MR spectroscopy in post-treatment follow up of brain tumors

PurposeTo detect the role of MR spectroscopy in evaluating the whole area of signal alteration within the irradiated volume aiming to differentiate recurrent/residual tumors from radiation injury and to detect the tumor margin and extent.Materials and methodsThis prospective study included 25 patients with previously treated primary intracranial tumors. All patients received radiotherapy. MRI and multivoxel MRS were performed. The volume of interest was placed over the whole area of signal alteration. The spectra were analyzed for the signal intensity of choline (Cho), creatine (Cr), and N-acetyl aspartate (NAA), lipid (Lip), lactate (Lac), and myo-inositol (mI). Metabolite ratios for Cho/NAA, Cho/Cr, and NAA/Cr were calculated.ResultsCho/NAA and Cho/Cr were significantly higher while NAA/Cr ratios were significantly lower in tumors than radiation injury (p = 0.001 for all ratios). The Cho/NAA and Cho/Cr ratios were significantly higher in radiation injury than in normal-appearing brain tissue (p = 0.032 and p = 0.008, respectively), whereas NAA/Cr was insignificantly lower in radiation injury than normal-appearing brain tissue (p = 0.051). Value >1.8 for Cho/NAA ratio was considered as indicator for tumor.ConclusionMR spectroscopy can differentiate recurrent/residual tumor from radiation injury and delineate the tumor margin and extent.     

Differentiation between brain tumor recurrence and radiation injury using MR spectroscopy

OBJECTIVE: The purpose of our study was to explore the feasibility and utility of 2D chemical shift imaging (CSI) MR spectroscopy in the evaluation of new areas of contrast enhancement at the site of a previously treated brain neoplasm. MATERIALS AND METHODS: Two-dimensional CSI (point-resolved spectroscopy sequence [PRESS]; TR/TE, 1,500/144) was performed in 29 consecutive patients (4-54 years old; mean age, 34 years) who had a new contrast-enhancing lesion in the vicinity of a previously diagnosed and treated brain neoplasm. Clinical and imaging follow-up, and histopathology in 16 patients, were used as indicators of the identity of a lesion. RESULTS: Diagnostic-quality spectra were obtained in 97% of the patients. The Cho/Cr (choline/creatine) and Cho/NAA (choline/N-acetyl aspartate) ratios were significantly higher, and the NAA/Cr ratios significantly lower, in tumor than in radiation injury (all three differences, p < 0.0001). The Cho/Cr and Cho/NAA ratios were significantly higher in radiation injury than in normal-appearing white matter (p < 0.0003 and p < 0.0001, respectively), whereas NAA/Cr ratios were not different (p = 0.075). Mean Cho/Cr ratios were 2.52 for tumor, 1.57 for radiation injury, and 1.14 for normal-appearing white matter. Mean Cho/NAA ratios were 3.48, 1.31, 0.79, and mean NAA/Cr ratios were 0.79, 1.22, and 1.38, respectively. When values greater than 1.8 for either Cho/Cr or Cho/NAA ratios were considered evidence of tumor, 27 of 28 patients could be correctly classified. CONCLUSION: Two-dimensional CSI MR spectroscopy can differentiate tumor from radiation injury in patients with recurrent contrast-enhancing intracranial lesions. In these lesions, the Cho/NAA and Cho/Cr ratios may be the best numeric discriminators.     

Proton MR spectroscopy of delayed cerebral radiation in monkeys and humans after brachytherapy.

PURPOSETo determine whether radiation necrosis can be differentiated from residual/recurrent tumor by proton MR spectroscopy.METHODSWe studied the effects of interstitial brachytherapy on the brains of healthy monkeys and in humans with glioblastoma multiforme. The effects of radiation therapy on normal brain tissue in monkeys were assessed with sequential proton MR spectroscopic studies 1 week to 6 months after brachytherapy. Proton MR spectroscopy was also performed in five patients with residual/recurrent glioblastoma multiforme (three of whom had radiation necrosis after brachytherapy), seven patients with newly diagnosed untreated glioblastoma multiforme, and 16 healthy volunteers, who served as a control group.RESULTSIn monkeys, the ratio of N-acetylaspartate (NAA) to creatine-phosphocreatine (Cr) and the ratio of choline-containing compounds (Cho) to Cr of the reference point were significantly lower 1 week after brachytherapy than before treatment. The ratio of NAA to Cho of the irradiated area tended to be higher 1 week after brachytherapy than before irradiation. These peak metabolic ratios showed characteristic changes 6 months after treatment. In two of three monkeys, lipid signal was elevated 6 months after irradiation. In the clinical study, the ratio of NAA to Cho in the area of radiation necrosis was significantly different from that in glioblastoma multiforme when compared with the contralateral hemisphere after irradiation. In addition, lipid signal was detected in all patients with radiation necrosis.CONCLUSIONIt might be possible to use proton MR spectroscopy to differentiate radiation necrosis from residual/recurrent glioblastoma multiforme on the basis of comparisons with the contralateral hemisphere after radiation therapy.     

