Intraspinal temperatures during regional deep hyperthermia induced by electromagnetic radiation in the Macaca mulatta

A capacitive ring system operating at 27 MHz was tested for temperature distribution in the abdominal cavity of the living Rhesus monkey. Catheters were introduced through the abdomen and their location checked after the experiment. During two of these experiments a catheter was also introduced into the intraspinal canal. Temperature distribution was rather homogeneous within the abdominal cavity. Core temperature remained 3-5 degrees C below intra-abdominal temperatures. The intraspinal temperature increase was of the same magnitude compared with intra-abdominal temperature increase. Similar findings in other species have been reported by others. It is concluded that during non-invasive induction of regional hyperthermia by electromagnetic radiation, where a high level of energy is directed close to the spine, the intraspinal temperatures may be increased as high as the temperatures within the surrounding tissues. The central nervous system may be relatively sensitive to hyperthermia and hyperthermia may sensitize the spinal cord to radiation. Therefore, when hyperthermia is targeted at areas near the spine, either alone or in combination with radiotherapy applied to the tolerance limit of the spinal cord, these findings will have to be taken into consideration.