Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Nanoparticle Enhanced Radiation Therapy
Download Nanoparticle Enhanced Radiation Therapy full books in PDF, epub, and Kindle. Read online Nanoparticle Enhanced Radiation Therapy ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Nanoparticle Enhanced Radiation Therapy by : Erno Sajo
Download or read book Nanoparticle Enhanced Radiation Therapy written by Erno Sajo and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Improved targeting of abnormal cells and tissue in the radiotherapy of cancer has been a long-standing goal of researchers. The central purpose in Nanoparticle-Enhanced Radiotherapy (NPRT) is to more precisely control where the radiation dose is delivered, desirably with subcellular precision, provided we can find a method to bring the nanoparticles to target and control their concentration and size distribution. The contents within this book will cover the rationale and fundamental principles of NPRT, optimal nanoparticle sizes, concentrations, design and fabrication, effective nanoparticle delivery methods, emerging clinical applications of NRT modalities, treatment planning and quality assurance and the potential of NPRT in global health. This volume will serve as a resource for researchers, educators and industry, and as a practical guide or comprehensive reference for students, research trainees and others working in cancer nanomedicine. Part of IOP Series in Global Health and Radiation Oncology." -- Prové de l'editor.
Book Synopsis Nanoparticle Enhanced Radiation Therapy by : Erno Sajo
Download or read book Nanoparticle Enhanced Radiation Therapy written by Erno Sajo and published by Myprint. This book was released on 2020-11-19 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved targeting of abnormal cells and tissue in the radiotherapy of cancer has been a long-standing goal of researchers. The central purpose of nanoparticle-enhanced radiotherapy (NPRT) is to more precisely control where the radiation dose is delivered, desirably with subcellular precision, provided we can find a method to bring the nanoparticles to target as well as control their concentration and size distribution. The contents within this book will cover the rationale and fundamental principles of NPRT, optimal nanoparticle sizes, concentrations, design and fabrication, effective nanoparticle delivery methods, emerging clinical applications of NRT modalities, treatment planning and quality assurance and the potential of NPRT in global health. This volume will serve as a resource for researchers, educators and industry, and as a practical guide or comprehensive reference for students, research trainees and others working in cancer nanomedicine. Key Features Covers the most important advances in nanoparticle-aided radiation therapy over the last few decades Features contributions from leaders in the field Focuses first on the fundamentals of radiosensitization, then it continues with imaging methods and concludes with various clinical applications
Book Synopsis Nanoparticle-Aided Radiotherapy by : Erno Prof. Sajo
Download or read book Nanoparticle-Aided Radiotherapy written by Erno Prof. Sajo and published by Iop Expanding Physics. This book was released on 2020-11-12 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improved targeting of abnormal cells and tissue in the radiotherapy of cancer has been a long-standing goal of researchers. The central purpose of nanoparticle-enhanced radiotherapy (NPRT) is to more precisely control where the radiation dose is delivered, desirably with subcellular precision, provided we can find a method to bring the nanoparticles to target as well as control their concentration and size distribution. The contents within this book will cover the rationale and fundamental principles of NPRT, optimal nanoparticle sizes, concentrations, design and fabrication, effective nanoparticle delivery methods, emerging clinical applications of NRT modalities, treatment planning and quality assurance and the potential of NPRT in global health. This volume will serve as a resource for researchers, educators and industry, and as a practical guide or comprehensive reference for students, research trainees and others working in cancer nanomedicine. Key Features Covers the most important advances in nanoparticle-aided radiation therapy over the last few decades Features contributions from leaders in the field Focuses first on the fundamentals of radiosensitization, then it continues with imaging methods and concludes with various clinical applications
Book Synopsis Nanoparticle Enhanced Radiotherapy by : Reem Hussain Ali Ahmad
Download or read book Nanoparticle Enhanced Radiotherapy written by Reem Hussain Ali Ahmad and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis NANOPARTICLE-AIDED RADIATION THERAPY. by : WILFRED F. NGWA
Download or read book NANOPARTICLE-AIDED RADIATION THERAPY. written by WILFRED F. NGWA and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Physical, Chemical and Biological Modelling for Gold Nanoparticle-enhanced Radiation Therapy by : Floriane Poignant
