Scans and Ongoing Investigations
There are many tests and procedures that may be required for children with cancer for the following purposes: diagnosis, staging, prognosis, monitoring during therapy and long term follow-up. Depending on the symptoms and type of cancer, an individual child may need none, some or all of these tests.
- Diagnostic Imaging – X-Rays, Ultrasounds, Magnetic Resonance Imaging (MRI), Computed Tomography (CT scan)
- Nuclear Medicine Tests – Bone scan, Gallium scan, MIBG scan, PET scan (Positron Emission Tomography)
X-Rays use radiation to penetrate solid structures like bones, showing up the inside parts of the body. They can show bone changes such as fractures, abnormal swelling or fluid in the lungs. X-Rays are quick procedures and do not cause pain. It’s a bit like having a photo taken.
Ultrasounds use high frequency sound waves to ‘show’ structures inside the body. Different tissues in the body absorb and reflect sound waves differently and these differences can be analysed by a computer to create an image of internal organs. Ultrasounds are performed by putting sgel on the skin and rubbing a probe over the area being scanned. They do not hurt and do not require any anaesthetic.
Magnetic Resonance Imaging (MRI)
An MRI uses high frequency radio waves and a powerful magnetic field to construct images of virtually any part of the body and it is one of the most sensitive imaging tools available.
To obtain the images, the child is placed in a large magnet in the shape of a long tube. The process is painless but an MRI can be very noisy and some children may feel frightened inside the tube. It is vital the child remains still so it is sometimes necessary to give young children some sedation or a general anaesthetic as an MRI may take a long time (30-90 minutes). It does not use any radiation.
CT Scans (Computed Tomography)
A CT (Computerised Tomography) scanner uses x-rays and a computer to make pictures of the inside of your body. It is similar to a plain x-ray however it takes lots of pictures of a section (cross sections) of your body instead of just one.
The child may be asked to drink a special liquid or be given a special x-ray dye by an injection to make the scan more effective.
The scanner has a round opening in the centre and a flat bed for the patient to lie on. While lying on the bed, it will slowly move into the opening where the pictures are taken. The movement is controlled by the CT staff.
A CT scan is not dangerous or painful but the child must lie still for up to 15 minutes. In very young children, sedation or a general anaesthetic may be required. Our new, state-of-the-art CT scanners use very low doses of radiation and are super fast. They can take images of a whole area in less than a second so even young children often do not need anaesthetics.
Nuclear Medicine Tests
Nuclear medicine uses small amounts of unsealed radioactive materials (radiopharmaceuticals) to diagnose and treat disease. Nuclear medicine imaging is unique in that it provides doctors with information about both the anatomy of the body and its physiology (function).
Nuclear medicine tests are safe and painless. They allow quick and accurate diagnosis of a wide range of conditions and diseases.
All nuclear studies require the injection of a tiny amount of radioactive compound called a radiotracer. The amount of radioactivity used is so small that it carries no risk and is eliminated from the body soon afterwards.
A bone scan takes images of the bones to find any tumour or infection present. It involves an injection of a radiotracer two hours before the scan is actually done. The radiotracer spreads to any parts of the bone that are not normal.
Children under five years usually need to be sedated so they remain still. The scan itself does not hurt but takes around an hour.
Gallium is a chemical absorbed by certain areas of inflammation, infection or types of cancer (such as lymphoma).
A gallium radiotracer is injected about 24-48 hours before the scan takes place. The scan takes about an hour.
Gallium is absorbed and excreted through the bowel (gut) so it is necessary for the child to take a laxative until after scanning is completed, otherwise a full bowel can give false results.
MIBG is a chemical that accumulates in certain types of tumours, particularly neuroblastoma. A small amount of radioactive iodine is injected (as a radiotracer), then 18-48 hours later the scan is done showing how the tumour has absorbed the radiotracer.
For four days prior to the radiotracer being injected, your child will be given oral Lugols Iodine twice a day, diluted in milk or orange juice (never undiluted). This will continue until after scanning is completed.
The scan takes around 1.5 hours and children under five years will usually need to be sedated.
