Evaluation of a bilinear model for attenuation correction using CT numbers generated from a parametric method.

A parametric model is used for the calculation of the CT number of some selected human tissues of known compositions (Hi) in two hybrid systems, one SPECT-CT and one PET-CT. Only one well characterized substance, not necessarily tissue-like, needs to be scanned with the protocol of interest. The linear attenuation coefficients of these tissues for some energies of interest (µ(i)) have been calculated from their tabulated compositions and the NIST databases. These coefficients have been compared with those calculated with the bilinear model from the CT number (µ(B)i). No relevant differences have been found for bones and lung. In the soft tissue region, the differences can be up to 5%. These discrepancies are attributed to the different chemical composition for the tissues assumed by both methods.

Monte Carlo simulation of the dose distribution of ICRP adult reference computational phantoms for acquisitions with a 320 detector-row cone-beam CT scanner.

PURPOSE: The purpose of this study was to develop and validate a Monte Carlo (MC) simulation tool for patient dose assessment for a 320 detector-row CT scanner, based on the recommendations of International Commission on Radiological Protection (ICRP). Additionally, the simulation was applied on four clinical acquisition protocols, with and without automatic tube current modulation (TCM). METHODS: The MC simulation was based on EGS4 code and was developed specifically for a 320 detector-row cone-beam CT scanner. The ICRP adult reference phantoms were used as patient models. Dose measurements were performed free-in-air and also in four CTDI phantoms: 150 mm and 350 mm long CT head and CT body phantoms. The MC program was validated by comparing simulations results with these actual measurements acquired under the same conditions. The measurements agreed with the simulations across all conditions within 5%. Patient dose assessment was performed for four clinical axial acquisitions using the ICRP adult reference phantoms, one of them using TCM. RESULTS: The results were nearly always lower than those obtained from other dose calculator tools or published in other studies, which were obtained using mathematical phantoms in different CT systems. For the protocol with TCM organ doses were reduced by between 28 and 36%, compared to the results obtained using a fixed mA value. CONCLUSIONS: The developed simulation program provides a useful tool for assessing doses in a 320 detector-row cone-beam CT scanner using ICRP adult reference computational phantoms and is ready to be applied to more complex protocols.

Low contrast detectability performance of model observers based on CT phantom images: kVp influence.

This paper studies low contrast detectability (LCD) performance of two model observers in CT phantom images acquired at different kVp levels and compares the results with humans in a 2-alternative forced choice experiment (2-AFC). Images of the Catphan phantom with objects of different contrasts (0.5 and 1%) and diameters (2-15 mm) were acquired in an Aquilion ONE 320-detector row CT (Toshiba Medical Systems, Tokyo, Japan), in two experiments, selecting (80-100-120-135 kV) with fixed mAs and varying the mAs to keep the dose constant, respectively. Four human observers evaluated the objects visibility obtaining a proportion correct (PC) for each case. LCD was also analyzed with two model observers (non-prewhitening matched filter with an eye filter, NPWE, and channelized Hotelling observer with Gabor channels, CHO). Object contrast was affected by kV, with differences up to 17% between the lowest and highest kV. Both models overestimated human performance and were corrected by efficiency and internal noise factors. The NPWE model reproduced better the human PC values trends showing Pearson's correlation coefficients ≥0.976 (0.954-0.987, 95% CI) for both experiments, whereas for CHO they were ≥0.706 (0.493-0.839). Bland-Altman plots showed better agreement between NPWE and humans being the average difference Δ and the range of the differences Δ±2σ (σ, standard deviation) of Δ=-0.3%, Δ±2σ = [-4.0%,4.5%]. For CHO, Δ=-1.2%, Δ± 2σ= [-10.7%,8.3%]. The NPWE model can be a useful tool to predict human performance in CT low contrast detection tasks in a standard phantom and be potentially used in protocol optimization based on kV selection.

Comparison between human and model observer performance in low-contrast detection tasks in CT images: application to images reconstructed with filtered back projection and iterative algorithms.

