Free-breathing unsedated MRI in children: Justification and techniques.

One of the more common and important challenges in the imaging of children is minimizing image degradation caused by motion. This is especially important in MRI, which is often preferable in the pediatric population due to better tissue characterization and lack of ionizing radiation. However, due to the length of time needed for most examinations, MRI is among the most sensitive to disruption by patient motion. Traditionally, deep conscious sedation or general anesthesia was the most common method of reducing motion in children who are unable or unwilling to follow direction. As the drawbacks and risks of anesthesia in children become more known and accepted, the development and optimization of means of mitigating motion and anxiety in children without the use of sedation or anesthesia becomes more urgent. In this article we describe the risks of sedation in the pediatric population and explore current methods of reducing both patient anxiety and imaging degradation from motion in the unsedated, free-breathing child. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;50:365-376.

A Simulation Paradigm for Evaluation of Subtle Liver Lesions at Pediatric CT: Performance and Confidence.

Purpose: To create and validate a systematic observer performance platform for evaluation of simulated liver lesions at pediatric CT and to test this paradigm to measure the effect of radiation dose reduction on detection performance and reader confidence. Materials and Methods: Thirty normal pediatric (from patients aged 0-10 years) contrast material-enhanced, de-identified abdominal CT scans obtained from July 1, 2012, through July 1, 2016, were retrospectively collected from the clinical database. The study was exempt from institutional review board approval. Zero to three simulated, low-contrast liver lesions (≤6 mm) were digitally inserted by using software, and noise was added to simulate reductions in volume CT dose index (representing radiation dose estimation) of 25% and 50%. Pediatric, abdominal, and resident radiologists (three of each) reviewed 90 data sets in three sessions using an online interface, marking each lesion location and rating confidence (scale, 0-100). Statistical analysis was performed by using software. Results: Mixed-effects models revealed a significant decrease in detection sensitivity as radiation dose decreased (P < .001). The mean confidence of the full-dose and 25% dose reduction examinations was significantly higher than that of the 50% dose reduction examinations (P = .011 and .012, respectively) but not different from one another (P = .866). Dose was not a significant predictor of time to complete each case, and subspecialty was not a significant predictor of sensitivity or false-positive results. Conclusion: Sensitivity for lesion detection significantly decreased as dose decreased; however, confidence did not change between the full-dose and 25% reduced-dose scans. This suggests that readers are unaware of this decrease in performance, which should be accounted for in clinical dose reduction efforts.Keywords: Abdomen/GI, CT, Liver, Observer Performance, Pediatrics, Perception Image© RSNA, 2019.