Paediatric CT dose: a multicentre audit of subspecialty practice in Australia and New Zealand

OBJECTIVES

To evaluate paediatric CT dosimetry in Australia and New Zealand and calculate size-specific dose estimates (SSDEs) for chest and abdominal examinations.

METHODS

Eight hospitals provided data from 12 CT systems for 1462 CTs in children aged 0-15. Imaging data were recorded for eight examinations: head (trauma, shunt), temporal bone, paranasal sinuses, chest (mass) and chest HRCT (high-resolution CT), and abdomen/pelvis (mass/inflammation). Dose data for cranial examinations were categorised by age and SSDEs by lateral dimension. Diagnostic reference ranges (DRRs) were defined by the 25th and 75th percentiles. Centralised image quality assessment was not undertaken.

RESULTS

DRRs for 201 abdominopelvic SSDEs were: 2.8-4.7, 3.6-11.5, 8.5-15.0, 7.6-15, and 10.6-16.2 for the <15 cm, 15-19 cm, 20-24 cm, 25-29 cm and >30 cm groups, respectively. For 147 chest examinations using these body width categories, SSDE DRRs were 2.0-4.4, 3.3-7.9, 4.0-9.4, 4.5-12, and 6.5-12. Kilovoltage peak (kVp), but not AEC or IR, was associated with SSDE (parameter estimate [standard error]: 0.12 (0.03); p < 0.0001).

CONCLUSIONS

Australian and New Zealand paediatric CT DRRs and abdominal SSDEs are comparable to international data. SSDEs for chest examinations are proposed. Dose variations could be reduced by adjusting kVp.

KEY POINTS

• SSDEs can be calculated for all patients, CT systems, and practices • Kilovoltage peak (kVp) has the greatest association with dose in similar-sized patients • Paediatric DRRs for CT are now available for use internationally.

Peripheral quantitative computed tomography (pQCT) reveals low bone mineral density in adolescents with motor difficulties

This is the first reported study to describe local bone mineral density, assess parameters of fracture risk and report history of fractures in adolescents with motor difficulties. Motor difficulties evidenced by poor coordination in adolescence should be considered a new risk factor for below-average bone strength and structure and fracture risk.

INTRODUCTION

Adolescents with motor difficulties are characterised by poor coordination and low levels of physical activity and fitness. It is possible these deficits translate into below-average bone strength and structure. The objectives of this study were to describe local bone mineral density (BMD), assess parameters of fracture risk (stress-strain index, SSI) and report history of fractures in this group.

METHODS

Thirty-three adolescents (13 females), mean age of 14.3 (SD = 1.5) years, with motor difficulties underwent peripheral quantitative computed tomography (pQCT) measurements at proximal (66 %) and distal (4 %) sites of the non-dominant radius (R4 and R66) and tibia (T4 and T66). One sample t test was used to compare Z-scores for total BMD, trabecular density, cortical density and stress strain index (SSI) against standardized norms.

RESULTS

Significant differences were present at R4 total density mean Z-score = -0.85 (SD = 0.7, p < 0.001), R66 cortical density mean Z-score = -0.74 (SD = 1.97, p = 0.038), R66 SSI mean Z-score = -1.00 (SD = 1.08, p < 0.001) and T66 SSI mean Z-score = -0.70 (SD = 1.15, p < 0.001). There was a higher incidence of fractures (26.9 %) compared to the normal population (3-9 %).

CONCLUSIONS

Motor difficulties in adolescence should be considered a risk factor for below-average bone strength and structure and fracture risk. Strategies are needed to improve bone health in this high-risk-group.

Allergic reaction following micturating cystourethrography

Adverse reactions associated with the parenteral use of contrast agents are widely recognized, but reactions to contrast agents used in micturating cystourethrography (MCU) are much less common, although absorption of contrast media through intact bladder mucosa has been documented. A significant adverse reaction to ionic contrast material used for MCU in which neither reflux nor traumatic urethral catheterization could be implicated is presented. This case illustrates that significant reactions can occur during MCU and appropriate resuscitation facilities must be available. In a patient with a history of reaction to IV contrast media, the need for MCU should be reviewed and consideration given to nuclear medicine MCU. If a radiologic MCU is needed, consideration should be given to performing it in the hospital, with nonionic contrast media and steroid premedication.

Intussusception: clinical prediction of outcome of barium reduction

Patients with intussusception who have necrotic bowel requiring bowel resection or who are at major risk of perforation from attempted hydrostatic reduction may be better managed without barium reduction. Ideally, the clinician would like to identify such patients at presentation. Two groups of patients, representing the extreme ends of the intussusception treatment spectrum were investigated in order to highlight the clinical features of patients in whom an attempted barium reduction is not justified. A group of 200 patients who had successful and safe hydrostatic reduction was compared with 104 patients who ultimately required bowel resection. Four features were found to be indicators of an increased likelihood of resection: age 3 months or less, or greater than 2 years, duration of symptoms greater than 24 h, presence of small bowel obstruction on plain radiology, and clinical assessment of dehydration greater than 5%. The validity of these features as prognostic indicators was assessed by applying them to all patients who had attempted barium reduction to see how they predicted patient outcome. In isolation, each feature was found to be compatible with a safe and successful hydrostatic reduction. The rate of resection was increased in patients with multiple adverse features and in these patients the enema technique may require modification. Patients with three or four adverse features had an unacceptably high incidence of gangrenous bowel requiring resection and a low likelihood of successful hydrostatic reduction. It is believed that attempts at reduction are not appropriate in these patients.