What is 125I seed implantation? 

125I Seed Implantation (also called Particle knife) is applied to a variety of primary and metastatic tumors nowadays. 125I seeds are some small iodine radioactive particles that can give off short-range γ-ray to kill tumor cells continuously. 125I seed implantation can achieve the same internal radiation effects as surgery does. Hence, it is also called particle knife. These iodine particles are 0.8 mm in thickness, about 0.4 cm in length.

What are the advantages of 125I seed implantation?

• The ray of these small seeds only effects inside the tumor where they are implanted, so it will not cause much damage to the normal surrounding tissues;
• Effectively kill the tumor by continuously and effectively exposure up to 180 days;
• Relieve pain, increase survival rate and the quality of patient’s life.
• The implanting position, amount of implanting seeds and the implanting way are determined by the exactly designed treatment plan which is made based on each patient’s individual condition.

How radioactive seeds are implanted?

Firstly, the tumor size, which comes from CT and MRI results, is input into a three-dimensional treatment planning system (TPS) to construct a dimensional image. Then the numbers of implanting seeds, the location of each seed will be come out depends on the location, shape and size of the tumor.

Under CT or ultrasound guidance, I 125 seeds will be directly placed into the tumor by a special set of equipment. Or they will be placed into the residual cancer bed and the possible paths of metastatic lymph nodes. These implanted particles will keep emitting γ-ray within the tumor, targeting to the cancer cells accurately, just as "land mines" do.

What happens after the procedure?

Iodine-125 seed implantation has few complications. After the procedure, most patients feel nothing pain or severe discomforts. Only few may have certain extent of uncomfortable feeling, which is caused by ray releases. Make prostate cancer patients as an example, after seeds implantation, they may present with irritation signs of bladder or rectum (sensations like mild bearing down) or distension over lower abdomen. While for lung cancer patients, it may cause a slight cough, and sometimes accompanied by slight blood streak. The most common side effects happened after seeds implantation to superficial tumor patients are skin ulcer, skin darkening. But generally speaking, the side effects are mild, not enough to cause serious damage or dysfunction of organs.

How many seeds are suitable for the implantation?

The amount of implanted seeds depends on the size, shape, location of the tumor or lesion. To bigger tumors, therapeutic effect can be achieved with more seeds. The smaller the tumor is, the fewer seeds will be implanted, and the better effect it will achieved. In some cases, tumors would disappear with only one procedure.

How to confirm the therapeutic efficacy of radioactive seeds?

Soon after the radioactive seeds have been implanted into the tumor site, they will release sustained rays to attack and kill the cancer cells. Once the energy of rays has accumulated to a certain extent, cancer cell will die gradually. Therefore, applying radioactive seeds to kill cancer cell will be a sustained and slowly process. Generally speaking, at the 2nd or 3rd month after seeds implantation, cancer cell necrosis will become obviously. If the tumor is on the surface of body, we can even observe it becoming smaller and smaller gradually with naked eyes; if the tumor is inside the body, we may observe its shrinking or death with the help of CT scans or B-Ultrasound examinations.

Announcements after treatment:

Test results of COSTIND (The Commission for Science, Technology and Industry for National Defense) show that the radiative damage of I125 seed implantation to normal adult is very much lower from the national radiological protection standards. Radiation range of I125 is rather limited with small affect on normal tissues around tumor. So there is no need for doctors or patients to worry about the possible damages. But among the first two months after receiving I125 seed implantation, patients had better avoid very close contact with pregnant women and children below 3 years old (keep a distance from them for more than 1m will be better). Two months later, after the radiation gradually weakened, patients can return to normal life.

Particle Knife is suit to treat what kind of tumors?