Basil Shepstone

Effect of central cholinergic stimulation on regional cerebral blood flow in Alzheimer disease

Patients with Alzheimer disease (AD) had reduced regional cerebral blood flow (rCBF) in the posterior parietotemporal region compared with controls, as determined with technetium-99m hexamethyl propyleneamine oxime and single photon emission tomography. Central cholinergic stimulation with physostigmine produced a focal increase in rCBF in the posterior parietotemporal region in the patients with AD but not in controls.

A representation for mammographic image processing

Abstract Mammographic image analysis is typically performed using standard, general-purpose algorithms. We note the dangers of this approach and show that an alternative physics-model-based approach can be developed to calibrate the mammographic imaging process. This enables us to obtain, at each pixel, a quantitative measure of the breast tissue. The measure we use is h int and this represents the thickness of ‘interesting’ (non-fat) tissue between the pixel and the X-ray source. The thicknesses over the image constitute what we term the h int representation, and it can most usefully be regarded as a surface that conveys information about the anatomy of the breast. The representation allows image enhancement through removing the effects of degrading factors, and also effective image normalization since all changes in the image due to variations in the imaging conditions have been removed. Furthermore, the h int representation gives us a basis upon which to build object models and to reason about breast anatomy. We use this ability to choose features that are robust to breast compression and variations in breast composition. In this paper we describe the h int representation, show how it can be computed, and then illustrate how it can be applied to a variety of mammographic image processing tasks. The breast thickness turns out to be a key parameter in the computation of h int , but it is not normally recorded. We show how the breast thickness can be estimated from an image, and examine the sensitivity of h int to this estimate. We then show how we can simulate any projective X-ray examination and can simulate the appearance of anatomical structures within the breast. We follow this with a comparison between the h int representation and conventional representations with respect to invariance to imaging conditions and the surrounding tissue. Initial results indicate that image analysis is far more robust when specific consideration is taken of the imaging process and the h int representation is used.

DETERMINING CORRESPONDENCE BETWEEN VIEWS

Two-view breast screening using cranio-caudal (CC) and medio-lateral oblique (MLO) mammograms has been shown to detect more cancers and lead to less women being recalled to assessment [11], [12] than one-view screening. However, matching signs between two views of the same breast can be a difficult task due to the changing geometry and, crucially, the effects of breast compression. If it were only the geometry that were changing the matching problem would reduce to being one of wide-angle stereo [1]. In this paper we develop a model-based method for finding a curve in the medio-lateral oblique mammogram which corresponds to the potential positions of a point marked in the cranio-caudal mammogram. A more mathematical version of this paper is in [7]. Related work on this problem [10], [9] does not explicitly consider compression. However, work on analysis of stomach x-rays [6] has shown the possibilities of modelling 3D deformations using a model-based approach.

Immunoscintigraphy of endometriosis

Summary. Twenty‐eight women with suspected endometriosis or infertility, or both, received radiolabelled monoclonal antibody OC‐125 F(ab′)2 fragments before surgery in a study to determine whether foci of pelvic endometriosis could be displayed with immunoscintigraphy. Immunoscintigraphy was positive in 22 women (16 with endometriosis, two with pelvic adhesions, one with pelvic inflammatory disease and one with normal pelvic findings) and negative in five women (two with endometriosis and three with normal pelvic findings). One woman developed a hypersensitivity reaction and, therefore, did not receive the radiolabelled fragments. The method had 89% sensitivity and 33% specificity for the diagnosis of endometriosis; it had 91% sensitivity and 60% specificity for the diagnosis of benign pelvic disease.

Estimating Compressed Breast Thickness

The compressed breast thickness must be known in order to properly calibrate the mammographic imaging process and to estimate radiation dose [5]. Newer mammography machines have thickness indicators but these are currently wanting and other techniques such as using the magnification of lead markers placed on the top compression plate have practical difficulties [1], [6]. Neither technique allows retrospective estimation of thickness. In this paper we present a new method for estimating the thickness using the breast image, calibration data and image processing.

Imaging of pulmonary endometriosis by immunoscintigraphy. Case report.

A 36-year-old woman presented in 1989 with cyclical low abdominal pain and haemoptysis. She was first seen in 1980 with right iliac fossa pain. Minimal pelvic endometriosis was found at laparoscopy and was confirmed histologically; she was treated with danazol. In 1982, a repeat laparoscopy showed minimal scarring from old endometriosis. Her pain persisted despite further treatment with progestogens and a gonadotrophin releasing hormone agonist . Two laparotomies were performed in 1983-84 to divide pelvic adhesions; no further macroscopic evidence of endometriosis was found. She first developed cyclical haemoptysis and left-sided pleuritic pain in 1986. A ventilation perfusion scan and bronchoscopy were normal. Pleuroscopy showed a macroscopically normal left pleural surface but on random biopsy there was microscopic evidence of chronic inflammation; pleurodesis was not performed. A clinical diagnosis of pulmonary endometnosis

Integration of Low-Level Processing to Facilitate Microcalcification Detection

The performance of microcalcification detection algorithms is currently not good enough for them to be used in a clinical setting. Most attempts to improve their performance consist of devising increasingly smarter high-level detection schemes. In contrast, we believe that application of low-level model-based image processing can reduce the number of false positives generated by existing detection algorithms. In this paper, we show how to identify those pixels which tend to be systematically labeled falsely as microcalcifications because of their similarity in radiological appearance to microcalcifications, namely screen-film ‘shot’ noise. In one of the most successful algorithms, Karssemeijer [4] treats such noise at the segmentation step, not in his preprocessing step which aims at making noise spectrally flat by rescaling pixel values, by defining an extra label class in his Markov random field (MRF) model.

Cerebral scintigraphy--the phoenix rises again.

This paper reviews the development of cerebral scintigraphy from its early days of planar imaging with simple technetium-99m labelled compounds to the recent revival of the technique in the form of positron-emission and single-photon emission tomography. A short explanation of instrumentation and radiopharmaceuticals is given as a prelude to a description of both techniques in normal and pathological situations. Particular emphasis is placed on the more readily-available single-photon emission-tomographic techniques using labelled amines in the functional investigation of disorders not readily diagnosed by computed tomography.

Imaging in the dementias

There are over 50 causes of dementia. Some of these may have clear clinical features, but others may be difficult to diagnose. A diagnosis and a prognosis is important to both patients and families so that appropriate care and drug therapies can be employed. Neuroimaging techniques are considered in two categories: structural and functional. The former include computed tomography and magnetic resonance imaging, and the latter singlephoton emission tomography and positron emission tomography. A more recent synthesis of both methods is image registration whereby the functional image is superimposed on the structural one, which can then demonstrate the anatomical region in which the functional defect has occurred.