| 1. |
- Peterson, Pernilla, et al.
(författare)
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Knee dGEMRIC at 7 T : Comparison against 1.5 T and evaluation of T1-mapping methods
- 2018
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Ingår i: BMC Musculoskeletal Disorders. - : Springer Science and Business Media LLC. - 1471-2474. ; 19:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: dGEMRIC (delayed Gadolinium Enhanced Magnetic Resonance Image of Cartilage) is a well-established technique for cartilage quality assessment in osteoarthritis at clinical field strengths. The method is robust, but requires injection of contrast agent and a cumbersome examination procedure. New non-contrast-agent-based techniques for cartilage quality assessment are currently being developed at 7 T. However, dGEMRIC remains an important reference technique during this development. The aim of this work was to compare T1 mapping for dGEMRIC at 7 T and 1.5 T, and to evaluate three T1-mapping methods at 7 T. Methods: The knee of 10 healthy volunteers and 9 patients with early signs of cartilage degradation were examined at 1.5 T and 7 T after a single (one) contrast agent injection (Gd-(DTPA)2-). Inversion recovery (IR) sequences were acquired at both field strengths, and at 7 T variable flip angle (VFA) and Look-Locker (LL) sequences were additionally acquired. T1 maps were calculated and average T1 values were estimated within superficial and deep regions-of-interest (ROIs) in the lateral and medial condyles, respectively. Results: T1 values were 1.8 (1.4-2.3) times longer at 7 T. A strong correlation was detected between 1.5 T and 7 T T1 values (r = 0.80). For IR, an additional inversion time was required to avoid underestimation (bias±limits of agreement - 127 ± 234 ms) due to the longer T1 values at 7 T. Out of the two 3D sequences tested, LL resulted in more accurate and precise T1 estimation compared to VFA (average bias±limits of agreement LL: 12 ± 202 ms compared to VFA: 25 ± 622 ms). For both, B1 correction improved agreement to IR. Conclusion: With an adapted sampling scheme, dGEMRIC T1 mapping is feasible at 7 T and correlates well to 1.5 T. If 3D is to be used for T1 mapping of the knee at 7 T, LL is preferred and VFA is not recommended. For VFA and LL, B1 correction is necessary for accurate T1 estimation.
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| 2. |
- Frostell, Björn M., et al.
(författare)
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Modeling both direct and indirect environmental load of purchase decisions : a web-based tool addressing household metabolism
- 2015
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Ingår i: Environmental Modelling & Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 71, s. 138-147
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Tidskriftsartikel (refereegranskat)abstract
- Consumer awareness is continuously increasing towards pro-environmental behavior. Thus, we developed a web-based environmental feedback tool EcoRunner, which is designed for Swedish households aiming at increasing the awareness in a more pro-environmental direction. The conceptual model of EcoRunner has been developed based on top-down and bottom-up approaches connecting economic activities within a household to environmental pressures (both direct and indirect). In addition, the development of the tool includes a multi-level model aiming at better tailor-made advice to consumers. In this paper, we examine the EcoRunner tool with average single Swedish household expenditures as well as explore options for reductions and systems effects. Analysis shows that food and non-alcoholic beverages, fuel for personal transport (e.g. car) and air transports have significant environmental pressures. In addition, this study suggests that EcoRunner could be used in education systems as an environmental feedback tool to enlighten consumers motivation and change consumption patterns.
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| 3. |
- Grefve, Josefine, et al.
(författare)
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Histopathology-validated gross tumor volume delineations of intraprostatic lesions using PSMA-positron emission tomography/multiparametric magnetic resonance imaging
- 2024
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier. - 2405-6316. ; 31
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Dose escalation in external radiotherapy of prostate cancer shows promising results in terms of biochemical disease-free survival. Boost volume delineation guidelines are sparse which may cause high interobserver variability. The aim of this research was to characterize gross tumor volume (GTV) delineations based on multiparametric magnetic resonance imaging (mpMRI) and prostate specific membrane antigen-positron emission tomography (PSMA-PET) in relation to histopathology-validated Gleason grade 4 and 5 regions.Material and methods: The study participants were examined with [68Ga]PSMA-PET/mpMRI prior to radical prostatectomy. Four radiation oncologists delineated GTVs in 15 study participants, on four different image types; T2-weighted (T2w), diffusion weighted imaging (DWI), dynamic contrast enhanced (DCE) and PSMA-PET scans separately. The simultaneous truth and performance level estimation (STAPLE) algorithm was used to generate combined GTVs. GTVs were subsequently compared to histopathology. We analysed how Dice similarity coefficient (DSC) and lesion coverage are affected by using single versus multiple image types as well as by adding a clinical target volume (CTV) margin.Results: Median DSC (STAPLE) for different GTVs varied between 0.33 and 0.52. GTVPSMA-PET/mpMRI generated the highest median lesion coverage at 0.66. Combining different image types achieved similar lesion coverage as adding a CTV margin to contours from a single image type, while reducing non-malignant tissue inclusion within the target volume.Conclusion: The combined use of mpMRI or PSMA-PET/mpMRI shows promise, achieving higher DSC and lesion coverage while minimizing non-malignant tissue inclusion, in comparison to the use of a single image type with an added CTV margin.
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| 4. |
- Nyholm, Tufve, et al.
