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Results for “Radioactive Tracers”

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PubMed1987

Possible role of vacuum systems and compressed air generators in cross-infection in the ICU. A radioactive tracer study.

Cross-contamination between a hospital's vacuum and compressed air systems was demonstrated using xenon-133 as a tracer. A xenon-133 bolus was introduced to the vacuum system in the intensive care unit. Calculations based on the amount of radioactive tracer recovered from the compressed air outlet at the same location as that at which the tracer was introduced indicated that 17% of the tracer had entered the compressed air system. The contamination was caused because the vacuum and compressed air systems were located in the same machine room. This could conceivably provide a route for respiratory tract contamination in patients receiving ventilatory assistance with air-oxygen mixtures.

Air↗
PubMed1975

Editorial: Guidelines for radioactive tracer studies of the heart and circulation. Report of the Inter-society Commission for Heart Disease Resources.

The Inter-Society Commission for Heart Disease Resources report concerning optimal resource guidelines for radioactive tracer studies of the heart and circulation is described. This report is an overview of the status of cardiovascular radionuclide diagnostic studies as well as a guideline to the hospital resources (physical and human) required for a high-quality nuclear medicine laboratory dealing with this area of study. These guidelines are directed to physicians and hospital administrators who are currently responsible for planning and organizing nuclear medicine programs or who anticipate a future need for such services in their community.

Cardiovascular Diseases↗
PubMed1978

Length dependence in reassociation kinetics of radioactive tracer DNA.

The reassociation kinetics have been measured for radioactive Escherichia coli DNAs (tracers) of various average single-strand lengths reassociated alone and in the presence of excess unlabeled DNA (driver) of two different average lengths. Hydroxylapatite binding was used to follow the reaction time course. The length-dependence of the rate constant determined in the tracer self-reassociation reactions is in agreement with the square-root dependence previously determined (Wetmur, J. G., & Davisond, N. (1968) J. Mol. Biol. 31, 349-370) using optical methods to follow the time course. However, for the driver-tracer reactions, where the radioactive DNA reassociates largely with DNA of a different average length, the dependence of the rate constant upon average tracer length is increased and approaches an L to the first power dependence. In 0.18 M Na+, the variation of the rate constant for tracer reassociation with the lengths of the reassociating strands has been shown to fit the simple equation k = (9.0077).(L T 0.55 + 1/L D 0.55), where k is the observed rate constant in L mol-1 s-1 and L(T)and L(D) are the weight average tracer and driver lengths, respectively, in nucleotides. This dependence suggests that the rate of nucleation of two free strands is proportional to the sum of the reciprocals of the hydrodynamic radii of the two strands.

Base Sequence↗
PubMed1994

The measurement of blood flow in humans using radioactive tracers.

Since the first description of the movement of blood around the body by William Harvey, the accurate measurement of blood velocity has provided a major challenge for medical science. This review looks at the contribution made by techniques using radioactive tracers. Initially consideration is given to the fundamental problem of how to measure the amount of radiotracer in an organ with sufficient accuracy, using both single-photon and positron-emitting tracers. The various models used to link tracer behaviour with blood flow are then discussed and the article closes with a detailed review of the clinical applications of blood flow measurements.

Animals↗
PubMed1998

A new method for measuring aerosol nebulizer output using radioactive tracers.

Reproducibility and comparability of bronchial challenge tests depends critically on accurate assessment of nebulizer output. Evaporation during nebulization means that simple weighing is inaccurate, overestimating the delivered dose of active ingredient. We wanted to quantify this effect in the context of intermittent nebulization, using a dosimeter as used in bronchial provocation tests. Output of three types of nebulizer, from the MEFAR dosimeter, was measured by radioactive tracer, using a standard solution of technetium-99m-pertechnetate (1.5 kBq x mL(-1)) in 4 mL of normal saline. The aerosol was impacted by suction onto a microfilter, and the radioactivity measured. Nebulizers were weighed before and after nebulization. Ratio of nebulized volume calculated from the radioactivity on the filter, to the total volume loss by weight, was expressed as nebulized ratio. The effect on output of two concentrations of methacholine, two tracers of different weights, and change in temperature, were assessed. Nebulized ratio varied between 44.1-71.6%. Results were more consistent within the same type of nebulizer than between different makes. Neither changes in molar concentration nor molecular weight affected nebulizer output or nebulized ratio. Mean nebulized ratio was 58.5%, showing that calibration by weighing, overestimates the delivered dose by a factor of approximately two. Measuring radioactivity eluted from a microfilter, onto which nebulized output had been impacted proved to be a satisfactory method of calibration.

