Status of hyperthermia in the treatment of advanced liver cancer

Synthesised Conductive/Magnetic Composite Particles for Magnetic Ablations of Tumours

Ablation is a clinical cancer treatment, but some demands are still unsatisfied, such as electromagnetic interferences amongst multiple ablation needles during large tumour treatments. This work proposes a physical synthesis for composite particles of biocompatible iron oxide particles and liquid metal gallium (Ga) with different alternative-current (AC)-magnetic-field-induced heat mechanisms of magnetic particle hyperthermia and superior resistance heat. By some imaging, X-ray diffraction, and vibrating sample magnetometer, utilised composite particles were clearly identified as the cluster of few iron oxides using the small weight ratio of high-viscosity liquid metal Ga as conjugation materials without surfactants for physical targeting of limited fluidity. Hence, well penetration inside the tissue and the promotion rate of heat generation to fit the ablation requirement of at least 60 °C in a few seconds are achieved. For the injection and the post-injection magnetic ablations, the volume variation ratios of mice dorsal tumours on Day 12 were expressed at around one without tumour growth. Its future powerful potentiality is expected through a percutaneous injection.

Magnetic Nanomaterials for Arterial Embolization and Hyperthermia of Parenchymal Organs Tumors: A Review

Magnetic hyperthermia (MH), proposed by R. K. Gilchrist in the middle of the last century as local hyperthermia, has nowadays become a recognized method for minimally invasive treatment of oncological diseases in combination with chemotherapy (ChT) and radiotherapy (RT). One type of MH is arterial embolization hyperthermia (AEH), intended for the presurgical treatment of primary inoperable and metastasized solid tumors of parenchymal organs. This method is based on hyperthermia after transcatheter arterial embolization of the tumor’s vascular system with a mixture of magnetic particles and embolic agents. An important advantage of AEH lies in the double effect of embolotherapy, which blocks blood flow in the tumor, and MH, which eradicates cancer cells. Consequently, only the tumor undergoes thermal destruction. This review introduces the progress in the development of polymeric magnetic materials for application in AEH.

Heat Transfer in Biological Spherical Tissues during Hyperthermia of Magnetoma

Hyperthermia therapy is now being used to treat cancer. However, understanding the pattern of temperature increase in biological tissues during hyperthermia treatment is essential. In recent years, many physicians and engineers have studied the use of computational and mathematical models of heat transfer in biological systems. The rapid progress in computing technology has intrigued many researchers. Many medical procedures also use engineering techniques and mathematical modeling to ensure their safety and assess the risks involved. One such model is the modified Pennes bioheat conduction equation. This paper provides an analytical solution to the modified Pennes bioheat conduction equation with a single relaxation time by incorporating in it the (MGT) equation. The suggested model examines heat transport in biological tissues as forming an infinite concentric spherical region during magnetic fluid hyperthermia. To investigate thermal reactions caused by temperature shock, specifically the influence of heat generation through heat treatment on a skin tumor [AEGP9], the Laplace transformation, and numerical inverse transformation methods are used. This model was able to explain the effects of different therapeutic approaches such as cryotherapy sessions, laser therapy, and physical occurrences, transfer, metabolism support, and blood perfusion. Comparison of the numerical results of the suggested model with those in the literature confirmed the validity of the model's numerical results.

