Postmortem microcomputed tomography (micro-CT) of small fetuses and hearts

Body weight-based iodinated contrast immersion timing for human fetal postmortem microfocus computed tomography

Objectives

The aim of this study was to evaluate the length of time required to achieve full iodination using potassium tri-iodide as a contrast agent, prior to human fetal postmortem microfocus computed tomography (micro-CT) imaging.

Methods

Prospective assessment of optimal contrast iodination was conducted across 157 human fetuses (postmortem weight range 2-298 g; gestational age range 12-37 weeks), following micro-CT imaging. Simple linear regression was conducted to analyse which fetal demographic factors could produce the most accurate estimate for optimal iodination time.

Results

Postmortem body weight (r2 = 0.6435) was better correlated with iodination time than gestational age (r2 = 0.1384), producing a line of best fit, y = [0.0304 × body weight (g)] - 2.2103. This can be simplified for clinical use whereby immersion time (days) = [0.03 × body weight (g)] - 2.2. Using this formula, for example, a 100-g fetus would take 5.2 days to reach optimal contrast enhancement.

Conclusions

The simplified equation can now be used to provide estimation times for fetal contrast preparation time prior to micro-CT imaging and can be used to manage service throughput and parental expectation for return of their fetus.

Advances in knowledge

A simple equation from empirical data can now be used to estimate preparation time for human fetal postmortem micro-CT imaging.

Micro-CT and high-field MRI for studying very early post-mortem human fetal anatomy at 8 weeks of gestation

OBJECTIVE

This study involved very early post-mortem (PM) examination of human fetal anatomy at 8 weeks of gestation (WG) using whole-body multimodal micro-imaging: micro-CT and high-field MRI (HF-MRI). We discuss the potential place of this imaging in early first-trimester virtual autopsy.

METHODS

We performed micro-CT after different contrast-bath protocols including diffusible iodine-based contrast-enhanced (dice) and HF-MRI with a 9.4 T machine with qualitative and quantitative evaluation and obtained histological sections.

RESULTS

Nine fetuses were included: the crown-rump length was 10-24 mm and corresponded to 7 and 9 WG according to the Robinson formula. The Carnegie stages were 17-21. Dice micro-CT and HF-MRI presented high signal to noise ratio, >5, according to the Rose criterion, and for allowed anatomical phenotyping in these specimens. Imaging did not alter the histology, allowing immunostaining and pathological examination.

CONCLUSION

PM non-destructive whole-body multimodal micro-imaging: dice micro-CT and HF-MRI allows for PM human fetal anatomy study as early as 8 WG. It paves the way to virtual autopsy in the very early first trimester. Obtaining a precision phenotype, even regarding miscarriage products, allows a reverse phenotyping to select variants of interest in genome-wide analysis, offering potential genetic counseling for bereaved parents.

Postmortem MR in termination of pregnancy for central nervous system (CNS) anomalies

OBJECTIVES

To evaluate the concordance of conventional autopsy (CA) and postmortem magnetic resonance (MR) after termination of pregnancy (TOP) in fetuses with prenatally detected central nervous system (CNS) anomalies. Second, to determine the most informative postmortem investigation in parental counseling.

METHODS

All TOPs between 2006 and 2016 with prenatally detected CNS involvement and having a postmortem MR and CA as postmortem examinations were retrospectively analyzed and concordance levels were established.

RESULTS

Of 764 TOPs, 255 cases had a CNS anomaly detected prenatally (33.4%). Fetal genetic anomalies (n = 40) and cases without both postmortem MR and CA were excluded, leaving 68 cases for analysis.Disagreement between postmortem MR and CA was observed in 22 cases (32.4%). In eight cases (11.8%), more information was obtained by CA compared with MR. However, only two cases with major additional findings were found when compared with prenatal diagnosis. In 14 cases (20.6%), MR was superior to CA either because of additional cerebral anomalies undetected by CA (n = 5) and/or because of severe autolysis hindering pathology of the CNS (n = 9).

CONCLUSIONS

Our data point out that an adequate postmortem evaluation, valuable in parental counseling, can be provided by a postmortem MR in 97% of the cases.Key PointsAn adequate postmortem evaluation, valuable in parental counseling, can be provided by a postmortem (PM) magnetic resonance (MR) in the majority of cases.PM MR is an excellent postmortem imaging tool for the brain.In cases with brain autolysis, PM MR is often the only informative PM investigation tool.PM MR is an essential adjunct to CA in the PM evaluation of pregnancies terminated for a central nervous system (CNS) anomaly.

Multidimensional Analysis of the Adult Human Heart in Health and Disease using Hierarchical Phase-Contrast Tomography (HiP-CT)

Cardiovascular diseases (CVDs) are a leading cause of death worldwide. Current clinical imaging modalities provide resolution adequate for diagnosis but are unable to provide detail of structural changes in the heart, across length-scales, necessary for understanding underlying pathophysiology of disease. Hierarchical Phase-Contrast Tomography (HiP-CT), using new (4th) generation synchrotron sources, potentially overcomes this limitation, allowing micron resolution imaging of intact adult organs with unprecedented detail. In this proof of principle study (n=2), we show the utility of HiP-CT to image whole adult human hearts ex-vivo: one 'control' without known cardiac disease and one with multiple known cardiopulmonary pathologies. The resulting multiscale imaging was able to demonstrate exemplars of anatomy in each cardiac segment along with novel findings in the cardiac conduction system, from gross (20 um/voxel) to cellular scale (2.2 um/voxel), non-destructively, thereby bridging the gap between macroscopic and microscopic investigations. We propose that the technique represents a significant step in virtual autopsy methods for studying structural heart disease, facilitating research into abnormalities across scales and age-groups. It opens up possibilities for understanding and treating disease; and provides a cardiac 'blueprint' with potential for in-silico simulation, device design, virtual surgical training, and bioengineered heart in the future.

Exploring the Role of Modified Vascular Anatomical Molding (MVAM) in Prenatal Diagnosis Teaching and Prognosis Prediction of Fetal Complex Congenital Heart Disease (CCHD): A Preliminary Study

Objective

The present study aimed to explore the role of modified vascular anatomical molding (MVAM) in prenatal diagnosis teaching and prognosis prediction of fetal complex congenital heart disease (CCHD).

Methods

Step 1, MVAM method was used to cast the micro-blood vessels and trachea of 52 CCHD specimens. Subsequently, 52 MVAMs were analyzed and compared with the prenatal ultrasound to summarize their characteristics, misdiagnosis and MVAM's teaching role. Step 2, the surgical and follow-up data of 206 CCHD cases were retrospectively analyzed. Cases that evolved into critical illnesses or died within 1-3 years after surgery (poor prognosis) were classified into the study group (n = 77) and those with good prognosis into the control group (n = 129), which were split into the training set and the test set in the ratio 7:3 based on the time cut-off. In the training set, the prognosis of CCHD was predicted using the MVAM anatomical soft markers (distortion and narrowing of aorta/pulmonary artery, right ventricular infundibulum, etc.) and the decision curve analysis (DCA) performed. The model was validated using the test set, and a nomogram was finally established.

Results

It was observed that all 52 CCHD cases were confirmed using MVAM. A total of 91 cardiac malformations were recorded, among which 41 malformations were misdiagnosed, and 29 malformations were missed by the prenatal echocardiography. The MVAM method has a good teaching/feedback effect on prenatal diagnosis. The combined model exhibited a higher predictive performance in the training- and test-set. Its high clinical net benefit was proved by DCA. Additionally, the nomogram established using the combined model received a favorable response in clinical practice.

Conclusion

The research results indicated that MVAM improved the prenatal diagnosis teaching and training performance. The combined model established based on MVAM anatomical soft markers can offer a high clinical significance for prognosis prediction of CCHD.

Ultra-high-field MRI of postmortem human fetal wrist joints: initial experience

BACKGROUND

This study aimed to assess the feasibility of postmortem ultra-high-field magnetic resonance imaging (UHF-MRI) to study fetal musculoskeletal anatomy and explore the contribution of variation in iodine and formaldehyde (paraformaldehyde, PFA) treatment of tissue.

