Paediatric nuclear medicine imaging

Abstract

Background

Nuclear medicine imaging explores tissue viability and function by using radiotracers that are taken up at cellular level with different mechanism. This imaging technique can also be used to assess blood flow and transit through tubular organs. Nuclear medicine imaging has been used in paediatrics for decades and this field is continuously evolving.

Sources of data

The data presented comes from clinical experience and some milestone papers on the subject.

Areas of agreement

Nuclear medicine imaging is well-established in paediatric nephro-urology in the context of urinary tract infection, ante-natally diagnosed hydronephrosis and other congenital renal anomalies. Also, in paediatric oncology, I-123-meta-iodobenzyl-guanidine has a key role in the management of children with neuroblastic tumours. Bone scintigraphy is still highly valuable to localize the source of symptoms in children and adolescents with bone pain when other imaging techniques have failed. Thyroid scintigraphy in neonates with congenital hypothyroidism is the most accurate imaging technique to confirm the presence of ectopic functioning thyroid tissue.

Areas of controversy

Radionuclide transit studies of the gastro-intestinal tract are potentially useful in suspected gastroparesis or small bowel or colonic dysmotility. However, until now a standardized protocol and a validated normal range have not been agreed, and more work is necessary. Research is ongoing on whether magnetic resonance imaging (MRI), with its great advantage of great anatomical detail and no ionizing radiations, can replace nuclear medicine imaging in some clinical context. On the other hand, access to MRI is often difficult in many district general hospitals and general anaesthesia is frequently required, thus adding to the complexity of the examination.

Growing points

Patients with bone pain and no cause for it demonstrated on MRI can benefit from bone scintigraphy with single photon emission tomography and low-dose computed tomography. This technique can identify areas of mechanical stress at cortical bone level, difficult to demonstrate on MRI, which can act as pain generators. Positron emission tomography (PET) is being tested in the staging, response assessment and at the end of treatment of several paediatric malignancies. PET is becoming more widely utilized in neurology in the pre-surgical assessment of some children with drug resistant epilepsy.

Areas timely for developing research

The use of PET/MRI scanners is very attractive as it combines benefits of MR imaging with the assessment of cellular viability and metabolism with PET in one examination. This imaging technique will allow important research on tumour in-vivo metabolism (possible applications include lymphomas, neuroblastomas, malignant germ cell tumours andbrain tumours), with the aim of offering a personalized biological profile of the tumour in a particular patient. Ground-breaking research is also envisaged in neurosciences, especially in epilepsy, using PET tracers that would enable a better identification of the epileptogenic focus, and in psychiatry, with the use of radiolabeled neurotransmitters. In paediatric nephro-urology, the identification of the asymptomatic child with ante-natally diagnosed hydronephrosis at risk of losing renal parenchymal function if left untreated is another area of active research involving radionuclide renography.

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