Bone scans (HDP Tc99m)
The principle of the test is visualisation of living bone, or more accurately, visualisation of the living molecules that make up bone tissue. This test is extraordinarily sensitive in detecting any abnormality within living bone. It is far more sensitive that x-ray, CT or even MRI in the detection of fractures and is the most sensitive means of detecting malignant tumour in bone. The entire skeleton can be surveyed easily and rapidly with modern Nuclear Medicine equipment. This test is also extremely useful for assessment of bone and joint pain following sporting activities or in the many forms of arthritis. It also has an important role in detecting infection in bones and joints.
Involve imaging with the gamma camera directly after the injection. Images demonstrate the pooling of blood in the veins. This too may indicate inflammation. Blood pool imaging is very useful to demonstrate inflammation in joints of patients with symptoms of arthritis, and may allow a specific diagnosis of particular types of arthritis, e.g. rheumatoid arthritis. This also allows the doctor to accurately locate and identify the source of joint or bone pain so that appropriate treatment can be started.
Each patient having a bone scan should be encouraged to be relatively mobile during the intervening period and also remain well hydrated.
VQ Scan (DTPA, Maa Tc99m)
VQ scans are scans of the lungs showing the distribution of air into the lung fields, and also showing the distribution of blood in the lungs. The lungs are made of multiple segments each with its own air and blood supply. The test is most commonly used to diagnose a clot in the lung (pulmonary embolus).
The patient inhales an inert gas mixture that contains extremely small particles of radioactive material (Tc-99m). This is in the form of a product called Tc-99m diethylene-triamine-penta-acetic acid (DTPA). The patient is then positioned comfortably for scanning with a gamma camera. Following this the patient is given a small intravenous injection of radiotracer (Tc-99m macro-aggregated albumin) that distributes throughout the blood vessels of the lungs. The patient is then positioned comfortably for further scanning. The scan takes a total time of about one hour to perform.
pdf Please click here to download a leaflet on VQ scans for pregnant patients. (645 KB)
Gastric emptying (MAA Tc99m)
Gastric emptying is used to investigate patients who have bloating after meals or other digestive problems. In patients with diabetes the nerves supplying the gut may be damaged and the stomach may not empty as quickly as it should. This scan allows measurement of how rapidly the stomach empties after a standardised meal is given.
A standardised meal is prepared (usually scrambled egg on toast) where a small amount of radioactive tracer (Tc-99m maa) is incorporated into the meal. Having eaten the meal the patient is positioned in front of a gamma camera in a comfortable position for imaging of the stomach. The test takes approximately four hours to complete.
HIDA biliary scan (Tc99m HIDA)
This scan is also known as a HIDA scan. Its role is to demonstrate the flow of bile in the body. Bile produced by the liver is stored in the gall bladder and then released on demand through bile ducts into the bowel to aid digestion. This test follows the flow patterns of bile. This test can demonstrate blockages of bile ducts (both inside the liver and outside the liver), reflux of bile into the stomach and, with the aid of a hormone drug known as cholecystokinin, can show whether the gall bladder and the important muscles at the junction of the main bile duct and the bowel (the sphincter of Oddi) are working normally. The test is usually used for patients with abdominal pain that is thought to be due to problems with the gall bladder or bile ducts.
The patient is prepared by fasting for about 6-8 hours. The patient should not fast for more than 8 hours. A small intravenous cannula is placed in the arm and through this a small amount of radioactive tracer, known as Tc-99m HIDA (an iminodiacetic acid derivative) is given. The patient is then comfortably positioned and imaging is performed using a gamma camera. This usually takes about one hour. Following this, when the gall bladder has filled sufficiently the patient is given Calogen a strawberry flavoured drink. This will cause the gall bladder to contract and will also have other effects on the bile ducts. Occasionally patients may feel some crampy discomfort in the abdomen but most notice little change. When this has finished the examination is complete.
Tektrotyd (Tc99m) is used to detect the presence of an unusual uptake. The chemical tektrotyd, used for the scan in combination with a radioactive material (Tc99m), is chemically similar to this hormone. The scan is most often used to detect abnormal tissue growth known as a carcinoid.
The scan is expensive to perform, and therefore it is recommended that only patients with a high clinical likelihood of having a positive diagnosis be scanned. The scanning procedure is relatively uncomplicated and involves a small intravenous injection of radiotracer Tektrotyd Tc99m). 2 hours later the patient is positioned comfortably for scanning and a gamma camera images the whole body. This takes about 30-40 minutes. The whole process is repeated at 4 hours.
This scan uses single photon emission computed tomography (SPECT) that allows cross-sectional imaging and when combined with a low-dose computed tomography (CT) scan allows accurate anatomical localisation of the tumour.
White Cell (Labelled Tc99m)
This Nuclear Medicine scan is a means of detecting infection in bone, joints and soft tissue as well inflammation due to other causes, such as inflammatory bowel disease (ulcerative colitis and Crohn’s disease).
The patient has a cannula /butterfly placed in an arm vein and a small amount of blood is withdrawn. The blood is taken to a pharmacy where the white blood cells are separated and mixed with a small amount of radioactive material (Tc-99m) before it is returned to the patient via the cannula. The patient is then positioned under the gamma camera on a comfortable scanning bed. The procedure can take up to 6 hours, and usually consists of a brief early scan before the patient has a break and returns four to five hours later for the main scan that takes approximately an hour.
This is a means of demonstrating the presence or absence of a rare cause of bleeding into the gut, known as Meckel’s diverticulum. This is a congenital outpouching, often in the distal small bowel that may contain some cells similar to the acid producing cells found in the stomach. This acid may cause ulceration and bleeding.
Other than several hours of fasting, no specific preparation is required. However, occasionally special medications (pentagastrin) may be used to better prepare the patient. The Nuclear Medicine physician will explain this to the patient at the time of booking. The patient is given a small intravenous injection of Tc-99m pertechnetate. The patient is then positioned comfortably whilst a gamma camera acquires images of the abdomen and pelvis regions. The imaging usually takes about an hour to complete.