| 1. |
- Magnander, Tobias, et al.
(author)
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Comparison of the accuracy in kidney activity concentration estimates by the conjugate view and posterior view methods
- 2015
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In: Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015.
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Conference paper (other academic/artistic)abstract
- Purpose: In nuclear medicine the conjugate view method (CV) is the most common method for activity quantifications in planar images. The advantage with the CV method is its depth independence, i.e. the activity concentrations can be calculated from two opposite planar images without the knowledge of depth. However, one disadvantage of the method that the signal to background ratio is dependent on the location of the object. This effect might increase the inaccuracy in the activity concentration estimates. Therefore, the activity in off-center objects might be better estimated by the camera projection with the shortest camera to object distance. The aim of the present study was to compare the CV method with a posterior-anterior (PA) projection method for estimation of 177Lu activity concentrations in the kidneys. Methods: The two methods were used to retrospectively determine and compare the left and right kidney activity concentration in 20 patients treated with 177Lu-DOTA-octreotate at Sahlgrenska University Hospital. The kidney was segmented in the SPECT or CT image using an appropriate segmentation algorithm. An attenuation map for 177Lu was created from the CT. Attenuated planar AP and PA projections were created from the SPECT and the attenuation map. The kidney VOI was projected onto the AP and PA projections. The activity concentration in the kidney was calculated using both the PA projection method (ACPA) and the CV method (ACCV) and the results were compared to the concentration in the kidney VOI in the SPECT. Results: The mean ratio between ACCV and the SPECT determined activity concentration was 1.99 with a standard deviation (SD) equal to 1.03 and the mean ratio between ACPA and the SPECT determined concentration was 1.66 with SD=0.80. Both methods demonstrated that the main problems with activity estimates from planar images are the influences of attenuation and the activity concentration in the under and overlying tissues. Conclusions: The present study shows that a true background estimate cannot be accurately performed with neither the CV nor the PA method and that the difficulties in obtaining a true background affect the CV method more than the PA method. The study indicates that the PA method gives a more accurate estimate of the kidney activity concentration than the CV method.
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| 2. |
- Hagmarker, Linn, et al.
(author)
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Characterisation of a planar dosimetry method estimating the absorbed dose to the bone marrow during 177Lu-DOTATATE treatment
- 2016
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In: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089.
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Conference paper (other academic/artistic)abstract
- Aim: An image based method for bone marrow dosimetry, earlier presented by our research group, has shown a significant correlation between the absorbed dose to the bone marrow and haematological toxicity in 177Lu-DOTATATE treatment. The aim of this study was to further evaluate and optimise the method. Materials and Methods: 46 patients with advanced neuroendocrine tumours were treated with 177Lu -DOTATATE on 2-6 occasions. The patients were evaluated using the 4 planar gamma camera images collected at 2, 24, 48 and 168 hours after injection. The whole body was divided into a high- and a low uptake compartment, using a threshold based segmentation tool in the image platform PhONSAi, developed in-house. The segmentation tool starts by including the highest uptake focus and then gradually includes foci with lower and lower uptakes until a threshold is reached where the number of foci escalates. The threshold determines the proportion of the foci that is included in the two compartments. Visual inspection was used to determine the threshold valuewhere all high uptake tissues (i.e. kidney, spleen, liver and tumours) were included in the high uptake compartment. For thresholds around this value the activity in the two compartments was determined by the conjugate view method and the bonemarrow dose was calculated as a sum of the self and cross dose in the low uptake compartment and the cross dose from the high uptake compartment. Results: The visual analysis implies a threshold value of 10%of the maximum number of foci. A correlation was found between the absorbed bone marrow dose and haematological toxicity with p-values ranging from 0.001 to 0.02 for thresholds between 2 % and 25 %, the strongest correlation was found at 15 %. The mean absorbed bone marrow dose were 0.20-0.22 Gy per 7.4 GBq for threshold values between 10-25 %, and increased to 0.28 Gy for the lower values. No significant difference was observed in coefficient of variation (8.2-8.7 %) for the individual mean absorbed doses when varying the threshold value. Conclusion: The individual variation in absorbed dose is maintained at a low level when varying the threshold value for the determination of the compartment sizes. This implies that the method is stable for estimation of bone marrow doses and its correlation to haematological toxicity.
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| 3. |
- Hagmarker, Linn, et al.
(author)
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Evaluation of planar versus hybrid SPECT image methodology for bone marrow dosimetry during 177Lu-DOTATATE treatments reveals the obstacles with bone marrow metastases and cross-irradiation for the SPECT activity concentration quantification
- 2018
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In: 31st Annual Congress of the European Association of Nuclear Medicine (EANM’18). 13-17 October, Dusseldorf, Germany.
