| 1. |
- Almquist, H, et al.
(författare)
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Performance of simultaneous emission-transmission systems for attenuation-corrected SPEct: a method for validation applied to two camera systems
- 2001
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Ingår i: Nuclear Medicine Communications. - 1473-5628. ; 22:7, s. 759-766
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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.
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| 2. |
- Gustafsson, Agnetha, et al.
(författare)
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Evaluation of various attenuation corrections in lung SPECT in healthy subjects
- 2003
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Ingår i: Nuclear Medicine Communications. - : Ovid Technologies (Wolters Kluwer Health). - 0143-3636 .- 1473-5628. ; 24:10, s. 1087-1095
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Tidskriftsartikel (refereegranskat)abstract
- The effect of increasingly more sophisticated attenuation correction methods on image homogeneity has been studied in seven healthy subjects. The subjects underwent computed tomography (CT), single photon emission computed tomography (SPECT) and transmission computed tomography (TCT) of the thorax region in the supine position. Density maps were obtained from the CT and TCT studies. Attenuation corrections were performed using five different methods: (1) uniform correction using only the body contour; (2) TCT based corrections using the average lung density; (3) TCT based corrections using the pixel density; (4) CT based corrections using average lung density; and (5) CT based corrections using the pixel density. The isolated attenuation effects were assessed on quotient images generated by the division of images obtained using various attenuation correction methods divided by the non-uniform attenuation correction based on CT pixel density (reference method). The homogeneity was calculated as the coefficient of variation of the quotient images (CVatt), showing the isolated attenuation effects. Values of CVatt were on average 12.8% without attenuation correction, 10.7% with the uniform correction, 8.1% using TCT map using the average lung density value and 4.8% using CT and average lung density corrections. There are considerable inhomogeneities in lung SPECT slices due to the attenuation effect. After attenuation correction the remaining inhomogeneity is considerable and cannot be explained by statistical noise and camera non-uniformity alone. ((C) 2003 Lippincott Williams Wilkins).
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| 3. |
- Källén, Kristina, et al.
(författare)
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Quantitative 201Tl SPET imaging in the follow-up of treatment for brain tumour: a sensitive tool for the early identification of response to chemotherapy?
- 2000
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Ingår i: Nuclear Medicine Communications. - 1473-5628. ; 21:3, s. 259-267
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to establish if repeated quantitative 201Tl SPET scanning during follow-up of astrocytoma therapy can provide information that is relevant for clinical management. Sixteen consecutive patients, with histopathologically verified highly malignant astrocytoma, were followed during PCV chemotherapy. Imaging with 201Tl SPET and CT was performed repeatedly over 8-16 weeks until treatment discontinuation, with a maximum follow-up of 74 weeks. Tumour uptake volume (TUV), a measure of metabolically active tumour tissue, was calculated from the SPET images. The reliability of early identification of treatment failure, defined as > 25% tumour volume increase, following one course (week 8) and three courses (week 24) of chemotherapy, was calculated for the two imaging methods. 201Tl SPET positive patients (> 25% tumour volume increase) were compared with 201Tl SPET negative patients in terms of time to treatment discontinuation (TTD) and survival time (ST). The patients were followed with a total of 59 SPET examinations, and treatment was continued for a median 27 weeks (range 16-78 weeks). The comparative reliability of SPET and CT showed the highest sensitivity and accuracy for SPET in the early identification of astrocytoma treatment failure at the week 24 assessment. Patients with positive 201Tl SPET after three courses of chemotherapy had a significantly reduced TTD (P = 0.040) but not significantly reduced ST. Of the ten patients who received concomitant radiation and chemotherapy, five had a small (0-10 ml) TUV at the week 24 assessment. Patients with a TUV > 10 ml at this assessment had a shorter TTD (P = 0.016) and a reduced ST (P = 0.024) compared to patients with a TUV < 10 ml. In conclusion, the assessment of progressive disease by quantitative 201Tl SPET appears to provide information on treatment response, earlier and with a higher reliability than CT. Repeated 201Tl SPET scanning during follow-up of astrocytoma treatment is an alternative tool for the early identification of treatment failure.
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| 4. |
- Larsson, Anne, et al.
(författare)
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A method for attenuation and scatter correction of brain SPECT based on computed tomography images
- 2003
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Ingår i: Nuclear medicine communications. - 0143-3636 .- 1473-5628. ; 24:4, s. 411-420
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Tidskriftsartikel (refereegranskat)abstract
- A method for attenuation and scatter correction of brain single photon emission computed tomography (SPECT) is described where computed tomography (CT) images of the brain are used for the calculation of attenuation maps. The method is evaluated for the substance 99mTc hexamethylpropylene amine oxime. A transmission dependent scatter correction is utilized and is based on ray sums calculated through the attenuation map. A method based on external markers is used to align the SPECT and CT image volumes. The markers need only to be present during the SPECT acquisition since the corresponding landmarks can be found without markers on the CT images. The mismatching has been investigated for five patients who have undergone both a CT examination and a SPECT examination with markers. Twelve individuals from the staff have pointed out the landmarks on the CT images, with an average standard deviation of 3.4 mm. Reconstructions with an attenuation map shifted the corresponding 95% confidence interval have been performed to obtain an estimation of the quantitative uncertainty caused by the mismatching, and quantitative errors of up to 6.3% have been measured. At present the method is probably most useful when groups of patients are studied.
