Temporal and spatial development of axonal maturation and myelination of white matter in the developing brain

BACKGROUND AND PURPOSE

Diffusion tensor imaging (DTI) has been widely used to investigate the development of white matter (WM). However, information about this development in healthy children younger than 2 years of age is lacking, and most previous studies have only measured fractional anisotropy (FA). This study used FA and radial and axonal diffusivities in children younger than 2 years of age, aiming to determine the temporal and spatial development of axonal maturation and myelination of WM in healthy children.

MATERIALS AND METHODS

A total of 60 healthy pediatric subjects were imaged by using a 3T MR imaging scanner. They were divided into 3 groups: 20 at 3 weeks, 20 at 1 year of age, and 20 at 2 years of age. All subjects were imaged asleep without sedation. FA and axial and radial diffusivities were obtained. Eight regions of interest were defined, including both central and peripheral WM for measuring diffusion parameters.

RESULTS

A significant elevation in FA (P < .0001) and a reduction in axial and radial diffusivities (P < .0001) were observed from 22 days to 1 year of age, whereas only radial diffusivity showed significant changes (P = .0014) from 1 to 2 years of age. The region-of-interest analysis revealed that FA alone may not depict the underlying biologic underpinnings of WM development, whereas directional diffusivities provide more insights into the development of WM. Finally, the spatial development of WM begins from the central to the peripheral WM and from the occipital to the frontal lobes.

CONCLUSIONS

With both FA and directional diffusivities, our results demonstrate the temporal and spatial development of WM in healthy children younger than 2 years of age.

Functional connectivity MR imaging reveals cortical functional connectivity in the developing brain

BACKGROUND AND PURPOSE

Unlike conventional functional MR imaging where external sensory/cognitive paradigms are needed to specifically activate different regions of the brain, resting functional connectivity MR imaging acquires images in the absence of cognitive demands (a resting condition) and detects brain regions, which are highly temporally correlated. Therefore, resting functional MR imaging is highly suited for the study of brain functional development in pediatric subjects. This study aimed to determine the temporal and spatial patterns of rfc in healthy pediatric subjects between 2 weeks and 2 years of age.

MATERIALS AND METHODS

Rfc studies were performed on 85 children: 38 neonates (2-4 weeks of age), 26 one-year-olds, and 21 two-year-olds. All subjects were imaged while asleep; no sedation was used. Six regions of interest were chosen, including the primary motor, sensory, and visual cortices in each hemisphere. Mean signal intensity of each region of interest was used to perform correlation analysis pixel by pixel throughout the entire brain, identifying regions with high temporal correlation.

RESULTS

Functional connectivity was observed in all subjects in the sensorimotor and visual areas. The percent brain volume exhibiting rfc and the strength of rfc continued to increase from 2 weeks to 2 years. The growth trajectories of the percent brain volume of rfc appeared to differ between the sensorimotor and visual areas, whereas the z-score was similar. The percent brain volume of rfc in the sensorimotor area was significantly larger than that in the visual area for subjects 2 weeks of age (P = .008) and 1-year-olds (P = .017) but not for the 2-year-olds.

CONCLUSIONS

These findings suggest that rfc in the sensorimotor precedes that in the visual area from 2 weeks to 1 year but becomes comparable at 2 years. In contrast, the comparable z-score values between the sensorimotor and visual areas for all age groups suggest a disassociation between percent brain volume and the strength of cortical rfc.

Blood vessel morphologic changes depicted with MR angiography during treatment of brain metastases: a feasibility study

PURPOSE

To prospectively determine if magnetic resonance (MR) angiography can depict intracranial vascular morphologic changes during treatment of brain metastases from breast cancer and if serial quantitative vessel tortuosity measurements can be used to predict tumor treatment response sooner than traditional methods.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Twenty-two women aged 31-61 years underwent brain MR angiography prior to and 2 months after initiation of lapatinib therapy for brain metastases from breast cancer. Vessels were extracted from MR angiograms with a computer program. Changes in vessel number, radius, and tortuosity were calculated mathematically, normalized with values obtained in 34 healthy control subjects (19 women, 15 men; age range, 19-72 years), and compared with subsequent assessments of tumor volume and clinical course.

RESULTS

All patients exhibited abnormal vessel tortuosity at baseline. Nineteen (86%) patients did not exhibit improvement in vessel tortuosity at 2-month follow-up, and all patients demonstrated tumor growth at 4-month follow-up. Vessel tortuosity measurements enabled us to correctly predict treatment failure 1-2 months earlier than did traditional methods. Three (14%) patients had quantitative improvement in vessel tortuosity at 2-month follow-up, with drop out of small abnormal vessels and straightening of large vessels. Each of the two patients for whom further follow-up data were available responded to treatment for more than 6 months.

CONCLUSION

Study results established the feasibility of using MR angiography to quantify vessel shape changes during therapy. Although further research is required, results suggest that changes in vessel tortuosity might enable early prediction of tumor treatment response.

Early postnatal development of corpus callosum and corticospinal white matter assessed with quantitative tractography

BACKGROUND AND PURPOSE

The early postnatal period is perhaps the most dynamic phase of white matter development. We hypothesized that the early postnatal development of the corpus callosum and corticospinal tracts could be studied in unsedated healthy neonates by using novel approaches to diffusion tensor imaging (DTI) and quantitative tractography.

MATERIALS AND METHODS

Isotropic 2 x 2 x 2 mm(3) DTI and structural images were acquired from 47 healthy neonates. DTI and structural images were coregistered and fractional anisotropy (FA), mean diffusivity (MD), and normalized T1-weighted (T1W) and T2-weighted (T2W) signal intensities were determined in central midline and peripheral cortical regions of the white matter tracts of the genu and splenium of the corpus callosum and the central midbrain and peripheral cortical regions of the corticospinal tracts by using quantitative tractography.

