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Engineering systems continuously interact with nano-sized particles coming from natural or artificial sources. Considering nano-sized contaminants the detrimental effects are known as soiling and fouling phenomena. The objective of the present work is to gather morphological and three-dimensional quantitative information of discontinuities such as voids and pores within the nano-sized particle layer and in correspondence to the substrate/layer interface using microtomography. Deposits are obtained through impact tests using fine powder (soil and soot), and there are realized on a low-density material substrate characterized by different surface roughness values. The packing process and the discontinuities at the substrate-to-layer interfaces explain macroscopic effects as detachment and spallation but at the same time, give the possibility to understand more in detail the process related to the deposition mechanisms involved in this type of test defining general guidelines to predict the fouling phenomenon and to improve the capability of the removal process.

By means of a combined microscopy-, spectroscopy-, and tomography-based approach, we investigated surface and interface defects in metal-polymer heterostacks. The aim was to characterize both morphological and compositional alterations of the surfaces, originating in the physical vapor deposition (PVD) growth methods adopted in the fabrication process. Synchrotron radiation X-ray computed tomography (CT) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray Spectroscopy (EDS) indicate that both chemical contaminations, introduced in the fabrication process, and growth conditions strongly affect the presence of defects. On the basis of our results, we classified the defects into four main families. Interestingly, the faults are mainly located at the metal-polymer interface. Thanks to this study, we have been able to gain a deeper insight into the defects' origins and nature, allowing the identification of the precise production steps involved in the generation of the selected defects.

Recent trends in hard X-ray micro-computed tomography (microCT) aim at increasing both spatial and temporal resolutions. These challenges require intense photon beams. Filtered synchrotron radiation beams, also referred to as `pink beams', which are emitted by wigglers or bending magnets, meet this need, owing to their broad energy range. In this work, the new microCT station installed at the biomedical beamline ID17 of the European Synchrotron is described and an overview of the preliminary results obtained for different biomedical-imaging applications is given. This new instrument expands the capabilities of the beamline towards sub-micrometre voxel size scale and simultaneous multi-resolution imaging. The current setup allows the acquisition of tomographic datasets more than one order of magnitude faster than with a monochromatic beam configuration.

Collagen is one of the main components of the extracellular matrix (ECM), involved, among all, in the maintenance of the structural support of tissues. In fibrotic diseases, collagen is overexpressed, and its production determines the formation of a significantly stiffer ECM. The cross-linking of high-resolution analytical tools, able to investigate both the tridimensional organization and the secondary structure of collagen in fibrotic diseases, could be useful to identify defined markers correlating the status of this protein with specific pathological conditions. To this purpose, an innovative multidisciplinary approach based on Phase-Contrast MicroComputed Tomography, Transmission Electron Microscopy, and Fourier Transform Infrared Imaging Spectroscopy was exploited on leiomyoma samples and adjacent myometrium to characterize microstructural collagen features. Uterine leiomyoma is a common gynecological disorder affecting women in fertile age. It is characterized by a massive collagen production due to the repairing processes occurring at myometrium level, and, hence, it represents a valuable model to investigate collagen self-organization in a pathological condition. Moreover, to evaluate the sensitivity of this multidisciplinary approach, the effects of eicosapentaenoic (EPA) and docosahexaenoic (DHA) omega-3 fatty acids in collagen reduction were also investigated.

Objective: Our goal is to evaluate the effects of heat and ultraviolet (UV) irradiation on P3 facial respirator microstructure. Intervention: P3 facial filters were exposed to dry heat and UV sterilization procedures. Methods: P3 facial filter samples underwent a standardized sterilization process based on dry heat and UV irradiation techniques. We analyzed critical parameters of internal microstructure, such as fiber thickness and porosity, before and after sterilization, using 3D data obtained with synchrotron radiation-based X-ray computed microtomography (micro-CT). The analyzed filter has two inner layers called the “finer” and “coarser” layers. The “finer” layer consists of a dense fiber network, while the “coarser” layer has a less compact fiber network. Results: Analysis of 3D images showed no statistically significant differences between the P3 filter of the controls and the dry heat/UV sterilized samples. In particular, averages fiber thickness in the finer layer of the control and the 60° dry heated and UV-irradiated sample groups was almost identical. Average fiber thickness for the coarser layer of the control and the 60° dry heated and UV-irradiated sample groups was very similar, measuring 19.33 µm (±0.47), 18.33 µm (±0.47), and 18.66 µm (±0.47), respectively. There was no substantial difference in maximum fiber thickness in the finer layers and coarser layers. For the control group samples, maximum thickness was on average 11.43 µm (±1.24) in the finer layer and 59.33 µm (±6.79) in the coarser layer. Similarly, the 60° dry heated group samples were thickened 12.2 µm (±0.21) in the finer layer and 57.33 µm (±1.24) in the coarser layer, while for the UV-irradiated group, the mean max thickness was 12.23 µm (±0.90) in the finer layer and 58.00 µm (±6.68) in the coarser layer. Theoretical porosity analysis resulted in 74% and 88% for the finer and coarser layers. The finer layers’ theoretical porosity tended to decrease in dry heat and UV-irradiated samples compared with the respective control samples. Conclusions: Dry heat and UV sterilization processes do not substantially alter the morphometry of the P3 filter samples’ internal microstructure, as studied with micro-CT. The current study suggests that safe P3 filter facepiece reusability is theoretically feasible and should be further investigated.

