Intraoperative scintigraphy in surgical treatment of thyroid carcinoma: evaluation of a new technique.
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Adenocarcinoma↗
Biomedical subjects
J Persliden
Publications and source records attributed to J Persliden.
Generalised use of contrast degradation and contrast improvement factors in diagnostic radiology. Application to vanishing contrast.
Although field area and object thickness are important parameters in comparisons of techniques for optimal reduction of scattered radiation to the image, they are in practice seldom varied. For this reason, we suggest that contrast degradation (CDF) and contrast improvement (CIF) factors be more frequently used and appropriately defined to make the dependence of CDF and CIF on field area (collimation) and object thickness (compression) explicit. Definitions are formulated and the results of experiments and Monte Carlo calculations (comprising effects of collimation, compression, air gap, antiscatter grid, detector thickness) cited to illustrate their usefulness. Currently used expressions for CIF (derived assuming monoenergetic radiation) lack a factor to account for the change in primary contrast caused by the antiscatter method when this affects the energy distribution of the transmitted primary photons (grids and compression) or the fractions of photon energy imparted to the detector (when comparing different detectors). Values of this factor are calculated for some cases. Also, the appropriate choice of physical quantity to be used in the formulae for CDF and CIF is discussed. The energy imparted to the detector is advocated since this is directly related to the detector signals forming the image on, e.g. the x-ray film.
Humans↗
Ultrastructural morphology and evidence of iodide uptake and protein synthesis in normal human thyroid transplants in nude mice.
Normal human thyroid tissue was xenotransplanted to athymic mice. Well preserved structural properties of the transplants were observed at both light and electron microscopical level. Analysis of the soluble proteins in the transplants by polyacrylamide gel electrophoresis showed that the major fractions were the 19S thyroglobulin, the 27S iodoprotein and a larger protein fraction. Protein synthesizing capacity of the transplants, as measured by in vivo 3H-leucine incorporation into the soluble transplants proteins was demonstrated. The observed 3H-leucine incorporation was in the same magnitude as that found in the original donor tissue at the time of transplantation. Four weeks after transplantation a significant 125I-iodide uptake (2.0%) was observed in the transplants. Corresponding value for the host thyroids was 6.6%. The biological half-time of the accumulated 125I-iodide in the transplants was reduced from 97 days to 38 days between 2 and 4 weeks after transplantation. The biological half-time in the host thyroid increased from 27 days to 32 days during the same period. This investigation shows that normal human thyroid tissue can be transplanted to nude mice with preserved tissue organisation and maintained cellular function.
Animals↗
Energy imparted to the patient in diagnostic radiology: calculation of conversion factors for determining the energy imparted from measurements of the air collision kerma integrated over beam area.
The energy imparted to the patient in diagnostic radiology, related to radiation risk in examinations of the trunk and head, can be deduced from a measurement of the air collision kerma (or exposure) of the incident primary photons integrated over beam area by using a thin, flat ionisation chamber covering the entire roentgen beam. Factors for converting the integral of the air collision kerma to energy imparted to the patient have been calculated using a Monte Carlo method. The patient is simulated by laterally infinite water slabs with thicknesses from 100-300 mm. Calculations are performed for monoenergetic photons (5-300 keV) and energy spectra commonly used in diagnostic radiology (40-130 kV acceleration potential differences and values of the half-value thickness of air collision kerma in aluminium from 0.9 to 9.9 mm). Correction factors which take into account the additional escape of scattered photons from the sides of a laterally finite water slab as a function of field size and focal distance are also given.
Humans↗
Energy imparted to water slabs by photons in the energy range 5-300 keV. Calculations using a Monte Carlo photon transport model.
In diagnostic examinations of the trunk and head, the energy imparted to the patient is related to the radiation risk. In this work, the energy imparted to laterally infinite, 10-300 mm thick water slabs by 5-300 keV photons is calculated using a Monte Carlo photon transport model. The energy imparted is also derived for energy spectra of primary photons relevant to diagnostic radiology. In addition to values of energy imparted, values of backscattered and transmitted energies, quantities primarily obtained in the transport calculations, are reported. Assumptions about coherent scattering are shown to be important for values of backscattered and transmitted energies but unimportant with respect to values of energy imparted. Comparisons are made with other Monte Carlo results from the literature. Discrepancies of 10-20% in some calculated quantities can be traced back to the use of different tabulations of interaction cross-sections by various authors.