OBJECTIVE: To compare low-contrast detectability (LCDet) performance between a model [non-pre-whitening matched filter with an eye filter (NPWE)] and human observers in CT images reconstructed with filtered back projection (FBP) and iterative [adaptive iterative dose reduction three-dimensional (AIDR 3D; Toshiba Medical Systems, Zoetermeer, Netherlands)] algorithms. METHODS: Images of the Catphan® phantom (Phantom Laboratories, New York, NY) were acquired with Aquilion ONE™ 320-detector row CT (Toshiba Medical Systems, Tokyo, Japan) at five tube current levels (20-500 mA range) and reconstructed with FBP and AIDR 3D. Samples containing either low-contrast objects (diameters, 2-15 mm) or background were extracted and analysed by the NPWE model and four human observers in a two-alternative forced choice detection task study. Proportion correct (PC) values were obtained for each analysed object and used to compare human and model observer performances. An efficiency factor (η) was calculated to normalize NPWE to human results. RESULTS: Human and NPWE model PC values (normalized by the efficiency, η = 0.44) were highly correlated for the whole dose range. The Pearson's product-moment correlation coefficients (95% confidence interval) between human and NPWE were 0.984 (0.972-0.991) for AIDR 3D and 0.984 (0.971-0.991) for FBP, respectively. Bland-Altman plots based on PC results showed excellent agreement between human and NPWE [mean absolute difference 0.5 ± 0.4%; range of differences (-4.7%, 5.6%)]. CONCLUSION: The NPWE model observer can predict human performance in LCDet tasks in phantom CT images reconstructed with FBP and AIDR 3D algorithms at different dose levels. ADVANCES IN KNOWLEDGE: Quantitative assessment of LCDet in CT can accurately be performed using software based on a model observer.

Dosimetry of a cone beam CT device for oral and maxillofacial radiology using Monte Carlo techniques and ICRP adult reference computational phantoms.

OBJECTIVES: The aim of this study was to calculate organ and effective doses for a range of available protocols in a particular cone beam CT (CBCT) scanner dedicated to dentistry and to derive effective dose conversion factors. METHODS: Monte Carlo simulations were used to calculate organ and effective doses using the International Commission on Radiological Protection voxel adult male and female reference phantoms (AM and AF) in an i-CAT CBCT. Nine different fields of view (FOVs) were simulated considering full- and half-rotation modes, and also a high-resolution acquisition for a particular protocol. Dose-area product (DAP) was measured. RESULTS: Dose to organs varied for the different FOVs, usually being higher in the AF phantom. For 360°, effective doses were in the range of 25-66 µSv, and 46 µSv for full head. Higher contributions to the effective dose corresponded to the remainder (31%; 27-36 range), salivary glands (23%; 20-29%), thyroid (13%; 8-17%), red bone marrow (10%; 9-11%) and oesophagus (7%; 4-10%). The high-resolution protocol doubled the standard resolution doses. DAP values were between 181 mGy cm(2) and 556 mGy cm(2) for 360°. For 180° protocols, dose to organs, effective dose and DAP were approximately 40% lower. A conversion factor (DAP to effective dose) of 0.130 ± 0.006 µSv mGy(-1) cm(-2) was derived for all the protocols, excluding full head. A wide variation in dose to eye lens and thyroid was found when shifting the FOV in the AF phantom. CONCLUSIONS: Organ and effective doses varied according to field size, acquisition angle and positioning of the beam relative to radiosensitive organs. Good positive correlation between calculated effective dose and measured DAP was found.

Validation of a Monte Carlo simulation for dose assessment in dental cone beam CT examinations.

