Interstitial Hyperthermia Research Articles

Lokoregionäre Hyperthermieverfahren in der Gynäkologie - Standortbestimmung und Perspektiven

Unter dem Begriff lokoregionäre Hyperthermieverfahren fasst man die lokale Hyperthermie (Erwärmung von oberflächlichen Tumoren, z. B. Brustwandrezidiv eines Mammakarzinoms), die regionale Hyperthermie (Behandlung größerer Körperregionen, z. B. pelvine Tumoren) und die interstitielle Hyperthermie (Einbringen von Sonden in den Tumor mit anschließender Erwärmung) zusammen. Gegenwärtige Einsatzmöglichkeiten der wissenschaftlich begründeten Hyperthermie bestehen in Deutschland lediglich im Rahmen kontrollierter Studien bzw. in Kooperation mit den Niederlanden. Durch prospektiv randomisierte Studien untermauerte Anwendungsbereiche betreffen vorbestrahlte Patientinnen mit Lokalrezidiven von Mammakarzinomen (in Kombination mit einer erneuten Radiatio) und Patientinnen mit Zervixkarzinomen (ebenfalls in Kombination mit einer Strahlentherapie und bei Rezidiven in Kombination mit einer Chemotherapie). Auch Patientinnen mit ausgedehnten Vaginalkarzinomen (Stadium II > 4 cm und Stadium III) profitieren möglicherweise ersten Ergebnissen zufolge von einer Kombination der Strahlentherapie mit einer Hyperthermie. Für eine abschließende Bewertung dieser Therapiemethode ist einerseits das Abwarten von Studienergebnissen erforderlich, insbesondere hinsichtlich des Vergleichs der hyperthermen Radiotherapie mit einer Radiochemotherapie bei Patientinnen mit Zervixkarzinom FIGO-Stadium I B - IV A und der magnetischen Flüssigkeitshyperthermie in Kombination mit einer interstitiellen Strahlentherapie bei Patientinnen mit inoperablen lokal begrenzten Residualtumoren. Andererseits bleibt abzuwarten, welche Fortschritte experimentelle Targeting-Verfahren im Hinblick auf ihre klinischen Einsatzmöglichkeiten erzielen.

Frontal Anaplastic Oligodendroglioma Showing Multi-organ Metastases After a Long Clinical Course-Case Report-

A 17-year-old woman presented with an anaplastic oligodendroglioma manifesting as generalized seizure. Neuroimaging studies revealed a right frontal tumor. Histological examinations of biopsy specimens revealed that the tumor was oligodendroglial in nature. Total resection was repeated four times, and malignant change was evident within the tissues. The final diagnosis was anaplastic oligodendroglioma. Despite irradiation, combination chemotherapy, and interstitial hyperthermia, the tumor grew rapidly but was confined to the cavity created by previous removal operations. She suffered bone pain in the last 3 months of her life, when neuroimaging examinations disclosed multiple bone lesions. She died at the age of 29 years. At autopsy, generalized metastases from the tumor were identified at various sites, including the dura mater covering the frontal lobes and thoracic cord, cavernous sinus, tuberculum sellae, spleen, liver, pancreas, lungs, paratracheal lymph nodes, vertebral bodies, ribs, sternum, pelvis, dorsal root ganglia, and iliopsoas muscle. This rare case of cerebral anaplastic oligodendroglioma developed in adolescence, and rapid hematogenous spread of the glioma cells into the systemic organs occurred after a relatively long clinical course.

Interstitial Hyperthermia With Intra-arterial Injection of Adriamycin for Malignant Glioma

A new method for treating malignant glioma by concurrent intra-arterial injection of adriamycin during thermotherapy was performed in seven patients with malignant glioma, four males and three females, with five cases of glioblastoma and two of anaplastic oligodendroglioma. Adriamycin was intra-arterially injected at a dose of 20 mg via the common carotid artery during thermotherapy. The heating procedure was repeated three times combined with chemotherapy in one therapy course, and a total of nine therapy courses were performed in the seven patients. All patients tolerated the protocol well. Based on post-therapy computed tomography, five of the therapy courses achieved partial response, one course resulted in disease progression, and the remaining three courses showed no change. The median time to progression was 3.4 months and the overall median length of survival following stereotactic biopsy was 13.2 months. Facial flushing was observed during eight therapy courses, and extensive alopecia in six therapy courses. Intracystic concentrations of adriamycin were determined in three patients, and marked increases were observed. Intra-arterial injection chemotherapy during hyperthermia is a promising therapeutic method for treatment of malignant glioma with few adverse effects.

