| 1. |
- Nettelbladt, Otto S, et al.
(författare)
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Combined fluorine-18-FDG and carbon-11-methionine PET for diagnosis of tumors in lung and mediastinum
- 1998
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 39:4, s. 640-647
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Tidskriftsartikel (refereegranskat)abstract
- We evaluated the value of PET using 18F-fluorodeoxyglucose (FDG) and 11C-methionine, individually or in combination, to distinguish malignant from benign tumors and to identify or exclude mediastinal metastases.METHODS:Seventeen patients with a tumor in the lung or mediastinum were evaluated with 18F-FDG and 11C-methionine PET. For morphological comparison, we used CT, and all findings were confirmed by histology of surgical resection specimens (n = 16) or by cytology (n = 1).RESULTS:All tumors were visualized equally well with both tracers, and there were no false-positive results. In 2 patients with a malignant tumor, coexisting pneumonia was correctly diagnosed as an inflammatory lesion because of its wedge-like shape. PET correctly excluded hilar invasion and mediastinal lymph node metastases in 10 of 14 patients with primary lung tumor. PET identified mediastinal metastases in 4 of 4 patients. CT failed to detect mediastinal tumor spread in 2 patients and gave a false-positive reading in 2 others. Significantly higher uptake (SUV) and transport rate (slope) values were obtained from malignant than benign lesions with both tracers. No major differences were seen in either the levels of significance or accuracy when the two tracers were compared. Slope values did not add further information to what was obtained with SUV. Density correction of SUV and slope values, to avoid the influence of surrounding air as well as tumor heterogeneity, increased these differences somewhat. Both tracers distinguished malignant from benign lesions with a 93% sensitivity and an accuracy of 89%-95%, but sensitivity improved to 100% when values from both tracers were combined.CONCLUSION:Fluorine-18-FDG and 11C-methionine PET visualized all tumors equally well and detected mediastinal spread better than CT. For differentiation purposes, the problems of false-positive and false-negative PET findings could not be safely overcome in a limited number of cases either by the use of both tracers, by the additional use of slope values or by lesion density correction.
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| 2. |
- Andersson, Jesper L, et al.
(författare)
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A method for coregistration of PET and MR brain images
- 1995
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 36:7, s. 1307-1315
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Tidskriftsartikel (refereegranskat)abstract
- Combining MRI morphological data with functional PET data offers significant advantages in research as well as in many clinical situations. Automatic methods are needed, however, to coregister the data from the two modalities.METHODS:Simulated PET images were created by simple and automatic segmentation of MR images followed by the assignment of different uptake values to various tissue types. The simulated PET images were registered to actual PET images using a pixel-by-pixel, PET-PET registration method. The transformation matrix was then applied to the MR images. The method was used to register MRI data to PET transmission scans and emission scans obtained with FDG, nomifensine and raclopride. Validation was performed by comparing the results to those obtained by matching internal points manually defined in both volumes.RESULTS:Emission and transmission PET images were successfully registered to MR data. Comparison to the manual method indicated a registration accuracy on the order of 1-2 mm in each direction. No difference in accuracy between the different tracers was found. The error sensitivity for the method's assumptions seemed to be sufficiently low to allow complete automation of the method.CONCLUSION:We present a rapid, robust and fully automated method to register PET and MR brain images with sufficient accuracy for most clinical applications.
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| 3. |
- Antoni, Gunnar, et al.
(författare)
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Synthesis of l-2,4-Diamino[4-11C]butyric acid and its use in some In vitro and In vivo tumour models
- 1997
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Ingår i: Nuclear Medicine and Biology. - 0969-8051 .- 1872-9614. ; 24:6, s. 595-601
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Tidskriftsartikel (refereegranskat)abstract
- l-2,4-Diamino[4-11C]butyric acid (DAB) was synthesized by an enzyme catalysed carrier added (0.1 μmol KCN) reaction of hydrogen [11C]cyanide with O-acetyl-l-serine followed by reduction. l-[11C]DAB was obtained with a radiochemical purity higher than 96% and with a decay corrected radiochemical yield of 30–40% within a 32 min reaction time. The enantiomeric excess was 98%. The uptake of l-[11C]DAB was investigated in multicellular aggregates of six different cell lines and animal tumour models. l-[11C]DAB is potentially useful for the assessment of pharmacokinetics of l-DAB in vivo for part of its evaluation as an antitumoural agent, although its use for diagnostic purposes seems limited.