Purpose: The SYRMA-3D collaboration is setting up a breast computed tomography (bCT) clinical program at the Elettra synchrotron radiation facility in Trieste, Italy. Unlike the few dedicated scanners available at hospitals, synchrotron radiation bCT requires the patient's rotation, which in turn implies a long scan duration (from tens of seconds to few minutes). At the same time, it allows the achievement of high spatial resolution. These features make synchrotron radiation bCT prone to motion artifacts. This article aims at assessing and compensating for motion artifacts through an optical tracking approach. Methods: In this study, patients’ movements due to breathing have been first assessed on seven volunteers and then simulated during the CT scans of a breast phantom and a surgical specimen, by adding a periodic oscillatory motion (constant speed, 1 mm amplitude, 12 cycles/minute). CT scans were carried out at 28 keV with a mean glandular dose of 5 mGy. Motion artifacts were evaluated and a correction algorithm based on the optical tracking of fiducial marks was introduced. A quantitative analysis based on the structural similarity (SSIM) index and the normalized mean square error (nMSE) was performed on the reconstructed CT images. Results: CT images reconstructed through the optical tracking procedure were found to be as good as the motionless reference image. Moreover, the analysis of SSIM and nMSE demonstrated that an uncorrected motion of the order of the system's point spread function (around 0.1 mm in the present case) can be tolerated. Conclusions: Results suggest that a motion correction procedure based on an optical tracking system would be beneficial in synchrotron radiation bCT.

Here we present the specifications and capabilities of the SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline of the Italian Synchrotron “Elettra” in Trieste. SYRMEP was designed to provide X-ray imaging in an energy range that fits both biomedical research and clinical applications on patients. Additionally, SYRMEP covers a spatial resolution range of 100 μm down to 1 μm (1/50th the width of a human hair) with a comparably wide field-of-view (FOV), which enables studies in large specimens and therefore closes the gap between micro computed tomography (CT) in biomedical research and clinical CT imaging. Moreover, the possible long sample-to-detector distance allows for an effective use of free-propagation phase contrast that increases dose efficacy and soft-tissue contrast. These parameters and their function are further discussed on a set of examples of biomedical applications.

Objective: We sought to evaluate the effects of heating and UltraViolet (UV) sterilization on level 3 protection microstructure (P3) used on disposable filtering facepieces.Intervention: P3 facial filter has been exposed to dry heat and UV sterilization procedures.Methods: P3 facial filter samples underwent standardized sterilisation processes based on dry heat and UV irradiation techniques. We analysed key parameters of internal microstructure, such as fibres thickness and porosity, before and after sterilization using 3D data obtained with a synchrotron radiation based X-ray computed microtomography (Micro-CT). The analyzed filter has two inner layers that we called "finer" and "coarser" layers. The "finer" layer consists of a dense fibers network while the "coarser" layer has a less compact fiber network. Results: Analysis on 3D images showed no statistically significant differences between P3 Filter of Controls and dry heat/UV sterilized samples. In particular, averages fibres thickness in the finer layer of Controls, 60° dry heated and UV irradiated samples group was almost identical for each group. Average fibres thickness for coarser layer of Controls, 60° dry heated and UV irradiated samples group was very similar measuring 19.33 µm (±0.47), 18.33 µm (±0.47) and 18.66 µm (±0.47), respectively. Of note, there was no substantial difference in fibres maximum thickness in the finer layers and coarser layers. For Controls group samples maximum thickness was on average of 11.43 µm (±1.24) in the finer layer and 59.33 µm (±6.79) in the coarser layer. Similarly, 60° dry heated group samples were thickened 12.2 µm (±0.21) in the finer layer and 57.33 µm (±1.24) in the coarser layer, while UV irradiated samples group the mean max thickness is 12.23 µm (±0.90) in the finer layer and 58.00 µm (±6.68) in the coarser layer.Theoretical porosity analysis resulted of 74% and 88%, for finer and coarser layer, respectively. Theoretical porosity of finer layers tend to decrease on dry heat and UV irradiated samples when compared with the respective controls samples.Conclusions: Dry heat and UV sterilization processes do not substantially alter morphometry of the internal microstructure of the P3 filter samples studied with Micro-CT. The current study suggests that safe P3 filter facepiece reusability is theoretically feasible and should be further investigated.

