MRI of late microstructural and metabolic alterations in radiation‐induced brain injuries

Purpose

To evaluate the late effects of radiation‐induced damages in the rat brain by means of in vivo multiparametric MRI.

Materials and Methods

The right hemibrains of seven Sprague‐Dawley rats were irradiated with a highly collimated 6 MV photon beam at a single dose of approximately 28 Gy. Diffusion tensor imaging (DTI), proton MR spectroscopy (¹H‐MRS), T2‐weighted imaging, and T1‐weighted imaging were performed to the same animals 12 months after radiation treatment.

Results

Compared with the contralateral side, a significantly higher percentage decrease in fractional anisotropy was observed in the ipsilateral fimbria of hippocampus (29%) than the external capsule (8%) in DTI, indicating the selective vulnerability of fimbria to radiation treatment. Furthermore, in ¹H‐MRS, significantly higher choline, glutamate, lactate, and taurine peaks by 24%, 25%, 87%, and 58%, respectively, were observed relative to creatine in the ipsilateral brain. Postmortem histology confirmed these white matter degradations as well as glial fibrillary acidic protein and glutamine synthetase immunoreactivity increase in the ipsilateral brain.

Conclusion

The microstructural and metabolic changes in late radiation‐induced brain injuries were documented in vivo. These multiparametric MRI measurements may help understand the white matter changes and neurotoxicity upon radiation treatment in a single setting. J. Magn. Reson. Imaging 2009;29:1013–1020. © 2009 Wiley‐Liss, Inc.     

Unusual features of gastrointestinal stromal tumor on PET/CT and CT imaging

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. It can be benign or malignant in behavior. Stomach, being the most common site (70%) for GISTs, is followed by the small intestine (20%). Anorectal, colonic, and esophageal GISTs are uncommon, whereas extraintestinal GISTs are extremely rare. The presenting symptoms are highly dependent on tumor size and location, although a large number of GISTs are asymptomatic. The purpose of this article is to highlight the unusual characteristics of GISTs illustrated by PET/CT and CT imaging. These characteristics are organized into (1) unusual tumor location, (2) unusual clinical presentation, and (3) unusual sites of metastasis. Knowing the uncommon features of GISTs is important, as they are more often seen nowadays with the increasingly important role of PET/CT and CT in GIST management; and these tumors are associated with a poorer prognosis and unwanted delay in diagnosis is avoidable. With the availability of effective treatment by imatinib mesylate, a prompt and early diagnosis is essential for disease control. All GISTs illustrated in this article are pathologically proven.     

Late-onset pediatric glaucoma associated with cutis marmorata telangiectatica congenita managed with Molteno implant surgery: case report and review of the literature.

Cutis marmorata telangiectatica congenita (CMTC) is characterized by the appearance of telangiectasia, phlebectasia, and a persistent reticular pattern of subcutaneous vasculature at or soon after birth. Up to 90% of cases are associated with systemic abnormalities, which include body asymmetry, cutaneous atrophy, neurological abnormalities, and vascular anomalies (nevus flammeus, Sturge-Weber syndrome, Klippel-Trenaunay syndrome, and capillary and cavernous hemangiomas). Glaucoma is the most commonly reported ocular association of CMTC, usually presenting in infancy. We report a case of CMTC associated with the previously unreported onset of glaucoma in mid-childhood that was managed by glaucoma drainage implant surgery and review the literature on glaucoma associated with this condition.     

Solid-cystic papillary tumor of the pancreas in children

Solid-cystic papillary tumor (SCPT) of the pancreas is a rare neoplasm in children. The current study attempted to estimate the incidence and possible pathological origin of the tumor. Clinicopathologic features of the children under the age of 16 years with pancreatic tumors managed in a single institution between January 1993 and November 1999 were reviewed. Representative blocks of SCPT specimens were immunostained for neuron-specific enolase (NSE) chromogrannin, synaptophysin, insulin, glucagon, somatostatin, and gastrin. There were three SCPTs, two pancreatic endocrine tumors, and one acinar cell carcinoma during the study period. The estimated yearly incidence in the referral area of 2 million population is about 0.01 pediatric SCPT per year per 100,000 population. The children underwent surgical removal of the tumors. Postoperatively, they were followed up for 6 months to 4 years and were well. Immunostaining for NSE, chromogranin, synaptophysin, insulin, somatostatin, and gastrin was negative in all cases. SCPT may thus be the most common pancreatic tumor in the Asian pediatric population. The pathological origin of the tumor remains unclear and requires further investigations. Accepted: 30 October 2000     

