Tissue artefacts caused by sponges.

Artefacts which occur during the processing of small biopsy specimens can cause sufficient tissue distortion to impair interpretation and can be a considerable source of nuisance. Triangular artefacts were noted in renal and liver biopsy specimens which were caused by foam sponges in embedding cassettes. Scanning electron microscopic examination of the sponges showed they comprised a mesh of scimitar-shaped rigid spikes which closely match the artefacts seen in the tissues.     

Misdiagnosis caused by fungal contaminant in a histological stain solution.

Silver stains on tissue and cytology specimens are important in the evaluation of patients with suspected fungal infections. Care must be taken, however, to prevent misinterpretation of contamination artifacts. Two cases presenting such a problem are reported. The first patient had granulomatous leg lesions that microscopically showed characteristics of erythema induratum but with budding yeastlike organisms demonstrated by Grocott methenamine silver stain. Cultures and subsequent biopsies were negative for fungi. The second patient had a steroid-dependent chronic obstructive lung disease, and during evaluation for possible Pneumocystis carinii pneumonia, the Grocott methenamine silver stain on expectorated sputum showed budding yeastlike organisms. Sputum cultures were negative for fungi. Examination of the two Grocott light-green counterstain solutions demonstrated black, budding yeast cells similar to those seen in the specimens from the patients. Culture of the counterstain grew Exophiala (Phialophora) jeanselmei. Further studies revealed that this cause of misdiagnosis could be prevented by either filtering or adding thymol to the counterstain solution. Care regarding contamination of histological stain solutions is emphasized.     

Dissociation of immune complexes in tissue sections by excess of antigen

Immune complexes (IC) present in the glomeruli of rabbits with chronic serum sickness (CSS) and in patients with systemic lupus erythematosus (SLE), idiopathic membranous nephropathy (IMN), and acute poststreptococcal glomerulonephritis (PSGN) were analyzed by incubation with antigenic preparations. The efficacy of these preparations to dissolve IC was assayed by comparison of results of direct immunofluorescence tests performed with the kidney tissues before and after incubation with antigenic preparations. The FITC-conjugated antisera used in these tests were specific for IgG, C3, and-in the case of CSS-for the eliciting antigen, bovine serum albumin (BSA). During the acute proteinuric phase of CSS in rabbits, incubation of tissue sections with BSA alone led to complete dissolution of IC. In many rabbits with late phase proteinuria, however, tissues had to be incubated with both BSA and aggregated fraction II of rabbit serum. In all biopsy specimens from patients with IMN, and in some specimens from patients with PSGN and SLE, aggregated fraction II of human serum resulted in complete or incomplete dissolution of IC. On the other hand, incubation of tissues with excess DNA in SLE or with streptococcal antigens PSGN did not lead to dissolution of IC. These studies suggest significant participation of antibodies to aggregated immunoglobulins (i.e., rheumatoid factors or rheumatoid-like factors) in IC found in the above-mentioned diseases. Other antigen -antibody systems, however, may also contribute to the deposits in the glomerulonephritides studied.     

碘过量对小鼠脾脏影响的组织学研究

目的探讨碘过量对机体免疫功能的影响。方法Balb/c小鼠32只,雌雄各半,随机分为适碘组(NI)、5倍碘组(5HI)、10倍碘组(10HI)、50倍碘组(50HI)。给以不同浓度碘化钾水喂养6个月后,处死取脾脏,对脾脏的绝对重量、脾脏指数进行测量分析,对脾脏的组织学改变进行观察,并对小鼠脾脏白髓、边缘区的体密度进行测量分析。结果摄入低倍过量碘的小鼠脾脏未见明显形态学改变,随着过量碘倍数的提高,脾脏的组织学改变逐渐明显,且呈现功能活跃的表现。结论高倍过量碘摄入可引起小鼠免疫功能亢进。     

A knowledge-based method for reducing attenuation artefacts caused by cardiac appliances in myocardial PET/CT

Attenuation artefacts due to implanted cardiac defibrillator leads have previously been shown to adversely impact cardiac PET/CT imaging. In this study, the severity of the problem is characterized, and an image-based method is described which reduces the resulting artefact in PET. Automatic implantable cardioverter defibrillator (AICD) leads cause a moving-metal artefact in the CT sections from which the PET attenuation correction factors (ACFs) are derived. Fluoroscopic cine images were measured to demonstrate that the defibrillator's highly attenuating distal shocking coil moves rhythmically across distances on the order of 1 cm. Rhythmic motion of this magnitude was created in a phantom with a moving defibrillator lead. A CT study of the phantom showed that the artefact contained regions of incorrect, very high CT values and adjacent regions of incorrect, very low CT values. The study also showed that motion made the artefact more severe. A knowledge-based metal artefact reduction method (MAR) is described that reduces the magnitude of the error in the CT images, without use of the corrupted sinograms. The method modifies the corrupted image through a sequence of artefact detection procedures, morphological operations, adjustments of CT values and three-dimensional filtering. The method treats bone the same as metal. The artefact reduction method is shown to run in a few seconds, and is validated by applying it to a series of phantom studies in which reconstructed PET tracer distribution values are wrong by as much as 60% in regions near the CT artefact when MAR is not applied, but the errors are reduced to about 10% of expected values when MAR is applied. MAR changes PET image values by a few per cent in regions not close to the artefact. The changes can be larger in the vicinity of bone. In patient studies, the PET reconstruction without MAR sometimes results in anomalously high values in the infero-septal wall. Clinical performance of MAR is assessed by two physicians' inspection of images generated in 30 patients with and without MAR. Noticeable image differences are judged in 14 of 28 (50%) observations with AICD leads, and significant clinical impact is judged in 2 of 28 (7%) of those observations. A polar map analysis shows significant differences in 10 of 14 (71%) studies with AICD leads, and 0 of 16 (0%) studies without AICD leads. These results show that the MAR method is successful in reducing the magnitude of the metal artefact without incorrectly altering cases without metal artefact. In spite of profound changes to the CT image from the moving metal, the PET ACF in that study was changed by no more than 20%.     