Item does not contain fulltext Breast computed tomography (BCT) is an emerging application of X-ray tomography in radiological practice. A few clinical prototypes are under evaluation in hospitals and new systems are under development aiming at improving spatial and contrast resolution and reducing delivered dose. At the same time, synchrotron-radiation phase-contrast mammography has been demonstrated to offer substantial advantages when compared with conventional mammography. At Elettra, the Italian synchrotron radiation facility, a clinical program of phase-contrast BCT based on the free-space propagation approach is under development. In this paper, full-volume breast samples imaged with a beam energy of 32 keV delivering a mean glandular dose of 5 mGy are presented. The whole acquisition setup mimics a clinical study in order to evaluate its feasibility in terms of acquisition time and image quality. Acquisitions are performed using a high-resolution CdTe photon-counting detector and the projection data are processed via a phase-retrieval algorithm. Tomographic reconstructions are compared with conventional mammographic images acquired prior to surgery and with histologic examinations. Results indicate that BCT with monochromatic beam and free-space propagation phase-contrast imaging provide relevant three-dimensional insights of breast morphology at clinically acceptable doses and scan times.

In this work, we evaluated the performance of the prototype SFOV MediPROBE developed at the University of Naples Federico II through the protocol proposed by (Bhatia B.S., Bugby S.L., Lees J.E., Perkins A.C. A scheme for assessing the performance characteristics of a small field of-view gamma cameras. Physica. Medica., 31 (1), pp. 98-103. (2015) doi: 10.1016/j.ejmp.2014.08.004). We extensively investigated a new device configuration where the pinhole collimator was placed outside the housing of the probe, in order to increase the system spatial resolution, and the pixel size was doubled, in order to reduce the charge sharing effect. The experimental measurements show that the spatial resolution is enhanced by only about 10%, but the sensitivity decreases strongly. Therefore, the trade-off between these two features does not seem to be advantageous. In addition, our experiments suggest that the charge sharing effect is not completely canceled. Despite these results, the features of this device appear suitable for intraoperative surgical survey. We aim to use this device in the clinical practice for the intraoperative imaging of lymph nodes, breast, thyroid and parathyroid tumors.

Introduction Rotational kilovoltage external beam radiotherapy (kV-EBRT) for breast cancer with orthovoltage tubes was recently proposed by a team at University of California at Davis, as an alternative to the typical 6-MV photon beams with breast tangential fields produced by a clinical accelerator. On this scientific basis, we propose to implement EBRT in breast cancer therapy, using a monochromatic synchrotron radiation (SR) beam and dedicated setup for irradiating the pendant breast (SR-EBRT). The same platform could be adopted to perform a computer tomography dedicated to the breast for tumor 3D localization and beam centering. Purpose To investigate, with a feasibility study in a breast phantom, the proposed technique SR-EBRT. Materials and methods The experimental plan includes dose distribution measurements with TLDs, radiochromic films and ionization chambers in cylindrical PMMA phantoms at ESRF and at the Australian Synchrotron. Results The use of the high-flux SR beam will permit dose delivery times comparable to the one of conventional radiotherapy. Preliminary data indicated that a 7:1–10:1 tumor-to-skin ratio from 60 keV to 180 keV could be achieved, and the possibility of realizing dose-painting by multiple rotations. Conclusion A SR beam down to 60 keV can be adopted for SR-EBRT of breast cancer with a skin sparing close to that of orthovoltage EBRT at 320 kVp. SR-EBRT at low energy (60–80 keV) might be coupled to gold nanoparticles injection for dose-enhanced breast SR-EBRT. Disclosure Nothing to declare.

It is shown that an extensive set of accurate ionization-chamber measurements with a primary polychromatic synchrotron X-ray beam transmitted through various filter combinations/thicknesses can be used to quite effectively estimate the absolute flux distribution. The basic technique is simple but the `inversion' of the raw data to extract the flux distribution is a fundamentally ill-posed problem. It is demonstrated, using data collected at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron, that the absolute flux can be quickly and reliably estimated if a suitable choice of filters is made. Results are presented as a function of the magnetic field (from 1.40 to 4.00 T) of the superconducting multi-pole wiggler insertion device installed at IMBL. A non-linear least-squares refinement of the data is used to estimate the incident flux distribution and then comparison is made with calculations from the programsSPECTRA,XOPandspec.exe. The technique described is important not only in estimating flux itself but also for a variety of other, derived, X-ray properties such as beam quality, power density and absorbed-dose rate. The applicability of the technique with a monochromatic X-ray beam for which there is significant harmonic contamination is also demonstrated. Whilst absolute results can also be derived in this monochromatic beam case, relative (integrated) flux values are sufficient for our primary aim of establishing reliable determinations of the percentages of the various harmonic components.

