PET-CT is a commonly used examination item in oncology, when patients get a thick stack of PET-CT paper reports, they often see such words "SUWmax", "increased FDG metabolism", "calcification", "low-density mass", etc., but they don't know what they mean, so let's learn about them one by one today.
One
How to read the PET-CT report?[1-3]
A complete PET-CT report generally includes the basic information of the examinee, clinical history, examination purpose, examination technology and operation process, imaging observations, imaging diagnosis, etc. Among them, doctors mainly look at what is seen on imaging and imaging diagnosis.
If you want to understand the PET-CT report, you can't fail to mention the most important data, SUV value, so what is SUV and what is its significance?
- 1. What is the SUV value in PET-CT?
SUV is an abbreviation for "standard intake value", which reflects the degree of ingestion of imaging agents in the lesion area. Glucose metabolism in malignant tissue is vigorous, and after injection of imaging agent 18F-FDG (fluorodeoxyglucose), it will take in more glucose than normal tissue, and the SUV value will be higher.
SUV values are widely used to distinguish benign and malignant tumors and indicate the degree of malignancy of tumors. Generally speaking, the higher the degree of tumor malignancy, the higher the SUV value, but the higher the SUV value, because the SUV value of the inflammatory lesion may also be greater than 2.5.
- 2. The normal range of SUV values
SUV2.5 is generally used as the distinguishing boundary for benign and malignant tumors:
- SUV＞2.5考虑为恶性肿瘤；
- SUVs are in the critical range between 2.0-2.5;
- SUV<2.0 can be considered benign lesions.
However, it is not that the SUV value is higher than a certain value is necessarily malignant, and below a certain value is necessarily benign, because there are multiple factors that may affect the SUV value.
- 3. What are the factors that affect the value of an SUV?
There are many factors that affect the value of SUV, including blood glucose and hormone levels, individual differences in subjects, the size of the lesion, the pathological type of the tumor, inflammation, abscess, imaging time after injection, device performance, operation method, etc. Therefore, in addition to the SUV value, it is also necessary to comprehensively analyze the CT manifestation, density, surrounding relationship and distribution of 18F-FDG in the lesion.
In addition to the SUV value, there are many technical terms in the PET-CT report, and the following four are representative:
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Two
4 terms to keep in mind!
- 1. Increased FDG metabolism
FDG is the abbreviation of fluorine-18-labeled deoxyglucose, and if the result shows that FDG is "metabolically elevated", it indicates that the local metabolism is relatively vigorous, suggesting that there may be a cancer. Be aware that some of the body's inflammatory responses may also cause increased metabolism
- 2. Calcifications
Calcification is generally formed by the deposition of calcium salts after the body tissue is damaged.
There are many reasons for this, such as calcifications in the lungs, which may indicate that there may have been tuberculosis in the past, or it may be a state after the inflammation has recovered. In general, there is no need to worry too much.
- 3. Irregular hypodense shadow/dense mass
The density of the human body's tissue structure can be summarized into three categories:
High density: bone tissue and calcifications;
Medium density: cartilage, essential organs, fluids in the body, muscles, nerves, connective tissues, etc.;
Low density: adipose tissue and gases present in the respiratory tract, sinuses, gastrointestinal tract, mastoid process, etc.
If a high-density shadow is present in a place that should be low-density, it indicates that there is a lesion in the area.
- 4. Ground-glass nodular opacity (GGO)
The shadow of an invasive lesion in the lungs, also called ground-glass nodules in the lungs, is uniform in density and resembles ground-glass in shape. is a typical feature of lung tumors and may be benign or malignant.
Three
How long does it take for the radiation from PET-CT to drain away?[4]
The radiation of PET-CT can be divided into two parts, the radiation of the imaging agent used to examine (18F-FDG) and the radiation of CT examination. After PET-CT scanning, a small amount of radioactive material remains in the patient's body, but the dose is small and has a short half-life of only 2 hours.
After the examination, the patient can drink more water to promote metabolism, and the radiation in the body can be discharged in about 1 day in a normal person. Patients are advised to avoid close contact with infants, the elderly, and pregnant women for a day after the examination.
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Bibliography:
[1] Wang Qian, Li Nan, Huo Li, et al.Nuclear Medicine~(18)F-FDG PET/CT Report Writing Specification[J].Chinese Journal of Medical Imaging,2021,29(01):1-3.
[2] Huang Xiaowei.Speaking of "making films", who performs better[J].Family Life Guide,2023,39(09):69-70.
[3] Wang Xinhua, Yang Yanxin, Wang Yujun, et al.Multi-omics multi-dimensional detection for monitoring the efficacy of lymphoma patients[J].Chinese Journal of Experimental Hematology,2023,31(03):746-752.
[4] Xu Mingming. Health Guide,2022,28(04):50-51.)
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Tips: This article is only a popular science article, does not provide professional diagnosis and treatment opinions, specific diagnosis and treatment, please under the guidance of professional doctors. Points, shares, points, favorites