Mild Magnetic Hyperthermia-Activated Innate Immunity for Liver Cancer Therapy

Magnetic hyperthermia therapy (MHT) is noninvasive and features excellent tissue penetration for deep-seated tumors, but unfortunately, it suffers the low therapeutic efficacy due to the limited magneto-thermal efficiency and insufficient intratumor accumulation of conventional intravenous-injected magnetic nanoparticles, which are actually mostly sequestered by the mononuclear phagocyte system, especially the liver. Such a disadvantageous characteristic of preferential liver uptake is here exploited, for the first time as far as we know, to treat orthotopic liver cancer by mild MHT using specially designed composite magnetic nanoparticles. A kind of core-shell-structured and Zn²⁺-doped Zn-CoFe₂O₄@Zn-MnFe₂O₄ superparamagnetic nanoparticles (ZCMF) has been synthesized which exhibits excellent and highly controllable magnetic hyperthermia performance owing to an exchange-coupled magnetism between the core and shell, and Zn²⁺ doping. The controllable mild MHT at 43-44 °C based on ZCMF demonstrates almost complete inhibition of liver cancer cell proliferation and tumor growth, which is associated with the suppression of heat shock protein 70 (HSP70) expression. More importantly, the mild MHT-treated liver cancer cells are capable of activating natural killer (NK) cells by dramatically upregulating the expression of UL16-binding proteins (ULBPs), ligands of natural killer group 2 member D (NKG2D). As a result, the growth of both xenograft tumors and orthotopic liver tumors were almost completely suppressed under mild MHT via induced NK-cell-related antitumor immunity in vivo. This work not only evidences the great potential of mild MHT but also reveals the underlying immunity activation mechanism in liver cancer treatment by mild MHT.

Optical signatures of radiofrequency ablation in biological tissues

Accurate monitoring of treatment is crucial in minimally-invasive radiofrequency ablation in oncology and cardiovascular disease. We investigated alterations in optical properties of ex-vivo bovine tissues of the liver, heart, muscle, and brain, undergoing the treatment. Time-domain diffuse optical spectroscopy was used, which enabled us to disentangle and quantify absorption and reduced scattering spectra. In addition to the well-known global (1) decrease in absorption, and (2) increase in reduced scattering, we uncovered new features based on sensitive detection of spectral changes. These absorption spectrum features are: (3) emergence of a peak around 840 nm, (4) redshift of the 760 nm deoxyhemoglobin peak, and (5) blueshift of the 970 nm water peak. Treatment temperatures above 100 °C led to (6) increased absorption at shorter wavelengths, and (7) further decrease in reduced scattering. This optical behavior provides new insights into tissue response to thermal treatment and sets the stage for optical monitoring of radiofrequency ablation.

Solving the Time- and Frequency-Multiplexed Problem of Constrained Radiofrequency Induced Hyperthermia

Targeted radiofrequency (RF) heating induced hyperthermia has a wide range of applications, ranging from adjunct anti-cancer treatment to localized release of drugs. Focal RF heating is usually approached using time-consuming nonconvex optimization procedures or approximations, which significantly hampers its application. To address this limitation, this work presents an algorithm that recasts the problem as a semidefinite program and quickly solves it to global optimality, even for very large (human voxel) models. The target region and a desired RF power deposition pattern as well as constraints can be freely defined on a voxel level, and the optimum application RF frequencies and time-multiplexed RF excitations are automatically determined. 2D and 3D example applications conducted for test objects containing pure water (r_target = 19 mm, frequency range: 500–2000 MHz) and for human brain models including brain tumors of various size (r₁ = 20 mm, r₂ = 30 mm, frequency range 100–1000 MHz) and locations (center, off-center, disjoint) demonstrate the applicability and capabilities of the proposed approach. Due to its high performance, the algorithm can solve typical clinical problems in a few seconds, making the presented approach ideally suited for interactive hyperthermia treatment planning, thermal dose and safety management, and the design, rapid evaluation, and comparison of RF applicator configurations.

Ultrashort Echo Time Quantitative Susceptibility Mapping (UTE-QSM) of Highly Concentrated Magnetic Nanoparticles: A Comparison Study about Different Sampling Strategies

The ability to accurately and non-invasively quantify highly concentrated magnetic nanoparticles (MNPs) is desirable for many emerging applications. Ultrashort echo time quantitative susceptibility mapping (UTE-QSM) has demonstrated the capability to detect high iron concentrations. In this study, we aimed to investigate the effect of different sampling trajectories on the accuracy of quantification based on MNPs acquired through UTE-QSM. A phantom with six different MNP concentrations was prepared for UTE-QSM study with different UTE sampling trajectories, including radial acquisition, continuous single point imaging (CSPI), and Cones with four different gradient stretching factors of 1.0, 1.2, 1.4, and 1.6. No significant differences were found in QSM values derived from the different UTE sampling strategies, suggesting that the UTE-QSM technique could be accelerated with extended Cones sampling.