The aim of this work was to assess the performance of a prototype compact gamma camera (MediPROBE) based on a CdTe semiconductor hybrid pixel detector, for coded aperture imaging. This probe can be adopted for various tasks in nuclear medicine such as preoperative sentinel lymph node localization, breast imaging with 99mTc radiotracers and thyroid imaging, and in general in radioguided surgery tasks. The hybrid detector is an assembly of a 1-mm thick CdTe semiconductor detector bump-bonded to a photon-counting CMOS readout circuit of the Medipix2 series or energy-sensitive Timepix detector. MediPROBE was equipped with a set of two coded aperture masks with 0.07-mm or 0.08-mm diameter holes. We performed laboratory measurements of field of view, system spatial resolution, and signal-difference-to-noise ratio, by using gamma-emitting radioactive sources (109Cd, 125I, 241Am, 99mTc). The system spatial resolution in the lateral direction was 0.56 mm FWHM (coded aperture mask with holes of 0.08 mm and a 60 keV source) at a source-collimator distance of 50 mm and a field of view of 40 mm by side. Correspondingly, the longitudinal resolution in 3D source localization tasks was about 3 mm. MediPROBE showed a significant improvement in terms of spatial resolution when equipped with the high-resolution coded apertures, with respect to the performance previously reported with 1–2 mm pinhole apertures as well as with respect to adopting a 0.35 mm pinhole aperture.

This study relates to the INFN project SYRMA-3D for in vivo phase-contrast breast computed tomography using the SYRMEP synchrotron radiation beamline at the ELETTRA facility in Trieste, Italy. This peculiar imaging technique uses a novel dosimetric approach with respect to the standard clinical procedure. In this study, optimization of the acquisition procedure was evaluated in terms of dose delivered to the breast. An offline dose monitoring method was also investigated using radiochromic film dosimetry. Various irradiation geometries have been investigated for scanning the prone patient's pendant breast, simulated by a 14 cm-diameter polymethylmethacrylate cylindrical phantom containing pieces of calibrated radiochromic film type XR-QA2. Films were inserted mid-plane in the phantom, as well as wrapped around its external surface, and irradiated at 38 keV, with an air kerma value that would produce an estimated mean glandular dose of 5 mGy for a 14 cm-diameter 50% glandular breast. Axial scans were performed over a full rotation or over 180°. The results point out that a scheme adopting a stepped rotation irradiation represents the best geometry to optimize the dose distribution to the breast. The feasibility of using a piece of calibrated radiochromic film wrapped around a suitable holder around the breast to monitor the scan dose offline is demonstrated.

We developed a scanner for micro computed tomography dedicated to the breast (BµCT) with a high resolution flat-panel detector and a microfocus X-ray tube. We evaluated the system spatial resolution via the 3D modulation transfer function (MTF). In addition to conventional absorption-based X-ray imaging, such a prototype showed capabilities for propagation-based phase-contrast and related edge enhancement effects in 3D imaging. The system limiting spatial resolution is 6.2mm −1 (MTF at 10%) in the vertical direction and 3.8mm −1 in the radial direction, values which compare favorably with the spatial resolution reached by mini focus breast CT scanners of other groups. The BµCT scanner was able to detect both microcalcification clusters and masses in an anthropomorphic breast phantom at a dose comparable to that of two-view mammography. The use of a breast holder is proposed in order to have 1–2min long scan times without breast motion artifacts.

Purpose: In cone-beam computed tomography dedicated to the breast (BCT), the mean glandular dose (MGD) is the dose metric of reference, evaluated from the measured air kerma by means of normalized glandular dose coefficients (DgNCT). This work aimed at computing, for a simple breast model, a set of DgNCT values for monoenergetic and polyenergetic X-ray beams, and at validating the results vs. those for patient specific digital phantoms from BCT scans. Methods: We developed a Monte Carlo code for calculation of monoenergetic DgNCT coefficients (energy range 4.25–82.25 keV). The pendant breast was modelled as a cylinder of a homogeneous mixture of adipose and glandular tissue with glandular fractions by mass of 0.1%, 14.3%, 25%, 50% or 100%, enveloped by a 1.45 mmthick skin layer. The breast diameter ranged between 8 cm and 18 cm. Then, polyenergetic DgNCT coefficients were analytically derived for 49-kVp W-anode spectra (half value layer 1.25–1.50mm Al), as in a commercial BCT scanner. We compared the homogeneous models to 20 digital phantoms produced from classified 3D breast images. Results: Polyenergetic DgNCT resulted 13% lower than most recent published data. The comparison vs. patient specific breast phantoms showed that the homogeneous cylindrical model leads to a DgNCT percentage difference between −15% and +27%, with an average overestimation of 8%. Conclusions: A dataset of monoenergetic and polyenergetic DgNCT coefficients for BCT was provided. Patient specific breast models showed a different volume distribution of glandular dose and determined a DgNCT 8% lower, on average, than homogeneous breast model.

