bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charting the development of optical CT and allied methods for 3-D radiation dosimetry: 2022 update - mapping the global research community
Authors: Doran Simon 
Published: November 2023

Abstract
To recognise the many and varied contributions from groups around the world over more than 25 years of research into 3-D radiation dosimetry using optical imaging (primarily optical computed tomography), a systematic review has been conducted with the aim of charting the development of this field. Some 493 publications matched the criteria of the review, and these have been coded with information relating to the category of research, the type of dosimeter material used and the geographical location where the research was conducted. The results of the analysis demonstrate a steady growth in the number of academic groups involved, from 4 at the first DOSGEL meeting in 1999 to over 30 in 2016. The important role played by the DOSGEL and IC3Ddose conference series is demonstrated by the marked biennial trend in publications. The division of publications between categories was 36% materials development, 34% scanner technology, 24% applications, 5% review and 1% teaching. The most common application areas were brachytherapy, proton/particle therapy and IMRT/VMAT. Prior to the introduction of PRESAGE® in 2003, polymer gels were the most popular material, whilst radiochromic dosimeters have dominated in recent years. These and other trends are discussed on the basis of the data presented. A brief discussion of the future of the field, including some personal opinions, ends this brief review.
Gel dosimetry: MRI
Authors: Deene Yves De 
Published: November 2023

Abstract
While a vast amount of scientific literature is available on the topic of gel dosimetry with MRI readout, this wealth of information may seem at first overwhelming for medical physicists and newcomers in this rapidly evolving field of research. With this review, my mission is to streamline the wealth of information in the scientific literature and provide a quick guideline for those making their first steps in implementing gel dosimetry in a clinical environment, while still providing a lookout to new and emerging evolutions in the field. In a first section, the physical mechanisms behind the MRI contrast are briefly explained for both Fricke gels and polymer gels. In a subsequent section, an overview is given of the different MRI pulse sequences and pulse sequence optimization will be discussed. Emphasize is placed on the framework and formalism to calculate optimal parameters. The reliability of MRI-based polymer gel dosimetry will be discussed, and a quick beginner’s guide is provided. Finally, a lookout to new and future developments of polymer gel dosimetry will be given.
CT and CBCT imaging of gel dosimeters: a review of the state of the art
Authors: Jirasek A. , Hilts M. 
Published: November 2023

Abstract
This review covers the main developments in x-ray CT-based polymer gel dosimetry (PGD) and more recently on-board cone-beam CT (CBCT) polymer gel dosimetry. Fundamental work as well as clinically-based applications are described and advantages and disadvantages of approaches highlighted. The body of work present within the literature points towards an overall feasibility of CT PGD and increasingly CBCT PGD as viable tools for the verification of highly complex, high dose radiotherapy treatments.
3D dosimetry of proton beams and influences on response
Authors: Ibbott G. , Carroll M. 
Published: November 2023

Abstract
Proton beams offer the ability to conform dose distributions exquisitely to target volumes, allowing radiation oncologists to avoid exceeding tolerance doses to sensitive normal tissues. Several volumetric dosimeters have shown potential in conventional radiotherapy modalities, but suffer from dose under-responding, or signal quenching, in proton therapy. This reduced response has been seen with gels as well as with radiochromic plastics and may result from dependences on dose rate and linear energy transfer (LET). Investigations have shown that the under-response is affected by the chemical concentration of the active components of PRESAGE®, and changes to the composition have been shown to reduce quenching. It is not clear if similar changes can be made to gels. This report reviews studies into the impact of formulation changes on signal quenching, and the degree to which mathematical corrections might still be needed to achieve accurate dosimetry.
Evolution of 3D X-Ray Dose Computation Algorithms
Authors: Battista J. , Chen J. , Sawchuk S. , Hajdok G. 
Published: November 2023

