| 1. |
- 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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| 2. |
- Ekberg, Tomas, et al.
(författare)
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Clinical impact of positron emission tomography (PET) with (18F)fluorodeoxyglucose (FDG) in head and neck tumours
- 2007
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Ingår i: Acta Oto-Laryngologica. - : Informa UK Limited. - 0001-6489 .- 1651-2251. ; 127:2, s. 186-193
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Tidskriftsartikel (refereegranskat)abstract
- Conclusion. PET plays an important role in staging, on suspicion of recurrence and for detection of occult primary tumours in the head and neck. Objective: Since 1998 we have used positron emission tomography (PET) with (F-18)fluorodeoxyglucose (FDG) to assess selected patients. This procedure has often helped in making decisions on staging and treatment. Patients and methods. The case records of the first 80 patients (104 PET examinations) were studied retrospectively. Results. A total of 39 examinations were performed for staging. PET detected all primary tumours except two (stage T1), and staging was adjusted after 13%. In all, 33 PET examinations were performed on suspicion of recurrent tumour. In 52% of these PET determined further treatments; in 21% PET had a direct impact on the surgical planning. In 18 patients with metastases from an occult primary tumour, PET detected 39% of those tumours; in 22% it was the sole modality to do so. No recurrences or second primary tumours were detected when PET was used for follow-up of clinically cured patients. Results were similar when squamous cell carcinomas (SCCs) were considered alone as compared to the complete material. The mean standardized uptake value (SUV) was higher for cases deemed tumour-positive than in negative cases.
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| 3. |
- Eriksson, Olof, et al.
(författare)
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Quantitative Imaging of Serotonergic Biosynthesis and Degradation in the Endocrine Pancreas
- 2014
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 55:3, s. 460-465
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Tidskriftsartikel (refereegranskat)abstract
- Serotonergic biosynthesis in the endocrine pancreas, of which the islets of Langerhans is the major constituent, has been implicated in insulin release and β cell proliferation. In this study, we investigated the feasibility of quantitative noninvasive imaging of the serotonergic metabolism in the pancreas using the PET tracer (11)C-5-hydroxy-l-tryptophan ((11)C-5-HTP).METHODS: Uptake of (11)C-5-HTP, and its specificity for key enzymes in the serotonergic metabolic pathway, was assessed in vitro (INS-1 and PANC1 cells and human islet and exocrine preparations) and in vivo (nonhuman primates and healthy and diabetic rats).RESULTS: In vitro tracer uptake in endocrine cells (INS-1 and human islets), but not PANC1 and exocrine cells, was mediated specifically by intracellular conversion into serotonin. Pancreatic uptake of (11)C-5-HTP in nonhuman primates was markedly decreased by inhibition of the enzyme dopa decarboxylase, which converts (11)C-5-HTP to (11)C-serotonin and increased after inhibition of monoamine oxidase-A, the main enzyme responsible for serotonin degradation. Uptake in the rat pancreas was similarly modulated by inhibition of monoamine oxidase-A and was reduced in animals with induced diabetes.CONCLUSION: The PET tracer (11)C-5-HTP can be used for quantitative imaging of the serotonergic system in the endocrine pancreas.
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| 4. |
- Eriksson, Olof, et al.
(författare)
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The Positron Emission Tomography ligand [11C]5-Hydroxy-Tryptophan can be used as a surrogate marker for the human endocrine pancreas
- 2014
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 63:10, s. 3428-3437
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Tidskriftsartikel (refereegranskat)abstract
- In humans a well-developed serotonin system is localized to the pancreatic islets while being absent in exocrine pancreas. Assessment of pancreatic serotonin biosynthesis could therefore be used to estimate the human endocrine pancreas. Proof of concept was tested in a prospective clinical trial by comparisons of type 1 diabetic (T1D) patients, with extensive reduction of beta cells, with healthy volunteers (HV).C-peptide negative (i.e. insulin-deficient) T1D subjects (n=10) and HV (n=9) underwent dynamic Positron Emission Tomography with the radiolabeled serotonin precursor [(11)C]5-Hydroxy-Tryptophan ([(11)C]5-HTP).A significant accumulation of [(11)C]5-HTP was obtained in the pancreas of the HV, with large inter-individual variation. A substantial and highly significant reduction (66%) in the pancreatic uptake of [(11)C]5-HTP in T1D subjects was observed, and this was most evident in the corpus and caudal regions of the pancreas where beta-cells normally are the major constituent of the islets.[(11)C]5-HTP retention in the pancreas was reduced in T1D compared to non-diabetic subjects. Accumulation of [(11)C]5-HTP in the pancreas of both HV and subjects with T1D were in agreement with previously reported morphological observations on the beta cell volume implying that [(11)C]5-HTP retention is a useful non-invasive surrogate marker for the human endocrine pancreas.
