Hypoxia-ischemic encephalopathy in full-term neonate: correlation proton MR spectroscopy with MR imaging

INTRODUCTION: To evaluate 1H Magnetic Resonance Spectroscopy (1HMRS) in the diagnosis of hypoxia-ischemic encephalopathy (HIE) of full-term neonates correlated with Magnetic Resonance Imaging (MRI). MATERIALS AND METHODS: Thirty-eight cases of full-term neonates diagnosed as HIE clinically were selected to perform MRI and 1HMRS examination. The ages ranged from 7 to 17 days, with median age of 8.2 days. In which, 26 cases were followed up and/or MRI reexamined at 6 months of age or later. Eight healthy neonates, with no evidence of birth asphyxia, also underwent 1HMRS for comparison. SE sequences were used for routine MR examination; point resolved spectroscopy sequence was required for 1HMRS. The metabolites in the spectra includes: N-acetylaspartate (NAA), choline compounds (CHO), creatine compounds (CR), myo-inositol (MI), lactate (LAC), glutamate and glutamine (Glu-Gln). RESULTS: The peaks of NAA were fall in two cases; the peaks of LAC, which were elevated, appeared as typical double-peaks appearance in 26 cases; the peaks of Glu-Gln, which were also elevated, appeared as zigzag appearance in nine cases. The peaks of CR were decreased in 11 cases, while those of MI were increased in seven cases. Mild type of lesions was present on MRI in 12 cases whose LAC/CR ratio lower than 0.5; mild and moderate types of lesions were present in 15 cases whose LAC/CR ratio between 0.5 and 1.5. Whereas, nine cases of severe lesions and two cases of moderate lesions were present on MRI in 11 cases whose LAC/CR ratio greater than 1.5. Twenty-six of 38 cases were followed up and/or MRI reexamined after 6 months, in which, sequelae were present in 12 cases. Among them, eight cases of sequelae in nine cases whose LAC/CR ratio greater than 1.5 were present (account for 88.89%). CONCLUSION: 1HMRS plays an important role to diagnose and predict outcome of HIE.     

Choroidal hematoma and effusion: evaluation with MR imaging

To evaluate the usefulness of magnetic resonance (MR) imagining in the evaluation of choroidal pathologic conditions, the authors studied 15 patients with either choroidal hematoma or choroidal effusion with a 1.5-T MR imager. These two lesions were reliably distinguished from each other on the basis of MR findings. Choroidal hematomas appeared as lenticular-shaped masses in the wall of the eyeball, and signal intensity depended on the age of the hematoma. Choroidal effusions appeared as crescentic or ring-shaped areas of increased signal on both T1- and T2-weighted images in an anatomic distribution corresponding to the choroidal and suprachoroidal spaces.     

Prostate cancer: correlation of MR imaging and MR spectroscopy with pathologic findings after radiation therapy-initial experience

PURPOSE: To prospectively evaluate magnetic resonance (MR) imaging and MR spectroscopy for depiction of local prostate cancer recurrence after external-beam radiation therapy, with step-section pathologic findings as the standard of reference. MATERIALS AND METHODS: Study received institutional approval, and written informed consent was obtained. Study was compliant with Health Insurance Portability and Accountability Act. Sextant biopsy, digital rectal examination, MR imaging, MR spectroscopy, and salvage radical prostatectomy with step-section pathologic examination were performed in nine patients with increasing prostate-specific antigen levels after external-beam radiation therapy. MR imaging criterion for tumor was a focal nodular region of reduced signal intensity at T2-weighted imaging. MR spectroscopic criteria for tumor were voxels with choline (Cho) plus creatine (Cr) to citrate (Cit) ratio ([Cho + Cr]/Cit) of at least 0.5 or voxels with detectable Cho and no Cit in the peripheral zone. Sensitivity and specificity of sextant biopsy, digital rectal examination, MR imaging, and MR spectroscopy were determined by using a prostate sextant as the unit of analysis. For feature analysis, MR imaging and MR spectroscopic findings were correlated with step-section pathologic findings. RESULTS: MR imaging and MR spectroscopy showed estimated sensitivities of 68% and 77%, respectively, while sensitivities of biopsy and digital rectal examination were 48% and 16%, respectively. MR spectroscopy appears to be less specific (78%) than the other three tests, each of which had a specificity higher than 90%. MR spectroscopic feature analysis showed that a metabolically altered benign gland could be falsely identified as tumor by using MR spectroscopic criteria; further analysis of MR spectroscopic features did not lead to improved MR spectroscopic criteria for recurrent tumor. CONCLUSION: In summary, MR imaging and MR spectroscopy may be more sensitive than sextant biopsy and digital rectal examination for sextant localization of cancer recurrence after external-beam radiation therapy.     

