Patterns of hepatic iron distribution in patients with chronically transfused thalassemia and sickle cell disease

Patients with sickle cell disease (SCD) appear to be at lower risk of endocrinopathies and cardiac dysfunction than those with thalassemia major (TM). Circulating redox active iron is lower in these patients, possibly due to increased systemic inflammation and circulating cytokines. Hepcidin synthesis is upregulated during chronic inflammation, reducing intestinal iron absorption and promoting retention of iron in the reticuloendothelial cells. Hence, we hypothesized that livers of patients with SCD would exhibit greater iron deposition in sinusoidal spaces relative to hepatocytes and less in portal tracts when compared to patients with TM. To test this hypothesis, iron scoring analysis was performed on 70 clinically indicated liver biopsy specimens from children and young adults with the two syndromes. Sinusoidal scores were lower in around 1 of 4 patients with TM but the relative iron loading in hepatocytes, and portal tracts was identical in both diseases. Sinusoidal iron burdens saturated at low hepatic iron concentration (HIC) while hepatocyte and portal iron depots increased proportionally to HIC. Liver fibrosis was increased in patients with TM regardless of their chronic hepatitis status. Overall, liver iron distribution was relatively insensitive to differences in disease type and to the presence or absence of hepatitis.

Metabolism of orthotopic mouse brain tumor models

We used magnetic resonance spectroscopy to determine whether orthotopic mouse brain tumors grown as xenografts in immunocompromised mice either from human brain tumor cells implanted immediately after surgery or from cultured human tumor lines show metabolic profiles comparable to those of the original tumors. Using a 7 T scanner, spectra were acquired from mice with a human atypical teratoid/rhabdoid tumor (AT/RT) either implanted directly from the surgical specimen or first grown in culture, directly implanted choroid plexus carcinoma (CPC), and two medulloblastoma cell lines. The results were compared with spectra from these same tumors or tumor types in patients and with controls. Metabolic variability of tumors from a single cell line was also evaluated using the medulloblastoma lines. The main metabolic features of human tumors were qualitatively replicated in xenografts. AT/RTs in mice exhibited choline, creatine, and myo-inositol levels comparable to those observed in the patient. As in patients, choline was prominent in experimental CPC. Tumors from a single cell line were comparable. Significant correlations were found with key metabolites in humans and mice; however, differences including lower lipids in the implanted AT/RTs than in patient spectra and taurine observed in all animal spectra were also noted. The causes of these dissimilarities warrant further investigation.

Histologic analysis of pediatric tonsil and adenoid specimens: is it really necessary?

OBJECTIVE

To evaluate the incidence of unexpected histologic findings in routine tonsillectomy and adenoidectomy specimens.

METHODS

A retrospective medical record review was performed at a tertiary care children's hospital. The pathology records of 2062 children who underwent tonsil or adenoid surgery were analyzed and the final histologic diagnosis was recorded.

RESULTS

Four unexpected histologic findings were found on routine tonsil and adenoid specimens. None were clinically significant. A review of the literature shows a very low rate (0.015%) of unexpected clinically significant diagnoses in pediatric adenotonsillectomy specimens.

CONCLUSIONS

Given rarity of unexpected clinically significant diagnoses in pediatric adenotonsillectomy specimens, the cost and effort of analyzing each specimen histologically is difficult to justify.

Completely intraosseous atretic meningocele

Atretic meningoceles are infrequent congenital malformations resulting from the herniation of meninges through a skull defect. All prior reported cases have had a subcutaneous component with or without an underlying osseous defect. We report the unusual case of a completely intraosseous atretic meningocele.

Aggressive variant of a papillary glioneuronal tumor. Report of 2 cases

Papillary glioneuronal tumors are a newly recognized type of brain neoplasm characterized by prominent pseudopapillary structures and glioneuronal elements. All prior cases have shown that these tumors have an indolent course. The authors present 2 patients with an aggressive variant of the tumor. The first patient had dissemination of her tumor and the second had local spreading. Therefore, the authors conclude that papillary glioneuronal tumors do not always behave in a strictly benign fashion.

