Ad Linney

Three dimensionaldigitization of the face and skull

The possibility of using computer-aided design as a tool for the planning and simulation of facial reconstruction surgery is discussed and has been shown to be feasible. Methods of acquiring the essential measurements on the facial surface and the underlying bone structure in a computer-compatible form are described, including a new approach which has been implemented using a system of fanned laser beams and a television camera for data acquisition. A mathematical analysis of the properties of this kind of imaging system is given. Finally the requirements of a complete aid to surgery system based on this approach are outlined and plans for the implementation of such a system are described.

A laser scanning system for the measurement of facial surface morphology

Abstract A no contact system based on laser scanning, which records 20 000 facial surface coordinates with a dynamic resolution of approximately 0·9mm in 30s, has been developed for the study of facial changes following facial reconstructive surgery. Individual profiles are recorded with a resolution better than 0·5mm. The system is based on the analysis of the output from a video camera which obliquely views a laser line projected vertically onto the face. In order to sample the whole face, the subject sits on a chair which rotates at six degrees per second under computer control. Examples of applications of the system are given.

Real-time three-dimensional fetal echocardiography - Optimal imaging windows

A total of 15 fetuses were scanned using 2-D array volumetric ultrasound (US). Acquired cardiac data were converted for rendering dynamic 3-D surface views and reformatting cross-sectional views. The image usefulness was compared between the data obtained from subcostal/subxiphoid and other imaging windows; the former are usually free of acoustic shadowing. Of 60 data sets recorded, 12 (20%) were acquired through subcostal windows in 6 (40%) patients. Subcostal windows were unavailable from the remaining patients due to unfavourable fetal positions. Of the 12 sets, 6 (50%) provided the dynamic 3-D and/or cross-sectional views of either the entire fetal heart or a great portion of it for sufficient assessments of its major structures and their spatial relationships. Of 48 data sets from other windows, only 9 (19%) provided such 3-D and/or cross-sectional views; the lower rate being due to acoustic shadowing. Real-time 3-D US is a convenient method for volumetric data acquisition. Through subcostal windows, useful information about the spatial relationships between major cardiac structures can be acquired. However, to offer detailed information, considerable improvement in imaging quality is needed.

Online motion-gated dynamic three-dimensional echocardiography in the fetus—preliminary results

The aim of this study was to visualise the fetal heart in dynamic three dimensions (4-D) during an ultrasound (US) scan (online), rather than after (offline). With special pairing and sequential setting to minimise interference between two scanners, umbilical arterial Doppler waveforms (UADWs) from one scanner were used as an online motion gating source to trigger simultaneous 3-D cardiac structural data acquisition by another. Of 25 data sets from 10 fetuses, 18 were acquired in 15 to 30 s per set with > or = 50% Doppler waveforms efficiently converted to triggering signals. Of 15 valid 4-D data sets, 10 were reconstructed in 2 to 20 min, compared to over 2 h previously reported (mainly for offline gating). Fine structures (including chordae tendinae and trabecular muscles) were depicted in six sets. The main problems in degrading 4-D images were extensive shadowing (6) from bony structures during rigid mechanical scanning, and random motion artefacts (6) from prolonged setting-up time with a complex combination of several systems. Integration of these systems is, therefore, recommended.

The Relationship and Reproducibility of Angle ANB and the Wits Appraisal

An analysis is presented of the errors and variations in the Wits analysis and the angle ANB, using computer simulation. The method is applicable to any index where the identification errors have been established for the points and planes used in its derivation. A standard deviation may be determined for the index produced and the statistical distribution of values for any number of observations.

Simultaneous use of two ultrasound scanners for motion-gated three-dimensional fetal echocardiography.

The aim of this study was to determine whether or not simultaneous use of an additional Doppler transducer could provide sufficient cardiovascular motion information without significantly interfering with three-dimensional (3-D) cardiac structural data acquisition by a primary two-dimensional (2-D) transducer. To determine sources of interference, paired transducers were activated alternatively and simultaneously in and out of a water bath, with and without electrical insulating and electromagnetic shielding. To determine factors affecting interference, pairs were tested on a phantom with different separating distances and angles between paired ultrasound (US) beams and under different 2-D depths and Doppler scales. Results show that the dominant source of interference is acoustic cross talk. The severity was mainly affected by transducer pairing and by separating distances and angles, and the pattern by display settings. With optimised settings, sufficient structural and motion data were obtained simultaneously in 9 of 12 fetal hearts, and detailed 3-D views could be reconstructed free of motion artefacts, confirming the feasibility of using the method for motion-gated 3-D fetal cardiac imaging. New scanner design strategy was then proposed.

A preliminary study of computer recognition and identification of skeletal landmarks as a new method of cephalometric analysis.

The usefulness of results obtained with cephalometrics is limited by measurement error. Much of this is due to the subjective nature of landmark identification on X-rays. Such subjectivity is not eliminated by electronic plotting equipment—despite its high resolution. Automatic (non-subjective) landmark identification of sella and menton was carried out in this study using the CLIP4 image processing system. The results obtained on 23 radiographs were compared with those of conventional techniques.

Novel technique for three-dimensional visualisation and quantification of deformable, moving soft-tissue body parts

BACKGROUND Three-dimensional (3D) imaging of delicate, moving soft-tissue body parts is very difficult. Our understanding of the muscles that control lip movements is based largely on histological and cadaveric studies, which provide scant information about dynamic morphology. Our aim was to develop an innovative scanning technique for the imaging and reconstruction of dynamic orofacial morphology by use of 3D and four-dimensional (4D, ie, 3D plus time) ultrasonography. METHODS Four volunteers (including one patient) underwent ultrasonography with 3D/4D imaging systems. To avoid deformation of the delicate orofacial structures, a water bath with an acoustic window was devised. The orofacial part was immersed in the bath throughout scanning, and a timer was used to synchronize lip movements with the 4D scan. FINDINGS 4D views showed the functional differences in superficial and deep muscle groups of the lips, and clearly showed the changes occurring with movement of the lips and mouth. In the patient, a pathological layer and its extension corresponding to surface malformation were clearly identified. INTERPRETATION We have developed a prototype device that has made possible 3D and 4D examination of orofacial anatomy and function. With further refinement of the device and improvement in 4D acquisition timing, this technique may offer a new way of dynamically imaging and quantifying many soft-tissue parts in 3D without deforming structure or disturbing function.

OC183: Clinical application of real‐time three‐dimensional ultrasound to the fetal heart

two procedures at 23 + 5 and 28 weeks with reduction in pressures. Good RV but poor TV growth make a one-and-a-half ventricle repair the most likely outcome. Conclusion: Fetal valvuloplasty is technically feasible and permits survival to term. It may have allowed biventricular repair in cases destined to the univentricular route. Repeated procedures, because of the ongoing disease process, advise interventions should be minimally invasive. All cases required early postnatal procedures.

Method for the analysis of the 3-D shape of the face and changes in the shape brought about by facial surgery

A method based on differential geometry is presented for quantitatively measuring facial (or body) surfaces and the amount of change produced in them by facial surgery. Facial shape is described mathematically in terms of 8 fundamental surface types. Changes produced in the shape of the face are described in terms of changes in these constituent surfaces. The method is illustrated using examples of faces changed by reconstructive surgery and its relationship to clinical observation explained.