Multiple-fibre low-power interstitial laser hyperthermia: studies in the normal liver.

Multiple four-fibre low-power interstitial laser hyperthermia was performed in the canine liver to establish the parameters with which large areas of thermal necrosis could be made. Using 1.5 W for 670 s (4020 J in total) and a fibre spacing of 1.5 cm, lesions with dimensions of 3.6 x 3.1 x 2.8 cm were achieved in 75 per cent of those attempted. There was no mortality and a low morbidity rate. These lesions could be visualized in both their development and resolution using ultrasonography. Healing occurred by 1 year. Temperatures in the centre of the heated region were 60 degrees C, which is more than enough to cause thermal cell death. There was good correlation between the temperatures recorded, the sonographic changes seen, and the pathological evidence of necrosis. Multiple-fibre low-power interstitial laser hyperthermia performed with ultrasonic guidance may be of use in the treatment of liver tumours.

The effect of thermotherapy using magnetic nanoparticles on rat malignant glioma

Thermotherapy using magnetic nanoparticles is a new technique for interstitial hyperthermia and thermoablation based on magnetic field-induced excitation of biocompatible superparamagnetic nanoparticles. To evaluate the potential of this technique for minimally invasive treatment, we carried out a systematic analysis of its effects on experimental glioblastoma multiforme in a rat tumor model. Tumors were induced by implantation of RG-2-cells into the brains of 120 male Fisher rats. Animals were randomly allocated to 10 groups of 12 rats each, including controls. Animals received two thermotherapy treatments following a single intratumoral injection of two different magnetic fluids (dextran- or aminosilane-coated iron-oxide nanoparticles). Treatment was carried out on days four and six after tumor induction using an alternating magnetic field applicator system operating at a frequency of 100 kHz and variable field strength of 0-18 kA/m. The effectiveness of treatment was determined by the survival time of the animals and histopathological examinations of the brain and the tumor.Thermotherapy with aminosilane-coated nanoparticles led up to 4.5-fold prolongation of survival over controls, while the dextran-coated particles did not indicate any advantage. Intratumoral deposition of the aminosilane-coated particles was found to be stable, allowing for serial thermotherapy treatments without repeated injection. Histological and immunohistochemical examinations after treatment revealed large necrotic areas close to particle deposits, a decreased proliferation rate and a reactive astrogliosis adjacent to the tumor.Thus, localized interstitial thermotherapy with magnetic nanoparticles has an antitumoral effect on malignant brain tumors. This method is suitable for clinical use and may be a novel strategy for treating malignant glioma, which cannot be treated successfully today. The optimal treatment schedules and potential combinations with other therapies need to be defined in further studies.

Prostate perfusion in patients with locally advanced prostate carcinoma treated with different hyperthermia techniques.

We determined prostate perfusion in 18 patients with locally advanced prostate carcinoma treated with a combination of external beam irradiation and regional (10) or interstitial (8) hyperthermia. Perfusion values were calculated from temperature elevations due to constant applied power and from transient temperature measurements after a change in applied power. Student's t test was used for comparing perfusion values with time and in the 2 groups. At the start of regional hyperthermia treatment mean estimated perfusion plus or minus standard deviation was 10 +/- 8 ml./100 gm. per minute. At the end of treatment mean perfusion was increased to 14 +/- 2 ml./100 gm. per minute (p <0.01). Achieved thermal parameters were a mean temperature of at least 40.3C +/- 0.6C in 90% of the prostate, 40.9C +/- 0.6C in 50% and a mean maximum temperature of 41.6C +/- 0.6C. At the end of interstitial hyperthermia treatment estimated mean perfusion was 47 +/- 5 ml./100 gm. per minute, which was significantly different compared with the end of regional hyperthermia (p < 0(-7) ). Mean temperature was at least 39.4C +/- 0.9C in 90% of the prostate and 41.8C +/- 1.6C in 50%, while mean maximum temperature was 53.1C +/- 6.3C. Systemic temperature increased during regional hyperthermia up to 38.6C, whereas during interstitial hyperthermia body temperature was not elevated. During interstitial hyperthermia perfusion values are higher than during regional hyperthermia. Hyperthermia causes increased prostate perfusion.