Brainstem primitive neuroectodermal tumors (bstPNET): results of treatment with intensive induction chemotherapy followed by consolidative chemotherapy with autologous hematopoietic cell rescue

We have evaluated the response rate and survival utilizing intensified chemotherapy followed by myeloablative chemotherapy with autologous hematopoietic cell rescue (AuHCR) and adjuvant radiation therapy in six young children with newly diagnosed brainstem primitive neuroectodermal tumors (bstPNET). Following maximum surgical resection of the tumor, patients received high dose induction chemotherapy including vincristine, cisplatin, cyclophosphamide, and etoposide. Eligible patients received a single cycle of myeloablative chemotherapy followed by AuHCR. Two patients survive at least 32 months with stable disease. This approach provides an alternative for young patients with bstPNET who in prior reports have had a uniformly fatal prognosis.

Enterobacter sakazakii invades brain capillary endothelial cells, persists in human macrophages influencing cytokine secretion and induces severe brain pathology in the neonatal rat

Enterobacter sakazakii is an opportunistic pathogen associated with contaminated powdered infant formula and a rare cause of Gram-negative sepsis that can develop into meningitis and brain abscess formation in neonates. Bacterial pathogenesis remains to be fully elucidated. In this study, the host inflammatory response was evaluated following intracranial inoculation of Ent. sakazakii into infant rats. Infiltrating macrophages and neutrophils composed multiple inflammatory foci and contained phagocytosed bacteria. Several genotypically distinct Ent. sakazakii strains (16S cluster groups 1-4) were shown to invade rat capillary endothelial brain cells (rBCEC4) in vitro. Further, the persistence of Ent. sakazakii in macrophages varied between strains. The presence of putative sod genes and SOD activity may influence the survival of acidic conditions and macrophage oxidase and contribute to Ent. sakazakii intracellular persistence. The influence of macrophage uptake of Ent. sakazakii on immunoregulatory cytokine expression was assessed by ELISA. This demonstrated that the IL-10/IL-12 ratio is high after 24 h. This is suggestive of a type 2 immune response which is inefficient in fighting intracellular infections. These findings may help explain how the diversity in virulence traits among Ent. sakazakii isolates and an unsuccessful immune response contribute to the opportunistic nature of this infection.

A non-invasive, in vivo technique for monitoring vascular status of glioblastoma during angiogenesis

The growth of solid tumors dependent on the process of angiogenesis in which growth factors secreted by tumor and stromal cells promote endothelial cell proliferation, migration, and maturation. This process generates a tumor-specific vascular supply and enables small or dormant tumors to grow rapidly with exponential increases in tumor volume. Determination of tumor oxygenation at the microvascular level will provide important insight into tumor growth, angiogenesis, necrosis, and therapeutic response, and will facilitate to develop protocols for studying tumor behavior. A non-invasive multi-modality approach based on near infrared spectroscopy (NIRS) technique, namely: Steady State Diffuse Optical Spectroscopy (SSDOS) along with Magnetic Resonance Imaging (MRI) is applied for monitoring the concentration of oxyhemoglobin, deoxyhemoglobin and water within tumor region and for studying the vascular status of tumor and the patho-physiological changes that occur during angiogenesis. Since, the growth of solid tumors depends on the formation of new blood vessels, an association between intramural microvessel density (MVD) and tumor oxygenation is also investigated. The relative decrease in oxygenation value with tumor growth indicates that though blood vessels infiltrate and proliferate the tumor region, a hypoxic trend is clearly present.

Mutations in the MPV17 gene are responsible for rapidly progressive liver failure in infancy

MPV17 is a mitochondrial inner membrane protein of unknown function recently recognized as responsible for a mitochondrial DNA depletion syndrome. The aim of this study is to delineate the specific clinical, pathological, biochemical, and molecular features associated with mitochondrial DNA depletion due to MPV17 gene mutations. We report 4 cases from 3 ethnically diverse families with MPV17 mutations. Importantly, 2 of these cases presented with isolated liver failure during infancy without notable neurologic dysfunction.

CONCLUSION

We therefore propose that mutations in the MPV17 gene be considered in the course of evaluating the molecular etiology for isolated, rapidly progressive infantile hepatic failure.

