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Biomedical subjects

S E Strand

Publications and source records attributed to S E Strand.

At least 109 records · Page 6Linked to original sources
PubMed1983

A comparison of two methods of labelling autologous platelets with 111In-oxine in five different species.

Several different methods for labelling autologous platelets with 111In-oxine have been described. However, no comparative study has been reported. In the present investigation two different labelling methods were compared in terms of labelling efficiency and platelet function in five species: human, dog, pig, rabbit and rat. One of the labelling methods, utilising among other things a serum albumin gradient separation of platelets and incubation of 111In-oxine in a water bath at 37 degrees C, was superior in all species with significantly higher labelling efficiency and unchanged platelet function.

Animals↗
PubMed1983

Diagnosis of deep venous thrombosis by 99mTc-human serum albumin microcolloid.

99mTc-human serum albumin microcolloid (HSAC) was evaluated for diagnosis of deep venous thrombosis (DVT) in the legs of 38 consecutive patients. Five and thirty minutes after IV injection, the 99mTc-HSAC activity in both legs was measured by external counting using a collimated NaI (T1)-detector. The relative predominance of 99mTc-HSAC activity in the diseased leg was calculated. Phlebography was performed as a control after the 99mTc-HSAC test. In our hands the non-invasive 99mTc-HSAC test appeared to be rapid, easy to perform and convenient to the patient. The test showed a high sensitivity (11/13) and a low specificity (10/20) compared with phlebography. No adverse reactions were found. The results seem promising and further studies are in progress to establish the value of the 99mTc-HSAC test in screening for DVT.

Adult↗
PubMed1983

Reticuloendothelial function in normal and tumor-bearing rats. Measurements with a scintillation camera technique.

The function of the reticuloendothelial system (RES) was evaluated after the inoculation of an experimental tumor in rats. Four groups were studied according to tumor size and site. Reticuloendothelial function was evaluated by measuring the biokinetics of a standardized [99Tcm]-sulfur colloid. Estimation of the uptake rate of the labeled colloid into the liver and other parts of the RES was performed through the use of a two-compartment model. Animals with small liver or subcutaneous tumors showed an increased activity of both the hepatic and the extrahepatic RES. Animals with large retroperitoneal tumors showed a significant decrease in the RE function of the liver. In these animals the function of the extrahepatic RES was not changed compared to controls but was, however, significantly decreased compared to animals with smaller tumors. The findings may reflect a difference in the impact of tumor size on RE function extra- and intrahepatically.

Animals↗
PubMed1983

Particle sizing and biokinetics of interstitial lymphoscintigraphic agents.

The biokinetics of inert lymphoscintigraphic agents strongly depends on their particle size. Different techniques for characterization of colloids are discussed. Experiments have been performed on eight different colloids. The particle size has been investigated with scanning electron microscopy. Activity distributions have been obtained with ultrafiltration and gel-column scanning technique. The colloids suggested for lymphoscintigraphy were found to have a median size of about 40-50 nm except one minimicro-aggregated human serum albumin colloid which has a median particle size around 10 nm. The biokinetics were studied with a scintillation camera in rabbits after a subcutaneous injection. Time-activity curves were generated. After 5 hr the rabbits were dissected and the activity content in different tissues measured. A compartment model for the biokinetics was designed and rate constants evaluated. The total and specific activity uptake in parasternal lymph nodes was highest for the small-particle colloids. The compartment model showed a good fitting to the experimental data.

Absorption↗
PubMed1982

A scintillation camera technique for measurements of the reticuloendothelial function - comparison of different methods for measuring RES function.

A highly standardized 99mTc-sulphur colloid was used to evaluate reticuloendothelial system (RES)-function in the normal rat and after RE blockade by gelatin (Haemaccel). Activity distribution in the animals was measured with a scintillation camera technique. Total uptake of activity in the liver was estimated. From the time-activity curves over the liver, the phagocytic index (kphag) was evaluated. Estimation of the uptake rate of the labelled colloid into the liver and into other parts of the RES was also performed using a two-compartment model. Different methods of evaluation of RE function were compared. It was shown that for a proper estimation of the RE function, the whole uptake curve must be considered. Gelatin (Haemaccel) significantly reduced the total colloid uptake by the liver. The colloid uptake rate into the liver was also significantly reduced. Liver specimens after colloid injection were examined by light and electron microscopy showing vacuolation of hepatocytes and sinusoidal cells probably due to pinocytosis. The technique described enables functional studies of the RES. It has the advantage of noninvasive registrations and is based on the same technical facilities as used for routine liver scintigraphy.