METHODS

Seven upper extremities from human fetuses with gestational ages of 19 to 24 weeks were included in this experimental study, approved by the Medical Research Ethics Committee. The specimens were treated with various storage (0.2-4% PFA) and staining (Lugol's solution) protocols and the wrist joint was subsequently imaged with 7.0 T UHF-MRI. Soft-tissue contrast was quantified by determining regions of interest within a chondrified carpal bone (CCB) from the proximal row, the triangular fibrocartilage (TFC), and the pronator quadratus muscle (PQM) and calculating the contrast ratios (CRs) between mean signal intensities of CCB to TFC and CCB to PQM.

RESULTS

UHF-MRI showed excellent soft-tissue contrast in different musculoskeletal tissues. Increasing storage time in 4% PFA, CRs decreased, resulting in a shift from relatively hyperintense to hypointense identification of the CCB. Storage in 0.2% PFA barely influenced the CRs over time. Lugol's solution caused an increase in CRs and might have even contributed to the inversion of the CRs.

CONCLUSIONS

UHF-MRI is a feasible technique to image musculoskeletal structures in fetal upper extremities and most successful after short storage in 4% PFA or prolonged storage in 0.2% PFA. The use of Lugol's solution is not detrimental on soft-tissue MRI contrast and therefore enables effectively combining UHF-MRI with contrast-enhanced micro-computed tomography using a single preparation of the specimen.

RELEVANCE STATEMENT

UHF-MRI can be performed after CE-micro-CT to take advantage of both techniques.

KEY POINTS

• UHF-MRI is feasible to study human fetal cartilaginous and ligamentous anatomy. • Storage in low PFA concentrations (i.e., 0.2%) improves soft-tissue contrast in UHF-MRI. • Limited preservation time in high concentrations of PFA improves soft-tissue contrast in UHF-MRI. • Prior staining with Lugol's solution does not reduce soft-tissue contrast in UHF-MRI.

Less-invasive autopsy for early pregnancy loss

Autopsy investigations provide valuable information regarding fetal death that can assist in the parental bereavement process, and influence future pregnancies, but conventional autopsy is often declined by parents because of its invasive approach. This has led to the development of less-invasive autopsy investigations based on imaging technology to provide a more accessible and acceptable choice for parents when investigating their loss. Whilst the development and use of more conventional clinical imaging techniques (radiographs, CT, MRI, US) are well described in the literature for fetuses over 20 weeks of gestational age, these investigations have limited diagnostic accuracy in imaging smaller fetuses. Techniques such as ultra-high-field MRI (>3T) and micro-focus computed tomography have been shown to have higher diagnostic accuracy whilst still being acceptable to parents. By further developing and increasing the availability of these more innovative imaging techniques, parents will be provided with a greater choice of acceptable options to investigate their loss, which may in turn increase their uptake. We provide a narrative review focussing on the development of high-resolution, non-invasive imaging techniques to evaluate early gestational pregnancy loss.

Confirmation of Heart Malformations in Fetuses in the First Trimester Using Three-Dimensional Histologic Autopsy

BACKGROUND

We aimed to evaluate the usefulness of three-dimensional (3D) reconstruction of histology slides to confirm congenital heart disease (CHD) detected by first-trimester fetal cardiac ultrasonography. Conventional autopsy is hindered by the small size of the first-trimester fetal heart, and current CHD confirmation studies employ the use of highly specialized and expensive methods.

TECHNIQUE

An extended first-trimester ultrasound examination protocol was used to diagnose fetal heart anomalies. Medical termination of pregnancies was followed by fetal heart extraction. The specimens were sliced, and the histology slides were stained and scanned. The resulting images were processed, and volume rendering was performed using 3D reconstruction software. The volumes were analyzed by a multidisciplinary team of maternal-fetal medicine subspecialists and pathologists and compared with ultrasound examination findings.

EXPERIENCE

Six fetuses with heart malformations were evaluated using histologic 3D imaging: two with hypoplastic left heart syndrome, two with atrioventricular septal defects, one with an isolated ventricular septal defect, and one with transposition of the great arteries. The technique allowed us to confirm ultrasound-detected anomalies and also identified additional malformations.

CONCLUSION

After pregnancy termination or loss, histologic 3D imaging can be used to confirm the presence of fetal cardiac malformations detected during first-trimester ultrasound examination. Additionally, this technique has the potential to refine the diagnosis for counseling regarding recurrence risk and retains the advantages of standard histology.

Microfocus computed tomography for fetal postmortem imaging: an overview

Over the last few years, fetal postmortem microfocus computed tomography (micro-CT) imaging has increased in popularity for both diagnostic and research purposes. Micro-CT imaging could be a substitute for autopsy, particularly in very early gestation fetuses for whom autopsy can be technically challenging and is often unaccepted by parents. This article provides an overview of the latest research in fetal postmortem micro-CT imaging with a focus on diagnostic accuracy, endovascular staining approaches, placental studies and the reversibility of staining. It also discusses new methods that could prove helpful for micro-CT of larger fetuses. While more research is needed, contrast-enhanced micro-CT has the potential to become a suitable alternative to fetal autopsy. Further research using this novel imaging tool could yield wider applications, such as its practise in imaging rare museum specimens.

Volumetric Tissue Imaging of Surgical Tissue Specimens Using Micro-Computed Tomography: An Emerging Digital Pathology Modality for Nondestructive, Slide-Free Microscopy-Clinical Applications of Digital Pathology in 3 Dimensions

OBJECTIVES

Micro-computed tomography (micro-CT) is a novel, nondestructive, slide-free digital imaging modality that enables the acquisition of high-resolution, volumetric images of intact surgical tissue specimens. The aim of this systematic mapping review is to provide a comprehensive overview of the available literature on clinical applications of micro-CT tissue imaging and to assess its relevance and readiness for pathology practice.

METHODS

A computerized literature search was performed in the PubMed, Scopus, Web of Science, and CENTRAL databases. To gain insight into regulatory and financial considerations for performing and examining micro-CT imaging procedures in a clinical setting, additional searches were performed in medical device databases.

RESULTS

Our search identified 141 scientific articles published between 2000 and 2021 that described clinical applications of micro-CT tissue imaging. The number of relevant publications is progressively increasing, with the specialties of pulmonology, cardiology, otolaryngology, and oncology being most commonly concerned. The included studies were mostly performed in pathology departments. Current micro-CT devices have already been cleared for clinical use, and a Current Procedural Terminology (CPT) code exists for reimbursement of micro-CT imaging procedures.

CONCLUSIONS

Micro-CT tissue imaging enables accurate volumetric measurements and evaluations of entire surgical specimens at microscopic resolution across a wide range of clinical applications.

OCT Meets micro-CT: A Subject-Specific Correlative Multimodal Imaging Workflow for Early Chick Heart Development Modeling

Structural and Doppler velocity data collected from optical coherence tomography have already provided crucial insights into cardiac morphogenesis. X-ray microtomography and other ex vivo methods have elucidated structural details of developing hearts. However, by itself, no single imaging modality can provide comprehensive information allowing to fully decipher the inner workings of an entire developing organ. Hence, we introduce a specimen-specific correlative multimodal imaging workflow combining OCT and micro-CT imaging which is applicable for modeling of early chick heart development—a valuable model organism in cardiovascular development research. The image acquisition and processing employ common reagents, lab-based micro-CT imaging, and software that is free for academic use. Our goal is to provide a step-by-step guide on how to implement this workflow and to demonstrate why those two modalities together have the potential to provide new insight into normal cardiac development and heart malformations leading to congenital heart disease.

Forensic applications of micro-computed tomography: a systematic review

Purpose

The aim of this systematic review was to provide a comprehensive overview of micro-CT current applications in forensic pathology, anthropology, odontology, and neonatology.

Methods

A bibliographic research on the electronic databases Pubmed and Scopus was conducted in the time frame 01/01/2001–31/12/2021 without any language restrictions and applying the following free-text search strategy: “(micro-computed tomography OR micro-CT) AND (forensic OR legal)”. The following inclusion criteria were used: (A) English language; (B) Application of micro-CT to biological and/or non-biological materials to address at least one forensic issue (e.g., age estimation, identification of post-mortem interval). The papers selected by three independent investigators have been then classified according to the investigated materials.