The principle of rotational summation of the absorbed dose for breast cancer treatment with orthovoltage X-ray beams was proposed by J. Boone in 2012. Here, use of X-ray synchrotron radiation for image guided external beam rotational radiotherapy treatment of breast cancer is proposed. Tumor irradiation occurs with the patient in the prone position hosted on a rotating bed, with her breast hanging from a hole in the bed, which rotates around a vertical axis passing through the tumor site. Horizontal collimation of the X-ray beam provides for whole breast or partial breast irradiation, while vertical translation of the bed and successive rotations allow for irradiation of the full tumor volume, with dose rates which permit also hypofractionated treatments. In this work, which follows a previous preliminary report, results are shown of a full series of measurements on polyethylene and acrylic cylindrical phantoms carried out at the Australian Synchrotron, confirmed byGeant4Monte Carlo simulations, intended to demonstrate the proof of principle of the technique. Dose measurements were carried out with calibrated ion chambers, radiochromic films and thermoluminescence dosimeters. The photon energy investigated was 60 keV. Image guidance may occur with the transmitted beam for contrast-enhanced breast computed tomography. For a horizontal beam collimation of 1.5 cm and rotation around the central axis of a 14 cm-diameter polyethylene phantom, a periphery-to-center dose ratio of 14% was measured. The simulations showed that under the same conditions the dose ratio decreases with increasing photon energy down to 10% at 175 keV. These values are comparable with those achievable with conventional megavoltage radiotherapy of breast cancer with a medical linear accelerator. Dose painting was demonstrated with two off-center `cancer foci' with 1.3 Gy and 0.6 Gy target doses. The use of a radiosensitizing agent for dose enhancement is foreseen.

Purpose - To characterize the dependence of normalized glandular dose (DgN) on various breast model and image acquisition parameters during spot compression mammography and other partial breast irradiation conditions, and evaluate alternative previously proposed dose‐related metrics for this breast imaging modality. Methods - Using Monte Carlo simulations with both simple homogeneous breast models and patient‐specific breasts, three different dose‐related metrics for spot compression mammography were compared: the standard DgN, the normalized glandular dose to only the directly irradiated portion of the breast (DgNv), and the DgN obtained by the product of the DgN for full field irradiation and the ratio of the mid‐height area of the irradiated breast to the entire breast area (DgNM). How these metrics vary with field‐of‐view size, spot area thickness, x‐ray energy, spot area and position, breast shape and size, and system geometry was characterized for the simple breast model and a comparison of the simple model results to those with patient‐specific breasts was also performed. Results - The DgN in spot compression mammography can vary considerably with breast area. However, the difference in breast thickness between the spot compressed area and the uncompressed area does not introduce a variation in DgN. As long as the spot compressed area is completely within the breast area and only the compressed breast portion is directly irradiated, its position and size does not introduce a variation in DgN for the homogeneous breast model. As expected, DgN is lower than DgNv for all partial breast irradiation areas, especially when considering spot compression areas within the clinically used range. DgNM underestimates DgN by 6.7% for a W/Rh spectrum at 28kVp and for a 9×9cm2 compression paddle. Conclusion - As part of the development of a new breast dosimetry model, a task undertaken by the American Association of Physicists in Medicine and the European Federation of Organizations of Medical Physics, these results provide insight on how DgN and two alternative dose metrics behave with various image acquisition and model parameters.

We investigated the influence of model assumptions in GEANT4 Monte Carlo (MC) simulations for the calculation of monoenergetic and polyenergetic normalized glandular dose coefficients (DgN) in mammography, focussing on the effect of the skin thickness and composition, of the role of compression paddles and of the bremsstrahlung processes. We showed that selecting a skin thickness of 4 mm instead of 1.45 mm produced DgN values with deviations from 9% to 32% for x-ray spectra routinely adopted in mammography. Consideration of the bremsstrahlung radiation had a weak influence on monoenergetic DgN. Simulations (in the range 8-40 kVp) which included consideration of bremsstrahlung radiation, a skin thickness of 1.45 mm and a 2 mm thick compression paddles produced polyenergetic DgN coefficients up to 19% higher than corresponding literature data. Adding a 2 mm thick adipose layer between the skin layer and the radiosensitive portion of the breast produces polyenergetic DgN values up to 15% higher than those routinely adopted. These findings provide a quantitative estimate of the influence of model parameters on the calculation of the mean glandular dose in mammography.