Polyacrylamide Ferrogels with Magnetite or Strontium Hexaferrite: Next Step in the Development of Soft Biomimetic Matter for Biosensor Applications

Magnetic biosensors are an important part of biomedical applications of magnetic materials. As the living tissue is basically a "soft matter." this study addresses the development of ferrogels (FG) with micron sized magnetic particles of magnetite and strontium hexaferrite mimicking the living tissue. The basic composition of the FG comprised the polymeric network of polyacrylamide, synthesized by free radical polymerization of monomeric acrylamide (AAm) in water solution at three levels of concentration (1.1 M, 0.85 M and 0.58 M) to provide the FG with varying elasticity. To improve FG biocompatibility and to prevent the precipitation of the particles, polysaccharide thickeners-guar gum or xanthan gum were used. The content of magnetic particles in FG varied up to 5.2 wt % depending on the FG composition. The mechanical properties of FG and their deformation in a uniform magnetic field were comparatively analyzed. FG filled with strontium hexaferrite particles have larger Young's modulus value than FG filled with magnetite particles, most likely due to the specific features of the adhesion of the network's polymeric subchains on the surface of the particles. FG networks with xanthan are stronger and have higher modulus than the FG with guar. FG based on magnetite, contract in a magnetic field 0.42 T, whereas some FG based on strontium hexaferrite swell. Weak FG with the lowest concentration of AAm shows a much stronger response to a field, as the concentration of AAm governs the Young's modulus of ferrogel. A small magnetic field magnetoimpedance sensor prototype with Co_68.6Fe_3.9Mo_3.0Si_12.0B_12.5 rapidly quenched amorphous ribbon based element was designed aiming to develop a sensor working with a disposable stripe sensitive element. The proposed protocol allowed measurements of the concentration dependence of magnetic particles in gels using magnetoimpedance responses in the presence of magnetite and strontium hexaferrite ferrogels with xanthan. We have discussed the importance of magnetic history for the detection process and demonstrated the importance of remnant magnetization in the case of the gels with large magnetic particles.

Methodological aspects of small iron concentrations determination in black yeasts grown in the presence of iron oxide nanoparticles

Nonpathogenic Exophiala nigrum (black yeasts) unicelular organisms of the Baikal Lake were used as a model system for determination of small iron concentrations in the samples grown without or with controlled amount of maghemite nanoparticles (MNPs) in nutrient. MNPs were produced by the electrophysical laser target evaporation technique. Electrostatically stabilized suspensions were prepared using sodium citrate solutions in distilled water. We assumed that one maximum permissive dose of ionic iron in water 1 MPD is equal to 0.3 mg/L. For biological experiments Saburo liquid nutrient medium was prepared with iron concentrations of 0, 102, 103 and 104 MPD. One ml of E. Nigrum cell suspension was added to Saburo liquid nutrient for 24 hours exposure. Followed by sowing onto a solid agar Saburo for 30 days colonies grows. Biosamples for electron microscopy, magnetic and total reflection X-ray fluorescence spectroscopy measurements were collected simultaneously. We were able to comparatively analyze the trace concentrations of iron in the yeast of the order of 10 ppm for control group and 600 ppm for the group grown in the presence of 104 MPD of iron.

Water-Based Suspensions of Iron Oxide Nanoparticles with Electrostatic or Steric Stabilization by Chitosan: Fabrication, Characterization and Biocompatibility

Present day biomedical applications, including magnetic biosensing, demand better understanding of the interactions between living systems and magnetic nanoparticles (MNPs). In this work spherical MNPs of maghemite were obtained by a highly productive laser target evaporation technique. XRD analysis confirmed the inverse spinel structure of the MNPs (space group Fd-3m). The ensemble obeyed a lognormal size distribution with the median value 26.8 nm and dispersion 0.362. Stabilized water-based suspensions were fabricated using electrostatic or steric stabilization by the natural polymer chitosan. The encapsulation of the MNPs by chitosan makes them resistant to the unfavorable factors for colloidal stability typically present in physiological conditions such as pH and high ionic force. Controlled amounts of suspensions were used for in vitro experiments with human blood mononuclear leukocytes (HBMLs) in order to study their morphofunctional response. For sake of comparison the results obtained in the present study were analyzed together with our previous results of the study of similar suspensions with human mesenchymal stem cells. Suspensions with and without chitosan enhanced the secretion of cytokines by a 24-h culture of HBMLs compared to a control without MNPs. At a dose of 2.3, the MTD of chitosan promotes the stimulating effect of MNPs on cells. In the dose range of MNPs 10-1000 MTD, chitosan "inhibits" cellular secretory activity compared to MNPs without chitosan. Both suspensions did not caused cell death by necrosis, hence, the secretion of cytokines is due to the enhancement of the functional activity of HBMLs. Increased accumulation of MNP with chitosan in the cell fraction at 100 MTD for 24 h exposure, may be due to fixation of chitosan on the outer membrane of HBMLs. The discussed results can be used for an addressed design of cell delivery/removal incorporating multiple activities because of cell capability to avoid phagocytosis by immune cells. They are also promising for the field of biosensor development for the detection of magnetic labels.