RESULTS

We observed that central regions exhibited lower MD, higher FA values, higher T1W intensity, and lower T2W intensity than peripheral cortical regions. As expected, MD decreased, FA increased, and T2W signal intensity decreased with increasing age in the genu and corticospinal tract, whereas there was no significant change in T1W signal intensity. The central midline region of the splenium fiber tract has a unique pattern, with no change in MD, FA, or T2W signal intensity with age, suggesting different growth trajectory compared with the other tracts. FA seems to be more dependent on tract organization, whereas MD seems to be more sensitive to myelination.

CONCLUSIONS

Our novel approach may detect small regional differences and age-related changes in the corpus callosum and corticospinal white matter tracts in unsedated healthy neonates and may be used for future studies of pediatric brain disorders that affect developing white matter.

A review of micro- and macrovascular analyses in the assessment of tumor-associated vasculature as visualized by MR

There is currently no noninvasive, reliable method of assessing brain tumor malignancy or of monitoring tumor treatment response. Monitoring changes to tumor vasculature might provide an effective means of assessing both tumor aggressiveness and treatment efficacy. To date, most such research has concentrated upon tumor "microvascular" imaging, with permeability and/or perfusion imaging used to assess vessel changes at the subvoxel level. An alternative approach assesses tumor vasculature at the "macroscopic" level, calculating the numbers and shapes of the larger vessels discriminable by magnetic resonance angiography. This paper provides an overview of magnetic resonance (MR) vascular imaging at both the microscopic (dynamic MR perfusion and permeability) and macroscopic (MR angiographic) levels. The two approaches provide different, complementary information and together could provide important insights into cancer growth as well as new methods of assessing malignancy and tumor treatment response.

Tumor therapeutic response and vessel tortuosity: preliminary report in metastatic breast cancer

No current non-invasive method is capable of assessing the efficacy of brain tumor therapy early during treatment. We outline an approach that evaluates tumor activity via statistical analysis of vessel shape using vessels segmented from MRA. This report is the first to describe the changes in vessel shape that occur during treatment of metastatic brain tumors as assessed by sequential MRA. In this preliminary study of 16 patients undergoing treatment for metastatic breast cancer we conclude that vessel shape may predict tumor response several months in advance of traditional methods.

Utility of navigator-prospective acquisition correction technique (PACE) for reducing motion in brain MR imaging studies

In this retrospective review, we demonstrate the utility of using a commercially available gated navigator sequence (prospective acquisition correction technique [PACE]) to reduce rhythmic breathing motion on brain MR images. For purposes of this report, we studied 2 sedated patients who had marked head rocking, one due to deep breathing and snoring and the other due to ventilator support. Motion degraded the routine images, which, despite a short acquisition time, were nondiagnostic. After application of PACE, a technique commonly used in abdominal studies, the brain images in both patients were judged to be of acceptable diagnostic quality. The use of PACE to diminish head motion is now routine at our institution when sedated or ventilated patients degrade images with involuntary head rocking.

Regional gray matter growth, sexual dimorphism, and cerebral asymmetry in the neonatal brain

Although there has been recent interest in the study of childhood and adolescent brain development, very little is known about normal brain development in the first few months of life. In older children, there are regional differences in cortical gray matter development, whereas cortical gray and white matter growth after birth has not been studied to a great extent. The adult human brain is also characterized by cerebral asymmetries and sexual dimorphisms, although very little is known about how these asymmetries and dimorphisms develop. We used magnetic resonance imaging and an automatic segmentation methodology to study brain structure in 74 neonates in the first few weeks after birth. We found robust cortical gray matter growth compared with white matter growth, with occipital regions growing much faster than prefrontal regions. Sexual dimorphism is present at birth, with males having larger total brain cortical gray and white matter volumes than females. In contrast to adults and older children, the left hemisphere is larger than the right hemisphere, and the normal pattern of fronto-occipital asymmetry described in older children and adults is not present. Regional differences in cortical gray matter growth are likely related to differential maturation of sensory and motor systems compared with prefrontal executive function after birth. These findings also indicate that whereas some adult patterns of sexual dimorphism and cerebral asymmetries are present at birth, others develop after birth.

Intracranial Hemorrhage in Asymptomatic Neonates: Prevalence on MR Images and Relationship to Obstetric and Neonatal Risk Factors

PURPOSE

To retrospectively evaluate the prevalence of neonatal intracranial hemorrhage (ICH) and its relationship to obstetric and neonatal risk factors.

MATERIALS AND METHODS

Pregnant women were recruited for a prospective study of neonatal brain development; the study was approved by the institutional review board and complied with HIPAA regulations. After informed consent was obtained from a parent, neonates were imaged with 3.0-T magnetic resonance (MR) imaging without sedation. The images were reviewed by a neuroradiologist with 12 years of experience for the presence of ICH. Medical records were prospectively and retrospectively reviewed for selected risk factors, which included method of delivery, duration of labor, and evidence of maternal or neonatal birth trauma. Risk factors were assessed for relationship to ICH by using Fisher exact test statistics.

RESULTS

Ninety-seven neonates (mean age at MR imaging, 20.8 days +/- 6.9 [standard deviation]) underwent MR imaging between the ages of 1 and 5 weeks. Eighty-eight (44 male and 44 female) neonates (65 with vaginal delivery and 23 with cesarean delivery) completed the MR imaging evaluation. Seventeen neonates with ICHs (16 subdural, two subarachnoid, and six parenchymal hemorrhages) were identified. Seven infants had two or more types of hemorrhages. All neonates with ICH were delivered vaginally, with a prevalence of 26% in vaginal births. ICH was significantly associated with vaginal birth (P < .005) but not with prolonged duration of labor or with traumatic or assisted vaginal birth.