Results

The bibliographic search provided 651 records, duplicates excluded. After screening for title and/or abstracts, according to criteria A and B, 157 full-text papers were evaluated for eligibility. Ninety-three papers, mostly (64) published between 2017 and 2021, were included; considering that two papers investigated several materials, an overall amount of 99 classifiable items was counted when referring to the materials investigated. It emerged that bones and cartilages (54.55%), followed by teeth (13.13%), were the most frequently analyzed materials. Moreover, micro-CT allowed the collection of structural, qualitative and/or quantitative information also for soft tissues, fetuses, insects, and foreign materials.

Conclusion

Forensic applications of micro-CT progressively increased in the last 5 years with very promising results. According to this evidence, we might expect in the near future a shift of its use from research purposes to clinical forensic cases.

Postmortem Micro-CT of Human Fetal Heart-A Systematic Literature Review

Micro-computed tomography (CT) is a non-invasive alternative to conventional macroscopic dissection for the evaluation of human fetal cardiac anatomy. This paper aims to systematically review the literature regarding the use of micro-CT to examine human fetal hearts, to illustrate its educational and research implications and to explain its possible directions for the future. A systematic literature review was conducted following the PRISMA statement to identify publications concerning micro-CT applications for the isolated human fetal heart. The search strategy identified nine eligible studies. Micro-CT is technically feasible for postmortem examination of the human fetal heart coming from early and late termination of pregnancy. It reaches high diagnostic accuracy, and it seems to perform better than autopsy in small samples or in the case of early termination of pregnancy. Applications derived from micro-CT allow multiple off-time evaluations and interdisciplinary comparisons for educational purposes and research perspectives in biological and bioengineering domains.

Reducing soft-tissue shrinkage artefacts caused by staining with Lugol's solution

Diffusible iodine-based contrast-enhanced computed tomography (diceCT) is progressively used in clinical and morphological research to study developmental anatomy. Lugol’s solution (Lugol) has gained interest as an effective contrast agent; however, usage is limited due to extensive soft-tissue shrinkage. The mechanism of Lugol-induced shrinkage and how to prevent it is largely unknown, hampering applications of Lugol in clinical or forensic cases where tissue shrinkage can lead to erroneous diagnostic conclusions. Shrinkage was suggested to be due to an osmotic imbalance between tissue and solution. Pilot experiments pointed to acidification of Lugol, but the relation of acidification and tissue shrinkage was not evaluated. In this study, we analyzed the relation between tissue shrinkage, osmolarity and acidification of the solution during staining. Changes in tissue volume were measured on 2D-segmented magnetic resonance and diceCT images using AMIRA software. Partial correlation and stepwise regression analysis showed that acidification of Lugol is the main cause of tissue shrinkage. To prevent acidification, we developed a buffered Lugol’s solution (B-Lugol) and showed that stabilizing its pH almost completely prevented shrinkage without affecting staining. Changing from Lugol to B-Lugol is a major improvement for clinical and morphological research and only requires a minor adaptation of the staining protocol.

Micro-CT yields high image quality in human fetal post-mortem imaging despite maceration

BACKGROUND

Current clinical post-mortem imaging techniques do not provide sufficiently high-resolution imaging for smaller fetuses after pregnancy loss. Post-mortem micro-CT is a non-invasive technique that can deliver high diagnostic accuracy for these smaller fetuses. The purpose of the study is to identify the main predictors of image quality for human fetal post-mortem micro-CT imaging.

METHODS

Human fetuses were imaged using micro-CT following potassium tri-iodide tissue preparation, and axial head and chest views were assessed for image quality on a Likert scale by two blinded radiologists. Simple and multivariable linear regression models were performed with demographic details, iodination, tissue maceration score and imaging parameters as predictor variables.

RESULTS

258 fetuses were assessed, with median weight 41.7 g (2.6-350 g) and mean gestational age 16 weeks (11-24 weeks). A high image quality score (> 6.5) was achieved in 95% of micro-CT studies, higher for the head (median = 9) than chest (median = 8.5) imaging. The strongest negative predictors of image quality were increasing maceration and body weight (p < 0.001), with number of projections being the best positive imaging predictor.

CONCLUSIONS

High micro-CT image quality score is achievable following early pregnancy loss despite fetal maceration, particularly in smaller fetuses where conventional autopsy may be particularly challenging. These findings will help establish clinical micro-CT imaging services, addressing the need for less invasive fetal autopsy methods.

Micro-CT processing's effects on microscopic appearance of human fetal cardiac samples

Higher resolution than common computed tomography has been reached through Micro-Computed Tomography (micro-CT) on small samples. Emerging forensic applications of micro-CT are the study of fetal/infant organs and whole fetuses, and their two/three-dimension reconstruction; it allows: to facilitate pathologists' role in the identification of causes of fetal stillbirth and of infant death; to create digital two and/or three-dimension representations of fetal/infant organs and whole fetuses which can be easily discussed in civil and/or penal courts. Micro-CT reconstructs cardiac anatomy of animal and human sample. There are no studies that are specifically aimed to evaluate possible effects of micro-CT processing on cardiac microscopic evaluation. This study analyzed microscopic effects of micro-CT processing on human-fetal-hearts. After processing with Lugol-solution or Microfil-MV-122-injection in coronary branches, fetal hearts underwent micro-CT scan. Then, hearts were microscopically analyzed using hematoxylin/eosin, trichrome, immunohistochemistry (IHC) for actin-protein, and IHC for desmin-intermediate-filament stains. In all cases staining was present in all fields. In all slides, disarranged myocardial proteins with increase of inter filaments and inter cellular spaces was reported. This manuscript allowed to observe post micro-CT appropriate staining and antigenic reactivity, and to identify cytoarchitecture modifications that could compromise slides' microscopic evaluation. It also highlighted a possible role of micro-CT determining this cytoarchitecture phenomenon.

Current clinical applications and potential perspective of micro-computed tomography in cardiovascular imaging: A systematic scoping review

Micro-computed tomography (micro-CT) constitutes an emerging imaging technique, which can be utilized in cardiovascular medicine to study in-detail the microstructure of heart and vessels. This paper aims to systematically review the clinical utility of micro-CT in cardiovascular imaging and propose future applications of micro-CT imaging in cardiovascular research. A systematic scoping review was conducted by searching for original studies written in English according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews. Medline, Scopus, ClinicalTrials.gov, and the Cochrane library were systematically searched through December 11, 2020 to identify publications concerning micro-CT applications in cardiovascular imaging. Preclinical-animal studies and case reports were excluded. The Newcastle-Ottawa assessment scale for observational studies was used to evaluate study quality. In total, the search strategy identified 30 studies that report on micro-CT-based cardiovascular imaging and satisfy our eligibility criteria. Across all included studies, the total number of micro-CT scanned specimens was 1,227. Six studies involved postmortem 3D-reconstruction of congenital heart defects, while eleven studies described atherosclerotic vessel (coronary or carotid) characteristics. Thirteen other studies employed micro-CT for the assessment of medical devices (mainly stents or prosthetic valves). In conclusion, micro-CT is a novel imaging modality, effectively adapted for the 3D visualization and analysis of cardiac soft tissues and devices at high spatial resolution. Its increasing use could make significant contributions to our improved understanding of the histopathophysiology of cardiovascular diseases, and, thus, has the potential to optimize interventional procedures and technologies, and ultimately improve patient outcomes.

