Combined prenatal US and post-mortem fetal MRI: can they replace conventional autopsy for fetal body abnormalities?

OBJECTIVES: The acceptance of conventional autopsy (CA), the gold standard method for investigating fetal death, often remains problematic. Post-mortem magnetic resonance imaging (PMMRI) is increasingly advocated, particularly for neurologic malformations. However, PMMRI performances to diagnose non-neurologic malformations remain unclear. We aim to clarify whether a full body CA remains needed after prenatal ultrasound (US) and PMMRI in assessing non-neurologic fetal malformations. METHODS: In this retrospective IRB-approved study, during a 6-year period, all fetuses who underwent PMMRI, prenatal US, and full body CA were included. Body abnormalities were identified in US, PMMRI, and CA reports. US and PMMRI images were all reviewed. All abnormalities were graded as major (2 points) or minor (1 point). Each technique (US, PMMRI, CA) was given a score by adding all grading points. In each fetus, results were compared for both separate and combined US and PMMRI to CA. Sensitivity and specificity were calculated for detecting major abnormalities. RESULTS: Fifty fetuses were included. The score of CA, US, and PMMRI was respectively 53, 37, and 46. Compared with US-PMMRI, CA added information in 2 cases (4%) with major abnormalities and 7 cases (14%) with minor abnormalities. PMMRI and US were concordant in 36/50 (72%) fetuses. Separate US/PMMRI sensitivities and specificities for detecting major body malformations respectively were 80%/80% and 100%/94%. Combined US-PMMRI had a sensitivity of 90% and a specificity of 94%. Two cardiac malformations (2/6) were only described by CA. CONCLUSIONS: After prenatal US and PMMRI, few additional fetal body malformations are discovered with CA. Nevertheless, fetal heart autopsy remains mandatory. CLINICAL RELEVANCE STATEMENT: A cardiac conventional autopsy complemented by prenatal ultrasound and post-mortem MRI allows to detect all major fetal body abnormalities. With this efficient and much less invasive approach, a higher acceptance rate of fetal autopsy can be expected. KEY POINTS: • Excepting cardiac malformations, most major fetal body malformations can reliably be identified by prenatal US combined with post-mortem MRI. • In the post-mortem diagnosis of fetal body malformations, a conventional autopsy limited to the fetal heart might replace a full body autopsy after a well-conducted prenatal US and post-mortem MRI.

Real-Time In Vivo Imaging of Human Liver Vasculature Using Coherent Flow Power Doppler: A Pilot Clinical Study.

Power Doppler (PD) is a commonly used technique for flow detection and vessel visualization in radiology clinics. Despite its broad set of applications, PD suffers from multiple noise sources and artifacts, such as thermal noise, clutter, and flash artifacts. In addition, a tradeoff exists between acquisition time and Doppler image quality. These limit the ability of clinical PD imaging in deep-lying and small-vessel detection and visualization, particularly among patients with high body mass indices (BMIs). To improve the Doppler vessel detection, we have previously proposed coherent flow PD (CFPD) imaging and demonstrated its performance on porcine vasculature. In this article, we report on a pilot clinical study of CFPD imaging on healthy human volunteers and patients with high BMI to assess the clinical feasibility of the technique in liver imaging. In this study, we built a real-time CFPD imaging system using a graphical processing unit (GPU)-based software beamformer and a CFPD processing module. Using the real-time CFPD imaging system, the liver vasculature of 15 healthy volunteers with normal BMI below 25 and 15 patients with BMI greater than 25 was imaged. Both PD and CFPD image streams were produced simultaneously. The generalized contrast-to-noise ratio (gCNR) of the PD and CFPD images was measured to provide the quantitative evaluation of image quality and vessel detectability. Comparison of PD and CFPD image shows that gCNR is improved by 35% in healthy volunteers and 28% in high BMI patients with CFPD compared to PD. Example images are provided to show that the improvement in the Doppler image gCNR leads to greater detection of small vessels in the liver. In addition, we show that CFPD can suppress in vivo reverberation clutter in clinical imaging.

Liver Fat Quantification by Ultrasound in Children: A Prospective Study.

