[en] The rapid and accurate quantification of radioactivity in the ground is important in many instances to enable appropriate decisions to be made about limiting its use. In-situ gamma spectrometry has been shown to be a potentially powerful technique for providing this information but its accuracy is dependent on knowledge of the activity variation with depth which is generally unavailable. Methods that allow this distribution to be rapidly determined have previously been published but all rely on a fixed depth-distribution model which is unrealistic. A novel technique using submerged collimated detector measurements termed the Submerged Detector Method (SDM) has been proposed, and theoretically assessed in earlier work and has given promising results. In this work, the SDM is experimentally assessed at 19 sites in Wales, U.K., of variable ¹³⁷Cs activity levels and profile shapes. Practicality and accuracy both in the derived activity per unit area and the profile shapes were assessed against the best of the other methods. The results confirm that the SDM gives more accurate results with the derived activity per unit area on average within ∼40% of the true value and the depth distributions being more accurately determined

[en] A modified form of the back-to-front display algorithm has been implemented on a conventional nuclear medicine computer, enabling real time display of three-dimensional shaded surface images of the heart. A surface model was created from conventional blood pool tomograms, and displayed using depth shading. Mean time required to process 40 tomographic sections was 45 s; subsequently the heart could be inspected from any aspect with a refresh rate of 2-4 Hz, giving the effect of real time rotation. Rapid oscillation between end-diastolic and end-systolic images allowed wall motion to be assessed, and was combined with interactive selection of the viewing direction using a trackerball. For hard copy images, a surface orientation shading algorithm was used. Kinetic information was incorporated by creating composite hidden surface images from end-diastolic and end-systolic objects, using colour to indicate which surface was visible. (author)

[en] Tomographic images of three-dimensional radionuclide distributions are usually presented as a set of parallel planar slices. A technique has been developed to enable the observer to perceive directly the three-dimensional morphology of the activity distribution by displaying iso-count surface. Computer graphics techniques have been used to present shaded surface images using a conventional nuclear medicine computer system. Because of the relatively coarse spatial sampling of radionuclide tomograms, a smooth shading algorithm based on a local polynomial fit procedure was developed. By using a simple solid model approach for data storage the program executes interactively, allowing the observer to view the reconstructed activity distribution from any aspect. The technique has been successfully applied to radionuclide tomograms of several organs, and promises to be particularly useful for the display or cardiac blood pool data. (author)

[en] Shaded surface images have the ability to display three-dimensional information in two-dimensional form. They can therefore be produced on conventional displays, and allow hard copies to be obtained. However, they do not include information about inhomogeneities beneath the displayed surface. A technique has been described for the production of shaded surface images, and simple procedures such as slicing and complementing have been shown to overcome some of the limitations of surface displays. It is suggested that this form of display may be a useful adjunct to conventional displays, especially for complex 3D distributions. The method has been illustrated with reference to radionuclide tomography (ECAT) but could be applied to the data from any tomographic imaging modality. Examples of liver and spleen, lung perfusion, and brain scans are presented. (U.K.)

No abstract available

[en] The measurement of gamma-camera linearity and resolution forms an important part of acceptance testing and routine quality control. Conventional techniques for measuring locations and widths of line spread functions require high precision digitization, usually via external analogue to digital converters. A technique is described for accurate measurement of peak location and width using coarsely sampled line spread functions. Results obtained for both simulated and actual gamma-camera data demonstrate that the method is capable of measuring peak deviations as small as 0.2 mm when the sampling interval is 1.5 mm or more. The precision of the method was found to be at least as good as conventional techniques. It is suggested that using the method accurate measurements of linearity can be made from a conventional 256 x 256 nuclear medicine image of a slit mask, and this enables routine evaluation of an important parameter of camera performance. (author)

[en] The efficacy of wipe tests for assessing ⁹⁹Tc^m surface contamination was measured. Four types of surface were contaminated with four radiopharmaceuticals and wiped using four types of swab. The fraction of activity removed was measured by direct monitoring for each combination of surface, pharmaceutical and swab. The results obtained showed that wipe tests are neither accurate nor precise. Observed wipe efficacies differed greatly from the customary assumption that 10% of the activity is removed by wiping. Detergent soaked swabs gave a mean efficacy of 40%, although with considerable variation (coefficient of variation 49%). Using these swabs alone the surface type affected efficacy by almost a factor three of (floor tile mean efficacy 20%, plastic laminate mean efficacy 57%). In principle this effect might be compensated for by using correction factors according to the surface being swabbed. However, the pharmaceutical type will generally be unknown, and this also affected efficacy by almost a factor of two (eluate mean efficacy 29%, macroaggregated albumin 53%). Overall the results suggest that wipe tests can be used to detect contamination but are unreliable for quantification. (author)

[en] The uptake of ₉₉Tcsup(m)-labelled colloid by the liver has been used to compare two methods of estimating the uptake rate constant from experimental data. For the authors' model, the non-linear curve fitting proved more accurate and precise than the linear fitting. (U.K.)

[en] Lymphoscintigraphy using sup(99m)Tc colloids has been proposed as a simple adjunct to lymphangiography. To validate the technique of subcutaneous injection we performed a direct comparison between intralymphatic and subcutaneous administration of sup(99m)Tc-antimony colloid. In all cases excellent correspondence was obtained between the two techniques. Lymphoscintigraphy does not provide the same morphological information as lymphangiography, but can provide useful data regarding lymphatic obstruction. (author)

[en] A new approach to ventilation imaging of the lung using ¹³³Xe in patients with suspected pulmonary embolism is described. Three inhalation images are obtained in the postero-anterior, right posterior oblique and left posterior oblique projections, respectively, and each image contains 140-180 kcounts. The technique is quick and simple and needs neither an oxygen supply nor a spirometer. It combines the multiple views characteristic of krypton imaging with the ease of availability of xenon. (author)