A comparison of subtraction MRI with the standard contrast-enhanced imaging in Perthes' disease.

PURPOSE: Perthes' disease (PD) results from loss of blood supply to the hip and can progress to femoral head deformity. MRI in the early course of the disease can provide data on the initial extent of infarct. Vascularity of the femoral head is assessed by gadolinium-enhanced MRI (contrast MRI), which may be improved by the digital subtraction technique (subtraction MRI). We hypothesized that gadolinium-enhanced MRI without subtraction was comparable with subtraction MRI in depicting the femoral head perfusion. METHODS: In all, 34 patients (34 hips) with unilateral PD had gadolinium-enhanced MRI as part of a prospectively randomized study. Nine patients had three MRIs, 15 had two and ten had a single MRI. Measurement of perfusion of the femoral head (MRI perfusion index) was obtained using digital image analysis on all the MRIs, including both before and after subtraction. A paired sample t-test was performed to compare the measurements. RESULTS: The mean age of the patients was 8.9 years (sd 1.6). At the time of diagnosis, the subtraction MRI did not elicit a statistically significant difference in MRI perfusion index measurements when compared with the contrast MRI (p = 0.19). The same findings were found when including all patients at various stages of the disease (p = 0.30). Qualitatively, although some subtraction MRI images showed superior delineation of epiphysis, there are no significant differences throughout the whole series. CONCLUSION: Although the current literature supports the increasing role of the subtraction MRI for PD management, our study proposed that the contrast MRI without subtraction technique appears adequate in assessing femoral head perfusion. LEVEL OF EVIDENCE: Level I - Diagnostic study.

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.

Severe spontaneous intracranial hypotension and Marfan syndrome in an adolescent.

We describe a 14-year-old girl with Marfan syndrome who presented with severe postural headache. Dural ectasia was demonstrated radiologically. Cerebrospinal fluid (CSF) pressure was immeasurable on formal measurement. Radionucleide cisternography failed to demonstrate a CSF leak. We consider that the underlying fibrillinopathy in Marfan syndrome rendered the dura sufficiently permeable to CSF leakage to cause the low CSF pressure headache. The patient was treated successfully with epidural autologous blood patch.

MR imaging of dysplasia epiphysealis hemimelica: bony and soft-tissue abnormalities.

OBJECTIVE: The purpose of this study is to describe the bony and, to our knowledge, previously unreported associated soft-tissue abnormalities seen on MR imaging of dysplasia epiphysealis hemimelica. CONCLUSION: MR imaging accurately depicted bony and cartilagenous structural abnormalities in multiple planes and revealed previously undescribed secondary changes in menisci, tendons, ligaments, and muscle. MR imaging is of value in the assessment of patients with this disorder.

Variation in the diagnosis of vesicoureteric reflux using micturating cystourethrography.

Variability in the interpretation of micturating cystourethrography by paediatric radiologists for the diagnosis of vesicoureteric reflux in children was evaluated. All 265 micturating cystourethrograms (MCUs) that were available from 304 consecutive children aged 0.5-61 months-who were investigated after their first urine infection between 1993 and 1995 as part of a prospective cohort study-were selected for interpretation. Three experienced paediatric radiologists from the same department independently interpreted the MCUs according to the grading system of the International Reflux Study in Children, from grades 0 to V, with the presence of intrarenal reflux also noted. Apart from being informed that urine infection was the indication for the MCU, no other clinical information was given to the radiologists. The indices of variability used were the percentage of agreement and the kappa statistic, expressed as a percentage. Both measures were weighted with integers representing the number of categories from perfect agreement. Disagreement was analysed for children and kidneys. For the diagnosis of vesicoureteric reflux in individual patients, including grade, the percentage of agreement was 96%-97% (kappa 90%-91%) and the weighted percentage of agreement was 96%-98% (weighted kappa 93%-94%). The same high level of agreement was present for individual kidneys, with a percentage of agreement of 97%-98% (kappa 89%-92%) and a weighted percentage of agreement of 98%-99% (kappa 94%-95%). There was near perfect agreement in the interpretation of radiological micturating cystourethrography among three experienced paediatric radiologists for the diagnosis and grade of vesicoureteric reflux. Any variations in the medical care of children suspected of having vesicoureteric reflux are not explained by differences in the reporting of this diagnostic test.