MR spectroscopy in the evaluation of recurrent contrast-enhancing lesions in the posterior fossa after tumor treatment

Recurrent contrast-enhancing lesions arising within foci of prior brain neoplasms treated with chemotherapy and/or radiation therapy pose a significant diagnostic dilemma, as they may represent recurrent or residual tumor, treatment-related changes, or a combination of both. Those lesions specifically in the posterior fossa are even more difficult to assess, given the technical limitations of 2D CSI in the infratentorial compartment. We explored the feasibility of 2D-CSI MR spectroscopy in the evaluation of recurrent contrast-enhancing lesions in eight consecutive patients who had undergone treatment for posterior fossa or brainstem tumors. Mean Cho/Cr (choline/creatine) ratios obtained by 2D-CSI in recurrent tumor, treatment-related changes, and normal white matter were 2.93, 1.62, and 0.97, respectively, mean Cho/NAA (choline/N-Acetyl aspartate) ratios were 4.34, 1.74, and 0.93, and mean NAA/Cr (N-acetyl aspartate/creatine) ratios were 0.74, 0.92, and 1.26, respectively. In conclusion, also in the posterior fossa, MR spectroscopy is likely to be useful as an adjunct to conventional imaging characteristics in distinguishing recurrent tumor from treatment-related changes, irrespectively of the MRS technique used. In most cases spectra of diagnostic quality can be obtained using 2D-CSI to include coverage of both the lesion and its vicinity.     

Human brain tumors: spectral patterns detected with localized H-1 MR spectroscopy.

Image-guided localized proton magnetic resonance (MR) spectroscopy of intracranial tumors was performed to correlate spectral patterns and histologic findings. Thirty-six patients were examined prior to any specific treatment. Evaluation based on signal intensity ratios showed that all tumor spectra differed from spectra of healthy brain tissue. Ratios of creatine to choline-containing compounds (Cr/Cho) and nitrogen acetyl-aspartate to Cho (NAA/Cho) were reduced significantly in all tumor spectra compared with spectra of normal tissue in contralateral brain hemispheres (P less than .005). Noncerebral tumors typically showed a vanishing or missing NAA signal, strongly reduced Cr signal, and additional signals, assigned to alanine in meningiomas and lipids in metastases. In contrast, 11 gliomas of grades 2 and 3 exhibited NAA/Cho ratios and Cr/Cho ratios that were less than normal but that were significantly larger (P less than .01) than corresponding values in eight meningiomas. Ten glioblastomas displayed spectra with various signal ratios, so no significant differences between them and other tumor types could be established. In nine gliomas a clearly detectable lactate signal was present. However, no direct correlation between lactate level and histologic tumor grading was found.     

Proton MR spectroscopy of pediatric cerebellar tumors.

