Cranial scintigraphy: value of adding emission computed tomographic sections to conventional pertechnetate images (512 cases).

A prospective trial was carried out to assess the contribution made by a radionuclide transverse-section view to conventional radionuclide scans of the brain. Each set of scans was reported by two independent teams of observers, but only one team viewed the tomography section. An abnormality rating was used to decide whether a set of scans was positive or normal. The reports for 512 patients were analyzed and compared with the final independent diagnosis. Greater accuracy of diagnosis with the section view was significant at the 0.1% level; the results showed that failure to detect tumors was almost halved while there was a 16% improvement for the detection of infarcts. Abnormality ratings were also used to plot ROC curves and rating curves; these showed that the addition of the tomographic view increased markedly the proportion of true positives without any increase in the proportion of false-positive reports.

Theoretical considerations in relation to the treatment of brain tumours by means of local hyperthermia generated by ultrasound fields.

Brain tumours comprise a significant fraction of all tumours in the human body. Despite the development of technology in clinical oncology, these tumours still present a difficult challenge. The margin between destruction of tumour and damage to normal tissue is narrow in the brain. The price paid for producing tissue damage outside the tumour is high in terms of quality of survival. Results of many experiments with ultrasound hyperthermia show that this new technique is successful for treating certain types of malignant tumours. In the case of brain tumours, applying focused fields should have the advantage of selectively destroying the tumour and leaving surrounding tissues intact. Previous attempts at applying ultrasound to the field of neurosurgery are reviewed. Those factors which have effects on the generation of thermal fields in brain tissues are considered in relation to the possible treatment of human brain tumours. Calculated thermal fields in a 2-D brain model generated by an applicator built in our laboratory are also presented.

Study of tissue compression in breast phantoms: possible implications for the use of X-ray mammography as a method of imaging breast carcinoma.

A method is described of constructing a simple phantom breast containing an idealised tumour with elastic properties. The transparent tissues are compressed and evidence is adduced to show that with tissue compression the tumour boundary is subjected to a degree of strain the magnitude of which is dependent on the degree of deformation. Excessive compression can lead to fracture of the tumour. A literature survey reveals that malignant tissues are more delicate than normal tissues. The study underlines the need for care when using X-ray mammography with compression to image a cancer bearing breast, in order to avoid disseminating cancer cells via the circulation.

Lyoluminescence dosimetry with some saccharides.

Lyoluminescent properties of mannose, glucose monohydrate, sucrose and trehalose dihydrate were investigated from the point of view of suitability as dosimetric materials in a new system of solid state dosimetry. Distilled water was used as a solvent. With a reader equipped with an uncooled PM tube it was possible to measure doses of X- and gamma-rays in the range from a few rad to about 100 krad. Various experimental factors which could affect the dose measurements using lyoluminescence are discussed, including the energy response for X-rays. Some preliminary information on the response of saccharides to fast neutrons is also included.

The influence of picture element size on the quality of clinical radionuclide images.

The effect of picture element (pixel) size on image quality is investigated. Asked simply to state their preference for clinical images displayed with different pixel sizes, observers preferred those with the smallest pixel. Specific perceptual tasks, however, such as abnormality detection, are found to be insensitive to changes in pixel size up to a limit. Interpolation is found to have no effect on perceptual tasks, but 'random interpolation' produced a more pleasing image than simple linear interpolation.

Nuclear magnetic resonance pulse sequence and discrimination of high- and low-fat tissues.

Signal size compared to independently measured T1 is described for various pulse sequences on the Aberdeen Mk II nuclear magnetic resonance imager. The ability of these sequences to discriminate between certain tissue types, and in particular between adipose tissue and muscle, is discussed. Inversion recovery, with a t interval of 200 ms, gives the best discrimination for this purpose, with a contrast ratio of 6 between fat and muscle. Other image types, and especially T1, give better contrast for low-lipid soft tissue such as liver and spleen.

The construction and assessment of lenses for local treatment of malignant tumours by ultrasound.

A simple method to build ultrasound lenses from araldite has been developed. The focussing properties of these lenses as a function of sonic frequency and lens diameter were studied using a computer model. The optimum frequency and diameter of these lens were found to be around 1 MHz and between 40 and 60 mm respectively, for deep tissue heating. The stability of the power output as well as the temperature distributions produced in vitro and in vivo have also been studied. It appears to be possible to produce larger temperature elevations near the acoustical focus than near the skin surface in vivo. Therefore the lenses seem to be suitable for local cancer treatment.

Local hyperthermia induced by focussed and overlapping ultrasonic fields--an in vivo demonstration.

Axial temperature distributions were measured in living and post mortem porcine tissues during sonication with plane, focussed and overlapping ultrasonic fields. With the focussed field it was always possible to induce the temperature maxima at depths up to 50 mm, although the actual temperatures achieved varied from animal to animal. The plane 0.75 MHz transducer produced a maximum temperature close to the skin surface. With 7 overlapping plane fields a relatively uniform temperature distribution was produced in a large tissue volume. The blood perfusion in tissue has a significant effect not only on the magnitude of the temperature increase, but also on the temperature distribution.

The measurement of the performance of the display system of radioisotope imaging device: the multi-element band display.

