Experimental optimization of the energy for breast-CT with synchrotron radiation

Breast Computed Tomography (bCT) is a three-dimensional imaging technique that is raising interest among radiologists as a viable alternative to mammographic planar imaging. In X-rays imaging it would be desirable to maximize the capability of discriminating different tissues, described by the Contrast to Noise Ratio (CNR), while minimizing the dose (i.e. the radiological risk). Both dose and CNR are functions of the X-ray energy. This work aims at experimentally investigating the optimal energy that, at fixed dose, maximizes the CNR between glandular and adipose tissues. Acquisitions of both tissue-equivalent phantoms and actual breast specimens have been performed with the bCT system implemented within the Syrma-3D collaboration at the Syrmep beamline of the Elettra synchrotron (Trieste). The experimental data have been also compared with analytical simulations and the results are in agreement. The CNR is maximized at energies around 26–28 keV. These results are in line with the outcomes of a previously presented simulation study which determined an optimal energy of 28 keV for a large set of breast phantoms with different diameters and glandular fractions. Finally, a study on photon starvation has been carried out to investigate how far the dose can be reduced still having suitable images for diagnostics

Proceedings Virtual Imaging Trials in Medicine 2024

This submission comprises the proceedings of the 1st Virtual Imaging Trials in Medicine conference, organized by Duke University on April 22-24, 2024. The listed authors serve as the program directors for this conference. The VITM conference is a pioneering summit uniting experts from academia, industry and government in the fields of medical imaging and therapy to explore the transformative potential of in silico virtual trials and digital twins in revolutionizing healthcare. The proceedings are categorized by the respective days of the conference: Monday presentations, Tuesday presentations, Wednesday presentations, followed by the abstracts for the posters presented on Monday and Tuesday

Virtual clinical trials in medical imaging: a review

The accelerating complexity and variety of medical imaging devices and methods have outpaced the ability to evaluate and optimize their design and clinical use. This is a significant and increasing challenge for both scientific investigations and clinical applications. Evaluations would ideally be done using clinical imaging trials. These experiments, however, are often not practical due to ethical limitations, expense, time requirements, or lack of ground truth. Virtual clinical trials (VCTs) (also known as in silico imaging trials or virtual imaging trials) offer an alternative means to efficiently evaluate medical imaging technologies virtually. They do so by simulating the patients, imaging systems, and interpreters. The field of VCTs has been constantly advanced over the past decades in multiple areas. We summarize the major developments and current status of the field of VCTs in medical imaging. We review the core components of a VCT: computational phantoms, simulators of different imaging modalities, and interpretation models. We also highlight some of the applications of VCTs across various imaging modalities

Multiscale X-ray phase-contrast tomography: From breast CT to micro-CT for virtual histology

Phase-contrast imaging techniques address the issue of poor soft-tissue contrast encountered in traditional X-ray imaging. This can be accomplished with the propagation-based phase-contrast technique by employing a coherent photon beam, which is available at synchrotron facilities, as well as long sample-to-detector distances. This study demonstrates the optimization of propagation-based phase-contrast computed tomography (CT) techniques for multiscale X-ray imaging of the breast at the Elettra synchrotron facility (Trieste, Italy). Two whole breast mastectomy samples were acquired with propagation-based breast-CT using a monochromatic synchrotron beam at a pixel size of 60 μm. Paraffin-embedded blocks sampled from the same tissues were scanned with propagation-based micro-CT imaging using a polychromatic synchrotron beam at a pixel size of 4 μm. Images of both methodologies and of the same sample were spatially registered. The resulting images showed the transition from whole breast imaging with propagation-based breast-CT methodology to virtual histology with propagation-based micro-CT imaging of the same sample. Additionally, conventional histological images were matched to virtual histology images. Phase-contrast images offer a high resolution with low noise, which allows for a highly precise match between virtual and conventional histology. Furthermore, those techniques allow a clear discernment of breast structures, lesions, and microcalcifications, being a promising clinically-compatible tool for breast imaging in a multiscale approach, to either assist in the detection of cancer in full volume breast samples or to complement structure identification in paraffin-embedded breast tissue samples

DEVELOPMENT OF A PATIENT SPECIFIC IMAGE PLANNING SYSTEM FOR RADIATION THERAPY

A patient specific image planning system (IPS) was developed that can be used to assist in kV imaging technique selection during localization for radiotherapy. The IPS algorithm performs a divergent ray-trace through a three dimensional computed tomography (CT) data set. Energy-specific attenuation through each voxel of the CT data set is calculated and imaging detector response is integrated into the algorithm to determine the absolute values of pixel intensity and image contrast. Phantom testing demonstrated that image contrast resulting from under exposure, over exposure as well as a contrast plateau can be predicted by use of a prospective image planning algorithm. Phantom data suggest the potential for reducing imaging dose by selecting a high kVp without loss of image contrast. In the clinic, image acquisition parameters can be predicted using the IPS that reduce patient dose without loss of useful image contrast

