Dr Annmarie Jeanes, Consultant Paediatric Radiologist at Leeds Children’s Hospital, explains the different types of imaging your child may experience at the time of diagnosis, during treatment and follow-up
Huge advances in medical scans and imaging have taken place over the last two decades with significant improvements in both the quality of images and how quickly we can access the scans. As a result, complex and time-intensive imaging, such as magnetic resonance imaging (MRI), have become much more accessible for children.
These advances, together with better access to specialist children’s cancer imaging services, have played an important role in improving the quality of cancer care in children. Medical imaging plays a part in confirming your child’s cancer diagnosis, finding out where it is, whether it’s spread, planning the best treatment for it and assessing response to treatment.
A broad range of imaging types are now routinely used in children. This will depend upon their symptoms, the type of cancer they have and specific imaging recommendations of any clinical trials they may be enrolled in. Not all children will require the same imaging and some children will require more scans than others.
Some scans such as MRI, CT and some nuclear medicine examinations will require your child to remain very still. This can be difficult for some children and where required, infants or young children can be given a sedative or a general anaesthetic.
X-rays
‘X-rays’ are digital images formed by using small amounts of radiation which passes through the body. They are performed by a radiographer and are mostly used to examine bones, joints and the chest. They are quick, painless and readily available and usually completed within 15 minutes.
The chest and, less commonly, abdominal X-rays are the most common types performed in children with cancer. They are most useful if your child is unwell with acute symptoms.
Bone scans
This is a type of nuclear medicine scan which is used to look at your child’s bones and to look for spread of childhood cancer to the bones eg. rhabdomyosarcoma and certain bone tumours.
A small amount of radioactive material (isotope) is injected into your child’s vein and will accumulate in their bones. More radioactive isotope will collect in areas of active bone growth such as at the ends of long bones (legs), and in any tumour areas.
After the isotope is injected, your child will lie on a table under a camera called a gamma camera. The gamma camera detects radioactivity and creates pictures of the bones. The detectors are shaped like a box and lie above and below your child. They move from your child’s head to toes during the scan, taking pictures of the whole body.
Ultrasound scans
Ultrasound uses high-frequency sound waves to create pictures of the inside of your child’s body. A probe with a camera is placed on your child’s skin, together with some gel to make it move more easily. Ultrasounds aren’t painful or uncomfortable, but the gel may feel cold and sticky.
Ultrasounds are used to image the abdomen and soft tissues of the neck or limbs. They are usually performed by radiologists (doctors who specialise in imaging) or sonographers (radiographers trained in ultrasound).
Ultrasound is quick, readily available and highly accurate, and is likely to be the first type of imaging test your child will have. It’s well tolerated by children and has the advantage of being highly portable so can be performed on the ward if your child’s unwell or isolating.
It’s also commonly used to find out the best site for biopsy at diagnosis. After your child’s treatment has started, ultrasound can be used with CT or MRI to assess your child’s response of the cancer to chemotherapy, or treatment related to symptoms.
CT scans
CT uses X-ray technology to create detailed images of the inside of the body in places such as the head, neck, chest, abdomen and pelvis. It uses ionising radiation and all children’s scan departments will have protocols in place to make sure lower doses of radiation are used for children and adolescents.
CT scanners are large, doughnut-shaped machines, with a short tunnel in their centre, through which a table slides. Your child will need to lie on the table, which will move through the tunnel, during the scan.
They are used to image tumours of the brain, abdomen and pelvis, and are first choice to image the lungs, with its main role being to look for cancer nodules, which are too small to see on a chest X-ray.
CT is fast and readily available compared to MRI and most children won’t require a general anaesthetic. Therefore, it’s often performed at the time of initial diagnosis, where MRI isn’t available.
PET-CT scans
Positron emission tomography (PET-CT) is a nuclear medicine scan, which involves using a radiotracer combined with CT. Cancer cells usually function at a faster rate and, as a result, use more glucose (sugar) than normal cells. The cancer cells show up on PET scans as ‘hot spots’ which can be localised more accurately by combining the scan with the CT. PET-CT can also help assess how well treatment is working.
PET-CT is used routinely in children and adolescents with Hodgkin’s lymphoma, at diagnosis and in assessing response to treatment. It’s also recommended, where available, for seeing the spread of rhabdomyosarcoma, Ewing’s tumour and MIBG negative neuroblastoma within the child’s body.
MIBG scans
An MIBG scan is a nuclear medicine scan that uses ‘metaiodobenzylguanidine’, a radioactive iodine (an isotope). MIBG is a molecule that is absorbed by certain cancers such as neuroblastoma in children.
MIBG scans help confirm the diagnosis of these tumours and can detect disease which has spread to bones or other organs. It’s also used to assess whether the cancer is responding to chemotherapy.
MIBG scans take place over two days. On the first, your child will receive an injection of MIBG and a radioactive isotope which will accumulate in any neuroblastoma cells.
On the second day, the scan will take place using a gamma camera.
MRI scans
Similar to CT scans, MRI scanners are also large doughnut-shaped machines, with a short tunnel in the centre, which a table slides through. MRI uses radiowaves and a strong magnetic field to produce detailed pictures of the inside of your child’s body.
MRI gives more detailed images of the soft tissues and organs compared to CT scans and doesn’t involve the use of ionising radiation. MRI is therefore usually used in preference to CT to image the brain and spine, abdomen, pelvis and tumours of the soft tissues or skeleton.
Unlike CT scans, MRI technology is more complex and takes more time to produce an image resulting in much longer scanning times. Infants and young children (under the age of six) and claustrophobic or anxious older children, will usually need to have a general anaesthetic. MRI scans can be noisy due to the magnet and radiowaves. Headphones will be given to help mask the noise so children can listen to music, audiobooks or videos during the scan.
From Contact magazine issue 93 - December 2021
