Gemcitabine-associated posterior reversible encephalopathy syndrome: MR imaging and MR spectroscopy findings

A 55 year old female receiving gemcitabine for stage IV non-small cell carcinoma of the lung developed the clinical-radiologic syndrome of posterior reversible encephalopathy syndrome (PRES). She had clinical manifestations of headaches, increasing somnolence and tonic-clonic seizures. The fluid-attentuated inversion recovery (FLAIR) MR imaging sequence conspicuously showed bihemispheric, symmetrical cortical and subcortical white matter hyperintensities that preponderantly involved the parietal and occipital lobes. Diffusion-weighted imaging (DWI) sequence reflected the preponderant existence of vasogenic edema in the involved areas. MR spectroscopy showed no significant N-acetyl aspartate (NAA) depletion or lactate elevation prospectively, indicating the absence of significant neuronal loss and reversibility of the brain parenchymal changes. The clinical and radiologic manifestations essentially resolved completely with discontinuation of the drug.     

Central neurocytoma: proton MR spectroscopy and diffusion weighted MR imaging findings

Purpose

To present proton magnetic resonance spectroscopy and diffusion-weighted imaging (DWI) findings of central neurocytoma (CN).

Methods and Materials

Imaging findings of seven patients with the histopathological diagnosis of CN (five male and two female; age range, 21–28 years of age) were evaluated retrospectively. In addition to conventional magnetic resonance imaging features, we also assessed the metabolite ratios and tumor normalized apparent diffusion coefficient (NADC), which was calculated by dividing the tumor apparent diffusion coefficient (ADC) values by normal ADC. Approval from our institutional review board was obtained for this review.

Results

The tumor choline/creatine ratios were 5.17±2.38, while N-acetyl aspartate/choline and N-acetyl aspartate/creatine ratios were 0.33±0.15 and 1.84±1.38, respectively. On DWI, tumors had heterogeneous hyperintense appearances when compared with the contralateral parietal lobe white matter and tumor NADC values were 0.63±0.05.

Conclusion

Significantly increased choline/creatine and decreased N-acetyl aspartate/choline ratios with lower NADC values in CN resemble high-grade gliomas and complicate the diagnosis. Familarity its physiologic features would help to presurgical diagnosis of ventricular and exraventricular CNs.     

Delayed myelination in a rhizomelic chondrodysplasia punctata case: MR spectroscopy findings

Rhizomelic chondrodysplasia punctata is a member of genetic peroxisomal disorders. Delayed myelination, which is probably related to the inadequacy of plasmalogens biosynthesis, is an important feature of this disorder. Direct assessment of neuropathologic aspects of RCDP syndrome such as neuronal degeneration and delayed myelination is possible with MR spectroscopy.In this report, MR spectroscopy findings (decreased Cho/Cr and increased Ins-Gly/Cr ratios and increased levels of mobile lipids) of a rhizomelic chondrodysplasia punctata case supporting delayed myelination are presented. This is the second report of MR spectroscopy examination of the specific brain metabolic changes associated with rhizomelic chondrodysplasia punctata.     

Central pontine myelinolysis after liver transplantation: MR diffusion, spectroscopy and perfusion findings

Magnetic resonance spectroscopy (MRS) and perfusion of central pontine myelinolysis (CPM) have been rarely reported. One case of CPM that developed after liver transplantation was analyzed with serial diffusion-weighted imaging (DWI), MRS and MR perfusion. During the acute phase, a pontine lesion showed an obvious high-signal intensity on DWI with decreased apparent diffusion coefficient value, decreased N-acetylaspartate (NAA)/creatine (Cr) ratio, increased choline (Cho)/Cr ratio and increased perfusion on the cerebral blood volume map. In a later phase, the lesion showed isosignal intensity on DWI, further decreased NAA/Cr ratio, increased Cho/Cr ratio and decreased perfusion. The increase in lesion perfusion during the acute phase may reflect a higher metabolic activity due to an increase in cell number and activity.     