Download or read book Physical, Chemical and Biological Modelling for Gold Nanoparticle-enhanced Radiation Therapy written by Floriane Poignant and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In radiation therapy, high-Z nanoparticles such as gold nanoparticles (GNPs) have shown particularly promising radiosensitizing properties. At an early stage, an increase in dose deposition and free radicals production throughout the tumour (photoelectric effect) and at sub-cellular scale (Auger cascade) might be responsible for part of the effect for low-energy X-rays. In this Ph.D work, we propose to study these early mechanisms with simulation tools, in order to better quantify them and better understand their impact on cell survival. We first finalised and validated Monte Carlo (MC) models, developed to track electrons down to low energy both in water (meV) and gold (eV). The comparison of theoretical predictions with available experimental data in the literature for gold provided good results, both in terms of secondary electron production and energy loss. This code allowed us to quantify the energy deposited in nanotargets located near the GNP, which is correlated with the probability to generate damages. This study required important optimisations in order to achieve reasonable computing time. We showed a significant increase of the probability of having an energy deposition in the nanotarget larger than a threshold, within 200 nm around the GNP, suggesting that GNPs may be particularly efficient at destroying biological nanotargets in its vicinity. The MC simulation was then used to quantify some chemical effects. At the macroscale, we quantified the increase of free radicals production for a concentration of GNPs. We also compared the radial distribution of chemical species following the ionisation of either a gold nanoparticle or a water nanoparticle. We showed that following an ionization, the average number of chemical species produced is higher for gold compared to water. However, in the vicinity of the nanoparticle, the number of chemical species was not necessarily higher for gold compared to water. This suggests that the effect of GNPs in its vicinity mostly comes from the increase of the probability of having an ionisation. We also studied several scenarios to explain the unexpectedly high experimental increase of the production of fluorescent molecules during the irradiation of a colloidal solution of GNPs and coumarin. Our study suggests that a plausible scenario to explain experimental measurements would be that GNPs interfere with an intermediate molecule, produced following the reaction between a coumarine molecule and a hydroxyl radical. During the last step of this Ph.D work, we injected our MC results in the biophysical model NanOx, originally developed at IPNL to calculate the biological dose in hadrontherapy, to predict cell survival in presence of GNPs. In addition, we implemented the Local Effect Model (LEM), currently the main biophysical model implemented for GNP-enhanced radiation therapy, to compare the NanOx and the LEM predictions with each other. In order to estimate cell survival with the LEM, we used various dosimetric approaches that were proposed in the literature. For a simple system where GNPs were homogeneously distributed in the cell, we showed that the LEM had different outcomes with regard to cell survival, depending on the dosimetric approach. In addition, we obtained an increase of cell death with the biophysical model NanOx that was purely due to the increase of the macroscopic dose. We did not obtain an increased biological effectiveness due to Auger electrons, which comes in contradiction with the LEM predictions. This study suggests that the current biophysical models available to predict the radiosensitizing effect of GNPs must be improved to be predictive. This may be done, for instance, by accounting for potential biological mechanisms evidenced by experimental works.
Book Synopsis Preclinical Evaluation of Nanoparticle Enhanced Breast Cancer Diagnosis and Radiation Therapy by : Jonas Albers
Download or read book Preclinical Evaluation of Nanoparticle Enhanced Breast Cancer Diagnosis and Radiation Therapy written by Jonas Albers and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Triple negative breast cancer (TNBC) is an aggressive type of cancer which makes up 15-20% of all newly diagnosed cases, lacking the main target molecules for tumor specific treatment. Surgery or systemic therapy by chemotherapy are frequently used in the clinic and combined with radiation therapy to improve locoregional control in breast cancer patients after surgery. With a poor prognosis, there is a clear need to explore new treatment options for TNBC. The aim of the here presented PhD project was to evaluate the feasibility to enhance the biological effect of radiation therapy and incre...