Clinical hyperthermia of prostate cancer using magnetic nanoparticles: Presentation of a new interstitial technique

The aim of this pilot study was to evaluate whether the technique of magnetic fluid hyperthermia can be used for minimally invasive treatment of prostate cancer. This paper presents the first clinical application of interstitial hyperthermia using magnetic nanoparticles in locally recurrent prostate cancer. Treatment planning was carried out using computerized tomography (CT) of the prostate. Based on the individual anatomy of the prostate and the estimated specific absorption rate (SAR) of magnetic fluids in prostatic tissue, the number and position of magnetic fluid depots required for sufficient heat deposition was calculated while rectum and urethra were spared. Nanoparticle suspensions were injected transperineally into the prostate under transrectal ultrasound and flouroscopy guidance. Treatments were delivered in the first magnetic field applicator for use in humans, using an alternating current magnetic field with a frequency of 100 kHz and variable field strength (0–18 kA m−1). Invasive thermometry of the prostate was carried out in the first and last of six weekly hyperthermia sessions of 60 min duration. CT-scans of the prostate were repeated following the first and last hyperthermia treatment to document magnetic nanoparticle distribution and the position of the thermometry probes in the prostate. Nanoparticles were retained in the prostate during the treatment interval of 6 weeks. Using appropriate software (AMIRA), a non-invasive estimation of temperature values in the prostate, based on intra-tumoural distribution of magnetic nanoparticles, can be performed and correlated with invasively measured intra-prostatic temperatures. Using a specially designed cooling device, treatment was well tolerated without anaesthesia. In the first patient treated, maximum and minimum intra-prostatic temperatures measured at a field strength of 4.0–5.0 kA m−1 were 48.5°C and 40.0°C during the 1st treatment and 42.5°C and 39.4°C during the 6th treatment, respectively. These first clinical experiences prompted us to initiate a phase I study to evaluate feasibility, toxicity and quality of life during hyperthermia using magnetic nanoparticles in patients with biopsy-proven local recurrence of prostate cancer following radiotherapy with curative intent. To the authors’ knowledge, this is the first report on clinical application of interstitial hyperthermia using magnetic nanoparticles in the treatment of human cancer.

1394 POSTER The impact of half-body irradiation on quality of life of patients with multiple bone metastases

Objective: The combination of hyperthermia and radiation in the treatment of malignancies is based on a variety of experimental data which have proven the synergistic effects of these two treatment modalities. We planned a phase II trial in a special hyperthermia research group (SFB 273) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) to determine feasibility, acute toxicity and efficacy of this combination for prostate cancer.Methods: A total of 57 patients with localized prostate cancer were treated with interstitial hyperthermia using cobalt-palladium thermoseeds and conformal radiation between July 1997 and December 2000. Thermoseeds were placed into the prostate homogeneously. Hyperthermia was created using a magnetic field and was delivered in six sessions once weekly. 3D-conformal radiotherapy of 68.4 Gy was given simultaneously in daily fractions of 1.8 Gy.Results: Intra-prostatic temperatures were between 42 and 46 °C. No major side effects were observed during hyperthermia. Median follow-up was 12 months (range: 3–26 months). Median prostate specific antigen (PSA) value decreased from 11.6 to 2.4 ng/ml 3 months after treatment, to 1.3 ng/ml 12 months after treatment and to 0.55 ng/ml 2 years after the therapy.Conclusion: Interstitial hyperthermia is feasible, well tolerated and led to a steep decrease of PSA values. Our current follow-up is too short to comment about efficacy. Combining effective interstitial hyperthermia with conformal radiotherapy may be an exciting innovative treatment option for prostate cancer.

