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PET-CT

What is a PET-CT?

A PET-CT is the most advanced diagnostic device that combines positron emission tomography (PET) and computed tomography (CT).
CT and MRI mainly detect the size and shape of Cancer cells (morphological diagnosis), and the nature of a disease can be determined by evaluating the amount of glucose consumed using a PET scan (function and metabolic diagnoses).

Cancer cells divide more frequently than normal cells and they require three to eight times as much glucose as normal cells. PET-CT is a method to obtain an image using the unique property of cancer cells to vigorously take up glucose.

Advantages of a PET scan

As the entire body is scanned at a time, cancer cells can be detected from all unexpected places. Therefore, the stage (evaluation of lesion size and metastasis) and recurrence can be quickly and accurately diagnosed. Moreover, the degree of malignancy (related to the speed of proliferation, metastasis, and recurrence) of cancer cells can be evaluated based on the degree of drug (18F-FDG) accumulation.
Furthermore, once the first intravenous injection of FDG is completed, there is little pain or burden on the patient until the examination is finished. During the scan, you need to stay still for about 12–20 min.

1.Scanning the entire body at a time

A PET scan can check the entire body at a time.

2.Less painful examination

You only have to rest for about an hour after being injected a drug and then lie down under the camera for about 30 min.

3.Useful for diagnosing cancer metastasis and recurrence

The entire body is scanned at a time and it is effective for detecting metastasis and recurrence (imaged area: the crown of the head to the thigh).

4.A PET scan shows how the tissues are functioning

A PET scan shows how the tissues are functioning and identifies if the tumor is benign or malignant based on the degree of drug accumulation.

Notes on PET-CT

Please note that there are some organs and parts of the body, wherein cancer cells are difficult to detect.
As the drug (18F-FDG) is excreted through the urine, it might be difficult to detect cancer cells in the kidneys and bladder.
At our hospital, you are requested to urinate before the examination, and we take an image of the abdomen twice with a certain time interval to prevent of scanning error.

Importance of multiple tests and the need for multipurpose diagnoses

PET scan is a revolutionary test method for cancer diagnosis. However, it is not complete because the location, spread, and severity of the disease become more apparent only when combined with other tests and diagnostic imaging methods.
In addition, it is necessary to understand that some organs and parts of the body contain cancer cells that cannot be detected with PET-CT alone.
Based on these characteristics of PET, we pay attention to the importance of combined examinations and the need for multipurpose diagnoses aimed to make a highly accurate diagnosis.

[False negative findings of PET] * False negative: Malignant tumor is detected as a normal or benign tumor.

Examples:

PET-CT scans almost the entire body at a time.
However, it is not complete, i.e., it must be combined with other diagnostic methods.
Cancer cells that form a mass are more visible, and those that spread thinly are less visible.
For example, if a tumor is about 5 mm that forms a mass, it may be visible. On the other hand, if it is 10 mm or more that spreads thinly, it is difficult to detect.

[False positive findings of PET] * False positive: Normal or benign tumor is detected as a malignant tumor.

Introduction of medical equipment