Book Synopsis Dose Enhancement with Nanoparticles in Radiotherapy Using Gold-doxorubicin Conjugates by : Simon Vallières
Download or read book Dose Enhancement with Nanoparticles in Radiotherapy Using Gold-doxorubicin Conjugates written by Simon Vallières and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Gold nanoparticles have recently been demonstrated to show properties in increasing energy deposition in tissues upon irradiation by X-rays. The present study uses gold nanoparticles conjugated with doxorubicin, a chemotherapeutic agent. The project acts on two simultaneous fronts, namely with chemotherapy and nanoparticle-enhanced radiotherapy treatments. The aim is to test the effectiveness of gold-doxorubicin conjugates in a radiochemotherapy context for the treatment of murine melanoma tumours. B16-F10 melanoma cells are grafted subcutaneously on the flank of male wild black mice. Intratumoural injections of gold-doxorubicin conjugates are given, followed by a single dose of X-rays. The effectiveness of the treatment is compared to the control groups and dose enhancement is quantified. Tumour growth inhibition was observed for at least six days postirradiation, as well as an enhanced radiobiological effect of gold nanoparticles. However, gold-doxorubicin conjugates were not as cytotoxic as expected. A small animal irradiator was calibrated following the AAPM TG-61 protocol. Dose uncertainties to tumours were assessed by developing a Monte Carlo model of the source using EGSnrc (National Research Council of Canada). Monte Carlo simulations of the 3D dose distributions in tumours were also calculated. Excellent agreement was observed between the source model and experimental measurements, the effective energy of the beam reported by the model showed a 3% difference with the measured value, and less than 1% when compared to the one based on SpekCalc, a semi-empirical spectra calculation tool. Moreover, a standard deviation of 60% on the tumour volume distribution translated into 5% of median dose variation in a mice cohort, which is relatively low. This project lies in the use of a stable gold-doxorubicin conjugate in a combined treatment using both chemotherapy and radiotherapy. This allows to reduce the radiation dose given to healthy tissues while maintaining the same tumour control." --
Book Synopsis Novel Approaches for Cancer Therapy by : Zane Barak Starkewolfe
Download or read book Novel Approaches for Cancer Therapy written by Zane Barak Starkewolfe and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work explores the interaction of X-rays with nanomaterials and examines applications of this interaction for the treatment of cancer. The absorption of X-rays by nanomaterials and the mechanism by which these structures induce the production of radicals is studied. Using nanoparticles of various materials and sizes, we elucidate a mechanism of the interactions between the nanoparticles and the X-ray radiation-generated radical species. We measured the enhanced generation of radicals by nanomaterials irradiated with X-ray-radiation and termed this Nanoparticle Enhanced X-ray Therapy (NEXT). Using this approach we measure an increase in cell death employing various sizes and types of nanoparticles under X-ray radiation. While the enhancement of this cell death has a promising application potential for cancer therapy, the overall benefit will be determined by the overall X-ray absorption and the number of generated radical species. Utilizing the mechanism for radical generation by nanomaterials under X-ray radiation, we devised a novel approach for X-ray Enabled Nanochemistry (XEN) that allows for chemical reactions to take place only on the surface of nanomaterials. These location specific reactions are induced and enhanced by X-ray radiation. Using an approach called X-ray Triggered Chemotherapy (XTC), cancer drug molecules were attached to the oligonucleotide strands bound to the surface of gold nanoparticles and the applications of these nanoparticle drug carriers is explored for the treatment of cancer. In breast cancer cells, we observed an increase in cancer cell death using the XTC approach as compared with the use of either X-ray radiation or chemotherapy alone. We find that nanomaterials can enhance the efficacy of X-rays in cancer treatment and that nanomaterials under X-ray radiation can be used for the remote activation of otherwise dormant cancer drugs at the tumor site.