A Monte Carlo (MC) simulation for calculating absorbed dose has been developed and applied for dental applications with an i-CAT cone beam CT (CBCT) system. To validate the method a comparison was made between calculated and measured dose values for two different clinical protocols. Measurements with a pencil CT chamber were performed free-in-air and in a CT dose head phantom; measurements were also performed with a transmission ionization chamber. In addition for each protocol a total number of 58 thermoluminescence dosemeters (TLD) were packed in groups and placed at 16 representative anatomical locations of an anthropomorphic phantom (Remab system) to assess absorbed doses. To simulate X-ray exposure, a software application based on the EGS4 package was applied. Dose quantities were calculated for different voxelized models representing the CT ionization and transmission chambers, the TLDs, and the phantoms as well. The dose quantities evaluated in the comparison were the accumulated dose averaged along the rotation axis (D(i)), the volume average dose,D(vol) for the dosimetric phantom, the dose area product (DAP) and the absorbed dose for the TLDs. Absolute differences between measured and simulated outcomes were ≤ 2.1% for free-in-air doses; ≤ 6.2% in the 5 cavities of the CT dose head phantom; ≤ 13% for TLDs inside the primary beam. Such differences were considered acceptable in all cases and confirmed the validity of the MC program for different geometries. In conclusion, the devised MC simulation program can be a robust tool to optimize protocols and estimate patient doses for CBCT units in dental, oral and maxillofacial radiology.

Automated assessment of low contrast sensitivity for CT systems using a model observer.

PURPOSE: Low contrast sensitivity of CT scanners is regularly assessed by subjective scoring of low contrast detectability within phantom CT images. Since in these phantoms low contrast objects are arranged in known fixed patterns, subjective rating of low contrast visibility might be biased. The purpose of this study was to develop and validate a software for automated objective low contrast detectability based on a model observer. METHODS: Images of the low contrast module of the Catphan 600 phantom were used for the evaluation of the software. This module contains two subregions: the supraslice region with three groups of low contrast objects (each consisting of nine circular objects with diameter 2-15 mm and contrast 0.3, 0.5, and 1.0%, respectively) and the subslice region with three groups of four circular objects each (diameter 3-9 mm; contrast 1.0%). The software method offered automated determination of low contrast detectability using a NPWE (nonprewhitening matched filter with an eye filter) model observer for the supraslice region. The model observer correlated templates of the low contrast objects with the acquired images of the Catphan phantom and a discrimination index d' was calculated. This index was transformed into a proportion correct (PC) value. In the two-alternative forced choice (2-AFC) experiments used in this study, a PC ≥ 75% was proposed as a threshold to decide whether objects were visible. As a proof of concept, influence of kVp (between 80 and 135 kV), mAs (25-200 mAs range) and reconstruction filter (four filters, two soft and two sharp) on low contrast detectability was investigated. To validate the outcome of the software in a qualitative way, a human observer study was performed. RESULTS: The expected influence of kV, mAs and reconstruction filter on image quality are consistent with the results of the proposed automated model. Higher values for d' (or PC) are found with increasing mAs or kV values and for the soft reconstruction filters. For the highest contrast group (1%), PC values were fairly above 75% for all object diameters >2 mm, for all conditions. For the 0.5% contrast group, the same behavior was observed for object diameters >3 mm for all conditions. For the 0.3% contrast group, PC values were higher than 75% for object diameters >6 mm except for the series acquired at the lowest dose (25 mAs), which gave lower PC values. In the human observer study similar trends were found. CONCLUSIONS: We have developed an automated method to objectively investigate image quality using the NPWE model in combination with images of the Catphan phantom low contrast module. As a first step, low contrast detectability as a function of both acquisition and reconstruction parameter settings was successfully investigated with the software. In future work, this method could play a role in image reconstruction algorithms evaluation, dose reduction strategies or novel CT technologies, and other model observers may be implemented as well.

[Quality assessment in single-slice spiral brain CT examinations of patients with cerebrovascular accident]. / Evaluación de la calidad de los exámenes de tomografía computarizada de cerebro en la indicación de accidente cerebro-vascular agudo.

