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[en] This letter discusses a paper by van der Zee et al, who express surprise that the effect of the mean tumour temperature achieved could be discerned in the response rate, but that this did not hold for the equivalent time at a reference temperature of 430C. Dr Holt is not surprised, and offers at least two explanations for this phenomenon; firstly, the clinical material represents spontaneous cancer and, secondly, the hyperthermia was generated with electromagnetic radiation. Dr Van der Zee refutes these explanations. (U.K.)
[en] The interaction of an incoming electromagnetic (EM) wave with two or more EM waves inside a plasma can give rise to a fourth EM wave which is a phase conjugate reflection of the incoming wave. This occurs resonantly if ωa -ωb, the difference frequency of two of the EM waves, along with Ka - kb, the difference wave vector, conforms to one of the plasma dispersion relations, such as that for ion acoustic or Langmuir oscillations. In this case an internal eigenstate of the plasma is excited, and the phase conjugate wave is produced by scattering of the third wave by the density perturbation. (author)
[en] Oncological hyperthermia is a treatment to selectively kill cancer cells by directly applying heat to cancer cells or indirectly demage cancer cells. One of the most side effects of treatment is burn that can appear on the skin. In areas with irregularities such as the umbilicus, the patient feels a sense of hot and treatment may be discontinued. Therefore, in order toeliminate the irregularities of these areas, compensators are manufactured and measured to decrease in temperature. The temperature of the four sites (umbilicus, near the umbilicus, 5 cm below the umbilicus, back) was measured five times around the umbilicus in patients who were treated at oncological hyperthermia treatment device (EHY-2000, Oncotherm Kft, Hungary). The temperature sensor (TM-100, Oncotherm Kft, Hungary) was attached to four sites and the changes were observed at 5, 15, 25, 35, and 50 minutes after treatment. Compensators of three materials were used(Vaseline, Bolus, Dental resin). The data measured five times were compared for each compensator. he temperature change when the compensator was not used increase from 34.65 degrees to 42.9 degrees on average. The near umbilicus was changed from 32.20 degrees to 37.00 degrees, and the 5 cm below the umbilicus was changed from 31.90 to 34.41 degrees. When the compensator material was inserted into the umbilicus, the temperature change was measured as 5.42 degrees for bolus, 6.55 degrees for vaseline, and 6.83 degrees for resin. Using the compensator in the region where the irregularities such as the umbilicus, the heat sensation could be reduced. the use of a resin that can be customized not only lowers the temperature but also significantly reduces the feeling of the patient. It will be possible to reduce the heat sensation in the treatment and to treat it in a more comfortable condition
[en] The derivation of the optimum mean diameter of magnetic nanoparticles (MNP) for hyperthermia as a tumour therapy in the literature is commonly reduced to application of the Neel relaxation model. Serious restrictions of this model for MNP for hyperthermia are discussed and a way is outlined to a more comprehensive model including hysteresis.
[en] Hyperthermia for the treatment of cancer has been introduced for a long time and the biological effect for the use of hyperthermia to treat malignant tumors has been well established and encouraging clinical results have been observed. Unfortunately, however, the engineering or technical aspects of hyperthermia for the deep seated tumors has not been satisfactory. We developed the radiofrequency capacitive hyperthermia device (Greenytherm-GY8) in cooperation with Yonsei Cancer Center and Green Cross Medical Corporation. It was composed with 8-10 MHz RF generator, capacitive electrode, matching system, cooling system, temperature measuring system and control PC computer. The thermal profile was investigated in agar phantom, animals and in human tumors, heated with capacitive RF device. Deep and homogeneous heating could be achieved in a large phantom of 25 cm diameter and 19 cm thick when heated with a pair of 23 cm diameter electrodes, coupled to both bases of the phantom, when the size of the two electrodes was not the same, the region near the smaller electrode was preferentially heated. It was, therefore, possible to control the depth of heating by choosing proper size of electrodes. Therapeutic temperature (42-43 .deg. C) could be obtained in the living animal experiments. Indications are that deep heating of human tumors might be achieved with the capacitive method, provided that subcutaneous fat layer is cooled by temperature controlled bolus and large size of electrodes
[en] Clinical trials have shown that hyperthermia is a potent adjuvant to conventional cancer treatments, but the temperatures currently achieved in the clinic are still suboptimal. Hyperthermia treatment planning simulations have potential to improve the heating profile of phased-array applicators. An important open challenge is the development of an effective optimization procedure that enables uniform heating of the target region while keeping temperature below a threshold in healthy tissues. In this work, we analyzed the effectiveness and efficiency of a recently proposed optimization approach, i.e. focusing via constrained power optimization (FOCO), using 3D simulations of twelve clinical patient specific models. FOCO performance was compared against a clinically used particle swarm based optimization approach. Evaluation metrics were target coverage at the 25% iso-SAR level, target hotspot quotient, median target temperature (T50) and computational requirements. Our results show that, on average, constrained power focusing performs slightly better than the clinical benchmark (T50 °C), but outperforms this clinical benchmark for large target volumes (40 cm, T50 °C). In addition, the results are achieved in a shorter time (%) and are repeatable because the approach is formulated as a convex optimization problem. (paper)
[en] New linear multi-row, multi-frequency arrays have been designed, constructed and tested as fully operational ultrasound probes to produce confocal imaging and therapeutic acoustic intensities with a standard commercial ultrasound imaging system. The triple-array probes and imaging system produce high quality B-mode images with a center row imaging array at 5.3 MHz and sufficient acoustic power with dual therapeutic arrays to produce mild hyperthermia at 1.54 MHz. The therapeutic array pair in the first probe design (termed G3) utilizes a high bandwidth and peak pressure, suitable for mechanical therapies. The second multi-array design (termed G4) has a redesigned therapeutic array pair which is optimized for a high time-averaged power output suitable for mild hyperthermia applications. The 'thermal therapy' design produces more than 4 W of acoustic power from the low-frequency arrays with only a 10.5 deg. C internal rise in temperature after 100 s of continuous use with an unmodified conventional imaging system or substantially longer operation at lower acoustic power. The low-frequency arrays in both probe designs were examined and contrasted for real power transfer efficiency with a KLM model which includes all lossy contributions in the power delivery path from system transmitters to the tissue load. Laboratory verification was successfully performed for the KLM-derived estimates of transducer parallel model acoustic resistance and dissipation resistance, which are the critical design factors for acoustic power output and undesired internal heating, respectively
[en] This work is a preliminary research which is opening a field of examination of this complex clinic method (i.e. treatment using ablation applicators). Although it is established in many medical facilities its effects were not analyzed thoroughly and there are many unknown factors which can affect patients in clinical practice. We aim to bring new analysis methods which can simply and clearly determine how the tissue in the treated area will be affected and we want to inspect and overcome potential risks connected to this medical method.
[en] The authors conclude that their results show that thermotolerance modifies the effects of heat, both its direct cytotoxicity and radiosensitization in the same way. At an equal level of cell lethality for non-tolerant and thermotolerant cells, thermal enchancement of radiation effects is the same, both with regard to TER (Dsub(o)) (Haveman et al. 1987), TER (β) and presumably TER (α). With regard to clinical implications, when hyperthermia is to be combined with interstitial low dose-rate irradiation, a substantial enhancement of the effectiveness of irradiation may be expected. (author)