Book Synopsis Octaarginine Labelled 30 Nm Gold Nanoparticles as Agents for Enhanced Radiotherapy by : Caitlin Latimer
Download or read book Octaarginine Labelled 30 Nm Gold Nanoparticles as Agents for Enhanced Radiotherapy written by Caitlin Latimer and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nanoparticle-aided Radiation Therapy: Micro-dosimetry and Evaluation of the Mediators Producing Biological Damage by : Nava R. Paudel
Download or read book Nanoparticle-aided Radiation Therapy: Micro-dosimetry and Evaluation of the Mediators Producing Biological Damage written by Nava R. Paudel and published by . This book was released on 2014 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation therapy has been established as a standard technique for cancer treatment. Advances in nanotechnology have enabled the application of many new approaches in the diagnosis and treatment of cancer. Achievement of selective enhancement in radiation dose deposition within a targeted tumor, while sparing surrounding normal structures, remains a challenge and one of the major objectives of cancer-related research. This objective can be realized by the insertion of high atomic number (Z) materials in the tumor site. Due to their high atomic number (Z=79) and favorable biological compatibility, gold nanoparticles (AuNPs) have been found very promising in this respect. Another candidate material, platinum (Z=78), offering very similar radiation interaction properties to gold and exhibiting additional cytotoxic effects, has been exploited in chemotherapeutic agents for a long time. A number of studies evaluating dose enhancement on the basis of an approximation of a uniform distribution of individual gold atoms rather than nanoparticles neglect the effects near the gold-tissue interface. Those studies have demonstrated high dose enhancement at low kiloelectronvolt (keV) energies, relevant only to certain brachytherapy nuclides, but have not shown a significant enhancement in clinical megavoltage (MV) radiation beams. However, recent experiments with biological systems have brought mixed results, few of them demonstrating promising cell kill effects exceeding the predictions based on pure dose deposition under MV beams. It has been a general observation in physics that many new phenomena originate from interfaces and hence it is important to closely examine the interface effects between high-Z materials, such as gold or platinum, and low-Z tissues. The small physical dimension of the radiation dose enhancement region, ~ 1 mm or less, and the very high dose gradient pose a great challenge in the investigation of the effects. Nonetheless, the interface effects have been largely overlooked in nanoparticle-aided radiation therapy studies. We explore the radiation effects near the interface of gold and platinum with tissue under a wide range of energies with Monte Carlo (MC) simulations. Our studies show that AuNPs and PtNPs (platinum nanoparticles) can offer a useful dose enhancement effect even in high energy radiotherapy beams, which can be important when critical structures are located close to the tumor. Our MC calculated dose enhancement increase of about 50% due to the removal of the flattening filter from the path of the photon beam of Varian TrueBeam accelerator suggests that flattening-filter-free beams are better suited for nanoparticle-aided radiation therapy. Also, the increase in dose enhancement with the tumor depth suggests that nanopartcle-aided radiation therapy can yield a better outcome while treating deep-seated tumors. Experimental microdosimetry is a non-trivial task, demanding detectors with small sensitive volumes to achieve a high spatial resolution. We have developed a microdosimetry technique utilizing an inexpensive in-house-built photodetector for the measurement of dose in a narrow high dose gradient region next to the interface between gold and tissue. Verification of the experimental results against MC simulations provides a foundation for the application of this technique to biological systems such as cell cultures. Recent studies demonstrating higher cancer cell killing than the predictions based on MC-modeled dose deposition due to AuNPs under radiation beams suggest the action of biochemical effects. Since free radicals are responsible for ~ 2/3 of cell killing in radiotherapy photon beams, we explore the role of gold and platinum in generating free radicals with the electron paramagnetic resonance (EPR) technique. Our results demonstrating higher free radical generation enhancement than the MC modeled enhancement in dose deposition due to thin gold or platinum wires under irradiation suggest that the high-Z material surfaces act as catalysts for free radical generation. The higher surface area to volume ratio and the size quantization effect should make this phenomenon even more pronounced with nanoparticles, thus augmenting the cell killing effect. Our results also show that platinum is as effective as gold in enhancing dose deposition as well as in generating free radicals in aqueous media under radiation beam.
Book Synopsis Harnessing Materials for X-ray Based Cancer Therapy and Imaging by : Surender Kumar Sharma
Download or read book Harnessing Materials for X-ray Based Cancer Therapy and Imaging written by Surender Kumar Sharma and published by Springer Nature. This book was released on 2022-10-31 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the efficacy of nanomaterial-based X-rays enhancers against cancer therapy and imaging in both in vitro and in vivo systems. Also, synthesis, mechanism, and the related biological effects are given. Moreover, nanoparticle-based contrast agents to enhance the image quality are compiled. Finally, special nanoparticle-based contrast agents to enhance the contrast for targeted cancer therapy are covered and discussed.
Book Synopsis Nanopharmaceuticals: Principles and Applications Vol. 3 by : Vinod Kumar Yata
Download or read book Nanopharmaceuticals: Principles and Applications Vol. 3 written by Vinod Kumar Yata and published by Springer Nature. This book was released on 2020-08-19 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the third volume on this subject and focuses on the recent advances of nanopharmaceuticals in cancer, dental, dermal and drug delivery applications and presents their safety, toxicity and therapeutic efficacy. The book also includes the transport phenomenon of nanomaterials and important pathways for drug delivery applications. It goes on to explain the toxicity of nanoparticles to different physiological systems and methods used to assess this for different organ systems using examples of in vivo systems.