Neuro-Behcet''s disease: diffusion MR imaging and proton MR spectroscopy

We herein report the case of a 53-year-old woman with Behcet's disease and an acute T2-hyperintense lesion in left side of the pons. Echo-planar "trace" diffusion MR imaging revealed high signal intensity changes at the lesion site on b = 1000 s/mm(2) images, initially suggesting restricted diffusion. On corresponding apparent diffusion coefficient maps, however, the lesion had high signal intensity and high apparent diffusion coefficient values (1.22 x 10(-3) mm(2)/s), compared with the contralateral normal side of the pons (0.86 x 10(-3) mm(2)/s) and compared with the normal temporal white matter (0.80 x 10(-3) mm(2)/s). This was consistent with the presence of increased diffusion, hence vasogenic edema. Proton MR spectroscopy excluded acute infarction. This particular pattern (high signal intensity on b = 1000 s/mm(2) images in association with high apparent diffusion coefficient values) likely represented the acute inflammatory process associated with disrupted brain-blood barrier in the fulminant form of neuro-Behcet's disease. Follow-up examinations 相似文献   

Marchiafava-Bignami disease: longitudinal MR imaging and MR spectroscopy study

A case of Marchiafava-Bignami disease was serially evaluated with MR imaging and MR spectroscopy at 1, 2, 4, and 11 months after the onset of symptoms. The first MR imaging study showed extensive abnormal signal intensity of the corpus callosum without macroscopic changes; a diagnosis of Marchiafava-Bignami disease was made, and vitamin therapy was initiated. Follow-up studies showed progressive reduction of signal intensity abnormalities and residual callosal atrophy. MR spectroscopy revealed progressive reduction of the N-acetylaspartate:creatine ratio, with partial recovery in the last study, and a normalization of the choline:creatine ratio, which was initially slightly increased. Lactate was detectable during the subacute phase and was replaced by lipids after 4 months. This study confirmed the role of MR imaging in diagnosing Marchiafava-Bignami disease and particularly the value of MR spectroscopy in focusing the pathogenesis of the disease, monitoring its evolution and changes related to therapy.     

MR imaging of liposarcomas: correlation of MR features and histology

The magnetic resonance (MR) imaging features of liposarcoma were correlated with histology in 15 patients. The MR findings for liposarcoma were not specific. The six myxoid liposarcomas and two atypical lipomatous tumors, however, had distinctive MR features, i.e., nodular masses of slightly heterogeneous intermediate to high signal intensity (SI), intermingled with high SI septa on T1-weighted images. The T2-weighted images demonstrated the relative reversal of these regional SI characteristics. Additionally, MR correctly identified the presence of fat in all eight cases in which it was pathologically present. The fat in two atypical lipomatous tumors was inseparable on MR from the subcutaneous fat. Magnetic resonance appears useful for preoperative staging and follow-up studies of liposarcomas. It may be helpful in identifying patients with myxoid liposarcoma and atypical lipomatous tumors who have longer survival times.     

Pantothenate kinase-associated neurodegeneration: MR imaging,proton MR spectroscopy,and diffusion MR imaging findings

We herein report the case of a 15-year-old male patient with pantothenate kinase-associated neurodegeneration. The classic "eye-of-the-tiger" appearance was initially present on the globus pallidi on T2-weighted MR images and had disappeared by the time of the 10-month follow-up examination. Fluid-attenuated inversion recovery images revealed marked hypointensity in the globus pallidi and dentate nuclei and high signal intensity changes in the deep cerebral white matter. Proton MR spectroscopy revealed markedly decreased N-acetylaspartate in the globus pallidi, associated with decreased N-acetylaspartate and increased myoinositol in the deep cerebral white matter. Diffusion MR images (b=1000 s/mm(2)) were negative (normal appearing) for deep cerebral white matter lesions, whereas apparent diffusion coefficient values were slightly increased (1.08-1.12 x 10(-3) mm(2)/s), compared with the apparent diffusion coefficient values from the normal white matter regions. Apparent diffusion coefficient values in the globus pallidi were lower than those in the unaffected thalamus.     