The aim of this work is the evaluation of the software BreastSimulator, as a tool for the creation of 3D uncompressed breast digital models and for the simulation and the optimization of Computed Tomography (CT) equipment. Three 3D digital breast phantoms were created, having different sizes and with realistic anatomical features. We calculated 2D X-ray CT projections simulating a breast tomogram with a dedicated cone-beam CT scanner. From the reconstructed CT slices, the power-law exponent, has been evaluated from the Noise Power Spectrum function S(f)=α/fβ. The results were then verified by comparison against clinical CT and published data. The preliminary results of this study showed that the simulated model complexity may reproduce the real anatomical complexity of the breast tissues as described, in terms of β values, since the measured β coefficients are close to that of clinical CT data from a dedicated breast CT scanner.

Purpose Recently, we proposed the use of the synchrotron radiation (SR) beam for a new rotational radiotherapy technique for breast cancer treatment (SR3T) [1] ;. In this work, we show, via Monte Carlo (MC) simulations, the potential of SR3T also for application in breast radiosurgery with the patient in prone position. Methods We simulated the irradiation condition of the breast rotational radiosurgery with a MC code based on GEANT 4 toolkit. The pendant breast was modeled as a polyethylene cylinder with a diameter of 14 cm and height of 9 cm with a 1-cm tumor simulated in the centre or at 4 cm from the cylinder axis. A monoenergetic laminar SR beam of size 1.5 cm × 1.0 cm with energy ranging between 60 and 120 keV irradiated the phantom during a complete rotation with the center of rotation along the tumor mass. Results A collimated SR beam irradiating a pendant breast produces a dose distribution peaked at the center of rotation. MC simulations showed that is possible to perform partial-breast irradiation with a skin sparing comparable with that from a conventional MV breast radiotherapy. Conclusions We proposed a kV SR beam for partial-breast irradiation, for breast radiosurgery in the treatment of small lesions. We foresee the use of dose-enhancement agents in order to improve the dose to the target volume with proper sparing of healthy tissues.

Purpose Measurements of the dose volume distribution in digital breast tomosynthesis (DBT) are lacking. They are useful for validation of Monte Carlo simulations in DBT dosimetry and also for devising models of radio-induced cancer risk in DBT exams. Due to the different scanner protocols (scan angle and spectra) the dose distribution can vary among DBT units and its determination is useful in scanner optimization and performance comparisons. We measured the dose volume distribution in breast phantoms for two DBT scanners. Methods We employed calibrated XR-QA2 radiochromic film pieces (25 × 15 cm2) placed within two layered breast phantoms: a circular homogenous PMMA phantom composed of five 1-cm thick layers with a diameter of 20 cm and a commercial BR3D CIRS mammographic phantom. Dose maps were measured at several horizontal planes in the phantom, including the entrance and exit surfaces. Two DBT scanners were employed at the University Hospital of Leuven: Hologic Selenia Dimensions and Mammomat Siemens Inspiration Prime, operated at 31 (HVL = 0.53 mmAl) and 29 kVp (HVL = 0.54 mmAl), respectively. Results The dose distributions within the PMMA phantom did not largely depend on the scanner type. However, the measurements with the heterogeneous CIRS phantom showed larger dose differences. For the Siemens unit, the exit dose was 21% of the entrance surface dose, for both phantoms. For the Hologic unit, this value reduced to 14% and 12%, for the CIRS and the PMMA phantoms, respectively. The in-plane dose spread in PMMA, evaluated as the percentage difference from the dose in a fixed region at the chest wall, was less than a few percent for both scanners. In the case of the CIRS phantom, the maximum in-plane dose spread was 10% for the Hologic and it was reduced to less than 5% for the Siemens unit. Conclusions 3D dose distributions were measured using two different DBT scanners. The dose spread was larger for the phantom which replicate the heterogeneous tissues distribution of the breasts. In this case, the dose spread in planes parallel to the detector is less than 10% and the entrance-to-exit dose ratio is less than 21%, for the two investigated DBT units.