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Conference paper (other academic/artistic)abstract
- Introduction. The aim of this study is to compare the recently developed planar image-based method for bone marrow dosimetry with a hybrid method using SPECT/CT imaging at 24 h.p.i. of 177Lu-DOTATATE. Predictive ability of the methods is compared by investigating correlations of determined absorbed bone marrow dose, with haematological toxicity during the course of four treatment cycles. The aim is also to investigate the activity distribution in the vertebral column, and how the hybrid methodology can be optimized. Methods and Materials. 45 patients with advanced neuroendocrine tumours treated with 177Lu-DOTATATE at Sahlgrenska University Hospital in 2011-2016 (ILUMINET-study, EUDRACT nr 2011-etc) were included in this study. Absorbed bone marrow doses were calculated as the sum of the cross-doses from high-uptake organs and the remainder of the body, and the self-dose. Cross-doses were determined by time-activity curves created using planar images and a two-compartment method in the image platform PhONSAi. The self-dose was calculated using the time-activity concentration curve for the remainder of the body adjusted with the activity concentration determined in spheres placed in the vertebral bodies in SPECT-images. To improve recovery and reduce cross-irradiation of false counts in the SPECT-image, we utilized the Monte Carlo based reconstruction code SARec. Three activity concentrations were calculated to represent the activity concentration in the bone marrow; one mean (mean SPECT) and one median (median SPECT) activity concentration based on all visible vertebras and one where vertebras enclosing metastases were manually excluded (w/o Mets SPECT). Results. The planar method, the hybrid methods mean SPECT, median SPECT, and w/o Mets SPECT, yielded absorbed bone marrow doses after treatment cycle one at 0.19 (0.12-0.32), 0.35 (0.12-1.25), 0.29 (0.11-0.92) and 0.29 (0.15-0.81) Gy/7.4 GBq, respectively. A significant dose-response relationship was established after treatment cycle one between decreased platelet counts and absorbed bone marrow dose using the planar method (p=0.025, r=-0.16). With hybrid methods, a significant correlation was firstly found after treatment cycle two between absorbed dose and decreased platelet counts using median SPECT (p=0.018, r=-0.35). Conclusion. Early significant dose-response relationships were established. Despite using SARec-reconstructed SPECT-imaging for specific measurement of activity concentration in bone marrow cavities, the hybrid methods were not able to perform better than the planar method. The hybrid methods yielded higher absorbed bone marrow doses compared to the planar method as both bone metastases and cross-irradiation will influence the activity quantification. Further studies on minimizing influence of bone metastases and cross-irradiation are on-going.
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| 4. |
- Hemmingsson, Jens, 1986, et al.
(author)
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Autoradiography and biopsy measurements of a resected hepatocellular carcinoma treated with 90 yttrium radioembolization demonstrate large absorbed dose heterogeneities
- 2018
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In: Advances in Radiation Oncology. - : Elsevier BV. - 2452-1094. ; 3:3, s. 439-446
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Journal article (peer-reviewed)abstract
- © 2018 The Authors Purpose: Radioembolization is an alternative palliative treatment for hepatocellular carcinoma. Here, we examine the uptake differences between tumor tissue phenotypes and present a cross-section of the absorbed dose throughout a liver tissue specimen. Methods and materials: A patient with hepatocellular carcinoma was treated with90Y radioembolization followed by liver tissue resection. Gamma camera images and autoradiographs were collected and biopsy tissue samples were analyzed using a gamma well counter and light microscopy. Results: An analysis of 25 punched biopsy tissue samples identified 4 tissue regions: Normal tissue, viable tumor tissue with and without infarcted areas, and tumor areas with postnecrotic scar tissue. Autoradiography and biopsy tissue sample measurements showed large dose differences between viable and postnecrotic tumor tissue (159 Gy vs 23 Gy). Conclusions: Radioembolization of 90 yttrium with resin microspheres produces heterogeneous-absorbed dose distributions in the treatment of unifocal hepatic malignancies that could not be accurately determined with current gamma camera imaging techniques.
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| 5. |
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| 6. |
- Högberg, Jonas, 1976, et al.