CONCLUSION

Asymptomatic ICH following vaginal birth in full-term neonates appears to be common, with a prevalence of 26% in this study.

Cerebral Blood Volume Measurements and Proton MR Spectroscopy in Grading of Oligodendroglial Tumors

OBJECTIVE

The purpose of this study was to determine whether perfusion-weighted imaging (PWI) and proton MR spectroscopy (MRS) are useful in differentiating high- and low-grade oligodendroglial tumors.

MATERIALS AND METHODS

PWI and MRS studies of 22 patients with histologically proven oligodendroglioma or oligoastrocytoma (13 low-grade and nine anaplastic tumors) were retrospectively reviewed. PWI of 14 subjects was performed with a dynamic contrast-enhanced susceptibility-weighted echo-planar technique. Intratumoral relative cerebral blood volume ratio was calculated and normalized to the same value in contralateral normal-appearing white matter. Multivoxel MRS was performed with a point-resolved spectroscopy sequence at a TE of 135 milliseconds in 20 patients and with the addition of a TE of 30 seconds in 17 patients. MRS data were expressed as intratumoral metabolite ratios (choline to creatine [Cho/Cr], choline to N-acetyl aspartate, N-acetyl aspartate to creatine, and myoinositol to creatine).

RESULTS

Relative cerebral blood volume ratios were significantly different (p = 0.004) between low-grade (1.61 +/- 1.20) and high-grade tumors (5.45 +/- 1.96). The optimal relative cerebral blood volume ratio cutoff value in identification of anaplastic oligodendroglial tumors was 2.14. Analysis of MRS data showed significantly higher Cho/Cr ratios (p = 0.002) in high-grade than in low-grade tumors. A Cho/Cr ratio cutoff value of 2.33 had the highest accuracy in identification of high-grade tumors.

CONCLUSION

Relative cerebral blood volume measurement and MRS are helpful in differentiating low-grade from anaplastic oligodendroglial tumors.

Parasellar tumors: suprasellar and cavernous sinuses

This article will review the presentation and imaging appearance of tumors affecting the area around the pituitary gland. For convenience, the lesions will be discussed in order of the regions they usually affect. For example, lesions affecting the suprasellar region include craniopharyngiomas, optic or hypothalamic gliomas, germ cell tumors, epidermoids, dermoids, hamartomas, lipomas, and choristomas. Tumors that commonly affect the parasellar cavernous sinus include schwannomas and meningiomas. Tumors like chordomas may arise in the sphenoid bone or clivus and affect the sella. Metastasis, meningiomas and aneurysms may involve any area around the sella. For a detailed discussion of normal anatomy and imaging protocols, see the first article of this monograph.

Clinical role of proton magnetic resonance spectroscopy in oncology: brain, breast, and prostate cancer

Standardised proton magnetic resonance spectroscopic imaging (MRSI) was initially developed for routine in-situ clinical assessment of human brain tumours, and its use was later extended for examination of prostate and breast cancers. MRSI coupled with both routine and functional MRI techniques provides more detailed information about a tumour's location and extent of its infiltration than any other modality alone. Information obtained by adding MRSI data to anatomical and functional MRI findings aid in clinical management decisions (such as watchful waiting vs immediate intervention). In this Review, we discuss the current status of proton MRSI, with emphasis on its clinical use to map the location and extent of tumour processes for spectroscopic image-guided biopsy procedures and to monitor treatment paradigms for brain, prostate, and breast cancer.

Vessel tortuosity and brain tumor malignancy: a blinded study

RATIONALE AND OBJECTIVES

Malignancy provokes regional changes to vessel shape. Characteristic vessel tortuosity abnormalities appear early during tumor development, affect initially healthy vessels, spread beyond the confines of tumor margins, and do not simply mirror tissue perfusion. The ability to detect and quantify tortuosity abnormalities on high-resolution magnetic resonance angiography (MRA) images offers a new approach to the noninvasive diagnosis of malignancy. This report evaluates a computerized, statistical method of analyzing the shapes of vessels extracted from MRA in diagnosing cancer.

MATERIALS AND METHODS

The regional vasculature of 34 healthy subjects was compared with the tumor-associated vasculature of 30 brain tumors before surgical resection. The operator performing the analysis was blinded to the diagnosis. Vessels were segmented from an MRA of each subject, a region of interest was defined in each tumor patient and was mapped to all healthy controls, and a statistical analysis of vessel shape measures was then performed over the region of interest. Many difficult cases were included, such as pinpoint, hemorrhagic, and irradiated tumors, as were hypervascular benign tumors. Tumors were identified as benign or malignant on the basis of histological evaluation.

RESULTS

A discriminant analysis performed at the study's conclusion successfully classified all but one of the 30 tumors as benign or malignant on the basis of vessel tortuosity.

CONCLUSIONS

Quantitative, statistical measures of vessel shape offer a new approach to the diagnosis and staging of disease. Although the methods developed under the current report must be tested against a new series of cases, initial results are promising.

Hemodynamic and permeability changes in posterior reversible encephalopathy syndrome measured by dynamic susceptibility perfusion-weighted MR imaging

BACKGROUND AND PURPOSE

The physiological mechanism that gives rise to posterior reversible encephalopathy syndrome (PRES) is currently unknown. We sought to better understand the mechanism of the edema formation in PRES and specifically hypothesized that this edema is caused by increased vascular permeability.

