Biomedical subjects

Adam D Waldman

Publications and source records attributed to Adam D Waldman.

7 recordsLinked to original sources

PubMed2007

Quantitative analysis of whole-tumor Gd enhancement histograms predicts malignant transformation in low-grade gliomas.

PURPOSE: To quantify subtle gadolinium (Gd) enhancement (signal increase) in whole-tumor histograms and optimize their ability to predict subsequent malignant transformation in low-grade gliomas (LGGs). MATERIALS AND METHODS: We analyzed histograms from 21 adult subjects with LGGs (eight nontransformers and 13 transformers) who had been imaged every six months for periods of two to five years. Before transformation these tumors were reported as radiologically non-enhancing. Imaging included a T(1)-weighted volume sequence before and after a double dose of Gd-DTPA contrast agent. Image data sets were spatially registered and subtracted to obtain maps of percent enhancement (%E). Tumor outlines were defined on fluid-attenuated inversion recovery (FLAIR) images, and the volumes were calculated. Histogram tails were analyzed to obtain the volume (mL) of subtly enhancing tissue (%E > 10%). RESULTS: Baseline enhancing volumes were higher for Ts than for NTs (P < 0.005). Kaplan-Meier survival curves for a threshold of 4 mL showed clear differences at five years (P < 0.04). Pretransformation examinations predicted transformation (corrected threshold = 3.0 mL, P = 0.011). CONCLUSION: Clear histogram differences at presentation suggest that the process of transformation starts very early. It is now possible to identify individuals at high risk for transformation at baseline by quantifying the volume of subtly enhancing tumor tissue, and such findings could have an impact on patient management.

Adult↗

PubMed2007

Apparent diffusion coefficient histograms may predict low-grade glioma subtype.

The subtypes of glioma are known to have different prognosis and response to treatment. The purpose of this work was to investigate whether apparent diffusion coefficient (ADC) histograms of untreated low-grade astrocytomas and oligodendrogliomas exhibit different characteristics due to their biological differences, and whether a diagnosis of tumour subtype can be made at presentation using the histogram alone, which, if possible, would have an impact on clinical practise. Fifteen patients with astrocytoma (AC) [11 male (mean age +/- standard deviation) 40 +/- 11 years], nine with oligodendroglioma (OD) (four male, 45 +/- 13 years) and three with oligoastrocytoma (OA) (two male, 60 +/- 11 years) were recruited and diffusion-weighted images (b = 0 and 1000 s mm(-2)) were acquired every 6 months to date or until malignant transformation. Whole tumour ADC histograms were calculated, a multiple discriminant analysis was performed and quantitative morphological parameters extracted, the AC and OD subtypes were then compared using Student's unpaired t-test. Classification of the histograms was also performed. ODs had significantly lower group ADC values than ACs and up to 83% of the subjects could be correctly classified into the OD and AC groups by reference to the histogram. The group differences were most significant for the multiple discriminant analysis (p = 1 x 10(-5)) and at the 10th centile point [AC = 1170 +/- 170, OD = (1030 +/- 80) x 10(-6) mm(2) s(-1)] (p = 0.01). ODs have a lower ADC than ACs with differences throughout the histogram. Both tumour types show similar intra-tumour heterogeneity, as seen from the equal group peak heights, but ACs shows more intra-group heterogeneity. ADC histogram analysis may aid non-invasive sub-classification of low-grade glioma histological subtypes.

Adult↗

PubMed2006

Posterior cingulate neurometabolite profiles and clinical phenotype in frontotemporal dementia.

Proton magnetic resonance spectroscopy was used to compare metabolite levels from a posterior cingulate voxel in a group of patients with 2 syndromic subtypes of frontotemporal dementia (n=10) and an age and education-matched group with Alzheimer disease (n=10). Overall, frontotemporal dementia was indistinguishable from Alzheimer disease, though differences in N-acetylaspartate emerged between patients with the SD and progressive nonfluent aphasia subtypes, attributable to 2 atypical results among the latter. Such values may index cases with atrophy in posterior cortical regions presenting with progressive nonfluent aphasia.

Aged↗

PubMed2005

Visual assessment of atrophy on magnetic resonance imaging in the diagnosis of pathologically confirmed young-onset dementias.

OBJECTIVES: To investigate the diagnostic accuracy of visual inspection of magnetic resonance imaging (MRI) in a range of pathologically confirmed diseases causing young-onset dementia and to assess the sensitivity and specificity of atrophy patterns for Alzheimer disease (AD) and frontotemporal lobar degeneration (FTLD). DESIGN: Sixty-two patients with pathologically confirmed diseases that may present as young-onset dementia were selected from a biopsy and postmortem series. The first diagnostic T1-weighted volumetric MRI was obtained for each patient, together with images from 22 healthy control subjects. All MRIs were assessed for regional atrophy independently by 3 neuroradiologists, blinded to all clinical details except age. Observers were also asked to use their clinical judgment to form a diagnosis. RESULTS: Eighty-seven percent of dementia cases were distinguished from controls after visual inspection of MRI, and a correct pathologically confirmed diagnosis was given in 58% of cases. Hippocampal atrophy was noted in 92% of AD cases but was commonly seen in other dementias and controls. A bilateral symmetrical pattern of hippocampal atrophy discriminated AD from FTLD with 47% specificity, while posterior greater than anterior gradient of atrophy was 92% specific for AD. Atrophy of the anterior, inferior, and lateral temporal lobes was suggestive of FTLD pathology (> or =90% sensitivity), while anterior greater than posterior gradient of atrophy and hemispheric asymmetry of atrophy were each at least 85% specific for FTLD. CONCLUSION: Despite variation and overlap of atrophy patterns, visual inspection of regional atrophy on MRI may aid in discriminating AD and FTLD.