Human fetal whole-body postmortem microfocus computed tomographic imaging

Perinatal autopsy is the standard method for investigating fetal death; however, it requires dissection of the fetus. Human fetal microfocus computed tomography (micro-CT) provides a generally more acceptable and less invasive imaging alternative for bereaved parents to determine the cause of early pregnancy loss compared with conventional autopsy techniques. In this protocol, we describe the four main stages required to image fetuses using micro-CT. Preparation of the fetus includes staining with the contrast agent potassium triiodide and takes 3-19 d, depending on the size of the fetus and the time taken to obtain consent for the procedure. Setup for imaging requires appropriate positioning of the fetus and takes 1 h. The actual imaging takes, on average, 2 h 40 min and involves initial test scans followed by high-definition diagnostic scans. Postimaging, 3 d are required to postprocess the fetus, including removal of the stain, and also to undertake artifact recognition and data transfer. This procedure produces high-resolution isotropic datasets, allowing for radio-pathological interpretations to be made and long-term digital archiving for re-review and data sharing, where required. The protocol can be undertaken following appropriate training, which includes both the use of micro-CT techniques and handling of postmortem tissue.

A Review of Ex Vivo X-ray Microfocus Computed Tomography-Based Characterization of the Cardiovascular System

Cardiovascular malformations and diseases are common but complex and often not yet fully understood. To better understand the effects of structural and microstructural changes of the heart and the vasculature on their proper functioning, a detailed characterization of the microstructure is crucial. In vivo imaging approaches are noninvasive and allow visualizing the heart and the vasculature in 3D. However, their spatial image resolution is often too limited for microstructural analyses, and hence, ex vivo imaging is preferred for this purpose. Ex vivo X-ray microfocus computed tomography (microCT) is a rapidly emerging high-resolution 3D structural imaging technique often used for the assessment of calcified tissues. Contrast-enhanced microCT (CE-CT) or phase-contrast microCT (PC-CT) improve this technique by additionally allowing the distinction of different low X-ray-absorbing soft tissues. In this review, we present the strengths of ex vivo microCT, CE-CT and PC-CT for quantitative 3D imaging of the structure and/or microstructure of the heart, the vasculature and their substructures in healthy and diseased state. We also discuss their current limitations, mainly with regard to the contrasting methods and the tissue preparation.

Postmortem microfocus computed tomography for noninvasive autopsies: experience in >250 human fetuses

Background

Noninvasive imaging autopsy alternatives for fetuses weighing <500 grams are limited. Microfocus computed tomography has been reported as a viable option in small case series with the potential to avoid an invasive autopsy. Implementation of postmortem microfocus computed tomography in a large cohort as part of routine clinical service has yet been unreported, and realistic “autopsy prevention rates” are unknown.

Objective

This study aimed to describe the range of abnormalities detectable on fetal microfocus computed tomography in a clinical setting and additional findings identified on the antenatal ultrasound and to estimate the invasive autopsy avoidance rate (ie, cases in which imaging was sufficient to deem autopsy unnecessary).

Study Design

A prospective observational case series of all fetuses referred for microfocus computed tomography imaging at a single institution was conducted for 3 years (2016–2019). Imaging was reported by 2 pediatric radiologists before autopsy, with “decision to proceed” based on the specialist perinatal pathologists’ judgment and parental consent. Agreement rates between microfocus computed tomography and antenatal ultrasound were evaluated, and where feasible, diagnostic accuracy for microfocus computed tomography was calculated using autopsy as a reference standard.

Results

A total of 268 fetuses were included (2–350 grams body weight; 11–24 weeks’ gestation), with cause for demise in 122 of 268 (45.5%). Of the 122 fetuses, 64 (52.5%) exhibited fetal anomalies. Although 221 of 268 (82.5%) fetuses had consent for invasive autopsy, only 29 of the 221 (13.1%) underwent this procedure, which implied an autopsy avoidance rate of 192 of 221 (86.9%). Complete agreement was present for all brain, thoracic, and abdominal pathologies, whereas sensitivity and specificity for cardiac anomalies were 66.7% and 91.7%, respectively. Microfocus computed tomography and antenatal ultrasound agreement was found in 219 of 266 cases (81.9%), with partial agreement in 21 of 266 (7.9%) and disagreement in 26 of 266 (10.5%), mostly because of additional cardiac, soft tissue, or genitourinary findings by microfocus computed tomography, which were not seen on the ultrasound.

Conclusion

Fetal microfocus computed tomography imaging is a viable and useful tool for imaging early gestational fetuses and can avoid the need for invasive autopsy. Confirmation of antenatal diagnoses is achieved in most cases, and additional anomalies may also be detected.

Micro-computed tomography (micro-CT) for the assessment of myocardial disarray, fibrosis and ventricular mass in a feline model of hypertrophic cardiomyopathy

Micro-computed tomography (micro-CT) is a high-resolution imaging modality that provides accurate tissue characterization. Hypertrophic cardiomyopathy (HCM) occurs as a spontaneous disease in cats, and is characterized by myocardial hypertrophy, disarray and fibrosis, as in humans. While hypertrophy/mass (LVM) can be objectively measured, fibrosis and myocyte disarray are difficult to assess. We evaluated the accuracy of micro-CT for detection and quantification of myocardial disarray and fibrosis by direct comparison with histopathology. 29 cat hearts (12 normal and 17 HCM hearts) underwent micro-CT and pathologic examination. Myocyte orientation was assessed using structure tensor analysis by determination of helical angle (HA), fractional anisotropy (FA) and myocardial disarray index (MDI). Fibrosis was segmented and quantified based on comparison of gray-scale values in normal and fibrotic myocardium. LVM was obtained by determining myocardial volume. Myocardial segments with low FA, low MDI and disruption of normal HA transmural profile on micro-CT were associated with myocardial disarray on histopathology. FA was consistently lower in HCM than normal hearts. Assessment of fibrosis on micro-CT closely matched the histopathologic evaluation. LVM determined by micro-CT was higher in HCM than normal hearts. Micro-CT can be used to detect and quantify myocardial disarray and fibrosis and determine myocardial mass in HCM.

Micro-computed tomography (micro-CT) for the assessment of myocardial disarray, fibrosis and ventricular mass in a feline model of hypertrophic cardiomyopathy

Micro-computed tomography (micro-CT) is a high-resolution imaging modality that provides accurate tissue characterization. Hypertrophic cardiomyopathy (HCM) occurs as a spontaneous disease in cats, and is characterized by myocardial hypertrophy, disarray and fibrosis, as in humans. While hypertrophy/mass (LVM) can be objectively measured, fibrosis and myocyte disarray are difficult to assess. We evaluated the accuracy of micro-CT for detection and quantification of myocardial disarray and fibrosis by direct comparison with histopathology. 29 cat hearts (12 normal and 17 HCM hearts) underwent micro-CT and pathologic examination. Myocyte orientation was assessed using structure tensor analysis by determination of helical angle (HA), fractional anisotropy (FA) and myocardial disarray index (MDI). Fibrosis was segmented and quantified based on comparison of gray-scale values in normal and fibrotic myocardium. LVM was obtained by determining myocardial volume. Myocardial segments with low FA, low MDI and disruption of normal HA transmural profile on micro-CT were associated with myocardial disarray on histopathology. FA was consistently lower in HCM than normal hearts. Assessment of fibrosis on micro-CT closely matched the histopathologic evaluation. LVM determined by micro-CT was higher in HCM than normal hearts. Micro-CT can be used to detect and quantify myocardial disarray and fibrosis and determine myocardial mass in HCM.

