Gold nanoparticle (GNP) enhanced radiosensitization was studied across three tumour cells lines that vary in radiosensitivity for a 2.5 MV photon beam. The intrinsic sensitivity of the cell lines is studied for the effects of GNPs. Three cell lines which exhibit differences in radiation response: prostate adenocarcinoma (PC-3), breast adenocarcinoma (MDA-MB-231), and cervical adenocarcinoma (HeLa) were used to determine thein vitrodose enhancement effects of GNPs combined with a 2.5 MV photon beam. Cells were incubated with 20 μg ml-1GNPs for 24 h, and any extracellular GNPs were washed out prior to each assay. The cellular uptake of GNPs was assessed with inductively coupled plasma optical emission spectroscopy (ICP-OES). Clonogenic assays were conducted to assess cell viability after irradiation. The biological damage was assessed through DNA damage using terminal deoxynucleotidyl transferase dUTP nick end labeling assay (TUNEL). The production of reactive oxygen species (ROS) was assessed using CellRox assays. The enhancement factor when cells were irradiated in the presence of GNPs with 2.5 MV was 1.35 ± 0.46 for HeLa, 1.35 ± 0.11 for MDA-MB-231, and 0.99 ± 0.08 for PC-3 cells. On average, the level of DNA damage increased in MDA-MB-231 and HeLa cells when irradiated with 2.5 MV in the presence of GNPs. Increase in the ROS levels were detected in all cell lines when irradiated in the presence of GNPs. The enhancement effects with GNPs combined with a 2.5 MV photon beam were dependent on the cell line. The enhancement factor for HeLa and MDA-MB-231 supports further investigation of intermediate photon-energy beams in combination with GNPs. The combination of using a conventionally lower energy megavoltage beam with gold nanoparticles may become applicable in the clinical setting due to reduced skin dose and enhanced secondary electron production.

Objective. This study investigates the feasibility of using a clinically relevant lower energy 2.5 megavoltage (MV) photon beam in combination with gold nanoparticles (GNPs).Approach.Pancreatic cancer cell line, BxPC-3 impregnated with GNPs were exposedin vitroto 2.5 MV photon beam and compared with orthovoltage 225 kV and clinical 6 MV photon beam. Bare, 50 nm diameter, spherical GNPs were introduced in the cell culture 24 h prior to irradiation at a concentration of either 10μg ml-1or 50μg ml-1. GNP uptake was determined using inductively coupled plasma optical emission spectroscopy. The cells were irradiated with doses between 0 Gy to 8 Gy. Cell survival curves were obtained via clonogenic assay using immediate or delayed plating (24 h) methods 12 d after irradiation. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to evaluate DNA damage at two time points post irradiation, immediate and 24 h for 1 Gy and 6 Gy.Main results. The enhancement factor (EF) in BxPC-3 cells was greatest for cells incubated with 50μg ml-1of GNPs analyzed immediately post irradiation. Cells irradiated with 225 kV showed greatest EF (1.57 ± 0.15), followed by 2.5 MV (1.51 ± 0.04). The lowest EF was seen for 6 MV, immediate plating (1.10 ± 0.04). A significant increase in the number of DNA double strand breaks (DSB) was observed in cells incubated with 50μg ml-1of GNPs irradiated at 6 Gy with 225 kV and 2.5 MV. There was no significant increase in DSBs for the cells irradiated with 6 MV.Significance.These results suggest that the 2.5 MV could be a compromise between an orthovoltage energy beam and a clinical 6 MV beam, showing comparable reduction in cell survival to the 225 kV beam. Future GNP radiation enhancement research may focus on intermediate energy beams.

Purpose:This study presents an evaluation of the dosimetric performance of radiochromic EBT4 films for clinical proton therapy, benchmarked against the widely used EBT3 model. Key parameters assessed include dose-response behavior, energy dependence, sensitivity, reproducibility, temporal stability, and longitudinal and lateral linear energy transfer (LET) effects. Methods:EBT4 films from three independent batches and one batch of EBT3 films were irradiated using monoenergetic therapeutic clinical proton beams ranging from 70 to 225 MeV. Film irradiation was done at various depths in a solid water phantom, while doses from 0.25 to 20 Gy were delivered. Following scanning, the film responses were quantified as net optical density and calibrated with absolute dose measurements from a parallel plate ionization chamber. Temporal kinetics of net optical density were studied at various time points up to 120 hours post irradiation. Film dependency on LET of the proton beams was assessed through both lateral beam profiles and longitudinal depth-dependent analyses beyond pristine Bragg peaks. Results:EBT4 films exhibited a highly linear and reproducible dose-response (R² > 0.998), with minimal energy dependence (<3%) across 70 to 225 MeV proton energies. Compared to EBT3, EBT4 films showed an under-response of approximately 13%-20% at 10 Gy, depending on the batch, with a batch-to-batch variation of ∼8% observed between EBT4 films. Reproducibility between independent irradiations was within 1%, and sensitivity tests confirmed the ability to resolve dose variations as small as ±5% for doses as low as 0.5 Gy. The film's optical density stabilized within 24 hours post-irradiation. LET-dependent response was observed in high-LET regions for EBT4 films, similar to EBT3 films. Conclusions:While EBT4 films exhibit relatively lower sensitivity compared to EBT3 and LET corrections remain necessary in high-gradient dose regions, EBT4 films are a promising candidate for routine and high-resolution proton dose measurements, provided that batch-specific calibration is performed.