Permalloy-Based Thin Film Structures: Magnetic Properties and the Giant Magnetoimpedance Effect in the Temperature Range Important for Biomedical Applications

Permalloy-based thin film structures are excellent materials for sensor applications. Temperature dependencies of the magnetic properties and giant magneto-impedance (GMI) were studied for Fe₁₉Ni₈₁-based multilayered structures obtained by the ion-plasma sputtering technique. Selected temperature interval of 25 °C to 50 °C corresponds to the temperature range of functionality of many devices, including magnetic biosensors. A (Cu/FeNi)₅/Cu/(Cu/FeNi)₅ multilayered structure with well-defined traverse magnetic anisotropy showed an increase in the GMI ratio for the total impedance and its real part with temperature increased. The maximum of the GMI of the total impedance ratio ΔZ/Z = 56% was observed at a frequency of 80 MHz, with a sensitivity of 18%/Oe, and the maximum GMI of the real part ΔR/R = 170% at a frequency of 10 MHz, with a sensitivity of 46%/Oe. As the magnetization and direct current electrical resistance vary very little with the temperature, the most probable mechanism of the unexpected increase of the GMI sensitivity is the stress relaxation mechanism associated with magnetoelastic anisotropy.

Physical mechanism and modeling of heat generation and transfer in magnetic fluid hyperthermia through Néelian and Brownian relaxation: a review

Current clinically accepted technologies for cancer treatment still have limitations which lead to the exploration of new therapeutic methods. Since the past few decades, the hyperthermia treatment has attracted the attention of investigators owing to its strong biological rationales in applying hyperthermia as a cancer treatment modality. Advancement of nanotechnology offers a potential new heating method for hyperthermia by using nanoparticles which is termed as magnetic fluid hyperthermia (MFH). In MFH, superparamagnetic nanoparticles dissipate heat through Néelian and Brownian relaxation in the presence of an alternating magnetic field. The heating power of these particles is dependent on particle properties and treatment settings. A number of pre-clinical and clinical trials were performed to test the feasibility of this novel treatment modality. There are still issues yet to be solved for the successful transition of this technology from bench to bedside. These issues include the planning, execution, monitoring and optimization of treatment. The modeling and simulation play crucial roles in solving some of these issues. Thus, this review paper provides a basic understanding of the fundamental and rationales of hyperthermia and recent development in the modeling and simulation applied to depict the heat generation and transfer phenomena in the MFH.

Anticipating hyperthermic efficiency of magnetic colloids using a semi-empirical model: a tool to help medical decisions

Semi-empirical modeling of small nanoparticle heat dissipation helps the designing of medical decisions for clinical cancer magnetic hyperthermia.

Cancer Cell Internalization of Gold Nanostars Impacts Their Photothermal Efficiency In Vitro and In Vivo: Toward a Plasmonic Thermal Fingerprint in Tumoral Environment

Gold nanoparticles are prime candidates for cancer thermotherapy. However, while the ultimate target for nanoparticle-mediated photothermal therapy is the cancer cell, heating performance has not previously been evaluated in the tumoral environment. A systematic investigation of gold nanostar heat-generating efficiency in situ is presented: not only in cancer cells in vitro but also after intratumoral injection in vivo. It is demonstrated that (i) in aqueous dispersion, heat generation is governed by particle size and exciting laser wavelength; (ii) in cancer cells in vitro, heat generation is still very efficient, but irrespective of both particle size and laser wavelength; and (iii) heat generation by nanostars injected into tumors in vivo evolves with time, as the nanostars are trafficked from the extracellular matrix into endosomes. The plasmonic heating response thus serves as a signature of nanoparticle internalization in cells, bringing the ultimate goal of nanoparticle-mediated photothermal therapy a step closer.

