Research utilizing synchrotron radiation for radiotherapy applications is becoming increasingly complex as it pushes towards canine clinical trials [1]–[3]. Recently, several beamline developments at the Imaging and Medical Beamline (IMBL) have taken place towards supporting the forthcoming canine clinical trials. A high speed dynamic collimator has been developed and tested on IMBL for shaping the synchrotron beam as a target is moved through the beam. A 6-Axis Kuka robot has also been configured to allow a target to be positioned and treated with respect to the synchrotron beam. In this work, we describe the synchronisation of these two systems when combined to deliver conformal radiotherapy treatments on IMBL for large animals. A proof-of-concept treatment is demonstrated whereby a medical physics phantom (ball bearings encased in an acryllic cube) is aligned and treated with the robot and dynamic collimator. A full characterisation of the systems capabilities is to follow such that appropriate treatment margins can be generated when using this configuration. More importantly, the ability to dynamically deliver conformal fields on the synchrotron beamline for large animals will ensure that the canine clinical trails can utilise conformal fields for the treatment of cancers whilst avoiding nearby critical structures.

In this work, a new image guidance system and protocols for delivering image-guided radiotherapy (IGRT) on the Imaging and Medical Beamline (IMBL) at the ANSTO Australian Synchrotron are introduced. The image guidance methods used and the resulting accuracy of tumour alignment in in vivo experiments are often under-reported. Image guidance tasks are often complex, time-consuming and prone to errors. If unchecked, they may result in potential mis-treatments. We introduce SyncMRT, a software package that provides a simple, image guidance tool-kit for aligning samples to the synchrotron beam. We have demonstrated sub-millimetre alignment using SyncMRT and the small-animal irradiation platform (the DynamicMRT system) on the IMBL. SyncMRT has become the standard for carrying out IGRT treatments on the IMBL and has been used in all pre-clinical radiotherapy experiments since 2017. Further, we introduce two quality assurance (QA) protocols to synchrotron radiotherapy on the IMBL: the Winston-Lutz test and hidden target test. It is shown that the presented QA tests are appropriate for picking up geometrical setup errors and assessing the end-to-end accuracy of the image guidance process. Together, these tools make image guidance easier and provide a mechanism for reporting the geometric accuracy of synchrotron-based IGRT treatments. Importantly, this work is scalable to other delivery systems, and is in continual development to support the upcoming veterinary radiotherapy trials on the IMBL.

Breast microcalcifications are an important primary radiological indicator of breast cancer. However, microcalcification classification and diagnosis may be still challenging for radiologists due to limitations of the standard 2D mammography technique, including spatial and contrast resolution. In this study, we propose an approach to improve the detection of microcalcifications in propagation-based phase-contrast X-ray computed tomography of breast tissues. Five fresh mastectomies containing microcalcifications were scanned at different X-ray energies and radiation doses using synchrotron radiation. Both bright-field (i.e. conventional phase-retrieved images) and dark-field images were extracted from the same data sets using different image processing methods. A quantitative analysis was performed in terms of visibility and contrast-to-noise ratio of microcalcifications. The results show that while the signal-to-noise and the contrast-to-noise ratios are lower, the visibility of the microcalcifications is more than two times higher in the dark-field images compared to the bright-field images. Dark-field images have also provided more accurate information about the size and shape of the microcalcifications.

Laminitis is an extremely painful and debilitating condition of horses that can affect their athletic ability and even quality of life. The current gold standard for assessment of laminar tissue is histology, which is the only modality that enables detailed visualization of the lamina. Histology requires dissection of the hoof and therefore can only represent one specific time point. The superior spatial and contrast resolution of synchrotron computed tomography (sCT), when compared with readily available imaging modalities, such as radiographs and conventional CT, provides an opportunity for detailed studies of the lamina without the need for hoof dissection and histological assessment. If the resolution of histology can be matched or even approached, dynamic events, such as laminar blood flow, could also be studied on the microscopic tissue level. To investigate this possible application of sCT further, two objectives are presented: (i) to develop a protocol for sCT of an equine digit using cadaver limbs and (ii) to apply the imaging protocol established during (i) for sCT imaging of the vasculature within the foot using an ex vivo perfusion system to deliver the vascular contrast. The hypotheses were that sCT would allow sufficient resolution for detailed visualization to the level of the secondary lamellae and associated capillaries within the equine digit. Synchrotron CT enabled good visualization of the primary lamellae (average length 3.6 mm) and the ex vivo perfusion system was able to deliver vascular contrast agent to the vessels of the lamina. The individual secondary lamellae (average length 0.142 mm) could not be seen in detail, although differentiation between primary and secondary lamellae was achieved. This approaches, but does not yet reach, the current gold standard, histology, for assessment of the lamellae; however, with further refinement of this imaging technique, improved resolution may be accomplished in future studies.