PURPOSETo investigate the role of proton MR spectroscopy in pediatric cerebellar tumor diagnosis.METHODSSingle voxel pulse sequences with long echo time (135 or 270 milliseconds, voxel size 8 to 19 cm3), were used to obtain proton spectra of primary pediatric cerebellar tumors. Eleven primitive neuroectodermal tumors (patient age, 2 to 12 years; mean, 7 years), 11 low-grade astrocytomas (age, 2 to 16 years; mean, 9 years), 4 ependymomas (age, 1 to 6 years; mean, 4 years), 1 mixed glioma ependymo-astrocytoma (age, 11 years), 1 anaplastic ependymoma (age, 7 years), 1 ganglioglioma (age, 14 years), and 1 malignant teratoma (age, 6 days) were studied. Control cerebellum spectra were acquired from five patients without abnormality in cerebellum (age, 2 to 15 years; mean, 8 years). The signal intensities from choline-containing compounds (Cho), creatine/phosphocreatine (Cr), N-acetyl-aspartate (NAA), and lactate (Lac) were quantified. The mean and standard deviation of metabolite ratios were calculated.RESULTSThe control spectra ratios (NAA:Cho = 1.49 +/- 0.36, Cr:Cho = 1.13 +/- 0.23) were distinct from the tumor spectra (NAA:Cho = 0.41 +/- 0.27 and Cr:Cho = 0.37 +/- 0.23). Most of primitive neuroectodermal tumors had low NAA:Cho (0.17 +/- 0.09) and Cr:Cho (0.32 +/- 0.19). Compared with primitive neuroectodermal tumors, low-grade astrocytomas and ependymomas had higher NAA:Cho ratio (0.63 +/- 0.19 and 0.39 +/- 0.12). The Cr:Cho ratio was higher for ependymomas (0.60 +/- 0.20) than for astrocytomas (0.27 +/- 0.12) and primitive neuroectodermal tumors. No NAA was found in the malignant teratoma. Lac:Cho ratio was 0.66 +/- 0.40, 0.58 +/- 0.30, and 0.08 +/- 0.12 for astrocytoma, ependymoma, and primitive neuroectodermal tumor, respectively. Lactate was elevated in the mixed glioma ependymo-astrocytoma, ganglioglioma, and teratoma. The NAA and lactate signals were sometimes obscured by lipids in the spectra. Discriminant analysis was carried out using NAA:Cho and Cr:Cho ratios to differentiate the three major tumor types. The sensitivity/specificity values for diagnosing astrocytoma, ependymoma, and primitive neuroectodermal tumor were found to be 0.91/0.84, 0.75/0.92, and 0.82/0.89, respectively, based on this study.CONCLUSIONIn many cases, proton MR spectroscopy can be used to help differentiate cerebellar primitive neuroectodermal tumor, low-grade astrocytoma, and ependymoma.     

Deep gray matter structures in HIV infection: a proton MR spectroscopic study.

PURPOSETo evaluate the effects of human immunodeficiency virus (HIV) infection on proton metabolites in brain regions carrying the heaviest HIV load.METHODSWe used two-dimensional proton MR spectroscopy with a preselected volume at the level of the third ventricle to measure N-acetyl-aspartate (NAA) and metabolites containing choline (Cho), and creatine (Cr) in the basal ganglia of eight cognitively impaired subjects who were seropositive for HIV and eight control subjects who were seronegative for HIV. Results are expressed as metabolite ratios.RESULTSIn the thalamus and lenticular nuclei, NAA/Cr was not different between the two groups. NAA/Cho was decreased in both the thalamus and lenticular nuclei of the HIV-positive group compared with the HIV-negative group. Cho/Cr tended to be increased in both the thalamus and lenticular nuclei of the HIV-positive group.CONCLUSIONSThe findings suggest no NAA differences between groups, consistent with negligible neuron loss in the region of the brain that carries the heaviest HIV load. The trends toward increased Cho/Cr are consistent with histopathologic findings of infiltration of subcortical gray matter structures with foamy macrophages, microglia, and lymphocytes, or possibly with gliosis.     

Proton magnetic resonance spectroscopy of brain tumors correlated with pathology

RATIONALE AND OBJECTIVES: Evaluate proton magnetic resonance spectroscopy ((1)H-MRS) for assessing and grading brain tumors. MATERIALS AND METHODS: The research was done at Detroit Medical Center in a 1.5-T Siemens MR magnet using single-voxel or multivoxel MRS. This study consisted of 27 patients: 10 females and 17 males ages 22-83 years (average age 43.8). The data were recorded for three peaks-N-acetyl aspartate (NAA), choline (Cho), creatine (Cr)-which were used to calculate the ratios Cho/NAA and Cho/Cr. RESULTS: Abnormal spectra were seen in 25 patients and normal spectra in 2. In 16 patients with brain astrocytoma of various grades, the pathology grading was correlated with Cho/NAA and Cho/Cr. These values were 6.53 and 3.35 for nine patients with Grade 4 astrocytoma; 1.85 and 1.62 for three patients with Grade 3 astrocytoma; 2.21 and 1.50 for three patients with Grade 2 astrocytoma; and 1.45 and 1.49 for one patient with Grade 1 astrocytoma. The remaining nine patients with abnormal spectra were also correlated with pathology. CONCLUSION: MRS ratios can be used to differentiate malignant and nonmalignant lesions from normal brain tissue. In general, high-grade astrocytoma have higher Cho/NAA and Cho/Cr ratios compared with low-grade astrocytoma.     

