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- Bajc, Marika, et al.
(författare)
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Lung ventilation/perfusion SPECT in the artificially embolized pig.
- 2002
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 43:5, s. 640-647
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Tidskriftsartikel (refereegranskat)abstract
- Planar lung scintigraphy is a standard method used for the diagnosis of lung embolism, but it is hampered by the high incidence of nondiagnostic tests. Ventilation/perfusion SPECT may possibly improve this situation. The objective of this study was to compare planar lung scintigraphy with ventilation/perfusion SPECT using pigs with artificially engendered lung emboli labeled with (201)Tl. METHODS: Sixteen anesthetized pigs were each injected with zero to 4 latex emboli. Cylindric emboli were used in the first 7 pigs and flat 3-tailed emboli were used in the remaining 9 pigs. The pigs spontaneously inhaled 30 MBq (99m)Tc-diethylenetriaminepentaacetic acid aerosol for ventilation scintigraphy. Planar scintigraphy and SPECT were performed using a double-head gamma camera in (99m)Tc and (201)Tl windows. Immediately thereafter, 100 MBq (99m)Tc-labeled macroaggregated albumin were injected intravenously followed by SPECT and, finally, planar scintigraphy. The ventilation background was subtracted from the perfusion tomograms for calculation of a normalized ventilation/perfusion (V/P) quotient image set. RESULTS: The cylindric emboli caused artifacts in the ventilation images; therefore, these were excluded from the final analysis. However, for the planar perfusion images of these pigs, sensitivity and specificity were 71% and 91%, respectively, whereas SPECT yielded 100% for both. For the 3-tailed emboli and ventilation/perfusion images, the sensitivity and specificity were 64% and 79%, respectively, for the planar modality, whereas SPECT yielded values of 91% and 87%, respectively. CONCLUSION: V/P SPECT may improve the diagnostic power of lung scintigraphy.
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| 4. |
- Jönsson, Lena M, et al.
(författare)
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A dosimetry model for the small intestine incorporating intestinal wall activity and cross-doses.
- 2002
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 43:12, s. 1657-1664
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Tidskriftsartikel (refereegranskat)abstract
- Current internal radiation dosimetry models for the small intestine, and for most walled organs, lack the ability to account for the activity uptake in the intestinal wall. In existing models the cross-dose from nearby loops of the small intestine is not taken into consideration. The aim of this investigation was to develop a general model for calculating the absorbed dose to the radiation-sensitive cells in the small intestinal mucosa from radionuclides located in the small intestinal wall or contents. Methods: A model was developed for calculation of the self-dose and cross-dose from activity in the intestinal wall or contents. The small intestine was modeled as a cylinder with 2 different wall thicknesses and with an infinite length. Calculations were performed for various mucus thicknesses. S values were calculated using the EGS4 Monte Carlo simulation package with the PRESTA algorithm and the simulation results were integrated over the depth of the radiosensitive cells. The cross-organ dose was calculated by summing the dose contributions from other intestinal segments. Calculations of S values for self-dose and cross-dose were made for monoenergetic electrons, 0.050–10 MeV, and for the radionuclides 99mTc, 111In, 131I, 67Ga, 90Y, and 211At. Results: The self-dose S value from activity located in the small intestinal wall is considerably greater than the S values for self-dose from the contents and the cross-dose from wall and contents except for high electron energies. For all radionuclides investigated and for electrons 0.10–0.20 MeV and 8–10 MeV in energy, the cross-dose from activity in the contents is higher than the self-dose from the contents. The mucus thickness affects the S value when the activity is located in the contents. Conclusion: A dosimetric model for the small intestine was developed that takes into consideration the localization of the radiopharmaceutical in the intestinal wall or in the contents. It also calculates the contribution from self-dose and cross-dose. With this model, more accurate calculations of absorbed dose to radiation-sensitive cells in the intestine are possible.
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| 6. |
- Ljungberg, Michael, et al.
(författare)
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A 3-dimensional absorbed dose calculation method based on quantitative SPECT for radionuclide therapy: evaluation for (131)I using monte carlo simulation.