Book Synopsis Nanoscale Physical Enhancement by Gold Nanoparticles Under X-ray Irradiation by : Arjun Sharmah
Download or read book Nanoscale Physical Enhancement by Gold Nanoparticles Under X-ray Irradiation written by Arjun Sharmah and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation therapy using X-rays is one of the standard methods of treating cancer. There are numerous studies on examining the use of metallic nanoparticles for cancer therapy ranging from effective enhancement of radiation to targeted drug delivery. However, when it comes to elucidating the mechanism of enhancement of radiation in presence of nanoparticles, although there is a substantial literature on theoretical studies, only a limited experimental work has been done. Elucidating the mechanism can aid in designing optimum nanostructures so as to maximize the enhancement effect which can have far-reaching impact on lowering the dose used in radiation therapy without lowering the effect of the radiation and may even increase its efficacy. Extra electrons released by nanoparticles under X-ray irradiation leads to enhanced electron energy deposition which we call Physical Enhancement (PE) and identify two processes contributing to the PE - firstly, a nanoscale enhancement (T2PE) which occurs near the metal nanoparticle surface and secondly the average PE (T1PE). To probe the nanoscale physical enhancement we have devised a nanostructure made of liposome coated with calcium phosphate and encapsulating a dye based probe (Sulforhodamine-B), we call it CaPEL. CaPEL is mixed with gold nanoparticles and irradiated under hard X-rays. We observed a 2.1 fold enhancement for 0.25 weight percent (wp) of gold, which is equivalent to an enhancement of 42 wp−1 of Au. This enhancement is much higher than the generally accepted average PE of about 1 fold enhancement wp-1 of gold and can only be explained by T2PE. A theoretical calculation was done which supports the experimentally observed enhancement for one gold nanoparticle associated with one CaPEL. A sudden jump in enhancement is observed at around 0.25 wp of gold which is explained by a threshold gold concentration required to achieve a dynamic one-gold -to -one CaPEL association. After the initial jump the enhancement follows a general slope (1 wp−1 of Au) of the average PE, which is further proof of distinct T2PE (separate from average PE) and one-gold-to-one CaPEL association. This phenomenon is explained by Brownian Dynamics simulation. The CaPEL used in the experiment is a robust non-leaky nano-container with an average internal diameter of 68 nm and 15 nm thick external calcium phosphate shell. This is the first experimental nanoscale enhancement measurement. The use of metal nanoparticles as radiation dose enhancers is much more efficient near its surface and use of nanostructures designed to harness T2PE will be able to deliver substantially greater enhancement at much lower gold concentration. This can have implications in cancer treatment in making radiation therapy much more efficient. The probe developed here may also be used for targeted drug delivery with slight modification.
Book Synopsis Gold-nanoparticle-based Theranostic Agents for Radiotherapy of Malignant Solid Tumors by : Sina Moeendarbari
Download or read book Gold-nanoparticle-based Theranostic Agents for Radiotherapy of Malignant Solid Tumors written by Sina Moeendarbari and published by . This book was released on 2016 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation therapy is one of the three major methods of cancer treatment. The fundamental goal of radiotherapy is to deliver high radiation doses to targets while simultaneously minimizing doses to critical structures and healthy normal tissues. The aim of this study is to develop a general, practical, and facile method to prepare nanoscale theranostic agents for more efficacious radiation therapy with less adverse side effects. First, a novel type of gold nanoparticle, hollow Au nanoparticles (HAuNPs) which was synthesized using the unique bubble template synthesis method developed in our lab, are studied in vitro and in vivo to investigate their effect as radiosensitizing agents to enhance the radiation dose during external radiotherapy. The results showed the promising potential of using HAuNPs as radiosensitization agents for efficacious treatment of breast cancer. Second, a novel radiolabeling method is developed to incorporate medical radioisotopes to gold nanoparticles. We incorporate palladium-103 (103Pd), a radioisotope currently in clinical brachytherapy, into a hollow gold nanoparticle. The resulting 103Pd@Au nanoparticles in the form of a colloidal suspension can be administered by direct injection into tumors, serving as internal radiation sources (nanoseeds) for radiation therapy. The size of the nanoseed, ~150nm in diameter, is large enough to prevent nanoseeds from diffusing into other areas while still small enough to allow them to homogeneously distribute inside the tumor. The therapeutic efficacy of 103Pd@Au nanoseeds have been tested when intratumorally injected into a prostate cancer xenograft model. The findings showed that this nanoseed-based brachytherapy has the potential to provide a theranostic solution to unresectable solid tumors. Finally, to make real clinical application more plausible, multi-functional magnetic nanoseeds nanoparticles for imaging-guided radiotherapy are synthesized and characterized.
