Biomedical subjects

G M Treece

Publications and source records attributed to G M Treece.

6 recordsLinked to original sources

PubMed2005

3D reconstruction of the skeletal anatomy of the normal neonatal foot using 3D ultrasound.

Currently imaging plays a limited role in the assessment of the neonate with a foot deformity. The aim of this study was to establish a technique for examining the neonatal foot with three-dimensional ultrasound (3D US). 3D US was attempted on the normal feet of 20 infants (9 male, 11 female) under 6 weeks old (range 35-41 days). The data sets were obtained whilst the infants were feeding or asleep to minimize movement artefact. A high-resolution optically tracked freehand 3D US system (Diasus, 16 MHz transducer) was used with Stradx software to acquire and analyse the data sets. Manual segmentation of the non-ossified tarsi from the data sets was performed. Five infants were too restless to be examined. 107 data sets were recorded from 22 feet of the remaining 15 infants. 21 of the data sets were discarded due to movement artefact. 86 were suitable for manual segmentation. Surface interpolation of the segmented data sets produced surface rendered reconstructions illustrating the complex 3D anatomy of the foot. This new technique may offer a method of examining the deformed foot, e.g. congenital talipes equinovarus.

Female↗

PubMed2005

Spatial mapping of the brachial plexus using three-dimensional ultrasound.

Imaging of the brachial plexus with MRI and standard two-dimensional (2D) ultrasound has been reported, and 2D ultrasound-guided regional anaesthetic block is an established technique. The aim of this study was to map the orientation of the brachial plexus in relation to the first rib, carotid and subclavian arteries, using three-dimensional (3D) ultrasound. A free-hand optically tracked 3D ultrasound system was used with a 12 MHz transducer. 10 healthy volunteers underwent 3D ultrasound of the neck. From the 3D ultrasound data sets, the outlines of the brachial plexus, subclavian artery and first rib were manually segmented. A surface was interpolated from the series of outlines to produce a spatially orientated 3D reconstruction of the brachial plexus. The brachial plexus could be mapped in all volunteers, although a variation in image resolution between individuals existed. Anatomical variations were demonstrated between the 10 volunteers; the most notable and clinically relevant was the alignment of the plexus divisions. 3D reconstructions illustrated the plexus, changing its orientation from a vertical alignment in the interscalene region to a more horizontal alignment in the supraclavicular fossa. Spatial mapping of the brachial plexus is possible with 3D ultrasound using the subclavian artery and first rib as landmarks. There is a deviation from the conventionally described anatomy and this may have implications for the administration of regional anaesthesia.

Adult↗

PubMed2004

Two- and three-dimensional ultrasound in the development of a needle-free injection system.

Ultrasound was used to assess a needle-free injection device for both intradermal and subcutaneous injections. The aim of this study was, first, to differentiate intradermal from subcutaneous injections, both in vivo and in vitro using 2D ultrasound, and second, to quantify the amount of injectate that actually arrives within the dermis or subcutaneous tissues using volume measurements derived from high-resolution 3D ultrasound data sets, using a freehand system (Stradx), developed by the Cambridge University Departments of Engineering and Radiology. For the in vitro study the devices were filled with dye and injected into a pig preparation. The injection site was examined with high-resolution ultrasound and subsequently dissected to locate the injected dye with respect to the dermis. For the in vivo study, 8 volunteers received needle-free injections of normal saline. High-resolution 2D images and 3D data sets were obtained of the injected sites. Proprioceptive information for the 3D data sets was produced using an optically tracked freehand system. Segmentation of the 3D data sets gave an estimation of the volume of injected material (injectate) within the dermis. The results demonstrated that 2D ultrasound could identify the location of the injectate in the in vitro experiments and successfully distinguished an intradermal from a subcutaneous injection. In the in vivo study, 2D ultrasound clearly demonstrated the injectate location within the volunteers' dermis but was less able to demonstrate the dispersion of injectate within the subcutaneous tissues.

Animals↗

PubMed2002

Correction of probe pressure artifacts in freehand 3D ultrasound.

We present an algorithm which combines non-rigid image-based registration and conventional position sensing to correct probe-pressure-induced registration errors in freehand three-dimensional (3D) ultrasound volumes. The local accuracy of image-based registration enables the accurate freehand acquisition of high resolution (>15 MHz) 3D ultrasound data, opening the way for 3D musculoskeletal examinations. External position sensor readings guarantee the large-scale positional accuracy of the data. Pressure correction is shown to dramatically increase the perceived quality of extended-field-of-view data sets and reslices through volumetric data sets, while quantitative comparisons of multiple in vivo volumes demonstrate the superior precision of the corrected data.

Algorithms↗

PubMed2000

Surface interpolation from sparse cross sections using region correspondence.

The ability to estimate a surface from a set of cross sections allows calculation of the enclosed volume and the display of the surface in three-dimensions. This process has increasingly been used to derive useful information from medical data. However, extracting the cross sections (segmenting) can be very difficult, and automatic segmentation methods are not sufficiently robust to handle all situations. Hence, it is an advantage if the surface reconstruction algorithm can work effectively on a small number of cross sections. In addition, cross sections of medical data are often quite complex. Shape-based interpolation is a simple and elegant solution to this problem, although it has known limitations when handling complex shapes. In this paper, the shape-based interpolation paradigm is extended to interpolate a surface through sparse, complex cross sections, providing a significant improvement over our previously published maximal disc-guided interpolation. The performance of this algorithm is demonstrated on various types of medical data (X-ray computed tomography, magnetic resonance imaging and three-dimensional ultrasound). Although the correspondence problem in general remains unsolved, it is demonstrated that correct surfaces can be estimated from a limited amount of real data, through the use of region rather than object correspondence.

Computer Simulation↗

PubMed1999

Fast surface and volume estimation from non-parallel cross-sections, for freehand three-dimensional ultrasound.

Volume measurements from ultrasound B-scans are useful in many clinical areas. It has been demonstrated previously that using three-dimensional (3-D) ultrasound can greatly increase the accuracy of these measurements. Freehand 3-D ultrasound allows freedom of movement in scanning, but the processing is complicated by having non-parallel scan planes. Two techniques are proposed for volume measurement from such data, which also improve surface and volume estimation from data acquired on parallel planes. Cubic planimetry is a more accurate extension of a volume measurement technique involving vector areas and centroids of cross-sections. Maximal-disc shape-based interpolation is an extension of shape-based interpolation which uses maximal disc representations to adjust the interpolation direction locally and hence improve the quality of the surface generated. Both methods are tested in simulation and in vivo. Volumes estimated using cubic planimetry are more accurate than step-section planimetry, and require fewer cross-sections, even for complex objects. Maximal-disc shape-based interpolation provides a reliable means of reconstructing surfaces from a handful of cross-sections, and can therefore be used to give confidence in the segmentation and hence also the cubic planimetry volume.

Anatomy, Cross-Sectional↗