Nano-Sized Drug Delivery Systems: Development and Implication in Treatment of Hepatocellular Carcinoma

Liver cancer results in enormous human toll worldwide. Over the years, various chemotherapeutic entities have been employed for treatment of advanced HCC; however, as of yet none embody attributes to improve overall survival. Following rapid advancement in nanotechnology, it is envisage that nanoscale systems may emerge as intriguing platforms to improve chemotherapeutic strategies against various cancers including liver cancer; with better insight in the understanding of pathophysiology of liver cancer and material science, the field of nanotechnology may bring newer hope to liver cancer treatment. Reckoning with these, we detailed the arsenal of nanoformulations that are in various stages of clinical development/ preclinical settings for the treatment of liver cancer together with providing a glimpse of the attributes of nanotechnology in revolutionizing the status of chemotherapeutic modalities.

Microwave resonant and zero-field absorption study of doped magnetite prepared by a co-precipitation method

Fe3O4 and ZnxFe3-xO4 pure and doped magnetite magnetic nanoparticles (NPs) were prepared in aqueous solution (Series A) or in a water-ethyl alcohol mixture (Series B) by the co-precipitation method. Only one ferromagnetic resonance line was observed in all cases under consideration indicating that the materials are magnetically uniform. The shortfall in the resonance fields from 3.27 kOe (for the frequency of 9.5 GHz) expected for spheres can be understood taking into account the dipolar forces, magnetoelasticity, or magnetocrystalline anisotropy. All samples show non-zero low field absorption. For Series A samples the grain size decreases with an increase of the Zn content. In this case zero field absorption does not correlate with the changes of the grain size. For Series B samples the grain size and zero field absorption behavior correlate with each other. The highest zero-field absorption corresponded to 0.2 zinc concentration in both A and B series. High zero-field absorption of Fe3O4 ferrite magnetic NPs can be interesting for biomedical applications.

Drug targeting using solid lipid nanoparticles

The present review aims to show the features of solid lipid nanoparticles (SLNs) which are at the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery and research. Because of some unique features of SLNs such as their unique size dependent properties it offers possibility to develop new therapeutics. A common denominator of all these SLN-based platforms is to deliver drugs into specific tissues or cells in a pathological setting with minimal adverse effects on bystander cells. SLNs are capable to incorporate drugs into nanocarriers which lead to a new prototype in drug delivery which maybe used for drug targeting. Hence solid lipid nanoparticles hold great promise for reaching the goal of controlled and site specific drug delivery and hence attracted wide attention of researchers. This review presents a broad treatment of targeted solid lipid nanoparticles discussing their types such as antibody SLN, magnetic SLN, pH sensitive SLN and cationic SLN.

3D viability imaging of tumor phantoms treated with single-walled carbon nanohorns and photothermal therapy

A new image analysis method called the spatial phantom evaluation of cellular thermal response in layers (SPECTRL) is presented for assessing spatial viability response to nanoparticle enhanced photothermal therapy in tissue representative phantoms. Sodium alginate phantoms seeded with MDA-MB-231 breast cancer cells and single-walled nanohorns were laser irradiated with an ytterbium fiber laser at a wavelength of 1064 nm and irradiance of 3.8 W cm(-2) for 10-80 s. SPECTRL quantitatively assessed and correlated 3D viability with spatiotemporal temperature. Based on this analysis, kill and transition zones increased from 3.7 mm(3) and 13 mm(3) respectively to 44.5 mm(3) and 44.3 mm(3) as duration was increased from 10 to 80 s. SPECTRL provides a quantitative tool for measuring precise spatial treatment regions, providing information necessary to tailor therapy protocols.