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| 5. |
- Persson, Eva, et al.
(författare)
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Quantification of myocardial hypoperfusion with 99m Tc-sestamibi in patients undergoing prolonged coronary artery balloon occlusion.
- 2002
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Ingår i: Nuclear Medicine Communications. - 1473-5628. ; 23:3, s. 219-228
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Tidskriftsartikel (refereegranskat)abstract
- SUMMARY: Percutaneous transluminal coronary angioplasty provides an excellent opportunity to investigate the location and quantity of hypoperfusion during sudden complete occlusion of one of the major coronary arteries. Thirty-five patients referred for elective percutaneous transluminal coronary angioplasty were injected intravenously with 99mTc-sestamibi during balloon inflation. To visualize and quantify the hypoperfused region, a map of perfusion was constructed from that occlusion study and from the control study performed on the following day. Patients were divided into groups according to proximal or distal occlusion within each of the three coronary arteries. The region of myocardium supplied by each coronary artery varied in location and extended outside the typical borders for all arteries, but most prominently for the left circumflex coronary artery. The quantities of hypoperfusion varied within each artery group, but the average hypoperfusion was greater for the left anterior descending coronary artery than for either the right coronary artery or the left circumflex coronary artery. It is concluded that the quantities of hypoperfusion were highly variable within each artery group. Occlusion of the left anterior descending coronary artery was associated with the largest ischaemic region. The area of hypoperfusion extended outside the typical borders, most prominently for the left circumflex coronary artery.
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| 6. |
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| 7. |
- Sjöström, A, et al.
(författare)
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Direct astatination of a peptide, human epidermal growth factor, using nido-carborane as a prosthetic group
- 2000
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Ingår i: Nuclear medicine communications. - 0143-3636 .- 1473-5628. ; 21:6, s. 594-
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Recension (övrigt vetenskapligt/konstnärligt)abstract
- Purpose The aim of the study was to evaluate direct astatine labelling of proteins with the use of nido-carborane as prosthetic group for attachments of astatine. Methods: Human epidermal growth factor, hEGF, was conjugated to 7-(3-amino-propyl)-7,8-dicarbanido-undecaborate (-), ANC, using two different conjugation methods, glutaraldehyde crosslinking and coupling via Traut's reagent. The hEGF-ANC conjugates were astatine labelled using the Chloramine-T method. The stability of the labelled compounds was tested by incubation at 37°C. Results: The conjugates were astatinated using the Chloramine-T method in high yield. The best labelling yields were obtained by the glutaraldehyde conjugate with an average yield of 70.5±2.2%. In vitro stability tests indicated that the introduced label was as stable as hEGF labelled with astatobenzoate. Conclusion: Conjugation of nido-carboranes to peptides creates binding sites for direct astatine labelling that can be performed in mild conditions (p 7.2) with high labelling yields.
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| 8. |
- Starck, Sven-Åke, et al.
(författare)
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An evaluation of reconstruction techniques and scatter correction in bone SPECT of the spine
- 2003
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Ingår i: Nuclear medicine communications. - 0143-3636 .- 1473-5628. ; 24:5, s. 565-570
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Tidskriftsartikel (refereegranskat)abstract
- A selection of commonly used reconstruction and filter techniques in the processing of 99mTc oxidronate (i.e., 99mTc hydroxymethane diphosphonate) single photon emission computed tomography (SPECT) of the spine was compared. The possible additional value of scatter correction on image contrast was also evaluated. Twenty-eight bone SPECT examinations of consecutive patients were studied retrospectively. The reconstruction techniques used were filtered back-projection and iterative reconstruction with the use of ordered subsets estimation maximization. Three-dimensional post-filtering with a Metz filter and a Butterworth filter was used. Each combination was evaluated with or without scatter correction. Each study was also processed with the department's standard technique of two-dimensional pre-filtering with a Metz filter followed by filtered back-projection (without scatter correction). Five observers evaluated the image quality of reconstructed coronal and sagittal slices, with special reference to the resolution of vertebrae, vertebral processes, the spinal canal and suspected abnormal uptakes. A grading scale from -2 to +2 was used with the standard technique as the reference. The best image quality was found with iterative reconstruction in combination with a contrast enhancing Metz filter or a noise reducing Butterworth filter. Scatter correction did not improve image quality.
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| 9. |
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