion-weighted images and of metabolic data such as water suppressed proton spectroscopic images These provide quantitative measurements that are more closely related to the biological properties of the tumor and reflect changes in tumor vascularity, cellularity and proliferation that are associated with tumor progression As the molecular properties that influence invasion and neoplastic transformation are elucidated, it is critical that noninvasive imaging techniques are available for investigating new therapies and tailoring treatment to individual patient characteristics The data obtained from patients with glioblastoma multiforme have already demonstrated that these new magnetic resonance techniques are able to contribute to diagnosis, characterization of malignant potential, treatment planning and assessment of response to therapy

Directional diffusion in relapsing-remitting multiple sclerosis: a possible in vivo signature of Wallerian degeneration.

Abstract: Purpose To examine the role of directional dependence of the apparent diffusion coefficients in the evaluation of normal-appearing brain regions of patients with relapsing-remitting multiple sclerosis. Materials and Methods The role of diffusion tensor eigenvalues was investigated in the normal-appearing brain regions for 18 patients with relapsing-remitting multiple sclerosis and 15 age-matched normal controls. Results The isotropic apparent diffusion was increased in all regions. However, reduced anisotropy was significant only in regions with high anisotropy, including the corpus callosum and the internal capsule, and was due to increased diffusion tensor eigenvalues corresponding to diffusion transverse to the fibers without significant increase along the fibers. This characteristic pattern of changes in diffusion tensor eigenvalues has been observed previously in cases of Wallerian degeneration. Low-anisotropy regions corresponded to gray matter and gray/white interface regions. Since fiber tract orientations are not determined for regions of low anisotropy, this characteristic pattern of diffusion change is not detectable in these regions. Conclusion Examination of diffusion tensor eigenvectors may provide insight into the changes observed in diffusion and a signature of Wallerian degeneration in the normal-appearing white matter of relapsing-remitting multiple sclerosis patients. J. Magn. Reson. Imaging 2003;18:420–426. © 2003 Wiley-Liss, Inc.

MRI lesion volume heterogeneity in primary progressive MS in relation with axonal damage and brain atrophy

Abstract: Objectives: To investigate whether axonal damage in primary progressive (PP) multiple sclerosis (MS), as measured by proton magnetic resonance spectroscopy (HMRS) imaging and brain atrophy, is a function of T2 weighted brain lesion volume. Methods: 34 PP MS patients were divided into two categories: low ( 3 , n = 18) or high (≥3 cm 3 , n = 16) T2 lesion load (LL). An Index of Brain Atrophy (IBA) was calculated and HMRS metabolite ratios were derived from a central brain area centred at the corpus callosum. Results: Patient groups did not differ with regard to clinical characteristics and showed lower mean IBA and mean N -acetylaspartate:creatinine (NAA:Cr) ratios compared to healthy controls. Conclusion: PP patients with low and high brain T2LL have detectable brain atrophy and NAA:Cr reduction compared to healthy controls. In PP MS, T2 lesions alone are insufficient to explain the presence of brain atrophy and decrease in NAA:Cr.

Challenges in dynamic contrast‐enhanced MRI imaging of cervical lymph nodes to detect metastatic disease

Abstract: Purpose To identify and overcome challenges in using dynamic contrast-enhanced magnetic resonance imaging (MRI) to distinguish tumor from nontumor in the cervical lymph nodes of patients with squamous cell carcinoma of the head and neck. Materials and Methods Signal-to-noise ratio (S/N), motion, node heterogeneity, and tissue normalizations were examined. Twenty-one patients with squamous cell carcinoma of the head and neck were scanned before a neck dissection (two-dimensional fast spoiled gradient-echo: 10 locations/13 seconds). Peak time, peak enhancement, maximum upslope, and washout slope were measured in pathologically confirmed tumor and nontumor nodes and in the submandibular gland and the sternocleidomastoid muscle. Results Surface coil arrays provided high coverage and high S/N. Motion averaged 1.1 pixels and was corrected. Large tumor nodes were heterogeneous in their contrast enhancement, while the nontumor nodes were homogeneous. The contrast enhancement parameters were significantly different for all regions except for the submandibular gland compared to the nontumor nodes. Conclusion Challenges of dynamic imaging of cervical lymph nodes were overcome and significant differences were found between the tumor and nontumor nodes, indicating that dynamic imaging is feasible and may aid this patient population. J. Magn. Reson. Imaging 2003;17:455–462. © 2003 Wiley-Liss, Inc.

Brain lesion volume and neuropsychological function predict efficacy of treatment for depression in multiple sclerosis.

Abstract: This study examined the effects of brain lesions and neuropsychological impairment on the efficacy of treatment for depression in patients with comorbid diagnoses of multiple sclerosis (MS) and major depressive disorder (MDD). Thirty patients meeting criteria for MS and MDD received 1 of 3 16-week treatments for depression and were followed for 6 months following treatment cessation. T2-weighted magnetic resonance imaging and neuropsychological evaluations were also obtained. End-of-treatment Beck Depression Inventory (BDI; A. T. Beck, C. H. Ward, M. Mendelson, J. Mock, & J. Erbaugh, 1961) results residualized for baseline BDI were related to right temporal periventricular lesion volume (R2=.32, p=.002) and left temporal grey-white junction lesion volume (R2=.19, p=.02) but were not statistically related to lesion volume in any other brain region or to neuropsychological function. BDI results at 6-month follow-up, residualized for end-of-treatment BDI, were predicted by total lesion volume (R2=.22, p=.005), lesion volume in many discrete areas, and neuropsychological functioning (R2=.29, p=.0009). The effect of total lesion volume on 6-month follow-up BDI results was fully mediated by neuropsychological function.