(author)
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Increased absorbed liver dose in Selective Internal Radiation Therapy (SIRT) correlates with increased sphere-cluster frequency and absorbed dose inhomogeneity
- 2015
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In: EJNMMI Physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 2:1
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Journal article (peer-reviewed)abstract
- Background The higher tolerated mean absorbed dose for selective internal radiation therapy (SIRT) with intra-arterially infused 90Y microspheres compared to external beam therapy is speculated to be caused by absorbed dose inhomogeneity, which allows for liver regeneration. However, the complex liver microanatomy and rheology makes modelling less valuable if the tolerance doses are not based on the actual microsphere distribution. The present study demonstrates the sphere distribution and small-scale absorbed dose inhomogeneity and its correlation with the mean absorbed dose in liver tissue resected after SIRT. Methods A patient with marginally resectable cholangiocarcinoma underwent SIRT 9 days prior to resection including adjacent normal liver tissue. The resected specimen was formalin-fixed and sliced into 1 to 2-mm sections. Forty-one normal liver biopsies 6-8 mm in diameter were punched from these sections and the radioactivity measured. Sixteen biopsies were further processed for detailed analyses by consecutive serial sectioning of 15 30-μm sections per biopsy, mounted and stained with haematoxylin-eosin. All sections were scrutinised for isolated or conglomerate spheres. Small-scale dose distributions were obtained by applying a 90Y-dose point kernel to the microsphere distributions. Results A total of 3888 spheres were found in the 240 sections. Clusters were frequently found as strings in the arterioles and as conglomerates in small arteries, with the largest cluster comprising 453 spheres. An increased mean absorbed dose in the punch biopsies correlated with large clusters and a greater coefficient of variation. In simulations the absorbed dose was 5–1240 Gy; 90% were 10-97 Gy and 45% were <30 Gy, the assumed tolerance in external beam therapy. Conclusions Sphere clusters were located in both arterioles and small arteries and increased in size with increasing sphere concentration, resulting in increased absorbed dose inhomogeneity, which contradicts earlier modelling studies.
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| 7. |
- Högberg, Jonas, 1976, et al.
(author)
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Simulation Model of Microsphere Distribution for Selective Internal Radiation Therapy Agrees With Observations
- 2016
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In: International Journal of Radiation Oncology Biology Physics. - : Elsevier BV. - 0360-3016. ; 96:2, s. 414-421
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Journal article (peer-reviewed)abstract
- Purpose: To perform a detailed analysis of microsphere distribution in biopsy material from a patient treated with 90 Y-labeled resin spheres and characterize microsphere distribution in the hepatic artery tree, and to construct a novel dichotomous bifurcation model for microsphere deposits and evaluate its accuracy in simulating the observed microsphere deposits. Methods and Materials: Our virtual model consisted of arteries that successively branched into 2 new generations of arteries at 20 nodes. The artery diameter exponentially decreased from the lowest generation to the highest generation. Three variable parameters were optimized to obtain concordance between simulations and measure microsphere distributions: an artery coefficient of variation (ACV) for the diameter of all artery generations and the microsphere flow distribution at the nodes; a hepatic tree distribution volume (HDV) for the artery tree; and an artery diameter reduction (ADR) parameter. The model was tested against previously measured activity concentrations in 84 biopsies from the liver of 1 patient. In 16 of 84 biopsies, the microsphere distribution regarding cluster size and localization in the artery tree was determined via light microscopy of 30-mm sections (mean concentration, 14 microspheres/mg; distributions divided into 3 groups with mean microsphere concentrations of 4.6, 14, and 28 microspheres/mg). Results: Single spheres and small clusters were observed in terminal arterioles, whereas large clusters, up to 450 microspheres, were observed in larger arterioles. For 14 microspheres/mg, the optimized parameter values were ACV = 0.35, HDV = 50 cm(3), and ADR = 6 mu m. For 4.6 microspheres/mg, ACV and ADR decreased to 0.26 and 0 mu m, respectively, whereas HDV increased to 130 cm(3). The opposite trend was observed for 28 microspheres/mg: ACV = 0.49, HDV = 20 cm(3), and ADR = 8 mu m. Conclusion: Simulations and measurements reveal that microsphere clusters are larger and more common in volumes with high microsphere concentrations and indicate that the spatial distribution of the artery tree must be considered in estimates of microsphere distributions.
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| 8. |
- Magnander, Tobias, et al.
(author)
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A fast GPU code for full Monte Carlo based SPECT reconstruction
- 2016
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In: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer. - 1619-7070 .- 1619-7089.
