Derek J. Roebuck

Hepatobiliary rhabdomyosarcoma in children: diagnostic radiology.

Abstract Rhabdomyosarcoma (RMS) occurs infrequently in the liver and biliary tree. Although the radiological diagnosis may be simple when the tumour involves the extrahepatic bile ducts, no specific imaging features are known for hepatic RMS. We present four cases and discuss the role of diagnostic radiology in the management of this tumour.

Potential utility of MRI in the evaluation of children at risk of renal scarring.

Background. Gadolinium-enhanced MRI has recently been employed in the diagnosis of acute pyelonephritis. Its potential utility in the diagnosis of renal scars in children is unknown. Objective. To evaluate the potential utility of MRI using fat-saturated T1-weighted (T1-W) and post-gadolinium, short-tau inversion-recovery (STIR) sequences in detecting renal scarring by comparison with technetium dimercaptosuccinic acid (99 mTc-DMSA) renal scintigraphy in children at risk of renal scarring. Materials and methods. A group of 24 children with spina bifida and neurogenic bladder or anorectal anomaly was studied. No patient had a history of acute pyelonephritis. Documented urinary tract infection (UTI) was present in 10 children (42 %). The remaining 14 (58 %) children had a history of asymptomatic bacteriuria. None had clinical signs or symptoms of acute UTI at the time of the study. 99 mTc-DMSA and MRI were performed to detect renal scarring. 99 mTc-DMSA scans were supplemented with pinhole imaging. MRI of the kidneys employed a fat-saturated T1-W sequence and a post-gadolinium STIR sequence employing a short echo time. Results. Of the kidneys studied, 33 % (n = 16) had evidence of a renal parenchymal defect suggestive of scarring on 99 mTc-DMSA. The concordance in the detection of a scarred kidney by post-gadolinium STIR sequence and 99 mTc-DMSA is 94 %; that by fat-saturated T1-W sequence and 99 mTc-DMSA is 82 %; that by both sequences (positive result on either sequence) and 99 mTc-DMSA is 100 %. Using 99 mTc-DMSA as the gold standard, MRI had a sensitivity of 100 % and a specificity of 78 % in the diagnosis of a scarred kidney. The concordance in the detection of a scarred zone by post-gadolinium STIR sequence and 99 mTc-DMSA is 68 %; that by fat-saturated T1-W sequence and DMSA is 44 %; that by both sequences (positive result on either sequence) and 99 mTc-DMSA is 84 %. MRI had a sensitivity of 84 % and a specificity of 86 % in the diagnosis of a scarred zone, using 99 mTc-DMSA as the gold standard. Conclusion. The detection rate for renal scarring on MRI using the fat-saturated T1-W and post-gadolinium STIR sequences is comparable to planar 99 mTc-DMSA. MRI is of potential utility in the evaluation of children at risk of renal scarring.

Imaging features of pancreatoblastoma

Background. Pancreatoblastoma is a rare tumour of childhood. Reports of the imaging appearances are limited. Objective. To define the imaging features of pancreatoblastoma by analysis of four previously unreported cases and review of the literature. Materials and methods. Findings at CT (n = 4), US (n = 3) and MRI (n = 2) were retrospectively reviewed in four patients with pancreatoblastoma. A Medline search was performed to identify relevant literature. Results. Pancreatoblastoma arises most frequently in the body and/or tail, or involves the entire pancreas. Ultrasonography, CT and MRI show variable imaging features, but should in most cases permit preoperative distinction of pancreatoblastoma from other tumours that occur in this region in infancy and childhood. Detection of metastases in the liver, lymph nodes and peritoneal cavity is not significantly better with any one of these three modalities. Conclusion. Preoperative imaging with US, CT and/or MRI will usually suggest a correct diagnosis of pancreatoblastoma. Contrary to previous reports, the tumour arises in the pancreatic head in a minority of cases.

Alveolar soft-part sarcoma: a rare soft-tissue malignancy with distinctive clinical and radiological features

Abstract Alveolar soft-part sarcoma (ASPS) is a rare tumour. Certain distinctive clinical and radiological features suggest the correct diagnosis. There is moderate predilection for young women. ASPS almost always arises in skeletal muscle and occurs most frequently in the lower limbs. There is often a long clinical history and a large mass at presentation. Two young females with ASPS presented with very vascular tumours in the thigh, with prominent intra- and extra-tumoural blood vessels. The imaging findings and the existing literature are reviewed.

Long-term cerebral metabolite changes on proton magnetic resonance spectroscopy in patients cured of acute lymphoblastic leukemia with previous intrathecal methotrexate and cranial irradiation prophylaxis.

