Radiation Dose and Image Quality in Pediatric Neck CT.

BACKGROUND AND PURPOSE: Optimization of pediatric neck CT protocols is of critical importance in order to maintain good diagnostic image quality while reducing the radiation burden. Our aim was to evaluate the image quality of pediatric neck CT studies before and after the implementation of a low radiation dose protocol. MATERIALS AND METHODS: We retrospectively reviewed 179 pediatric neck CT studies, 75 before and 104 after the implementation of low-dose protocols, performed in children 0-16 years of age. The 2 cohorts were divided into 3 age groups, 0-4, 5-9, and 10-16 years. The signal-to-noise ratio was calculated using the axial image through the true vocal folds. Three neuroradiologists assessed the image quality of the same CT scan using a 5-point scoring system. We compared the CT dose index volume, dose-length product, image-quality ratings, and SNR of studies conducted at baseline and with low-dose protocols. RESULTS: Image-quality ratings were lower in the low-dose than in the baseline cohort in children 10-16 years of age, but not in children 0-4 and 5-9 years of age. The SNR was lower in the low-dose cohort than in the baseline cohort in children 0-4 and 10-16 years of age, but not in children 5-9 years of age. Despite the decrease in image-quality scores in older children, 97% of the studies (73/75) in the baseline cohort and 96% of studies (100/104) in the low-dose cohort were considered of sufficient image quality. CONCLUSIONS: Images acquired with the low-dose CT protocols were deemed to be of sufficient quality for making a clinical diagnosis. Our initial results suggest that there may be an opportunity for further radiation dose reduction without compromising diagnostic image quality using iterative reconstruction algorithms.

Surface Topography, Gloss and Flexural Strength of Pressable Ceramic After Finishing-Polishing Protocols.

This study evaluated the effect of different finishing-polishing protocols on surface roughness, gloss, morphology and biaxial flexural strength of pressable fluorapatite glass ceramic. Thirty ceramic discs (12x1 mm) were produced and divided into five groups (n=6): CT: control (glaze); DA: fine grit diamond bur; DG: DA + new glaze layer; DP: DA + felt disk with fine grit diamond paste; DK: DA+ sequential polishing with silicon abrasive instruments, goat hair brush and cotton wheel. The specimens were analyzed for surface roughness (Ra) under profilometry and atomic force microscopy (AFM). Gloss was measured with spectrophotometry and micromorphology with scanning electron microscopy (SEM). Flexural strength was assessed by biaxial flexural strength test. Data were analyzed using one-way ANOVA and Tukey's post hoc test (a=0.05). DK showed the lowest surface roughness values and DA presented the highest in the perfilometer analysis. No significant differences were observed in the AFM for the CT, DG and DK groups, which presented the lower surface roughness; DA and DP had the higher Ra values. The DA, DP and CT showed the lowest surface gloss values, and the reflectance was significantly different from those observed for DK and DG groups. SEM analysis revealed the smoothest surface for DK group, followed by DG and CT groups; DA and DP groups exhibited variable degrees of surface irregularities. No significant differences were observed among groups for the biaxial flexural strength. The polishing protocol used in DK group can be a good alternative for chairside finishing of adjusted pressable fluorapatite glass ceramic surfaces.

Surface topography, gloss and flexural strength of pressable ceramic after finishing-polishing protocols