Aerosols↗
PubMedDate not supplied

[Validation protocol of sentinel node biopsy for breast cancer using radioactive tracer at the Institute of Oncology Bucharest "Prof. Dr. Alexandru Trestioreanu"].

The sentinel ganglion concept originates in the assumption according to which the primary tumor drains into a specific lymph node area and then runs through the lymphatic nodes in an orderly, sequential mode. When neoplastic dissemination along the lymphatic pathway occurs, there is an initial invasion of a specific lymph node (rarely more than one) located on the drainage route. That first lymph node has been identified as the sentinel node, which mirrors the regional lymph node status. In order to establish the indication for lymphadenectomy and avoid the situations in which such a surgical procedure would be of no use (N-), the only correct method consists in the identification and biopsy of the sentinel node which can be performed using vital staining (blue dye), radioactive tracers or both. The technique of sentinel lymph node identification and biopsy by means of radioactive tracing includes: -pre-surgical lymphoscintigraphy, -identification of the sentinel lymph node and its excisional biopsy, -intra-operative histopathological examination, paraffin embedded sections and immunohistochemical stains of the sentinel lymph node. The paper presents the refinement of the technique and the validation of the method for identification and biopsy of the sentinel lymph node in breast cancer with the intra-operative use of NEOPROBE 2000 gamma probe at the "Prof. Dr. Alexandru Trestioreanu" Oncological Institute in Bucharest. It is a prospective study which enrolled 93 patients with breast cancer between September 2003-December 2005, who underwent sentinel node biopsy. Complete axillary dissection (back-up lymphadenectomy) was performed in all cases. By comparing the pathological results of the frozen section of the sentinel node, with the paraffin embedded and immunohistochemical ones of the remaining axillary nodes, we present the following results: sensibility 97,15% (34/35), specificity 100% (93/93), positive predictive value 100% (34/34), negative predictive value 98,3% (58/59).

Axilla↗
PubMed2001

Improving the seal of amalgam cores with cemented dowels: a comparative in vitro radioactive tracer study.

Amalgam cores with cemented dowels are commonly used to restore endodontically treated teeth. These restorations were widely studied for their mechanical properties; however, less is known about their sealing ability. The effect of the cement type used for the dowel and that of a bonding agent application were studied in a radioactive tracer coronal leakage study. The sealing ability of posts and cores was also compared with that of 5 mm remaining root canal fillings. Composite luting cement provided a better seal than zinc phosphate cement. The seal provided by 5 mm root canal fillings was poorer than that provided by posts and cores. High variability in seal quality was found among all types of posts and cores studied. This may indicate that the seal provided by cemented dowels with amalgam cores is unpredictable. Because neither the remaining root canal filling nor the post and core may be trusted alone for a seal, each should be performed with the greatest care and both covered with a crown as soon as possible.

Bicuspid↗
PubMed2004

Blue dye versus combined blue dye-radioactive tracer technique in detection of sentinel lymph node in breast cancer.

