Following our previous introduction to the field of Nuclear Medicine, explaining what it is and its key features, in this second part we introduce the diagnostic tools used in this specialty.
Diagnostic tools used in Nuclear Medicine
These can be divided into two main groups: imaging devices using radiopharmaceuticals and other equipment within Nuclear Medicine.
1. Imaging devices using radiopharmaceuticals
1.1 Gamma Camera / SPECT (Single Photon Emission Computed Tomography) This is a primary tool in Nuclear Medicine, used to assess the function of various organs such as bones, kidneys, heart, and thyroid gland. It produces both 2D (planar imaging) and 3D (SPECT) images. Commonly used radiopharmaceuticals include Technetium-99m (Tc-99m), which provides high-quality images and is very safe, making it suitable for clinical use.
1.2 PET/CT Scanner (Positron Emission Tomography/Computed Tomography) This device offers high-resolution imaging by combining PET, which shows cellular-level function, with CT, which provides detailed anatomical information, in a single machine. It allows assessment of lesion location, size, anatomical characteristics, and tissue tracer uptake. It is especially useful for evaluating cancer, disease spread, and monitoring treatment response.
2. Other equipment within Nuclear Medicine
2.1 Dual-energy X-ray Absorptiometry (DXA) This device measures bone mineral density (BMD) to help diagnose osteoporosis and assess fracture risk, as well as monitor treatment. Unlike other tests, it does not require injection of radiopharmaceuticals, using instead low-energy X-rays emitted directly from the machine. The test is quick, involves low radiation exposure, and is highly accurate.
2.2 Other equipment Examples include radiation dose meters, shielding systems, and quality control systems to ensure patients receive appropriate and safe radiation levels.
Nuclear Medicine examination procedures
The steps of a Nuclear Medicine exam vary depending on the organ or system being studied. However, the general procedure is as follows.
Administration of radiopharmaceuticals
A doctor or technician administers the radiopharmaceutical to the patient by intravenous injection, oral intake, or inhalation, depending on the type of exam. An exception is the DXA scan, which does not require radiopharmaceutical injection because the radiation comes directly from the machine.
Waiting period for radiopharmaceutical distribution
After administration, patients usually wait for the radiopharmaceutical to distribute and accumulate in the target organ before imaging. The waiting time varies based on the exam type and radiopharmaceutical used. During this period, designated areas are provided for patient comfort and safety. Some exams involve immediate imaging during injection without a waiting time.
Imaging with the diagnostic device
Patients lie on the examination table in the appropriate position while the device captures images of radiopharmaceutical distribution. The procedure is generally painless and quiet.
Overall exam duration
Exam length varies by type and organ system. Some exams require multiple imaging sessions. Including waiting time, certain tests can last up to 4 hours after radiopharmaceutical administration, or patients may be scheduled for imaging days later. Each imaging session typically lasts no more than 5 to 30 minutes in clinical practice (research scans may last up to 90 minutes).
Post-exam care instructions
After the exam, patients are generally advised to drink plenty of water to help eliminate the radiopharmaceutical through urine and to urinate frequently. They should avoid close contact with young children or pregnant women for a period depending on the exam type. Nursing mothers may be advised to temporarily stop breastfeeding during the time the substance remains in breast milk and to pump and discard milk to maintain supply.
Pre-exam recommendations
Nuclear Medicine is a radiology specialty using radiopharmaceuticals for diagnosis and treatment. It does not cause permanent radiation residue because radioactive substances are eliminated by the body's excretory systems. Radiation doses used in diagnostic exams are low and strictly controlled for safety. Side effects are rare and usually mild, so patients can confidently undergo Nuclear Medicine examinations and treatments.
Information provided by Associate Professor Dr. Kanungnit Thammanirat, Department of Nuclear Medicine, Radiology Division, Faculty of Medicine Ramathibodi Hospital, Mahidol University.