PET scan (Positron Emission Tomography)
Like other nuclear tests, a PET scan involves an injection of a small amount of radiotracer. A period of 45 minutes is allowed to pass before the PET scanner is then used to look at the distribution of the radiotracer throughout the body. This takes around 45 minutes so sedation for smaller children may be required.
PET scans are used most often to detect cancer and to examine the effects of therapy by looking for certain biochemical changes in the cancer. For four hours prior to the scan, your child will not be able to eat.
A CT scan is performed at the same time as the PET scan, to improve image quality.
- This is a surgical procedure that allows cells to be collected so they can be examined under a microscope. The biopsy can be done in one of two ways:
Open Biopsy – the skin is opened during surgery under general anaesthetic and the surgeon removes a sample of tissue.
Closed Biopsy – a needle is inserted into the tissue without cutting open the skin (for example a fine needle aspirate or a core biopsy).
- The type of biopsy and anaesthetic used will depend on where the tumour is in the body.
- For some cancers, a diagnosis can be made within two days, but more commonly it takes about a week or more for all the tests to be completed.
- Bone marrow aspiration (BMA) and biopsy (trephine) – a needle is inserted into a bone (usually the hipbone at the back) while the child is under general anaesthetic. A BMA is done to look at the blood cells in the bone marrow whereas a trephine is done to study an actual piece of the bone and looks at the architecture of the marrow space.
Bone marrow is the liquid spongy part inside the bone where the blood cells are made. A BMA and trephine are usually carried out either to make a diagnosis of leukaemia or lymphoma, or to find out whether cancer cells from a solid tumour (eg neuroblastoma) have spread to the bone marrow.
- Lumbar Puncture (LP) – A lumbar puncture needle is inserted into the spinal cord (between the vertebrae in the lower back) in order to collect a specimen of cerebrospinal fluid (CSF). CSF is the fluid that surrounds the brain and spinal cord and a biopsy of this fluid is necessary to ascertain whether disease has spread to these areas.
LPs are also used to inject chemotherapy drugs into the CSF, to either treat or prevent the growth of cancer or leukaemia cells in the central nervous system.
- Useful for diagnosis as they show the different types and proportions of blood cells present in a child’s blood and any abnormal cells such as leukaemic cells.
- Blood tests can show the functions of organs such as the kidneys, liver, lungs and muscle which is useful for both diagnosis and ongoing assessment.
- Common blood tests include:
Full Blood Count (FBC) – looking at red (Hb) and white cells and platelets
Urea Electrolyte Creatinine (UEC) – to check kidney function
Liver Function Tests (LFT)
Calcium Magnesium Phosphorus (CMP)
Serology – checking for evidence of exposure to infection
Tumour Markers – for specific tumour types only
Coagulation Studies – checking the clotting ability of blood
- Blood cultures – a test to find and identify any bacteria or fungi that have infected the blood stream. A child who develops a fever may have a blood culture done to find out what type of infection is causing the illness and which antibiotics are likely to be most effective.
Cardiac Function Tests
- Used to assess the heart for any adverse effects of treatment or complications of disease
Echocardiogram (Echo): an ultrasound of the heart to measure the motion of the walls of the heart and the heart valves by using sound waves.
Electrocardiogram (ECG): records the electrical activity of the heart. Rubber pads (little stickers) called electrodes are attached to the child’s wrists, legs and chest, and recordings are made by a machine onto a strip of paper. This test is not painful and has no side effects.
Kidney Function Tests
- Glomerular Filtration Rate (GFR) – a special dye is injected intravenously, after which blood samples are taken to measure how much dye remains in the blood. This test shows how well the kidneys are working by measuring how quickly they remove the dye from the blood.
- Urinalysis – Chemical and microscopic examination of the urine to evaluate kidney function and to determine if there is any infection in the urinary tract.
Lung Function Tests
- Measures how well a lung can fill with air and then empty. It looks at whether disease, medication or infection has affected the way in which the lungs work.
- It is only performed on children who are five years or older as a certain level of ability is required to use the equipment.