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Sökning: L773:1473 5628

  • Resultat 1-10 av 42
  • [1]2345Nästa
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  • Almquist, H, et al. (författare)
  • Performance of simultaneous emission-transmission systems for attenuation-corrected SPEct: a method for validation applied to two camera systems
  • 2001
  • Ingår i: Nuclear Medicine Communications. - : Lippincott Williams & Wilkins. - 1473-5628. ; 22:7, s. 759-766
  • Tidskriftsartikel (refereegranskat)abstract
    • Several commercially available systems for attenuation correction in single photon emission computed tomography (SPECT) based on a transmission scan have been introduced that vary in performance. A test procedure for attenuation correction in SPECT is described and applied to two principally different gamma camera systems (the Siemens Multispect 3 triple-headed system [3HS] and the ADAC Genesys Vertex double-headed system [2HS]). The test procedure was based on geometrically well-defined phantoms. A torso phantom was used to illustrate the attenuation correction methods. The test procedure can be used without detailed knowledge of or access to the algorithms used for attenuation correction. The influence on the transmission measurement of radioactivity in a phantom was higher for the 2HS than for the 3HS. The 3HS produced satisfactory attenuation maps and corrected emission count rates to a constant value independent of phantom density and size. With the 2HS, there was a progressive decrease in the correction of emission count rates with increasing phantom density, and about 30% lower corrected count rates in the large compared with the small phantom. A decrease in measured attenuation coefficients in the vicinity of an emission source was demonstrated in large but not small phantoms. A likely explanation is erroneous correction of downscatter into the transmission energy window. This study demonstrates the need for independent evaluation of systems for attenuation correction in SPECT.
  • Back, Anna-Karin, et al. (författare)
  • Renography with a semiautomated algorithm for diuretic decision 7 min postradiopharmaceutical administration : a feasibility study
  • 2020
  • Ingår i: Nuclear medicine communications. - : LIPPINCOTT WILLIAMS & WILKINS. - 0143-3636 .- 1473-5628. ; 41:10, s. 1018-1025
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective The F+10 method for diuretic renography (diuretics given 10 min after the radiopharmaceutical) could be a time-conserving method. This method involves a 30-min dynamic acquisition where diuretics are administered only when necessary by the Nuclear Medicine technologist performing the examination. The purpose of this study was to assess the method's performance and to discover the optimal threshold of residual activity for a diuretic administration 7 min into the F+10 renography by reprocessing raw data from prior performed examinations with 20-min acquisitions without diuretics. Methods Retrospectively, raw data from 320 original examinations of adult patients performed from 2013 to 2015 were reprocessed into 7-min series and categorized as requiring diuretic or not. The diuretic decisions made by an expert panel were used as a reference. A receiver-operating characteristic curve was drawn to assess the optimal cutoff value for the residual renal activity. Sensitivity, specificity, positive and negative predictive values, as well as the Youden J index were calculated. Result The experts classified 50% (160 examinations) as in need of diuretics. The receiver-operating characteristic curve demonstrated the theoretical optimal cutoff value at 7 min to be 94% of maximum activity (sensitivity 0.93, specificity 0.81, Youden J index 0.73). A clinically acceptable threshold is suggested to be 85% (sensitivity 0.99, specificity 0.59, Youden J index 0.58). Conclusion Tc-99m-mercaptoacetyltriglycine renography with the F+10 method and the threshold 85% for diuretic decision 7 min into the renography is a feasible and acceptable method in clinical practice.
  • Barta, Pavel, et al. (författare)
  • Circumventing the requirement of binding saturation for receptor quantification using interaction kinetic extrapolation
  • 2011
  • Ingår i: Nuclear medicine communications. - 0143-3636 .- 1473-5628. ; 32:9, s. 863-867
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantification of the number of receptors per cell (NRPC) is important when assessing whether a tumor surface biomarker is suitable for medical imaging. One common method for NPRC quantification is to use a binding saturation assay, which is time consuming and requires large amounts of reagents. The aim of this study was to evaluate an alternative method based on kinetic extrapolation (KEX) and compare it with the classical manual saturation technique with regard to accuracy as well as time and reagent consumption. Epidermal growth factor receptor (EGFR) and HER2 receptor surface expression were quantified on five tumor cell lines using three (125)I-labeled and (131)I-labeled ligands (cetuximab and EGF for EGFR, trastuzumab for HER2 receptor) for both techniques. The KEX method involved interaction measurements in the LigandTracer, followed by KEX through computerized real-time interaction analysis to correct for nonsaturation on cells. Variability and NRPC estimates of the EGFR and HER2 receptor levels using the KEX method were comparable with the results from the classical saturation technique. However, the ligand consumption for the KEX method was 26-46% of the classical saturation technique. Furthermore, the KEX method reduced the workload radically. From the observations described in this study, we believe that the KEX method enables fast, credible, and easy NRPC quantification with a reduction in reagent consumption.