Vesicoureteric reflux and timing of micturating cystourethrography after urinary tract infection.

OBJECTIVE: To test the medical belief that the micturating cystourethrogram (MCU) be deferred four to six weeks after acute symptomatic urinary tract infection (UTI) because of the risk of falsely detecting vesicoureteric reflux if performed earlier. STUDY DESIGN: A cross sectional analytic study of preschool children with first time symptomatic UTI. RESULTS: Of the 284 eligible children, 272 (95.8%) had MCU at a median time of 29 days after diagnosis (range 5 to 167 days). Vesicoureteric reflux was present in 77 children (28.3%). Beyond one week after diagnosis (270 children) the proportion and severity of vesicoureteric reflux detected was not associated with the timing of the MCU. Before one week, both children tested had vesicoureteric reflux. CONCLUSIONS: The presence and grade of vesicoureteric reflux is not influenced by the timing of the MCU one week after acute symptomatic UTI. There may be an association between the MCU and the presence of vesicoureteric reflux for children tested within one week after UTI. The MCU need not be deferred for four to six weeks after UTI.

Accuracy of MR imaging for estimating intraosseous extent of osteosarcoma.

OBJECTIVE: We compared how well T1-weighted and short inversion time inversion recovery (STIR) MR images obtained before and after preoperative chemotherapy reveal the extent of longitudinal intraosseous tumor involvement in osteosarcoma of children. MATERIALS AND METHODS: MR images were obtained at diagnosis and after preoperative multiagent chemotherapy in 20 children with osteosarcoma arising in the long bones. Images were reviewed to determine the length of the abnormal intraosseous signal intensity on paired longitudinal T1-weighted and STIR images taken at diagnosis and after chemotherapy. These measurements were compared with those made during a review of similarly oriented pathologic sections of the resected bone. Median differences were calculated and analyzed using Wilcoxon's signed-rank test. RESULTS: Abnormalities detected on T1-weighted images corresponded more closely to pathologic findings than did abnormalities detected on STIR images. On STIR images, readers overestimated tumor extent in 73% of both pre- and postchemotherapy studies. Readers overestimated tumor length on 29 of the 40 STIR images and on 13 of the 40 T1-weighted images. Readers underestimated tumor length on five STIR images and 11 T1-weighted images. Median differences between measurements made at the pathologic examination and on STIR images were statistically significant, both for imaging at diagnosis (p = .001) and for imaging after chemotherapy (p = .005); however, no significant differences were found between measurements made at the pathologic examination and measurements made on T1-weighted images. Measurements of tumor length on either type of imaging did not change significantly after chemotherapy. MR imaging showed 100% sensitivity for epiphyseal tumor spread but poor specificity. False-positive readings occurred in seven of 13 patients with abnormal signal intensity that extended into the adjacent epiphyses. CONCLUSION: Readers estimated intraosseous tumor extent more accurately on T1-weighted images than on STIR images. Readers overestimated tumor length on STIR images. T1-weighted longitudinal images taken before chemotherapy can be used for early planning of surgical approaches to osteosarcoma in children.

Partial sacral agenesis with constipation: a report of one family.

Seven first degree relatives in three generations of a family with partial sacral agenesis are reported. Anterior sacral meningoceles were found in five cases, four of whom had severe constipation, one with urinary voiding dysfunction, and another without constipation who had low pressure headaches and dyspareunia. The anomalad was transmitted in an autosomal dominant fashion with incomplete penetrance and variable expression. This entity should be considered in all children and adults with severe constipation from birth, a family history of constipation and/or where constipation is refractory to medical therapy.