Fetal postmortem imaging: an overview of current techniques and future perspectives

Fetal death because of miscarriage, unexpected intrauterine fetal demise, or termination of pregnancy is a traumatic event for any family. Despite advances in prenatal imaging and genetic diagnosis, conventional autopsy remains the gold standard because it can provide additional information not available during fetal life in up to 40% of cases and this by itself may change the recurrence risk and hence future counseling for parents. However, conventional autopsy is negatively affected by procedures involving long reporting times because the fetal brain is prone to the effect of autolysis, which may result in suboptimal examinations, particularly of the central nervous system. More importantly, fewer than 50%-60% of parents consent to invasive autopsy, mainly owing to the concerns about body disfigurement. Consequently, this has led to the development of noninvasive perinatal virtual autopsy using imaging techniques. Because a significant component of conventional autopsy involves the anatomic examination of organs, imaging techniques such as magnetic resonance imaging, ultrasound, and computed tomography are possible alternatives. With a parental acceptance rate of nearly 100%, imaging techniques as part of postmortem examination have become widely used in recent years in some countries. Postmortem magnetic resonance imaging using 1.5-Tesla magnets is the most studied technique and offers an overall diagnostic accuracy of 77%-94%. It is probably the best choice as a virtual autopsy technique for fetuses >20 weeks' gestation. However, for fetuses <20 weeks' gestation, its performance is poor. The use of higher magnetic resonance imaging magnetic fields such as 3-Tesla may slightly improve performance. Of note, in cases of fetal maceration, magnetic resonance imaging may offer diagnoses in a proportion of brain lesions wherein conventional autopsy fails. Postmortem ultrasound examination using a high-frequency probe offers overall sensitivity and specificity of 67%-77% and 74%-90%, respectively, with the advantage of easy access and affordability. The main difference between postmortem ultrasound and magnetic resonance imaging relates to their respective abilities to obtain images of sufficient quality for a confident diagnosis. The nondiagnostic rate using postmortem ultrasound ranges from 17% to 30%, depending on the organ examined, whereas the nondiagnostic rate using postmortem magnetic resonance imaging in most situations is far less than 10%. For fetuses ≤20 weeks' gestation, microfocus computed tomography achieves close to 100% agreement with autopsy and is likely to be the technique of the future in this subgroup. The lack of histology has always been listed as 1 limitation of all postmortem imaging techniques. Image-guided needle tissue biopsy coupled with any postmortem imaging can overcome this limitation. In addition to describing the diagnostic accuracy and limitations of each imaging technology, we propose a novel, stepwise diagnostic approach and describe the possible application of these techniques in clinical practice as an alternative or an adjunct or for triage to select cases that would specifically benefit from invasive examination, with the aim of reducing parental distress and pathologist workload. The widespread use of postmortem fetal imaging is inevitable, meaning that hurdles such as specialized training and dedicated financing must be overcome to improve access to these newer, well-validated techniques.

Cardiac multi-scale investigation of the right and left ventricle ex vivo: a review

The heart is a complex multi-scale system composed of components integrated at the subcellular, cellular, tissue and organ levels. The myocytes, the contractile elements of the heart, form a complex three-dimensional (3D) network which enables propagation of the electrical signal that triggers the contraction to efficiently pump blood towards the whole body. Cardiovascular diseases (CVDs), a major cause of mortality in developed countries, often lead to cardiovascular remodeling affecting cardiac structure and function at all scales, from myocytes and their surrounding collagen matrix to the 3D organization of the whole heart. As yet, there is no consensus as to how the myocytes are arranged and packed within their connective tissue matrix, nor how best to image them at multiple scales. Cardiovascular imaging is routinely used to investigate cardiac structure and function as well as for the evaluation of cardiac remodeling in CVDs. For a complete understanding of the relationship between structural remodeling and cardiac dysfunction in CVDs, multi-scale imaging approaches are necessary to achieve a detailed description of ventricular architecture along with cardiac function. In this context, ventricular architecture has been extensively studied using a wide variety of imaging techniques: ultrasound (US), optical coherence tomography (OCT), microscopy (confocal, episcopic, light sheet, polarized light), magnetic resonance imaging (MRI), micro-computed tomography (micro-CT) and, more recently, synchrotron X-ray phase contrast imaging (SR X-PCI). Each of these techniques have their own set of strengths and weaknesses, relating to sample size, preparation, resolution, 2D/3D capabilities, use of contrast agents and possibility of performing together with in vivo studies. Therefore, the combination of different imaging techniques to investigate the same sample, thus taking advantage of the strengths of each method, could help us to extract the maximum information about ventricular architecture and function. In this review, we provide an overview of available and emerging cardiovascular imaging techniques for assessing myocardial architecture ex vivo and discuss their utility in being able to quantify cardiac remodeling, in CVDs, from myocyte to whole organ.

Investigation of optimal sample preparation conditions with potassium triiodide and optimal imaging settings for microfocus computed tomography of excised cat hearts

OBJECTIVE

To determine optimal sample preparation conditions with potassium triiodide (I₂KI) and optimal imaging settings for microfocus CT (micro-CT) of excised cat hearts.

SAMPLE

7 excised hearts (weight range, 10 to 17.6 g) obtained from healthy adult cats after euthanasia by IV injection of pentobarbital sodium.

PROCEDURES

Following excision, the hearts were preserved in 10% formaldehyde solution. Six hearts were immersed in 1.25% I₂KI solution (n = 3) or 2.5% I₂KI solution (3) for a 12-day period. Micro-CT images were acquired at time 0 (prior to iodination) then approximately every 24 and 48 hours thereafter to determine optimal sample preparation conditions (ie, immersion time and concentration of I₂KI solution). Identified optimal conditions were then used to prepare the seventh heart for imaging; changes in voltage, current, exposure time, and gain on image quality were evaluated to determine optimal settings (ie, maximal signal-to-noise and contrast-to-noise ratios). Images were obtained at a voxel resolution of 30 μm. A detailed morphological assessment of the main cardiac structures of the seventh heart was then performed.

RESULTS

Immersion in 2.5% I₂KI solution for 48 hours was optimal for sample preparation. The optimal imaging conditions included a tube voltage of 100 kV, current of 150 μA, and exposure time of 354 milliseconds; scan duration was 12 minutes.

CONCLUSIONS AND CLINICAL RELEVANCE

Results provided an optimal micro-CT imaging protocol for excised cat hearts prepared with I₂KI solution that could serve as a basis for future studies of micro-CT for high resolution 3-D imaging of cat hearts.

Proportional vascularization along the fallopian tubes and ovarian fimbria: assessment by confocal microtomography

Objective

To evaluate and reconstruct three-dimensional images of vascularization along the fallopian tube (FT), as well as to determine its relationship with the ovary and ovarian fimbria, and to quantify the blood vessels along the FT according to its anatomical segments, using confocal microtomography (micro-CT).

Materials and Methods

Nine specimens (six FTs and three FTs with ovaries) were fixed in a solution of 10% formalin for > 24 h at room temperature. Iodine staining was performed by soaking the specimens in 10% Lugol’s solution for 24 h. All specimens were evaluated using micro-CT. A morphometric analysis was performed on the reconstructed images to quantify the vascular distribution along the FT.

Results

In the FTs evaluated, the density of blood vessels was significantly greater in the fimbrial segments than in the isthmic segments (p < 0.05). The ovarian fimbria was clearly identified, demonstrating the important relationship between these vessels and the FT fimbriae.

Conclusion

We believe that the vascularization in the fimbriae is greater than and disproportional that in the other segments of FT, and that the ovarian fimbria plays an important role in the development of that difference.

Micro-computed tomography of isolated fetal hearts following termination of pregnancy: A feasibility study at 8 to 12 weeks' gestation

OBJECTIVES

To assess the feasibility of retrieval of intact human fetal hearts after first trimester surgical termination of pregnancy (TOP) and subsequent anatomical assessment by postmortem micro-computed tomography (micro-CT).

METHODS

In a cohort of consenting women undergoing surgical TOP between 8 and 13 weeks' gestation, we attempted the retrieval of the fetal heart from the suction material. Specimens were immersion fixed in 10% formaldehyde, scanned by iodine-enhanced micro-CT and cardiac anatomy assessed by a multidisciplinary team using 3D-multiplanar analysis.

RESULTS

The median gestational age at TOP was 10.7 weeks (range 8.3-12.9). In 57 (95.0%) out of 60 suction specimens, the heart could be retrieved. The median cardiac length was 5 mm (range 2-8 mm), in three (5.3%), the heart was too damaged to assess cardiac anatomy and in five (8.7%) only the four chambers could be examined. In the remaining 49 (86.0%) cases, a detailed assessment of cardiac anatomy was possible, showing a major defect in two (4.1%) and a minor defect in four (8.2%).

CONCLUSIONS

Fetal hearts can be retrieved after first trimester TOP being intact in the vast majority of cases. Iodine-enhanced, postmortem micro-CT can be used to assess cardiac anatomy from as early as 8 weeks and to describe heart abnormalities.