Thyroid masses: MR imaging and pathologic correlation

The authors explored the capability of high-field-strength surface coil magnetic resonance (MR) imaging in disclosing the gross pathologic characteristics of thyroid masses (especially pseudocapsular and hemorrhagic degeneration). Twenty-four patients were examined, including 12 with papillary carcinoma, eight with adenoma, and four with adenomatous goiter. All patients underwent surgery within 2 days after MR imaging. Specimens were cut and correlated directly with MR images. The appearance of the pseudocapsule was classified into four types: A, intact and even thickness around the tumor; B, only partially present or even absent; C, intact but with uneven thickness; D, partially destroyed by tumor. MR imaging findings corresponded precisely with those of gross pathologic examination in all cases but four of adenoma. Type A pseudocapsules were found only in adenoma and type D only in papillary carcinoma. Although the number of cases in the series was limited, the authors conclude that MR images reflect gross pathologic findings well and that some characteristic findings are suggestive of benign or malignant disease.     

Molecular imaging of cancer: MR spectroscopy and beyond

Proton magnetic resonance spectroscopic imaging is a non-invasive diagnostic tool for the investigation of cancer metabolism. As an adjunct to morphologic and dynamic magnetic resonance imaging, it is routinely used for the staging, assessment of treatment response, and therapy monitoring in brain, breast, and prostate cancer. Recently, its application was extended to other cancerous diseases, such as malignant soft-tissue tumours, gastrointestinal and gynecological cancers, as well as nodal metastasis. In this review, we discuss the current and evolving clinical applications of proton magnetic resonance spectroscopic imaging. In addition, we will briefly discuss other evolving techniques, such as phosphorus magnetic resonance spectroscopic imaging, sodium imaging and diffusion-weighted imaging in cancer assessment.     

MR imaging and MR spectroscopy in prostate cancer management

Currently, endorectal coil MR imaging has the ability to improve accuracy in staging of localized prostate cancer. The addition of MR spectroscopic imaging has further improved the sensitivity of MR imaging for intraprostatic tumor localization. Additional refinements and techniques are expected to further improve the performance of MR imaging for prostate cancer imaging and to aid in patient management. Further studies are required to identify the ideal role for MR imaging in the diagnosis and management of prostate cancer.     

MR imaging of thymoma: radiologic-pathologic correlation.

MR images in 17 patients with surgically proved thymomas (12 malignant and five benign) were reviewed and compared with pathologic specimens. In nine cases, MR images of excised specimens also were made and evaluated. On T2-weighted images, 11 of 12 malignant thymomas had an inhomogeneous signal intensity, half with and half without a lobulated internal architecture. None of the five benign thymomas had a lobulated internal architecture, and they all had a moderately or slightly inhomogeneous signal. Cystic regions and/or hemorrhage were noted pathologically, and corresponded to areas of inhomogeneous high signal intensity seen on T2-weighted images. Examination of the excised specimens in malignant thymomas showed that the lobulated configuration seen in the tumors was caused by thick fibrous septa. Our experience suggests that, although calcification cannot be identified, MR is helpful in making a differential diagnosis of mediastinal tumors and in determining malignancy of thymoma.     

MR imaging and MR spectroscopy in rhizomelic chondrodysplasia punctata

A case of rhizomelic chondrodysplasia punctata was investigated with MR imaging of the brain and hydrogen-1 MR spectroscopy of the brain and blood. Areas with abnormal signal hyperintensity on T2-weighted images or hypointensity on T1-weighted images were detected in the subcortical white matter. MR spectroscopy of the brain showed that normal-appearing white matter was characterized by increased levels of mobile lipids and myo-inositol, reduced levels of choline, and the presence of acetate. The importance of these metabolic anomalies is correlated to the deficiency in plasmalogen biosynthesis.     