Standardized, Reproducible, High Resolution Global Measurements of T1 Relaxation Metrics in Cases of Multiple Sclerosis

Abstract: BACKGROUND AND PURPOSE: We herein present a methodology for standardized and clinically applicable measurement of T1 relaxation maps with high resolution and volumetric coverage by using the commercially available 3D spoiled gradient-echo sequence. The reproducibility of the T1 metrics derived from these maps and their sensitivity to distinguish between control participants and patients with multiple sclerosis are evaluated. METHODS: Axial view 3D RF spoiled data sets with two flip angles were acquired at 1.5 T to generate the T1 maps, with all other imaging parameters (27/6 ms [TR/TE]; field of view, 180 × 240 × 186 mm3; matrix, 192 × 256 × 124) kept identical between the two acquisitions. T1 maps were collected from 20 normal control participants and 32 patients with multiple sclerosis. An automated and operator-independent method was developed to segment the relaxation maps and define T1 metrics. RESULTS: We showed that the metrics derived from these maps to represent tissue characteristics were highly reproducible (coefficient of variation, approximately 1% to 4%) and were significantly different between normal control participants and patients with multiple sclerosis ( P < .001) for the small cohort of patients in this study. CONCLUSION: The commercially accessible 3D spoiled gradient-echo sequence can be used to generate T1 relaxation maps with high resolution and volumetric coverage. The metrics derived from the relaxation maps are reproducible and have been shown to be sensitive to qualitative and quantitative differences between subgroups of patients with multiple sclerosis and control participants, with strong statistical significance. The use of a commercially available sequence enables the standardization and comparison of T1 metrics across different multiple sclerosis centers.

Reliable in vivo lactate and lipid estimation in glioma patients

Abstract: Lactate is a sensitive indicator of anaerobic glycolysis and reduced cellular oxygenation in living tissues. Mobile lipid resonances have been correlated with necrosis and cell breakdown. Reliable estimates of levels of lactate and lipid are of interest for evaluating prognosis and hence guiding the clinical management of patients with brain tumors. The goal of this study was to develop a robust and reliable estimation scheme to evaluate the in vivo lactate and lipid levels in glioma patients. The acquisition method combined J-difference modulation and reduced k-space sampling to obtain two set of 3D 1H-magnetic resonance spectroscopic imaging (MRSl) data, from which lactate editing was implemented. An iterative nonlinear least-squares algorithm for fitting Voigt line shape models in the frequency domain was developed for quantification for choline, creatine, NAA, lactate and lipid after non-parametric phase, frequency and baseline correction. Simulated data showed that the presented algorithm was robust and reliable. The quantification scheme was also applied to sixteen glioma patients prior to therapy.

3T Brain Spectroscopy: Repeatability and Inter-subject Variability

Abstract: Spectra were all acquired on either a 1.5T or 3T GE Signa scanner (Milwaukee, WI) with similar sequences and gradient performances using volume head coils. Automated-PRESS, PROBE™, was used at TE 35, along with a t1-oversampled 2DJ spectrum to capture metabolite T2’s (4). For 2DJ f1=0 spectra, peak heights were also compared. Data were analyzed with and without frame-by-frame water referencing (5), to determine any variation due to physiological noise or system drift. To match the expected 2-fold increase in linewidth (1/πT2*), data were apodized by a 2Hz Gaussian filter at 1.5T and a 4Hz Gaussian filter at 3.0T. Creatine linewidth was taken from the 2DJ spectrum without any apodization. Both prescriptions delineated a 2cm x 2cm x 2cm volume. 128 averages were taken for the PROBE TE 35 data. TE-averaged data (2DJ f1=0) data were sampled from 35ms to 195ms in 64 steps of 2.5ms, with NEX =4 per step. Results Figure 1a shows typical spectra from a 3T “white” matter prescription. Creatine linewidth at 3.0T ranged from 5.4Hz – 8.9Hz and at 1.5T from 3.5Hz – 4.4Hz. A single exponential fit to the Creatine methyl T2 relaxation in the corresponding TE-averaged data is shown in Figure 1b. Relaxivity values are uncorrected for diffusion. Repeatability was established both in phantom and in vivo. T2eff, amplitude and metabolite ratio repeatability measurements were all found to be significantly less than the inter-subject variations reported. T2eff, ratios and T2eff-corrected ratios are given in Table 1. In addition to the metabolites listed, the TE averaged spectra provided a direct measure of Glutamate and myo-Inositol, both of which gave less than 10% standard deviation across our volunteer group. Discussion T2 differences were less than previously reported. Creatine was the shortest at 143ms for gray at 3T, and 205 msec at 1.5T. In all cases, Creatine T2 values had the narrowest inter-subject distribution. NAA had the longest T2’s with larger gray/white differences with a significant decrease in 3T gray matter. Most interesting, at least in this limited population, is the large variation in choline T2’s at both field strengths.