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| 5. |
- Garske-Román, Ulrike, 1963-
(författare)
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177Lu-DOTA-octreotate Radionuclide Therapy of Neuroendocrine Tumours : Dosimetry-Based Therapy Planning and Outcome
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Peptide receptor radionuclide therapy for the internal radiation of neuroendocrine tumours expressing somatostatin receptors has made great advances and offers promising results. 177Lu-DOTA-octreotate is one of the most widely used radiopeptides, but kidneys and bone marrow are organs at risk. Methods of measuring radiation doses to at-risk organs and tumours (dosimetry) on an individual patient basis have been regarded as impracticable and a maximum of 4 treatment cycles has widely been accepted as the treatment standard instead.The first aim of this thesis was to establish a clinically feasible protocol to calculate absorbed doses to bone marrow and the kidneys during therapy with 177Lu-DOTA-octreotate. A new dosimetry protocol for the bone marrow was described. Dosimetry for solid organs had previously been described based on 3-dimensional imaging by the research group. In the current thesis it was demonstrated that in most patients only minor changes of the effective half-life occurred in the kidneys. By performing complete dosimetry during the first cycle and comparing it with the uptake in later cycles, it was shown that the absorbed dose can be cal-culated based on the activity concentration at 24 hours after therapy. The study concluded that 50% of all patients could receive more than the standard 4 treatment cycles with 7.4 GBq 177Lu-DOTA-octreotate without passing the limit of 23 Gray to the kidneys or 2 Gray to the bone marrow, whereas 20% would tolerate fewer than 4 cycles. The second aim was to describe treatment outcomes of dosimetry-guided therapy with 177Lu-DOTA-octreotate. Patients with metastasized colorectal neuroendocrine tumours and bronchial carcinoids were shown to have longer survival with this method than previously reported. Morphological tumour response could be correlated to time to progression. Furthermore, in a case of low-differentiated neuroendocrine cancer it was shown that large tumours with high proliferation can also be treated with this method and that tumour-to-risk organ ratios can improve in later cycles, resulting in a more effective treatment.Dosimetry-guided, fractionated radionuclide therapy with 177Lu-DOTA-octreotate is a valuable treatment option for patients with advanced neuroendocrine tumours expressing somatostatin receptors.
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| 6. |
- Lindström, Elin, et al.
(författare)
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Evaluation of block-sequential regularized expectation maximization reconstruction of 68Ga-DOTATOC, 18F-fluoride, and 11C-acetate whole-body examinations acquired on a digital time-of-flight PET/CT scanner
- 2020
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Ingår i: EJNMMI Physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Block-sequential regularized expectation maximization (BSREM) is a fully convergent iterative image reconstruction algorithm. We hypothesize that tracers with different distribution patterns will result in different optimal settings for the BSREM algorithm. The aim of this study was to evaluate the image quality with variations in the applied β-value and acquisition time for three positron emission tomography (PET) tracers. NEMA image quality phantom measurements and clinical whole-body digital time-of-flight (TOF) PET/computed tomography (CT) examinations with 68Ga-DOTATOC (n = 13), 18F-fluoride (n = 10), and 11C-acetate (n = 13) were included. Each scan was reconstructed using BSREM with β-values of 133, 267, 400, and 533, and ordered subsets expectation maximization (OSEM; 3 iterations, 16 subsets, and 5-mm Gaussian post-processing filter). Both reconstruction methods included TOF and point spread function (PSF) recovery. Quantitative measures of noise, signal-to-noise ratio (SNR), and signal-to-background ratio (SBR) were analysed for various acquisition times per bed position (bp).RESULTS: The highest β-value resulted in the lowest level of noise, which in turn resulted in the highest SNR and lowest SBR. Noise levels equal to or lower than those of OSEM were found with β-values equal to or higher than 400, 533, and 267 for 68Ga-DOTATOC, 18F-fluoride, and 11C-acetate, respectively. The specified β-ranges resulted in increased SNR at a minimum of 25% (P < 0.0001) and SBR at a maximum of 23% (P < 0.0001) as compared to OSEM. At a reduced acquisition time by 25% for 68Ga-DOTATOC and 18F-fluoride, and 67% for 11C-acetate, BSREM with β-values equal to or higher than 533 resulted in noise equal to or lower than that of OSEM at full acquisition duration (2 min/bp for 68Ga-DOTATOC and 18F-fluoride, 3 min/bp for 11C-acetate). The reduced acquisition time with β 533 resulted in increased SNR (16-26%, P < 0.003) and SBR (6-18%, P < 0.0001 (P = 0.07 for 11C-acetate)) compared to the full acquisition OSEM.CONCLUSIONS: Within tracer-specific ranges of β-values, BSREM reconstruction resulted in increased SNR and SBR with respect to conventional OSEM reconstruction. Similar SNR, SBR, and noise levels could be attained with BSREM at relatively shorter acquisition times or, alternatively, lower administered dosages, compared to those attained with OSEM.
