Single-voxel Proton MR Spectroscopy Research Articles

Proton MR Spectroscopy in Normal Breasts Between Pre- and Postmenopausal Women: A Preliminary Study

The purpose of our study was to assess the differences in the water and lipid fractions and lipid line widths in normal breasts between premenopausal and postmenopausal women using single-voxel proton MR spectroscopy (1H-MRS). Thirty-two premenopausal and 25 postmenopausal women were enrolled in the study. Single-voxel proton MR spectroscopy of the breast was performed using point-resolved spectroscopy (PRESS) with water suppression and stimulated echo acquisition mode (STEAM). On STEAM, water fraction 1 was the ratio of the integration of water to the sum of the integration of water and methylene resonances, and the lipid fraction 1 was the ratio of the integration of methylene to water and methylene resonances. Lipid fraction 2 was the ratio of the integration of allylic methylene to water and allylic methylene resonances. Lipid line width was measured on PRESS. The premenopausal group had a higher water fraction 1 and lower lipid fraction 1 than the postmenopausal group (p < 0.01, Student's t test). The breast density had a positive effect on water fraction 1 and a negative effect on lipid fraction 1 for premenopausal women (p = 0.018, multivariate regression) and for the total population (p = 0.019). The premenopausal women had a higher lipid fraction 2 than postmenopausal women without significance (Student's t test), but the premenopausal status had a positive effect on lipid fraction 2 (p = 0.024, multivariate regression). There was no significant correlation between all independent variables and lipid line width. Breast 1H-MRS shows the differences of water and lipid compositions between pre- and postmenopausal women. Lipids containing methylene and allylic methylene protons had different implications in normal breasts.

Prognostic value of high-field proton magnetic resonance spectroscopy in patients presenting with clinically isolated syndromes suggestive of multiple sclerosis

The aim of this study was to determine the prognostic value of metabolic alterations in the normal-appearing white matter (NAWM) of patients presenting with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) with special regard to the prediction of conversion to definite MS. Using a 3T whole-body MR system, a multisequence conventional MRI protocol and single-voxel proton MR spectroscopy (PRESS, repetition time 2000 ms, echo times 38 ms and 140 ms) of the parietal NAWM were performed in 25 patients presenting with CIS at baseline and in 20 controls. Absolute concentrations of N-acetyl-aspartate (tNAA), myo-inositol (Ins), choline (Cho) and creatine (tCr) as well as metabolite ratios were determined. Follow-up including neurological assessment and conventional MRI was performed 3-4 and 6-7 months after the initial event. Nine patients converted to definite MS during the follow-up period. Compared to controls, those patients who converted to MS also showed significantly lower tNAA concentrations in the NAWM (-13.4%, P = 0.002) whereas nonconverters (-6.5%, P = 0.052) did not. The Ins concentration was 20.2% higher in the converter group and 1.9% higher in the nonconverter group, but these differences did not reach significance. No significant differences could be observed for tCr and Cho in either patient group. Axonal damage at baseline in patients presenting with CIS was more prominent in those who subsequently converted to definite MS in the short term follow-up, indicating that tNAA might be a sufficient prognostic marker for patients with a higher risk of conversion to early definite MS.

Interferon Beta-1b May Reverse Axonal Dysfunction in Multiple Sclerosis

Progression of the disability of multiple sclerosis (MS) is thought to be related to axonal damage that is seen even in normal appearing white matter (NAWM) of patients' brains. Interferon beta (IFNβ) treatment for MS reduces the frequency of clinical exacerbations and the appearance of new inflammatory demyelinating lesions on magnetic resonance imaging (MRI). However, the effect of IFNβ treatment on axonal damage in MS is not known. The present study aimed to assess the effect of IFNβ on axonal function by comparing the data from localised single voxel proton MR spectroscopy (MRS) performed on eight MS patients given IFNβ-1b treatment and 11 untreated patients. Brain MRI and MRS were performed before the initiation of IFNβ-1b treatment and 24 months after treatment initiation. Levels of N-acetylaspartate (NAA), choline-containing compounds (Cho) and creatine (Cr) were calculated as the areas under their peaks shown on MRS and the ratios of NAA/Cr and Cho/Cr were calculated. In the patients treated with IFNβ-1b there was a significant increase in the ratio of NAA/Cr in NAWM (p=0.028) at 24 months after the initiation of treatment. In contrast, there was no significant change in the NAA/Cr ratio in the untreated patients. These results suggest that IFNβ-1b treatment might recover axonal function in NAWM of MS patients.