OBJECTIVES: Our objective was to apply quality criteria proposed by the European Commission (EC) Guidelines to the brain CT examinations for cerebrovascular accident (CVA) diagnosis at single-slice spiral CT scanners from five different hospitals in the Madrid area. MATERIAL AND METHODS: A sample of 100 brain CT examinations was collected and independently reviewed by five radiologists, to determine the degree of fulfilment of image quality criteria. Dose measurements were performed to estimate the values of the CT dose indexes (CTDIw, CTDIair), the dose length product (DLP), and the effective dose (E). RESULTS: Once the McNemar test was applied to the sample, the number of observers' readings was reduced to three. The quality criteria were, in general, fulfilled, since mean values of image quality score between 80% and 92% were deduced, with variation coefficients per centre in the range of 0.07-0.1. However, both visualization criteria 1.1.2 and 1.1.3 exhibited similar ranges of fulfilment (38% - 94%). The good compliance with critical reproduction criteria in the study reflected the capability of these CT scanners to create images of adequate quality, although optimisation should be achieved in some of the centres. Concerning radiation exposure, the mean values per centre of the dose quantities were in the range of 42-64 mGy for the weighted CTDI (CTDIw), 423-744 mGy x cm for DLP, and 1.1-1.9 mSv for E. CONCLUSIONS: The mean values at three centres were close to but above the reference value proposed by the EC Guidelines for CTDIw (60 mGy), and lower than the corresponding reference level for DLP (1050 mGy x cm). Dose optimisation techniques focused on the adjustment of the CTDIw-related examination parameters were proposed.

Evaluación de la calidad de los exámenes de tomografía computarizada de cerebro en la indicación de accidente cerebro vascular agudo / Quality assessment in single-slice spiral brain ct examinations of patients with cerebrovascular accident

Objetivos. El objetivo del trabajo ha sido aplicar los criterios de calidad propuestos en la Guía de la Comisión Europea sobre criterios de calidad en tomografía computarizada (TC) para exámenes de cerebro en la indicación de accidente cerebro-vascular (ACV) en cinco centros de la Comunidad de Madrid dotados de equipos de TC helicoidal de corte único. Material y métodos. Se ha recogido una muestra de 100 exámenes de cerebro que ha sido analizada independientemente por cinco radiólogos para establecer el grado de cumplimiento de los criterios de imagen propuestos. Se han efectuado medidas de dosis en los centros para estimar los valores de los índices de dosis de TC (CTDIw, CTDIair), el producto dosis-longitud (DLP) y la dosis efectiva (E). Resultados. Después de aplicar las pruebas de McNemar y de Friedman a las evaluaciones, se seleccionaron las correspondientes a tres observadores. En general se cumplieron los criterios de calidad en una proporción alta, con promedios del índice de calidad de imagen por centros entre el 80% y el 92%, y coeficientes de variación entre 0,07 y 0,1. Sin embargo, dos criterios de visualización (el 1.1.2 y el 1.1.3) se cumplieron en una proporción variable según los centros con un rango similar de cumplimiento medio (38%-94%). Los criterios de reproducción crítica se cumplieron en una mayor proporción que los de visualización, reflejando así la capacidad técnica de estos equipos para generar imágenes de calidad adecuada, aunque en algunos centros hay que optimizar los procedimientos. En cuanto a las dosis de radiación, los valores medios del CTDIw por centros estuvieron en el intervalo 42-64 mGy, los del DLP entre 423 y 744 mGy·cm y la dosis efectiva media entre 1,1 y 1,9 mSv. Conclusiones. Los valores medios del CTDIw en tres de los centros estuvieron ligeramente por encima del valor de referencia propuesto en la Guía Europea (60 mGy) y en todos por debajo del correspondiente para el DLP (1050 mGy·cm). Se han analizado y propuesto vías de optimización de la calidad de imagen y la dosis en cada centro