Humans↗
The nude mouse. A possible experimental model for investigation of human thyroid tissue.
The effect of transplanting hyperfunctioning human thyroid tissue to athymic, nude mice was explored. The thyroid tissue was obtained from a patient with diffuse, thyrotoxic goiter preoperatively treated with a beta-adrenoreceptor blocker. One transplant was placed in each groin of 4 nude mice. Light microscopy after 4 weeks showed that transplants consisted mainly of typical follicles; capillaries were common at the periphery of the transplant but not in between the follicles. The ultrastructure of the follicle cells in the transplants was similar to that of follicle cells in general. All 8 transplants accumulated 125I as revealed by external counting; the uptake in each transplant 24 h after administration of radioiodine was 4-25% of that in the thyroid of the transplanted mouse. The release of radioiodine, measured during a period of 14 days, from the thyroid of a transplanted mouse was delayed as compared to a nontransplanted control; this indicates that the mouse thyroid activity was suppressed due to hormone production in the transplants. Electron microscopic autoradiography 24 h after injection of 125I showed that protein-bound label in transplants was located mainly in follicle lumens. The radioiodine was incorporated in thyroglobulin as demonstrated by separation of soluble proteins from transplants by sucrose density gradient centrifugation. The present study shows that human thyroid tissue can be transplanted to nude mice with maintained structural and functional properties. Transplantation of human thyroid tissue might be a useful model for studies of thyroid diseases.
Animals↗
A Monte Carlo program for photon transport using analogue sampling of scattering angle in coherent and incoherent scattering processes.
A computer program was developed for the Monte Carlo simulation of photon transport. The program was designed for photon transport simulation in geometries occurring in diagnostic radiology and especially for the investigation of scattered radiation. A method is described for the analogue sampling of scattering angle in coherent and incoherent scattering processes. The two scattering processes are treated separately, and the influence of coherent scattering, an often neglected process, can be estimated quantitatively. The program can also be used for the calculation of the energy imparted to water slabs and fluorescent screens.
Computers↗
Calculation of the small-angle distribution of scattered photons in diagnostic radiology using a Monte Carlo collision density estimator.
Calculations of various physical quantities pertaining to scattered photons in diagnostic radiology are conveniently carried out using the Monte Carlo technique. Some quantities, e.g., the small-angle distribution of scattered photons transmitted through the patient, are difficult to obtain with sufficient precision using straightforward simulation of physical experiments. By mixing the simulation of random trajectories with analytical calculations, the efficiency of deriving values for a particular field quantity may be drastically improved. This work describes a Monte Carlo collision density estimator that increases the efficiency of calculating the small-angle distribution of transmitted scattered photons by a factor of more than 50. Examples of such distributions outside laterally infinite water slabs are given for x rays generated at 40-70 kV and for various slab thicknesses (10-200 mm). Comparison with experimental results from the literature shows that cross sections for coherent scattering which take diffraction phenomena in liquid water into account must be used to get accurate results. A discrepancy between the experimental and calculated distributions of photons transmitted at very small (less than 3 degrees) angles to the normal to the slab may be interpreted in terms of experimental difficulties or insufficient accuracy in the differential scattering cross sections used in the calculations.
Humans↗
Radiographic joint space narrowing and histologic changes in a rabbit meniscectomy model of early knee osteoarthrosis.
The purpose of this study was to compare weightbearing radiographs with histologic cartilage evaluation in a rabbit meniscectomy model of the early stage of osteoarthrosis. Fifteen rabbits had a medial meniscectomy performed in one knee and a sham operation in the other knee. Five rabbits each were sacrificed at 13, 25, and 40 weeks after surgery. Radiographic joint space width and histologic cartilage changes of the medial knee compartment were quantified. Five non-operated knees and five knees in which the meniscus had been removed immediately before the evaluations served as control specimens. Overall, the joint space of the peripheral part of the medial knee compartment was narrower in knees operated on for meniscus removal than in sham-operated knees (P < 0.003). In the knees with the meniscus removed, more cartilage changes were seen at the joint surface area of contact on radiographs than in the sham-operated knees (P < 0.0015). Indeed, the area of contact had cartilage changes similar to those in the whole medial compartment. However, there was no correlation between the degree of histologic cartilage change and the corresponding joint space measurements. Joint space width as measured on weightbearing radiographs is reduced after meniscectomy in the rabbit, but it does not reflect the degree of cartilage damage of the loaded joint surfaces in early stages of osteoarthrosis.
Animals↗