What should be paid attention to in MRI examination of liver cancer? You must know these diagnostic common senses for liver cancer

People at high risk of liver cancer need to have a physical examination every six months

Wang Zhiming reminded that long-term consumption of moldy, seaweed-contaminated, and aflatoxin- or nitrosamine-containing foods may cause liver cancer. Especially for chronic hepatitis B carriers, long-term heavy drinking can also bring liver cancer risks. Therefore, the majority of people at high risk of liver cancer, such as hepatitis and cirrhosis, need to undergo a physical examination every six months for early diagnosis, while liver cancer patients can improve the cure rate and prolong survival through the multidisciplinary collaborative diagnosis and treatment model (MDT) of "individualized treatment" and "comprehensive treatment".

According to statistics, about 500,000 people die of liver cancer every year in the world, and 50% to 55% of them are in my country. It ranks second in cancer mortality among urban populations and third in rural areas. Globally, the 5-year survival rate of liver cancer is only 36%, and the recurrence rate is also very high, with about 50% to 60% of patients recurring within one to two years after surgery.

Liver cancer is closely related to hepatitis and cirrhosis. The three are in a "progressive relationship". my country is a high-incidence area of ​​hepatitis B in the world. After patients are infected with the hepatitis B virus through blood, mother-to-child transmission and sexual transmission, liver cells begin to degenerate and necrotize, and then the liver proliferates to form nodules, which is commonly known as cirrhosis. In this way, some cells will become cancerous. Wang Zhiming said that the probability of liver cancer in patients with hepatitis and cirrhosis is ten times that of ordinary people.

"Patients with liver cancer usually do not have any clinical symptoms in the early stage, and the early detection rate is less than 15%." Wang Zhiming said that since liver cancer tumors grow very fast, once patients experience perceptible clinical symptoms such as abdominal pain, fatigue, weight loss, shoulder pain, jaundice, ascites, etc., they are often in the middle and late stages. Therefore, people at high risk of liver cancer, including those with hepatitis B, hepatitis C and cirrhosis, must insist on undergoing liver color Doppler ultrasound and alpha-fetoprotein (AFp) testing every six months. If the lesion is discovered early, the treatment effect and long-term survival rate can be significantly improved, and there are many more treatment options.

What should be paid attention to in MRI examination of liver cancer

On T1-weighted images, primary liver cancer can present as low signal, high signal, and isosignal. The water content and lipid content of liver cancer tissue are higher than those of normal liver tissue. Water has long T1 and long T2 relaxation time, while lipid has short T1 and longer T2 relaxation time. Increased water will prolong the T1 relaxation time of the tumor, while increased lipid will shorten the T1 relaxation time of the tumor.

The two factors restrict the change of T1 relaxation time of liver cancer, which can have at least three results: the water content of the tumor increases more, while the lipid content does not increase or increases only slightly, resulting in a longer T1 relaxation time for this part of liver cancer. Low signal appears on T1-weighted images in about 2/3 of the cases; the water content of the tumor does not increase much, but the lipid content increases significantly, resulting in the T1 relaxation time of this part of liver cancer being significantly shorter than that of normal tissue, and high signal appears on T1-weighted images in about 1/3 of the cases; the increase in tumor water content and lipid content are in a certain proportional relationship, resulting in a small extension of the T1 relaxation time of this part of liver cancer tissue or being very close to that of normal tissue. The latter generally shows equal signal on T1-weighted images, while the signal intensity of the former is related to the selected program.

If a T1-weighted program with a larger T1 weight is selected, these liver cancers will show low signal T2. Conversely, if a T1-weighted program with a smaller T1 weight is selected, these liver cancers may show equal signal. Using the spin echo short TR, short TE (T1-weighted) program, most liver cancers show uneven low signal, a few show high and low mixed signal areas, and the probability of the entire lesion showing equal signal and high signal is low. Among them, the lesion showing high and low mixed signals is a reliable sign of malignant lesions. These patchy high signal areas in the tumor represent necrotic bleeding in the pathology of liver cancer or significant lipid accumulation in the local part of the tumor. High-signal cancer nodules need to be distinguished from regenerative nodules of cirrhosis. The difference between the two is that regenerative nodules show low signal and cancer nodules show high signal on T, weighted images. The boundaries of the lesions are generally clear, especially at the capsule formation site, where the boundaries can be clearly displayed. When the tumor grows in an invasive manner or the peritumoral edema is more obvious, the boundaries are blurred.

On the spin-echo wavelength and multi-echo images, the vast majority of liver cancers show uneven high signal areas, and as the echo time increases, the signal intensity decays, the signal becomes more uneven, and the boundaries are blurred and irregular. The principle of this sign may be that liver cancer is composed of liver cancer cells of various morphologies in different combinations to form a diverse histological structure. Under the microscope, cancer cells can be seen arranged in cords or nests; some cancer nests have very rich sinusoids, while some cancer nests have very few sinusoids, and the cancer tissue is in a solid mass. The space-occupying signs of primary liver cancer (such as narrowing, occlusion, and displacement of the liver fissure and hilum, compression, deformation, and displacement of the inferior vena cava, and localized protrusion of the liver contour), hilar and retroperitoneal metastases, and cirrhosis that often accompanies patients with primary liver cancer can all be well displayed on MRI.