Experimental measurement of Synchrotron Radiotherapy (SyncRT) doses is challenging, especially for Microbeam Radiotherapy (MRT), which is characterised by very high dynamic ranges with spatial resolutions on the micrometer scale. Monte Carlo (MC) simulation is considered a gold standard for accurate dose calculation in radiotherapy, and is therefore routinely relied upon to produce verification data. We present a MC model for Australian Synchrotron's Imaging and Medical Beamline (IMBL), which is capable of generating accurate dosimetry data to inform and/or verify SyncRT experiments. Our MC model showed excellent agreement with dosimetric measurement for Synchrotron Broadbeam Radiotherapy (SBBR). Our MC model is also the first to achieve validation for MRT, using two methods of dosimetry, to within clinical tol-erances of 5% for a 20 x 20 mm(2) field size, except for surface measurements at 5 mm depth, which remained to within good agreement of 7.5%. Our experimental methodology has allowed us to control measurement uncertainties for MRT doses to within 5-6%, which has also not been previously achieved, and provides a confidence which until now has been lacking in MRT validation studies. The MC model is suitable for SyncRT dose calculation of clinically relevant field sizes at the IMBL, and can be extended to include medical beamlines at other Synchrotron facilities as well. The presented MC model will be used as a validation tool for treatment planning dose calculation algorithms, and is an important step towards veterinary SyncRT trials at the Australian Synchrotron.

PURPOSE:Propagation-based phase-contrast computed tomography (PB-CT) is a method for three-dimensional x-ray imaging that utilizes refraction, as well as absorption, of x rays in the tissues to increase the signal-to-noise ratio (SNR) in the resultant images, in comparison with equivalent conventional absorption-only x-ray tomography (CT). Importantly, the higher SNR is achieved without sacrificing spatial resolution or increasing the radiation dose delivered to the imaged tissues. The present work has been carried out in the context of the current development of a breast CT imaging facility at the Australian Synchrotron.METHODS:Seven unfixed complete mastectomy samples with and without breast cancer lesions have been imaged using absorption-only CT and PB-CT techniques under controlled experimental conditions. The radiation doses delivered to the mastectomy samples during the scans were comparable to those approved for mammographic screening. Physical characteristics of the reconstructed images, such as spatial resolution and SNR, have been measured and compared with the results of the radiological quality assessment of the complete absorption CT and PB-CT image stacks.RESULTS:Despite the presence of some image artefacts, the PB-CT images have outperformed comparable absorption CT images collected at the same radiation dose, in terms of both the measured objective image characteristics and the radiological image scores. The outcomes of these experiments are shown to be consistent with predictions of the theory of PB-CT imaging and previous reported experimental studies of this imaging modality.CONCLUSIONS:The results presented in this paper demonstrate that PB-CT holds a high potential for improving on the quality and diagnostic value of images obtained using existing medical x-ray technologies, such as mammography and digital breast tomosynthesis (DBT). If implemented at suitable synchrotron imaging facilities, PB-CT can be used to complement existing imaging modalities, leading to more accurate breast cancer diagnosis.

Body: Breast MRI has numerous benefits for the newly diagnosed breast cancer patient.MRI is much better at lesion size determination and can find tumors occult to conventional imaging (mammography, ultrasound).MRI can be used to assess tumor extent and tumor involvement of surrounding structures, such as nipple, skin, pectoralis muscle, and chest wall.As such, staging of the ipsilateral breast is more accurate with breast MRI.In addition, contralateral malignancy is not uncommon in the newly diagnosed patient, so evaluation of the contralateral breast with MRI helps with appropriate treatment.Breast MRI is also an excellent way to assess neoadjuvant chemotherapy response.In spite of these benefits, breast MRI for newly diagnosed patients remains controversial in the U.S. The importance of defining the extent of disease will increase, especially in light of recent updates in tumor prognosticating factors in staging.In any case, certain populations are more likely to have occult disease.These can be viewed in three broad categories: 1) tumor biologypatients with invasive lobular carcinoma or aggressive lesions, like triple negative tumors or those that are HER2 positive; 2) patient characteristicsdense tissue or younger age; and 3) clinical scenariospatients with node positive disease or those with more discrepancy in tumor size on mammography and sonography.Focusing MRI on these populations might help optimize utilization.Learning Objectives: To understand the use of MRI in the newly diagnosed breast cancer patient; to understand the benefits and controversy of use of MRI in this patient populations; to identify populations who would benefit most from preoperative breast MRI.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

