Comparison of postmortem whole-body contrast-enhanced microfocus computed tomography and high-field magnetic resonance imaging of human fetuses.

OBJECTIVE: Although fetal autopsy is generally recommended to confirm or refute the antemortem diagnosis, parental acceptance of the procedure has fallen over time, mainly due to its invasiveness. Contrast-enhanced microfocus CT (micro-CT) and high-field magnetic resonance imaging (HF-MRI, ≥ 3 Tesla) have both been suggested as non-invasive alternatives to conventional fetal autopsy for fetuses < 20 weeks of gestation. The aim of this study was to compare these two modalities in postmortem whole-body fetal imaging. METHODS: In this study, the imaging process and quality of micro-CT and HF-MRI were compared using both qualitative and quantitative assessments. For the qualitative evaluation, fetal anatomy experts scored 56 HF-MRI and 56 micro-CT images of four human fetuses aged 13-18 gestational weeks on two components: overall image quality and the ability to recognize and assess 21 anatomical structures. For the quantitative evaluation, participants segmented manually three organs with increasing complexity to assess interobserver variability. In addition, the signal-to-noise and contrast-to-noise ratios of five major organs were determined. RESULTS: Both imaging techniques were able to reach submillimeter voxel size. The highest resolution of micro-CT was 22 µm (isotropic), while the highest resolution of HF-MRI was 137 µm (isotropic). The qualitative image assessment form was sent to 45 fetal anatomy experts, of whom 36 (80%) responded. It was observed that micro-CT scored higher on all components of the qualitative assessment compared with HF-MRI. In addition, the quantitative assessment showed that micro-CT had lower interobserver variability and higher signal-to-noise and contrast-to-noise ratios. CONCLUSIONS: Our findings show that micro-CT outperforms HF-MRI in postmortem whole-body fetal imaging in terms of both quantitative and qualitative outcomes. Combined, these findings suggest that the ability to extract diagnostic information is greater when assessing micro-CT compared with HF-MRI images. We, therefore, believe that micro-CT is the preferred imaging modality as an alternative to conventional fetal autopsy for early gestation and is an indispensable tool in postmortem imaging services. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Chromogenic media for the detection of Salmonella enterica serovar Paratyphi A in human stool samples: evaluation in a reference setting.

Detection of Salmonella Paratyphi A stool carriers by conventional stool culture media is hindered by the absence of hydrogen sulphide production compared to most other Salmonella serovars. This study evaluated the detection of Salmonella Paratyphi A in stool samples using Salmonella chromogenic media compared to a conventional medium. Four chromogenic media, COMPASS Salmonella agar (Biokar Diagnostics, Beauvais, France), BBL™ CHROMagar™ Salmonella (BD Diagnostics, Erembodegem-Aalst, Belgium), Brilliance™ Salmonella agar (Oxoid Ltd., Basingstoke, UK) and Salmonella PLUS CHROMagar™ (CHROMagar, Paris, France), were compared to conventional Salmonella-Shigella agar (Oxoid Ltd.). The colony morphology of 29 freshly grown stock isolates (Salmonella and competing organisms) was assessed. The limit of detection (LOD) was also determined using saline and stool suspensions. Finally, recognizability of Salmonella Paratyphi A isolates was assessed using 20 human stool samples spiked with different concentrations of Salmonella Paratyphi A. All Salmonella Paratyphi A isolates demonstrated detectable growth with typical purple-coloured colonies that could be clearly differentiated from competing organisms on all four chromogenic media. The LOD for Salmonella Paratyphi A was 103 colony-forming units (CFU)/ml for all media, except for Brilliance agar (105 CFU/ml of stool). Salmonella Paratyphi A was easy to differentiate from competing organisms in the spiked stool samples. Colony yields improved when an enrichment step (Selenite-F broth (BD Diagnostics, Erembodegem-Aalst, Belgium)) and prolonged incubation for 48 h were performed. Chromogenic media demonstrated good specificity and a low LOD for the detection of Salmonella Paratyphi A in stool samples.