PURPOSEnTo evaluate the long-term brain metabolite changes on (1)H-MRS in acute lymphoblastic leukemia (ALL) patients who had intrathecal methotrexate (ITMTX) and cranial irradiation (CRT) for central nervous system (CNS) prophylaxis against CNS relapse.nnnMETHODS AND MATERIALSnThirty-seven ALL patients (12 females, 25 males) with history of ITMTX and CRT for CNS prophylaxis were studied. Age ranges at the time of diagnosis and at magnetic resonance examination were 0.8-13 years and 12-27 years, respectively. The interval since diagnosis was 5.6-19 years. T2-weighted and gradient-recalled echo (GRE) magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy ((1)H-MRS) were performed to assess brain injury.nnnRESULTSnOn MRI, 3 leukoencephalopathy (LEP) and 1 infarct were detected. Twenty-two patients had evidence of hemosiderin. On (1)H-MRS no statistically significant difference in choline (Cho)/creatine (Cr) and N-acetylaspartate (NAA)/Cr was associated with LEP. A lower Cho/Cr (p = 0.006) and NAA/Cr (p = 0.078) was observed in brains with hemosiderin. Linear-regression analysis showed no statistically significant relationship between NAA/Cr or Cho/Cr with age at diagnosis, but there was a statistically significant decreasing trend of NAA/Cr and Cho/Cr with the interval since diagnosis.nnnCONCLUSIONnLong-term brain injury in ALL survivors after CNS prophylaxis with ITMTX and CRT was reflected by decreasing NAA/Cr and Cho/Cr with the interval since diagnosis. The lower Cho/Cr associated with hemosiderin but not LEP suggested a different pathophysiology for these brain lesions.

Risk and benefit in paediatric radiology

Abstract An investigation requiring the use of ionising radiation can be justified by showing that its benefits are likely to exceed its risks. The risks can be estimated from the effective dose by using the system recommended by the International Commission on Radiological Protection. The benefits of investigations in paediatric radiology are currently unquantified. We can assume that some tests have potential benefits so large that further evaluation is unnecessary. Others have a maximum potential benefit so low that they can be discarded. For most investigations, however, research into the magnitude of benefit to the patient is required in order to establish that it is greater than the magnitude of the radiation risk.

A technique for enhancing union of allograft to host bone

The aim of limb-salvage surgery in malignant bone tumours in children is to restore function and eradicate local disease with as little morbidity as possible. Allografts are associated with a high rate of complications, particularly malunion at the allograft-host junction. We describe a simple technique which enhances union of allograft to host bone taking advantage of the discrepancy in size between the adult allograft and the childs bone. This involves lifting a flap of periosteum before resection from the host bone, which is then telescoped into the allograft medullary canal, which may require internal burring or splitting, for a distance of 1.5 to 2 cm and covering the bone junction with the periosteal flap. This is more stable than conventional end-to-end opposition. For each centimetre of telescoping the surface area available for bony union is increased more than three times. The periosteal flap also augments union. Additional surface fixation with a plate and screws is not necessary. We have used this technique in nine children, in eight of whom there was complete union at a mean of 16 weeks. Delayed union, associated with generalised limb osteoporosis, occurred in one. Early mobilisation, with weight-bearing by three weeks, was possible. There was only one fracture of the allograft.

External and internal-external biliary drainage in children with malignant obstructive jaundice.

Background. Obstructive jaundice is an uncommon but important clinical problem in children with cancer. Percutaneous transhepatic biliary drainage is widely used to relieve malignant biliary obstruction in adults, but its use in children has not been well described.¶Materials and methods. Six patients aged between 1 and 17 years underwent external or internal-external biliary drainage to relieve malignant obstructive jaundice. Biochemical, haematological and microbiological parameters were measured before the procedure and repeated 7–9 days later.¶Results. External or internal-external biliary drainage was technically successful in all patients. No patient developed clinically significant biliary sepsis. Asymptomatic duodenal perforation occurred in one patient with bulky duodenal tumour following conversion from external to internal-external drainage.¶Conclusions. External biliary drainage may be successfully performed in children with malignant obstructive jaundice.

Sellar and suprasellar medulloepithelioma

Abstract Medulloepithelioma is a rare tumour with a very poor prognosis. The most frequent site in the central nervous system is the cerebral hemispheres. Appearances on MRI are very variable, possibly reflecting the divergent forms of differentiation seen at histological examination. We report a rare case of sellar and suprasellar medulloepithelioma in a 2-year-old boy and discuss the imaging, differential diagnosis and pathologic findings.