3D analysis of the myenteric plexus of the human bowel by X-ray phase-contrast tomography - a future method?

Optimization of phase contrast imaging with a nano-focus x-ray tube

Propagation-based phase contrast imaging with a laboratory x-ray source is a valuable tool for studying samples that show only low absorption contrast, either because of low density, elemental composition, or small feature size. If a propagation distance between sample and detector is introduced and the illumination is sufficiently coherent, the phase shift in the sample will cause additional contrast around interfaces, known as edge enhancement fringes. The strength of this effect depends not only on sample parameters and energy but also on the experimental geometry, which can be optimized accordingly. Recently, x-ray lab sources using transmission targets have become available, which provide very small source sizes in the few hundred nanometer range. This allows the use of a high-magnification geometry with a very short source-sample distance, while still achieving sufficient spatial coherence at the sample position. Moreover, the high geometrical magnification makes it possible to use detectors with a larger pixel size without reducing the image resolution. Here, we explore the influence of magnification on the edge enhancement fringes in such a geometry. We find experimentally and theoretically that the fringes become maximal at a magnification that is independent of the total source-detector distance. This optimal magnification only depends on the source size, the steepness of the sample feature, and the detector resolution. A stronger influence of the sample feature on the optimal magnification compared to low-magnification geometries is observed.

Structure of the myenteric plexus in normal and diseased human ileum analyzed by X-ray virtual histology slices

BACKGROUND

The enteric nervous system (ENS) is situated along the entire gastrointestinal tract and is divided into myenteric and submucosal plexuses in the small and large intestines. The ENS consists of neurons, glial cells, and nerves assembled into ganglia, surrounded by telocytes, interstitial cells of Cajal, and connective tissue. Owing to the complex spatial organization of several interconnections with nerve fascicles, the ENS is difficult to examine in conventional histological sections of 3-5 μm.

AIM

To examine human ileum full-thickness biopsies using X-ray phase-contrast nanotomography without prior staining to visualize the ENS.

METHODS

Six patients were diagnosed with gastrointestinal dysmotility and neuropathy based on routine clinical and histopathological examinations. As controls, full-thickness biopsies were collected from healthy resection ileal regions after hemicolectomy for right colon malignancy. From the paraffin blocks, 4-µm thick sections were prepared and stained with hematoxylin and eosin for localization of the myenteric ganglia under a light microscope. A 1-mm punch biopsy (up to 1 cm in length) centered on the myenteric plexus was taken and placed into a Kapton^® tube for mounting in the subsequent investigation. X-ray phase-contrast tomography was performed using two custom-designed laboratory setups with micrometer resolution for overview scanning. Subsequently, selected regions of interest were scanned at a synchrotron-based end-station, and high-resolution slices were reported. In total, more than 6000 virtual slices were analyzed from nine samples.

RESULTS

In the overview scans, the general architecture and quality of the samples were studied, and the myenteric plexus was localized. High-resolution scans revealed details, including the ganglia, interganglional nerve fascicles, and surrounding tissue. The ganglia were irregular in shape and contained neurons and glial cells. Spindle-shaped cells with very thin cellular projections could be observed on the surface of the ganglia, which appeared to build a network. In the patients, there were no alterations in the general architecture of the myenteric ganglia. Nevertheless, several pathological changes were observed, including vacuolar degeneration, autophagic activity, the appearance of sequestosomes, chromatolysis, and apoptosis. Furthermore, possible expulsion of pyknotic neurons and defects in the covering cellular network could be observed in serial slices. These changes partly corresponded to previous light microscopy findings.

CONCLUSION

The analysis of serial virtual slices could provide new information that cannot be obtained by classical light microscopy. The advantages, disadvantages, and future possibilities of this method are also discussed.

Reconstructing topography and extent of injury to the superior mesenteric artery plexus in right colectomy with extended D3 mesenterectomy: a composite multimodal 3-dimensional analysis

Background

Superior mesenteric artery plexus (SMAP) injury is reported to cause postoperative intractable diarrhea after pancreatic/colonic surgery with extended lymphadenectomy. This study aims to describe the SMAP microanatomy and extent of injury after right colectomy with extended D3 mesenterectomy for cancer.

Methods

Three groups (I) anatomical dissection, (II) postmortem histology, and (III) surgical specimen histology were included. Nerve count and area were compared between groups II and III and paravascular sheath thickness between groups I and II. 3D models were generated through 3D histology, nanoCT scanning, and finally through 3D printing.