Post mortem histological artifacts created by poor tissue handling during necropsy

Abstract

Histological artifacts may be introduced into the tissue of laboratory animals during sample collection at the time of necropsy or during tissue processing. To identify and characterize tissue artifacts, modifications in necropsy/tissue processing standard operating procedures were made in order to reproduce some of these effects in the lungs, thyroid glands, and stomach of rats; the liver, spleen, and kidney of dogs; and the liver and spleen of non-human primates. Induced artifacts included lungs over-infused with formalin, stomachs subjected to mechanical damage, and thyroid glands roughly handled with forceps. Oversized sections of liver, spleen, and kidney tissues were forced into cassettes. All tissues were preserved for 24 hours in formalin before trimming. These tissues were processed, embedded in paraffin wax, sectioned, and stained with hematoxylin and eosin (H&E). Tissues were then examined microscopically by a pathologist and compared with control tissues collected at necropsy under standard conditions. The evaluation confirmed that artifacts such as those induced in this study can interfere with accurate histologic examination, ultimately confounding pathology interpretation. These results emphasize the importance of rigorous necropsy and tissue collection practices to ensure a consistently high quality of tissue specimens.     

Detection of cyanoacrylate tissue adhesives in histological sections

Previous histological studies of cyanoacrylate in wound healing have all used Oil-Red-O staining of paraffin sections prepared by routine method. In the course of our studies we began to suspect that artifact was being introduced because of dissolution of cyanoacrylate during processing. Accordingly, biopsis of wounds sealed with cyanoacrylate and pieces of cyanoacrylate of a standard known dimension with no associated tissue were observed after every stage of histological preparation. It was observed that approximately 80% of the cyanoacrylate was lost at the deparaffinization in xylene stage. Accordingly, a number of solvents were tested, and it was found that petroleum ether could be used to remove paraffin completely without the loss of any of the cyanoacrylate from the specimen. This technique has been used to view the location and ultimate fate of cyanoacrylate applied to wounds and examined at different stages in healing process. It is concluded that previous histological studies of cyanoacrylate in wound healing have been inaccurate due to leaching out of most of the tissue adhesive during deparaffinization of the specimen.     

Soft tissue infection and bacteremia caused by Shewanella putrefaciens

Shewanella putrefaciens is as yet rarely responsible for clinical syndromes in humans. However, a case involving multiple organs in an elderly male under treatment with appropriate steroids confirms that attention should be devoted to unusual pathogens.     

In vivo EIS characterization of tumour tissue properties is dominated by excess extracellular fluid

Electrical impedance spectroscopy (EIS) is a non-ionizing, non-invasive technique which can be used to detect the presence of malignant tumours based on their electrical properties. Although it has been suggested that the edema which accompanies tumours strongly influences EIS tumour characterization, such information has not, until now, been documented in the literature. Growing intramuscular rodent tumours were imaged using magnetic resonance imaging (MRI) and EIS at several time points post-tumour implantation. The amount of edema associated with the tumours was calculated from the MRI images. Electrical parameters (resistivity, permittivity, fluid index ratio and peak frequency) were extracted from the EIS spectra. Taken together, the resulting electrical parameters strongly indicate that edema is the dominating pathological feature in EIS characterization and can at times conceal the presence of the tumour. Receiver operating characteristic analysis supports these findings.     

Automatic segmentation of histological structures in mammary gland tissue sections

Real-time three-dimensional (3-D) reconstruction of epithelial structures in human mammary gland tissue blocks mapped with selected markers would be an extremely helpful tool for diagnosing breast cancer and planning treatment. Besides its clear clinical application, this tool could also shed a great deal of light on the molecular basis of the initiation and progression of breast cancer. We present a framework for real-time segmentation of epithelial structures in two-dimensional (2-D) images of sections of normal and neoplastic mammary gland tissue blocks. Complete 3-D rendering of the tissue can then be done by surface rendering of the structures detected in consecutive sections of the blocks. Paraffin-embedded or frozen tissue blocks are first sliced and sections are stained with hematoxylin and eosin. The sections are then imaged using conventional bright-field microscopy and their background corrected using a phantom image. We then use the fast-marching algorithm to roughly extract the contours of the different morphological structures in the images. The result is then refined with the level-set method, which converges to an accurate (subpixel) solution for the segmentation problem. Finally, our system stacks together the 2-D results obtained in order to reconstruct a 3-D representation of the entire tissue block under study. Our method is illustrated with results from the segmentation of human and mouse mammary gland tissue samples.     

Soft tissue infection associated with bacteremia caused by Shewanella putrefaciens

Shewanella putrefaciens is rarely involved in human infectious disease. We report here a case of soft tissue infection with bacteremia on a patient with risk factors (liver cirrhosis, diabetes mellitus).