Novel imaging techniques to study postmortem human fetal anatomy: a systematic review on microfocus-CT and ultra-high-field MRI

Background

MRI and CT have been extensively used to study fetal anatomy for research and diagnostic purposes, enabling minimally invasive autopsy and giving insight in human fetal development. Novel (contrast-enhanced) microfocus CT (micro-CT) and ultra-high-field (≥ 7.0 T) MRI (UHF-MRI) techniques now enable micron-level resolution that combats the disadvantages of low-field MRI and conventional CT. Thereby, they might be suitable to study fetal anatomy in high detail and, in time, contribute to the postmortem diagnosis of fetal conditions.

Objectives

(1) To systematically examine the usability of micro-CT and UHF-MRI to study postmortem human fetal anatomy, and (2) to analyze factors that govern success at each step of the specimen preparation and imaging.

Method

MEDLINE and EMBASE were systematically searched to identify publications on fetal imaging by micro-CT or UHF-MRI. Scanning protocols were summarized and best practices concerning specimen preparation and imaging were enumerated.

Results

Thirty-two publications reporting on micro-CT and UHF-MRI were included. The majority of the publications focused on imaging organs separately and seven publications focused on whole body imaging, demonstrating the possibility of visualization of small anatomical structures with a resolution well below 100 μm. When imaging soft tissues by micro-CT, the fetus should be stained by immersion in Lugol’s staining solution.

Conclusion

Micro-CT and UHF-MRI are both excellent imaging techniques to provide detailed images of gross anatomy of human fetuses. The present study offers an overview of the current best practices when using micro-CT and/or UHF-MRI to study fetal anatomy for clinical and research purposes.

Key Points

• Micro-CT and UHF-MRI can both be used to study postmortem human fetal anatomy for clinical and research purposes.

• Micro-CT enables high-resolution imaging of fetal specimens in relatively short scanning time. However, tissue staining using a contrast solution is necessary to enable soft-tissue visualization.

• UHF-MRI enables high-resolution imaging of fetal specimens, without the necessity of prior staining, but with the drawback of long scanning time.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06543-8) contains supplementary material, which is available to authorized users.

Latest developments in post-mortem foetal imaging

A sustained decline in parental consent rates for perinatal autopsies has driven the development of less-invasive methods for death investigation. A wide variety of imaging modalities have been developed for this purpose and include post-mortem whole body magnetic resonance imaging (MRI), ultrasound, computed tomography (CT) and micro-focus CT techniques. These are also vital for "minimally invasive" methods, which include potential for tissue sampling, such as image guidance for targeted biopsies and laparoscopic-assisted techniques. In this article, we address the range of imaging techniques currently in clinical practice and those under development. Significant advances in high-field MRI and micro-focus CT imaging show particular promise for smaller and earlier gestation foetuses. We also review how MRI biomarkers such as diffusion-weighted imaging and organ volumetric analysis may aid diagnosis and image interpretation in the absence of autopsy data. Three-dimensional printing and augmented reality may help make imaging findings more accessible to parents, colleagues and trainees.

Complex Congenital Heart Disease Associated With Disordered Myocardial Architecture in a Midtrimester Human Fetus

BACKGROUND

In the era of increasingly successful corrective interventions in patients with congenital heart disease (CHD), global and regional myocardial remodeling are emerging as important sources of long-term morbidity/mortality. Changes in organization of the myocardium in CHD, and in its mechanical properties, conduction, and blood supply, result in altered myocardial function both before and after surgery. To gain a better understanding and develop appropriate and individualized treatment strategies, the microscopic organization of cardiomyocytes, and their integration at a macroscopic level, needs to be completely understood. The aim of this study is to describe, for the first time, in 3 dimensions and nondestructively the detailed remodeling of cardiac microstructure present in a human fetal heart with complex CHD.

METHODS AND RESULTS

Synchrotron X-ray phase-contrast imaging was used to image an archival midgestation formalin-fixed fetal heart with right isomerism and complex CHD and compare with a control fetal heart. Analysis of myocyte aggregates, at detail not accessible with other techniques, was performed. Macroanatomic and conduction system changes specific to the disease were clearly observable, together with disordered myocyte organization in the morphologically right ventricle myocardium. Electrical activation simulations suggested altered synchronicity of the morphologically right ventricle.

CONCLUSIONS

We have shown the potential of X-ray phase-contrast imaging for studying cardiac microstructure in the developing human fetal heart at high resolution providing novel insight while preserving valuable archival material for future study. This is the first study to show myocardial alterations occur in complex CHD as early as midgestation.

Micro-computed tomography: a new diagnostic tool in postmortem assessment of brain anatomy in small fetuses

PURPOSE

The aim of our study was to evaluate the postmortem micro-CT anatomy of early fetal human fetal brains, either in situ or isolated.

METHODS

We studied 12 ex vivo specimens, 9 whole human fetuses (9-18 GW), and 3 isolated samples (16-26 GW). Specimens were fixed in formalin, then immersed in Lugol solution. Images were evaluated by two neuroradiologists. The depiction of CNS structures was defined based on the comparison between micro-CT images and a reference histologic anatomical Atlas of human brain development.

RESULTS

Micro-CT provided informative high-resolution brain images in all cases, with the exception of one case (9 weeks) due to advanced maceration. All major CNS structures (i.e., brain hemispheres, layering, ventricles, germinal neuroepithelium, basal ganglia, corpus callosum, major cranial nerves, and structures of the head and neck) were recognizable.

CONCLUSIONS

Micro-CT imaging of the early fetal brain is feasible and provides high-quality images that correlate with the histological Atlas of the human brain, offering multiplanar and volumetric images that can be stored and shared for clinical, teaching, and research purposes.

Potential clinical benefits and limitations of fetal virtopsy using high-field MRI at 7 Tesla versus stereomicroscopic autopsy to assess first trimester fetuses

OBJECTIVE

The aim of this study was to establish the diagnostic accuracy of high-field magnetic resonance imaging (MRI) at 7 Tesla (T) compared with that of stereomicroscopic autopsy for assessing first trimester fetuses.

METHODS

Nine consecutive cases of first trimester fetuses resulting from spontaneous and therapeutic pregnancy termination were considered. The cases were divided into two groups according to gestational age: the Embryo Group with cases of nine to 10 gestational weeks (GWs) and the Fetus Group with cases of 13 GWs. The first group was scanned using three-dimensional fast imaging with steady state precession (3D FISP), and the second group was scanned using a two-dimensional (2D) turbo spin-echo high-resolution T2-weighted imaging (T2 WI) protocol. A radiologist and two embryologists interpreted the images. All cases were evaluated by invasive autopsy, with pathologist blinded to the imaging results. In total, the database included 270 items for evaluation (9 cases × 30 structures/case).

RESULTS

The global agreement between fetal high-field virtopsy and microscopic or stereomicroscopic autopsy was evaluated using 225 evaluation items visible by both methods. Overall, using microscopic examination and stereomicroscopic autopsy as the gold standard, fetal high-field virtopsy had a sensitivity of 94.6% [95% CI, 87.2-98.3] and a specificity of 97.6% [95% CI, 95-98.8]. The positive predictive value (PPV) was 93% [95% CI, 85.7-96.6], and the negative predictive value (NPV) was 98.2% [95% CI, 95.7-99.4]. Cohen kappa coefficient of agreement was k = 0.92 [95% CI, 0.82-0.97], and the McNemar test showed p = 1.00.

CONCLUSIONS

Virtual autopsy using high-field MRI at 7 T can be considered a safe alternative approach to stereomicroscopic autopsy for the assessment of fetal structural anomalies at the end of the first trimester of pregnancy.

Three-Dimensional Printing of Fetal Models of Congenital Heart Disease Derived From Microfocus Computed Tomography: A Case Series

This article presents a case series of n = 21 models of fetal cardiovascular anatomies obtained from post mortem microfocus computed tomography (micro-CT) data. The case series includes a broad range of diagnoses (e.g., tetralogy of Fallot, hypoplastic left heart syndrome, dextrocardia, double outlet right ventricle, atrio-ventricular septal defect) and cases also had a range of associated extra-cardiac malformations (e.g., VACTERL syndrome, central nervous system anomalies, renal anomalies). All cases were successfully reconstructed from the microfocus computed tomography data, demonstrating the feasibility of the technique and of the protocols, including in-house printing with a desktop 3D printer (Form2, Formlabs). All models were printed in 1:1 scale as well as with the 5-fold magnification, to provide insight into the intra-cardiac structures. Possible uses of the models include education and training.