In vitro magnetic hyperthermia response of iron oxide MNP’s incorporated in DA3, MCF-7 and HeLa cancer cell lines

In the current work, iron oxide magnetic nanoparticles (MNP’s) were synthesized by thermal decomposition of Fe(acac)3-(iron acetylacetonate) compounds in high-boiling organic solvents containing stabilizing surfactants and examined as possible agents for magnetic hyperthermia treatment, according to their structural, magnetic and heating properties. Three different cancer cell lines (DA3, MCF-7 and HeLa cell lines) were used to assess the suitability of the MNP’s. The experimental results proved that the synthesized MNPs are non-toxic and the uptake efficiency was extremely good. Further, from in vitro hyperthermia results, very fast thermal response was observed (reaching hyperthermia levels in less than 200 s), which minimize the duration of the cell and human body exposure in a high frequency AC external magnetic field.

Noninvasive thermometry assisted by a dual-function ultrasound transducer for mild hyperthermia

Mild hyperthermia is increasingly important for the activation of temperature-sensitive drug delivery vehicles. Noninvasive ultrasound thermometry based on a 2-D speckle tracking algorithm was examined in this study. Here, a commercial ultrasound scanner, a customized co-linear array transducer, and a controlling PC system were used to generate mild hyperthermia. Because the co-linear array transducer is capable of both therapy and imaging at widely separated frequencies, RF image frames were acquired during therapeutic insonation and then exported for off-line analysis. For in vivo studies in a mouse model, before temperature estimation, motion correction was applied between a reference RF frame and subsequent RF frames. Both in vitro and in vivo experiments were examined; in the in vitro and in vivo studies, the average temperature error had a standard deviation of 0.7°C and 0.8°C, respectively. The application of motion correction improved the accuracy of temperature estimation, where the error range was 1.9 to 4.5°C without correction compared with 1.1 to 1.0°C following correction. This study demonstrates the feasibility of combining therapy and monitoring using a commercial system. In the future, real-time temperature estimation will be incorporated into this system.

Supraphysiological thermal injury in different human bladder carcinoma cell lines

Depending on the duration of exposure to supraphysiological temperatures, cellular proteins and organelles can suffer from structural alternations and irreversible denaturation, which may induce cell death. The thermotolerance of three human urinary bladder carcinoma cell lines, TSGH-8301, J82 and TCC-SUP (cytological grade 2, 3 and 4, respectively), was investigated in the present study. A home-made heating stage was used to provide a constant temperature for different cell lines of bladder carcinoma. The experimental data showed that the TCC-SUP and TSGH-8301 cells exhibited the lowest and highest thermotolerances, respectively, while J82 cells were intermediate. Moreover, the differences in the thermotolerances for the TSGH-8301 and J82 cells are significant when the supraphysiological temperature is higher than 43 degrees C. As for TSGH-8301 and TCC-SUP cells, the thermotolerances are significantly different for all of the thermal treatments tested. Furthermore, the thermotolerances of J82 and TCC-SUP are significantly different when the cells are exposed to a temperature less than 50 degrees C for longer than 2 min. Overall, the results suggest that the high cytological grade of the cell line of bladder cancer exhibits a low thermotolerance. The kinematic parameters of the activation energy and frequency factor for bladder cancer cell lines with different cytological grades were also quantitatively evaluated in this work.