BACKGROUND. Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children in certain regions and is rising in prevalence with increasing obesity. Accurate noninvasive imaging methods for diagnosing and quantifying liver fat are needed to guide NAFLD management. OBJECTIVE. The purpose of this article is to evaluate four ultrasound technologies for quantitative assessment of liver fat content in children using MRI proton density fat fraction (PDFF) as a reference standard. METHODS. This prospective study enrolled children who underwent clinical abdominal MRI without general anesthesia between November 2018 and July 2019. Patients underwent investigational liver ultrasound within a day of 1.5-T or 3-T MRI. Acquired ultrasound radiofrequency data were processed offline to compute the acoustic attenuation coefficient, hepatorenal index (HRI), Nakagami parameter, and shear-wave elastography (SWE) parameters (elasticity, viscosity, and dispersion). Ultrasound parameters were compared with MRI PDFF obtained using a multiecho sequence. A second observer independently performed offline attenuation coefficient and HRI measurements in all patients. RESULTS. A total of 48 patients were enrolled: 22 girls, 26 boys; mean age of 13 years (range, 7-17 years); mean body mass index (weight in kilograms divided by the square of height in meters) of 22.25 (range, 14.5-48.1). A total of 21% (10/48) had steatosis (PDFF ≥ 5%). PDFF was correlated with attenuation coefficient (r = 0.76; 95% CI, 0.60-0.86; p < .001), HRI (r = 0.84; 95% CI, 0.74-0.91; p < .001), and Nakagami parameter (r = 0.55, 95% CI, 0.32-0.72, p < .001), but not SWE parameters (r = 0.05-0.25; p > .05). In patients with no, mild, moderate, and severe steatosis according to PDFF, the mean (± SD) attenuation coefficient was 0.48 ± 0.08, 0.54 ± 0.03, 0.57 ± 0.04, and 0.86 ± 0.07 dB/cm/MHz, respectively, and the mean HRI was 1.28 ± 0.30, 1.59 ± 0.23, 2.25 ± 0.04, and 3.06 ± 0.49, respectively. For the attenuation coefficient, the threshold of 0.54 dB/cm/MHz achieved a sensitivity of 80% and a specificity of 82% for steatosis, and 0.60 dB/cm/MHz achieved a sensitivity of 80% and a specificity of 98% for moderate steatosis. For HRI, the threshold of 1.48 achieved sensitivity of 90% and specificity of 76% for steatosis, and 2.11 achieved sensitivity of 100% and specificity of 100% for moderate steatosis. The interobserver concordance coefficient was 0.92 for attenuation coefficient and 0.91 for HRI. CONCLUSION. Attenuation coefficient and HRI accurately detected and quantified liver fat in this small sample of children. CLINICAL IMPACT. Quantitative ultrasound parameters may guide NAFLD diagnosis and management in children.

Postmortem fetal magnetic resonance imaging: where do we stand?

Postmortem fetal magnetic resonance imaging (PMFMRI) is increasingly used thanks to its good overall concordance with histology paralleling the rising incidence of parental refusal of autopsy. The technique could become a routine clinical examination but it needs to be standardized and conducted by trained radiologists. Such radiologists should be aware of not only the (congenital and acquired) anomalies that can involve the fetus, but also of the "physiological" postmortem changes. In this article, we intend to focus on the contribution of PMFMRI based on the existing literature and on our own experience, as we presently perform the technique routinely in our clinical practice. KEY POINTS: • Concordance rates between PMFMRI and autopsy are high for detecting fetal pathologies. • PMFMRI is more acceptable for parents than traditional autopsy. • PMFMRI is becoming widely used as a part of the postmortem investigations. • A dedicated radiologist needs to learn to interpret correctly a PMFMRI. • PMFMRI can be easily realized in daily clinical practice.

Tuning of automatic exposure control strength in lumbar spine CT.

OBJECTIVE: To investigate the impact of tuning the automatic exposure control (AEC) strength curve (specific to Care Dose 4D®; Siemens Healthcare, Forchheim, Germany) from "average" to "strong" on image quality, radiation dose and operator dependency during lumbar spine CT examinations. METHODS: Two hospitals (H1, H2), both using the same scanners, were considered for two time periods (P1 and P2). During P1, the AEC curve was "average" and radiographers had to select one of two protocols according to the body mass index (BMI): "standard" if BMI <30.0 kg m(-2) (120 kV-330 mAs) or "large" if BMI >30.0 kg m(-2) (140 kV-280 mAs). During P2, the AEC curve was changed to "strong", and all acquisitions were obtained with one protocol (120 kV and 270 mAs). Image quality was scored and patients' diameters calculated for both periods. RESULTS: 497 examinations were analysed. There was no significant difference in mean diameters according to hospitals and periods (p > 0.801) and in quality scores between periods (p > 0.172). There was a significant difference between hospitals regarding how often the "large" protocol was assigned [13 (10%)/132 patients in H1 vs 37 (28%)/133 in H2] (p < 0.001). During P1, volume CT dose index (CTDIvol) was higher in H2 (+13%; p = 0.050). In both hospitals, CTDIvol was reduced between periods (-19.2% in H1 and -29.4% in H2; p < 0.001). CONCLUSION: An operator dependency in protocol selection, unexplained by patient diameters or highlighted by image quality scores, has been observed. Tuning the AEC curve from average to strong enables suppression of the operator dependency in protocol selection and related dose increase, while preserving image quality. ADVANCES IN KNOWLEDGE: CT acquisition protocols based on weight are responsible for biases in protocol selection. Using an appropriate AEC strength curve reduces the number of protocols to one. Operator dependency of protocol selection is thereby eliminated.