Animals↗
PubMed1982

Dosimetry in lymphoscintigraphy of Tc-99m antimony sulfide colloid.

A quantitative kinetic technique using a scintillation camera has been developed for investigating lymph drainage and the uptake in the lymph nodes of 99mTcSb2S3 colloid injected subcutaneously. Twenty-two patients with primary malignant melanoma were examined. Lymph-node dissection was performed and 185 lymph nodes were individually measured for radioactivity. The kinetics of colloid uptake in individual nodes can be expressed by a simple two-compartment model. The outflow of colloid from the injection site was found to be monoexponential, and the tissue volume containing the injected colloid at the injection site increased asymptotically with time. A model has been developed for calculating absorbed doses at the injection site and in organs with colloid uptake. The following absorbed doses were estimated (muGy/MBq): whole body 0.7-4.5, gonads 0-22, liver 1.0-3.9, lymph nodes up to 1000 and injection site about 10,000. Possible biological effects in the skin and effective dose equivalents have been estimated when using other lymphoscintigraphic agents.

Antimony↗
PubMed1980

Theoretical studies of image artifacts and counting losses for different photon fluence rates and pulse-height distributions in single-crystal NaI(T1) scintillation cameras.

Using computer simulations, we have developed a theoretical model to explain the correlation between counting losses and image artifacts in single-crystal NaI(T1) scintillation cameras. The theory, valid for scintillation cameras of the Anger type, is based on the physical properties of the NaI(T1) crystal. Based on a statistical model using random numbers, pulse trains of the light pulses from scintillations were simulated. Pulse-height distributions for different event rates were calculated, with various Compton distributions. Images of point sources and line sources were generated. Counting losses and image artifacts were dependent on the shape of the pulse-height distribution. The calculated counting losses decreased with larger Compton distributions, due to increasing numbers of pileup events in the energy window; this also caused severe image distortion. The improvement of the spatial resolution with pileup rejection was demonstrated. The theoretical results are in good agreement with experimental results obtained previously. It is concluded that, in modern cameras, the decay time of the scintillation determines the amount of pileup, and the resolving time of the electronics governs the count rates. The results indicate that in some modern cameras the limits of the count-rate capacity in Anger cameras may be reached.

Elementary Particles↗
PubMed1979

Quantitative lymphoscintigraphy I: Basic concepts for optimal uptake of radiocolloids in the parasternal lymph nodes of rabbits.

The activity-size distribution of radiocolloids has been studied using gel-chromatography scanning (GCS) of columns filled with Sepharose 4B gel. Rabbits were injected subcutaneously with the colloid of interest, laid supine beneath a gamma camera, and imaged every 15 sec for 2 to 4 hr. From the stored data, the uptakes in the parasternal lymph nodes were analyzed in terms of two-compartment model, and the rate constants measured. The substances tested were Au- 198 colloid, Tc-99m antimony sulfide colloid, Tc-99m tin colloid, Tc-99m phytate, and Tc-99m sulfur colloid. It was shown that the optimal particle size for the colloid in the range 1-10 nm. The large and most rapid uptake was found for Au- 198 colloid, with a particle size of 5 nm, which appeared as a single peak in the GCS spectrum. The percentage uptake after 2 hr for Au- 198 colloid 8%, while it was 5% for antimony-sulfide colloid, which was the best of the Tc-99m-labeled colloids. The GCS spectrum for the antimony product showed a single-peaked size distribution with a somewhat broader range: 5-15 nm. The particles of the other colloids were either too large to pass into the lymphatic system, or too small to be trapped.

Animals↗
PubMed1978

Quantitative lymphoscintigraphy for detection of metastases to the internal mammary lymph nodes. Biokinetics of 99Tcm-sulphur colloid uptake and correlation with microscopy.

Dymanic quantitative activity determination and accurate scintigraphic localization of parasternal lymph nodes were obtained from antero-posterior measurements with a scintillation camera. The scintigraphic observations were compared with microscopy of the nodes removed at operation. The 99Tcm-sulphur colloid indicated a high frequency (7/16) of absent uptake in normal lymph nodes. However, the technique used indicates that a similar technique with smaller particle size may be a useful method for proper classification of the clinical stage of carcinoma of the breast.