A noninvasive multimodal technique to monitor brain tumor vascularization

Determination of tumor oxygenation at the microvascular level will provide important insight into tumor growth, angiogenesis, necrosis and therapeutic response and will facilitate to develop protocols for studying tumor behavior. The non-ionizing near infrared spectroscopy (NIRS) technique has the potential to differentiate lesion and hemoglobin dynamics; however, it has a limited spatial resolution. On the other hand, magnetic resonance imaging (MRI) has achieved high spatial resolution with excellent tissue discrimination but is more susceptible to limited ability to monitor the hemoglobin dynamics. In the present work, the vascular status and the pathophysiological changes that occur during tumor vascularization are studied in an orthotopic brain tumor model. A noninvasive multimodal approach based on the NIRS technique, namely steady state diffuse optical spectroscopy (SSDOS) along with MRI, is applied for monitoring the concentrations of oxyhemoglobin, deoxyhemoglobin and water within tumor region. The concentrations of oxyhemoglobin, deoxyhemoglobin and water within tumor vasculature are extracted at 15 discrete wavelengths in a spectral window of 675-780 nm. We found a direct correlation between tumor size, intratumoral microvessel density and tumor oxygenation. The relative decrease in tumor oxygenation with growth indicates that though blood vessels infiltrate and proliferate the tumor region, a hypoxic trend is clearly present.

Giant cell tumor of the skull in pediatric patients

Giant cell tumors of the bone are rare, locally aggressive lesions that primarily affect the epiphyses of long bones. These tumors can occur in the skull, principally in the sphenoid and temporal bones. Symptoms of these tumors depend on their site of origin but typically include headache, pain, visual field defects, and conductive hearing loss. Histologically, these tumors consist of three cell types: osteoclast-like multinucleated giant cells; round mononuclear cells resembling monocytes; and spindle-shaped, fibroblast-like stromal cells. Radiographically, the tumors appear osteolytic and radiolucent without a sclerotic border. These tumors typically present in the third to fourth decades of life and rarely occur in patients under 20 years of age. The small number of studies of giant cell tumors of the skull has focused on the adolescent and adult populations. The authors report two cases of giant cell tumors of the skull in pediatric patients. In the first case, a 2-year-old girl presented with swelling behind the right ear. In the second case, a 7-week-old girl presented with a mass within the external auditory canal. Both patients underwent metastatic workup and biopsy procedures before resection of the tumor. Both case reports contribute to the literature of giant cell tumors of the skull by describing this condition in pediatric patients. To the authors' knowledge, these cases represent the youngest two patients with giant cell tumors of the skull yet described.

A case of composite neuroblastoma composed of histologically and biologically distinct clones

We report a case of a 12-month-old girl with stage 3 neuroblastoma composed of 2 distinct clones in the adrenal primary tumor. One clone showed neuroblastoma, poorly differentiated subtype with a low mitosis-karyorrhexis index (favorable histology), and the other was neuroblastoma, poorly differentiated subtype with a high mitosis-karyorrhexis index (unfavorable histology), according to the International Neuroblastoma Pathology Classification. Fluorescent-labeled in-situ hybridization using the formalin-fixed, paraffin-embedded material showed that the MYCN oncogene was amplified in the latter clone but not in the former clone. Lymph nodes from ipsilateral and contralateral sides contained metastatic neuroblastoma of the latter clone. It is well documented that tumors in the Ganglioneuroblastoma, nodular (composite, Schwannian stroma-rich/stroma-dominant and stroma-poor) category are composite and composed of multiple clones. To our knowledge, however, this is the 1st case report of composite tumor with biologically favorable and unfavorable clones in the Neuroblastoma (Schwannian stroma-poor) category.

Unexpected myxopapillary ependymoma within a filum terminale tethering the spinal cord

We present a 9-month-old neurologically normal infant with cutaneous markers for a closed neural tube defect consisting of two sacral dimples and associated tuft of hair. Magnetic resonance imaging showed that her spinal cord was tethered at S2 and associated with a large syrinx. A myelotomy was performed to address the hydrosyringomyelia and the filum terminale resected to untether the spinal cord. Histopathologic examination of the filum terminale specimen revealed the presence of an unexpected myxopapillary ependymoma. The association of a myxopapillary ependymoma with a closed neural tube defect appears to be coincidental. This patient may have presented at some future date with a clinically symptomatic myxopapillary ependymoma. The presence of microscopic myxopapillary ependymoma cells in this infant's filum supports the concept that these tumors arise from embryonic rests of ependymal cells.

fliP influences Citrobacter koseri macrophage uptake, cytokine expression and brain abscess formation in the neonatal rat