- 2002
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 43:8, s. 1101-1109
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Tidskriftsartikel (refereegranskat)abstract
- A general method is presented for patient-specific 3-dimensional absorbed dose calculations based on quantitative SPECT activity measurements. METHODS: The computational scheme includes a method for registration of the CT image to the SPECT image and position-dependent compensation for attenuation, scatter, and collimator detector response performed as part of an iterative reconstruction method. A method for conversion of the measured activity distribution to a 3-dimensional absorbed dose distribution, based on the EGS4 (electron-gamma shower, version 4) Monte Carlo code, is also included. The accuracy of the activity quantification and the absorbed dose calculation is evaluated on the basis of realistic Monte Carlo-simulated SPECT data, using the SIMIND (simulation of imaging nuclear detectors) program and a voxel-based computer phantom. CT images are obtained from the computer phantom, and realistic patient movements are added relative to the SPECT image. The SPECT-based activity concentration and absorbed dose distributions are compared with the true ones. RESULTS: Correction could be made for object scatter, photon attenuation, and scatter penetration in the collimator. However, inaccuracies were imposed by the limited spatial resolution of the SPECT system, for which the collimator response correction did not fully compensate. CONCLUSION: The presented method includes compensation for most parameters degrading the quantitative image information. The compensation methods are based on physical models and therefore are generally applicable to other radionuclides. The proposed evaluation methodology may be used as a basis for future intercomparison of different methods.
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| 7. |
- Lubberink, Mark, et al.
(författare)
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110mIn-DTPA-D-Phe1-octreotide for imaging of neuroendocrine tumors with PET
- 2002
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 43:10, s. 1391-7
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Tidskriftsartikel (refereegranskat)abstract
- The somatostatin analog diethylenetriaminepentaacetic acid (DTPA)-D-Phe1-octreotide labeled with 111In has been applied extensively for diagnosis of neuroendocrine tumors using SPECT or planar scintigraphy. However, the spatial resolution of planar scintigraphy and SPECT prohibits imaging of small tumors, and the quantification accuracy of both methods is limited. METHODS: We developed a method to prepare the positron-emitting radiopharmaceutical 110mIn-DTPA-D-Phe1-octreotide based on a commercially available kit. Phantom studies were done to investigate and compare the performance of 110mIn PET and 111In SPECT. A clinical imaging study using 110mIn-DTPA-D-Phe1-octreotide and PET was done to investigate the application of this radiopharmaceutical. RESULTS: An almost 3-fold better resolution and much better quantitative capabilities were found for 110mIn PET than for 111In SPECT. The clinical imaging study demonstrated the potential use of 110mIn-octreotide in PET to image tumors and quantify radioactivity uptake in humans using (110m)In-DTPA-D-Phe1-octreotide. CONCLUSION: PET with 110mIn-DTPA-D-Phe1-octreotide greatly improved detection of small tumors and offers a possibility of more accurate quantification of tumor uptake than can be obtained with 111In-DTPA-D-Phe1-octreotide and SPECT.
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| 10. |
- Postgård, Per, et al.
(författare)
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Stunning of iodide transport by (131)I irradiation in cultured thyroid epithelial cells.
- 2002
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Ingår i: Journal of nuclear medicine : official publication, Society of Nuclear Medicine. - 0161-5505. ; 43:6, s. 828-34
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Tidskriftsartikel (refereegranskat)abstract
- The existence of thyroid stunning (i.e., inhibited thyroidal iodide uptake after administration of diagnostic amounts of (131)I) is controversial and is currently a subject of debate. To our knowledge, the stunning phenomenon has not been investigated previously in vitro. METHODS: Growth-arrested porcine thyroid cells that formed a tight and polarized monolayer in a bicameral chamber were irradiated with 3-80 Gy (131)I present in the surrounding culture medium for 48 h. The iodide transport capacity after irradiation was evaluated 3 d later by measuring the transepithelial (basal to apical) flux of trace amounts of (125)I. RESULTS: The basal-to-apical (125)I transport decreased with increasing absorbed dose acquired from (131)I; a nearly 50% reduction was observed already at 3 Gy. Stable iodide at the same molarity as (131)I (10(-8) mol/L) had no effect on the (125)I transport. Cell number and epithelial integrity were not affected by irradiation. CONCLUSION: Stunning of iodide transport is detected after (131)I irradiation of cultured thyroid cells. The degree of inhibition of transport is dependent on the absorbed dose.
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