Purpose The development of compact sources of high brilliance, mono-chromatic, tunable X-rays with energy in the range 30–150 keV is a topical research field; applications in radiodiagnostics are foreseen. The aim of this work is to propose the use of a compact source based on X-ray Compton back-scattering (also known as Inverse Compton Source, ICS) developed within the MariX/BriXS project [1] , for kilovoltage rotational radiotherapy dedicated to the breast. Methods The proposed source is based on a modified Tigner scheme of push-and-pull twin Super-Conducting Energy Recovery Linacs, just wrapped on itself in order to halve the overall length of the machine. The ICS source was simulated by using the code CAIN and the output X-ray photon beam was obtained. The anticipated performances are a flux up to 1013 photons/s within 5% bandwidth, coming in radiation pulses a few psec long at a repetition rate up to 100 MHz, fully tunable in the 20–150 keV energy range with full control of polarization and adjustable bandwidth in the range 0.5–10%. The simulated X-ray spectrum was used as an input of a previously validated Monte Carlo Geant4 code to calculate the dose distribution in a 50/50 breast phantom during a rotational radiotherapy scan. The pendant breast was modelled as a cylinder of 14 cm diameter and 9 cm height irradiated over 360 deg at 88 keV average energy and a 1-cm tumor was simulated at the isocenter. Results The dose distribution obtained with the kilovoltage beam generated by the ICS source shows that it is possible to perform a partial breast irradiation with dose levels to the target and to the skin, compatible with clinical treatments using conventional linacs. Conclusions We proposed the application of a Compton back-scattering X-ray source for kilovoltage rotational radiotherapy for breast cancer. The technique could be useful for partial breast irradiation with or without injection of a dose enhancement agent, for radiosurgery of small size breast tumors.

Monte Carlo calculations for breast dosimetry in Digital Breast Tomosynthesis (DBT) may require experimental validations, e.g. via the assessment of the calculated and measured dose volume distribution in the breast. This might also take into account any uneven distribution of the beam intensity in the entrance plane, not usually considered in Monte Carlo simulations, e.g. as determined by the heel effect. We measured the 3D dose distribution in a breast phantom, using XR-QA2 radiochromic films calibrated in free-in-air air kerma. Film sheets were positioned at the entrance surface, at the bottom surface as well as at four depths between adjacent slabs in the 5-slabs, 5-cm-thick phantom simulating a compressed breast with 50% glandular fraction. By varying the irradiation angle, the basic requirements of a DBT scan were simulated. The irradiations were made at 40 kV (HVL 1.1 mm Al) for three angular positions of the beam central axis (θ = ±25 deg and θ = 0 deg normal incidence, simulating a craniocaudal view). Results show that it is possible to determine the transverse and longitudinal distribution of the average dose in the phantom (in terms of kerma in simulated breast tissue 50/50 normalized to the entrance kerma), showing the angular dependence of the depth-resolved dose. In the direction of the beam axis, the dose decreases down to about 26% of the entrance value without the phantom. The backscatter fraction was 8%. In transverse planes the maximum dose variations are between 6% and 18% at θ = 0 deg, whereas the dose varies up to 22% in angular views.

Introduction Normalized glandular dose coefficients (gN CT )for computed tomography dedicated to the breast with a polychromatic X-ray source are available for estimating the mean glandular dose in a breast CT scan. However, a number of assumptions and simplifications are introduced in their derivation using Monte Carlo (MC) codes, both on breast geometry and on photon tracking and energy deposition details. Purpose To investigate, via MC simulations, four different factors which affect DgN CT calculation: (1) skin thickness, (2) electron tracking energy cutoff, (3) source position and (4) glandular tissue distribution. Materials and methods The MC code was developed using GEANT4. The breast was simulated as a cylindrical homogenous mixture of fat and glandular tissue. Skin thickness was varied from 1.45 to 4 mm. Monochromatic (8–80 keV) DgN CT have been calculated and the polychromatic DgN CT were computed by weighting them for typical X-ray tube spectra adopted for breast CT. A heterogeneous breast model as a mixture of adipose and randomly disposed glandular tissue voxels was investigated. Results Default GEANT4 electron energy cutoff leads to a DgN CT overestimation up to 1.6% at 60 keV. The skin thickness affects DgN CT values by about 1% (30–80 keV). DgN CT values calculated for a heterogeneous breast differ by 2% with respect to a homogeneous tissue mixture approximation. The X-ray source position also affects the DgN CT determinations, and setup-specific dose coefficients should be adopted. Conclusion Some factors which influence DgN CT MC calculations have been investigated and new polychromatic DgN CT coefficients have been computed in breast CT. Disclosure Nothing to declare.

Introduction Digital Mammography is a fundamental technique in breast cancer diagnosis. DM returns a two-dimensional representation of a three-dimensional object. Therefore, tissues belonging to different planes are all projected on the same X-ray image plane. Digital Breast Tomosynthesis (DBT) and Breast Computed Tomography (BCT) are two forms of 3D X-ray breast imaging for diagnostic exam developed to overcome this limitation. Recently, it has been shown that for the generation of the radiographic contrast it is possible to exploit also the information related to the wave phase shift introduced in the propagation of X-rays in matter. Purpose To compare image quality in monochromatic DBT and BCT scans with propagation based phase contrast imaging of a 3D breast phantom. Materials and methods The CIRS Model 020 BR3D is used to evaluate the image quality in the two modalities. The standard package consists of 6 slabs of thickness of 1 cm, each slice is produced by tissue equivalent materials in an approximate 50/50 ratio by weight. The central slab of the stack contains assortments of simulated microcalcifications, fibers and masses. The experiment was conducted on the biomedical beamline ID 17 at the European Synchrotron Radiation Facility. The comparison will be made in terms of noise, contrast, CNR, SNR and spatial resolution, for simulated masses and microcalcifications. Results First measurements show slightly higher values for CNR and C for masses in CT images than in DBT images. Conclusion The image quality in DBT and BCT monochromatic images of a 3D breast phantom was evaluated.