Single voxel proton MR spectroscopy findings of typical and atypical intracranial meningiomas

Purpose To prospectively define proton magnetic resonance spectroscopy (MRS) findings of meningiomas, and describe the ability or inability of short- and long-echo MRS to differentiate typical and atypical meningiomas in vivo. Material and methods Seventeen patients with pathologically confirmed typical meningiomas and six with atypical meningiomas were evaluated with conventional MR imaging and MRS before resection. MRS studies using point-resolved spectroscopy (PRESS) localisation, at short- and long-echo time (TR 2000 ms, TE: 30 and 144 ms, 64–96 acquisition) were acquired on a 1.5 T scanner. MRS data obtained from these patients were compared with histopathological findings. Mean cellular proliferation (MIB-1) antibody staining against the Ki-67 antigen was also determined in all meningiomas. Results Prominent choline (Cho) was present in all meningiomas. Alanine (Ala) was observed in 21 cases of the 23 meningiomas. Acetylaspartate (NAA) and creatine (Cr) were either not observed or detected in minimal amounts in at all both groups of meningiomas on long TE (144 ms) spectra. The mean Cho/Cr values in the four atypical meningiomas were 4.44 ± 0.30 (mean ± standard deviation) and 3.39 ± 0.52 in the 12 typical meningiomas on short TE spectra. Cho/Cr ratio could not be determined in the other seven cases because of a lack of creatine peak. Of the five meningiomas in which a lactate peak was detected, four were in typical cases and only one was in atypical meningioma. Mean MIB-1 proliferation index was 3.7% in typical meningiomas and 10% in atypical meningiomas. Conclusion Prominent Cho, absence or low amount of NAA and Cr, and presence of Ala were common characteristics of spectral pattern of both atypical and typical meningiomas on MRS. MRS cannot reliably differentiate typical intracranial meningiomas from atypical meningiomas preoperatively. Mean MIB-1 proliferation index was well correlated with histopathology findings.

Magnetic Resonance Spectroscopy of the Thalamus in Essential Tremor Patients

ABSTRACTBackground and Purpose. Although essential tremor (ET) is one of the most common movement disorders, its pathogenesis remains obscure. The ventral intermediate nucleus of the thalamus (VIM nucleus) is suggested to play an important role in the occurrence of disease. In this study, the authors investigated the presence of biochemical or metabolic alterations in the thalamus of patients with ET using magnetic resonance (MR) spectroscopy. Methods. The study group included 14 patients with ET who suffered from tremor predominantly in their right arm and 9 healthy controls. All patients and controls were right handed. Following conventional cranial MR imaging, single voxel protonMRspectroscopy of the thalamus involving the VIM nuclei was performed bilaterally in both the patients with ET and controls. Metabolite peaks of choline (Cho), creatine (Cr), and Nacetylaspartate (NAA) were obtained from each spectroscopic volume of interest. The right and left thalamic NAA/Cr and Cho/ Cr ratios were compared first within the patient group and then between the control and patient groups. The differences in age and spectroscopic data between groups were assessed using the Mann‐Whitney U test, whereas the comparison within groups between left thalamus and right thalamus was done by the Wilcoxon test. Results. In patients with ET, the NAA/Cr ratio of the right thalamus was found to be significantly higher than the NAA/Cr ratio of the left thalamus (P= .02). However, NAA/Cr and Cho/Cr ratios were found to be similar (P &gt; .05) when we compared the control and patient groups for the right thalamus and then the left thalamus. Conclusion. These data present preliminary evidence for metabolic alterations of the contralateral thalamus (namely, low NAA/Cr ratio) in ET patients with predominantly involved right arm. However, the series is small and further data are necessary to clear the subject adequately.