Cerebral aspergillosis: MR imaging and histopathologic correlation.

The authors report a case of intracranial aspergillosis secondary to immunosuppression. Signal intensity changes in the lesion on brain MR are compared with gross and histopathologic findings at autopsy. A peripheral ring of low signal intensity relates to a dense population of Aspergillus hyphal elements and small areas of hemorrhage. CT findings are included for comparison.     

Low-grade glioma: correlation of short echo time 1H-MR spectroscopy with 23Na MR imaging

BACKGROUND AND PURPOSE: There is considerable variability in the clinical behavior and treatment response of low-grade (WHO grade II) gliomas. The purpose of this work was to characterize the metabolic profile of low-grade gliomas by using short echo time ¹H-MR spectroscopy and to correlate metabolite levels with MR imaging-measured sodium (²³Na) signal intensity. Based on previous studies, we hypothesized decreased N-acetylaspartate (NAA) and increased myo-inositol (mIns), choline (Cho), glutamate (Glu), and ²³Na signal intensity in glioma tissue.MATERIALS AND METHODS: Institutional ethics committee approval and informed consent were obtained for all of the subjects. Proton (¹H-MR) spectroscopy (TR/TE = 2200/46 ms) and sodium (²³Na) MR imaging were performed at 4T in 13 subjects (6 women and 7 men; mean age, 44 years) with suspected low-grade glioma. Absolute metabolite levels were quantified, and relative ²³Na levels were measured in low-grade glioma and compared with the contralateral side in the same patients. Two-sided Student t tests were used to test for statistical significance.RESULTS: Significant decreases were observed for NAA (P < .001) and Glu (P = .004), and increases were observed for mIns (P = .003), Cho (P = .025), and sodium signal intensity (P < .001) in low-grade glioma tissue. Significant correlations (r² > 0.25) were observed between NAA and Glu (P < .05) and between NAA and mIns (P < .01). Significant correlations were also observed between ²³Na signal intensity and NAA (P < .01) and between ²³Na signal intensity and Glu (P < .01). Ratios of NAA/mIns, NAA/²³Na, and NAA/Cho were altered in glioma tissue (P < .001); however based on the t statistic, NAA/²³Na (t = 9.6) was the most significant, followed by NAA/mIns (t = 6.1), and NAA/Cho (t = 5.0).CONCLUSION: Although Glu concentration is reduced and mIns concentration is elevated in low-grade glioma tissue, the NAA/²³Na ratio was the most sensitive indicator of pathologic tissue.