Breast Neoplasms↗
PubMed1978

Image artifacts at high photon fluence rates in single-crystal NaI(T1) scintillation cameras.

A method that simulates a clinically relevant situation is used to measure the amount of pulse pileup in the gamma image by distinguishing between correctly and incorrectly positioned events. Comparison was then made between responses from different cameras. These investigations show the influence of pileup rejection on counting rate. Pileup effects can be determined for some cameras at such low count rates as about 10,000/sec with a 30% energy window. Parameters affecting the total count rate of the scintillation camera--such as scattering media, source geometry, collimator, and energy window--have been investigated. It is shown that the energy distribution of the photon fluence striking the crystal determines the counting losses and image distortion, rather than the counting rate in the energy window. The approach described here might fulfill the requirements for a new method to compare scintillation cameras. It is important to note that measurements without scattering medium yield results irrelevant for clinical situations.

Radionuclide Imaging↗
PubMed1977

The dual photopeak-area method applied to scintillation camera measurements of effective depth and activity of in vivo 123I-distributions.

Attenuation curves and photopeak ratios of 159 keV and 28 keV photons emitted in the decay of 123I have been studied using a scintillation camera equipped with an extra ADC for recording the pulse height distribution of the energy signal. Cavities of various sizes containing 123I-solution were placed at different depths in a water phantom in order to vary the effective depth i.e., the thickness of attenuating material above the cavity plus the distance to the centre of activity in the cavity. The centre of activity varies with the distribution of activity in the cavity, size of cavity, and the effective attenuation coefficient derived from the attenuation curves. From the photopeak ratio an average effective depth is determined which can be used for calculating the attenuation correction factor. The dual photopeak ratio has been used in clinical evaluation of thyoid 123I uptake measurements where effective depths ranging from 21 to 43 mm were obtained for the activity in the thyroid. Applications of the photopeak ratio method for renography with 123I-hippuran and blood flow studies using 133Xe or 127Xe and studies with many other radionuclides are also discussed.

Adult↗
PubMed1977

Imaging 123I with a scintillation camera. A study of detection performance and quality factor concepts.

Image quality, resolution and sensitivity of a scintillation camera equipped with various collimators have been investigated using high purity 123I. Pulse height distributions of 123I from a thyroid phantom partly in air and partly immersed in water demonstrate the substantial septa penetration of the 440 and 529 keV gamma rays of 123I with high resolution collimators. Line spread functions recorded first with the line source in air and then in water show that the area under the 'wings' is attributed mainly to septa penetration but with a marked contribution from scattering in water. The modulation transfer function evaluated from the line spread functions shows a sudden drop at low frequencies for high resolution collimators due to their high degree of septa penetration. The two concepts of 'figure of merit' also used are Qb=Sa [MTF]2, where Sa is the plane sensitivity and Qc=S2/(S+2B), where S is the true signal from the object and B is the total background or noise due to septa penetration and scatter. The image reproduction per unit time which is described by Qb is best for a high resolution converging collimator. The statistical accuracy per unit time which is used in dynamic studies is described by Qc and is best for a medium energy collimator.

Air↗
PubMed1976

Repeat scintigraphy of the internal mammary lymph nodes in rabbits.

Rabbits were subjected to different combinations of scintigraphy of the internal mammary lymph nodes, fractionated irradiation, and surgical trauma to the chest wall. No influence could be demonstrated on the image at repeat scintigraphy of the internal mammary nodes. Microscopic changes in the lymph nodes and vessels were relatively slight and inconstant.

Animals↗
PubMed1975

A scintillation camera technique for quantitative estimation of separate kidney function and its use before nephrectomy.

A scintillation camera technique was used for measuring renal uptake of [131I]Hippuran 80-110 s after injection. Externally measured Hippuran uptake was markedly influenced by kidney depth, which was measured by lateral-view image after injection of [99mTc]iron ascorbic acid complex or [197Hg]chlormerodrine. When one kidney was nearer to the dorsal surface of the body than the other, it was necessary to correct the externally measured Hippuran uptake for kidney depth to obtain reliable information on the true partition of Hippuran between the two kidneys. In some patients the glomerular filtration rate (GFR) was measured before and after nephrectomy. Measured postoperative GFR was compared with preoperatively predicted GFR, which was calculated by multiplying the preoperative Hippuran uptake of the kidney to be left in situ, as a fraction of the preoperative Hippuran uptake of both kidneys, by the measured preoperative GFR. The measured postoperative GFR was usually moderately higher than the preoperatively predicted GFR. The difference could be explained by a postoperative compensatory increase in function of the remaining kidney. Thus, the present method offers a possibility of estimating separate kidney function without arterial or ureteric catheterization.

