ABSTRACT
The structure and main features of a HF EM installation based upon a new approach for creating electromagnetic fields destined for whole body (WBH) and deep local (DLH) hyperthermia are discussed. The HF EM field, at a frequency of 13.56 MHz, is created by a coplanar capacity type applicator positioned under a distilled water filled bolus that the patient is lying on. The EM energy being released directly in the deep tissues ensures effective whole body heating to required therapeutic temperatures of up to 43.5 degrees C, whereas the skin temperature can be maintained as low as 39-40.5 degrees C. For DLH, the installation is equipped with additional applicators and a generator operating at a frequency of 40.68 MHz. High efficiency of the WBH applicator makes it possible to carry out the WBH procedure without any air-conditioning cabin. Due to this, a free access to the patient's body during the WBH treatment is provided and a simultaneous WBH/DLH or WBH/LH procedure by means of additional applicators is possible. Controllable power output in the range of 100-800 W at a frequency of 13.56 MHz and 50-350 W at a frequency of 40.68 MHz allows accurate temperature control during WBH, DLH and WBH/DLH procedures. SAR patterns created by the WBH and DLH applicators in a liquid muscle phantom and measured by means of a non-perturbing E-dipole are investigated. The scattered EM field strength measured in the vicinity of the operating installation during the WBH, DLH and WBH/DLH procedures does not exceed security standards. Examples of temperature versus time graphs in the course of WBH, DLH and WBH/DLH procedures in clinics are presented. The installation is successfully used in leading oncological institutions of Russia and Belarus, though combined WBH/DLH procedures are evidently more complicated and demand thorough planning and temperature measurements to avoid overheating.
Subject(s)
Electromagnetic Phenomena/instrumentation , Electromagnetic Phenomena/methods , Hyperthermia, Induced/instrumentation , Hyperthermia, Induced/methods , Humans , Neoplasms/therapy , Phantoms, Imaging , Temperature , ThermometersABSTRACT
A homogeneity coefficient (HC) is suggested allowing quantitative evaluation of SAR distribution homogeneity over the heated area. Its efficacy in appreciation of SAR patterns quality is demonstrated on idealized and real SAR distributions. The HC parameter of a series of applicators widely used in clinics are calculated. HC could be assumed as a useful parameter additional to the qualified effective field size (EFS) in characterizing the applicator's properties.
Subject(s)
Fever , Humans , Microwaves , Models, TheoreticalABSTRACT
LTH on Yakhta-4M unit was used in benign prostatic hyperplasia (BPH). The prostate was heated transrectally by directional radiation. The course of treatment comprised 5 sessions for 60 min twice a week. The efficacy of the treatment was assessed 3 years later in 78 patients which were divided into 4 groups: 31 patients with BPH, 30 patients with BPH in combination with chronic prostatitis, 9 patients with acute urine retention and 8 patients with cystostomy fistula. 5 patients underwent surgery. LTH is safe in relation to side effects, may be used both at early stage of the disease and in risk of operative intervention.
