Robyn A. Owens

Registration of stereo and temporal images of the retina

The registration of retinal images is required to facilitate the study of the optic nerve head and the retina. The method the authors propose combines the use of mutual information as the similarity measure and simulated annealing as the search technique. It is robust toward large transformations between the images and significant changes in light intensity. By using a pyramid sampling approach combined with simulated reannealing the authors find that registration can be achieved to predetermined precision, subject to choice of interpolation and the constraint of time. The algorithm was tested on 49 pairs of stereo images and 48 pairs of temporal images with success.

Calibrating a Structured Light Stripe System: A Novel Approach

The problem associated with calibrating a structured light stripe system is that known world points on the calibration target do not normally fall onto every light stripe plane illuminated from the projector. We present in this paper a novel calibration method that employs the invariance of the cross ratio to overcome this problem. Using 4 known non-coplanar sets of 3 collinear world points and with no prior knowledge of the perspective projection matrix of the camera, we show that world points lying on each light stripe plane can be computed. Furthermore, by incorporating the homography between the light stripe and image planes, the 4 × 3 image-to-world transformation matrix for each stripe plane can also be recovered. The experiments conducted suggest that this novel calibration method is robust, economical, and is applicable to many dense shape reconstruction tasks.

BREAST VOLUME AND MILK PRODUCTION DURING EXTENDED LACTATION IN WOMEN

Quantitative measurements were made of relative breast volume and milk production from 1 month of lactation until 3 months after weaning, and the storage capacity of the breasts was calculated. The increase in breast tissue volume from before conception until 1 month of lactation was maintained for the first 6 months of lactation (means ±s.e.m.) (190·3 ± 13·1 ml, number of breasts, nb= 46). During this period of exclusive breast‐feeding, 24 h milk production from each breast remained relatively constant (453·6 ± 20·1 g, nb= 48), and storage capacity was 209·9 ± 11·0 ml (nb= 46). After 6 months, breast volume, milk production and storage capacity all decreased. There was a relationship between 24 h milk production and the storage capacity of the breasts, and these both appeared to be responding to infant demand for milk. At 15 months of lactation, the 24 h milk production of each breast was substantial (208·0 ± 56·7 g, nb= 6), even though the breasts had returned to preconception size. This was associated with an apparent increased efficiency of the breast (milk production per unit breast tissue) after 6 months, which may have been due to redistribution of tissues within the breast. The possible causes of the decrease in breast volume are discussed.

Location of the pupil-iris border in slit-lamp images of the cornea

We present results for an active contour that finds the pupil-iris border in slit lamp images of the eye. Preprocessing involves producing a variance image from the original image and then locating the annulus, of a given size, which has the lowest mean variance. The centre of this annulus falls inside the pupil, giving a starting position for a discrete circular active contour (DCAC). The DCAC is moved under the influence of two forces-external and internal. The external force is based on the grey-scales immediately inside and outside of the contour, at each vertex, in both the original and variance images and pushes the vertices inwards. The internal force acts to move the contour towards a perfect polygon, /spl delta/ larger than the current polygon. Repeated trials with decreasing values of /spl delta/ are performed until equilibrium is reached between the two forces and the pupil/iris border has been found.

BREAST GROWTH AND THE URINARY EXCRETION OF LACTOSE DURING HUMAN PREGNANCY AND EARLY LACTATION: ENDOCRINE RELATIONSHIPS

Breast volume and morphology of eight subjects were measured before conception and at intervals throughout pregnancy until 1 month of lactation. Breast volume before conception ranged from 293 to 964 ml. At the end of pregnancy the volume of breast tissue had increased by 145 ± 19 ml (mean ±s.e.m., n= 13 breasts, range 12‐227 ml) with a further increase to 211 ± 16 ml (n= 12 breasts, range 129‐320 ml) by 1 month of lactation. Urinary excretion of lactose increased at 22 weeks of pregnancy, signalling the capacity of the breast to synthesize lactose at this time. During pregnancy, both the change in breast volume and the change in cross‐sectional area of the areola were related to the concentration of human placental lactogen in the plasma. The growth of the nipple and the rate of excretion of lactose were related to the concentration of prolactin in the plasma. During the first 3 days after birth, the rate of excretion of lactose was related to the rate of excretion of progesterone. There was no relationship between the growth of the breast during pregnancy and the amount of milk produced at 1 month of lactation.

Averaging feature maps

Abstract We describe a method for combining several instances of image feature maps to obtain an `average’ feature map. Applications are shown to radar maps of aircraft flight paths, and line sketches of human faces. The technique is an adaptation of the `distance average’ of random sets introduced by Baddeley and Molchanov. It involves computing the distance transform of each input image, calculating the pixelwise mean (or median or trimmed mean) of distance values, and applying a threshold or ridge-tracing operation to obtain a binary image.