An assessment has been made of the performance of the type of display system in which each display signal intensity, i.e. grey shade or colour, represents a range of count densities or counting rates. In the particular commercially available system used in this investigation eight different grey shades are used to display the image, a range of count densities beingallocated to each grey shade. It is shown experimentally that changes in the distribution of radioisotope can fail to be detected solely due to the manner in which the display is used, viz. The way in which the count density is allocated to the available grey shades. Also, it is shown experimentally that the best display performance can be achieved by using one in which the range of count densities represented by each grey shade is less than three standard deviations of the mean background [corrected] count density.

The influence of size and radiopharmaceutical concentration ratio on the detection of abnormalities in clinical radionuclide imaging.

The effect of the size of an abnormality on its detectability was measured. The cylindrical abnormalities studied, with diameters ranging from 3 mm to 4 cm, were superimposed on a uniform background. To avoid artefacts produced by the imaging devices, the images were simulated by computer. The method of constant stimulus was used to determine the detectability of the abnormalities. By using a Perspex phantom filled with 99Tcm, measurements were made of the concentration ratio between abnormality and background which permitted detection of the abnormality. This allowed evaluation of the effectiveness of 99Tcm pertechnetate in the detection of small abnormalities. Assuming a concentration ratio between abnormal and normal tissue of 22.5:1, then at a depth of 50 mm in the brain a cylindrical abnormality of about 8 mm diameter was the smallest detectable under the chosen scanning conditions.

Comparison of different electrophoretic separations of hen egg white proteins.

The hen egg white protein composition has not yet been fully defined. To improve the knowledge of this biological fluid, the most usual and recently developed electrophoretic methods have been used: SDS-PAGE, native-PAGE, isoelectric focusing (IEF), and 2-dimensional electrophoresis (2DE). Seven of the major known proteins were thus identified in at least one electrophoretic system. Isoforms of ovotransferrin, ovalbumin, and ovomucoid were visualized when pI was used for the separation. Two-dimensional electrophoresis allowed separation of a very large number of spots. In each of the four systems, some components were revealed but not identified, and unknown spots were particularly numerous with 2DE. With this technique, many spots corresponding to small acidic proteins were highlighted, among which was the Ch21 protein, whose presence in hen egg white was thus confirmed. This study thus constitutes, to our knowledge, the first proteomic investigation of hen egg white.

Measurement of blood flow in tibial fracture patients using positron emission tomography.

The quantification of local bone blood flow in man has not previously been possible, despite its importance in the study of normal and pathological bone. We report the use of positron emission tomography, using 15O-labelled water, to measure bone blood flow in patients with closed unilateral fractures of the tibia. We compared fractured and unfractured limbs; alterations in blood flow paralleled those found in animal models. There was increased tibial blood flow at the fracture site as early as 24 hours after fracture, reaching up to 14 times that in the normal limb at two weeks. Blood flow increase was less in displaced than in undisplaced fractures. The muscle to bone ratios of blood flow were similar to those in previous animal work using other techniques. Positron emission tomography will allow study of human bone blood flow in vivo in a wide variety of pathological conditions.

Pattern of 2-deoxy-2-[18F]-fluro-D-glucose accumulation in liver tumours: primary, metastatic and after chemotherapy.

Eight patients with liver metastases from adenocarcinoma of the colon or rectum, two with suspected hepatic metastases and one with primary hepatoma were studied with 2-deoxy-2-[18F]-fluro-D-glucose (18F-FDG) using positron emission tomography (PET). In five of the patients with metastatic tumour a second examination was performed four weeks after treatment with recombinant interleukin-2 (rIL2) and fluorouracil (5FU). In all tumours (one primary and eight metastatic) the radioactivity was seen to accumulate in a rim around each tumour with a large central area showing no uptake. In the five cases imaged after treatment with rIL2, the appearance of the tumour uptake was the same as before treatment. In the two cases of suspected but not proven metastases, no abnormal accumulation of 18F-FDG was seen.

Identifying genes involved in the variability of genetic fatness in the growing chicken.

A precise knowledge of the genome involved in the expression of a quantitative trait could provide a useful tool in breeding programs; molecular genetic methods are capable of yielding this kind of information. An experimental procedure is presented here for identifying genes whose expression is related to weight variability of abdominal adipose tissue in the growing chicken. Quantitative traits are the result of metabolic pathways exhibiting some major regulation stages that are controlled genetically. These steps involve genes that may act as "major genes". With regard to chicken fat metabolism, most fatty acids are synthesized in the liver and incorporated into very low density lipoprotein (VLDL) particles before their secretion into the plasma. Accordingly, the present study focused on the expression of liver genes. The mRNA of lipogenic enzymes (acetyl-coenzyme-A carboxylase, fatty acid synthase, malic enzyme, and delta 9-desaturase) were analyzed. Also studied were apoprotein (apo)A1, apoVLDL-II, and apoB mRNA from 9-wk-old male chickens from two lines selected for high and low abdominal fat pads. Significant differences for apoA1 mRNA levels occurred between fat and lean birds. Moreover, the total quantity of mRNA provided an accurate estimation of the abdominal fat pad (r = .74 with P < .05).

Some of the factors involved in the Sarvazyan method for recording ultrasound field distributions with special reference to the application of ultrasound in physiotherapy.

The mapping of ultrasound fields using the dye paper method is described. The mode of action by which the dye concentration is increased has been investigated. Microbubbles on the paper surface and microstreaming of dye solution seem to be essential features of the mapping method. The streaming is thought to inhibit the formation of a dye depletion layer near the paper to an extent dependent on local sound intensity A linear relation between streaming velocity and intensity is derived.