Objectives. Our objective was to apply quality criteria proposed by the European Commission (EC) Guidelines to the brain CT examinations for cerebrovascular accident (CVA) diagnosis at single-slice spiral CT scanners from five different hospitals in the Madrid area. Material and methods. A sample of 100 brain CT examinations was collected and independently reviewed by five radiologists, to determine the degree of fulfilment of image quality criteria. Dose measurements were performed to estimate the values of the CT dose indexes (CTDIw, CTDIair), the dose length product (DLP), and the effective dose (E). Results. Once the McNemar test was applied to the sample, the number of observers' readings was reduced to three. The quality criteria were, in general, fulfilled, since mean values of image quality score between 80% and 92% were deduced, with variation coefficients per centre in the range of 0.07-0.1. However, both visualization criteria 1.1.2 and 1.1.3 exhibited similar ranges of fulfilment (38% -- 94%). The good compliance with critical reproduction criteria in the study reflected the capability of these CT scanners to create images of adequate quality, although optimisation should be achieved in some of the centres. Concerning radiation exposure, the mean values per centre of the dose quantities were in the range of 42-64 mGy for the weighted CTDI (CTDIw), 423-744 mGy·cm for DLP, and 1.1-1.9 mSv for E. Conclusions. The mean values at three centres were close to but above the reference value proposed by the EC Guidelines for CTDIw (60 mGy), and lower than the corresponding reference level for DLP (1050 mGy·cm). Dose optimisation techniques focused on the adjustment of the CTDIw-related examination parameters were proposed

Absceso cerebral / Brain abscess

El absceso cerebral es una patología poco frecuente en la infancia, aunque grave, que puede presentar una alta morbimortalidad, a pesar de los avances diagnósticos y terapéuticos actuales. El germen causal depende de los factores predisponentes. La presentación clínica en niños es inespecífica, y requiere la sospecha precoz por parte del médico. La tomografía computarizada (TC) y/o la resonancia magnética (RM) son herramientas indispensables para realizar el diagnóstico de certeza. El tratamiento de la mayoría de los abscesos consiste en antibioterapia de amplio espectro y drenaje quirúrgico, aunque en la fase precoz de cerebritis puede responder sólo a tratamiento médico. Describimos una niña de 13 años diagnosticada de dos abscesos cerebrales originados a partir de una otitis media y que se encontraba en tratamiento antibiótico. Presentaba cefalea, vómitos y otalgia a su ingreso. El diagnóstico se hizo mediante TC. Se trató con antibioterapia de amplio espectro con buna penetración cerebral, con la que evolucionó a un aumento del tamaño del absceso y un empeoramiento clínico. Se realizó la aspiración estereotáxica de la lesión y la evolución fue favorable sin complicaciones postquirúrgicas (AU)

Brain abscess is uncommon but life- threatening infection in children with high mobility and mortality despite recent advances in diagnostic and therapeutic modalities. Predominant etiologic microorganisms vary depending on these predisposing factors. The clinical presentation in children can be nonspecific, and a high index of suspicion is required. Computed tomography (CT) and/or magnetic resonance imaging (MRI) are essential tools that enable the physician to diagnosis. Surgical drainage with antimicrobial therapy is the treatment of choice for most brain abscesses. In the early phase of cerebritis, infection can respond to long-term antibiotic therapy alone. We described a 13 years old girl with two brain abscesses originated form otitis media with antibiotic therapy. Diagnosis was given by CT. Initial treatment with broad spectrum antibiotics with good cerebral penetration was associated with an increase in the size of abscess and clinical worsening. Stereotactic aspiration of lesion and culture was performed and the patient showed improvement and there was any postoperative complication (AU)

Monte Carlo calculation of radiation dose in CT examinations using phantom and patient tomographic models.

By using a voxel-based Monte Carlo simulation technique, we developed and validated a method to calculate radiation-absorbed dose in the computed tomography (CT) examinations from the images of phantoms and patients. The ionising radiation transport was simulated using the EGS4 code system. The geometry of the X-ray beam (focus-to-axis distance, field of view, collimation, and primary and beam-shaper filtration) and the X-ray spectral distribution (HiSpeed LX/i) were included in the simulation. Each axial CT image was reduced to a 256 x 256 matrix and stacked in a volume. The patient images were segmented before the simulation of radiation transport by using four categories of materials, such as air, lung, muscle and bone. To test the voxel-based method, the values of the radiation dose derived from a simulated CT exposure were calculated and compared with those obtained from the measurements performed within the dosimetry phantoms. To complete the scope of the work, series of CT scans of the trunk of an anthropomorphic phantom and patients were simulated to calculate the average dose in each 1-cm-wide transverse slice (ADS). The comparison between the simulated and measured dose data for the CT indices showed a difference of <5% in all the cases. The estimated mean values of ADS from the chest, abdomen and pelvis of the anthropomorphic phantom were approximately 1.7-2 times the weighted CT dose index (CTDI(w)) value, whereas the mean ADS values for these anatomical areas were 1.3-2 times the CTDI(w) of patients. The voxel-based simulation method provided a technique for estimating the individual patient doses in the CT examinations.