Book Synopsis Bionanotechnology in Cancer by : D. Sakthi Kumar
Download or read book Bionanotechnology in Cancer written by D. Sakthi Kumar and published by CRC Press. This book was released on 2022-10-27 with total page 679 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cancer research world is looking forward to bionanotechnology to find the best solutions for a complete cure from cancer, which is not possible with the current established treatment methods. The past decade of research on nano imaging and drug delivery in cancer has witnessed many interesting papers and reviews, but there has not been a concise resource that discusses all fields related to nano cancer research in diagnosis and drug delivery. This book fills this gap and presents the latest bionano research in cancer, focusing on nanodiagnostics and nanotherapy. The book is organized into two sections. The section on nanodiagnostics focuses on topics such as diagnostic methods in cancer-related therapy and use of radiolabeled nanoparticles, magnetic nanoparticles, acoustically reflective nanoparticles, X-ray computed tomography, and optical nanoprobes for diagnosis. The section on nanotherapy focuses on nanomaterials in chemotherapy, magnetic nanoparticles for hyperthermia against cancer, phototherapy, nanotechnology-mediated radiation therapy, nanoparticle-mediated small-RNA deliveries for molecular therapies, and theranostics. The book will serve as the gateway to enter the beautiful and elegant field of bionanoscience, which is considered the last hope for the fight against cancer and will be a highly useful resource for the students, researchers, teachers, and curious readers working in this field or related fields.
Book Synopsis Monte Carlo Calculations of Microscopic Dose Enhancement for Gold Nanoparticle-aided Radiation Therapy by : Bernard Jones
Download or read book Monte Carlo Calculations of Microscopic Dose Enhancement for Gold Nanoparticle-aided Radiation Therapy written by Bernard Jones and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gold Nanoparticle-Aided Radiation Therapy (GNRT) is a new paradigm in radiation therapy which seeks to make a tumor more susceptible to radiation damage by modifying its photon interaction properties with an infusion of a high-atomic-number substance. The purpose of this study was to quantify the energy deposition due to secondary electrons from gold nanoparticles on a micrometer scale and to calculate the corresponding microscopic dose enhancement factor during GNRT. The Monte Carlo code EGSnrc was modified to obtain the spectra of secondary electrons from atoms of gold and molecules of water under photon irradiation of a tumor infused with 0.7 wt. % gold. Six different photon sources were used: 125I, 103Pd, 169Yb, 192Ir, 50kVp, and 6MV x-rays. Treating the scored electron spectra as point sources within an infinite medium of water, the event-by-event Monte Carlo code NOREC was used to quantify the radial dose distribution, giving rise to gold and water electron dose point kernels. These kernels were applied to a scanning electron microscope (SEM) image of a gold nanoparticle distribution in tissue. The dose at each point was then calculated, enabling the determination of the microscopic dose enhancement at each point. For the lower energy sources 125I, 103Pd, 169Yb, and 50 kVp, the secondary electron fluence was increased by as much as two orders of magnitude, leading to a one-to-two order of magnitude increase in the electron dose point kernel over radial distances up to 50 um. The dose was enhanced by 100% within 5 um of the nanoparticles, and by 5% as far away as 30 um. This study demonstrates a remarkable microscopic dose enhancement due to gold nanoparticles and low energy photon sources. Given that the dose enhancement exceeds 100% within very short distances from the nanoparticles, the maximum radiobiological benefit may be derived from active targeting strategies that concentrate nanoparticles in close proximity to the cancer cell and/or its nucleus.