Detection and differentiation of lactate and lipids by single-voxel proton MR spectroscopy

The signals of lactate and lipids partially overlap in single-voxel proton MR spectroscopy (1HMRS), sometimes making them difficult to differentiate in clinical settings. Our aim in this study was to identify lactate and lipids by varying the echo time (TE). We expect that the accurate detection of lactate and lipids will have high diagnostic value in the diagnosis of brain tumors. Following our protocol, we obtained meaningful 1HMRS spectra from 213 patients, including 163 patients with brain tumors, between August 1999 and February 2004. 1HMRS was performed with a TE of 144 ms followed by a TE of 30 ms and/or a TE of 288 ms, if necessary. For the 213 patients, lactate level was "negative" in 47 patients, "positive" in 131 patients, and "strongly positive" in 35 patients. The lipid level was "negative" in 90 patients, "positive" in 56 patients, and "strongly positive" in 67 patients. Based on logistic discriminant analyses of neuro-epithelial tumor WHO grade and lactate and lipid levels, lactate and lipid levels were significant between WHO grades 2 and 3 (P=0.0239) and between grades 3 and 4 (P=0.0347). Lipids are a more significant factor for the discrimination between WHO grades 2 and 3 (P=0.0073) and between grades 3 and 4 (P=0.0048). With our method of varying the TE, it is possible accurately and efficiently to detect lactate and lipids in the brain. We found a significant correlation between lactate and lipid expression and WHO grade of neuro-epithelial tumors.

Magnetic Resonance Spectroscopy Features of Uterine Leiomyomas

Objective: The purpose of this study is to investigate the in vivo magnetic resonance spectroscopy features of uterine leiomyomas using long echo time and to characterize the spectral patterns of these lesions. Methods: We calculated metabolites in 15 patients with uterine leiomyomas and myometrium of 20 healthy control subjects using single-voxel proton MR spectroscopy (point resolved spectroscopy technique, TE:136 ms). Voxels were placed at the center of the uterine leiomyomas. The peak areas of creatine, choline, lipid and lactate were determined. The MR spectroscopy results of uterine leiomyomas were compared with the spectroscopy results obtained from the myometrium of healthy control subjects. Results: The characteristically obtained signal was choline, which was detected not only in 14 of the 15 leiomyomas (93.3%) but also in 18 of the 20 myometrium of control subjects (90%). The lipid signals were determined in 9 of 15 patients with uterine leiomyomas (60%) and 8 of 20 control subjects (40%). The lactate signal was obtained from six of 15 patients with leiomyomas (40%) but only two of myometrium (10%). The creatine signal was obtained from 4 of 15 patients with leiomyomas (26.6%) and 5 of 20 myometrium (25%). Among the tested parameters only lactate peak was statistically significant (p < 0.05). Conclusion: Proton MR spectroscopic imaging may be helpful for the investigation of the underlying pathophysiology of uterine leiomyomas. The presence of lactate and lipid signals in the spectrum may be a useful indicator of metabolic pathway of uterine leiomyomas.

Serial cranial MR imaging and single voxel proton MR spectroscopy in paraneoplastic limbic encephalitis

We report the serial cranial MR imaging (MRI) and single voxel proton magnetic resonance spectroscopy ( 1 H -MRS) findings of the brain, at 3 and 11 weeks after the onset of symptoms in a patient with paraneoplastic limbic encephalitis (PLE) in association with anti-Hu antibodies. There was a suspiciously detectable hyperintensity in temporal lobes on initial MRI and increased myoinositol (mI) and minimally decreased N-acetylaspartate (NAA) levels were seen in 1 H -MRS from the right superior temporal neocortex. Follow-up cranial MRIs showed more striking hyperintensity in bilateral medial temporal regions on T2-weighted images. Repeat single voxel 1 H -MRS from the bilateral medial temporal region showed the lactate peak, prominent NAA decrease, both choline and mI increase. These findings provided suggestive evidence in vivo for neuronal loss and gliosis, even there may be inflammatory cell infiltration in the PLE brain. To our knowledge, this is the first description of single voxel 1 H -MRS findings associated with PLE.

Monitoring individual response to brain-tumour chemotherapy: proton MR spectroscopy in a patient with recurrent glioma after stereotactic radiotherapy.

Since antineoplastic activity varies, sensitive methods for individual assessment of efficacy are needed. We demonstrate the clinical value of MR spectroscopy in monitoring chemotherapy in a patient with recurrent glioma after stereotactic radiotherapy. Diagnostic imaging before and after chemotherapy included contrast-enhanced MRI, single-voxel proton MR spectroscopy ((1)H MRS), (1)H MR spectroscopic imaging ((1)H SI), and fluorodeoxyglucose (FDG) positron-emission tomography (PET). A significant decrease in choline signal intensity was observed 2 months after chemotherapy indicating tumour chemosensitivity, in line with tumour shrinkage on MRI and decreased uptake of FDG. Assessment of early response by MRS may help to improve treatment protocols in other patients.