Regional differences of in vivo proton MR spectroscopy in developing human brain

The purpose of this study was to clarify regional differences in proton MR spectroscopy (1H-MRS) in the developing human brain. Proton MR spectra were obtained from 24 infants aged 0 to 24 months old. Proton MR spectroscopy was performed on a 1.5 Tesla clinical MR unit using a 3D-chemical shift imaging sequence (3D-CSI). MR spectra obtained from voxels in frontal white matter and those in parietal white matter were compared. The NAA/Cho ratios of the frontal region were lower than those of the parietal region at birth but increased rapidly during the first six months of life. The rate of increase was reduced in the second year of life. In contrast, NAA/Cho ratios in paracentral areas were already high at birth but increased slowly through the first two years of life. Cho/Cr ratios of the frontal region were stable during the first year of life and started to decrease in the second year of life. In the parietal region, Cho/Cr ratios were decreased throughout infancy. Regional differences in 1H-MRS spectra were apparent during infancy, and these differences were suggested to reflect regional differences in the maturation of the developing human brain.     

Noninvasive evaluation of malignancy of brain tumors with proton MR spectroscopy.

PURPOSETo test clinical proton MR spectroscopy as a noninvasive method for predicting tumor malignancy.METHODSWater-suppressed single-voxel point resolved spectroscopy in the frontal white matter of 17 healthy volunteers and 25 patients with brain tumors yielded spectra with peaks of N-acetyl aspartate (NAA), choline-containing compounds (Cho), creatine/phosphocreatine (Cre), and lactate. These peak intensities were semiquantitated as a ratio to that of the external reference. The validity of the semiquantitation was first evaluated through phantom and volunteer experiments.RESULTSThe variation in measurements of the designated region in the volunteers was less than 10%. Normal ranges of NAA/reference, Cho/reference, and Cre/reference were 3.59 +/- 0.68, 1.96 +/- 0.66, and 1.53 +/- 0.64 (mean +/- SD), respectively. In 17 gliomas, the Cho/reference value in high-grade gliomas was significantly higher than in low-grade gliomas. Levels of NAA/reference were also significantly different in low-grade and high-grade malignancy. In eight meningiomas (four newly diagnosed and four recurrent), the level of Cho/reference was significantly higher in recurrent meningiomas than in normal white matter or in newly diagnosed meningiomas.CONCLUSIONSHigher grades of brain tumors in this study were associated with higher Cho/reference and lower NAA/reference values. These results suggest that clinical proton MR spectroscopy may help predict tumor malignancy.     

Infantile tuberous sclerosis changes in the brain: proton MR spectroscopy findings.

A parietal hamartoma of a three-month-old boy with tuberous sclerosis was studied with magnetic resonance (MR) imaging, and proton MR spectroscopy. MR spectra were obtained with the single-voxel PRESS (point resolved spectroscopy; TR = 1500 ms, TE = 135 ms) sequence, in a 8 cc region of interest. Apparently low NAA/Cho (0.28), and NAA/Cr (0.37) ratios were noted in the hamartoma, that could suggest a neoplasm. The lesion and the surrounding brain tissue were studied again after seven months with spectroscopic imaging using the chemical shift sequence (TR = 1500 ms. TE = 40 ms). This study revealed apparently improved NAA/Cho (2.63), NAA/Cr (2.13) ratios in the hamartoma compared to the initial examination at three months of age, excluding the possibility of a neoplasm.     

Proton MR spectroscopy of the brain in infants

Proton magnetic resonance spectroscopy (MRS) was used to study the brain of 2 normal and 15 abnormal infants aged from 33 weeks postmenstrual age (PMA) to 14 months postnatal age. Eleven of the infants were examined on at least two occasions. The principal clinical diagnoses in the abnormal infants were perinatal ischemic and hemorrhagic brain injury. All proton spectra demonstrated peaks that were assigned to N-acetylaspartate (NAA), choline containing compounds (Cho), and creatine plus phosphocreatine (Cr). The NAA/Cho and NAA/Cr ratios increased with age, while the Cho/Cr ratio decreased with age in the majority of infants. The NAA/Cho ratio was generally lower in abnormal infants, but the difference was not apparent before 40 weeks (PMA). This ratio was lowest in infants with the severest degree of neurological abnormality. Proton and phosphorus MRS was compared in seven infants. In those with severe brain lesions, early phosphorus spectra were abnormal. On follow-up the phosphorus spectra became normal, but the proton spectra showed persistently low NAA/Cho and NAA/Cr ratios. Proton MRS provides new information that may be complementary to phosphorus MRS in the diagnosis and monitoring of brain development in normal and neurologically damaged infants.     