Abstract
Radiation treatment planning of individual cancer patients relies on the accurate computation of dose distributions in irradiated tissue. Inaccurate dose maps have the potential to mislead clinical decision-making and compromise the balance between effective tumour control and side effects in surrounding normal tissue. In the context of this conference, 3D dosimetry is important for the experimental validation of computed dose distributions. Dose computation methods for external beams of high energy x rays have evolved over the past decade with computer simulation models more closely aligned with the fundamental physics of x-ray scattering and absorption in heterogeneous tissue. In this article, we first present a historical review from a Canadian perspective, followed by an introductory intuitive description of contemporary algorithms used in clinical treatment planning: (1) Convolution-superposition algorithm fundamentally based on the Green’s function method; (2) Stochastic Monte Carlo simulation of x-ray interactions in tissue, and (3) Deterministic numerical solution of a system of Boltzmann transport equations. In principle, all these methods solve the same problem of predicting x-ray scattering and absorption in heterogeneous tissue. However, the mathematical tools differ in their approach and approximations to achieve sufficient speed for routine clinical application. In the conclusion of this article, the evolution of 3D x-ray dose computation is summarized, in terms of accuracy and computational speed.
FLASH radiotherapy and the associated dosimetric challenges
Authors: Ceberg S , Mannerberg A , Konradsson E , Blomstedt M , Kügele M , Kadhim M , Edvardsson A , Bäck S Å J , Petersson K , Jamtheim Gustafsson C , Ceberg C 
Published: November 2023

Abstract
At Lund University and Skåne University Hospital in Lund, Sweden, we have, as the first clinic, modified a clinical Elekta Precise linear accelerator for convertible delivery of ultra-high dose rate (FLASH) irradiation. Whereas recently published reviews highlighted the need for standardised protocols for ultra-high dose rate beam dosimetry to be able to determine the true potential of FLASH irradiation, several dosimetry studies as well as in-vitro and in-vivo experiments have been carried out at our unit. Dosimetric procedures for verification of accurate dose delivery of FLASH irradiation to cell cultures, zebrafish embryos and small animals have been established using radiochromic films and thermo-luminescent dosimeters. Also, recently the first experience of electron FLASH radiotherapy (FLASH-RT) in canine patients in our clinical setting was published. Our research facilities also include a laboratory for 3D polymer gel manufacturing. Recently, we started investigating the feasibility of a NIPAM polymer gel dosimeter for ultra-high dose rate dosimetry. Furthermore, in the bunker of the modified Elekta linear accelerator, a Surface Guided Radiotherapy (SGRT) system is accessible. The Catalyst™ system (C-Rad Positioning, Uppsala, Sweden) provides optical surface imaging for patient setup, real-time motion monitoring and breathing adapted treatment. Aiming at treating patients using ultra-high dose rates, a real-time validation of the alignment between the beam and the target is crucial as the dose is delivered in a fraction of a second. Our research group has during the last decade investigated and developed SGRT workflows which improved patient setup and breathing adapted treatment for several cancer patient groups. Recently, we also started investigating the feasibility of a real-time motion monitoring system for surface guided FLASH-RT. Both FLASH related studies; 3D polymer gel dosimetry and surface guided FLASH-RT are to our knowledge the first of their kind. Following an introduction to the field of FLASH and the associated dosimetric challenges, we here aim to present the two ongoing studies including some preliminary results.
The role of standards laboratories in reducing uncertainty in clinical dosimetry: A Canadian perspective
Authors: Renaud J , Muir B , McEwen M 
Published: November 2023

Abstract
As a National Metrology Institute, the National Research Council Canada (NRC) provides confidence in measurement results, and data traceable to SI units. This paper outlines some of the ways that the NRC contributes to reducing measurement uncertainty in clinical medical physics dosimetry. These activities include, (i) the improvement of existing primary standards and traceability for established beam modalities, such as MV photon and electron beams; (ii) improving measurement accuracy for new beam modalities through the development of transportable systems which permit operation at the user’s facility; (iii) contributing to new dosimetry protocols, best practice reports and educational outreach; and (iv) supporting the verification of clinical implementation by offering dosimetry auditing capabilities through coordination with the clinical medical physics community.
Optimization of MRI pulse sequences and gadobutrol-doped polymer gel for real time 4D radiation dosimetry on the MRI-Linac
Authors: Deene Yves De , Mason Daniel 
Published: November 2023