In vivo single-voxel proton MR spectroscopy in the differentiation of high-grade gliomas and solitary metastases

AIM: To determine whether single-voxel proton magnetic resonance spectroscopy (1HMRS) could be used to differentiate gliomas from metastases on the basis of differences in metabolite levels in the different involved regions. MATERIALS AND METHODS: Twenty-two patients (age range from 32 to 62 years, with a median age of 46.7 years) with a solitary brain tumour (14 gliomas, eight metastases) underwent conventional, gadolinium-DTPA enhanced T1-weighted images, and 1HMRS before surgical resection. Spectra from the enhancing tumour, the peritumoural region, and normal brain were obtained from 1HMRS. A point resolved spectroscopy sequence was required for 1HMRS. The metabolites in the spectra include: N-acetylaspartate (NAA), choline (CHO), creatine compounds (CR), myo-inositol (MI), lactate (LAC), glutamate and glutamine (Glu-n). Relative concentrations of metabolites were related to the peak area, and expressed with reference to CR. Student's t-test was used to determine whether there was a statistically significant difference in relative metabolic ratios between high-grade gliomas and metastases. Meanwhile, 16 of all 22 patients were re-examined using magnetic resonance imaging (MRI) within 6 months of surgical resection. Recurrence was present in three patients (two gliomas, one metastasis). RESULTS: Of the 14 patients with gliomas, the peaks of NAA were reduced in three cases; the peaks of LAC, which were elevated, appeared as typical double-peaks in the peritumoural region in nine cases; the peaks of Glu-n, which were also elevated, had a zigzag appearance in seven cases. The peaks of MI were increased in the tumoural region in eight cases, and CHO levels were elevated in all 14 cases. Of the eight patients with metastases, Glu-n peaks in the tumoural region in three cases and CHO peaks in the tumoural region in four cases were elevated, respectively, while the peaks of CR were reduced in three cases, and the peaks of NAA were markedly reduced in four cases within the enhancing tumoural region. Elevated CHO levels (CHO-to-CR ratio was 4.98:1.46, 2.65:0.32) in both the tumoural and peritumoural regions of gliomas but not in the metastases (CHO-to-CR ratio was 1.37:0.92, 1.22:0.38), and elevated MI levels were present (MI-to-CR ratio was 1.67:0.35) within the enhancing foci of gliomas but not in the metastases (MI-to-CR ratio was 0.89:0.31). The difference was statistically significant ( p<0.01). Elevated Glu-n and lipid levels were present in all three patients with recurrences. CONCLUSION: 1HMRS is a useful method in the distinction of these two kinds of tumours. It may also may provide useful prognostic information.

Cerebellar metabolite alterations detected in vivo by proton MR spectroscopy.

The aim of our work was to evaluate the feasibility of in vivo single-voxel quantitative proton MR spectroscopy in order to identify possible alterations in the main metabolite concentrations due to some metabolic dysfunctions in the cerebellum of patients suffering from a particular form of migraine called "with aura." Measurements of metabolite levels in the cerebellum disclosed reduced choline values (normalized both to N-acetyl-aspartate and creatine) in the patient group with respect to the age-matched control group. Our interest in this pathology is motivated by the fact that there are no available specific biochemical markers for migraine characterization, and the current diagnostic only takes advantage of the medical history and the clinical examination.

Proton MR spectroscopy of cerebellitis

Single voxel proton MR spectroscopy ( 1H-MRS) of the vermis was obtained in two patients with cerebellitis. In the acute phase 1H-MRS revealed low N-acetyl-aspartate (NAA)/creatine (Cr) and NAA/choline (Cho) and normal Cho/Cr ratios. Decrease of the concentration of NAA was confirmed by quantitative analysis in one patient. The NAA/Cr and NAA/Cho ratios and NAA concentration were increased in 1H-MRS examinations obtained 10 and 24 months after the acute episode. 1H-MRS demonstrates reversible metabolite changes in cerebellitis.

In vivo single-voxel proton MR spectroscopy in brain lesions with ring-like enhancement.