METHODS

Eight consecutive patients with PRES who had been studied by using perfusion MR imaging were retrospectively identified. Perfusion images were obtained using a gradient-echo echo planar sequence with contrast enhancement. Measures of apparent diffusion coefficient (ADC), cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT) and vascular permeability (K2) were calculated in the affected posterior brain areas and normalized to values obtained in unaffected anterior brain. These values were compared with those found in healthy subjects.

RESULTS

Regions of interest within the posterior affected brain indicated a significant increase in ADC values in all but one patient, a significant decrease in CBV and CBF values in all patients with PRES (average 30% of control), variable changes in MTT, and no measurable change in K2.

CONCLUSION

The decrease in both CBV and CBF in PRES supports the theory of autoregulatory vasoconstriction; changes in K2 were not detected.

Pseudoephedrine and guaifenesin urolithiasis: widening the differential diagnosis of radiolucent calculi on abdominal radiograph

Unenhanced helical computed tomography has played an increasingly important role in the management of urinary tract stones, guiding diagnosis and control of calculus disease. We report computed tomographic and radiographic appearances of a renal calculus composed of pseudoephedrine and guaifenesin in a patient who abused over-the-counter allergy medication.

Correlation of MR perfusion imaging and vessel tortuosity parameters in assessment of intracranial neoplasms

Advances in noninvasive imaging techniques such as magnetic resonance perfusion imaging have been found useful in grading cerebral neoplasms and have potential for significant clinical benefit. The purpose of this study was to determine the correlation between tumor vessel tortuosity as measured from vessels extracted from magnetic resonance angiograms (MRA) and perfusion parameters of cerebral blood flow (CBF) and cerebral blood volume (CBV) in intracranial neoplasms. We hypothesized that tumor blood vessel tortuosity measures and perfusion measures would be correlated, since both are increased by tumor angiogenesis. 18 patients with 19 cerebral neoplasms were evaluated with conventional MR imaging and dynamic contrast-enhanced T2-weighted perfusion MR imaging (PWI). Both benign and malignant lesions were included, as were hyper- and hypovascular tumors. Regions of interest were plotted within the tumor area to locate foci of maximum CBV and CBF. CBV and CBF measurements were also recorded in contralateral normal appearing white matter to calculate relative CBV (rCBV) and relative CBF (rCBF). Vessel tortuosity analyses were conducted upon vessels segmented from MRA images of the same patients using two tortuosity descriptors (SOAM and ICM), which have previously been demonstrated to have efficacy in separating benign from malignant disease. Linear regression analyses were conducted to determine if correlations exist between CBV or CBF and the two tortuosity measurements. For the overall set of tumors, no significant correlations were found between flow or volume measures and the tortuosity measures. However, when the 7 glioblastoma multiforme tumors were examined as a subgroup, the following significant correlations were found: rCBV and SOAM (R2=0.799), rCBV and ICM (R2=0.214). Our results demonstrate that MR perfusion imaging data do not correlate significantly with vessel tortuosity parameters as determined from the larger vessels seen by MRA. However, for subgroups of a particular tumor type such as GBM, there may be significant correlations. It appears that perfusion and tortuosity data may provide independently useful data in the assessment of cerebral neoplasms.

Abnormal vessel tortuosity as a marker of treatment response of malignant gliomas: preliminary report

Despite multiple advances in medical imaging, noninvasive monitoring of therapeutic efficacy for malignant gliomas remains problematic. An underutilized observation is that malignancy induces characteristic abnormalities of vessel shape. These characteristic shape abnormalities affect both capillaries and much larger vessels in the tumor vicinity, involve larger vessels prior to sprout formation, and are generally not present in hypervascular benign tumors. Vessel shape abnormalities associated with malignancy thus may appear independently of increase in vessel density. We hypothesize that an automated, computerized analysis of vessel shape as defined from high-resolution MRA can provide valuable information about tumor activity during the treatment of malignant gliomas. This report describes vessel shape properties in 10 malignant gliomas prior to treatment, in 2 patients in remission during treatment, and in 2 patients with recurrent disease. One subject was scanned multiple times. The method involves an automated, statistical analysis of vessel shape within a region of interest for each tumor, normalized by the values obtained from the vessels within the same region of interest of 34 healthy subjects. Results indicate that untreated tumors display statistically significant vessel tortuosity abnormalities. These abnormalities involve vessels not only within the tumor margins as defined from MR but also vessels in the surrounding tissue. The abnormalities resolve during effective treatment and recur with tumor recurrence. We conclude that vessel shape analysis could provide an important means of assessing tumor activity.

Neuroimaging in human immunodeficiency virus infection

Human immunodeficiency virus (HIV) is associated with central nervous system (CNS) changes that may affect cerebral blood flow (CBF), metabolism, structure, and diffusion. Each of the available neuroimaging techniques offers unique insight into the neural mechanisms underlying HIV, as well as a potential means of monitoring disease progression and treatment response. The purpose of the article is to provide a review of experimental studies evaluating changes related to HIV with imaging techniques, including single-photon emission computed tomography (SPECT), positron emission tomography (PET), volumetric magnetic resonance imaging (MRI), functional MRI (fMRI), magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), and perfusion MRI (pMRI).

Neurosarcoidosis--review of imaging findings

Five to 25% of patients with systemic sarcoidosis also have CNS involvement. Patients with systemic disease may initially present with neurologic symptoms, and rarely, the sarcoidosis may be isolated to the CNS. A typical imaging feature is thickening and enhancement of the basilar leptomeninges of the brain. Other imaging findings, such as enhancing or nonenhancing parenchymal lesions, dural, and bone lesions may occur in the head and spine. Because there is a high rate of progression and recurrence following treatment, imaging follow-up is recommended in all patients.