1392 POSTER Tolerance and efficacy of high-dose 3D-Conformal Radiation Therapy (CRT) in cirrhotic patients with small hepatocellular carcinomas (HCC) not suitable for curative therapies

Objective: The combination of hyperthermia and radiation in the treatment of malignancies is based on a variety of experimental data which have proven the synergistic effects of these two treatment modalities. We planned a phase II trial in a special hyperthermia research group (SFB 273) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) to determine feasibility, acute toxicity and efficacy of this combination for prostate cancer.Methods: A total of 57 patients with localized prostate cancer were treated with interstitial hyperthermia using cobalt-palladium thermoseeds and conformal radiation between July 1997 and December 2000. Thermoseeds were placed into the prostate homogeneously. Hyperthermia was created using a magnetic field and was delivered in six sessions once weekly. 3D-conformal radiotherapy of 68.4 Gy was given simultaneously in daily fractions of 1.8 Gy.Results: Intra-prostatic temperatures were between 42 and 46 °C. No major side effects were observed during hyperthermia. Median follow-up was 12 months (range: 3–26 months). Median prostate specific antigen (PSA) value decreased from 11.6 to 2.4 ng/ml 3 months after treatment, to 1.3 ng/ml 12 months after treatment and to 0.55 ng/ml 2 years after the therapy.Conclusion: Interstitial hyperthermia is feasible, well tolerated and led to a steep decrease of PSA values. Our current follow-up is too short to comment about efficacy. Combining effective interstitial hyperthermia with conformal radiotherapy may be an exciting innovative treatment option for prostate cancer.

Magnetic fluid hyperthermia (MFH)reduces prostate cancer growth in the orthotopic Dunning R3327 rat model

Magnetic fluid hyperthermia (MFH) is a new technique for interstitial hyperthermia or thermoablation based on AC magnetic field-induced excitation of biocompatible superparamagnetic nanoparticles. Preliminary studies in the Dunning tumor model of prostate cancer have demonstrated the feasibility of MFH in vivo. To confirm these results and evaluate the potential of MFH as a minimally invasive treatment of prostate cancer we carried out a systematic analysis of the effects of MFH in the orthotopic Dunning R3327 tumor model of the rat. Orthotopic tumors were induced by implantation of MatLyLu-cells into the prostates of 48 male Copenhagen rats. Animals were randomly allocated to 4 groups of 12 rats each, including controls. Treatment animals received two MFH treatments following a single intratumoral injection of a magnetic fluid. Treatments were carried out on days 10 and 12 after tumor induction using an AC magnetic field applicator system operating at a frequency of 100 kHz and a variable field strength (0--18 kA/m). On day 20, animals were sacrificed and tumor weights in the treatment and control groups were compared. In addition, tumor growth curves were generated and histological examinations and iron measurements in selected organs were carried out. Maximum intratumoral temperatures of over 70 degrees C could be obtained with MFH at an AC magnetic field strength of 18 kA/m. At a constant field strength of 12.6 kA/m, mean maximal and minimal intratumoral temperatures recorded were 54.8 degrees C (centrally) and 41.2 degrees C (peripherally). MFH led to an inhibition of tumor growth of 44%-51% over controls. Mean iron content in the prostates of treated and untreated (injection of magnetic fluids but no AC magnetic field exposure) animals was 82.5%, whereas only 5.3% of the injected dose was found in the liver, 1.0% in the lung, and 0.5% in the spleen. MFH led to a significant growth inhibition in this orthotopic model of the aggressive MatLyLu tumor variant. Intratumoral deposition of magnetic fluids was found to be stable, allowing for serial MFH treatments without repeated injection. The optimal treatment schedules and temperatures for MFH need to be defined in further studies.