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| 7. |
- Lindström, Elin, et al.
(författare)
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Evaluation of penalized likelihood estimation reconstruction on a digital time-of-flight PET/CT scanner for 18F-FDG whole-body examinations
- 2018
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 59:7, s. 1152-1158
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Tidskriftsartikel (refereegranskat)abstract
- The resolution and quantitative accuracy of PET are highly influenced by the reconstruction method. Penalized-likelihood estimation algorithms allow for fully convergent iterative reconstruction, generating a higher image contrast than ordered-subsets expectation maximization (OSEM) while limiting noise. In this study, a type of penalized reconstruction known as block-sequential regularized expectation maximization (BSREM) was compared with time-of-flight OSEM (TOF OSEM). Various strengths of noise penalization factor β were tested along with various acquisition durations and transaxial fields of view (FOVs) with the aim of evaluating the performance and clinical use of BSREM for 18F-FDG PET/CT, both quantitatively and in a qualitative visual evaluation. Methods: Eleven clinical whole-body 18F-FDG PET/CT examinations acquired on a digital TOF PET/CT scanner were included. The data were reconstructed using BSREM with point-spread function recovery and β-factors of 133, 267, 400, and 533—and using TOF OSEM with point-spread function—for various acquisition times per bed position and various FOVs. Noise level, signal-to-noise ratio (SNR), signal-to-background ratio (SBR), and SUV were analyzed. A masked evaluation of visual image quality, rating several aspects, was performed by 2 nuclear medicine physicians to complement the analysis. Results: The lowest levels of noise were reached with the highest β-factor, resulting in the highest SNR, which in turn resulted in the lowest SBR. A β-factor of 400 gave noise equivalent to TOF OSEM but produced a significant increase in SUVmax (11%), SNR (22%), and SBR (12%). BSREM with a β-factor of 533 at a decreased acquisition duration (2 min/bed position) was comparable to TOF OSEM at a full acquisition duration (3 min/bed position). Reconstructed FOV had an impact on BSREM outcome measures; SNR increased and SBR decreased when FOV was shifted from 70 to 50 cm. The evaluation of visual image quality resulted in similar scores for reconstructions, although a β-factor of 400 obtained the highest mean whereas a β-factor of 267 was ranked best in overall image quality, contrast, sharpness, and tumor detectability. Conclusion: In comparison with TOF OSEM, penalized BSREM reconstruction resulted in an increased tumor SUVmax and an improved SNR and SBR at a matched level of noise. BSREM allowed for a shorter acquisition than TOF OSEM, with equal image quality.