Citrobacter koseri causes neonatal meningitis frequently complicated with multiple brain abscesses. During C. koseri central nervous system infection in the neonatal rat model, previous studies have documented many bacteria-filled macrophages within the neonatal rat brain and abscesses. Previous studies have also shown that C. koseri is taken up by, survives phagolysosomal fusion and replicates in macrophages in vitro and in vivo. In this study, in order to elucidate genetic and cellular factors contributing to C. koseri persistence, a combinatory technique of differential fluorescence induction and transposon mutagenesis was employed to isolate C. koseri genes induced while inside macrophages. Several banks of mutants were subjected to a series of enrichments to select for gfp : : transposon fusion into genes that are turned off in vitro but expressed when intracellular within macrophages. Further screening identified several mutants attenuated in their recovery from macrophages compared with the wild-type. A mutation within an Escherichia coli fliP homologue caused significant attenuation in uptake and hypervirulence in vivo, resulting in death within 24 h. Furthermore, analysis of the immunoregulatory interleukin (IL)-10/IL-12 cytokine response during infection suggested that C. koseri fliP expression may alter this response. A better understanding of the bacteria-macrophage interaction at the molecular level and its contribution to brain abscess formation will assist in developing preventative and therapeutic strategies.

In vivo testing of Renilla luciferase substrate analogs in an orthotopic murine model of human glioblastoma

In vivo bioluminescent imaging using cells expressing Renilla luciferase is becoming increasingly common. Hindrances to the more widespread use of Renilla luciferase are the high autoluminescence of its natural substrate, coelenterazine, in plasma, the relatively high absorbance by tissue of the light emitted by the enzyme-substrate reaction; rapid clearance of the substrate; and significant cost. These factors, save for the cost, which has its own limiting effect on use, can combine to reduce the sensitivity of in vivo assays utilizing this reporter system, and methods of increasing light output or decreasing autoluminescence could be of great benefit. A number of analogs of coelenterazine are being investigated may accomplish one or both of these goals. In this study that we report on the testing of two new substrate analogs, EnduRen and ViViren, manufactured by Promega Corporation, in an orthotopic murine model of human glioblastoma expressing Renilla luciferase. We have tested these analogs in this cell line both in vitro and in vivo, and find that the substrate viviren results in significantly greater light output than the natural substrate or the other analog EnduRen. This new substrate could be valuable for studies where greater sensitivity is important.

Quantitative short echo time 1H-MR spectroscopy of untreated pediatric brain tumors: preoperative diagnosis and characterization

PURPOSE

Our aims were to evaluate the metabolic profiles of pediatric brain tumors with short echo time (TE) MR spectroscopy and absolute quantitation of metabolite concentrations (in mmol/kg of tissue) and to describe metabolic features that distinguish individual tumor types and that may help to improve preoperative diagnosis of specific tumors.

METHODS

MR imaging examinations of 60 patients with untreated brain tumors (14 medulloblastomas, 5 anaplastic astrocytomas, 3 low-grade astrocytomas, 17 pilocytic astrocytomas, 4 anaplastic ependymomas, 5 ependymomas, 3 choroid plexus papillomas, 3 choroid plexus carcinomas, and 6 pineal germinomas) were reviewed. Single-voxel proton MR spectroscopy with a TE of 35 ms was performed and absolute metabolite concentrations were determined by using fully automated quantitation.

RESULTS

Taurine (Tau) was significantly elevated in medulloblastomas (P < .00001) compared with all other tumors pooled (All Other). Tau was also observed consistently, at lower concentration, in pineal germinomas. Creatine (Cr) was significantly reduced in pilocytic astrocytomas, distinguishing them from All Other (P < .000001). The MR spectra of choroid plexus papillomas exhibited low Cr (P < .01) concentrations; however, myoinositol was elevated (P < .01) and total choline (tCho) (P < .0001) was reduced relative to All Other. Choroid plexus carcinomas had low Cr (P < .01 versus All Other) and the lowest Cr/tCho ratio (P < .0001 versus All Other) among all tumors studied. Guanidinoacetate was reduced in low-grade astrocytomas and anaplastic astrocytomas (P < .00001) versus All Other, whereas ependymoma and anaplastic ependymomas exhibited particularly low N-acetylaspartate (P < .00001 versus All Other).

CONCLUSION

Quantitative proton MR spectroscopy reveals features of pediatric brain tumors that are likely to improve preoperative diagnoses.

Cobalamin C disease presenting with hemophagocytic lymphohistiocytosis

Cobalamin C disease is a rare genetic condition resulting in methylmalonic aciduria, homocystinuria, and hematologic abnormalities. Clinical characteristics include ophthalmologic findings and neurological abnormalities, such as microcephaly, seizure, and mental retardation. The authors report on a 4-month-old patient initially diagnosed with hemophagocytic lymphohistiocytosis (HLH), who was later diagnosed with cobalamin C disease.