Improved input impedance of a coaxial-slot antenna for interstitial heating by loading a matching circuit

Recently, research on medical applications of the thermal effects of microwaves, such as microwave treatment, on biological bodies has been carried out extensively. One example is hyperthermic treatment of cancer. In particular, in the treatment of cancer deep inside the human body, interstitial hyperthermia is effective. The most important characteristic of the antenna for interstitial hyperthermia is its heating properties. However, when clinical use is considered, impedance matching also must receive attention. In the present paper, with a view to impedance matching of the interstitial hyperthermia antenna, a coaxial slot antenna with a matching circuit of simple configuration is proposed. The reflection coefficient (S11) of the antenna is used as an evaluation guideline, and numerical simulation by the FDTD method and measurement are carried out. From these examinations, it is confirmed that the reflection characteristics can be improved drastically. It is further confirmed that the proposed antenna can supply a power of at least a certain level regardless of the electrical parameters of the biological tissue to be heated and of the antenna insertion length. Hence, this antenna is demonstrated to be practical. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(12): 11–19, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20218

500 kHz hyperthermia assisted HDR brachytherapy in the treatment of recurrent cervical and endometrial cancer in previously irradiated fields

Summary Background The biological effectiveness of elevated temperature (hyperthermia) on cancer cells is a well documented issue. Nevertheless, it is still not widely used in clinical practice, mainly due to technical difficulties. The main limiting factor is the protection of healthy tissue during the hyperthermia procedure. Hyperthermia, used as an adjuvant treatment with brachytherapy, provides the possibility of lowering total radiation doses, without reducing biological effects. Aim The aim of this work was to present the advantages of using 500 kHz hyperthermia in HDR brachytherapy of cervical & endometrial cancer. Materials/Methods Hyperthermia procedures were performed in 8 endometrial cancer patients and 2 cervical cancer patients with early recurrent local disease in previously irradiated areas. One or two interstitial hyperthermia procedures were performed using rigid metal needles, both for brachytherapy and temperature elevation. The total radiation dose was 30 Gy, delivered in 3 or 6 Gy per fraction. In the case of 3 Gy per fraction, a scheme of two fractions per day, separated by at least 8 hours, was used. The total treatment time ranged from 5 to 14 days. Hyperthermia was performed concurrently with brachytherapy. Results During the treatment, no acute reactions were observed. In each case, tumour regression over 50% was noted. During the 3 to 14 month follow-up period, complete vaginal tumour regression was seen in 8 of 10 cases. Conclusions 500 kHz hyperthermia assisted interstitial brachytherapy can be regarded as effective and safe procedure, especially when applied as secondary (salvage) treatment. More cases and longer observation time are needed to make definite conclusions.

Is interstitial hyperthermia a safe and efficacious adjunct to radiotherapy for localized prostate cancer?

Is interstitial hyperthermia a safe and efficacious adjunct to radiotherapy for localized prostate cancer?

A feasibility study of interstitial hyperthermia plus external beam radiotherapy in glioblastoma multiforme using the multi electrode current source (MECS) system

Purpose: Thermoradiotherapy has been shown in several randomized trials to increase local control compared to radiotherapy alone. The first randomized study of interstitial hyperthermia in glioblastoma multiforme showed a survival benefit for hyperthermia, though small. Improvement of the heating technique could lead to improved results. The purpose of this feasibility study is to present the clinical and thermal data of application of an improved interstitial hyperthermia system.Methods and materials: Six patients with a glioblastoma multiforme were treated with interstitial hyperthermia using the Multi Electrode Current Source Interstitial Hyperthermia (MECS-IHT) system. The MECS-IHT system has the capability of spatial monitoring of temperature and individually steering of heating electrodes. Three sessions were given aiming at a steady state temperature of 42°C for 1 h, with an interval of 3–4 days, during an external irradiation scheme of 60 Gy in 6 weeks. Hyperthermia was delivered with a mean of 10 catheters, 18 heating electrodes and 38 thermal probes per patient.Results: Sub-optimal temperatures were encountered in the first two patients leading to adjustments in technique thereafter with subsequent improvement of thermal data. With a catheter spacing of 11–12 mm, measurements yielded a mean T90, T50 and T10 of 39.9, 43.7 and 45.2°C, respectively, over three sessions in the last patient. The power per electrode to reach this temperature distribution varied from 25–100% of full power in each of the last four patients. Thermal data were reproducible over the three sessions. Acute toxicity was minimal.Conclusions: Despite the spatial steering capabilities of the MECS-IHT system, a large temperature heterogeneity was encountered. The heterogeneity was the reason to limit the catheter spacing to 11–12 mm, thus making only small tumour volumes feasible for interstitial heating.

