Energy imparted to neonates during X-ray examinations in a special care baby unit.

Neonates in a special care baby unit may receive a large number of X-rays and their dosimetry is of particular importance. A method of calculating energy imparted to neonates has been developed and a survey carried out in one unit, over a period of 18 months. Entrance dose was calculated from the technique factors used and measurement of tube output. Technique factors were recorded by the radiographer for each exposure taken, and output was measured both with and without an incubator present. Field size was determined by measurements made retrospectively from the radiograph, and a Monte Carlo simulation was used to determine factors for conversion to imparted energy. 119 neonates were included in the survey, and the mean total energy imparted was found to be 0.09 mJ. The maximum value was a factor of nine greater than this. This study also highlighted the potential for dose reduction with regard to better collimation and shielding.

Radiation doses to paediatric patients undergoing less common radiological procedures involving fluoroscopy.

A semi-automated dosimetry survey has been undertaken to monitor the radiation doses to patients in a paediatric fluoroscopy room. The doses were assessed using large area Diamentor ionization chambers to measure dose x area product, and by means of thermoluminescent dosemeters attached to the patient's skin in various places. Details of patients and examinations were entered into a computer, all information being stored on a data base. Many radiological examinations have been monitored, including renal and jejunal biopsies, nephrostograms, loopograms, tracheograms and fistulograms. Patients included in the study have been divided into three age bands for dose assessment. Radiation doses for different types of examination have been compared, including more common examinations for which data have been previously presented.

Results of a survey of doses to paediatric patients undergoing common radiological examinations.

A survey has been performed to investigate typical radiation dose levels for children undergoing a number of common radiological examinations. Doses have been assessed using a Diamentor ionization chamber to measure dose-area product, and by attaching thermoluminescent dosemeters to the patient's skin to determine entrance and organ doses. The survey has been automated by using a personal computer for data collection and storage. Doses have been monitored for a large number of children, primarily in a dedicated paediatric X-ray room, and the results presented can be used as a baseline for making comparative measurements elsewhere. Entrance skin doses were found to range from 0.3 mGy to 5.7 mGy for radiographic examinations, and values of dose-area product from 3 to 225 cGy cm2. The corresponding dose ranges for fluoroscopic examinations are 7.4-26.2 mGy and 130-1241 cGy cm2.

Ultrasound screening of newborn urinary tract.

A non-invasive method to screen newborn babies for ureteric reflux might allow the possibility of appropriate action to prevent reflux nephropathy. We have tested the sensitivity of ultrasound screening of the urinary tract. 1061 unselected newborn infants born during 1986 were examined by ultrasound and the findings were recorded on videotape. Babies with dilated renal collecting systems underwent further investigations (micturating cystourethrography, intravenous urography, or radioisotope study). With these methods, 11 children were found to have renal disorders. A postal follow-up survey was carried out when the children were 3 years old. 657 (62%) families responded. We searched for non-responders among children born in 1986 who had subsequently had a renal radioisotope investigation: 5 non-responders were found among these children. Of the total, 24 children had had a urinary-tract infection: 3 more children with ureteric reflux were found; their neonatal ultrasound scans had suggested no abnormality. Thus, more than half the children of this cohort in whom hydronephrosis or ureteric reflux developed had only slight dilatation (less than 5 mm) on the neonatal scan. On review of the original videotapes there was no difference in internal dimension between left and right kidneys: the internal dimension was 5 mm or less in both kidneys in 96.3% of babies and 4 mm or less in 93.3%. Routine renal ultrasound scanning of newborn babies is of no value in detecting those who may have ureteric reflux: the number of other renal abnormalities likely to be detected is small.

Ultrasound measurement of renal size in newborn infants.

Renal measurements were made by ultrasonography in 560 healthy newborn infants. Three dependent variables (kidney length, kidney depth, and kidney area) were measured, together with three independent variables (birth weight, head circumference, and gestational age). The SD of the measurement inconsistency was 0.13 cm for length, 0.078 cm for depth, and 0.32 cm2 for area; the percentages of total variance caused by measurement inconsistency were 7.9, 9.5, and 7.5, respectively. There was a significant difference between right and left kidneys in length and depth for each independent variable. The left kidney increased more in length and less in depth than the right so that the areas remained similar as the scale of variable increased. Kidney depth and area in boys were significantly larger than in girls, both dimensions increasing at equal rates. Centile charts for each dependent variable by each independent variable were constructed by a non-parametric method.