Untreated pediatric primitive neuroectodermal tumor in vivo: quantitation of taurine with MR spectroscopy

PURPOSE

To retrospectively investigate whether quantitation of taurine (Tau) concentrations with proton magnetic resonance (MR) spectroscopy in vivo improves the differentiation of primitive neuroectodermal tumors (PNET) from other common brain tumors in pediatric patients.

MATERIALS AND METHODS

The institutional review board approved this review of clinical data; it was not necessary to obtain parental consent. This study was HIPAA compliant. Single-voxel proton spectroscopy was added to the preoperative MR imaging work-up of 29 patients (12 boys and 17 girls; mean age, 6.5 years +/- 3.5) with untreated brain tumors; 13 had PNETs, and 16 had other tumors. Absolute concentrations (measured in millimoles per kilogram of brain tissue) of metabolites of the proton spectrum were determined. Student t tests were used for statistical comparisons.

RESULTS

Elevated absolute Tau concentration proved to be the most significant metabolite in the differentiation of PNETs from other tumors (6.09 mmol/kg +/- 2.24 vs 0.76 mmol/kg +/- 0.95, P < .001). PNETs also exhibited a higher ratio of Tau relative to choline (1.21 +/- 0.48 vs 0.28 +/- 0.39, P < .001), a higher ratio of Tau relative to creatine (1.28 +/- 0.44 vs 0.38 +/- 0.67, P < .001), a reduced a ratio of N-acetyl-aspartate relative to choline (0.20 +/- 0.20 vs 0.79 +/- 0.56, P < .001), and an increased choline concentration (5.30 mmol/kg +/- 1.64 vs 3.08 mmol/kg +/- 2.53, P < .05). Tau concentrations ranged from 2.62 to 11.15 mmol/kg in individual patients with a PNET.

CONCLUSION

Single-voxel quantitative (1)H MR spectroscopy performed in patients with untreated pediatric brain tumors showed that the Tau concentration was significantly elevated in PNETs and was useful in the differentiation of PNETs from other tumors.

Synchronous Multicentric Pleomorphic Xanthoastrocytoma: Case Report

OBJECTIVE AND IMPORTANCE:

Pleomorphic xanthoastrocytoma (PXA) is a rare, low-grade astrocytoma of adolescence. Relatively favorable outcomes have been achieved with complete surgical resection. However, few data exist regarding the treatment of recurrent, deep-seated, or multicentric lesions. We report the first case to our knowledge of synchronous multicentric PXA and discuss the related therapeutic challenges.

CLINICAL PRESENTATION:

A 13-year-old Hispanic girl presented with a 1-year history of progressive headaches, polyuria, and generalized fatigue. Findings from the neurological examination were notable only for the presence of papilledema. Results of laboratory studies revealed diabetes insipidus and hypothyroidism. The magnetic resonance imaging study revealed numerous nodular, homogeneously enhancing lesions, approximately 1 cm in size, scattered throughout both cerebral hemispheres.

INTERVENTION:

A right frontal craniotomy was performed for excisional biopsy of a superficial lesion beneath the coronal suture. Results of the histological examination were consistent with a diagnosis of PXA. The patient was treated with whole-brain radiation of 3600 cGy, with additional intensity-modulated boosts to the enhancing lesions of 1440 cGy. Three years after treatment, the patient remains neurologically nonfocal and shows no evidence of disease progression. Surgical intervention will be considered if accessible lesions progress in size on later imaging studies.

CONCLUSION:

Synchronous multicentric PXA presents unique challenges in that gross total resection would impose significant surgical morbidity; histological homogeneity among the lesions cannot be confirmed; and the well-described potential for anaplastic transformation may be increased with multiple lesions. The optimal treatment for patients with this rare and challenging diagnosis awaits further study.

Differentiation of choroid plexus tumors by advanced magnetic resonance spectroscopy

OBJECT

The management of pediatric intraventricular tumors is highly dependent on identification of the tumor type. Choroid plexus papillomas, a common intraventricular tumor in children, can be difficult to distinguish radiographically from choroid plexus carcinomas and other common pediatric central nervous system (CNS) tumors. In this study to overcome the limitations of current noninvasive imaging modalities, the authors use novel magnetic resonance (MR) spectroscopy techniques in vivo to elucidate the identifying biochemical features of choroid plexus tumors that may facilitate diagnosis and treatment.

