Volume segmentation of transverse cine MR images of the hypopharynx aids in quantification of increased airway wall motion in children with OSA. Transverse MR imaging demonstrates both airway distention and collapse in children with OSA.

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ObjectiveThe purpose of this study is to evaluate the airway dynamics of the upper airway as depicted on cine MRI in children with tracheotomy tubes during two states of airflow through the upper airway.Materials and MethodsSagittal fast gradient echo cine MR images of the supra-glottic airway were obtained with a 1.5T MRI scanner on seven children with tracheotomy tubes. Two sets of images were obtained with either the tubes capped or uncapped. The findings of the cine MRI were retrospectively reviewed. Volume segmentation of the cine images to compare the airway volume change over time (mean volume, standard deviation, normalized range, and coefficient of variance) was performed for the capped and uncapped tubes in both the nasopharynx and hypopharynx (Signed Rank Test).ResultsGraphical representation of the airway volume over time demonstrates a qualitative increased fluctuation in patients with the tracheotomy tube capped as compared to uncapped in both the nasopharyngeal and hypopharyngeal regions of interest. In the nasopharynx, the mean airway volume (capped 2.72 mL, uncapped 2.09 mL, p = 0.0313), the airway volume standard deviation (capped 0.42 mL, uncapped 0.20 mL, p = 0.0156), and the airway volume range (capped 2.10 mL, uncapped 1.09 mL, p = 0.0156) were significantly larger in the capped group of patients. In the hypopharynx, the airway volume standard deviation (capped 1.54 mL, uncapped 0.67 mL, p = 0.0156), and the airway volume range (capped 6.44 mL, uncapped 2.93 mL, p = 0.0156) were significantly larger in the capped tubes. The coefficient of variance (capped 0.37, uncapped 0.26, p = 0.0469) and the normalized range (capped 1.52, uncapped 1.09, p = 0.0313) were significantly larger in the capped tubes.ConclusionThere is a statistically significant change in airway dynamics in children with tracheotomy tubes when breathing via the airway as compared to breathing via the tracheotomy tube.

Small-animal imaging systems are often characterized using phantoms, which may not predict performance in clinical applications. An implantable synthetic SPECT lesion would facilitate characterization of lesion detectability in a living animal. Methods: Anion-exchange columns with bed volumes of 100-300 nL were constructed from medical-grade polyvinyl chloride tubing and resin. The columns were tested in an excised mouse femur and implanted in the femur of a living mouse. Imaging was performed using a prototype dual-modality SPECT/CT system. Results: Activity of 7.4-22.2 MBq (0.2-0.6 mCi) localized within the synthetic lesion. The synthetic lesions were reused multiple times. Mice tolerated the implanted columns without complications for up to 8 wk. Conclusion: A reusable, synthetic SPECT lesion was constructed and implanted in the femur of a living mouse. The synthetic lesion is useful for the development of imaging schemes and for more realistically evaluating imagingsystem performance in the context of a living animal. The imaging of small-animal models of disease is an evolving science (1-5). Although dedicated small-animal imaging systems, including SPECT, PET, MRI, and CT, are commercially available, development of new small-animal systems with improved performance continues at a rapid pace. Small-animal imaging systems face additional constraints and limitations in spatial resolution and sensitivity relative to human imaging (6-8). Imaging phantoms are commonly used to assess equipment function and performance.However, phantoms typically do not directly measure imaging-system performance of a clinical or biomedical task. Small-animal imaging systems pose additional technical problems, such as animal immobilization and anesthesia, image coregistration, and validation, which often cannot be adequately addressed with typical phantom studies.An implantable synthetic SPECT lesion would bridge the gap between phantom studies and live small-animal imaging. An ideal synthetic SPECT lesion would have known size and activity ranges, be made of biocompatible materials, and be reusable. Incorporation of a synthetic lesion into a live animal would allow standardized imaging studies in the context of living tissues, with all of the real-life challenges of background activity, anesthesia, physiologic monitoring, and animal positioning. A rechargeable synthetic lesion would minimize the number of animals used during technique development. The known size, location, and activity range of a synthetic SPECT lesion could facilitate development and refinement of quantitative reconstruction algorithms, automated lesion detection, size-estimation tasks, and coregistration algorithms in multimodality imaging schemes. MATERIALS AND METHODS Catheter AssemblyAnion-exchange chromatography beads with quaternary amine groups were selected to provide fixed ionic binding sites for negatively charged ions in solution such as 99m TcO 42 . Two to 6 AG 1-X2, 50-to 100-mesh anion-exchange chromatography beads (Bio-Rad) were placed inside a 5-...