External beam rotational radiotherapy of breast cancer with kilovoltage photons (kV-EBRT), with the patient in prone position, has been proposed [ [1] Prionas N.D. et al. Kilovoltage rotational external beam radiotherapy on a breast computed tomography platform: a feasibility study. Int J Radiation Oncol Biol Phys. 2012; 84: 533-539 Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar ] as a possible alternative to conventional radiotherapy with two tangential 6-MV X-ray beams produced by a medical linac with a supine patient. kV-EBRT uses a dedicated setup initially developed for breast CT, with a 320-kVp beam from an orthovoltage X-ray tube rotating in full circles around the breast; CT for tumour localization can be performed by using the same setup. Though dose build-up is not present, rotational summation of dose delivery allows a skin sparing comparable to conventional radiotherapy. We proposed the use of a monoenergetic synchrotron radiation (SR) collimated beam for image-guided rotational radiotherapy for the pendant breast (SR3T) [ [2] Di Lillo F. et al. Towards breast cancer rotational radiotherapy with synchrotron radiation. Phys Med. 2017; 41: 20-25 Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar ]. The high flux of SR permits dose rates even greater to that of conventional radiotherapy, while the optimal photon energy can be selected for the treatment. In this work, we present Monte Carlo simulation and a simple model for evaluation of the 3D dose distribution in SR3T. The MC code was based on GEANT4 toolkit ver.10.00. We validated these simulations via measurements on breast phantoms performed at the Imaging and Medical Beamline of the Australian Synchrotron. We measured the dose distribution in cylindrical PMMA and polyethylene phantoms at 60 keV, using an ionization chamber, thermoluminescent dosimeters and radiochromic films. This study indicated that for a tumour localized at the centre of a mid-sized breast (14-cm diameter at chest wall), a ”skin-to-tumour” dose ratio of 14% can be reached at 60 keV with a collimated SR beam. Non uniform dose distribution to the target (dose painting) can be performed with multiple rotations around the organ. Kilovoltage SR3T with suitable radiosensitizers may exploit the dose enhancement factor due to increased photoelectric absorption, at SR beam energies in the 60–110 keV range. External beam rotational radiotherapy of breast cancer with kilovoltage photons (kV-EBRT), with the patient in prone position, has been proposed [ [1] Prionas N.D. et al. Kilovoltage rotational external beam radiotherapy on a breast computed tomography platform: a feasibility study. Int J Radiation Oncol Biol Phys. 2012; 84: 533-539 Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar ] as a possible alternative to conventional radiotherapy with two tangential 6-MV X-ray beams produced by a medical linac with a supine patient. kV-EBRT uses a dedicated setup initially developed for breast CT, with a 320-kVp beam from an orthovoltage X-ray tube rotating in full circles around the breast; CT for tumour localization can be performed by using the same setup. Though dose build-up is not present, rotational summation of dose delivery allows a skin sparing comparable to conventional radiotherapy. We proposed the use of a monoenergetic synchrotron radiation (SR) collimated beam for image-guided rotational radiotherapy for the pendant breast (SR3T) [ [2] Di Lillo F. et al. Towards breast cancer rotational radiotherapy with synchrotron radiation. Phys Med. 2017; 41: 20-25 Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar ]. The high flux of SR permits dose rates even greater to that of conventional radiotherapy, while the optimal photon energy can be selected for the treatment. In this work, we present Monte Carlo simulation and a simple model for evaluation of the 3D dose distribution in SR3T. The MC code was based on GEANT4 toolkit ver.10.00. We validated these simulations via measurements on breast phantoms performed at the Imaging and Medical Beamline of the Australian Synchrotron. We measured the dose distribution in cylindrical PMMA and polyethylene phantoms at 60 keV, using an ionization chamber, thermoluminescent dosimeters and radiochromic films. This study indicated that for a tumour localized at the centre of a mid-sized breast (14-cm diameter at chest wall), a ”skin-to-tumour” dose ratio of 14% can be reached at 60 keV with a collimated SR beam. Non uniform dose distribution to the target (dose painting) can be performed with multiple rotations around the organ. Kilovoltage SR3T with suitable radiosensitizers may exploit the dose enhancement factor due to increased photoelectric absorption, at SR beam energies in the 60–110 keV range.