Comparative evaluation of magnetization transfer MR imaging and in-vivo proton MR spectroscopy in brain tuberculomas

We have compared and analyzed the value of in vivo proton MR spectroscopy (PMRS) and T1 weighted magnetization transfer (MT) MR imaging in tissue characterization of brain tuberculomas. We studied 33 cases of proven intracranial tuberculomas with in vivo PMRS and T1 weighted MT MR imaging. MT ratios from the rim and core of the tuberculomas were calculated and compared with metabolites seen on PMRS. Final diagnosis of tuberculoma was based on histopathology (n = 26) and/or associated tuberculous meningitis (n = 7) in all the cases. Out of the 33 patients who underwent both PMRS and T1 weighted MT MR imaging, spectroscopy showed only lipids at 0.9 ppm, 1.3 ppm, 2.0 ppm, and 2.80 ppm in 26 cases while lipids at 0.9 ppm, 1.3 ppm, 2.0 ppm and 2.80 ppm along with choline at 3.22 ppm was seen in remaining 7 patients. MT ratios from the core or solid necrosis varied from 21-29% while from the rim or cellular region varied from 16-24%. MT ratios from all the 33 lesions were consistent with tuberculomas while PMRS showed choline along with lipids in 7 predominantly cellular lesions simulating a neoplasm. We conclude that T1 weighted MT MR imaging appears to be more consistent in the tissue characterization of brain tuberculomas.     

MR imaging findings in mild traumatic brain injury with persistent neurological impairment

Traumatic brain injury (TBI) is a widespread cause of neurologic disability, with > 70% of cases being mild in severity. Magnetic resonance imaging provides objective biomarkers in the diagnosis of brain injury by detecting brain lesions resulting from trauma. This paper reports on the detection rates of presumed trauma-related pathology using fluid-attenuated inversion recovery (FLAIR) and susceptibility-weighted imaging (SWI) in TBI patients with chronic, persistent symptoms. Methods: 180 subjects with persistent neurobehavioral symptoms following head trauma referred by personal injury attorneys and 94 asymptomatic, age-matched volunteers were included in the study. 83% of TBI subjects were classified as mild. Results: TBI subjects had a significantly greater number of lesions detected by FLAIR than controls (42% vs. 22%) and more lesions detected by SWI than controls (28% vs. 3%). To reduce the confounding effects of aging, we examined mild TBI subjects < 45 years of age, which reduced the rate of lesions detected by FLAIR (26% vs. 2%) and SWI (15% vs. 0%). This younger group, which contained few age-related lesions, also demonstrated that subcortical lesions on FLAIR are more specific for TBI than deeper lesions. Conclusions: While the presence of litigation in mild TBI cases with incomplete recovery has been associated with greater expression of symptomatology and, by extension, poorer outcomes, this study shows that mild TBI patients in litigation with chronic, persistent symptoms may have associated brain injury underlying their symptoms detectable by MRI biomarkers.     

Cerebral mucormycosis: proton MR spectroscopy and MR imaging

Proton magnetic resonance spectroscopy (MRS) was integrated with magnetic resonance imaging (MRI) in the evaluation of a case of cerebral mucormycosis. MRS showed markedly elevated lactate, depleted N-acetyl aspartate and metabolite resonances attributable to succinate and acetate. The spectroscopy profile is essentially similar to that of bacterial abscess but without the commonly seen resonances of the amino acids valine, leucine and isoleucine. Our extensive literature review did not yield any reports of MRS findings on cerebral mucormycosis. MRS prospectively limited the differential diagnoses given the otherwise nonspecific and complex MR imaging findings in our immunosuppressed patient.     

Laser Raman spectroscopy of the effect of solvent on the low-frequency oscillations of organic molecules

The effect of solvent on low-frequency oscillations is studied using an example of the 1,1,2,2-tetrachloroethane (TCE) and 1,1,2,2-tetrabromoethane (TBE) molecules, which exhibit torsional oscillations in the terahertz range. Dimethylsulfoxide (DMSO) and carbon tetrachloride (CTC) are used as solvents. It is demonstrated that a decrease in the concentration of the substance under study in the TBE/CTC, TCE/DMSO, and TCE/CTC mixtures leads to a frequency shift of the low-frequency oscillation. The shift is not observed in the TBE/DMSO mixture but a decrease in the TBE concentration causes significant broadening of the low-frequency line.     

Renal replacement lipomatosis: MR findings in one case

Replacement lipomatosis of the kidney is the result of severe atrophy or destruction of the renal parenchyma, often caused by calculous disease with secondary marked proliferation of renal sinus, renal hilus, and perirenal fatty tissue. Different diagnostic tools have been used to define this entity, with ultrasonography (US), i.v. pyelography (IVP) and computed tomography (CT) used most commonly. We report MR urography and MR appearance of replacement lipomatosis in a 38-year-old man. We think that it combines the advantages of IVP, US and CT.     

Fluorescence spectroscopy of aminobenzenes in solvent mixtures

The shifts of the fluorescence spectra of aniline (A), N-methyl-A and N,N-dimethyl-A in mixtures of cyclohexane and tetrahydrofuran, 1-butanol or 1,4-dioxan differ only because of the molecular volumes of the amines and not because of their excited-state hydrogen-bonding properties.     