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Conference paper (other academic/artistic)abstract
- To improve image quality in SPECT/CT reconstructions, various approximate recovery resolution techniques have been developed and implemented in clinical practice. However, optimal image reconstruction requires accounting for all physical interactions of the emitted photons in the individual patient. The objectives for this study were to develop a novel Monte Carlo (MC) code for fast simulation of individual image projections, and to implement these projections in ordered subset expectation maximum (OSEM) reconstructions of SPECT/CTimages.Method: The MC code was written in Compute Unified Device Architecture language for a computer with four graphic processing units (GeForce GTX Titan X, Nvidia, USA). This enables simulations of parallel photon emission from the voxels matrix (1283 or 2563). Each CT number was converted to attenuation coefficients for photo absorption, coherent scattering and incoherent scattering. The type of interaction was determined by the ratio of attenuation coefficients in the CT voxels. For photon scattering the deflection angle was determined by the differential scattering cross sections. The accepted angle for photon interaction with the crystal was determined from the diameter and height of the collimator hole. Predefined energy and spatial resolution kernels for the crystal were used. TheMCcode was implemented intoOSEMreconstruction of 177Lu, 111In and 99mTc SPECT/CT images. The National Electrical Manufacturers Association (NEMA) image quality phantom was used to evaluate the performance of the MC reconstruction in comparison with clinical standard OSEM reconstructions and clinical state-of-the-art OSEM reconstructions with recovery resolution corrections. Results and conclusion: The performance of the MC code was 500 millions photons/s. The required number of photons emitted per voxel for obtaining low noise in the simulated image was 400 for a 1283 voxel matrix. With this number of emitted photons/voxel the MC-based OSEM reconstruction with 10 subsets was performed within 60 s/iteration. The images converged after 2-4 iterations, depending on the sphere sizes in the NEMAphantom. Thereby, the reconstruction time was <4 minutes. The contrast-to-noise level was slightly improved with increased number of emitted photons/voxel, and the reconstruction time was linearly depending on the number of emitted photons/voxel. The signal-to-background for the spheres in the NEMA phantom was clearly improved with MC-based OSEM reconstruction: e.g. for 177Lu the improvement was 37% compared to standard OSEM and 20 % compared to state-of-the-art OSEM. Furthermore, visual inspection of clinical investigations revealed clearly improved resolution and contrast with MC-based reconstruction.
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| 9. |
- Magnander, Tobias, et al.
(author)
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A novel statistical analysis method to improve the detection of hepatic foci of (111)In-octreotide in SPECT/CT imaging.
- 2016
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In: EJNMMI physics. - : Springer Science and Business Media LLC. - 2197-7364. ; 3:1
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Journal article (peer-reviewed)abstract
- Low uptake ratios, high noise, poor resolution, and low contrast all combine to make the detection of neuroendocrine liver tumours by (111)In-octreotide single photon emission tomography (SPECT) imaging a challenge. The aim of this study was to develop a segmentation analysis method that could improve the accuracy of hepatic neuroendocrine tumour detection.
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| 10. |
- Magnander, Tobias, et al.
(author)
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Improved detection rate and visualization of liver uptake foci in diagnostic 111In-octreotide SPECT/CT investigations with a novel segmentation analysis
- 2015
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In: Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015.
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Conference paper (other academic/artistic)abstract
- Purpose: Detection of liver tumors will change the course of treatment of neuroendocrine tumours. In nuclear medicine 111In-octreoscan is of high value for detection of neuroendocrine tumours. However, neuroendocrine tumours disseminated to the livers is often challenging to detect from 111In-octreoscan SPECT images due to low uptake, high noise, poor resolution and low contrast. The aim of the present study was to develop a segmentation analysis method for increased diagnostic accuracy of neuroendocrine liver tumours. Methods: For the SPECT reconstruction 120 projections are acquired with 3 degrees spacing around the patient injected with 111In-octreoscan. The projections are reconstructed into a 128x128x128 voxel matrix using OSEM with CT based attenuation correction. The liver is segmented from the SPECT or CT using either an isosurface, region growing or a GPU accelerated level set algorithm. Manual editing finishes the segmentation of the liver. The segmented liver volume of interest, liver VOI, is thresholded at 125 equidistant threshold values between 0 and the maximum voxel value. At each threshold value a connected component labeling algorithm is used to calculate the number of uptake foci (NUF). The normalized NUF (nNUF) is then plotted against the threshold index (ThI), defined as ThI=(cmax-cthr)/cmax, where cmax is the maximal voxel value in the VOI, and cthr is the voxel threshold value. The method is named nNUFTI - normalized Number of Uptake Foci vs ThI. The ThI at 0.25 nNUF was used for analysis of liver tumour involvement. SPECT images from 53 patients without tumour involvement (i.e SPECT negative) in the liver were analysed with nNUFTI. A three year follow up with MRI, SPECT, PET/CT and CT was used to separate the patients into two groups: the healthy group, with still no liver tumours, and the malignant group, shown to have developed tumours in the liver. Results: 40 patients ended up in the healthy group and 13 in the malignant group. The ThI at 0.25 nNUF was significantly different between the groups (p<0.01). A probability function for the ThI values was constructed from the obtained data. This relationship might be a useful guide in the diagnostic decision making. Conclusions: Our new developed method nNUFTI has been shown to perform well. More studies on the nNUFTI method are needed.
