What is Scintigraphy?

Scintigraphy can be requested for many situations. For example, to locate an occult primary tumour or inflammatory or infectious disease; to assess whether a cancer has affected the bones; to see the functioning of the heart or its blood flow in suspected cases of coronary disease or in cerebral blood flow; in renal or digestive function; or to confirm or rule out thyroid problems. 

There are two ways to acquire the images: 

• Static acquisition. This consists of obtaining a single image during a certain period of time. A number of static images taken around the patient is known as SPECT and can be acquired together with a Computed Tomography (CT) scan to provide SPECT/CT images. 

• Dynamic acquisition. This consists of several images taken during a given time interval.  

Currently, these different scintigraphy types can provide early diagnosis of disease in various specialities: bone, cardiology, oncology, endocrinology, neurology, nephrology and urology, pulmonology, haematology, digestive system, infectious pathology, peripheral vascular system and paediatrics. 

Preparation for the scan depends on the specific type of examination and the medical condition being evaluated. The general guidelines are: 

1. Inform the health professional about any medical condition, allergy or medication being taken. 

2. Wear comfortable clothing, preferably without metal zips or buttons, as they can interfere with the image. 

3. Drink plenty of fluids before and after the test, as this helps clear the radiopharmaceutical from your system more quickly. 

4. You do not have to fast, except for some types of scintigraphy, such as thyroid, gastric emptying and scanning with I-131. 

5. Avoid caffeine, nicotine and strenuous exercise for at least 24 hours before the exam, as they can affect the results. 

6. If you are breast-feeding, pregnant or suspect you may be, inform your healthcare professional or nuclear medicine nurse beforehand, as some types of nuclear medicine imaging may not be recommended during pregnancy or lactation. 

7. Arrive early for the appointment and leave enough time for the examination and any additional paperwork that may be necessary.  

8. Depending on the type of test, you may have to stay in the imaging centre for several hours after injection, to give time for absorption of the radiopharmaceutical and for taking the images at the optimal time. 

9. Close contact with pregnant women or children must be avoided for as long as indicated by the nuclear medicine nursing staff.  

A small amount of a radiopharmaceutical ̶ which is a radioactive compound that emits gamma rays ̶ is administered; these are then detected by a gamma camera. The gamma camera is placed over the study area and creates images that show the distribution of the radiopharmaceutical within the body. The nuclear medicine specialist then analyses the images to diagnose or evaluate the medical condition. 

The specific steps for performing a scintigraphy vary depending on the type of test being performed; however, these are the general ones: 

• A small amount of the radiopharmaceutical is administered to the patient (orally or intravenously, depending on the type of test). 

• The patient waits a certain time for the radiopharmaceutical to be distributed throughout the body. 

• After this waiting period, the patient lies down, immobile on a bed. The gamma camera is placed on the area of interest and detects the gamma rays emitted by the radiopharmaceutical. 

• In some types of scintigraphy, the patient may be asked to change position during the process to obtain images from different angles. 

• Once the test is finished, the patient may be asked to wait while the images are reviewed by the nuclear medicine specialist, to check if they can be used for assessment. 

• The radiopharmaceutical administered breaks down naturally after the examination, and is eliminated from the body in the urine and faeces. The patient is advised to drink fluids to help clear the radiopharmaceutical from the system more quickly. 

The scan is performed by a qualified team of nuclear medicine specialists. The team includes:  

• A nuclear medicine specialist. Responsible for interpreting the examination results from the images obtained and determining the best course of treatment. 

• Radiopharmacist. Responsible for radiopharmaceutical management. 

• Nuclear medicine nursing staff. They assess the patient beforehand and administer the radiopharmaceutical based on the test indicated by the specialist. 

• Diagnostic imaging technician. Responsible for operating the gamma camera and ensuring patient safety during the examination.  

• Biomedical engineer. Responsible for creating and supervising the image acquisition, reconstruction and processing features. 

• Radiophysicist. A specialist who ensures the gamma camera works properly and the radiation dose administered to the patient is safe and adequate. 

All team members are trained professionals who work together to ensure the examination is performed safely and accurately and that the patient receives the best care possible. 

The time taken for the scintigraphy test varies according to the type performed. Some procedures may only take a few minutes, while others may require several hours or be performed over several days. 

For example, a bone scan typically takes 2-3 hours to complete, while a thyroid scan typically takes an hour. Meanwhile, cardiac stress scintigraphy can take several hours; since the patient has to exercise or take medication to increase the blood flow to the heart before the image is taken. 

You should arrive on time for your appointment and follow the preparation instructions provided by your healthcare team to ensure the examination is performed efficiently and accurately. 

Most patients do not experience any discomfort during a scan. However, other patients may experience the following: 

• Discomfort from the injection. A little discomfort or pain at the injection site, if the radiopharmaceutical is administered by intravenous injection. 

• Heat or cold. A sensation of warmth or cold may be felt as the radiopharmaceutical is absorbed. 

• Nausea. Mild nausea or a metallic taste in the mouth may be a side effect of the radiopharmaceutical. 

• Need to urinate. The need to urinate more often, as the radiopharmaceutical is removed from the body. 

• Claustrophobia. Because they have to remain still in a confined space during imaging, some patients can feel claustrophobic or anxious. 

You should inform a healthcare team member if you experience any discomfort or side effects during the scan. 

Scintigraphy is considered a safe, non-invasive imaging technique. However, there are potential complications associated with the use of radiopharmaceuticals: 

• Allergic reaction. In very rare cases, patients may experience an allergic reaction to the radiopharmaceutical injection, causing symptoms such as hives or itching. 

• Radiation exposure. The dose administered in a scintigraphy procedure is very low and the risk of long-term side effects is generally low, so it does not interfere with normal life. 

• Pregnancy and lactation. Pregnant or breastfeeding women should inform their healthcare professional before undergoing a scintigraphy to minimise the radiation received by the foetus or infant. 

You should discuss any risks or concerns with the specialist before undergoing scintigraphy.