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| 8. |
- Lindström, Elin
(författare)
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Evaluation of Regularized Image Reconstruction for Clinical Positron Emission Tomography
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Positron emission tomography (PET) combined with computed tomography (CT) is a widely used noninvasive molecular imaging modality with a broad range of clinical applications in oncology, neurology, and cardiology. Producing imperative image quality and accurate quantification are important driving forces behind the technological advances within PET image reconstruction and system development. To ensure clinical quality and to understand how the modern state-of-the-art PET/CT systems and image reconstruction methods compare with older systems and reconstruction methods they need to be evaluated and assessed in a clinical setting. This thesis summarizes six studies assessing the effect of state-of-the-art image reconstruction methods and the introduction of digital PET on image quality and quantitative outcomes of clinical PET scans in oncology, neurology, and cardiology. The overall aim was to evaluate, optimize, and compare quantitative results of regularized image reconstruction with the current standard reconstruction method used in routine clinical practice, ordered subsets expectation maximization (OSEM).The optimal setting of regularized image reconstruction by block-sequential regularized expectation maximization (BSREM) was found to be tracer dependent, and a potential clinical benefit in terms of image quality measures of BSREM over OSEM was found when applied for whole-body 18F-FDG, 68Ga-DOTATOC, 18F-fluorde, 11C-acetate, and 68Ga-PSMA-11 PET imaging. Software-aided assessment of neurodegenerative disease evaluated with 18F-FDG and 18F-flutemetamol was affected by image reconstruction methods and should be used with caution when employing other image reconstruction methods than those used for acquisition of the normal database. In contrast, changes in reconstruction settings were shown to not implicate myocardial blood flow (MBF) based on 15O-water PET analyzed using automated software. This shows that diagnostic MBF cutoff values can be consistently used for 15O-water. Also, large variations in image noise with three different image reconstruction methods did not impact quantitative cerebral blood flow (CBF) in white and gray matter volumes of interest with 15O-water brain PET to any large extent.BSREM image reconstruction shows a great potential clinical benefit providing improved image quality measures with a subsequent possibility of shortening image acquisition durations and/or lowering amount of radioactivity needed for each examination.
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| 9. |
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| 10. |
- Lindström, Elin, et al.
(författare)
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Optimisation of penalized likelihood estimation reconstruction (Q.Clear) on a digital time-of-flight PET-CT scanner for four different PET tracers
- 2017
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Ingår i: Journal of Nuclear Medicine. - 0161-5505 .- 1535-5667. ; 58:S1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Objectives: The penalized likelihood estimation reconstruction algorithm Q.Clear (GE Healthcare) allows for full convergence and edge preservation through a block sequential regularized expectation maximization technique. In this study the performance of Q.Clear was investigated for different penalization factors (β) with the aim to optimize its clinical use for four different tracers.Methods: Q.Clear reconstructions with β values of 200, 400, 600 and 800 were compared to time-of-flight ordered subset expectation maximization (TF-OSEM) (3 iterations, 16 subsets and 5 mm Gaussian filter) with point spread function recovery. Clinical whole-body PET/CT (Discovery MI, GE Healthcare) scans with 68Ga-DOTATOC, 18F-FDG, 11C-acetate or 18F-fluoride were analyzed for level of noise in healthy liver tissue, signal to noise ratio (SNR), signal to background ratio (SBR) and maximum standardized uptake value (SUVmax). In addition, acquisition times per bed position and transaxial field of view (FOV) of the reconstructed images were varied. For each tracer, images from 10 patients were included, with a mean of 30 lesions per tracer. A spherical reference volume of interest (VOI) was placed in the liver and lesions were delineated employing a 41% threshold of the maximum voxel.Results: The lowest levels of noise were reached with the highest beta factor resulting in the highest SNR, but this in turn gave the lowest SBR. Noise equivalence to OSEM was found with β 600 for 68Ga-DOTATOC, 18F-FDG and 18F-fluoride, and β 400 for 11C-acetate with a resulting significant increase of SUVmax (19.4%, 9.7%, 22.5% and 19.0% respectively) (P < 0.0001, paired t-test), SNR (22.1%, 22.6%, 9.5% and 33.6%) and SBR (19.5%, 11.7%, 21.3% and 18.5%) compared to OSEM. SNR decreased while SBR increased for all tracers when extending FOV from 500 to 700 mm, but only significantly for 18F-fluoride. Decreasing image acquisition time gave no statistical difference of SUVmax for 68Ga-DOTATOC, 18F-fluoride (2 to 1.5 min) for any reconstruction method nor for 11C-acetate (3 to 2 min) with β 蠅 400. Decreasing time for 18F-FDG (3 to 2 min) resulted in a change of optimal beta to β 800 in order to reach noise equivalence to OSEM along with maintaining a higher SNR than OSEM.Conclusion: Images reconstructed by Q.Clear result in a tracer-dependent increase in tumour SUVmax values compared to OSEM at matched levels of noise, and an improved SNR. The optimal penalization factor, both in terms of noise-equivalence to OSEM and in terms of absolute SNR, is tracer dependent.
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