A case of Budd-Chiari syndrome: Gd-EOB-DTPA-enhanced MR findings

Budd-Chiari syndrome (BCS) is a rare disorder caused by the obstruction of hepatic venous outflow, leading to sinusoidal congestion, ischemic injury to liver cells and portal hypertension. Long-term survival largely depends on whether hepatocellular carcinoma occurs. A recently available liver-specific contrast medium, gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA), reportedly has high diagnostic capability for detection of malignant liver tumors. However, there has been no report of the sue of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) for BCS. We present a case of chronic BCS who underwent both gadopentetate dimeglumine (Gd-DTPA) and Gd-EOB-DTPA-enhanced MRI. Hepatic congestion and edema were seen as slightly hypointense areas on Gd-EOB-DTPA-enhanced hepatobiliary-phase images, although these areas were observed as slightly hyperintense on previously obtained Gd-DTPA-enhanced delayed-phase image. Reduced uptake of Gd-EOB-DTPA by hepatocytes in the region of congestion or edema may account for this difference, which should be recognized in image interpretations.     

Cavernous hemangioma of the adrenal gland: MR findings

Adrenal hemangioma is considered a rare tumor and is pathologically similar to hemangiomas found elsewhere in the body. Magnetic resonance imaging (MRI) findings thought to be highly suggestive of this neoplasm are presented. Correlation with pathologic findings in this case, as well as imaging and pathologic findings in other reported cases, is provided.     

Single-voxel proton MR spectroscopy in toluene abuse

Inhalation of toluene, which is an organic solvent, causes toxic encephalopathy characterized by cognitive impairment, cerebellar and extra-pyramidal symptoms. We studied cranial MR images and single-voxel MR spectroscopy of 22 toluene abusers and age-matched control subjects. The mean age of the abusers and mean duration of abuse were 18,1 years and 47 months, respectively. We got three MR spectra from the centrum semiovale, cerebellum and thalamus by using STEAM sequence with a TE value of 30 ms. N-acetyl aspartate (NAA)/Creatine (Cr), Choline (Cho)/Cr, myo-inositol (mI)/Cr peak integral ratios were calculated. NAA/Cr in the cerebellum and centrum semiovale of the abusers were significantly lower than those of the control subjects. mI/Cr in centrum semiovale and cerebellum were higher in toluene abusers. No significant difference was found in the metabolite ratios of the thalami. The association of NAA/Cr and mI/Cr ratios in cerebellum and centrum semiovale with the duration of abuse was significant. Normal level of NAA in thalamus, which was a neuron rich gray matter structure, might imply that toluene inhalation did not cause direct neuronal injury. Selective reduction of NAA and increased level of mI in white matter supported the theory of that axonopathy and gliosis were the main mechanisms of pathophysiology in chronic toluene encepholopathy. Insignificance of elevation of Cho/Cr ratios demonstrated that toluene inhalation did not cause active demyelination.     

Renal cell carcinoma in a transplanted kidney: MR imaging findings

We report the MR findings of a 42-year-old man who developed renal cell carcinoma in an allograft kidney, 10 years after transplantation. The lower pole of the transplant kidney showed a solid lesion which was well shown on the post gadolinium fat suppressed images as a heterogeneously enhancing 2 cm mass lesion.     

Occupational exposure limits for nanomaterials: state of the art

Assessing the need for and effectiveness of controlling airborne exposures to engineered nanomaterials in the workplace is difficult in the absence of occupational exposure limits (OELs). At present, there are practically no OELs specific to nanomaterials that have been adopted or promulgated by authoritative standards and guidance organizations. The vast heterogeneity of nanomaterials limits the number of specific OELs that are likely to be developed in the near future, but OELs could be developed more expeditiously for nanomaterials by applying dose–response data generated from animal studies for specific nanoparticles across categories of nanomaterials with similar properties and modes of action. This article reviews the history, context, and approaches for developing OELs for particles in general and nanoparticles in particular. Examples of approaches for developing OELs for titanium dioxide and carbon nanotubes are presented and interim OELs from various organizations for some nanomaterials are discussed. When adequate dose–response data are available in animals or humans, quantitative risk assessment methods can provide estimates of adverse health risk of nanomaterials in workers and, in conjunction with workplace exposure and control data, provide a basis for determining appropriate exposure limits. In the absence of adequate quantitative data, qualitative approaches to hazard assessment, exposure control, and safe work practices are prudent measures to reduce hazards in workers.