Microbeam and minibeam radiation therapies (MRT and MBRT, respectively) are preclinical radiation therapy modalities being developed at several biomedical synchrotron beamlines and involve the collimation of synchrotron x-ray beams into an array of spatially fractionated quasiparallel beams. Spatial fractionation exploits the dose-volume effect, where the threshold dose for damage to normal tissues increases as the volume of irradiated tissue decreases. Very large doses of radiation can be delivered to a tumor while sparing surrounding normal tissues, thereby satisfying the clinical goal. A robust dosimetry protocol is at the core of quality assurance for any radiation therapy technique. The characteristics of synchrotron X rays that offer desirable outcomes for radiation therapy present significant challenges to dosimetric measurements. The narrow beam widths—typically 25-50 μm for MRT and 500-600 μm for MBRT—require a detector with submillimetric dimensions to accurately measure peak doses and scattered dose between the beams (valley). The detector should also exhibit tissue equivalence in kilovoltage x-ray spectra and have a linear response with dose rate. A synthetic single crystal diamond detector (SSCD) designed specifically for dosimetry in small fields has been studied to investigate its potential as a high-resolution dosimeter for quality assurance measurements in spatially fractionated synchrotron radiation therapy. The energy dependence was characterized for energies 30-120 keV by comparing the response of the detector to reference ionization chambers. The dose rate dependence was also studied over the range 1-700 Gy/s. High-resolution measurements of mini- and microbeam array profiles were performed and peak to valley dose ratio (PVDR) at various depths was calculated and compared to gafchromic film. The detector exhibited an energy response but this has been characterized and beam quality correction factors are now known. Over the dose rate range 1-700 Gy/s the response of the detector was independent of dose rate. Minibeam and microbeam array profiles showed less noise than film profiles, and PVDRs calculated from the diamond detector and film were in agreement. The diamond detector studied is a promising candidate to be used in a dosimetry protocol for spatially fractionated synchrotron radiation therapy.

The Australian Synchrotron Imaging and Medical Beam Line (IMBL) began phased commissioning in late 2008 and was opened for Users this year (November, 2012). It will provide Australia with an unrivaled facility for x-ray imaging and radiotherapy research covering a wide range of applications in disease studies, treatments, and revealing physiological processes. The clinical research drivers for IMBL rely on the facility's ability to support high spatial and contrast resolution imaging.The wide variety of demands for x-ray imaging with IMBL cannot be covered with any single detector system. A list of six detector categories was drawn up after assessing the techniques that are most likely to be used during our first years of operation. Detectors in this list will cover the fields of view, resolutions (both spatial and contrast), and frame rates required for a majority of the experiments. We present the six detectors within these categories. One detector system is the topic of a development project with the goal of producing a large field of view high aspect ratio system. Some initial design ideas are presented.

The Australian Synchrotron Imaging and Medical Beam Line (IMBL) began phased commissioning in late 2008 and was opened for Users this year (November, 2012). It will provide Australia with an unrivaled facility for x-ray imaging and radiotherapy research covering a wide range of applications in disease studies, treatments, and revealing physiological processes. The clinical research drivers for IMBL rely on the facility’s ability to support high spatial and contrast resolution imaging. The wide variety of demands for x-ray imaging with IMBL cannot be covered with any single detector system. A list of six detector categories was drawn up after assessing the techniques that are most likely to be used during our first years of operation. Detectors in this list will cover the fields of view, resolutions (both spatial and contrast), and frame rates required for a majority of the experiments. We present the six detectors within these categories. One detector system is the topic of a development project with the goal of producing a large field of view high aspect ratio system. Some initial design ideas are presented.

The effects of uniaxial stress on the pressure-induced α→ω transition in pure titanium (Ti) are investigated by means of angle dispersive X-ray diffraction in a diamond-anvil cell. Experiments under four different pressure environments reveal that: (1) the onset of the transition depends on the pressure medium used, going from 4.9GPa (no pressure medium) to 10.5GPa (argon pressure medium); (2) the α and ω phases coexist over a rather large pressure range, which depends on the pressure medium employed; (3) the hysteresis and quenchability of the ω phase is affected by differences in the sample pressure environment; and (4) a short-term laser heating of Ti lowers the α→ω transition pressure. Possible transition mechanisms are discussed in the light of the present results, which clearly demonstrate the influence of uniaxial stress in the α→ω transition.