Developmental delay in children: assessment with proton MR spectroscopy

BACKGROUND AND PURPOSE: The cause of developmental delay frequently is unknown, and clinicians and families can be frustrated by the lack of neuroimaging correlation especially when considering therapeutic options and long-term prognosis. We sought to determine if proton MR spectroscopy can depict abnormalities in patients with developmental delay who have structurally normal brain MR images. METHODS: Children with developmental delay who were older than 2 years (mean age, 5.0 years; range, 3.0-10.0 years) and those aged 2 years or younger (mean age, 1.5 years; range, 0.5-2.0 years) and age-matched control subjects for each patient group underwent brain MR imaging and proton MR spectroscopy. A point-resolved spectroscopy sequence (2000/144 [TR/TE]) was used. Voxels (8 cm(3)) were placed in the subcortical white matter of the frontal and parieto-occipital lobes bilaterally. N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were assessed. RESULTS: All patients had normal brain MR images. In children with developmental delay who were aged 2 years or younger, no statistically significant differences were detected in the NAA/Cr or Cho/Cr ratios compared with those of the control subjects. In children with developmental delay who were older than 2 years, decreases in the NAA/Cr ratio were observed in frontal (P <.001) and parieto-occipital (P <.017) subcortical white matter, and elevations in the Cho/Cr ratio were detected in the frontal (P <.24) and parieto-occipital (P <.002) subcortical white matter compared with age-matched control subjects. CONCLUSIONS: In children with developmental delay who are older than 2 years, proton MR spectroscopy depicted abnormalities in the NAA/Cr and Cho/Cr ratios. Proton MR spectroscopy should be performed as part of the neuroimaging evaluation of developmental delay. Further studies will be needed to determine if abnormalities detected with proton MR spectroscopy can be used as a diagnostic tool and neuroimaging marker to assess long-term functional outcome.     

Volumetric proton spectroscopic imaging of mild traumatic brain injury

BACKGROUND AND PURPOSE: Poor clinical outcomes without notable neuroimaging findings after mild traumatic brain injury (MTBI) suggest diffuse tissue damage and altered metabolism not observable with conventional MR imaging and CT. In this study, MTBI-associated metabolic changes were assessed over the entire brain by using volumetric proton MR spectroscopic imaging (MRSI) and the findings related to injury and outcome assessments. METHODS: Fourteen subjects with mild closed head injury (Glasgow Coma Scale [GCS] scores of 13-15) underwent structural MR imaging and proton MRSI at 1.5 T within 1 month of injury. Distributions of N-acetylaspartate (NAA), total creatine (Cr), and total choline (Cho) were mapped over a wide region of the brain, and metabolite ratios were calculated for 25 regions without MR imaging abnormalities. Results were compared with data from 13 control subjects. RESULTS: Significant changes (P <.05) were found for some, but not all, brain regions for the average values from all MTBI subjects, with reduced NAA/Cr, increased Cho/Cr, and reduced NAA/Cho. Global NAA/Cho obtained from the sum of all sampled regions in two subjects was significantly reduced. Metabolite ratios were not significantly correlated with GCS score at admission or Glasgow Outcome Scale (GOS) score at 6 months after injury, although they were weakly correlated with GOS score at discharge. CONCLUSION: These results show evidence of widespread metabolic changes following MTBI in regions that appear normal on diagnostic MR images. Although the association with injury assessment and outcome is weak, this preliminary study demonstrates the applicability of volumetric proton MRSI for evaluating diffuse injury associated with MTBI.     

Multivoxel proton MR spectroscopy and hemodynamic MR imaging of childhood brain tumors: preliminary observations.