Accuracy of Micro-Computed Tomography in Post-mortem Evaluation of Fetal Congenital Heart Disease. Comparison Between Post-mortem Micro-CT and Conventional Autopsy

Aims: Early prenatal diagnosis of congenital heart disease is feasible. Conventional autopsy is the current gold standard method for post-mortem confirmation. Radiologic techniques alternative to conventional autopsy, such as post-mortem micro-computed tomography, have been proposed in case of limited diagnostic accuracy (i.e., early termination of pregnancy, samples of small dimension or of low weight). The aim of the present study was to define accuracy of micro-computed tomography for post-mortem diagnosis of congenital heart disease in gross anatomy samples. Methods and Results: Fetal heart underwent in-utero prenatal echocardiography and ex-vivo post-mortem evaluation by 9 μm resolution micro-computed tomography and conventional autopsy. For each case, 25 indices of cardiac anatomy were studied by post-mortem micro-computed tomography and conventional autopsy; these were used to compare the two post mortem techniques. Ten samples were examined (gestational age between 12 + 4 and 21 + 6 weeks of gestation). Considering comparable indices, agreement between post-mortem micro-computed tomography and conventional autopsy was of 100% and sensitivity and specificity were of 100%. In "challenging specimens," post-mortem micro-computed tomography diagnoses more indices as compared to conventional autopsy and 84% of "not-diagnostic" indices at conventional autopsy would be diagnostic at post-mortem micro-computed tomography. Conclusion: Micro-computed tomography can be a valid diagnostic alternative to conventional autopsy for post-mortem evaluation of human fetal heart. In addition, it may prove superior to conventional autopsy particularly in cases coming from early termination of pregnancy or in samples of small dimension or of low weight.

In Vivo Imaging With Confirmation by Histopathology for Increased Rigor and Reproducibility in Translational Research: A Review of Examples, Options, and Resources

Preclinical noninvasive imaging can be an indispensable tool for studying animal models of disease. In vivo imaging to assess anatomical, functional, and molecular features requires verification by a comparison to the macroscopic and microscopic morphological features, since all noninvasive in vivo imaging methods have much lower resolution than standard histopathology. Comprehensive pathological evaluation of the animal model is underutilized; yet, many institutions have veterinary or human pathologists with necessary comparative pathology expertise. By performing a rigorous comparison to gross or histopathology for image interpretation, these trained individuals can assist scientists with the development of the animal model, experimental design, and evaluation of the in vivo imaging data. These imaging and pathology corroboration studies undoubtedly increase scientific rigor and reproducibility in descriptive and hypothesis-driven research. A review of case examples including ultrasound, nuclear, optical, and MRI is provided to illustrate how a wide range of imaging modalities data can be confirmed by gross or microscopic pathology. This image confirmation and authentication will improve characterization of the model and may contribute to decreasing costs and number of animals used and to more rapid translation from preclinical animal model to the clinic.

Minimally invasive fetal autopsy using ultrasound: a feasibility study

OBJECTIVES

To evaluate postmortem ultrasound (PM-US) for minimally invasive autopsy, and to demonstrate its feasibility, sensitivity and specificity, as compared with conventional autopsy, in detecting major congenital abnormalities.

METHODS

Over a 19-month study period from 1 March 2012 to 30 September 2013, we recruited from a referral hospital 88 consecutive fetuses, at 11-40 weeks' gestation, which had undergone termination, miscarriage or intrauterine fetal death. We performed PM-US using different transducers and compared the data with those from conventional autopsy. The latter was performed, according to the Societé Francaise de Foetopathologie (France) guidelines, by experienced perinatal pathologists who were blinded to the ultrasound data.

RESULTS

Complete virtual autopsy by ultrasound was possible in 95.5% of the cases. The sensitivity of PM-US for detecting brain abnormalities was 90.9% (95% CI, 58.7-99.8%) and the specificity was 87.3% (95% CI, 75.5-94.7%). In 20% of cases, a neuropathological examination was not possible due to severe maceration. The sensitivity for detection of thoracic abnormalities was 88.9% (95% CI, 65.3-98.6%) and the specificity was 92.8% (95% CI, 84.1-97.6%), and the sensitivity for detection of abdominal anomalies was 85.7% (95% CI, 57.2-98.2%) and the specificity was 94.6% (95% CI, 86.7-98.5%).

CONCLUSION

This pilot study confirms the feasibility of PM-US for virtual autopsy as early as 11 weeks' gestation. This new technique shows high sensitivity and specificity in detecting congenital structural abnormalities as compared with conventional autopsy. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.

Regulatory Forum Opinion Piece*: Imaging Applications in Toxicologic Pathology-Recommendations for Use in Regulated Nonclinical Toxicity Studies

Available imaging systems for use in preclinical toxicology studies increasingly show utility as important tools in the toxicologic pathologist's armamentarium, permit longitudinal evaluation of functional and morphological changes in tissues, and provide important information such as organ and lesion volume not obtained by conventional toxicology study parameters. Representative examples of practical imaging applications in toxicology research and preclinical studies are presented for ultrasound, positron emission tomography/single-photon emission computed tomography, optical, magnetic resonance imaging, and matrix-assisted laser desorption ionization-imaging mass spectrometry imaging. Some of the challenges for making imaging systems good laboratory practice-compliant for regulatory submission are presented. Use of imaging data on a case-by-case basis as part of safety evaluation in regulatory submissions is encouraged.

Postmortem microfocus computed tomography for early gestation fetuses: a validation study against conventional autopsy

BACKGROUND

Perinatal autopsy provides useful clinical information in up to 40% of cases. However, there is a substantial unmet clinical need with regards to postmortem investigation of early gestation fetal loss for parents for whom standard autopsy is either not available or not acceptable. Parents dislike the invasive nature of autopsy, but current clinical imaging techniques do not provide high-enough imaging resolution in small fetuses. We hypothesized that microfocus computed tomography, which is a rapid high-resolution imaging technique, could give accurate diagnostic imaging after early gestation fetal loss.

OBJECTIVE

The objective of the study was to evaluate the diagnostic accuracy of microfocus computed tomography for noninvasive human fetal autopsy for early gestation fetuses, with the use of conventional autopsy as the reference standard.

STUDY DESIGN

We compared iodinated whole body microfocus computed tomography in 20 prospectively recruited fetuses (11-21 weeks gestation from 2 centers) with conventional autopsy in a double-blinded manner for a main diagnosis and findings in specific body organs. Fetuses were prepared with 10% formalin/potassium tri-iodide. Images were acquired with a microfocus computed tomography scanner with size-appropriate parameters. Images were evaluated independently by 2 pediatric radiologists, who were blinded to formal perinatal autopsy results, across 40 individual indices to reach consensus. The primary outcome was agreement between microfocus computed tomography and conventional autopsy for overall diagnosis.

RESULTS

Postmortem whole body fetal microfocus computed tomography gave noninvasive autopsy in minutes, at a mean resolution of 27μm, with high diagnostic accuracy in fetuses at <22 weeks gestation. Autopsy demonstrated that 13 of 20 fetuses had structural abnormalities, 12 of which were also identified by microfocus computed tomography (92.3%). Overall, microfocus computed tomography agreed with overall autopsy findings in 35 of 38 diagnoses (15 true positive, 18 true negative; sensitivity 93.8% [95% confidence interval, 71.7-98.9%], specificity 100% [95% confidence interval, 82.4-100%]), with 100% agreement for body imaging diagnoses. Furthermore, after removal of nondiagnostic indices, there was agreement for 700 of 718 individual body organ indices that were assessed on microfocus computed tomography and autopsy (agreement, 97.5%; 95% confidence interval, 96.1-98.4%), with no overall differences between fetuses at ≤14 or >14 weeks gestation (agreement, 97.2% and 97.9%, respectively). Within first-trimester fetal loss cases (<14 weeks gestation), microfocus computed tomography analysis yielded significantly fewer nondiagnostic indices than autopsy examination (22/440 vs 48/348, respectively; P<.001).