3 Tesla magnetic resonance imaging of the brain in newborns

While it has been hypothesized that brain development is abnormal in schizophrenia and other neurodevelopmental disorders, there have been few attempts to study very early brain development in children. Twenty unsedated healthy newborns underwent 3 Tesla magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI). The left ventricle was significantly larger than the right; females had significantly larger ventricles than males. Fractional anisotropy (FA) increased significantly with gestational age in the genu and splenium of the corpus callosum. It is feasible to study brain development in unsedated newborns using 3 T MRI.

Atypical MR imaging perfusion in developmental venous anomalies

Developmental venous anomalies (DVAs) are common variants of cerebral venous drainage that are typically incidental findings on contrast-enhanced MR imaging studies. We present four cases of asymptomatic DVAs that demonstrate increased cerebral blood flow, cerebral blood volume, mean transit time, and time to peak on perfusion MR images. Our study indicates that alterations in perfusion MR imaging parameters can be seen with uncomplicated DVAs and do not necessarily imply a more ominous underlying etiologic factor, such as hypervascular tumor or stroke.

Brain MRI findings in patients with mucopolysaccharidosis types I and II and mild clinical presentation

Our objective was to determine the brain magnetic resonance imaging (MRI) abnormalities in a selected group of patients with mucopolysaccharidosis (MPS) types I and II who had only mild clinical manifestations. We retrospectively assessed MRI brain studies in 18 patients with MPS (type I: 6 and type II: 12). We evaluated abnormal signal intensity in the white matter, widening of the cortical sulci, size of the supratentorial ventricles, dilatation of the perivascular spaces (PVS) and enlargement of the subarachnoid spaces. We observed a broad spectrum of findings, and despite severely abnormal MRI studies, no patients had mental retardation. We also observed that dilated PVS, previously believed to be caused by macroscopic deposition of the mucopolysaccharides, had an appearance similar to cerebrospinal fluid (CSF) in all MRI sequences performed, even in FLAIR and trace diffusion weighted images. Based on our results, we believe that with the exception of white matter abnormalities and brain atrophy, all other findings may be related to abnormal resorption of CSF, and there is no relationship between the imaging and clinical manifestations of the disease.

CT findings of increased splanchnic circulation in a case of celiac sprue

We report a diagnosis of celiac disease first suggested by the computed tomographic appearance, which included findings indicative of increased splanchnic circulation. Similar findings have been reported with angiography and ultrasound but, to our knowledge, have not been reported with computed tomography.

MR spectroscopy of brain tumors

MR spectroscopy is a non-invasive technique for measuring tissue metabolites. Changes in tissue metabolites may be useful for diagnosing or characterizing primary and other brain neoplasms, planning treatment, and assessing the results of treatment. Ongoing improvements in equipment and pulse sequence design may make full brain spectroscopy clinically practical in the near future. The authors review the basic concepts of MR spectroscopy and its use in clinical management of brain neoplasms.

Radio-frequency ablation in cirrhotic patients with hepatocellular carcinoma

Current surgical treatments for hepatocellular carcinoma (HCC) include radio-frequency ablation (RFA), resection, and orthotropic liver transplant (OLT). RFA is particularly attractive in these high-risk patients because surgery is associated with high mortality and there is a relative scarcity of organs available for those in need of transplants. This study was performed to evaluate the management of cirrhotic patients with HCC undergoing RFA at a single Western institution. A retrospective study from March 1999 to June 2002 was performed to evaluate the clinicopathologic and treatment-related variables in cirrhotic patients with HCC. Forty-nine lesions in 26 patients with HCC and cirrhosis underwent RFA. Data was analyzed for safety and overall survival as the main endpoints. The mean age was 60.4 +/- 11 years, 19 patients were male, 5 had hepatitis B virus, and 19 had hepatitis C virus. The Child classification was 26 per cent, 39 per cent, and 35 per cent for A, B, and C; the number of lesions was 1 in 62 per cent, 2 in 23 per cent, and more than 2 in 15 per cent. The approach was laparoscopic in 58 per cent, percutaneous in 15 per cent, and open in 27 per cent. There were no mortalities and only 1 complication. Average hospital stay was 2.7 +/- 2 days. Subsequent to RFA, 9 patients underwent an OLT within a median of 4.1 months. The median follow-up of the whole group was 13 months and the disease-free survival 9.3 months. Tumor recurrence was identified in 3 previously ablated lesions, nonablated liver in 11, and as pulmonary metastases in 3. Overall survival (P = 0.03) was prolonged for those treated with RFA + OLT over RFA alone. We conclude that RFA is a safe ablative technique in high-risk cirrhotic patients with HCC. This technique may provide a bridge to OLT; however, it remains to be proven whether it prolongs survival in those who do not undergo OLT.

Apparent diffusion coefficient measurements in the hippocampi in patients with temporal lobe seizures

BACKGROUND AND PURPOSE

Loss of neurons results in a relative increase in extracellular space that may lead to altered apparent diffusion coefficient (ADC) values in the hippocampi of patients with seizures. Our purpose was to determine if ADC values along the long axis of hippocampi are useful in evaluating patients with partial complex seizures.

METHODS

Hippocampi of 23 patients with partial complex seizures and 25 healthy volunteers were evaluated with MR imaging and ADC maps. MR images were evaluated for loss of volume and/or high signal intensity on T2-weighted images and compared with ADC maps. ADCs were compared between patients and controls, as were ADCs along the length of each hippocampus. Mean and SDs were obtained for each measurement, and level of significance was determined (P <.05). The relationship between clinical lateralization and MR imaging and ADCs was studied.