It is often difficult to make a correct diagnosis of ring-like enhanced lesions on Gd-enhanced MR brain images. To differentiate these lesions using proton MR spectroscopy (1H-MRS), we retrospectively evaluated the correlation between the 1H-MR spectra and histopathological findings. We evaluated proton MR spectra obtained from the lesions in 45 patients, including metastasis (n = 19), glioblastoma (n = 10), radiation necrosis (n = 7), brain abscess (n = 5), and cerebral infarction (n = 4). The rate of misdiagnosis was found to be lowest at the threshold level of 2.48 for the (choline containing compounds)/(creatine and phosphocreatine) ratio (Cho/Cr) obtained from the whole lesions, which include the enhanced rim and the non-enhanced inner region. That is, the positively predictive values of a Cho/Cr greater than 2.48 for diagnosing metastasis or glioblastoma was 88.9 and 60.0%, respectively, and the positively predictive value of a Cho/Cr less than 2.48 for diagnosing radiation necrosis or cerebral infarction was 71.4 and 100%, respectively. For further differentiating between metastasis and glioblastoma, information about the presence and absence of an N-acetyl-aspartate (NAA) peak and lipid- or lactate-dominant peak was found to be useful. In 73.7% of metastasis cases a lipid-dominant peak was observed in the whole lesion without an NAA peak in the inner region, whereas the same pattern was observed in only 10% of the glioblastoma cases. Correlation with the histopathological findings showed that a high Cho signal is suggestive of neoplasm. Lipid signal in the non-enhanced central region was correlated to necrosis. Lactate signals were often observed in glioblastoma, abscess and sometimes metastasis, presumably reflecting the anaerobic glycolysis by the living cells in the ring-like enhanced rim. Single-voxel proton MR spectroscopy may serve as a potential tool to provide useful information of differentiation of ring-like enhanced lesions that cannot be diagnosed correctly using enhanced MR images alone.

The evaluation of human breast lesions with magnetic resonance imaging and proton magnetic resonance spectroscopy

MR spectroscopy (MRS) assists in lesion characterization and diagnosis when combined with magnetic resonance imaging (MRI). Cancerous lesions demonstrate elevated composite choline levels arising from increased cellular proliferation. Our study investigated if MR spectroscopy of the breast would be useful for characterizing benign and malignant lesions. Single voxel proton MR spectroscopy (MRS) was acquired as part of an MR imaging protocol in 38 patients referred upon surgical consultation. The MR spectra were read independently in a blinded fashion without the MR images by three spectroscopists. The MRI exam was interpreted in two settings: (a) as a clinical exam with detailed histories and results from previous imaging studies such as mammography or ultrasound included and (b) as a blinded study without prior histories or imaging results. Elevated choline levels were demonstrated by MRS in 19 of the 23 confirmed cancer patients. The sensitivity and specificity for determining malignancy from benign breast disease with MRS alone were 83 and 87%, respectively, while a blinded MRI review reported 95 and 86%, respectively. Proton MR spectroscopy provides a noninvasive, biochemical measure of metabolism. The technique can be performed in less than 10 min as part of an MRI examination. MRI in combination with MRS may improve the specificity of breast MR and thereby, influence patient treatment options. This may be particularly true with less experienced breast MRI readers. In exams where MRI and MRS agree, the additional confidence measure provided by MRS may influence the course of treatment.

Differentiation between high-grade glioma and metastatic brain tumor using single-voxel proton MR spectroscopy.

The purpose of this study was to clarify the efficacy of single-voxel proton magnetic resonance spectroscopy (MRS) in differentiating high-grade glioma from metastasis. Thirty-one high-grade gliomas (11 anaplastic gliomas and 20 glioblastomas) and 25 metastases were studied. Proton MRS was performed using point-resolved spectroscopy with echo times (TEs) of both 136 and 30 ms. The peaks for lipid were evaluated at short TE, and those for N-acetyl-aspartate (NAA), creatine (Cr), and choline-containing compounds (Cho) were assessed at long TE. All the tumors exhibited a strong Cho peak at long TE. Twenty-one of 25 metastases showed no definite Cr peak. The remaining 4 metastases showed NAA and Cr peaks; however, the presence of NAA and relatively high NAA/Cr ratio (1.58+/-0.56) indicated normal brain contamination. All the gliomas, except for a single glioblastoma, showed a Cr peak with (n=16) or without (n=14) NAA. At short TE all metastases and glioblastomas showed definite lipid or lipid/lactate mixture, but anaplastic gliomas showed no definite lipid signal. Intratumoral Cr suggests glioma. Absence of Cr indicates metastasis. Definite lipid signal indicates cellular necrosis in glioblastoma and metastasis, and no lipid signal may exclude metastases.

