Optimizing and applying high-resolution, in-line laboratory phase-contrast X-ray imaging for low-density material samples

3D Virtual Histopathology by Phase-Contrast X-Ray Micro-CT for Follicular Thyroid Neoplasms

Histological analysis is the core of follicular thyroid carcinoma (FTC) classification. The histopathological criteria of capsular and vascular invasion define malignancy and aggressiveness of FTC. Analysis of multiple sections is cumbersome and as only a minute tissue fraction is analyzed during histopathology, under-sampling remains a problem. Application of an efficient tool for complete tissue imaging in 3D would speed-up diagnosis and increase accuracy. We show that X-ray propagation-based imaging (XPBI) of paraffin-embedded tissue blocks is a valuable complementary method for follicular thyroid carcinoma diagnosis and assessment. It enables a fast, non-destructive and accurate 3D virtual histology of the FTC resection specimen. We demonstrate that XPBI virtual slices can reliably evaluate capsular invasions. Then we discuss the accessible morphological information from XPBI and their significance for vascular invasion diagnosis. We show 3D morphological information that allow to discern vascular invasions. The results are validated by comparing XPBI images with clinically accepted histology slides revised by and under supervision of two experienced endocrine pathologists.

Inflammatory tissue response in human soft tissue is caused by a higher particle load near carbon fiber-reinforced PEEK compared to titanium plates

Titanium as the leading implant material in locked plating is challenged by polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK), which became the focus of interest of researchers and manufacturers in recent years. However, data on human tissue response to these new implant materials are rare. Osteosynthesis plates and peri‑implant soft tissue samples of 16 healed proximal humerus fractures were examined (n = 8 CFR-PEEK, n = 8 titanium). Soft tissue was analyzed by immunohistochemistry and µCT. The entrapped foreign bodies were further examined for their material composition by FTIR. To gain insight into their origin and formation mechanism, explanted and new plates were evaluated by SEM, EDX, profilometry and HR-CT. In the peri‑implant soft tissue of the CFR-PEEK plates, an inflammatory tissue reaction was detected. Tissues contained foreign bodies, which could be identified as tantalum wires, carbon fiber fragments and PEEK particles. Titanium particles were also found in the peri‑implant soft tissue of the titanium plates but showed a less intense surrounding tissue inflammation in immunohistochemistry. The surface of explanted CFR-PEEK plates was rougher and showed exposed and broken carbon fibers as well as protruding and deformed tantalum wires, especially in used screw holes, whereas scratches were identified on the titanium plate surfaces. Particles were present in the peri‑implant soft tissue neighboring both implant materials and could be clearly assigned to the plate material. Particles from both plate materials caused detectable tissue inflammation, with more inflammatory cells found in soft tissue over CFR-PEEK plates than over titanium plates. STATEMENT OF SIGNIFICANCE: Osteosynthesis plates are ubiquitously used in various medical specialties for the reconstruction of bone fractures and defects and are therefore indispensable for trauma surgeons, ENT specialists and many others. The leading implant material are metals such as titanium, but recently implants made of polymers such as carbon fiber-reinforced polyetheretherketone (CFR-PEEK) have become increasingly popular. However, little is known about human tissue reaction and particle generation related to these new implant types. To clarify this question, 16 osteosynthesis plates (n = 8 titanium and n = 8 CFR-PEEK) and the overlying soft tissue were analyzed regarding particle occurrence and tissue inflammation. Tissue inflammation is clinically relevant for the development of scar tissue, which is discussed to cause movement restrictions and thus contributes significantly to patient outcome.

Framework to optimize fixed-length micro-CT systems for propagation-based phase-contrast imaging

A laboratory X-ray imaging system with a setup that closely resembles commercial micro-CT systems with a fixed source-to-detector distance of ∼90 cm is investigated for single distance propagation-based phase-contrast imaging and computed tomography (CT). The system had a constant source-to-detector distance, and the sample positions were optimized. Initially, a PTFE wire was imaged, both in 2D and 3D, to characterize fringe contrast and spatial resolution for different X-ray source settings and source-to-sample distances. The results were compared to calculated values based on theoretical models and to simulated (wave-optics based) results, with good agreement being found. The optimization of the imaging system is discussed. CT scans of two biological samples, a tissue-engineered esophageal scaffold and a rat heart, were then acquired at the optimum parameters, demonstrating that significant image quality improvements can be obtained with widely available components placed inside fixed-length cabinets through proper optimization of propagation-based phase-contrast.

Non contrast enhanced volumetric histology of blood clots through high resolution propagation-based X-ray microtomography

We have demonstrated the capability of laboratory propagation-based microtomography (miroCT) in non-destructive 3D virtual histopathology of human blood clots without any contrast agent. The volumetric information are valuable to understand the mechanical properties of clots which are crucial in selecting the most efficient mechanical thrombectomy method for clot extraction. Different clot types retrieved by mechanical thrombectomy from patient victims of acute ischemic stroke were evaluated through propagation-based microCT. The results were correlated with high-resolution scanning electron microscopy (SEM) images, confirming detected cellular and fibrillary structures. Calcifications appeared as glassy opacity areas with relatively intense signal on microCT images, also proved by energy-dispersive spectroscopy and X-ray diffraction. Hyperintense regions on the microCT corresponded to individual or compact aggregates of red blood cells, whereas fibrin dominated volumes appeared at consistently moderate to low normalized microCT values. Red blood cell shapes and sizes are consistent with the SEM observations. Together with other potential parameters, 3D porosity distribution and volume fraction of structures can be easily measured by microCT data. Further development of automated post-processing techniques for X-ray propagation-based micro/nanoCT, also based on machine learning algorithms, can enable high throughput analysis of blood clot composition and their 3D histological features on large sample cohorts.

An In-House Cone-Beam Tomographic Reconstruction Package for Laboratory X-ray Phase-Contrast Imaging

Phase-contrast, and in general, multi-modal, X-ray micro-tomography is proven to be very useful for low-density, low-attention samples enabling much better contrast than its attenuation-based pendant. Therefore, it is increasingly applied in bio- and life sciences primarily dealing with such samples. Although there is a plethora of literature regarding phase-retrieval algorithms, access to implementations of those algorithms is relatively limited and very few packages combining phase-retrieval methods with the full tomographic reconstruction pipeline are available. This is especially the case for laboratory-based phase-contrast imaging typically featuring cone-beam geometry. We present here an in-house cone-beam tomographic reconstruction package for laboratory X-ray phase-contrast imaging. It covers different phase-contrast techniques and phase retrieval methods. The paper explains their implementation and integration in the filtered back projection chain. Their functionality and efficiency will be demonstrated through applications on a few dedicated samples.