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.


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 degrees C before heating and 54.8 degrees 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.


CONCLUSIONS
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.
Park
Byeong Ho
BH
Department of Diagnostic Radiology, Institute of Medical Science, Dong-A University College of Medicine, Busan, Korea. bhpark@daunet.donga.ac.kr
Koo
Bong Sig
BS
Kim
Young Kon
YK
Kim
Moon Kon
MK
D000818:Animals; D001831:Body Temperature; D006979:Hyperthermia, Induced / Q000295:instrumentation*; D008099:Liver / Q000473:pathology / Q000502:physiology*; D009336:Necrosis; D011817:Rabbits; D013193:Stainless Steel
D013193:Stainless Steel