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| 4. |
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| 5. |
- Bergström, Mats, et al.
(författare)
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PET with [11C]-Metomidate for the Visualization of Adrenocortical Tumors and Discrimination from Other Lesions
- 1999
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Ingår i: Clinical Positron Imaging. - 1095-0397 .- 1878-5751. ; 2:6, s. 339-
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Tidskriftsartikel (refereegranskat)abstract
- Purpose:The purpose of the study was to evaluate the potential role of PET with the adrenocortical-specific tracer 11C-metomidate in the characterization of incidentally found adrenal cortical lesions and in adrenocortical carcinomas.Methods:PET with 11C-metomidate was performed in 15 patients with unilateral adrenal mass confirmed by CT (incidentalomas) and in 9 additional patients with adrenocortical cancer. All incidentalomas subsequently underwent surgery, except 2 subjected to biopsy only. These lesions were histopathologically examined and diagnosed as adrenal cortical adenoma (n = 6; 3 nonfunctioning), adrenocortical carcinoma (n = 2) and nodular hyperplasia (n = 1). The remaining were non-cortical lesions including 1 pheochromocytoma, 1 myelolipoma, 2 adrenal cysts, and 2 metastases.Results:All lesions, except 1, with an adrenocortical origin were easily identified due to exceedingly high uptake of 11C-metomidate, whereas the non-cortical lesions showed very low uptake. The 1 false negative was a cancer that at surgery was found to be extensively necrotic. High uptake was also seen in normal adrenal glands. The tracer uptake kinetics indicated trapping of the tracer in the cortical lesions. For quantitative evaluation of tracer binding in individual lesions, the simple SUV concept was found to be equally accurate as more elaborate kinetic analyses.Conclusion:The patients presented and altogether over 40 PET investigations have demonstrated 11C-metomidate to be an attractive tracer for the characterization of adrenal masses with the ability to discriminate lesions of adrenal cortical origin from non-cortical lesions. Additionally the method allows the assessment of metastases from adrenocortical cancers, and the very high contrast has allowed partial whole-body examinations.
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| 6. |
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| 7. |
- Bäck, Sven, et al.
(författare)
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Improvements in absorbed dose measurements for external radiation therapy using ferrous dosimeter gel and MR imaging (FeMRI)
- 1998
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 43, s. 261-
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Tidskriftsartikel (refereegranskat)abstract
- A ferrous gel, based on ferrous (Fe) sulphate and agarose, was used with a clinical magnetic resonance imaging (MRI) scanner to obtain relative dose distribution data from therapeutic photon and electron beams. The FeMRI gel was scanned using a new MRI acquisition protocol optimized for T1 measurements. Thorough comparisons with silicon semiconductor detector and ionization chamber measurements, as well as with Monte Carlo calculations, were performed in order to quantify the improvements obtained using FeMRI for dose estimations. Most of the relative doses measured with FeMRI were within 2% of the doses measured with other methods. The larger discrepancies (2-4%) found at shallow depths are discussed. The uncertainty in relative dose measurements using FeMRI was significantly improved compared with previously reported results (5-10%, one standard deviation, 1 SD), and is today between 1.6% and 3.3% (depending on dose level, 2 SD). This corresponds to an improvement in the minimum detectable dose (3 SD above background) from approximately 2 Gy to better than 0.6 Gy. The results obtained in this study emphasize the importance of obtaining basic FeMRI dose data before the method is extended to complicated treatment regimes.
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| 8. |
- Carlsson, Jörgen, et al.