The aim of this work is to assess the performance of a prototype compact gamma camera (MediPROBE) based on a CdTe semiconductor hybrid pixel detector for coded aperture imaging. This probe can be adopted for various tasks in nuclear medicine such as preoperative sentinel lymph node localization, breast imaging with 99mTc-sestamibi and thyroid imaging with iodinated radioisotopes. The hybrid detector is an assembly of a 1mm thick CdTe semiconductor detector (sensitive area 14.08×14.08 mm2) bump-bonded to a photon-counting CMOS readout circuit of the Medipix2 series (256×256 square pixels, 55-μm pitch) or with a photon counting, energy-sensitive Timepix detector (128×128 square pixels, 110-μm pixel pitch). MediPROBE is equipped with a set of three interchangeable knife-edge pinhole collimators (hole aperture of 0.78 mm, 1 mm, or 1.9 mm) and a set of two coded aperture masks with 0.070-mm or 0.080-mm round holes. We performed measurements of field of view (FOV), system spatial resolution, and signal-difference-to-noise ratio (SDNR) by using a point-like gamma-emitting 241Am source (60 keV). The detector is operated at a single low-energy threshold of about 5 keV. At 60 keV the sensitivity is 0.0085 cps/kBq (w/0.78 mm pinhole). The system spatial resolution was 2.57 mm FWHM (w/ 0.78 mm pinhole) at a source-collimator distance of 45 mm, and 0.560 mm FWHM (w/ coded aperture 0.080 mm) at a source-collimator distance of 50 mm. We observed greater values of SDNR with the use of the coded aperture and the Timepix detector. A clinical trial is ongoing to evaluate the performance of MediPROBE for gamma-ray nuclear imaging.

Breast physical phantoms are a basic tool for the assessment and verification of performance standards in daily clinical practice of x-ray breast imaging modalities. They are also invaluable in testing and evaluation of new x-ray breast modalities to be potentially established, e.g. breast computed tomography, dual-energy breast CT and phase-contrast mammography and tomography. Nowadays, there is a lack or there are only a limited number of breast physical phantoms available for this purpose. The aim of this study is to explore a range of 3D printing materials such as resins, PLA, ABS, Nylon etc, to determine their attenuation and refractive properties, and to finally compare them to the properties of the breast tissues: adipose, glandular and skin. To achieve this goal, step-wedge phantoms were computationally modeled and then manufactured using stereolithographic and fused-deposition modeling technologies. X-ray images of the phantoms were acquired, using monochromatic beam at ID17, ESRF, Grenoble for three energies-30 keV, 45 keV and 60 keV. Experimental data were further processed to obtain the linear attenuation coefficients of these materials. Comparison with theoretical data for the linear attenuation coefficients and the refractive indexes for breast tissues was performed. From the studied materials, most of the resins, Nylon, Hybrid, PET-G show absorption properties close to the glandular tissue, while ABS shows absorption characteristics close to these of the adipose tissue. For phase-contrast imaging, it turns out that the ABS combined with resin-based materials to represent the adipose and glandular tissues, respectively may be a good combination for manufacturing of a phantom suitable for these studies. These results can be used for the design and the construction of a new physical anthropomorphic phantom of the breast with improved anatomical and radiological characteristics dedicated for advanced mammography imaging techniques implemented at higher photon energies. ispartof: PHYSICS IN MEDICINE AND BIOLOGY vol:63 issue:17 ispartof: location:England status: published

We performed laboratory investigations of the image quality for in-line phase contrast micro tomography dedicated to the breast, using a 3D breast phantom. We employed the cone-beam, microfocus (7-micrometer focal spot size) computed tomography (CT) scanner developed in-house for investigation of high resolution, absorption based, and phase contrast based, X-ray imaging of the breast for cancer diagnosis, at dose levels comparable to two-view mammography. CT slices were reconstructed (FDK algorithm) from phase contrast projection images as well as from phase retrieved projections (ANKAphase algorithm), under the assumption of spatially uniform distribution in the object volume of the ratio of the X-ray optical coefficients of the sample material, at the effective energy of the X-ray beam (80 kV, HVL = 6.11 mm Al). Microcalcifications were best visible after phase retrieval, down to 0.23 mm size.