RESULTS

No significant variations were found in the ADCs in controls (side to side and along hippocampi). In patients, abnormalities were seen with MR imaging alone in 16, with ADC in 14, and with both in 21. Of 23 hippocampi with an abnormal MR appearance, 14 had abnormal ADCs. Nine hippocampi with a normal MR appearance had abnormal ADCs. Normal MR appearance and ADCs were seen in 13 hippocampi. Most abnormal ADCs were seen in the anterior aspect of the hippocampi. All differences were statistically significant. Of 19 patients who underwent clinical testing, unequivocal lateralization was established in 10. Concordance between clinical tests and MR imaging, ADC, and MR imaging plus ADC was found in five, five, and seven patients, respectively.

CONCLUSION

Visual assessment was better than ADCs alone for detection of abnormal hippocampi. MR imaging plus ADCs was better than either technique alone. ADCs may be abnormal when MR images are unremarkable. Concordance with clinical lateralization was better when MR imaging and ADC were jointly evaluated than when either technique was evaluated separately.

Cranial fasciitis of childhood

Cranial fasciitis is a benign fibroblastic tumor of the skull found almost exclusively in young children. It is histologically identical to nodular fasciitis. We present the clinical, radiologic, and pathologic findings of a 7-month-old male infant with cranial fasciitis of the skull. Herein, we include the first description of this entity's diffusion-weighted imaging appearance. Although rare, cranial fasciitis can mimic more aggressive processes both clinically and radiographically.

Differentiation of toxoplasmosis and lymphoma in AIDS patients by using apparent diffusion coefficients

BACKGROUND AND PURPOSE

Distinguishing between toxoplasmosis and lymphoma brain lesions in AIDS patients is difficult but clinically relevant. This study was performed to test the hypothesis that diffusion-weighted (DW) imaging with apparent diffusion coefficient (ADC) maps can be used to distinguish these two lesions.

METHODS

The ADC values were calculated in regions of interest placed in 13 brain toxoplasmosis lesions and eight brain lymphoma lesions in patients with AIDS. These values were compared with those of normal white matter. ADC ratios in lymphoma lesions then were compared with those in toxoplasmosis lesions by using a two-sample two-tailed t test.

RESULTS

Toxoplasmosis lesions demonstrated significantly greater diffusion than that of lymphoma lesions (P =.004). ADC ratios were 1.63 +/- 0.41 (mean +/- standard deviation) in the 13 toxoplasmosis lesions and 1.14 +/- 0.25 in the eight lymphoma lesions. While considerable overlap was present for ADC ratios between 1.0 and 1.6, ADC ratios greater than 1.6 were associated solely with toxoplasmosis, accounting for seven of 13 toxoplasmosis lesions.

CONCLUSION

ADC values are helpful in differentiating toxoplasmosis from lymphoma in patients with AIDS.

Alterations of brain activity associated with resolution of emotional distress and pain in a case of severe irritable bowel syndrome

BACKGROUND & AIMS

The association of psychosocial disturbances with more severe irritable bowel syndrome (IBS) is well recognized. However, there is no evidence as to how these associations might be mediated. Functional magnetic resonance imaging (fMRI) offers an opportunity to study whether activation of the cingulate cortex, an area involved with the affective and pain intensity coding might be linked to poorer clinical status with IBS. In this case report, we found an association between the severity of a patient's clinical symptoms and psychosocial state, with activation of the cingulate cortex. We also found that clinical and psychosocial improvement was associated with reduced cingulate activation.

METHODS

Observational case report of a young woman observed for 16 years with a history of sexual abuse, psychosocial distress, and functional GI complaints. Psychosocial, clinical, and fMRI assessment was performed when the patient experienced severe symptoms and again 8 months later when clinically improved.

RESULTS

During severe illness, the patient had major psychosocial impairment, high life stress, a low visceral pain threshold, and activation of the midcingulate cortex (MCC), prefrontal area 6/44, and the somatosensory cortex, areas associated with pain intensity encoding. When clinically improved, there was resolution in activation of these 3 areas, and this was associated with psychosocial improvement and an increased threshold to rectal distention.

CONCLUSIONS

Activation of the MCC and related areas involved with visceral pain encoding are associated with poor clinical status in patients with severe IBS and psychosocial distress and appear to be responsive to clinical improvement.

False-negative contrast MRA in the setting of carotid artery dissection

A case of false-negative contrast magnetic resonance angiography (MRA) in the setting of significant carotid stenosis caused by a carotid arterial intimal dissection is described. If arterial dissection is suspected but contrast MRA is normal, additional evaluation may be warranted. In this case the abnormality was detectable on 2D time-of-flight MRA and contrast digital subtraction arteriography. Since MRA has become a commonly used initial screening test for carotid stenosis, it is important to understand the possibility of false-negative results.

Proton magnetic resonance spectroscopy of brain-stem lesions

The imaging findings of brain-stem lesions are often nonspecific and histological diagnosis is limited because of fear of complications associated with biopsy. A noninvasive method for tissue characterization is therefore highly desirable. We undertook a review of proton magnetic resonance spectroscopy (MRS) of patients with solitary brain-stem lesions to determine if MRS could characterize them. We carried out single- or multivoxel proton MRS using long echo times (135 or 270 ms) on 34 patients with solitary brain-stem lesions. We analyzed the following peaks: choline (Cho), creatine (Cr), N-acetylaspartate (NAA), and lipids/lactate (Lip) and calculated peak height ratios for Cho/Cr, NAA/Cr and Lip/Cr. The results were compared with histology in nine patients and with the presumptive diagnosis in 25. We also performed single-voxel proton MRS on the brain stem of five normal volunteers. There were differences in all ratios between controls and the patients with neoplastic and non-neoplastic lesions: Cho/Cr was low in non-neoplastic and high in neoplastic lesions (control: 1.8+/-0.1; non-neoplastic: 1.4+/-0.2; neoplastic: 2.0+/-0.2); NAA/Cr was low in non-neoplastic, and lower in neoplastic lesions (control: 2.3+/-0.1; non-neoplastic: 1.4+/-0.2; neoplastic: 1.2+/-0.1), and Lip/Cr was elevated in both neoplastic and non-neoplastic lesions (control: 0.04+/-0.02; nonneoplastic: 1.9+/-0.7; neoplastic:1.9+/-0.7).

