X-ray exposure in utero and school performance: a population-based study of X-ray pelvimetry.

AIM: To investigate the association between exposure to ionising radiation from pelvimetric examinations in utero and school performance. MATERIAL AND METHODS: This was a population-based cohort study comprising 46,066 children born in the county of Östergötland, Sweden, from 1980 through 1990. Through record linkage between Swedish registers, children exposed in utero to X-ray pelvimetry examination were compared to other children born in the same county during the study period, as well as to their unexposed siblings. Outcome variable was primary school grades, expressed in centiles and calculated through linear regression. RESULTS: In the univariate analysis, children exposed to X-ray pelvimetry in utero had higher school grades compared to unexposed children (point estimate 3 centiles, 95% confidence interval [CI]: 1.5 to 4.6). When sex, mother's education and income, birth order, and birth position were included in the analysis; however, the difference was reduced and the association was no longer statistically significant (PE 1.4, 95% CI: -0.1 to 2.8). Comparing exposed children with their siblings showed no statistical difference in univariate analysis or in multivariate analysis. CONCLUSION: No suggestion was found of a negative effect on school performance from in utero exposure of diagnostic X-ray pelvimetry.

[Low dose helical CT pelvimetry: evaluation of radiation dose and image processing]. / Pelviscanner hélicoïdal en basse dose: évaluation de la dose d'irradiation et du traitement d'images.

PURPOSE: to estimate from phantom measurements the radiation dose and the accuracy of helical ct pelvimetry. MATERIALS AND METHODS: Eight helical CT acquisitions using different tube current (100, 50, 25 or 10mAs) and pitch factor (1.125 or 1.375) settings but identical collimation (2mm) and kilovoltage (120 kVp) were evaluated using a four-channel MDCT scanner and compared with conventional CT pelvimetry including a single scout and two transverse images. A plexiglas phantom combined with an ionization chamber was used to calculate the CTDIw and DLP for each acquisition. Then, an ex vivo phantom of bony pelvis was used to evaluate the accuracy of helical acquisitions for the measurement of pelvic diameters (i.e. the antero-posterior inlet, the transverse inlet and the interspinous distance). Reconstructions of helical acquisitions were performed using 2D MPR, 3D MIP and 3D SSD algorithms. RESULTS: CTDIw and DLP of conventional pelvimetry were 26 mGy and 42 mGy.cm respectively. The radiation dose of helical acquisitions decreased linearly with tube current (CTDIw: from 13 to 1.3 mGy, DLP: from 218.3 to 18.7 mGy.cm). Compared to conventional CT, the dose was nearly similar at 25 mAs and reduced at 10 mAs. Helical acquisitions provided accurate measurements of pelvic diameters with a pitch of 1.125 and a 2D MPR algorithm to evaluate the AP inlet and a 3D MIP algorithm to evaluate the transverse inlet and the interspinous distance. Variations of tube current did not influence the accuracy of pelvic diameter measurement. CONCLUSION: Our results suggest that accurate low-dose helical CT pelvimetry using 10-25 mAs and a pitch factor of 1.125 combined with 2D MPR and 3D MIP reconstructions is possible.

X-ray pelvimetry: helpful or harmful?

This study was performed (1) to clarify the usefulness of x-ray pelvimetry in diagnosing cephalopelvic disproportion (CPD), particularly in patients with abnormal labor, and (2) to examine the association between infant birthweight and mode of delivery. The subjects were 100 consecutive patients who underwent x-ray pelvimetry. A retrospective chart review was done to collect demographic data and evaluate Friedman labor curves. Radiologic dimensions were tabulated for anteroposterior diameter, transverse diameter, and summation plane values of both inlet and midpelvic planes. Average pelvimetric values for subjects delivered vaginally and those delivered abdominally were compared, and Hotelling's T2 analyses were conducted to determine whether the differences were statistically significant. Average birthweights of infants born to women in cesarean section and vaginal delivery groups were also compared, with t tests conducted to determine statistical significance. Results showed that even in a select group of patients in abnormal labor with the highest probability of CPD--a condition it was believed x-ray pelvimetry could diagnose--no significant difference in bony pelvic dimensions existed between vaginal and cesarean delivered patients. The cesarean group did, however, deliver significantly heavier infants. The results question the usefulness of x-ray pelvimetry in diagnosing CPD.

[Pelvimetry in Norwegian maternity departments]. / Pelvimetri ved nordke fødeavdelinger.

A questionnaire was sent to 39 maternity departments in Norway. We asked about indications for and use of pelvimetry in the department. 36 departments returned the filled in questionnaire. This paper presents the results of the survey together with a brief discussion of possible harmful effects of pelvimetry. The results show that in Norway every pregnant woman has access to pelvimetry, but there is wide variation as regards the indications and which limits to use. Many obstetricians doubt the value of pelvimetry, especially in vertex presentation. Some are still concerned about the possible harmful effect of ionising radiography. All maternity departments should critically discuss their use of pelvimetry. In the future other methods should replace pelvimetry so that mother and foetus will no longer be exposed to ionising radiography.

Defects of the central nervous system in Finland. IV. Associations with diagnostic x-ray examinations.

Based on the Finnish Register of Congenital Malformations a search was undertaken to find possible associations between defects of the CNS and diagnostic x-ray examinations of the mother during pregnancy as well as pelvic x-ray examinations prior to pregnancy. Time-area--matched pregnancies and polydactylic children were used as controls. The risk of having a microcephalic child was increased for mothers with pelvic x-ray prior to pregnancy, but the number of discordant pairs was small. Of the examinations performed during pregnancy, fetal x-ray was significantly more common among mothers who delivered a CNS-defective child. No associations were observed for other kinds of examinations.

[Protection from ionizing radiation in medicine]. / Schutz vor ionisierenden Strahlen in der Medizin.

Radiation burden of medical personnel is low in trained medical staff. Higher doses can occur with therapeutic application of unsealed or sealed sources, if adequate shielding is not possible or not cared for or if radiation protection measures are not observed in work with higher activities of radionuclides. More important than immoderate structural alterations for shielding purposes is individual inspection with advice on the working place and optimisation of working methods, also in regard to the radiation protection. This is possible only by cooperation and by discussing risks and problems between the radiation protection officer and the working personnel in an overt manner, assuring the mutual understanding. Radiation protection concerning medical uses of radiation in the whole population and in patients especially is determined by the necessity of indication for the medical application of radiation, by quality control and lastly by the correct interpretation of results or consequences. The latter necessitates a good collaboration between nuclear medicine specialists and clinicians because of the individual particularity of the patient which must be considered in the evaluation of results.

The effects of diagnostic X-ray exposure on the human fetus: an examination of the evidence.

Epidemiological studies have demonstrated an increased incidence of morbidity and mortality among children exposed prenatally or preconceptually to diagnostic x-rays, as compared to nonirradiated controls. In those studies radiation exposure occurred on a selective basis, as the examination was always medically indicated. Comparisons of those studies and comparable ones in which radiation exposure occurred on a nonselective basis (from routine pelvimetry examinations or atomic bomb radiation) indicate that the latter studies do not confirm the former and a significant discrepancy is present in each instance. Thus, some doubt is cast on the validity of the former studies.