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| 11. |
- Magnander, Tobias, et al.
(author)
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IMPROVED PLANAR KIDNEY ACTIVITY CONCENTRATION ESTIMATE BY THE POSTERIOR VIEW METHOD IN 177LU-DOTATATE TREATMENTS.
- 2016
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In: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 169:1-4, s. 259-266
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Journal article (peer-reviewed)abstract
- The aims of this study were to determine how different background regions of interest (ROIs) around the kidney represent true background activity in over- and underlying tissues in(177)Lu-DOTA-octreatate ((177)Lu-DOTATATE) treatments and to determine the influence of the background positions on the kidney activity concentration estimates by the conjugate view (ConjV) and posterior view (PostV) methods. The analysis was performed in single-photon emission computed tomography (SPECT) images of 20 patients, acquired 24 h post injection of a(177)Lu-DOTATATE treatment, by a computer algorithm that created planar images from the SPECT data. The ratio between the activity concentration in the background and the true background varied from 0.36 to 2.08 [coefficient of variation (CV) = 25-181 %] and from 0.44 to 1.52 (CV = 16-70 %) for the right and left kidneys, respectively. The activity concentration estimate in the kidneys was most accurate with the PostV method using a background ROI surrounding the whole kidney, and this combination might be an alternative planar method for improved kidney dosimetry in the(177)Lu-DOTATATE treatments.
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| 12. |
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| 13. |
- Polte, Christian Lars, et al.
(author)
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Cardiac Positron Emission Tomography: a Clinical Perspective
- 2016
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In: Current Cardiovascular Imaging Reports. - : Springer Science and Business Media LLC. - 1941-9066 .- 1941-9074. ; 9:3
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Journal article (peer-reviewed)abstract
- © 2016, Springer Science+Business Media New York. Cardiac positron emission tomography is a powerful, quantitative, non-invasive imaging modality, which adds valuable diagnostic and prognostic information to the clinical work-up. Myocardial perfusion and viability imaging are, as a result of continuously growing evidence, established clinical indications that may be cost-effective, due to the high diagnostic accuracy of cardiac positron emission tomography, despite high single-test costs. In the field of inflammation imaging, new indications are entering the clinical arena, which may contribute to a better diagnosis and overall patient care, as for instance in patients with cardiac sarcoidosis, prosthetic valve endocarditis and cardiac device infections. This review will discuss the individual strengths and weaknesses of cardiac positron emission tomography and, hence, the resulting clinical usefulness based on the current evidence for an individualized, patient-centered imaging approach.
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| 14. |
- Waldenström, Ann-Charlotte, 1950, et al.
(author)
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A comparison of two imaging modalities for detecting lymphatic nodal spread in radiochemotherapy of locally advanced cervical cancer
- 2018
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In: Physics and Imaging in Radiation Oncology. - : Elsevier BV. - 2405-6316. ; 8, s. 33-37
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Journal article (peer-reviewed)abstract
- Background and purpose: In uterine cervical cancer tumour spread reaching the para-aortic lymph nodes is the most significant independent pre-treatment predictor of progression-free survival. When introducing [18F] fluorodeoxyglucose-positron emission tomography (FDG-PET)/computed tomography (CT) in our clinic for patients with advanced cervical cancer planned for definitive radiochemotherapy, the purpose of this study was to quantify to what extent the added information lead to changes in radiotherapy planning. Material and methods: We included 25 consecutive patients with cervical cancer stages IB2 – IIIB planned for definitive radiochemotherapy between November 2010 and May 2012. The patients were examined both with magnetic resonance imaging (MRI) and FDG-PET/CT before treatment and after four weeks of treatment. Results: In 11/24 (46%) of the patients the FDG-PET/CT before treatment provided additional diagnostic information leading to changes in treatment planning compared to information from MRI. Seven of these eleven patients (64%) were alive and without evidence of disease at four-year follow-up. The MRI detected pelvic tumour spread not seen on the FDG-PET/CT in 2/24 patients. The disease-free four-year survival was 59%. Conclusions: Additional diagnostic information from FDG-PET/CT changed treatment strategy in almost half of the patients and may have increased chances of survival in this limited group of patients with locally advanced uterine cervical cancer. We recommend both modalities for nodal detection.
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