The Induction of Hyperthermia in Rabbit Liver by means of Duplex Stainless Steel Thermoseeds

OBJECTIVE: To determine the heating characteristics of needle-shaped duplex stainless steel thermoseeds, and to evaluate their effectiveness in the induction of hyperthermia in rabbit liver. MATERIALS AND METHODS: Thermoseeds of the two different shapes, L-shaped for single doses of hyperthermia and I-shaped for in-vitro study and repeated hyperthermic induction, were prepared. For the in-vitro study, an I-shaped thermoseed 0.23 mm in diameter and 25 mm long was placed inside a plastic tube filled with water. Heat was applied for 30 minutes within an induction magnetic field, and during this time changes in temperature were recorded using three thermocouples. For the in-vivo study, fifteen New Zealand white rabbits were divided into five equal groups. An I-shaped or L-shaped thermoseed was inserted in each rabbit's liver, and then placed within the center of the magnetic induction coil during a 30-minute period of hyperthermia. The rabbits in the first group were sacrificed immediately after hyperthermia was induced once, while those in the other groups were sacrificed at 1, 3, and 7 days, respectively, also after one induction. The remaining three rabbits were sacrificed 4 days after three consecutive daily treatment sessions. The resected segments of liver were subsequently evaluated histopathologically for the extent of coagulation necrosis caused by heating of the thermoseed. RESULTS: The in-vitro study demonstrated that the temperature in the thermoseed, which was 25.9 degree C before heating and 54.8 degree C after heating, rose rapidly at first but progressively less rapidly as time elapsed. Light microscopic examination of the rabbits' livers revealed coagulation necrosis and infiltration by inflammatory cells around the insertion site of the thermoseed. The maximum diameter of coagulation necrosis was 2.81+/-1.68 mm, and this occurred in the rabbits that were sacrificed 7 days after heat induction. CONCLUSION: Needle-shaped duplex stainless steel thermoseeds show temperature-dependent-type heating characteristics, and in rabbit liver, induced coagulation necrosis of surrounding tissues after heat is applied for 30 minutes. These thermoseeds may thus be useful for the induction of interstitial hyperthermia.

Effect of Ni-Cu Thermoseeds on L-929 Cells and Muscle Tissues in Rabbits / 中国微创外科杂志

Objective To study the in vitro heating ability of Ni-Cu thermoseeds and their effect on the rabbit liver cells and tissues. Methods The temperature of rabbit liver tissues were monitored under an alternating magnetic field.MTT assay was used to evaluate the in vitro cytotoxicity of the extra-liquid of the Ni-Cu thermoseeds;Hemolytic test was carried out to estimate its blood toxicity;and muscular implantation test was employed to determine the levels of its tissue toxicity.Results The thermoseeds used in this experiment showed a high heating ability in alternating magnetic field in vitro.MTT assay showed that the toxicity of the material on mouse fibroblast(L-929) cell lines was 1 degree,which means non-cytotoxic.Hemolytic test revealed a hemolysis rate(HR) of 3.25%(less than 5%),showing that the thermoseeds had no hemolytic reaction.Muscular implantation test showed different levels of inflammatory reaction in the muscle tissues.Conclusion Thermoseeds induced heating in alternating magnetic field can achieve an appropriate temperature,and the gilded thermoseeds have a high biocompatibility with 1 degree cytotoxicity without leading to hemolytic reaction.

Thermoseed Inductive Heating in vivo and in vitro and Its Impact on Immune Function of Tumor Bearing Rats / 中国微创外科杂志

Objective To evaluate the heating ability of thermoseeds in alternating magnetic field and its therapeutic effects on tumor bearing rats with simultaneously detected immune function. Methods To monitor the temperature increase of thermoseeds in vitro,of which the Curie point was 57 ℃ or 70 ℃.Forty Wistar rats implanted with Walker-256 cells were randomly divided into five groups: C group(control group,10 rats),M group(magnetic control group,5 rats),T group(thermoseeds control group,5 rats) and two heating treatment groups(H1 group,10 rats and H2 group,10 rats).In the H1 group,two thermoseeds with a Curie point at 57 ℃ were implanted into the tumor tissues in each rat with a heating time of 30 minutes,while in the H2 group,two thermoseeds with a Curie point at 70 ℃ were used with a heating time of 6 minutes.Five rats from each group were killed 9 days after the heating therapy to evaluate the volume and weight of the tumor tissues.The peripheral blood T-cells were counted in the rest rats in the H1,H2,and C groups. Results Magnetic inductive heating of the thermoseeds in vitro can reach the Curie point.The median tumor volume in the H2 group was 0.50 cm3(0.00-26.54),which was significantly lower than that in the M group(36.18 cm3,0.96-39.90,Z=2.21,P=0.032).And the weight of the tumors in the H1 and H2 groups was significantly lower than that in the M group [0.96 g(0.00-21.18) in H1 and 0.41 g(0.00-23.40) in H2 vs 31.45 g(1.09-36.09) in M group,Z=2.21 and P=0.032 for both].In the peripheral blood,the percentage of CD4+ T-cells was(22.39?5.27)% in H1 group,and(24.76?5.19)% in H2 group,which were significantly higher than that in C group [(12.07?4.45)%,P=0.01 and 0.003 respectively];and the percentage of CD8+ T-cells in the H2 group was significantly higher than that in the C group [(19.58?4.63)% vs(12.72?3.96)%,P=0.04].Conclusions Thermoseed had a good heating ability in alternating magnetic field and its inductive heating can inhibit tumor growth in Wistar rats and improve the immune function of the rats.

Temperature distribution in VX-2 hepatoma heated with thermoseed hyperthermia / 대한치료방사선과학회지

It was the purpose of present study to develop a new thermoseed for heating deep-seated tumors and assessment of the effect of magnetic control on thermoseeds. Aqueous suspension of iron micro spheres (Ferropolysaccharide) was injected directly into the VX-2 hepatoma and heated with 1.2 MHz inductive radiofrequency unit. Aqueous thermoseed suspension was delivered to the tumor by simple percutaneous injection. The limitation of the thermoseed heating method is the positional change of thermoseed particles in the tumor after implantation. The thermoseed particles could enter the systemic blood circulation and cause a severe embolization of a critical organ. To minimize this limitation, we have used the magnetic control after loading the thermoseed in the tumor. When ferropolysaccharides were exposed to a strong magnetic field, they magnetized and subsequently exerted a magnetic force on each other, forming larger aggregates of particles. The size of aggregated particles were too big to enter the systemic blood circulation. Thus, unlike other thermoseed method, we hold the thermoseed particles stationary in the tumor. The temperature of the injected site and immediate vicinity elevated by 4-5degree C. The temperature of the surrounding normal hepatic tissue elevated by 1-2degree C only. The heating effect within the tumor was variable depending on the density of ferromagnetic aqueous suspension. Our results suggest that inductive heating of tumor injected with ferropolysaccharide solution offers the possibility of effective heat delivery to the defined tumor volume, which is difficult to heat with other heating devices.