CONCLUSION

Postmortem whole-body fetal microfocus computed tomography gives noninvasive, detailed anatomic examinations that are achieved in minutes at high resolution. Microfocus computed tomography may be preferable to magnetic resonance imaging in early gestation fetuses and may offer an acceptable method of examination after fetal loss for parents who decline invasive autopsy. This will facilitate autopsy and subsequent discussions between medical professionals who are involved in patient care and counselling for future pregnancies.

Three-dimensional modelling and three-dimensional printing in pediatric and congenital cardiac surgery

Three-dimensional (3D) modelling and printing methods greatly support advances in individualized medicine and surgery. In pediatric and congenital cardiac surgery, personalized imaging and 3D modelling presents with a range of advantages, e.g., better understanding of complex anatomy, interactivity and hands-on approach, possibility for preoperative surgical planning and virtual surgery, ability to assess expected results, and improved communication within the multidisciplinary team and with patients. 3D virtual and printed models often add important new anatomical findings and prompt alternative operative scenarios. For the lack of critical mass of evidence, controlled randomized trials, however, most of these general benefits remain anecdotal. For an individual surgical case-scenario, prior knowledge, preparedness and possibility of emulation are indispensable in raising patient-safety. It is advocated that added value of 3D printing in healthcare could be raised by establishment of a multidisciplinary centre of excellence (COE). Policymakers, research scientists, clinicians, as well as health care financers and local entrepreneurs should cooperate and communicate along a legal framework and established scientific guidelines for the clinical benefit of patients, and towards financial sustainability. It is expected that besides the proven utility of 3D printed patient-specific anatomical models, 3D printing will have a major role in pediatric and congenital cardiac surgery by providing individually customized implants and prostheses, especially in combination with evolving techniques of bioprinting.

Tuboperitoneal fistula, ectopic pregnancy, and remnants of fallopian tube: a confocal microtomography analysis and 3D reconstruction of human fallopian tube pathologies

Objective: The aim of this study was to provide a three-dimensional (3D) microscopic reconstruction of morphological modifications of the fallopian tube (FT) following surgical sterilization (including tuboperitoneal fistula) and ectopic pregnancy (EP) using confocal microtomography (micro-CT). Methods: Six specimens of FT from elective and emergency surgeries were selected: three remnants of the FT (RFT) from surgical sterilization, including one presenting tuboperitoneal fistula, and three FTs with EP. The specimens were fixed in formalin and stained with Lugol solution. Micro-CT studies were conducted on the specimens using protocols adapted from biological studies. Results: Three RFTs from surgical sterilization and three FTs affected by EPs were successfully scanned using micro-CT. There was good contrast impregnation, allowing tissue segmentation and analysis of different sections of the FTs. Three FT specimens from EP exhibited considerable distortion of the tubal anatomy, mainly from the blood clot in the tubal abortion. Three RFT specimens exhibited some features observed in traditional microscopy, such as tubal distension and loss of normal anatomical characteristics of a normal FT, and indicated the presence of a tuboperitoneal fistula in one of the three specimens. Conclusion: Micro-CT can identify morphological characteristics of FT pathologies previously described in a microscopic scale, with tissue contrast and the possibility of 3D reconstruction. Micro-CT is also useful in guiding traditional sectioning of specimens for histopathological studies.

Fetal Cardiac Impairment in Nitrofen-Induced Congenital Diaphragmatic Hernia: Postmortem Microcomputed Tomography Imaging Study

INTRODUCTION

We assessed the post-mortem micro-CT utility to evaluate fetal cardiac impairment in nitrofen-induced congenital diaphragmatic hernia (CDH).

METHODS

At 9.5d postconception (dpc), pregnant rats were exposed to nitrofen. At +18 and +21dpc, fetuses were harvested by cesarean section. Postmortem micro-CT and autopsy were performed. Fetuses were assigned to three experimental groups: Control group (C), Nitrofen group (N, exposition to nitrofen without CDH), CDH group. Cardio-pulmonary indices were evaluated.

RESULTS

An accurate morphological evaluation of the lung and heart was obtained. Early cardiac impairment was present in the N and CDH groups. At term pregnancy, an increased maximum diameter and decreased minimum diameter of the ventricles and increased interventricular septal thickness were noted in CDH. Histology showed a myocardial "disarray" and an high density of mitotic myocytes in CDH at midgestation.

CONCLUSIONS

The potential utility of post-mortem fetal micro-CT examination in CDH was introduced. The results highlighted the presence of cardiac adaptation in affected fetuses.

Early clinical applications for imaging at microscopic detail: microfocus computed tomography (micro-CT)

Microfocus CT (micro-CT) has traditionally been used in industry and preclinical studies, although it may find new applicability in the routine clinical setting. It can provide high-resolution three-dimensional digital imaging data sets to the same level of detail as microscopic examination without the need for tissue dissection. Micro-CT is already enabling non-invasive detailed internal assessment of various tissue specimens, particularly in breast imaging and early gestational fetal autopsy, not previously possible from more conventional modalities such as MRI or CT. In this review, we discuss the technical aspects behind micro-CT image acquisition, how early work with small animal studies have informed our knowledge of human disease and the imaging performed so far on human tissue specimens. We conclude with potential future clinical applications of this novel and emerging technique.

Back to the Future - Part 2. Post-mortem assessment and evolutionary role of the bio-medicolegal sciences

Part 2 of the review "Back to the Future" is dedicated to the evolutionary role of the bio-medicolegal sciences, reporting the historical profiles, the state of the art, and prospects for future development of the main related techniques and methods of the ancillary disciplines that have risen to the role of "autonomous" sciences, namely, Genetics and Genomics, Toxicology, Radiology, and Imaging, involved in historic synergy in the "post-mortem assessment," together with the mother discipline Legal Medicine, by way of its primary fundament, universally denominated as Forensic Pathology. The evolution of the scientific research and the increased accuracy of the various disciplines will be oriented towards the elaboration of an "algorithm," able to weigh the value of "evidence" placed at the disposal of the "justice system" as real truth and proof.

Current issues in postmortem imaging of perinatal and forensic childhood deaths

Perinatal autopsy practice is undergoing a state of change with the introduction of evidence-based cross-sectional imaging, driven primarily by parental choice. In particular, the introduction of post mortem magnetic resonance imaging (PMMR) has helped to advance less-invasive perinatal autopsy in the United Kingdom (UK) and Europe. However, there are limitations to PMMR and other imaging techniques which need to be overcome, particularly with regard to imaging very small fetuses. Imaging is also now increasingly used to investigate particular deaths in childhood, such as suspected non-accidental injury (NAI) and sudden unexpected death in infancy (SUDI). Here we focus on current topical developments the field, with particular emphasis on the application of imaging to perinatal autopsy, and pediatric forensic deaths. Different imaging modalities and their relative advantages and disadvantages are discussed, together with other benefits of more advanced cross-sectional imaging which currently lie in the research domain. Whilst variations in local imaging service provision and need may determine different practice patterns, and access to machines and professionals with appropriate expertise and experience to correctly interpret the findings may limit current practices, we propose that gold standard perinatal and pediatric autopsy services would include complete PMMR imaging prior to autopsy, with PMCT in suspicious childhood deaths. This approach would provide maximal diagnostic yield to the pathologist, forensic investigator and most importantly, the parents.

The possibilities of studying human embryos and foetuses using micro-CT: a technical note

The purpose of the study was to discover a way to study the internal structure and evolution of human embryos noninvasively. The human embryo was stained with phosphotungstic acid solution (PTA) in ethanol (EPTA) and scanned using a micro computed tomography (micro-CT) scanner. Using appropriate software, a three-dimensional image of the embryo was created, which could be further exploited. The methodology described could be used for the non-destructive examination of the internal structure of the human embryo, and the resulting data can be used as a resource for medical students, gynaecologists, and paediatricians.