Focused RF hyperthermia using magnetic fluids

Heat therapies such as hyperthermia and thermoablation are very promising approaches in the treatment of cancer. Compared with available hyperthermia modalities, magnetic fluid hyperthermia (MFH) yields better results in uniform heating of the deeply situated tumors. In this approach, fluid consisting of superparamagnetic particles (magnetic fluid) is delivered to the tumor. An alternating (ac) magnetic field is then used to heat the particles and the corresponding tumor, thereby ablating it. However, one of the most serious shortcomings of this technique is the unwanted heating of the healthy tissues. This results from the magnetic fluid diffusion from the tumor to the surrounding tissues or from incorrect localization of the fluids in the target tumor area. In this study, the authors demonstrated that by depositing appropriate static (dc) magnetic field gradients on the alternating (ac) magnetic fields, focused heating of the magnetic particles can be achieved. A focused hyperthermia system was implemented by using two types of coils: dc and ac coils. The ac coil generated the alternating magnetic field responsible for the heating of the magnetic particles; the dc coil was used to superimpose a static magnetic field gradient on the alternating magnetic field. In this way, focused heating of the particles was obtained in the regions where the static field was dominated by the alternating magnetic field. In vitro experiments showed that as the magnitude of the dc solenoid currents was increased from 0 to 1.8 A, the specific absorption rate (SAR) of the superparamagnetic particles 2 cm apart from the ac solenoid center decreased by a factor of 4.5, while the SAR of the particles at the center was unchanged. This demonstrates that the hyperthermia system is capable of precisely focusing the heat at the center. Additionally, with this approach, shifting of the heat focus can be achieved by applying different amounts of currents to individual dc solenoids. In vivo experiments were performed with adult rats, where magnetic fluids were injected percutaneously into the tails (with homogeneous fluid distribution inside the tails). Histological examination showed that, as we increased the dc solenoid current from 0.5 to 1.8 A, the total burned volume decreased from 1.6 to 0.2 cm3 verifying the focusing capability of the system. The authors believe that the studies conducted in this work show that MFH can be a much more effective method with better heat localization and focusing abilities.

Magnetic nanoparticles and their applications in medicine

Magnetic nanoparticles have attracted attention in modern medicine and pharmacology owing to their potential usefulness as contrast agents for MRI, as colloidal mediators for cancer magnetic hyperthermia or as active constituents of drug-delivery platforms. This review examines these in vivo applications through an understanding of the involved problems and the current and future possibilities for resolving them. A special emphasis is placed upon magnetic nanoparticle requirements from a physical viewpoint (e.g., relaxivity for MRI, specific absorption rate for hyperthermia and magnetic guidance), the factors affecting their biodistribution after intravenous injection (e.g., size and surface hydrophobic/hydrophilic balance) and the solutions envisaged for enhancing their half-life in the blood compartment and in targeting tumor cells.

The influence of crystallised Fe3O4 on the magnetic properties of coprecipitation-derived ferrimagnetic glass-ceramics

Ferrimagnetic glass-ceramics are potential candidates for magnetic induction hyperthermia, which is one form of inducing deep-regional hyperthermia, by using a magnetic field. The aim of this work was to analyse the influence of the amount of crystallised magnetite on the magnetic properties of glass-ceramic samples. Thus, two different ferrimagnetic glass-ceramics with the composition of the system Na(2)O-CaO-SiO(2)-P(2)O(5)-FeO-Fe(2)O(3) were prepared by melting at 1500 degrees C for 30 min of the coprecipitation-derived starting products. The X-ray diffraction patterns show the presence of nanometric magnetite crystals in a glassy matrix after cooling from melting temperature. The estimated amount of crystallised magnetite varies between 20 and 45 wt.%, as a function of the chemical composition. The morphology of the crystals was studied by scanning electron micrography and transmission electron micrography. Glass transition temperature and thermal stability were investigated by differential thermal analysis. Magnetic hysteresis cycles were analysed using a vibrating sample magnetometer with a maximum applied field of 17 kOe, at room temperature, in quasi-static conditions. Calorimetric measurements were carried out using a magnetic induction furnace. The power losses estimated from calorimetric measurements under a magnetic field of 40 kA/m and 440 kHz are 65 W/g for the glass-ceramic with lower iron oxides content and 25 W/g for the glass-ceramic with higher iron oxide content.

Alcohol and liver cancer

Hepatocellular carcinoma is the eighth most frequent cancer in the world, accounting for approximately 500,000 deaths per year. Unlike many malignancies, hepatocellular carcinoma occurs predominantly within the context of known risk factors, with hepatic cirrhosis being the most common precursor to the development of hepatocellular carcinoma. After ethanol ingestion, the liver represents the major site of metabolism. Ethanol metabolism by alcohol dehydrogenase leads to the generation of acetaldehyde and free radicals that bind rapidly to numerous cellular targets, including components of cell signaling pathways and DNA. In addition to direct DNA damage, acetaldehyde depletes glutathione, an antioxidant involved in detoxification. Chronic ethanol abuse leads to induction of hepatocyte microsomal cytochrome P450 2E1, an enzyme that metabolizes ethanol to acetaldehyde and, in doing so, causes further free radical production and aberrant cell function. Cytochrome P450 2E1-dependent ethanol metabolism is also associated with activation of procarcinogens, changes in cell cycle, nutritional deficiencies, and altered immune system responses. The identification of oxidative stress in mediating many deleterious effects of ethanol in the liver has led to renewed interest in the use of dietary antioxidants as therapeutic agents. Included in this group are S-adenosyl-L-methionine and plant-derived flavanoids.