Image quality and dose evaluation in spiral chest CT examinations of patients with lung carcinoma.

A study was undertaken to assess the quality of general chest CT examinations for indication of lung carcinoma according to the criteria proposed in the European Commission (EC) Guidelines, and to investigate their usefulness in the optimization of this practice. The criteria were evaluated for a sample of 100 examinations from five radiology departments in the Madrid area featuring single slice helical CT scanners with special emphasis on radiation dose and image quality. To determine the degree of compliance with the image criteria considered, the examinations were independently evaluated twice by five radiologists from the participating centres. A subsequent selection of the observers was made according to the consistency and independence of their readings. Dose measurements carried out in parallel supplied data to estimate the values of the CT dose indices (CTDI), dose-length product (DLP) and effective dose (E). The results show good compliance with the image criteria used - between 93% and 98% on average at the different sites, with variable degrees of internal deviation. 10 out of a total of 16 criteria proposed in the EC guidelines were met by practically all the examinations in the sample. The average weighted CTDI (CTDI(w)) values per site were in the range of 13-19 mGy; those of DLP were between 263 mGy cm and 577 mGy cm, and those of effective dose between 4 mSv and 9 mSv. The highest mean DLP value was below but close to the reference value proposed in the EC Document (650 mGy cm). In general, a weak correlation or no correlation at all was found between image quality scores and patient dose (DLP).

Quality criteria implementation for brain and lumbar spine CT examinations.

A study was undertaken to implement the quality criteria proposed by the European Commission for brain general and lumbar spine (disc herniation) CT examinations. The proposed criteria were evaluated for samples including 93 brain and 86 lumbar spine CT examinations, with special emphasis on the diagnostic and radiation dose requirements. The extent to which the image criteria had been achieved was evaluated after two independent observers had each read the images twice. Dose measurements were conducted in parallel to estimate the proposed dose quantities needed to obtain the images. For brain examinations, we found that a group of image criteria were largely met, and met uniformly in all sites. One criterion (1.2.5) was frequently fulfilled but had intermediate values for two sites; the remaining criteria were fulfilled to different extents, although for criteria 1.2.1 and 1.2.2, scores were lower than 50% and 70%, respectively. The mean percentage image quality score had values between 57% and 78%, with variation coefficients in the range 30-68%. Mean values of the dose quantities were in the ranges 44-74 mGy for weighted CT dose index (CTDIw), 497-1018 mGy cm for dose-length product (DLP) and 1.1-2.2 mSv for effective dose (E). CTDIw and DLP were not correlated because of significant variations in the scanned length, whereas DLP and E were strongly correlated. A weak relationship between image quality score and DLP was found for the sample as a whole. For lumbar spine examinations, none of the critical reproduction image criteria was systematically achieved. One group of criteria (1.2.7, 1.2.8 and 1.2.9) was fulfilled to a large extent in many departments, but fulfilment of the remainder varied widely. The mean score fluctuated in the range 39-88%, with three groups of differences: low (39-51%), intermediate (67-71%) and high (85-88%). Mean values of the CTDIw varied between sites in the range 27-48 mGy. Mean DLP values varied between 188 mGy cm and 333 mGy cm, and the mean effective dose ranged between 3 mSv and 5 mSv. There were significant differences in effective dose between men and women. By sites, there was no relationship between DLP and mean score, with the highest image score associated with intermediate dose values. The percentage disagreement among the observers about a given criterion ranged between 2% and 22% for brain, and between 3% and 46% for lumbar spine.

[Acute meningococcal disease. Its prognostic assessment]. / Enfermedad meningocócica aguda. Valoración pronóstica.

