OSIRIS-REx Contamination Control Strategy and Implementation

OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and <180 ng/cm² of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.

Advances in ophthalmic ultrasound

New ultrasound technologies, including three-dimensional imaging, tissue characterization, and very high frequency (50 MHz) ultrasound, have become available recently. We demonstrate how these technologies can be used alone and together to improve the use of ultrasound for diagnosis of ocular pathology.

Correlation of high-frequency ultrasound backscatter with tumor microstructure in iris melanoma

OBJECTIVE

This study aimed to correlate histologic characteristics with high-frequency ultrasound backscatter spectra in malignant melanomas of the iris.

DESIGN

The study design was a cohort (case series) study of patients diagnosed with iris melanoma in the authors' clinic.

PARTICIPANTS

Sixteen patients with iris melanoma participated.

INTERVENTION

The patients were scanned with a 50-MHz ultrasound unit equipped for digitization of raw echo data. Spectral parameter images representing the spatial distribution of size and concentration of tissue inhomogeneities were produced.

MAIN OUTCOME MEASURES

The variation of spectral properties within and between tumors was determined. In the two tumors in this series for which histologic material was available, the authors compared scatterer concentration and size with histology and mathematically modeled the effect of melanocyte distribution on spectra.

RESULTS

Ultrasound scattering characteristics differed considerably among tumors. Where histology was available, acoustic parameters correlated with the size and number of melanocytes present.

CONCLUSIONS

Iris melanomas exhibited a wide range in acoustic backscatter properties. Whereas characteristics such as vascularity and necrosis might contribute to this, in the two cases examined here, backscatter characteristics could be largely accounted for by melanocyte distribution. A better understanding of the relationship of histology to noninvasive ultrasound data will enhance the diagnostic utility of this technique.

Three-dimensional ultrasound imaging. Clinical applications

OBJECTIVE

The aim of this report is to describe the technology of three-dimensional (3-D) ultrasonic imaging and its impact on improved diagnosis and monitoring of ocular disease.

DESIGN

The authors reviewed techniques for acquiring and displaying 3-D ultrasound data of the eye.

PARTICIPANTS

The authors applied these techniques to representative individual cases, including a choroidal hemorrhage, a ciliary body melanoma, a ciliary body detachment, a displaced posterior chamber intraocular lens, and topographic analysis of a normal cornea.

INTERVENTION

A computer-controlled motion system was used to perform very high-frequency (VHF) (50-MHz) and conventional (10-MHz) digital 3-D ultrasound data collection. The scanning system allowed digitization of ultrasound data from a series of parallel planes. The 3-D data could be manipulated interactively to obtain two-dimensional images in any plane through the scan volume. The 3-D images were constructed by volume rendering and could be positioned for viewing from a variety of perspectives. The 3-D ultrasound parameter images representing acoustic scatterer properties were generated by spectrum analysis of digitized echo data. Color maps representing the contour and thickness of the epithelium and stroma of the central corneal were generated by digital signal processing of 3-D echo data.

RESULTS

Quantitative volume measurement and biometric techniques enhanced the diagnostic and treatment planning information content in 3-D ultrasound images. The location and extent of hemorrhage and clots within the suprachoroidal space were shown with solid modeling. Volume changes in ciliary body melanoma over time were documented and 3-D ultrasound parameter image changes associated with radiation therapy observed. In ciliary body detachment, the extent of the detachment was shown. Solid modeling of a posterior chamber intraocular lens showed misplacement of the haptic in relation to the lens capsule remnants. Keratopachymetric maps showed the range and variance of thickness and local radius of curvature measurements in the cornea.

CONCLUSIONS

Quantitative volume measurement and biometric tools combined with segmentation of 3-D ultrasound images improve diagnostic and treatment planning informational content of 3-D ultrasound images through improved localization of tissue structures.

Unrecognized aspiration of an oropharyngeal airway

A case of unsuspected aspiration of an oropharyngeal airway causing dysphagia is described. Visualization of this airway on plain film would be facilitated if radio-opaque material were included at manufacture.