Abstract
Different MRI pulse sequences can be applied to acquire real time dose distributions on an MRI-Linac. The temporal resolution is affected by the MRI pulse sequence type, the MRI pulse sequence parameters and the NMR relaxation-dose response of the polymer gel. To obtain a sufficiently high temporal resolution, it is crucial to optimize the MRI pulse sequence parameters such as TE, TR and flip angle. The optimization goal is to obtain the highest dose resolution within the shortest time frame, i.e. the smallest temporal uncertainty. We here also demonstrate that it is possible to further improve the temporal uncertainty of the polymer gel dosimeter by adding an MRI contrast agent. The optimization of two MRI pulse sequences in combination with a gadobutrol-doped MAGAT polymer gel dosimeter is discussed.
Spatial and Dosimetric accuracy of 3D polymer gel with CBCT readout - Varian HyperArc® SRS implementation
Authors: Kunkyab Tenzin , Hilts Michelle , Jirasek Andrew , Hyde Derek 
Published: November 2023

Abstract
3D polymer gel dosimetry is a promising means to verify complex radiation treatments such as stereotactic radiosurgery (SRS), as it provides both 3D dosimetric and spatial information. The purpose of the study is to use a polymer gel read-out with cone-beam computed tomography (CBCT) to commission Varian’s HyperArc®-treatment planning and delivery. Three targets (3 cm, 2 cm, 1 cm diameter respectively) were defined on a treatment plan with a maximum dose of 25 Gy, resembling a single isocentre, multiple-lesion SRS plan. Pre- and post-irradiation CBCT images of the gel were obtained for dosimetry analysis. One slice containing two large targets was used to self-calibrate the entire gel volume for dose comparison. We were able to achieve sub-millimeter spatial accuracy and all evaluated gamma criterion (5% 1mm, 3% 1mm, 2% 1 mm were > 95%). In summary, in this study we have demonstrated that CBCT polymer gel dosimetry can be a highly valuable tool for commissioning complex radiation treatment techniques such as SRS.
Modified optical computed tomography scanner for low temperature scanning
Authors: Woolvett Nathaniel , Jordan Kevin 
Published: November 2023

Abstract
Large radiochromic hydrogels, such as ferrous xylenol formulations require several hours to warm from the storage temperature of 278 K to 293 K for optical CT scanning and irradiation. This warm-up time can be avoided if gels are scanned at 278 K, resulting in a more practical 3D dose measurement. In this study a Vista 16 optical CT scanner was modified to allow scanning at 278 K, below the temperature where condensation forms on the aquarium windows. The refractive index matching liquid was first cooled to 276K in order to cool the aquarium as it was filled. The modification involved pumping cool, dry air into the aquarium scanner compartment to provide a positive pressure, preventing condensation on the aquarium windows. A warming rate of 2 K per hour was achieved with passive cooling which relied on the liquid-filled aquarium’s thermal mass. The radiochromic reaction rate decreased with temperature, requiring an increased post-irradiation wait time from 1 hour at 293 K to 1.5 hours at 278 K. In addition, initial sample transmission was greater by avoiding the auto-darkening that occurred as the samples were warmed from 278 K to 293 K over several hours. This increase in transmission resulted in a larger dynamic range for the dosimeter system.
Proof-of-concept of proton and photon measurements for large-area 2D dosimeters utilising optically stimulated luminescence
Authors: Nyemann Jacob S. , Jensen Mads L. , Valdetaro Lia B. , Jensen Morten B. , Turtos Rosana M. , Julsgaard Brian , Petersen Jørgen B. B. , Muren Ludvig P. , Balling Peter 
Published: November 2023

Abstract
Reusable high-resolution 2D dosimeters have a great potential for radiotherapy verification and quality assurance, not least due to the reduced cost and simpler calibration procedures implied by reusability. We have performed proof-of-concept measurements in both photon and proton beams with a reusable 2D dosimeter (5×7 cm2; 1 mm thickness) based on optically stimulated luminescence, using a readout setup scalable to 3D. Our data indicated a strong linear-energy-transfer quenching for this type of dosimeter.
Optimizing the transparency of nano-LiF:Cu/silicone nanocomposites for 3D optically stimulated luminescence dosimetry
Authors: Nielsen Camilla L , Turtos Rosana M , Julsgaard Brian , Muren Ludvig P , Balling Peter 
Published: November 2023