Altered white and gray matter metabolism in CADASIL: a proton MR spectroscopy and 1H-MRSI study.

Subcortical white matter hyperintensities (WMH) and small cystic lesions are the radiologic hallmark of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary angiopathy causing stroke in young adults. To further characterize the cerebral pathology in vivo we analyzed metabolite concentrations in normal and abnormal appearing brain tissue using single and multiple voxel proton MR spectroscopy (1H-MRS and 1H-MRSI). Twenty patients with CADASIL and 21 age-matched controls were studied with 1H-MRSI at the level of the centrum semiovale; short echo time 1H-MRS was performed in six patients (WMH) and 10 controls. LCModel fits were used to estimate absolute and relative concentrations of N:-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (Cr) within WMH, normal appearing white matter (NAWM), and cortical gray matter (GM) as well as myo-inositol (mI) and lactate in WMH. 1H-MRSI-Patients with CADASIL showed significantly reduced NAA, Cho, Cr, and total metabolite content (Met(tot)) in WMH and NAWM. Normalization to Met(tot) revealed that NAA/Met(tot) was reduced in all regions, whereas Cho and Cr were relatively elevated in WMH. Short echo time 1H-MRS showed decreased NAA, Cr, Met(tot), and NAA/Met(tot) and elevated mI/Met(tot) and lactate in WMH. Metabolite changes were larger in severely affected subjects. Rankin scores correlated negatively with NAA/Met(tot) (all regions) and NAA/Cho (WMH), and positively with Cho/Met(tot) (WMH) and Cr/Met(tot) (NAWM). Marked metabolic abnormalities were observed in abnormal and normal appearing white matter in patients with CADASIL. The findings suggest axonal injury, enlarged extracellular spaces, myelin loss, and gliosis. The cortical abnormalities may reflect structural damage or functional neuronal impairment secondary to white matter pathology. NAA reductions were correlated with clinical disability emphasizing the clinicopathologic relevance of axonal injury in CADASIL.

Single Voxel Proton MR Spectroscopy Methods and Applications in Neuropediatrics

The purpose of this contribution is to introduce quantitative single voxel proton MR spectroscopy of the human brain as an easy-to-use method for a noninvasive assessment of cellular composition and metabolism and to demonstrate its clinical potential in the field of neuropediatrics.The chosen approach transforms fully relaxed (TR = 6000 ms) short echo time (TE = 20 ms) proton MR spectra (STEAM localization sequence) into absolute metabolite concentrations by automatically fitting the raw data with a library of model spectra comprising all metabolites at known concentration (LCModel). The procedure includes total N-acetylaspartyl compounds as a marker for viable neuroaxonal tissue and myo-inositol as a purely glial constituent as well as total creatine, choline-containing compounds, glutamate and glutamine, and lactate.Extensive studies of brain disorders in childhood suggest the use of proton MRS as a promising tool for an in vivo histopathologic characterization of brain tissue. Typical metabolite patterns are observed for pathologic processes such as lactic acidosis, loss of functioning neurons, astrocytosis, myelin breakdown, or loss of oligodendrocytes. Examples deal with the diagnostic workup of enzyme deficiencies, demyelinating white matter diseases, and focal brain lesions.

Hippocampal and Neocortical Metabolite Ratio in Patients with Complex Partial Seizure: Short TE and Long TE Techniques Using Single Voxel Proton MR Spectroscopy