We have studied 50 children affected with acute meningococcal disease (AMD). The ages of the children varied between 4 months and 12.58 years, with a mean age of 4.58 years. By using the shock state and DIC syndrome, both of which are indications of the severity of the illness, an evaluation of the discriminatory capacity was done with regard to significantly associate variables and 3 scores, Bjorvatn, Leclerc and PRISM, throughout 8 intervals within the first 48 hours of hospital treatment. We observed a very high survival rate (98%) associated with the early treatment for shock. Leukopenia and disseminated purpura were the best variables in order to discriminate shock and DIC, respectively. The greatest capacity for the diagnosis of the shock state and DIC syndrome were registered during the 0-6 hour period and the 0-12 hour period, respectively. The prognosis improved if the child remained alive 12 hours after the treatment had begun.

Estimation of doses to patients from "complex" conventional X-ray examinations.

A numerical method has been developed to estimate the organ doses and effective dose-equivalent for patients undergoing three "complex" examinations (barium meal, barium enema and intravenous urography). The separation of radiological procedures into a set of standard numerical views is based on the use of Monte Carlo conversion factors and measurements within a Remab phantom. The radiation doses measured in a phantom for such examinations have been compared with the predictions of the "numerical" method. Dosimetric measurements with thermoluminescent dosemeters attached to the patient's skin along with measurements of the dose-area product during the examination have enabled us to derive organ doses and to estimate the effective dose-equivalent. Mean frequency weighted values of dose-area product, energy imparted to the patient, doses to a set of organs and effective dose-equivalent in the area of Madrid are reported. Comparisons of the results with those from similar surveys in other countries have been made.

Some indicative parameters on diagnostic radiology in Spain: first dose estimations.

The Medical Physics Group at the Complutense University of Madrid has been co-ordinating, for approximately 1 year, a project on optimization of radiation protection in diagnostic radiology, in co-operation with the other states of the European Community. Exhaustive data on the subject, which offer accurate results on patient dosimetry for the different types of examination, are the final aim of the project. So far, it has been possible to analyse in detail the data from the National Institute of Health (NIH), which manages the care of about 96% of the Spanish population, plus the findings from several hospitals, outpatient centres and private clinics of the community of Madrid, which allowed us to perform the first dose estimations and to extrapolate them to the rest of Spain. The following estimations are presented: annual frequency of different examinations, their variation from 1985 to 1986, number of diagnostic rooms used for a given minimum of annual examinations, organ doses for different examinations, effective dose-equivalent, genetically significant dose for some examinations, as well as the collective dose.

[Reye's syndrome in Spain, 1980-1984 (A cooperative study: Pediatric Intensive Care Section of the Asociación Española de Pediatría)]. / Síndrome de Reye en España, 1980-1984. (Estudio cooperativo. Sección de CIP de la AEP).

The incidence of the Reye syndrome in Spain has been retrospectively reviewed from 1980 to 1984. A survey of 57 cases has been available to study. It is pointed out the low frequency (0.12/10(5) 15 years); the low mean age (12 month) due to a higher prevalence in infants; the high mortality rate (49%), proportional to the great number of III and IV Lovejoy's stages; the low correlation with chicken-pox and salycilate-intake in the prodromic period and a better prognosis in patients when barbituric coma was established along with other measures.

[Election of a venous approach. The internal jugular vein]. / Elección de vía venosa. La vena yugular interna.

Due to the variety of venous routes and of techniques described, it may be difficult to choose most suitable one in every case. Authors found percutaneous internal jugular vein cannulation appropriate as alternative venous route for short-term routine use, and as a preferent one for long-term use or if central venous cannulation is necessary. They present their experience with this technique in 52 children from 7 days to 13 years old (3-36 kg). They achieved 44 cannulations (84,6%), with a greater success rate at right side (90,4%) than at left side (60%). As complications there were 4 carotid artery punctures (3,9% of the punctures) and one transient sinus bradycardia (0,9% of the punctures). They conclude that this technique is the one of choice for central venous cannulation.