Protein-losing enteropathy in a young African-American woman with abdominal pain, diarrhea and hydronephrosis

The case of a 21-year-old African-American woman who presented with abdominal pain, diarrhea and hydronephrosis and who proved to have protein-losing enteropathy secondary to systemic lupus erythematosus is discussed. This is an unusual complication of lupus.

Clinical applications of proton MR spectroscopy in oncology

Proton magnetic resonance spectroscopy (H1-MRS) has been increasingly receiving more attention from radiologists, neurosurgeons, radiation and medical oncologists in the "in situ" clinical evaluation of human tumors. The utilization of H1-MRS, especially in human brain tumors, coupled to both routine magnetic resonance imaging (MRI) and functional MRI techniques provides greater information concerning tumor grading and extension and characterization of the normal surrounding tissue than what is possible with any other imaging technique alone. In this paper, we will review the current status of proton MR spectroscopy with emphasis on its clinical utility to diagnose tumors, its utility in planning surgical and radiation therapy interventions, and in its use in monitoring tumor treatment.

The influence of presentation format and viewer training in the visual arts on the perception of pictorial and aesthetic qualities of paintings

The comparability of viewers' responses to slide-projected and computer-generated images of nine paintings by renowned artists to those obtained from individuals experiencing the originals in the galleries of the New York Metropolitan Museum of Art was investigated. The influence of training in the visual arts upon evaluative judgments made under the three presentation formats was also assessed. Specifically, art-trained and untrained participants in each format condition rated each artwork on sixteen measures of physical and structural characteristics, novelty of content, and aesthetic qualities. Analyses revealed significant differences in the judged hedonic value of the originals as contrasted with the two types of reproduction, whereas trained and untrained participants' evaluations of the pictorial qualities of the artworks were comparable across presentation formats. Findings are discussed in terms of a facsimile-accommodation hypothesis proposed by the authors.

The effects of HIV infection on endothelial function

Endothelial dysfunction and/or injury is pivotal to the development of cardiovascular and inflammatory pathology. Endothelial dysfunction and/or injury has been described in Human Immunodeficiency Virus (HIV) infection. Elaboration of circulating markers of endothelial activation, such as soluble adhesion molecules and procoagulant proteins, occurs in HIV infection. Certain endothelial cells, such as those lining liver sinusoids, human umbilical vein endothelial cells, bone marrow stromal endothelial cells or brain microvascular endothelial cells, have been shown to be variably permissive for HIV infection. Entry of virus into endothelial cells may occur via CD4 antigen or galactosyl-ceramide receptors. Other mechanisms of entry including chemokine receptors have been proposed. Nevertheless, endothelial activation may also occur in HIV infection either by cytokines secreted in response to mononuclear or adventitial cell activation by virus or else by the effects of the secreted HIV-associated proteins, gp 120 (envelope glycoprotein) and Tat (transactivator of viral replication) on endothelium. Enhanced adhesiveness of endothelial cells, endothelial cell proliferation and apoptosis as well as activation of cytokine secretion have all been demonstrated. Synergy between select inflammatory cytokines and viral proteins in inducing endothelial injury has been shown. In HIV infection, dysfunctional or injured endothelial cells potentiate tissue injury, inflammation and remodeling, and accelerate the development of cardiovascular disease.

Exercise and atherogenesis

Atherogenesis involves the activation of endothelial cells and the egress of atherogenic T lymphocytes and monocytes into the intima. Exercise training contributes to the arrest and even reversal of atherosclerosis by modifying risk factors and by inducing an atheroprotective phenotype in endothelial cells and T cells.

Proton MR spectroscopy in patients with acute temporal lobe seizures

BACKGROUND AND PURPOSE

Decreases in N-acetyl aspartate (NAA) as seen by proton MR spectroscopy are found in hippocampal sclerosis, and elevated levels of lipids/lactate have been observed after electroconvulsive therapy. Our purpose was to determine whether increased levels of lipids/lactate are found in patients with acute seizures of hippocampal origin.

METHODS

Seventeen patients with known temporal lobe epilepsy underwent proton MR spectroscopy of the mesial temporal lobes within 24 hours of their last seizure. Four of them were restudied when they were seizure-free. Five healthy individuals were used as control subjects. All MR spectroscopy studies were obtained using a single-voxel technique with TEs of 135 and 270. The relationship between the presence of lipids/lactate and seizures was tested using Fisher's exact test. Mean and standard deviations for NAA/creatine (Cr) were obtained in the hippocampi in patients with seizures on initial and follow-up studies and these values were compared with those in the control subjects.

RESULTS

Seizure lateralization was obtained in 15 patients. Of the 17 seizure locations that involved hippocampi, 16 showed lipids/lactate by proton MR spectroscopy. Of the 13 hippocampi not directly affected by seizures, 10 showed no lipids/lactate and three showed lipids/lactate. The relationship between lipids/lactate and seizure location was confirmed. A comparison of NAA/Cr ratios for the involved hippocampi with those in control subjects showed significant differences on initial MR spectroscopy; however, no significant difference was found between acute and follow-up NAA/Cr ratios in hippocampi affected by seizures.