Low-grade (WHO grade II) gliomas, including astrocytoma, oligodendroglioma, and mixed glioma (oligoastrocytoma), account for 10%–20% of primary brain tumors in adults.¹ Although such tumors are more indolent than high-grade gliomas, there is considerable variability in their clinical behavior.² They are capable of malignant transformation and, ultimately, are almost universally fatal. Pathologically, these tumors are diffuse and infiltrative but lack such anaplastic features as necrosis, endothelial proliferation, and mitotic activity.³Tailoring treatment to the individual patient requires a better understanding of the factors that account for the variability in tumor behavior.^{4, 5} Currently, neither the appearance of a low-grade glioma on conventional MR imaging nor tumor pathology can completely predict future tumor behavior or response to treatment. Metabolic profiling of these tumors with MR spectroscopy has the potential to improve our ability to predict the biological behavior and treatment response of low-grade gliomas and to better delineate tumor boundaries. Previous in vitro and in vivo MR spectroscopy studies have identified metabolic markers that help noninvasively discriminate tumor type,^6–8 aid in radiation treatment planning,⁹ or predict survival.¹⁰ Most studies have used long echotime spectroscopy acquisitions (TE ≥ 130 ms), limiting tumor metabolite characterization to the dominant peaks in the ¹H spectrum: N-acetylaspartate (NAA; a putative marker of neuronal viability), total creatine (Cr; involved in energy metabolism), choline-containing compounds (Cho; associated with membrane breakdown/synthesis), and lactate (associated with anaerobic glycolysis). Typically, low-grade glioma is characterized by reduced NAA due to reduced neuronal attenuation, reduced Cr due to a hypermetabolic state, and increased Cho, reflecting increased membrane turnover.^{6, 8} The metabolites glutamate (Glu) and myo-inositol (mIns), measurable by shorter echotime ¹H-MR spectroscopy, may provide additional information about the pathologic state of the neoplasm. A previous study¹¹ has demonstrated that highly malignant tumors may release excess Glu to kill surrounding tissue and promote tumor growth, and increased Glu plus glutamine (Gln) has been measured previously in oligodendroglioma by ¹H-MR spectroscopy.¹² mIns activation of protein kinase C¹³ has also been associated with tumor malignancy. The limited use of short echotime ¹H-MR spectroscopy is due mainly to the difficulty in quantifying metabolites with complicated j-modulated spectral line shapes and the uncertainty introduced by less well-characterized macromolecule resonances beneath the metabolites of interest.Tumors may also be characterized by the local concentration of total sodium, which is sensitive to changes in the tumor microstructure.^14–16 For example, neoplastic cell proliferation and packing, cell death, and necrosis expand the extracellular space in tumors. A defective blood-brain barrier in tumors also permits water, electrolytes, and proteins to enter the extracellular space leading to vasogenic edema. Because both intracellular and extracellular sodium levels may be increased in tumors, ²³Na MR imaging represents a potentially sensitive and noninvasive means of monitoring tissue sodium content related to cancer pathology.^15–18The purpose of this study was to prospectively characterize the metabolic profile of low-grade gliomas by using ¹H-MR spectroscopy and to correlate metabolite levels with MR imaging-measured sodium signal intensity. Based on previous studies, it was hypothesized that levels of NAA would be reduced, and levels of Cho, mIns, Glu, and ²³Na signal intensity would be increased in low-grade glioma compared with normal tissue.     

Androgen sensitivity of rat prostate carcinoma studied by 31P NMR spectroscopy, 1H MR imaging, and 23Na MR imaging

31P NMR spectroscopy, 1H magnetic resonance (MR) imaging, and 23Na MR imaging were used to study the biochemical difference between nine hormone-sensitive and six hormone-resistant rat prostate cancers and to follow bioenergetic and morphologic changes subsequent to androgen deprivation in the hormone-sensitive model. Neither 1H nor 23Na MR image characteristics were useful in distinguishing androgen-sensitive from androgen-resistant prostate cancer nor in identifying androgen deprivation. 31P NMR spectroscopy did detect bioenergetic differences between the hormone-sensitive and hormone-resistant tumors. Baseline spectra showed a significantly higher PCr/ATP ratio (mean 0.86 +/- 0.09 SEM) for hormone-sensitive tumors than for hormone-resistant tumors (mean 0.26 +/- 0.07 SEM). By 3 days after androgen deprivation (orchiectomy (castration], PCr/ATP ratios had decreased noticeably; by 1 week, the decrease was statistically significant and remained so for the rest of the study (3 weeks). It appears that 31P NMR spectroscopy is useful in detecting androgen sensitivity of prostatic carcinoma.     

Experimental radiation injury: combined MR imaging and spectroscopy

A model of radiation injury to the brain was developed in the cat. Definite radiation changes were demonstrated at magnetic resonance (MR) imaging in four of six cats. These changes consisted of high-intensity abnormalities on images obtained with a long repetition time (TR) and a long echo time (TE), which were initially noted 208-285 days after irradiation. These changes were associated with gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) enhancement on short TR and inversion-recovery (IR) pulse sequences. Gd-DTPA enhancement and the high intensity on the long TR/TE images were identified at the same time and became more prominent throughout the study. Chemical-shift imaging and phosphorus spectroscopy demonstrated no notable changes despite clear-cut MR evidence of abnormalities. Sodium imaging was positive in one case. Correlation of MR and pathologic findings revealed areas of radiation necrosis and wallerian degeneration that corresponded to areas of Gd-DTPA enhancement on short TR and IR images and to areas of high intensity on long TR/TE images. Peripheral to the areas of Gd-DTPA enhancement were nonenhanced zones of high-signal-intensity abnormality on long TR/TE images, which represented regions of demyelination without necrosis. Gd-DTPA-enhanced proton imaging was the most sensitive method for detecting radiation damage in this animal model.