(författare)
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Conjugate chemistry and cellular processing of EGF-dextran
- 1999
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 38:3, s. 313-321
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Tidskriftsartikel (refereegranskat)abstract
- Conjugates with specific binding to the epidermal growth factor receptor, EGFR, of interest for radionuclide based imaging and therapy were prepared using mouse epidermal growth factor, mEGF, and dextran. In one type of conjugate, mEGF was coupled to dextran by reductive amination in which the free amino group on the mEGF N-terminal reacted with the aldehyde group on the reductive end of dextran. The end-end coupled conjugate could be further activated by the cyanopyridinium agent CDAP, thereby introducing tyrosines to the dextran part. In the other type of conjugate, the cyanylating procedure using CDAP was applied, first to activate dextran and then allowing for the amino terminus of mEGF to randomly attach to the dextran. In the latter case, radionuclide-labelled tyrosines or glycines could be added in the same conjugation step. All types of mEGF-dextran conjugates had EGFR-specific binding since the binding could be displaced by an excess of non-radioactive mEGF. The conjugates were to a large extent internalized in the test cells and the associated radioactivity was retained intracellularly for different times depending on both the type of cells and conjugate applied. Different intracellular 'traffic routes' for the radionuclides are discussed as well as applications for both imaging and therapy.
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| 9. |
- Edin, Anders
(författare)
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Interplay between soft and hard processes in quantum chromodynamics
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In QCD, the theory of strong interactions, hard processes with large momentum transfers can be calculated using perturbation theory, while soft processes with small momentum transfers are poorly understood. In this thesis, phenomenological models of soft and hard QCD processes are developed and tested.A new model is presented for the distribution of quarks and gluons in hadrons. They are derived from a spherically symmetric, Gaussian, distribution of the quark and gluon momenta in the hadron rest frame. The proton structure function F2 is calculated from the model and evolved using next-to-leading order QCD, resulting in a successful comparison-with deep inelastic scattering data.A unified description is given of the hadronic final states observed in deep inelastic electron-proton scattering at HERA, regarding both the large forward energy flow and the rapidity gap events with no particles in a large forward angular region. The model is based on perturbative QCD complemented with a new "soft colour interaction" mechanism which affects the hadronic final state, and provides a continuous description of the transition from diffractive to non-diffractive hard scattering.The model for soft colour interactions also describes the surprisingly high production rate of heavy quarkonia observed in proton-antiproton collisions at the Tevatron.
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| 10. |
- Gunther Axelsson, Maria
(författare)
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Production asymmetry of strange quarks in electron-positron annihilation at LEP
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The forward-backward asymmetry in the production of strange quarks in electron-positron annihilation has been measured at a centre-of-mass energy corresponding to the mass of the Z0 particle. The asymmetry at this energy is highly sensitive to the ratio between the vector and axial-vector couplings of the quark to the Z0 and to the value of the electroweak mixing angle sin2 θw. Together with the previously measured value of the forward-backward asymmetry of the bottom quark, the measurement provides a test of the important theoretical prediction that the couplings to the Z0 are universal for all down-type quarks.The analysis is based on 1.4 million hadronic Z0 decays recorded in 1994 with the DELPHI detector system at the LEP collider at CERN. The strange quarks are selected using high-momentum charged kaons identified by the Ring Imaging CHerenkov (RICH) detectors. The charged kaon momentum is used to evaluate the probability for an event to belong to one of six possible event classes. Five classes are determined by the flavour of the primary quark (up, down, charm, strange and bottom) and the sixth class contains misidentified particles. The forward-backward asymmetry is determined using a maximum-likelihood method. At the Z0 pole, the asymmetry is found to beAFB0, s = 0.105 ± 0,016(stat.) ± 0.0006(syst.)which is the most precise measurement available for the strange quark asymmetry. The result is consistent with the previously measured value of the asymmetry of, the bottom quark, and thus with the predicted universality of the down-type quark couplings to the Z0. The obtained asymmetry corresponds to an electroweak mixing angle sin2 θw = 0.2229 ± 0.0030.
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