Signal-to-noise and contrast in fast spin echo (FSE) and inversion recovery FSE imaging.

Fast spin echo (FSE) imaging has recently experienced a renewed enthusiasm in the clinical setting for its ability to provide high contrast T2-weighted images in short imaging times. This article evaluates the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) properties of the FSE sequence, inversion recovery (IR) FSE sequence, and conventional SE imaging. The results indicate that FSE imaging displays similar contrast properties to SE imaging, but that the SNR and CNR are improved secondary to the longer TRs and longer effective TEs that may be used. The SNR per unit time of the FSE sequence, and hence its efficiency, is at least a factor of 8 better than the SE sequence when 16 echoes are acquired for each excitation. The addition of a slice selective inversion pulse in IR-FSE allows rapid generation of IR images with image contrast similar to that of conventional IR sequences. When used with a multicoil array for abdominal, pelvic, and spine imaging, the IR-FSE sequence produces images that are virtually free of motion artifact from the subcutaneous fat immediately adjacent to the coils. Both FSE and IR-FSE, when compared with SE imaging, provide superior image contrast and SNR in reduced imaging time.     

Surfactant phosphatidylcholine composition during dexamethasone treatment in chronic lung disease

Objectives - To determine whether dexamethasone `matures' the phosphatidylcholine (PC) composition of broncheoalveolar fluid in infants at high risk of neonatal chronic lung disease (CLD), either by increasing the proportion of dipalmitoylphosphatidylcholine (DPPC), expressed as a percentage of total PC (%DPPC), or by increasing the ratio of DPPC to palmitoyloleoylphosphatidylcholine (DPPC:POPC ratio).     

Mortality studies of machining fluid exposure in the automobile industry III: A case-control study of larynx cancer

A case-control study of larynx cancer was conducted within a cohort of automobile workers exposed to metal working fluids, commonly referred to as machining fluids (MF). Results are based on 108 cases of larynx cancer and 5:1 matched controls. Risks associated with specific types of MF, as well as specific components of the fluids were evaluated. Based on a retrospective exposure assessment, lifetime exposures to straight and soluble fluids, grinding particulate, biocides, selected metals, sulfur, and chlorine were examined. Exposure to asbestos and acid mists at two of the three study sites was also characterized. Results suggest that straight mineral oils are associated with almost a two-fold excess in larynx cancer risk. There was also evidence of an association with elemental sulfur, commonly added to straight MF to improve the integrity of the materials under extreme pressure and heat. It is not clear whether sulfur is causally related to an excess relative risk of larynx cancer or whether the observed association is the result of unmeasured confounding by another contaminant or process feature. For example, the high stress operations that require MF enriched with sulfur are also more likely to produce polycyclic aromatic hydrocarbons (PAHs) during the process. Thus, the observed association with sulfur may be due to an association with PAH. The finding of excess risk of laryngeal cancer associated with MF is consistent with several previous reports in the literature. This is the first study, however, to distinguish straight mineral oils from other types of MF. Based on these findings, a general reduction in concentrations of straight mineral oil particulate in occupational environments would be prudent.     

Evaluating risk adjustment by partitioning variation in hospital mortality rates

The variation in mortality rates among hospitals has often been described informally as having three major components: patient severity, quality of care and random variation. These informal concepts are characterized formally by partitioning sums of squares and finding their expected values. The partition relates to commonly used tests for whether individual hospitals have unusual mortality rates. Application of the partition to the hospital mortality reports by the Health Care Financing Administration shows that their models for patient risk account for about one-half the variation among hospital mortality rates. An example using clinical measures of severity accounts for about two-thirds of mortality variation among hospitals.     

Molecular genetics and cytogenetics--a glossary and list of abbreviations.

A glossary of terms commonly used in molecular genetics and cytogenetics has been prepared to assist pathologists. The emphasis is on clinically relevant examples.     

Association of atrophy of the medial temporal lobe with reduced blood flow in the posterior parietotemporal cortex in patients with a clinical and pathological diagnosis of Alzheimer''s disease.

A combination of medial temporal lobe atrophy, shown by computed tomography, and reduced blood flow in the parietotemporal cortex, shown by single photon emission tomography, was found in 86% (44/51) of patients with a clinical diagnosis of senile dementia of the Alzheimer type (SDAT). The same combination of changes was found in four out of 10 patients with other clinical types of dementia and in two out of 18 with no evidence of cognitive deficit. Of the 12 patients who died, 10 fulfilled histopathological criteria for Alzheimer's disease, nine of them having a clinical diagnosis of SDAT, and one a clinical diagnosis of multi-infarct dementia. All 10 patients with histopathologically diagnosed Alzheimer's disease had shown a combination of hippocampal atrophy and reduced parietotemporal blood flow in life. In 10 patients (nine with SDAT) out of 12 in whom the hippocampal atrophy was more noticeable on one side of the brain than on the other the parietotemporal perfusion deficit was also asymmetrical, being greater on the side showing more hippocampal atrophy. These results suggest that the combination of atrophy of the hippocampal formation and reduced blood flow in the parietotemporal region is a feature of dementia of the Alzheimer type and that the functional change in the parietotemporal region might be related to the loss of the projection neurons in the parahippocampal gyrus that innervate this region of the neocortex.     

Lymphocyte proliferation and sister chromatid exchange in Alzheimer's disease.

Sister chromatid exchange (SCE) and lymphocyte proliferation were studied in peripheral lymphocyte cultures derived from 5 patients with Alzheimer disease (AD), 5 control elderly subjects and 5 young donors. These parameters did not differ significantly between the AD group and the elderly control group, but higher SCE frequency and less intensive proliferation were observed in the AD group and in the elderly control group when compared to the young donors.