Childhood acute disseminated encephalomyelitis: the role of brain and spinal cord MRI

BACKGROUND: It is recognised that the clinical and radiological spectrum of childhood acute disseminated encephalomyelitis (ADEM) is wide. OBJECTIVE: To determine whether initial MRI features are predictive of clinical outcome and to determine the role of MRI in the management of ADEM. MATERIALS AND METHODS: The MRI scans of ten consecutive children (eight boys, two girls), clinically and radiologically diagnosed to have ADEM, were retrospectively reviewed. Follow-up MRI was available for eight patients. RESULTS: Lesions ranged from small and punctate (<1 cm) to moderate sized and confluent (4-5 cm) to diffuse and extensive. Spinal cord lesions, seen in five of seven children, were contiguous or segmental. Seven children (70%) made good clinical recovery while three children (30%) remained severely handicapped. There was no correlation between the site, extent and pattern of involvement and clinical outcome. However, the evolution of MRI findings on follow-up correlated well with the subsequent clinical course and outcome. CONCLUSIONS: Although the extent and site of lesions on initial MRI scans are not predictive of clinical outcome, early MRI of the brain and spine is useful in aiding clinical diagnosis, and subsequent follow-up MRI is helpful in monitoring disease progression.     

INVESTIGATING COMMUNITY PERSPECTIVES ON FALLS PREVENTION INFORMATION SEEKING AND DELIVERY: OLDER PERSON PERCEPTIONS REGARDING PREFERENCES FOR FALLS PREVENTION EDUCATION USING A WORLD CAFE APPROACH

Falls among older people are a significant global socioeconomic problem, and older adults have low levels of self‐perceived risk and a lack of willingness to take up existing falls prevention strategies. We believe that given the challenges of delivering falls prevention information, meaningful engagement of community members would create solutions based on an understanding of what would work best for that community. A World Cafe community forum sought the opinions of 70 community‐dwelling older people about their preferences on how they would best receive and seek falls prevention information that could prevent falls within their age group. Participants evaluated the café as a highly positive experience and felt that learning occurred by way of interaction and “sharing of ideas.” Local communities could develop this participatory approach to engage older people in leading the translation of falls prevention evidence into practice.     

Parvovirus as a cause of hydrops fetalis: detection by in situ DNA hybridisation.

Lung tissue from 13 cases of unexplained non-immunological hydrops fetalis was examined by in situ hybridisation to detect parvovirus. Four specimens contained parvovirus DNA in cells in the blood vessel lumina and alveoli. Twenty six control cases were negative for parvovirus DNA. As there was no known epidemic of parvovirus infection during the study period, this suggests that parvovirus is a relatively common cause of non-immunological hydrops fetalis. In situ hybridisation may have a role in clinical medicine, particularly for retrospective investigations.     

Late measures of microstructural alterations in severe neonatal hypoxic–ischemic encephalopathy by MR diffusion tensor imaging