Abstract This study evaluated the effect of different finishing-polishing protocols on surface roughness, gloss, morphology and biaxial flexural strength of pressable fluorapatite glass ceramic. Thirty ceramic discs (12x1 mm) were produced and divided into five groups (n=6): CT: control (glaze); DA: fine grit diamond bur; DG: DA + new glaze layer; DP: DA + felt disk with fine grit diamond paste; DK: DA+ sequential polishing with silicon abrasive instruments, goat hair brush and cotton wheel. The specimens were analyzed for surface roughness (Ra) under profilometry and atomic force microscopy (AFM). Gloss was measured with spectrophotometry and micromorphology with scanning electron microscopy (SEM). Flexural strength was assessed by biaxial flexural strength test. Data were analyzed using one-way ANOVA and Tukey's post hoc test (a=0.05). DK showed the lowest surface roughness values and DA presented the highest in the perfilometer analysis. No significant differences were observed in the AFM for the CT, DG and DK groups, which presented the lower surface roughness; DA and DP had the higher Ra values. The DA, DP and CT showed the lowest surface gloss values, and the reflectance was significantly different from those observed for DK and DG groups. SEM analysis revealed the smoothest surface for DK group, followed by DG and CT groups; DA and DP groups exhibited variable degrees of surface irregularities. No significant differences were observed among groups for the biaxial flexural strength. The polishing protocol used in DK group can be a good alternative for chairside finishing of adjusted pressable fluorapatite glass ceramic surfaces.

Resumo O objetivo deste estudo foi avaliar o efeito de diferentes protocolos de acabamento e polimento na rugosidade da superfície, brilho, resistência à flexão biaxial e morfologia de cerâmica prensada. Trinta discos de cerâmica (12x1 mm) foram produzidos e divididos em cinco grupos (n=6): CT- controle (glaze); DA- ponta diamantada de granulação fina; DG: DA + nova camada de glaze; DP: DA + disco de feltro com pasta de diamante de granulo fino; DK: DA + polimento sequencial com instrumentos abrasivos de silício, escova de cabra e roda de algodão. Os espécimes foram analisados quanto à rugosidade da superfície (Ra) sob profilometria e microscopia de força atômica (AFM). O brilho foi medido com espectrofotometria e a micromorfologia com microscopia eletrônica de varredura (SEM). A resistência à flexão foi avaliada pelo teste de resistência à flexão biaxial. Os dados foram analisados ​​usando ANOVA um fator e teste post hoc de Tukey (a=0,05). DK mostrou mais baixos valores de rugosidade da superfície e DA apresentou o maior na análise do perfilômetro. Não foram observadas diferenças significativas no AFM para os grupos CT, DG e DK, que apresentaram a menor rugosidade de superfície; DA e DP apresentaram os maiores valores Ra. O DA, DP e CT mostraram valores de brilho superficial mais baixos, e a reflectância foi significativamente diferente da observada para os grupos DK e DG. A análise de SEM revelou a superfície mais homogênea para o grupo DK, seguido de grupos DG e CT; Os grupos DA e DP exibiram graus variáveis de irregularidades da superfície. Não foram observadas diferenças significativas entre os grupos quanto à resistência à flexão biaxial. O protocolo de polimento utilizado no grupo DK pode ser uma boa alternativa para o acabamento em consultório das superfícies de cerâmicas prensadas após ajustes.

Antagonism of non-NMDA receptors in the dorsal periaqueductal grey induces anxiolytic effect in the elevated plus maze.

Microinjections of glutamate into the dorsal periaqueductal grey (DPAG) of rats induce flight behavior, and blockade of glutamate NMDA receptors in the same region increases exploratory behavior of rats tested on the elevated plus maze. To investigate a possible role of other glutamate receptors in the DPAG on anxiety modulation, rats (n = 6-10) received microinjections into this structure of CNQX (1 and 3 nmol/0.5 microl), an AMPA/kainate antagonist, or GDEE (80 or 160 nmol/0.5 microl), a non-selective glutamate antagonist, and were tested on the elevated plus-maze, an ethologically based animal model of anxiety. Both drugs increased the percentage of entries into open arms, as compared to rats receiving vehicle, without changing the number of enclosed arm entries. Injections of the active compounds outside the DPAG were not effective. The anxiolytic effect of CNQX (3 nmol/0.5 microl) was not reversed by glycine (10 nmol/0.5 microl), injected into the DPAG 5 min after CNQX administration. These results suggest that, in addition to NMDA receptors, non-NMDA glutamate receptors may also modulate anxiety in the DPAG.