Infrared thermographic SAR measurements of interstitial hyperthermia applicators: errors due to thermal conduction and convection

Thermal conduction and convection were examined as sources of error in thermographically measured SAR patterns of an interstitial microwave hyperthermia applicator. Measurements were performed in a layered block of muscle-equivalent phantom material using an infrared thermographic technique with varying heating duration. There was a 52.7% reduction in maximum SAR and 75.5% increase in 50% iso-SAR contour area for a 60-s heating duration relative to a 10-s heating duration. A finite element model of heat transfer in an homogeneous medium was used to model conductive and convective heat transfer during the thermographic measurement. Thermal conduction artefacts were found to significantly distort thermographically measured SAR patterns. Convective cooling, which occurs when phantom layers are exposed for thermal image acquisition, was found to significantly affect the magnitude, but not the spatial distribution, of thermographically measured SAR patterns. Results from this investigation suggest that the thermal diffusion artefacts can be minimized if the duration of the applied power pulse is restricted to 10 s or less.

Development of multi-channel radiofrequency (RF) interstitial hyperthermia system compatible with high-dose rate iridium-192 brachytherapy

9694 Background: We have developed a multi-channel RF interstitial hyperthermia system compatible with the high-dose rate Iridium-192 remote after loading system (Ir-192 RALS). The purpose of this presentation is to evaluate the heating characteristics of the system. Methods: The system is composed of eight channel RF signal generators, which can be controlled individually. Each RF generator consists of two types of electrodes: 1) an internal electrode made of stainless steel, which is originally an Ir-192 RALS applicator; and 2) a shared rectangular external electrode made of copper plate. For the computer simulation, we used simulation software (e-m CAD system, MAFIA ver. 3.20, CST, Germany) to calculate RF field distribution, magnetic field distribution and the specific absorption rate (SAR) distribution, in an arrangement using 4 needles inserted in a square-like formation, 2cm in distance from one another. For the experiments using the agar phantom, we generated a 5W 13.56 MHz RF signal for 5 minutes for 4 electrodes in the same square fashion. Results: The results from the computer simulation showed that SAR distribution outside each electrode was elevated, but the area inside the 4 electrodes did not show temperature elevation. The results from the experiments using the agar phantom showed a temperature increase in the center of the area surrounded by the 4 electrodes. Conclusions: Using an independently controlled RF signal, the results from the experiments with the agar phantom showed satisfactory temperature rise. The RF interstitial system we developed can provide greater heating volume compared to using a single internal electrode or multiple electrodes with a single generator. In addition, our system is compatible with the Ir-192 RALS, allowing for less-invasive interstitial hyperthermoradiotherapy by eliminating the trauma of needle re-insertion. No significant financial relationships to disclose.

Development of multi-channel radiofrequency (RF) interstitial hyperthermia system compatible with high-dose rate iridium-192 brachytherapy