Abstract
Nanoparticles displaying optically stimulated luminescence embedded in a transparent polymer matrix have been proposed as a reusable high-spatial resolution 3D dosimeter. We measured the refractive indices of LiF:Cu nanoparticles and silicone and found a mismatch of 0.03-0.05 for the relevant wavelengths, explaining the transmission loss through 1 cm-sized nanocomposite dosimeters. We propose to bridge the refractive index gap by coating the LiF nanoparticles with a shell of SiO2. Initial studies show successful SiO2 growth, although more work is required to produce core-shell nanoparticles with an optimized refractive index.
Bare spherical gel dosimeter with optical computed tomography scanning
Authors: Moluchi Olivia , Mulligan Matt , Jordan Kevin 
Published: November 2023

Abstract
Radiochromic polyvinyl alcohol-iodide (PVA-I) hydrogel dosimeter with crosslinking by glutaraldehyde (GTA) has been reported. Because of the transparent gel’s mechanical strength, a study to cast samples in spherical shapes was initiated. The bare sample, 47 mm in diameter was mounted on a funnel and held by suction in a custom, 96 mm diameter, cylindrical vessel for 3D optical CT scanning. A solution of the same formulation without GTA provided refractive index matching inside the vessel for optic scanning and eliminated concentration gradients. The gel sphere remained in the vessel after draining the solution for the ‘in-air’ irradiation. A 20 Gy, maximum dose to the gel sphere was delivered by a single, 6 MV, x-ray beam. Comparison of central axis depth doses for the gel reconstruction and Monte Carlo calculation revealed similar results, indicating accurate 3D dosimetry within 1 mm of the gel surface will be possible. The gel recorded slightly greater dose in build-up region and slightly lower dose in the exit hemisphere relative to the calculation.
Lung radiotherapy verification with a 3D printed thorax phantom and an ionisation chamber array
Authors: Kairn T. , Jessen L. , Bodnar J. , Charles P. H. , Crowe S.B. 
Published: November 2023

AbstractIn this study, a 3D printing error inspired the development of a novel method for using a sagittally-sliced 3D printed thorax phantom to perform dosimetric verifications of lung radiotherapy treatment methods using a 2D ionization chamber array. A full-size thorax model was designed for 3D printing with multiple tissue densities including lung and bone and printed as a series of 2.4 cm sagittal slices using a Raise 3D Pro dual nozzle printer (Raise 3D Technologies Inc, Irvine, USA). An error introduced midway through printing resulted in one half of the phantom being printed at unrealistically high densities. A method was therefore devised whereby the entire phantom was used to plan two lung treatments, one conventionally fractionated and one hypo-fractionated, which were then verified via measurements using an Octavius 729 ionisation chamber array (PTW-Freiburg GmbH, Freiburg, Germany) in combination with several correctly-printed slices of the phantom. The measurements allowed dose distributions in planes through the target, adjacent to the target and at the location key of organs at risk to be verified, for both treatment plans. This method has the potential to be adapted for use with other phantoms and other dosimetry arrays to allow efficient evaluation of future treatment techniques.
On the comparison of two NIPAM gel dosimeters with high resolution 3D MRI sequences
Authors: Cinq-Mars M , Jutras J-D , Beaulieu L 
Published: November 2023