Adult↗
PubMedDate not supplied

Pharmacokinetic modeling.

For radiation dosimetry calculations of radiolabeled monoclonal antibodies, (MAB), pharmacokinetics are critical. Specifically, pharmacokinetic modeling is a useful component of estimation of cumulated activity in various source organs in the body. It is thus important to formulate general methods of pharmacokinetic modeling and of pharmacokinetic data reduction, leading to cumulated activities. In this paper different types of models are characterized as "empirical," "analytical," and "compartmental" pharmacokinetic models. There remains a pressing need for quantitative studies in man for a proper understanding of the pharmacokinetics of MAb. Pharmacokinetic modeling of radiolabeled MAb in vivo has relied on relatively limited studies in man and complementary detailed measurements in animals. In either case, any model chosen for analysis of such data is inevitably based on measurements of limited accuracy and precision as well as assumptions regarding human physiology. Very few macroscopic compartmental pharmacokinetic models for MAb, have been tested over a range of conditions to determine their predictive ability. Extracorporeal immunoadsorption represents one approach for drastically altering the biokinetics of antibody distribution, and may serve to validate a given pharmacokinetic model. In addition to macroscopic modeling, the microscopic evaluation of the time-dependent distribution of radiolabeled MAb in tissues is of utmost importance for a proper understanding of the kinetics and radiobiologic effect. Many tumors do not exhibit homogeneous uptake. A mathematical understanding of that distribution is thus essential for accurate tumor dosimetry estimates. This review summarizes methodologies for pharmacokinetic modeling, critically reviews specific pharmacokinetic models and demonstrates the capability of modeling for predictive calculations of altered pharmacokinetics, emphasizing its use in dosimetric calculations.

Animals↗
PubMedDate not supplied

Considerations on the calibration of small thermoluminescent dosimeters used for measurement of beta particle absorbed doses in liquid environments.

An investigation has been carried out on the factors which affect the absolute calibration of thermoluminescent dosimeters (TLDs) used in beta particle absorbed dose evaluations. Four effects on light output (LO) were considered: decay of detector sensitivity with time, finite TLD volume, dose linearity, and energy dependence. Most important of these was the decay of LO with time in culture medium, muscle tissue, and gels. This permanent loss of sensitivity was as large as an order of magnitude over a 21-day interval for the nominally 20-microns-thick disc-shaped CaSO4(Dy) TLDs in gel. Associated leaching of the dosimeter crystals out of the Teflon matrix was observed using scanning electron microscopy. Large channels leading from the outside environment into the TLDs were identified using SEM images. A possibility of batch dependence of fading was indicated. The second most important effect was the apparent reduction of light output due to finite size and increased specific gravity of the dosimeter (volume effect). We estimated this term by calculations as 10% in standard "mini" rods for beta particles from 90Y, but nearly a factor of 3 for 131I beta particles in the same geometry. No significant nonlinearity of the log (light output) with log (absorbed dose) over the range 0.05-20.00 Gy was discovered. Energy dependence of the LO was found to be not detectable, within measurement errors, over the range of 0.60-6.0 MeV mean energy electrons. With careful understanding of these effects, calibration via gel phantom would appear to be an acceptable strategy for mini TLDs used in beta absorbed dose evaluations in media.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta Particles↗
PubMedDate not supplied

Prospective investigation of radiologic methods in the diagnosis of intra-abdominal abscesses.

A prospective investigation of conventional abdominal radiography, ultrasonography, computed tomography and 111In-labelled leucocyte scintigraphy was performed in 40 patients suspected of having an intra-abdominal abscess. There were 23 confirmed abscesses in the material. When conventional abdominal radiography indicated an abscess, such a lesion was usually present. The ability of abdominal radiography to exclude an abscess was, however, low. Both ultrasonography and 111In-labelled leucocyte scintigraphy detected 65 to 85 per cent of the confirmed abscesses, but both also revealed many abscess-like areas in patients where no unequivocal abscess was confirmed at follow-up. Computed tomography was, when employed as a single method, the most reliable one both to show and to exclude an abscess, However, the combination of ultrasonography and 111In-labelled leucocyte scintigraphy disclosed all the lesions demonstrated by any one of the four methods used in the investigation.

Abdomen↗