CONCLUSION

Lipids/lactate were present in the hippocampi of patients with acute seizures and decreased when the patients were seizure-free. Thus, lipids/lactate may be a sensitive marker for acute temporal lobe seizures.

Apparent diffusion coefficients in the evaluation of high-grade cerebral gliomas

BACKGROUND AND PURPOSE

Preliminary data indicate that apparent diffusion coefficient (ADC) values may be useful in identifying and grading primary cerebral tumors. We tested the hypothesis that ADC values can be used to differentiate tumor, edema, and normal brain tissue.

METHODS

Fifteen patients with high-grade cerebral astrocytomas underwent conventional MR imaging, diffusion-weighted MR imaging, and proton MR spectroscopy. We defined tumor as an area containing the highest choline/creatine and choline/N-actetyl aspartate ratios, contrast enhancement, and abnormal T2 signal intensity. Edema was defined as tissue with normal proton MR spectra, no enhancement, and high T2 signal intensity. Normal brain was assumed if tissue had normal proton MR spectra, no enhancement, and normal T2 signal intensity in the hemispheres ipsilateral or contralateral to tumor. ADC maps were calculated and regions of interest were manually placed over areas of tumor, edema, and normal tissue. Comparisons were made by analysis of variance. For post hoc testing, the Tukey method was used to correct for the effect of multiple comparisons, and significance was accepted if P was less than .05.

RESULTS

When ADC values were analyzed as a group, significant differences were found between tumor (131 + 45) and normal brain tissue (ipsilateral to tumor, 92 + 22; contralateral to tumor, 78 + 5) but not between tumor and adjacent edema (129 + 45). A plot of individual data points showed considerable overlapping among the three types of tissue sampled.

CONCLUSION

As a group, ADC values helped to distinguish high-grade glioma from normal tissue but could not be used to separate high-grade glioma from surrounding edema. Individually, ADC values overlapped considerably and were not useful in our patients. The utility of ADC values (as obtained in this relatively small study) is questionable in patients with high-grade cerebral astrocytomas.

Focal posttransplantation lymphoproliferative disorder at the renal allograft hilum

OBJECTIVE

This report describes the imaging characteristics of focal posttransplantation lymphoproliferative disorder.

CONCLUSION

Posttransplantation lymphoproliferative disorder may be limited to the allograft. A focal complex mass in the renal allograft hilum surrounding the main renal blood vessels is a common finding and can be visualized with sonography. MR imaging can help increase diagnostic confidence.

Correlation of myo-inositol levels and grading of cerebral astrocytomas

BACKGROUND AND PURPOSE

In a limited number of patients, the level of myo-inositol (MI), as seen by proton magnetic resonance spectroscopy (HMRS), has been shown to differ for gliomas of different histologic grades. We sought to determine if MI levels correlate with cerebral astrocytoma grade.

METHODS

Five control subjects, 14 patients with low-grade astrocytoma, 10 patients with anaplastic astrocytoma, and 10 patients with glioblastoma multiforme (GBM) underwent single-volume HMRS with an echo time of 20 ms. Twenty-five patients had received surgery, chemotherapy, and/or radiation therapy previously. Using the curve-fitting program supplied by the manufacturer, peak areas for n-acetyl aspartate (NAA), choline (Cho), and MI were normalized with respect to the peak area of creatine (Cr). Ratios for MI/Cr, Cho/Cr, and NAA/Cr were obtained for each lesion and retrospectively compared with the histologic grade of the lesion.

RESULTS

Levels of MI/Cr were higher (0.82 +/- 0.25) in patients with low-grade astrocytoma, intermediate (0.49 +/- 0.07) in control subjects, and lower in patients with anaplastic astrocytoma (0.33 +/- 0.16) and GBM (0.15 +/- 0.12).

CONCLUSION

Our study shows a trend toward lower MI levels in the presence of anaplastic astrocytomas and GBMs compared with those of low-grade astrocytomas. MI levels may have implications in the grading of cerebral astrocytomas.

The cardiovascular and metabolic complications of HIV infection

With the advent of more effective therapies for human immunodeficiency virus (HIV) infection, HIV-infected patients are living longer and cardiovascular disease is becoming more obvious in this population. Patients with HIV infection represent one of the most rapidly developing groups with cardiovascular disease globally. Cardiovascular disease complicating HIV infection is likely to contribute to burgeoning healthcare costs. Pericarditis, myocarditis, cardiomyopathy, atherosclerotic coronary vasculopathy, arterial aneurysms, pulmonary hypertension, and endocarditis occur with increased frequency in these patients. Pericardial tamponade, dilated cardiomyopathy, endocarditis, and vasculopathy can lead to fatal outcomes in this population. The advent of cardiomyopathy heralds a very poor prognosis in patients infected with HIV. Coronary vasculopathy without obvious risk factors can lead to myocardial ischemia in young patients infected with the virus. Moreover, the protease inhibitors used to treat HIV infection induce a syndrome of lipodystrophy and dyslipidemia that may be associated with accelerated atherosclerosis as well as insulin resistance. All these factors contribute to increased cardiovascular morbidity and mortality in the HIV-infected population. HIV infection, opportunistic infections, secreted viral proteins such as gp120 (envelope protein) or Tat (transactivator of viral transcription), and cytokines elaborated during the course of HIV infection of the immune system all contribute to pathogenesis of these disorders. Further basic and clinical studies are required to understand the pathogenesis of cardiovascular complications and develop appropriate management strategies for these patients.