Purpose: To compare hippocampal and neocortical metabolite ratios using single-voxel proton MR spec-troscopy with different echo times in patients with complex partial seizure. Materials and Methods: Using a GE Signa 1.5 T scanner with STEAM and PRESS sequences, automated single voxel proton MRS was used to determine metabolite ratio differences in the hippocampus and neocortex of nine complex partial seizure patients [mesial temporal sclerosis (n=5), status epilepticus (n=1), tumor (n=1), cortical dysplasia (n=1), occipital lobe epilepsy (n=1)]. A total of 20 examinations were performed in the region of the hippocampus (n=17), temporal neocortex (n=1), and parieto-occipital gray matter (n=1). Voxel size range was 5.2 -17.4 . The calculated creatine (Cr) peak was employed as an internal reference and the relative ratio of N-acetylaspartate (NAA) and choline (Cho) was calculated for both short and long echo times using an automated PROBE/SV (GE Medical Systems) package. Each NAA/Cho ratio obtained using both PRESS and STEAM techniques was compared by means of statistical analysis (paired Student t-test). Results: Using PRESS (long TE, 272 ms), NAA/Cho ratios were successfully calculated in 16 of 20 examina-tions; in four this was not possible due to noise levels of the Cr and Cho peaks. Using STEAM (short TE, 30 ms) NAA/Cho ratios were successfully calculated in 19 of 20 examinations; in one, the Cho peak could not be mea-sured. Using PRESS and STEAM, mean and standard deviations for the NAA/Cho ratio were 1.22 0.50 and 1.16 0.36, respectively. There were no statistically significant differences in this ratio between the short and long TE method (p 0.01). Conclusion: In complex partial seizure patients, no significant metabolite differences were found between short and long echo times of single voxel proton MR spectroscopy. The metabolite ratio at different echo times can be reliably obtained using this simplified and automated PROBE/SV quantitation method.

Usefulness of Single Voxel Proton MR Spectroscopy in the Evaluation of Hippocampal Sclerosis

ObjectiveThe purpose of our study was to determine the ability of H-1 MR spectroscopy (MRS) to lateralize the lesion in patients with hippocampal sclerosis.Materials and MethodsTwenty healthy volunteers and 25 patients with intractable temporal lobe epilepsy whose MR imaging diagnosis was unilateral hippocampal sclerosis were included. This diagnosis was based on the presence of unilateral atrophy and/or high T2 signal intensity of the hippocampus. Single-voxel H-1 MRS was carried out on a 1.5-T unit using PRESS sequence (TE, 136 msec). Spectra were obtained from hippocampal areas bilaterally with volumes of interest (VOIs) of 6.0 cm3 and 2.25 cm3 in healthy volunteers, and of either 6.0 cm3 (n = 14) or 2.25 cm3 (n = 11) in patients. Metabolite ratios of NAA/Cho and NAA/Cr were calculated from relative peak height measurements. The capability of MRS to lateralize the lesion and to detect bilateral abnormalities was compared with MR imaging diagnosis as a standard of reference.ResultsIn healthy volunteers, NAA/Cho and NAA/Cr ratios were greater than 0.8 and 1.0, respectively. In patients, the mean values of these ratios were significantly lower on the lesion side than on the contralateral side, and lower than those of healthy volunteers (p < .05). The overall correct lateralization rate of MRS was 72% (18/25); this rate was lower with a VOI of 6.0 cm3 than of 2.25 cm3 (64% versus 82%, p < .05). Bilateral abnormalities on MRS were found in 24% (6/25) of cases.ConclusionAlthough its rate of correct lateralization is low, single-voxel H-1 MRS is a useful and promising diagnostic tool in the evaluation of hippocampal sclerosis, particularly for the detection of bilateral abnormalities. To improve the diagnostic accuracy of H-1 MRS, further investigation, including the use of a smaller VOI and measurement of the absolute amount of metabolites, are needed.

Clinical impact of MR spectroscopy when MR imaging is indeterminate for pediatric brain tumors.

We undertook this study to determine if single-voxel proton (hydrogen) MR spectroscopy could have clinical impact on the management of pediatric brain tumors when MR findings were indeterminate. Eleven children (mean age, 9 years) being examined for brain tumors underwent MR imaging that revealed indeterminate criteria of enhancement, mass effect, and prolonged T1 and T2 signal. MR spectroscopy was then used to distinguish radiation necrosis from tumor in one patient, differentiate residual tumor from scarring in two patients, document early treatment response in three patients, and discriminate benign from malignant masses in five patients. In 10 of the 11 patients, spectra were successfully acquired. Based on the chemical analysis of the indeterminate area shown on MR imaging, clinical impact was achieved in these 10 patients. Clinical impact included treatment modification in five patients, follow-up studies replacing further treatment in three patients, and tumor characterization in the remaining two patients. Confirmation was by histology in four patients and by follow-up MR imaging and MR spectroscopy for up to 30 months in the remaining six patients. When MR imaging is indeterminate in evaluating pediatric brain tumors, MR spectroscopy can provide objective neurochemical information, thereby altering treatment.