9694 Background: We have developed a multi-channel RF interstitial hyperthermia system compatible with the high-dose rate Iridium-192 remote after loading system (Ir-192 RALS). The purpose of this presentation is to evaluate the heating characteristics of the system. Methods: The system is composed of eight channel RF signal generators, which can be controlled individually. Each RF generator consists of two types of electrodes: 1) an internal electrode made of stainless steel, which is originally an Ir-192 RALS applicator; and 2) a shared rectangular external electrode made of copper plate. For the computer simulation, we used simulation software (e-m CAD system, MAFIA ver. 3.20, CST, Germany) to calculate RF field distribution, magnetic field distribution and the specific absorption rate (SAR) distribution, in an arrangement using 4 needles inserted in a square-like formation, 2cm in distance from one another. For the experiments using the agar phantom, we generated a 5W 13.56 MHz RF signal for 5 minutes for 4 electrodes in the same square fashion. Results: The results from the computer simulation showed that SAR distribution outside each electrode was elevated, but the area inside the 4 electrodes did not show temperature elevation. The results from the experiments using the agar phantom showed a temperature increase in the center of the area surrounded by the 4 electrodes. Conclusions: Using an independently controlled RF signal, the results from the experiments with the agar phantom showed satisfactory temperature rise. The RF interstitial system we developed can provide greater heating volume compared to using a single internal electrode or multiple electrodes with a single generator. In addition, our system is compatible with the Ir-192 RALS, allowing for less-invasive interstitial hyperthermoradiotherapy by eliminating the trauma of needle re-insertion. No significant financial relationships to disclose.

Studies on microwaves in medicine and biology: from snails to humans.

This d'Arsonval Medal acceptance presentation highlights several research themes selected from Dr. Lin's published works, focusing on the microwave portion of the nonionizing electromagnetic spectrum. The topics discussed include investigation of microwave effects on the spontaneous action potentials and membrane resistance of isolated snail neurons, effects on the permeability of blood brain barriers in rats, the phenomenon and interaction mechanism for the microwave auditory effect (the hearing of microwave pulses by animals and humans), the development of miniature catheter antennas for microwave interstitial hyperthermia treatment of cancer, the application of transcatheter microwave ablation for treatment of cardiac arrhythmias, and the use of noninvasive wireless technology for sensing of human vital signs and blood pressure pulse waves. The paper concludes with some observations on research and other endeavors in the interdisciplinary field of bioelectromagnetics.

Safety and efficacy of concurrent interstitial radiation and hyperthermia in the treatment of progressive malignant brain tumors

High activity 125I brachytherapy has efficacy in selected recurrent malignant brain tumors, but limited efficacy and risk of radiation necrosis have prompted investigation of additional adjunctive therapies. This study aims to assess the toxicity of interstitial conductive hyperthermia used concurrently with 125I brachytherapy for the treatment of recurrent brain malignancies. Twelve patients with recurrent malignant brain tumors were implanted using afterloading catheters intended to deliver 50 Gy at the isodose line encompassing the enhancing tumor with a 5-mm margin and heated to 41.5 degrees C for 48 h. The average implant volume was 18 cc with 5.3 catheters containing 9.4 sources with a total activity of 265 mCi. Serious toxicities included 8 motor deficits, 2 mood alterations, 4 seizures and 2 catheter wound cerebrospinal fluid leaks. Median survival was 10.35 months with the best responses being 6 with stable disease and 2 with partial responses. Reoperation rate for radiation necrosis was 33%. Concurrent conductive thermoradiotherapy is feasible but is associated with serious toxicity. There is no suggestion of improved survival with thermoradiotherapy over brachytherapy alone. Given the degree of toxicity observed, alternative approaches to improving local control of these tumors are being explored.

Effect of the combination of laser excision and interstitial hyperthermia in palliative therapy of head and neck tumours in the advanced stage of the disease.

We evaluated the potential of combining laser excision with laser interstitial hyperthermia in order to improve the quality of life of patients with 3rd or 4th stage malignant head and neck tumours. To evaluate the quality of life, we used the 4th version of the University of Washington Quality of Life assessment score modified for head and neck tumours. The study group of 20 patients assessed their condition in a questionnaire, examining 12 aspects of their quality of life before the laser treatment, the second day after, and 6 weeks after the treatment. We observed a gain of 16.41 points, which subjectively represents a 70.32% improvement in the quality of life. Following this therapy the quality of life significantly improved in patients with primarily low quality of life, whereas the group of patients with less affected quality of life reported a temporary decline in the quality of life after the treatment. To obtain a proper objective indication, we suggest a mathematical modelling of possible gains for the individual patient using the University of Washington Quality of Life classification.