Optimization of a High-Energy X-Ray Inline Phase Sensitive Imaging System for Diagnosis of Breast Cancer

Breast cancer screening modalities have received constant research attention that are mainly focused on their abilities to detect cancer at an early stage while reducing the risks of harmful radiation dose delivered to the patient. As a result, numerous advancements have been made over the last two decades which include the introduction of digital mammography (DM) and digital breast tomosynthesis (DBT). Numerous clinical trials have demonstrated the decrease in mortality rates by employing these modalities. Significant research attention remains focused on investigating methods for further improving the detection capabilities and reducing the radiation dose. The conventional x-ray imaging technique relies on the attenuation characteristics of a tissue to produce imaging contrast. However, the similar attenuation characteristics of normal and malignant breast tissue present a challenge in differentiating between them using conventional x-ray imaging. The current technique for providing higher image quality involves the introduction of anti-scatter grids and operating the x-ray tubes at much lower x-ray energies as compared to the other radiography fields, both of which results in an increased radiation dose. The current method for providing higher image quality involves utilizing anti-scatter grids and operating at much lower x-ray energies than other radiography fields, both of which result in an increased radiation dose. Phase sensitive imaging is an emerging technique, which relies not only on attenuation coefficients but also the effects produced by x-ray phase shift coefficients. Within the diagnostic energy range, it has been estimated that the phase shift coefficients of a breast tissue are at least 2-3 orders of magnitude larger than their attenuation coefficients. Thus, this technique holds the potential to increase the x-ray energy and remove the grid without compromising the image quality, which could potentially reduce the patient dose. The inline phase sensitive approach involves the simplest implementation—provided that the imaging system is spatially coherent — as it does not involve the introduction of any optical element between the object and detector. Preclinical studies with the inline phase sensitive imaging technique at the same energy as conventional imaging have indicated the ability to reduce the radiation dose without negatively impacting the diagnostic capabilities. However, there are some existing challenges that have prevented this technique in its clinical implementation. Responding to the challenges, an inline phase sensitive imaging prototype has been developed in the advanced biomedical imaging laboratory. The goal of the research presented in this dissertation comprises a thorough investigation in optimizing a high energy phase sensitive imaging prototype efficiently in terms of its geometric and operating parameters. Once optimized, the imaging performance of this phase sensitive x-ray imaging prototype is going to be compared with the commercial digital mammography and digital breast tomosynthesis (DBT) imaging systems using modular breast phantoms at similar and reduced mean glandular dose (Dg) dose levels. This dissertation includes numerous original contributions, perhaps the most significant of which were the demonstration of the ability of inline phase sensitive imaging prototype to deliver higher image quality required for tumor detection and diagnosis at higher x-ray energies in comparison with low energy commercial imaging systems at similar or less radiation dose levels. These results clearly demonstrate the ability of the high energy inline phase sensitive imaging system to maintain the image quality improvement that is necessary for diagnosis at high x-ray energies without an increase in the radiation dose

Characterizing Accuracy of Total Hemoglobin Recovery Using Contrast-Detail Analysis in 3D Image-Guided Near Infrared Spectroscopy with the Boundary Element Method

The quantification of total hemoglobin concentration (HbT) obtained from multi-modality image-guided near infrared spectroscopy (IG-NIRS) was characterized using the boundary element method (BEM) for 3D image reconstruction. Multi-modality IG-NIRS systems use a priori information to guide the reconstruction process. While this has been shown to improve resolution, the effect on quantitative accuracy is unclear. Here, through systematic contrast-detail analysis, the fidelity of IG-NIRS in quantifying HbT was examined using 3D simulations. These simulations show that HbT could be recovered for medium sized (20mm in 100mm total diameter) spherical inclusions with an average error of 15%, for the physiologically relevant situation of 2:1 or higher contrast between background and inclusion. Using partial 3D volume meshes to reduce the ill-posed nature of the image reconstruction, inclusions as small as 14mm could be accurately quantified with less than 15% error, for contrasts of 1.5 or higher. This suggests that 3D IG-NIRS provides quantitatively accurate results for sizes seen early in treatment cycle of patients undergoing neoadjuvant chemotherapy when the tumors are larger than 30mm