Neonatal hypoxic–ischemic encephalopathy is a major cause of brain damage in infants, and is associated with periventricular white matter injury and chronic neurological dysfunctions. However, the mechanisms of the chronic white matter injury and reorganization are still unclear. In this study, in vivo diffusion tensor imaging (DTI) was employed to evaluate the late changes of white matter microstructural integrity in the rat brains at 10 weeks after severe neonatal hypoxic–ischemic insults at postnatal day 7. In the fractional anisotropy directionality map, qualitative evaluation showed that a dorsoventrally oriented fiber bundle extended from the corpus callosum into the cyst in the anterior brain, whilst the posterior peri-infarct areas had similar fiber orientations as the contralateral internal capsule, optic tract and fimbria of hippocampus. Compared to the contralateral hemisphere, significantly higher fractional anisotropy, axial diffusivity and diffusion trace value were observed quantitatively in the distal end of the extended fiber bundle connecting the anterior and posterior white matters rostrocaudally. A significantly lower fractional anisotropy but higher axial and radial diffusivities and trace were also found in the ipsilateral corpus callosum, proximal external capsule and anterior commissure, while slightly lower fractional anisotropy and axial diffusivity were noticed in the ipsilateral internal capsule and optic nerve. It was suggested that increased fractional anisotropy, axial diffusivity and trace characterize white matter reorganization in chronic neonatal hypoxic–ischemic insults, whereas reduction in fractional anisotropy appears to characterize two types of white matter lesions, with significantly higher axial and radial diffusivities and trace being primary and slightly lower axial diffusivity being secondary. Combined with fractional anisotropy directionality map, in vivo DTI provides important indices to differentiate the chronic effects of severe neonatal hypoxic–ischemic injury and recovery globally, quantitatively and non-invasively.     

Diffusion-weighted imaging and proton magnetic resonance spectroscopy in perinatal hypoxic-ischemic encephalopathy: association with neuromotor outcome at 18 months of age

We evaluated early diffusion-weighted imaging findings, the quantitative apparent diffusion coefficient, and magnetic resonance spectroscopy (the presence of lactate and ratios of N-acetylaspartate to total creatine and choline to total creatine) in the prediction of the 18-month neuromotor outcome of term newborns with hypoxic-ischemic encephalopathy. Conventional T1- and T2-weighted and diffusion-weighted imaging was performed in 20 asphyxiated term newborns, with additional basal ganglia magnetic resonance spectroscopy in 15 newborns between 2 and 18 days of life (mean 7.3 days). Neuromotor outcome was dichotomized into normal and abnormal for statistical analysis. Statistically significant differences in the ratios of N-acetylaspartate to total creatine, but not apparent diffusion coefficient values and ratios of choline to total creatine, were found between infants with a normal and an abnormal outcome (Mann-Whitney U-test, P = .010). There was a significant association between the presence of a lactate peak and an abnormal outcome (chi-square test, P = .017). The presence of a lactate peak for predicting an abnormal outcome had a sensitivity of 100% and a specificity of 80%, and the odds ratio was 37.4. Ischemic lesions were more conspicuous and/or extensive on diffusion-weighted imaging in all except one neonate. The presence of normal findings on both diffusion-weighted imaging and conventional magnetic resonance imaging is predictive of a normal neuromotor outcome, whereas lactate and a reduced ratio of N-acetylaspartate to total creatine in the basal ganglia, but not an apparent diffusion coefficient, are associated with an abnormal outcome at 18 months of age.     

Comparing diffusion-weighted and T2-weighted MR imaging for the quantification of infarct size in a neonatal rat hypoxic–ischemic model at 24 h post-injury

PURPOSE: In a neonatal rat model of hypoxic-ischemic (HI) brain injury, using T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI), we aim to determine the best MRI method of lesion quantification that reflects infarct size. MATERIALS AND METHODS: Twenty 7-day-old rats underwent MRI 24h after HI brain injury was induced. Lesion size relative to whole brain was measured using T2WI and apparent diffusion coefficient (ADC) maps, applying thresholds of 60%, 70% and 80% contralateral control hemisphere mean ADC, and at day 10 post-HI on pathology with TTC staining. Multiple linear regression analysis was used to study the relationships between lesion size at MRI and pathology. RESULTS: Lesion size measurement using all MRI methods significantly correlated with infarct size at pathology; using T2WI, r=0.808 (p<0.001), using 80% ADC, 70% ADC and 60% ADC thresholds, r=0.888 (p<0.001), 0.761, (p<0.001) and 0.569 (p=0.014), respectively. Eighty percent ADC threshold was found to be the only significant independent predictor of final infarct volume (adjusted R(2)=0.775). CONCLUSION: At 24h post-HI, lesion size on DWI, using 80% ADC threshold is the best predictor of final infarct volume. Although T2WI performed less well, it has the advantage of superior spatial resolution and is technically less demanding. These are important considerations for experiments which utilize MRI as a surrogate method for lesion quantification in the neonatal rat HI model.