Behavioral effects of "vehicle" microinjected into the dorsal periaqueductal grey of rats tested in the elevated plus maze.

To investigate the behavioral effects of different vehicles microinjected into the dorsal periaqueductal grey (DPAG) of male Wistar rats, weighing 200-250 g, tested in the elevated plus maze, animals were implanted with cannulas aimed at this structure. One week after surgery the animals received microinjections into the DPAG of 0.9% (w/v) saline, 10% (v/v) dimethyl sulfoxide (DMSO), 2% (v/v) Tween-80, 10% (v/v) propylene glycol, or synthetic cerebrospinal fluid (CSF). Ten min after the injection (0.5 microliters) the animals (N = 8-13/group) were submitted to the elevated plus maze test. DMSO significantly increased the number of entries into both the open and enclosed arms when compared to 0.9% saline (2.7 +/- 0.8 and 8.7 +/- 1.3 vs 0.8 +/- 0.3 and 5.1 +/- 0.9, respectively. Duncan test, P < 0.05), and tended to increase enclosed arm entries as compared to 2% Tween-80 (8.7 +/- 1.3 vs 5.7 +/- 0.9, Duncan test, P < 0.10). In a second experiment no difference in plus maze exploration was found between 0.9% saline-or sham-injected animals (N = 11-13/group). These results indicate that intra-DPAG injection of some commonly used vehicles such as DMSO, saline or Tween-80 affects the exploratory activity of rats exposed to the elevated plus maze in statistically different manners.

Behavioral effects of "vehicle" microinjected into the dorsal periaqueductal grey of rats tested in the elevated plus maze

To investigate the behavioral effects of different vehicles microinjected into the dorsal periaqueductal grey (DPAG) of male Wistar rats, weighing 200-250 g, tested in the elevated plus maze, animals were implanted with cannulas aimed at this structure. One week after surgery the animals received microinjections into the DPAG of 0.9 per cent (w/v) saline, 10 per cent (v/v) dimethyl sulfoxide (DMSO), 2 per cent (v/v) Tween-80, 10 per cent (v/v) propylene glycol, or synthetic cerebrospinal fluid (CSF). Ten min after the injection (0.5 mul) the animals (N = 8-13/group) were submitted to the elevated plus maze test. DMSO significantly increased the number of entries into both the open and enclosed arms when compared to 0.9 per cent saline (2.7 ñ 0.8 and 8.7 ñ 1.3 vs 0.8 ñ 0.3 and 5.1 ñ 0.9, respectively, Duncan test, P<0.05), and tended to increase enclosed arm entries as compared to 2 per cent Tween-80 (8.7 ñ 1.3 vs 5.7 ñ 0.9, Duncan test, P

Anxiolytic effect of glycine antagonists microinjected into the dorsal periaqueductal grey.

To investigate if blockade of the modulatory glycine site of NMDA receptors in the dorsal periaqueductal grey (DPAG) would produce anxiolytic effects, groups of 9-14 rats received microinjections into this structure of 7-chloro-kynurenic acid (7-Cl-KY, 4 and 8 nmol) or 3-amino-1-hydroxypyrrolid-2-one (HA-966, 30 or 100 nmol), two selective antagonists at the strychnine-insensitive glycine modulatory site, and were submitted to the elevated plus-maze, an ethologically based animal model of anxiety. Both drugs increased the percentage of entries and of time spent in open arms as compared to rats receiving isotonic saline. Injections of the active compounds outside the DPAG were not effective. In another experiment microinjections of 7-Cl-KY (8 nmol) and HA-966 (100 nmol) into the DPAG raised the threshold of aversive electrical stimulation of the rat DPAG. These results indicate that microinjections of 7-Cl-KY and HA-966 into the DPAG cause anxiolytic effects in two different models of anxiety and support the proposal that NMDA-mediated neurotransmission in the DPAG may be related to anxiety and panic.