Molecular Imaging and Nuclear Medicine

Molecular imaging uses small amounts of radioactive markers, called radiopharmaceuticals, in the visualization and diagnosis of disease, including many types of cancer, heart disease, neurological disorders and other abnormalities in the body.

Depending on the type of examination, the radiopharmaceutical is either injected in liquid form into a vein or swallowed by the patient, or it can be inhaled as a gas. The radiopharmaceuticals accumulate in the organ or area of the body being examined, where they give off energy in the form of gamma rays. This energy is detected by positron emission tomography (PET) or single photo emission (SPECT) scanner (Figure 1) 1. A computer is used to calculate the amount of radiopharmaceutical absorbed by the body and special images are produced providing details on both the structure and function of organs and tissues.

Fig. 1: SPECT image

Fig. 1: SPECT image

Molecular imaging procedures allow visualization of the structure and function of organs, tissue, bones or other systems of the body, e.g. heart blood flow and function, and kidney and lung function. Furthermore, molecular imaging scans are performed for a wide range of purposes from locating lymph nodes before surgery in patients with breast cancer or melanoma to evaluating bone fractures, infections and tumors or investigating abnormalities in the brain, such as seizures and memory loss.

Radiopharmaceuticals are also used to treat cancer and metastases, medical conditions affecting the thyroid gland, certain blood disorders and adrenal gland tumors in adults and nerve tissue tumors in children.

The amount of radioactive material used during these examinations depends on the individual procedure. The risk to the patient is comparably low, and experts consider the risks to be far outweighed by the benefits of an accurate diagnosis and treatment. Doctors and manufacturers know about these risks and are working together to minimize radiation dose. Nevertheless, women should always inform their physician or X-ray technologist if there is any possibility that they are pregnant.

1. St. Teresa's Hospital, Hong Kong