Introduction of Nuclear Medicine
Nuclear medicine is a relatively minor discipline compared to more established disciplines like internal medicine, surgery, and obstetrics and pediatrics. It utilizes nuclear technology to diagnose, treat, and research diseases. As one of the hallmarks of medical modernization, nuclear medicine has experienced rapid growth in recent years.
Description of Nuclear Medicine
Nuclear medicine investigations encompass various sample analyses, radionuclide functional imaging techniques—especially SPECT, SPECT/CT, PET/CT, and PET/MR scans—and targeted functional studies. This multiparametric approach is now a mainstay for recognizing and elaborating systemic diseases. Key use cases include surveys of the skeleton for assessing bone disease, thyroid scans targeting thyroid dysfunction, renal and ectopic gastric wall investigations, hepatobiliary evaluations, myocardial perfusion mapping, preoperative detection of sentinel lymph nodes, plus the initial or repeat staging of both primary and secondary tumors. Distinct from ultrasound, CT, and MRI, which emphasize structural anatomy, nuclear imaging captures metabolic and physiological behavior instead. The visualization of ongoing biological activity permits tissues or lesions to be evaluated even while subclinical or diminutive. Whole-body bone scintigraphy, the workhorse of nuclear imaging, demonstrates the capacity to identify skeletal metastasis three to six months before conventional radiograph confirmation, and the latest PET-CT platforms have documented the ability to visualize suspicious lesions six to twelve months ahead of traditional anatomical techniques.
Where does the radiation from nuclear medicine exams come from?
Unlike radiology, CT scans, and radiotherapy, nuclear medicine tests are performed after the patient takes or is injected with a radiopharmaceutical. The patient is essentially moving the radiation source, radiating it around them like the sun. In contrast, patients in radiology, CT scans, and radiotherapy departments receive external radiation. Once outside the radiation room, they are treated just like ordinary people.
Is radiation exposure safe in nuclear medicine?
It's safe for nuclear medicine candidates!
A whole-body bone scan provides only about half the radiation dose of an abdominal CT scan. The radiation dose of a PET-CT scan is similar to that of a chest contrast-enhanced CT scan.
Nuclear medicine examinations are generally unnecessary for pregnant women and children, but they are not absolutely contraindicated and can be performed if necessary.
Breastfeeding women can also undergo nuclear medicine examinations if necessary. A 10 mCi 18F-FDG PET scan only requires stopping lactation for two hours, while a 20 mCi 99mTC-MDP SPECT scan does not require stopping lactation.
The radiation exposure of accompanying personnel during nuclear medicine examinations is lower than that of the examinee, so the radiation dose for accompanying personnel is also safe.
Do patients undergoing nuclear medicine examinations need to be isolated after returning home or to the ward?
No, isolation is not necessary. However, considering the residual radionuclides in the patient's body, it is recommended that patients minimize contact with others and minimize the duration of contact. Hugging is particularly recommended for infants, young children, and pregnant women. There are no contraindications for adults.
Professional Analysis: Commonly used radionuclides that enter the patient's body have a short half-life. Take 99mTc, for instance, which is the workhorse radionuclide for SPECT imaging. It has a physical half-life of 6.02 hours, but when you factor in the body’s drug metabolism and clearance, the effective half-life drops to about 2 to 3 hours. The upshot is that the radioactivity in the patient’s body reaches background levels typically within a 24-hour window. Now, consider the fluorine-18 isotope frequently employed in PET/CT studies. Its half-life is a brisk 109.8 minutes, leading to an even speedier clearance. In PET/CT cases, background levels are restored within 7 to 8 hours after administration.
Does nuclear medicine affect health?
The human body is inherently radioactive and contains trace amounts of radioactive substances, such as potassium, cesium, and radium. Instrumental measurements show that an adult human body emits 24,000 gamma rays per minute—a very small amount of radiation. We live daily in an environment exposed to cosmic rays, various radiation sources in soil and building materials, and electromagnetic radiation from computers and cell phones. Fruits, vegetables, and drinking water contain radionuclides. For example, eating a banana exposes you to approximately 0.1 μSV of radiation. At 30,000 feet, the radiation intensity is approximately 2 μSV/h, meaning that in a 10-hour flight, you'll receive approximately 20 μSV of radiation. Cigarettes contain radioactive polonium and lead, and each smoker's lungs receive approximately 160 millisieverts of radiation per year. Therefore, the safe dose of radiopharmaceuticals taken during nuclear medicine examinations will not affect human health or cause cancer.
With the development of modern medical technology, nuclear medicine examinations are increasingly used in the early diagnosis, staging, prognosis, and efficacy observation of diseases. Nuclear medicine examinations are safe and reliable. Both patients and medical staff should look at the so-called "nuclear radiation" issue scientifically and rationally, eliminate unnecessary fear of nuclear medicine examinations, and thus improve the level of diagnosis and treatment of diseases.