Nuclear magnetic resonance parameters for monitoring coagulation of liver tissue

A new NMR parameter is suggested as a sensitive tool for monitoring thermal coagulation of liver tissue. That parameter is the proton magnetization exchange time (tau(MEX)) between water and the proteins. tau(MEX) was very sensitive to coagulation and insensitive to temperature, therefore representing only damage to the tissue, independent of effects caused by temperature fluctuations. The measurement of tau(MEX) by two different methods revealed the existence of two or more groups of proteins, characterized by their different transverse relaxation time, and tau(MEX).

Minimally invasive image-guided therapies for hepatocellular carcinoma

Minimally invasive therapies are gaining increasing attention as an alternative to standard surgical therapies in the treatment of primary hepatocellular carcinoma. These include therapies administered transcatheterally (arterial embolization, intraarterial chemoinfusion, and combination chemoembolization) and percutaneously (chemical ablation with ethanol or acetic acid, and thermal ablation with radiofrequency, microwave, or laser energies). Benefits over surgical resection include the anticipated reduction in morbidity and mortality, low cost, suitability for real time image guidance, the ability to perform ablative procedures on outpatients, and the potential application in a wider spectrum of patients, including nonsurgical candidates. This review examines reported clinical success, potential complications, current limitations, and future directions of development of chemoembolization, ethanol and acetic acid instillation, and radiofrequency, microwave, and laser thermal ablation.

Thermal ablation therapy for hepatocellular carcinoma

Thermal ablation strategies, including the use of radiofrequency, microwaves, lasers, and high-intensity focused ultrasound, are gaining increasing attention as an alternative to standard surgical therapies in the treatment of primary hepatocellular carcinoma. Benefits over surgical resection include the anticipated reduction in morbidity and mortality, low cost, suitability for real-time imaging guidance, ability to perform ablative procedures on an outpatient basis, and the potential application in a wider spectrum of patients-including those who are not surgical candidates. In this review, the authors examine the reported clinical success of each of these four therapies, potential complications, current limitations, and future directions of development.

Radiofrequence ablation of liver cancers

Primary and secondary malignant liver cancers are some of most common malignant tumors in the world. Chemotherapy and radiotherapy are not very effective against them. Surgical resection has been considered the only potentially curtive option, but the majority of patients are not candidates for resection because of tumor size, location near major intrahepatic blood vessels and bile ducts, precluding a margin-negative resection, cirrhotic, hepatitis virus infection or multifocial. Radiofrequence ablation (RFA), which is a new evolving effective and minimally invasive technique, can produce coagulative necrosis of malignant tumors. RFA should be used percutaneously, laparscopically, or during the open laparotomy under the guidance of ultrasound, CT scan and MRI. RFA has lots of advantages superior to other local therapies including lower complications, reduced costs and hospital stays, and the possibility of repeated treatment. In general, RFA is a safe, effective treatment for unresectable malignant liver tumors less than 7.0 cm in diameter. We review the principle, mechanism, procedures and experience with RFA for treating malignant liver tumors.

Intraoperative magnetic resonance: the future of surgery

Intraoperative magnetic resonance imaging (iMRI) is a new development in medicine that bridges the specialties of surgery and radiology. Deficiencies in the visualization of anatomical architecture and the perception of tumour boundaries in conventional open surgery have led to the integration of imaging within surgery. The superior soft tissue and multiplanar imaging features of magnetic resonance (MR) make this imaging modality superior to that of alternatives. The unique properties of MR to detect heat change and perfusion, and diffusion characteristics of tissue enhance the usefulness of this medium. Concurrent developments in computer aided image guidance and thermoablative technology, herald the era of minimally invasive tumour ablation. Applications have been developed for areas such as neurosurgery, general surgery, gynaecology and urology.