BACKGROUND: Sentinel lymph node biopsy in breast cancer can be used to select patients in which axillary lymph node dissection could be avoided. In this study we compared the value of two methods for identification of sentinel node (SN) using either only blue dye or combination of blue dye and radioactive tracer. MATERIAL AND METHODS: All patients were women with clinically T(1-2)N(0)M(0) breast cancer. They were randomized into two groups. In Group A (50 patients) SN marking was performed only with blue dye and in Group B (100 patients) combined SN marking with blue dye and radiotracer was done. We used 2 ml of blue dye Patentblau V (Byk Gulden). Radiotracer was Antimony sulfide marked with Tc 99m and of 0.3 mCy (11.1 MBq) activity. Application method of both contrasts was peritumoral. After SN biopsy all patients underwent mastectomy or conservative surgery with axillary lymph node dissection of levels I and II. RESULTS: In Group A mean of 1.7 SNs were identified (median 1, range 1-4). False-negative rate in this group was 3/17 (17.6%) with negative-predictive value 20/23 (86.9%), sensitivity 14/17 (82%), specificity 20/33 (60%) and accuracy 34/50 (68%). In Group B mean number of SNs excised per case was 1.6 (median 1, range 1-5). False-negative rate was 2/44 (4.5%), negative-predictive value 41/43 (95.3%), sensitivity 42/44 (95%), specificity 41/56 (73%) and accuracy 83/100 (83%). The combination technique was significantly superior to blue-dye alone technique for negative-predictive value (p=0.033) and overall accuracy (p=0.048). CONCLUSIONS: The prediction of axillary lymph node status in breast cancer patients using combined technique has significantly higher accuracy than marking of SN with blue dye alone and therefore should be preferred.

Adult↗
PubMed2000

Sorption Studies of Cobalt(II) on Colloidal Hematite Using Potentiometry and Radioactive Tracer Technique.

The sorption of Co(II) on colloidal hematite was studied as a function of pH, ionic strength, and Co(II) concentration. Two different techniques were used, yielding two different sets of information: (i) potentiometric titrations that provide information on the number of protons released as a function of pH owing to the sorption of Co(II) and (ii) measurement of the amount of cobalt sorbed on the surface as a function of pH using a radioactive tracer, (60)Co. At low Co(II) concentrations (10(-8) M), the sorption was found to be independent of ionic strength but there seems to be a weak ionic strength dependence at higher Co(II) concentrations (10(-4) M). The adsorption edge moved to higher pH with increasing Co(II) concentration. For the high Co(II) concentration, the number of protons released per cobalt sorbed increased from zero to approximately 1.5. The basic charging properties of hematite were modeled with four different surface complexation models. The 1-pK Basic Stern Model (BSM), with binding of electrolyte ions to the Stern plane, seems to be the most reasonable model if the ambition is to describe experimental data at different ionic strengths. The sorption of cobalt was modeled with the 1-pK BSM. By introducing a low concentration of high affinity surface sites for cobalt sorption it was possible to model the sorption in very wide cobalt concentrations, ranging from 10(-8) M to 10(-4) M. Copyright 2000 Academic Press.

Journal Article↗
PubMed1993

The relationship between inert gas wash-out and radioactive tracer microspheres in measurement of bone blood flow: effect of decreased arterial supply and venous congestion on bone blood flow in an animal model.

Several methods have been employed in the study of bone perfusion. We used a method of determining inert gas wash-out by mass spectrometry in the study of blood flow rates in pigs. The method was validated by comparison of the result obtained with inert gas wash-out to that with measurement by microspheres. Furthermore, the effect of decreased inlet flow and venous congestion on the bone perfusion data was tested. The undisturbed bone blood flow was not significantly different when measured with wash-out of inert gas (7 +/- 0.7 ml/min/100 g) or with microspheres (9 +/- 2.9 ml/min/100 g), and the methods were correlated. Perfusion was reduced significantly, to 20% of the original value, after arterial occlusion. The changes in wash-out curves and accumulation of radioactive tracer provided substantial evidence for impaired intraosseous circulation following venous obstruction also. In conclusion, the study showed that this method of determining inert gas wash-out is feasible for studies of local perfusion rates in bone. The flow rates obtained by wash-out correlated well with the results of microsphere studies. In this animal model, both methods detected a fivefold reduction in flow rate after clamping of the arterial inflow. Obstruction of the venous outflow also impaired blood flow and lowered the cellular supply.

Animals↗