Objective. We aim to characterize kinetics of radiation-induced optical density in newly released EBT4 radiochromic films exposed to clinical x-rays. Several film models and batches were evaluated for the film sensitivity, optical signal increasing with time, relative film noise, and minimum detectable limits (MDL).Approach. Radiochromic film pieces from a single batch of EBT3 and three batches of EBT4 were exposed to doses of 77.38 cGy, 386.92 cGy, and 773.84 cGy using a 6 MV x-ray beam. The films were scanned with a flatbed scanner at specific time intervals up to 120 h. The time-series net optical density of red, green and blue colors was corrected for response of the scanner with time and studied to establish the saturation characteristics of film polymerization process. Dose-response from 3.86 cGy to 1935 cGy was also determined for each color. MDL of the films was quantitatively defined as the dose that would double the net optical density of red color above the standard deviation of the residual signal at zero dose. The relative noise characteristics of EBT3 versus EBT4 were studied as a function of time, dose and scanner resolution.Main Results. For doses ≥ 100 cGy, analysis revealed a stability of optical density beyond 48 h post-exposure for EBT3 and EBT4 films. EBT3 films attained 80%-90% of their net optical density at 48 h within minutes of irradiation, compared to 72%-88% for EBT4 films. The rate of growth was slowest for blue color, fastest for red, while green was in between the two. The MDL for EBT4 averaged 15 cGy for three batches, whereas EBT3 films reliably detected doses as low as 8.5 cGy.Significance. Several batches of the new EBT4 film showed slightly lower response compared to its predecessor over 3.86 cGy to 1935 Gy range. For all practical purposes, the post-irradiation growth of polymers ceases between 48 to 60 h for both EBT films. Overall, the EBT4 film exhibited noise characteristics similar to EBT3, except for lower doses where the noise was observed to be higher than its predecessor.

Purpose: The global cancer burden and mortality rates are increasing, with significant disparities in access to care in low- and middle-income countries (LMICs). This study aimed to identify radiology and radiation therapy needs in LMICs from the perspective of departmental and institutional leaders. Methods and Materials: A survey was developed and conducted by the American Association of Physicists in Medicine Global Needs Assessment Committee and the American Association of Physicists in Medicine International Council. The survey, organized into 5 sections (Introduction, Infrastructure Needs, Education Needs, Research Needs, and General Information), was open to respondents from March 1, to August 16, 2022. Results: A total of 175 responses were received from 6 global regions: Africa (31.4%), the Americas (17.7%), the Eastern Mediterranean (14.3%), Europe (9.1%), Southeast Asia (23.4%), and the Western Pacific (4.0%). The greatest reported need was for new or updated equipment, particularly positron emission tomography/computed tomography imaging technology. There was also a high demand for clinical and equipment training. Approximately 25% of institutions reported a lack of radiology-based cancer screening programs because of high health care costs and a shortage of specialized equipment. Many institutions that expressed interest in research face funding and grant challenges. Conclusions: The findings highlight critical areas where organizations can support LMICs in enhancing radiology and radiation therapy services to mitigate the growing cancer burden.

Objective. This study simulated the potential of gold nanoparticles (GNPs) to improve the effectiveness of radiation therapy in pancreatic cancer cases. The purpose of this study was to assess the impact of GNPs on tumor control probability (TCP) and normal tissue complication probability (NTCP) in pancreatic cancer cases undergoing radiation therapy. The work aimed to compare treatment plans generated with a novel 2.5 MV beam using GNPs to conventional 6 MV plans and evaluate the dose-volume histogram (DVH), TCP, and NTCP. Approach. Treatment planning for five pancreatic computed tomography (CT) images was performed using the open-source MATLAB-based treatment planning program matRad. MATLAB codes were developed to calculate the relative biological effectiveness (RBE) of GNPs and apply the corresponding dose and RBE values to each voxel. TCP and NTCP were calculated based on the applied RBE values. Main results. Adding GNPs to the 2.5 MV treatment plan resulted in a significant increase in TCP, from around 59% to 93.5%, indicating that the inclusion of GNPs improved the effectiveness of the radiation treatment. The range in NTCP without GNPs was relatively larger compared to that with GNPs. Significance. The results indicated that the addition of GNPs to a 2.5 MV plan can increase TCP while maintaining a relatively low NTCP value (<1%). The use of GNPs may also reduce NTCP values by decreasing the dose to normal tissues while maintaining the same prescribed dose to the tumor. Hence, the addition of GNPs can improve the balance between TCP and NTCP.