Rietveld refinement of monochromatic synchrotron x‐ray powder diffraction data was used to study the evolution of octahedral tilting in the orthorhombic NaMgF 3 perovskite under pressure. Hydrostatic pressure conditions were ensured up to 16 GPa using helium as a pressure medium. The tilting angles of MgF 6 octahedral framework were observed to increase with increasing pressure. The compression mechanism was observed to be dominated by the shortening of the octahedral Mg‐F bond below 6 GPa, and then controlled by the increase of the octahedral tilting above 12 GPa. The bulk modulus of NaMgF 3 was estimated as 76.0 ± 1.1 GPa. A phase transition was observed at about 19.4 GPa in a separate run when silicone oil was used as pressure medium, and this high‐pressure phase could be rationalized in term of a post‐perovskite structural model.

We present evidence for an isostructural, first-order Mott transition in MnO at 105+/-5 GPa, based on high-resolution x-ray emission spectroscopy and angle-resolved x-ray diffraction data. The pressure-induced structural and spectral changes provide a coherent picture of MnO phase transitions from paramagnetic B1 to antiferromagnetic distorted B1 at 30 GPa, to paramagnetic B8 at 90 GPa, and to diamagnetic B8 at 105+/-5 GPa. The last is the Mott transition, accompanied by a significant loss of magnetic moment, an approximately 6.6% volume collapse and the insulator-metal transition as demonstrated by recent resistance measurements.

Introduction Structural transformations in titanium have received a great deal of experimental and theoretical attention. Under pressure, titanium transforms from the hexagonal-closedpacked (hcp) structure to the high-pressure omega phase. This phase transition from hcp (α) to omega (ω) is martensitic. Martensitic transformations are abundant in the nature and have tremendous scientific and technological interest. In particular, the pressure-induced martensitic α → ω transformation in pure titanium (Ti) has significant implications in the aerospace industry because the ω phase formation affects the toughness and ductility of Ti. The occurrence of the pressure-driven α → ω transformation was first observed by Jamieson [13] and has since been studied extensively. Room temperature (RT) high-pressure studies of the α → ω transition show a large hysteresis, with the high-pressure ω phase being retained after pressure is released [2, 3]. The onset of the transition has been observed over a wide range of pressures from 2.9 GPa [4] to 11 GPa [5]. One of the factors that could be responsible for this scatter in the observed transition pressure (Pα→ω) is possibly the variation in the non-hydrostatic conditions in different experiments. However, the combined results from different experiments are inconsistent with this fact. Then the question is whether the shear stress explanation is correct and whether other factors play a role in the transition. To answer this question, we conducted a series of experiments in a diamond-anvil cell (DAC) using different pressure media. In this study, we examined the effects of uniaxial stresses on the α → ω transition of Ti using synchrotron xray powder diffraction. Experiments were performed using a DAC and four different pressure media, which provided different hydrostatic conditions. We clearly demonstrated that the presence of uniaxial stresses has a significant effect on the structural stability of Ti. We also observed that shortterm laser-heating of Ti lowers Pα→ω.

Introduction Structural transformations in titanium have received a great deal of experimental and theoretical attention. Under pressure, titanium transforms from the hexagonal-closedpacked (hcp) structure to the high-pressure omega phase. This phase transition from hcp (α) to omega (ω) is martensitic. Martensitic transformations are abundant in the nature and have tremendous scientific and technological interest. In particular, the pressure-induced martensitic α → ω transformation in pure titanium (Ti) has significant implications in the aerospace industry because the ω phase formation affects the toughness and ductility of Ti. The occurrence of the pressure-driven α → ω transformation was first observed by Jamieson [13] and has since been studied extensively. Room temperature (RT) high-pressure studies of the α → ω transition show a large hysteresis, with the high-pressure ω phase being retained after pressure is released [2, 3]. The onset of the transition has been observed over a wide range of pressures from 2.9 GPa [4] to 11 GPa [5]. One of the factors that could be responsible for this scatter in the observed transition pressure (Pα→ω) is possibly the variation in the non-hydrostatic conditions in different experiments. However, the combined results from different experiments are inconsistent with this fact. Then the question is whether the shear stress explanation is correct and whether other factors play a role in the transition. To answer this question, we conducted a series of experiments in a diamond-anvil cell (DAC) using different pressure media. In this study, we examined the effects of uniaxial stresses on the α → ω transition of Ti using synchrotron xray powder diffraction. Experiments were performed using a DAC and four different pressure media, which provided different hydrostatic conditions. We clearly demonstrated that the presence of uniaxial stresses has a significant effect on the structural stability of Ti. We also observed that shortterm laser-heating of Ti lowers Pα→ω.