METHODS

Based on an Internal Review Board-approved protocol, six children with newly diagnosed, untreated intraventricular brain tumors were identified. On retrospective review, this series included three choroid plexus papillomas and three choroid plexus carcinomas. Single-voxel proton MR spectroscopy with a short echo time was performed, and absolute metabolite concentrations (in mmol/kg) were determined using fully automated quantitation. These results were compared with MR spectroscopy profiles obtained in 54 other untreated CNS neoplasms in children. The myo-inositol (mI) level was significantly higher in choroid plexus papillomas (> 10 mmol/kg), uniquely distinguishing these tumors from choroid plexus carcinomas and all other tumors. Choroid plexus carcinomas, on the other hand, had significantly elevated levels of choline when compared with choroid plexus papillomas.

CONCLUSIONS

In this study the authors find that mI is a biochemical constituent that uniquely identifies choroid plexus papillomas and can be used as a noninvasive means of diagnosis and for follow-up evaluations in patients with this disease.

Differentiation of choroid plexus tumors by advanced magnetic resonance spectroscopy

Object

The management of pediatric intraventricular tumors is highly dependent on identification of the tumor type. Choroid plexus papillomas, a common intraventricular tumor in children, can be difficult to distinguish radiographically from choroid plexus carcinomas and other common pediatric central nervous system (CNS) tumors. In this study to overcome the limitations of current noninvasive imaging modalities, the authors use novel magnetic resonance (MR) spectroscopy techniques in vivo to elucidate the identifying biochemical features of choroid plexus tumors that may facilitate diagnosis and treatment.

Methods

Based on an Internal Review Board–approved protocol, six children with newly diagnosed, untreated intraventricular brain tumors were identified. On retrospective review, this series included three choroid plexus papillomas and three choroid plexus carcinomas. Single-voxel proton MR spectroscopy with a short echo time was performed, and absolute metabolite concentrations (in mmol/kg) were determined using fully automated quantitation. These results were compared with MR spectroscopy profiles obtained in 54 other untreated CNS neoplasms in children.

The myo-inositol (mI) level was significantly higher in choroid plexus papillomas (> 10 mmol/kg), uniquely distinguishing these tumors from choroid plexus carcinomas and all other tumors. Choroid plexus carcinomas, on the other hand, had significantly elevated levels of choline when compared with choroid plexus papillomas.

Conclusions

In this study the authors find that mI is a biochemical constituent that uniquely identifies choroid plexus papillomas and can be used as a noninvasive means of diagnosis and for follow-up evaluations in patients with this disease.

Proton-decoupled 31P MRS in untreated pediatric brain tumors

Proton-decoupled (31)P and (1)H MRS was used to quantify markers of membrane synthesis and breakdown in eight pediatric patients with untreated brain tumors and in six controls. Quantitation of these compounds in vivo in humans may provide important indicators for tumor growth and malignancy, tumor classification, and provide prognostic information. The ratios of phosphoethanolamine to glycerophosphoethanolamine (PE/GPE) and phosphocholine to glycerophosphocholine (PC/GPC) were significantly higher in primitive neuroectodermal tumors (PNET) (16.30 +/- 5.73 and 2.97 +/- 0.93) when compared with controls (3.42 +/- 1.62, P < 0.0001 and 0.45 +/- 0.13, P < 0.0001) and with other tumors (3.93 +/- 3.42, P < 0.001 and 0.65 +/- 0.30, P < 0.0001). Mean PC/PE was elevated in tumors relative to controls (0.48 +/- 0.11 versus 0.24 +/- 0.05, P < 0.001), but there was no difference between PNET and other tumors. Total choline concentration determined with quantitative (1)H MRS was significantly elevated (4.78 +/- 3.33 versus 1.73 +/- 0.56 mmol/kg, P < 0.05), whereas creatine was reduced in tumors (4.89 +/- 1.83 versus 8.28 +/- 1.50 mmol/kg, P < 0.05). A quantitative comparison of total phosphorylated cholines (PC+GPC)/ATP measured with (31)P MRS and total choline measured with (1)H MRS showed that in tumors a large fraction of the choline signal (>54 +/- 36%) was not accounted for by PC and GPC. The fraction of unaccounted choline was particularly large in PNET (>78 +/- 7%). The pH of tumor tissue was higher than the pH of normal brain tissue (7.06 +/- 0.03 versus. 6.98 +/- 0.03, P < 0.001).