Radiosurgery and stereotactic radiotherapy have established themselves as precise and accurate areas of radiation oncology for the treatment of brain and extracranial lesions. Along with the evolution of other methods of radiotherapy, this type of treatment has been associated with significant advances in terms of a variety of modalities and techniques to improve the accuracy and efficacy of treatment. This paper provides a comprehensive overview of the progress in stereotactic radiosurgery (SRS) over several decades, and includes a review of various articles and research papers, commencing with the emergence of stereotactic techniques in radiotherapy. Key clinical aspects of SRS, such as fixation methods, radiobiology considerations, quality assurance practices, and treatment planning strategies, are presented. In addition, the review highlights the technological advancements in treatment modalities, encompassing the transition from cobalt-based systems to linear accelerator-based modalities. By addressing these topics, this study aims to offer insights into the advancements that have shaped the field of SRS, that have ultimately enhanced the accuracy and effectiveness of treatment.

AbstractPurposeThe shallow depth of maximum dose and higher dose fall‐off gradient of a 2.5 MV beam along the central axis that is available for imaging on linear accelerators is investigated for treatment of shallow tumors and sparing the organs at risk (OARs) beyond it. In addition, the 2.5 MV beam has an energy bridging the gap between kilo‐voltage (kV) and mega‐voltage (MV) beams for applications of dose enhancement with high atomic number (Z) nanoparticles.MethodsWe have commissioned and utilized a MATLAB‐based, open‐source treatment planning software (TPS), matRad, for intensity‐modulated radiation therapy (IMRT) dose calculations. Treatment plans for prostate, liver, and head and neck (H&N), nasal cavity, two orbit cases, and glioblastoma multiforme (GBM) were performed and compared to a conventional 6 MV beam. Additional Monte Carlo calculations were also used for benchmarking the central axis dose.ResultsBoth beams had similar planning target volume (PTV) dose coverage for all cases. However, the 2.5 MV beam deposited 6%–19% less integral doses to the nasal cavity, orbit, and GBM cases than 6 MV photons. The mean dose to the heart in the liver plan was 10.5% lower for 2.5 MV beam. The difference between the doses to OARs of H&N for two beams was under 3%. Brain mean dose, brainstem, and optic chiasm max doses were, respectively, 7.5%–14.9%, 2.2%–8.1%, and 2.5%–19.0% lower for the 2.5 MV beam in the nasal cavity, orbit, and GBM plans.ConclusionsThis study demonstrates that the 2.5 MV beam can produce clinically relevant treatment plans, motivating future efforts for design of single‐energy LINACs. Such a machine will be capable of producing beams at this energy beneficial for low‐ and middle‐income countries, and investigations on dose enhancement from high‐Z nanoparticles.

Gas sensors based on metal oxide semiconductors have recently captured more research interest because they are cost-effective, portable, highly sensitive, and easily manufactured. With increased technological development, modern industries and advanced devices are now focused on process management and validation. Sensors are fundamental to these advancements and require enhanced sensitivity, rapid responsiveness with recovery, and less power usage at affordable rates. Nanomaterials significantly increase the sensing capability of sensors because of their greater surface area. Porous nanomaterials have larger surface areas with outstanding electrical and thermal conductivity, making them promising materials for use in gas sensors. The key improvements in gas sensors based on carbon nanotubes involve high sensitivity and selectivity by functionalizing a number of materials, including noble metals, metal oxides, and polymers. Functionalization with a variety of materials can make the sensor more sensitive to harmful gases by making them more selective and sensitive. This chapter provides a comprehensive analysis of current and past gases-sensing devices using carbon nanotubes. Metal oxide hybrid materials are described, which should prove helpful in developing highly advanced gas sensors.

Film dosimeters provide two-dimensional measurement with high spatial resolution over a large area. There are, in general, two types of films used as dosimeters: radiographic and radiochromic. Radiographic films have been phased out of most of radiotherapy clinics; radiochromic films are now widely used in radiation therapy dosimetry and particularly in quality assurance (QA), especially for planar dose distribution comparisons. This chapter provides a summary of film-based dosimetry and their basic principles and applications in radiation dosimetry. Furthermore, the history of film, origin and mechanism of response to radiation, factors influencing the film response, applications, and practical examples are also discussed in more details for radiochromic films.