  • Begic, Amela, et al. (författare)
  • Impact of ventilation/perfusion single-photon emission computed tomography on treatment duration of pulmonary embolism.
  • 2015
  • Ingår i: Nuclear Medicine Communications. - : Lippincott Williams & Wilkins. - 1473-5628. ; 36:2, s. 162-167
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the study was to establish whether the duration of anticoagulant (AC) therapy can be tailored, on an objective basis, by using ventilation/perfusion single-photon emission computed tomography (V/P SPECT) and to assess the extent of residual perfusion defects over time. In particular, we addressed the following: (a) is the extent of perfusion recovery at 3 months of initial pulmonary embolism (PE) diagnosis a satisfactory criterion for deciding the duration of oral AC? (b) Is it safe to withdraw AC at 3 months if perfusion recovery is complete?
  • Begic, Amela, et al. (författare)
  • Tomographic ventilation/perfusion lung scintigraphy in the monitoring of the effect of treatment in pulmonary embolism: serial follow-up over a 6-month period.
  • 2011
  • Ingår i: Nuclear Medicine Communications. - : Lippincott Williams & Wilkins. - 1473-5628. ; 32, s. 508-514
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Pulmonary embolism (PE) is a severe condition with nonspecific symptoms. Diagnosis relies on medical imaging but follow-up is currently based on clinical symptoms and general risk factors. The duration of anticoagulant treatment after an acute episode of PE is still subject to debate and the best method of identifying the risk of recurrence in individual patients is undefined. Tomographic lung scintigraphy [ventilation/perfusion single photon emission computed tomography (V/P SPECT)] has improved the diagnostic accuracy with regard to PE but has not been evaluated for PE follow-up. AIM: The aim of this prospective study was to quantitatively follow the natural history of treated PE using V/P SPECT, which could prove helpful in defining an anticoagulant treatment regime for individual patients. METHODS: Of 83 consecutive patients with clinically suspected PE examined with V/P SPECT, 23 patients with confirmed PE were followed by serial V/P SPECT examinations over a 6-month period. All patients were also followed clinically. RESULTS: The mean relative decrease in PE extent compared with the time of diagnosis was 54±26% at 2 weeks, 79±30% at 3 months, and 82±30% at 6 months. Significant resolution of mismatched perfusion defects occurred between V/P SPECT controls within the first 3 months of anticoagulation (P<0.001) but not thereafter. V/P SPECT identified four patients with chronic PE, even though all patients were free from symptoms at 3-month follow-up. CONCLUSION: Follow-up of PE with V/P SPECT is feasible to evaluate treatment effectiveness in individual patients and to identify patients that develop chronic PE. This study also confirms that resolution of perfusion defects after PE occurs within the first 3 months of treatment. It is therefore recommended that V/P SPECT follow-up should be considered at 3 months after diagnosis.
  • Edwards, David, et al. (författare)
  • 99mTc-NC100668, an agent for imaging venous thromboembolism : The effect of anticoagulant or thrombolytic therapy on the uptake and retention of radioactivity in blood clots in vivo
  • 2007
  • Ingår i: Nuclear medicine communications. - 0143-3636 .- 1473-5628. ; 28:1, s. 55-62
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: The purpose of this study was to evaluate the uptake of Tc-NC100668 into blood clots and elucidate the potential for medications commonly used to treat thromboembolism to interfere with the uptake and retention of Tc-NC100668. METHODS: Tc-NC100668 in vivo uptake and retention in a range of blood clot of various ages (up to 4 h old) and in the presence of anticoagulants or thrombolytic therapies was measured in a rat model of deep vein thrombosis. RESULTS: Tc-NC100668 was rapidly absorbed into and retained by blood clots and was not significantly affected by the presence of unfractionated or low molecular weight heparin or thrombin inhibitor. Tissue plasminogen activator reduced the uptake of Tc-NC100668 into blood clot by a factor of 3 when adjusted to allow for changes in the weight of the blood clot. CONCLUSIONS: This study has demonstrated that the uptake and retention of Tc-NC100668 into blood clots in the rat model of deep vein thrombosis is rapid and maintained over at least a 4 h post-injection period. It has been shown that Tc-NC100668 is retained in blood clots even in the presence of therapeutic doses of those anticoagulant and thrombolytic therapies typically used to treat pulmonary embolism and venous thrombosis.
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