PURPOSETo assess multivoxel proton MR spectroscopy combined with MR imaging and hemodynamic MR imaging in the evaluation of brain tumors in children and young adults.METHODSFifteen patients with brain tumors and 10 healthy children underwent MR imaging and MR spectroscopy on a 1.5-T system. Ten patients with tumors had both MR spectroscopy and hemodynamic MR imaging. MR spectroscopy data sets with 1 cm3 to 3.4 cm3 resolution were acquired within 8.5 minutes by using a point-resolved spectroscopic, chemical-shift imaging technique in two dimensions with volume preselection. MR imaging was performed using fast spin-echo techniques. Hemodynamic MR imaging data were acquired every 2.5 seconds at one anatomic level using a spoiled gradient-echo sequence during intravenous bolus administration of contrast material.RESULTSAssessment with multivoxel MR spectroscopy and hemodynamic MR imaging added about 30 minutes to the total MR examination time. Normal tissue exhibited spectral peaks from biologically significant compounds such as N-acetylaspartate (NAA), choline-containing compounds (Cho), and total creatine (tCr). Twelve biopsy-proved tumors exhibited prominent Cho, reduced NAA, variable tCr, and/or lactate or lipids, and two showed increased hemodynamic parameters. Three of the tumors treated with radiation did not reveal prominent levels of Cho. Tissue necrosis had no Cho, NAA, or tCr, and reduced hemodynamics.CONCLUSIONSPreliminary findings by MR spectroscopy combined with MR imaging and hemodynamic MR imaging suggest that regions of active tumor may be differentiated from areas of normal tissue and areas of necrosis. These findings may enable metabolic and hemodynamic characterization of childhood brain tumors as well as suggest their response to therapy.     

Computation of brain metabolite ratios in single-voxel proton MR spectroscopy: comparison between semiautomatic and automatic software

Purpose

Metabolite ratios are the measurements most commonly utilised for clinical applications of brain proton magnetic resonance spectroscopy (¹H-MRS) [1]. We evaluated the agreement between the metabolite ratios calculated with semiautomatic and automatic software.

Materials and methods

Two single-voxel spectra (3.375 ml) localised in the frontal grey matter (GM) and peritrigonal white matter (WM) were obtained in 20 healthy subjects by using a point-resolved proton spectroscopy sequence (PRESS, TE=144 ms). The spectra were processed using the semiautomatic software J-Magnetic Resonance User Interface (JMRUI) and the automatic software SpectroView. Agreement of the N-acetyl-aspartate (NAA)/creatine (Cr), NAA/choline (Cho) and Cho/Cr ratios calculated with the two methods was assessed by estimating the 95% limits of agreement (LAs) of the differences of the values obtained with the two software packages.

Results

Mean values and standard deviations of NAA/Cr, Cho/Cr and NAA/Cho (semiautomatic//automatic software) were 1.99±0.53//1.73±0.36, 1.13±0.40//1.04±0.33, 1.85±0.62//1.89±0.69 for the GM and 2.24±0.41//2.37±0.27, 0.96±0.17//1.13±0.15, 2.37±0.43//2.11±0.23 for the WM. The 95% LAs were wider for GM spectra and ranged between ?0.51, 0.17 for Cho/Cr in the WM and ?1.54, 1.47 for NAA/Cho in the GM.

Conclusions

The difference between brain metabolite ratios calculated with the two software packages is not negligible and reflects spectral quality.     

脑肿瘤治疗后磁共振质子波谱评价

目的：评估脑肿瘤手术后、放疗后的多体素^1H MRS的临床应用价值。方法：21例脑肿瘤手术后、放疗后行多体素^1H MRS检查。结果：^1H MRS显示脑肿瘤内Cho升高5例，其中4例手术证实为肿瘤复发，1例为胶质增生。放射治疗后肿瘤生长抑制。^1H MRS表现为Cho降低，NAA、Cr明显下降。放射性坏死^1H MRS表现为肿瘤坏死区出现乳酸-脂质峰。结论：^1H MRS可评估脑肿瘤术后复发和监测肿瘤放疗后的病理变化，是一种有价值的检查方法。     