Abstract
Polymer gel dosimeters allow the measurement of a dose distribution in 3 dimensions. Irradiation induces polymerization reactions in the long chains of the gel molecules, which is characterized by a change in the transverse relaxation time T2. Gel dosimetry is mainly advantageous for its high resolution, but can also be expensive. The main goal of this project is to compare two normoxic polymer gel recipes made with NIPAM as monomer. The analysis is based on the quality of the images obtained for a fixed MRI scan time and a comparative cost of analysis of each 1L phantom. The ΔT2 maps are obtained by scanning the gels before and after irradiation with 3D sequences and the DESPOT2 technique is used to reconstruct the T2 maps. The phantoms were irradiated with 8 photon beams of 6 MV with a fixed 250 MU, 4 at two opposite sides of the jar (AP-PA configuration), to obtain 4 dose distributions of 4.7 Gy, 8.9 Gy, 13.2 Gy and 17.3 Gy. The SNR is then determined in the ΔT2 maps in function of the dose step and the concentration of NIPAM in the phantom. The first gel phantom is made with 15% NIPAM and has a total cost of $1561.65, including products and MRI scan costs. The SNR obtained for the 4 dose steps are 10.02, 31.18, 45.12 and 37.54. The contrast between the T2 before and after the irradiation in the 4 regions of dose are 0.45, 0.66, 0.78 and 0.85. The second phantom contained 5% NIPAM, cost 1186.85$ and the SNR obtained are 16.80, 27.08, 30.11 and 26.17 and the ΔT2 are of 0.61, 0.75, 0.79 and 0.77 for the 4 dose steps respectively. The comparison of the two recipes has shown that the increase of NIPAM concentration does not allow a significant increase in image quality for MRI. The recipe with 5% of NIPAM has a lower dynamic range but a better sensitivity at lower dose and is less expensive than the one with 15% of NIPAM. The results also show that by increasing the NIPAM concentration 3-fold, the cost of a 1L phantom increases by 30%.
Characterization of a water-based liquid scintillator for use in megavoltage radiotherapy beams
Authors: Bernier-Marceau D. , Cloutier É. , Yeh M. , Gann G. D Orebi , Beaulieu L. 
Published: November 2023

Abstract
The measurement of the dose delivered in radiotherapy treatments is carried out using dosimeters that are often expensive to produce and sometimes toxic to humans and the environment, which leads to more complex and rigorous clinical manipulations. It is in this context that it is necessary to provide new types of scintillators that would no longer have these problems while having properties equivalent to those of human tissues. Thus, the following study presents the performance of a water-based liquid scintillator used at radiotherapy energies. The characteristics studied include the proportionality of the scintillation signal to the dose, the scintillation efficiency at two different energies as well as the identification of the Cherenkov portion of the signal for photon beams of 180 kVp, 6 MV as well as 18 MV. Spectral measurements of the scintillation solution and a solution of distilled water were acquired in order to isolate the contribution of the scintillation signal from the spectrum obtained, and then compared to a commercial scintillator, Ultima Gold. The signal exhibits a linear dose relationship with a correlation coefficient of 0.999 and lower scintillation efficiency than Ultima Gold.
Preliminary commissioning of a prototype solid tank optical CT scanner for 3D radiation dosimetry
Authors: Ogilvy A , Collins S , Guenter M , Huang D , Hare W , Hilts M , Jirasek A 
Published: November 2023

Abstract
Optical computed tomography (CT) is one of the leading modalities for imaging gel dosimeters. In previous research, it was shown that a design could significantly reduce the volume of the refractive index baths that are commonly found in optical CT systems. The proposed scanner has been manufactured and is in process of being commissioned. The rays refract through the system and their paths are estimated using a ray-tracing simulator. Reconstruction is preformed through algebraic reconstruction technique and iterated using the FISTA-TV algorithm. A Sylgard®184 edge phantom was created to commission the scanner’s spatial resolution. The scanner is capable of a 0.929 mm−1 spatial resolution, although the spatial resolution is highly dependent on the number of iterations, and method of processing the edge spread function.
An ultra-low power 10-bit, 50 MSps SAR ADC for multi-channel readout ASICs
Authors: Firlej Mirosław , Fiutowski Tomasz , Idzik Marek , Kulis Szymon , Moroń Jakub , Świentek Krzysztof 
Published: November 2023

Abstract
The design and measurement results of a fast, ultra-low power, small area 10-bit SAR ADC, developed for multi-channel readout systems, in particular for applications in particle physics experiments, are discussed. A prototype ASIC was designed and fabricated in 130 nm CMOS technology and a wide spectrum of static (INL<0.4 LSB, DNL<0.3 LSB) and dynamic (ENOB=9.45) measurements was performed to study and quantify the performance of ADC.
The ADC converts analogue signals with a sampling frequency up to 55 MHz and power consumption below 1 mW.
The ADC works asynchronously, so no external clock is required. The ADC Figure of Merit (FOM) at 50 MHz sampling frequency is 24 fJ/conv.-step, and is the lowest among the State of the Art designs with similar technology and specifications.