Aged↗

PubMed2005

Differential chemosensitivity of tumor components in a malignant oligodendroglioma: assessment with diffusion-weighted, perfusion-weighted, and serial volumetric MR imaging.

We report the case of malignant oligodendroglioma in a 36-year-old man who underwent diffusion-weighted, perfusion-weighted, and volumetric MR imaging before and after PCV (procarbazine, CCNU, vincristine) chemotherapy. The tumor regions exhibiting a low apparent diffusion coefficient and increased relative cerebral blood volume showed a marked response to chemotherapy and dramatic decrease in volume, whereas the remaining tumor regions showed little change. Diffusion-weighted and perfusion-weighted MR imaging may be helpful in predicting chemosensitivity of glial tumors.

Adult↗

PubMed2004

1H-MRS evaluation of metabolism in Alzheimer's disease and vascular dementia.

Proton magnetic resonance spectroscopy (1H-MRS) allows major metabolites to be measured noninvasively in defined regions of the living brain, and can detect biochemical abnormalities where conventional structural imaging appears normal. MRS can be performed in 10 min as part of a clinical MRI examination. Biochemical abnormalities in Alzheimer's Disease (AD), vascular dementia (VaD) and other primary degenerative dementias have been investigated using MRS. Characteristic and consistent abnormalities in AD are decreased N-acetyl aspartate (NAA) and elevated myo-inositol (mI) in the mesial temporal and parieto-occipital cortex. These are thought to represent neuronal loss/dysfunction and gliosis, in anatomic distributions which reflect early pathological involvement and atrophy patterns in AD. Less consistent disturbances of glutamine and glutamate (Glx) and choline-containing compounds (Cho) have also been reported. Similar changes are seen in VaD; mostly in white matter, whereas in AD they predominate in cortical grey matter. The regional distribution of grey matter involvement may differ between AD and other degenerative dementias. Hence, both the nature and anatomic distribution of metabolite abnormalities contribute to diagnostic discrimination with MRS. NAA/mI ratios from short echo time spectra of the posterior cingulate region cortex discriminate reliably between AD subjects, normal individuals and those with VaD, and provides a useful clinical test, as an adjunct to structural imaging. Elevated mI is detected in mild cognitive impairment (MCI) and quantitative metabolite measures correlate with degrees of cognitive impairment in AD; these suggest a possible role for MRS in early diagnosis and for surrogate biochemical markers for monitoring disease progression and therapeutic response.

Acetylcholine↗

PubMed2003

Rapid echoplanar diffusion imaging in a case of variant Creutzfeldt-Jakob disease; where speed is of the essence.

Neuroimaging with magnetic resonance imaging (MRI) is important in the diagnosis of Creutzfeldt-Jakob disease (CJD), but is frequently frustrated by patient movement. Diffusion-weighted imaging (DWI) has previously shown markedly restricted diffusion in grey matter structures of patients with CJD, and may add to diagnostic sensitivity. Echoplanar imaging (EPI) sequences, which are usually used for DWI, are also very rapid, and typically allow imaging of the whole brain in less than 1 min. A case of histologically proven variant CJD (vCJD) in which conventional MRI was difficult to interpret confidently owing to motion artefact, but EPI was diagnostic, emphasises the utility of rapid imaging in agitated patients. Comparison of the regional quantitative apparent diffusion coefficient (ADC) with a control group ( n=5) showed restricted diffusion in the caudate (vCJD: 0.63 x 10(-3) mm(2)/s; controls: mean 0.722 x 10(-3) mm(2)/s, SD 0.017) and lentiform (vCJD: 0.65 x 10(-3) mm(2)/s; controls: mean 0.707 x 10(-3) mm(2)/s, SD 0.011) nuclei. T2 effects dominated the signal abnormality on DWI in the pulvinar; ADC was increased (vCJD: 0.87-0.95 x 10(-3) mm(2)/s; controls: mean 0.773 x 10(-3) mm(2)/s, SD 0.038). Our data emphasise variation in diffusion patterns in vCJD, and illustrate the value in using all the components available from the DWI examination for maximum diagnostic information. EPI-DWI provides both rapid T2- and diffusion-dependent information, and is recommended for those patients in whom confusion and agitation is likely to confound standard MRI protocols.

Adult↗