~1H-MRS在脑胶质瘤诊断及分级中的应用

目的:分析脑胶质瘤的氢质子磁共振波谱(proton magnetic resonance spectroscopy,1H-MRS)表现及其临床意义;探讨脑胶质瘤的1H-MRS特点与其病理级别相关性。方法:搜集经临床手术、病理证实的脑胶质瘤38例,按照WHO分级(2000)标准分成两组:低级别脑胶质瘤组、高级别脑胶质瘤组。所有患者在术前行1H-MRS检查,均在MR非增强成像的基础上获得。使用GE Signa1.5T超导磁共振扫描仪,多体素扫描,点分辨选择波谱法,检测不同区域代谢物变化。结果:脑胶质瘤的1H-MRS表现:肌酸(Cr)无明显变化;N-乙酰天门冬氨酸(NAA)下降,胆碱(Cho)增高,变化的程度由肿瘤级别高低决定;低级别、高级别脑胶质瘤的肿瘤组织分别和对侧正常脑组织的NAA/Cr、Cho/Cr、NAA/Cho比值存在显著性差异(P<0.01);低级别脑胶质瘤和高级别脑胶质瘤的肿瘤组织的NAA/Cr、Cho/Cr、NAA/Cho比值有统计学意义(P<0.05),脑胶质瘤的NAA/Cho、Cho/Cr、NAA/Cr比值与病理级别相关。结论:1H-MRS与MRI相结合能提高脑胶质瘤术前诊断的准确性。1H-MRS可评价脑胶质瘤的分级,反映脑胶质瘤代谢特性以及肿瘤生长潜能。     

MRI and 2D-CSI MR spectroscopy of the brain in the evaluation of patients with acute onset of neuropsychiatric systemic lupus erythematosus

MRI and 2D-CSI spectroscopy were performed in eight patients with systemic lupus erythematosus who presented with acute onset of neuropsychiatric lupus (NP-SLE), and in seven normal controls to evaluate for differences in metabolic peaks and metabolic ratios between the two groups. Also, the interval change of the metabolic peaks and their ratios during treatment in the NP-SLE patient group was evaluated. Metabolic peaks for N-acetyl-aspartate (NAA), choline (Cho), creatine (Cr), and lactate/lipids (LL) and their ratios (NAA/Cr, NAA/Cho, Cho/Cr, LL/Cr) were determined at initial presentation and 3 and 6 months later. In the eight lupus patients compared to the seven normal controls, NAA/Cho ratios were lower at presentation (1.05 vs 1.25; p = 0.004) and decreased even further at the three month follow-up (0.92 vs 1.05; p = 0.008). In contrast, both Cho/Cr (1.42 vs 1.26; p = 0.026) and LL/Cr ratios (0.26 vs 0.19; p = 0.002) were higher in the lupus patients at presentation compared to the controls and did not significantly change at three and six months follow-up. The NAA/Cr ratios were lower in the lupus patients compared to the controls at presentation but the difference was not statistically significant. However, the mean NAA/Cr significantly decreased from the initial examination to the three month follow-up (1.42 vs 1.32; p = 0.049) but did not significantly change from the three to the six month follow-up examinations. The NAA/Cr, Cho/Cr, and NAA/Cho ratios varied significantly (p < 0.05, p < 0.05, p < 0.05, respectively) between the 17 different locations measured in the brain in all eight patients and seven controls. Both the NAA/Cr ratios and the Cho/Cr ratios were also significantly lower in the gray matter than in the white matter (p < 0.0001) in both patients and controls, whereas the LL/Cr and NAA/Cho ratios were not significantly different. In conclusion, 2D-CSI MR spectroscopy may be useful in the early detection of metabolic CNS changes in NP-SLE patients with acute onset of new neurological symptoms as well as in the follow-up after treatment to assess presence and changes in metabolic brain injury. However, although there are detectable differences between normal individuals and lupus patients it is currently unclear whether these relate to the acute episode. Future studies are needed comparing NP-SLE patients with active CNS involvement with those inactive disease.     

Metabolite concentrations in the developing brain estimated with proton MR spectroscopy

The purpose of the present study was to estimate absolute concentrations and relaxation time constants of metabolites that were detectable with proton magnetic resonance (MR) spectroscopy in the healthy preterm, term, and infant brain. Five MR spectra were recorded for each infant by using STEAM (stimulated-echo acquisition mode) sequences with different TEs and TRs. Water was used as an internal standard. The T1 of choline-containing compounds (Cho) and the T1 of phosphocreatine plus creatine (PCr+Cr) decreased. The T2 of the N-acetyl-L-aspartate (NAA) resonance increased, probably because of a relatively larger signal overlap with glutamate in the most immature brains. The concentration of NAA almost doubled, whereas the Cho concentration showed only a nonsignificant tendency to decrease; therefore, the well-known increase in the ratio of NAA to Cho appears to be due mostly to an increase in NAA concentration. The concentration of PCr+Cr increased rapidly and reached adolescent values at approximately 4 months of age.