Is the radiation dose from PET/CT really that high?
2019-09-03
We often come across content related to PET-CT in mobile news feeds and WeChat Moments, which naturally sparks some questions in our minds:
“Can a PET-CT really screen for all diseases?”
“Is the radiation dose from PET-CT really high?”
“Is there a difference between CT and PET-CT?”
To address the above-mentioned concerns, we’ve compiled popular science materials from experts and scholars to help dispel any doubts and enable a more scientific and comprehensive understanding of PET-CT.
01. Principle
02. Scope of Application
A. Tumor Disease Indications
1. Clinical staging of tumors
2. Early diagnosis of tumors
3. To detect whether the tumor has recurred.
4. Monitoring the efficacy of tumor treatment and prognosis assessment
5. Differential diagnosis of residual lesions or post-treatment fibrosis and necrosis in tumor patients
6. Locate the primary tumor site.
7. Guide the radiotherapy plan and define the biological target volume for tumor radiation therapy.
8. Differential Diagnosis Between Benign Diseases and Malignant Tumors
9. Help determine the biopsy site for the tumor.
B. Indications for Heart Disease
Early diagnosis of coronary heart disease and assessment of viable myocardium after myocardial infarction.
C. Indications for the Central Nervous System
Diagnosis and assessment of the condition in senile dementia, detection of epileptic foci, and diagnosis and differential diagnosis of Parkinson’s disease.
03. Is the radiation level really extremely high?
In the field of radiomedicine, there is another important unit called the "gray" (Gy), often abbreviated as absorbed dose. It describes the amount of ionizing radiation energy absorbed per unit mass of a substance.
In PET/CT scans, the CT component primarily collects spatial information about organs and tissues and performs attenuation correction. Low-dose CT is used, with an radiation dose significantly lower than that of conventional CT scans. When the doses from both modalities are combined, the effective radiation dose received by the patient during a single PET/CT examination ranges from 8 to 10 mSv.
After reviewing the data set above and making a comparison, you’ll realize that a dose of 8 to 10 mSv not only falls within the normal range but is also perfectly safe.
The radioactive substance contained in 18F-FDG has a physical half-life of 108 minutes. Approximately 12 hours after 18F-FDG is injected into the body, its radioactivity will drop below background levels. If you drink plenty of water and urinate frequently after a PET/CT scan, you can significantly shorten the time the radiotracer remains in your body, allowing you to feel completely safe after about four hours. Until the radiotracer has been fully eliminated from your body, avoid prolonged contact with children and pregnant women.
04. The difference from CT
A.CT
The working procedure of CT is as follows: Based on the differences in how various human tissues absorb and transmit X-rays, highly sensitive instruments are used to measure the body. The data obtained from these measurements are then fed into a computer, which processes the data to produce cross-sectional or three-dimensional images of the examined part of the body, enabling the detection of even the smallest abnormalities anywhere within the body. CT scans are particularly effective for examining bones; moreover, CT is also well-suited for detecting intracranial hemorrhages.
B. Enhanced CT
Enhanced CT refers to a scanning procedure in which a water-soluble iodine contrast agent is administered intravenously prior to the scan, thereby increasing the density difference between the lesion tissue and the adjacent normal tissue and improving the visibility of the lesion. In contrast, conventional CT is a standard scan performed without any contrast enhancement or use of contrast agents. Conventional CT does not require injection of contrast agents, thus eliminating the risk of contrast-agent allergy. Compared to enhanced CT, conventional CT poses less harm to the human body.
C.PET/CT
PET, whose full name is Positron Emission Tomography, is a relatively advanced clinical imaging technique in the field of nuclear medicine. It is currently the only imaging technology capable of visualizing, in vivo, the metabolism of biomolecules, as well as the activity of receptors and neurotransmitters. Today, PET is widely used in the diagnosis and differential diagnosis of various diseases, assessment of disease severity, evaluation of treatment efficacy, research on organ function, and development of new drugs.
D.PET/CT
PET-CT is a perfect combination of PET and CT technologies, with each technology complementing the other. This combined PET-CT technique can significantly enhance the accuracy of clinical diagnosis—for example, when it comes to differentiating between benign and malignant lesions in small, solitary, isolated lesions within the body or to precisely locate such lesions prior to surgery. It offers advantages in both precise localization and accurate characterization that no other imaging modality can match.
After gaining a deeper understanding of PET-CT from this article, you should consult your doctor for more specialized questions. The PET-CT Center at Dalian Jinshitan Hospital has introduced NeuSight PET-CT, a flagship product from Dongsoft Medical Systems. This advanced imaging technology boasts advantages such as high sensitivity, accuracy, specificity, and precise localization. A single scan can provide an accurate overview of the body’s overall condition, enabling early detection of lesions and accurate diagnosis of diseases. It excels in screening and diagnosing high-risk factors for conditions including tumors, epilepsy, Alzheimer’s disease, and cardiovascular diseases, offering you a green and healthy medical experience.
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