Results

A total of 21 specimens were included as follows: Group (I): 5 (3 females, 80–93 years), the SMAP is a complex mesh surrounding the superior mesenteric artery (SMA), branching out, following peripheral arteries and intertwining between them, (II): 7 (5 females, 71–86 years), nerve count: 53 ± 12.42 (38–68), and area: 1.84 ± 0.50 mm2 (1.16–2.29), and (III): 9 (5 females, 55–69 years), nerve count: 31.6 ± 6.74 (range 23–43), and area: 0.889 ± 0.45 mm2 (range 0.479–1.668). SMAP transection injury is 59% of nerve count and 48% of nerve area at middle colic artery origin level. The median values of paravascular sheath thickness decreased caudally from 2.05 to 1.04 mm (anatomical dissection) and from 2.65 to 1.17 mm (postmortem histology). 3D histology models present nerve fibers exclusively within the paravascular sheath, and lymph nodes were observed only outside. NanoCT-derived models reveal oblique nerve fiber trajectories with inclinations between 35° and 55°. Two 3D-printed models of the SMAP were also achieved in a 1:2 scale.

Conclusion

SMAP surrounds the SMA and branches within the paravascular sheath, while bowel lymph nodes and vessels lie outside. Extent of SMAP injury on histological slides (transection only) was 48% nerve area and 59% nerve count. The 35°–55° inclination range of SMAP nerves possibly imply an even larger injury when plexus excision is performed (lymphadenectomy). Reasons for later improvement of bowel function in these patients can lie in the interarterial nerve fibers between SMA branches.

Subcutaneous Low-Density Foreign Bodies Detection via Grating-Based Multimodal X-ray Imaging

Detecting low-density foreign bodies within soft tissues still stands for a serious challenge. Grating-based multimodal X-ray imaging typically has low hardware requirements while simultaneously providing three kinds of imaging information, i.e., absorption, phase-contrast, and dark-field. We aimed to explore the capacity of grating-based multimodal X-ray imaging technology for detecting common foreign bodies within subcutaneous tissues, and to assess the advantages as well as disadvantages of the three kinds of images obtained via grating-based X-ray multimodal technology in relation to diverse kinds of foreign bodies within different tissues. In this study, metal, glass, wood, plastic, graphite, and ceramic foreign bodies were injected into chunks of the pig adipose tissue and chicken thigh muscles. Next, a grating-based multimodal X-ray imaging device developed in our laboratory was used to detect the above foreign bodies within the adipose and muscle tissues. Our results show that grating-based multimodal X-ray imaging clearly revealed the subcutaneous foreign bodies within the adipose and muscle tissues by acquiring complementary absorption, phase-contrast, and dark-field imaging data in a single shot. Grating-based multimodal X-ray imaging has an exciting potential to detect foreign bodies underneath the epidermis.

Diseases which cause generalized peripheral neuropathy: a systematic review

PURPOSE

Peripheral autonomic neuropathy, including enteric neuropathy, may be subtle and unrecognized for several years. Diagnosis of enteric neuropathy demands complicated examinations such as full-thickness bowel biopsy. We hypothesized that knowledge about simultaneous occurrence of different types of neuropathy would lead to faster recognition and diagnosis of autonomic/enteric neuropathy. The aim of the present systematic review was to increase the awareness of disease groups causing autonomic and enteric neuropathy along with sensorimotor neuropathy.

METHODS

A systematic search strategy was used in PubMed, Embase and Web of Science. First, 4978 articles were identified. Review of titles/abstracts rendered exclusion of animal studies, articles not written in English or full-length, case reports, conference abstracts and duplicates until 357 articles remained. The full-length evaluation resulted in 35 studies (27 non-systematic reviews) which described objectively verified peripheral autonomic, enteric and sensorimotor neuropathy within the same disease.

RESULTS

Diabetes is the most common disease in society rendering generalized peripheral neuropathy. Accumulation of tissue deposits in amyloidosis, Lewy body disorders and sarcoidosis lead to widespread peripheral neuropathy. Several autoimmune disorders such as systemic sclerosis and primary Sjögren's syndrome present themselves with neuropathy. Paraneoplastic neuropathy may appear prior to symptoms from the malignancy. Both the infection per se, as well as the autoimmune response to the infection, i.e., Guillain-Barré syndrome, may lead to widespread peripheral neuropathy. Hereditary disorders with disturbed metabolism lead to intermittent attacks of neuropathy.

CONCLUSIONS

The major causes of generalized peripheral neuropathy are diabetes, diseases with tissue deposits, autoimmunity, infections, malignancy and metabolic diseases.