(författare)
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MR and CT data with multiobserver delineations of organs in the pelvic areaPart of the Gold Atlas project
- 2018
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Ingår i: Med Phys. - : Wiley. - 0094-2405 .- 2473-4209. ; 45:3, s. 1295-1300
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Tidskriftsartikel (refereegranskat)abstract
- PurposeWe describe a public dataset with MR and CT images of patients performed in the same position with both multiobserver and expert consensus delineations of relevant organs in the male pelvic region. The purpose was to provide means for training and validation of segmentation algorithms and methods to convert MR to CT like data, i.e., so called synthetic CT (sCT). Acquisition and validation methodsT1- and T2-weighted MR images as well as CT data were collected for 19 patients at three different departments. Five experts delineated nine organs for each patient based on the T2-weighted MR images. An automatic method was used to fuse the delineations. Starting from each fused delineation, a consensus delineation was agreed upon by the five experts for each organ and patient. Segmentation overlap between user delineations with respect to the consensus delineations was measured to describe the spread of the collected data. Finally, an open-source software was used to create deformation vector fields describing the relation between MR and CT images to further increase the usability of the dataset. Data format and usage notesThe dataset has been made publically available to be used for academic purposes, and can be accessed from . Potential applicationsThe dataset provides a useful source for training and validation of segmentation algorithms as well as methods to convert MR to CT-like data (sCT). To give some examples: The T2-weighted MR images with their consensus delineations can directly be used as a template in an existing atlas-based segmentation engine; the expert delineations are useful to validate the performance of a segmentation algorithm as they provide a way to measure variability among users which can be compared with the result of an automatic segmentation; and the pairwise deformably registered MR and CT images can be a source for an atlas-based sCT algorithm or for validation of sCT algorithm. (c) 2018 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
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| 5. |
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| 6. |
- Olsson, Lars E, et al.
(författare)
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Basic concepts and applications of functional magnetic resonance imaging for radiotherapy of prostate cancer
- 2019
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier. - 2405-6316. ; 9, s. 50-57
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the interest to integrate magnetic resonance imaging (MRI) in radiotherapy for prostate cancer has increased considerably. MRI can contribute in all steps of the radiotherapy workflow from diagnosis, staging, and target definition to treatment follow-up. Of particular interest is the ability of MRI to provide a wide range of functional measures. The complexity of MRI as an imaging modality combined with the growing interest of the application to prostate cancer radiotherapy, emphasize the need for dedicated education within the radiation oncology community. In this context, an overview of the most common as well as a few upcoming functional MR imaging techniques is presented: the basic methodology and measurement is described, the link between the functional measures and the underlying biology is established, and finally relevant applications of functional MRI useful for prostate cancer radiotherapy are given.
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| 7. |
- Olsson, Lars E., 1971-, et al.
(författare)
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EcoRunner : User Experiences of a Web Based Environmental Feedback Tool Addressing Household Consumption
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Feedback is generally used to monitor progress toward different goals and standards in life, and to adjust behaviour accordingly. EcoRunner was developed as a web-based feedback tool providing environmental and financial information about households’ daily consumption. This paper presents a user experience study of this feedback tool, and addresses the influences of goal-setting on the experience. The results show that people who more often set financial and pro-environmental goals in life find the tool more attractive, more useful, believing it to have influenced their current behaviour and believing it will be helpful when changing (regulating) future consumption behaviour. Conclusions are drawn that feedback tools like EcoRunner may have different effects for different subgroups in society. It is further suggested that EcoRunner could be used as a tool in education, at different levels in schools and higher education, for enlightening consumers about the relationship between household spending and environmental consequences.
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| 8. |
- Persson, Emilia, et al.
(författare)
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MR-OPERA : A Multicenter/Multivendor Validation of Magnetic Resonance Imaging-Only Prostate Treatment Planning Using Synthetic Computed Tomography Images
- 2017
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : ELSEVIER SCIENCE INC. - 0360-3016 .- 1879-355X. ; 99:3, s. 692-700
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To validate the dosimetric accuracy and clinical robustness of a commercially available software for magnetic resonance (MR) to synthetic computed tomography (sCT) conversion, in an MR imaginge-only workflow for 170 prostate cancer patients.Methods and Materials: The 4 participating centers had MriPlanner (Spectronic Medical), an atlas-based sCT generation software, installed as a cloud-based service. A T2-weighted MR sequence, covering the body contour, was added to the clinical protocol. The MR images were sent from the MR scanner workstation to theMriPlanner platform. The sCT was automatically returned to the treatment planning system. Four MR scanners and 2 magnetic field strengths were included in the study. For each patient, a CT-treatment plan was created and approved according to clinical practice. The sCT was rigidly registered to the CT, and the clinical treatment plan was recalculated on the sCT. The dose distributions from the CT plan and the sCT plan were compared according to a set of dose-volume histogram parameters and gamma evaluation. Treatment techniques included volumetric modulated arc therapy, intensity modulated radiation therapy, and conventional treatment using 2 treatment planning systems and different dose calculation algorithms.Results: The overall (multicenter/multivendor) mean dose differences between sCT and CT dose distributions were below 0.3% for all evaluated organs and targets. Gamma evaluation showed a mean pass rate of 99.12% (0.63%, 1 SD) in the complete body volume and 99.97% (0.13%, 1 SD) in the planning target volume using a 2%/ 2-mm global gamma criteria.Conclusions: Results of the study show that the sCT conversion method can be used clinically, with minimal differences between sCT and CT dose distributions for target and relevant organs at risk. The small differences seen are consistent between centers, indicating that an MR imagingeonly workflow using MriPlanner is robust for a variety of field strengths, vendors, and treatment techniques.
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| 9. |
- Zarei, Maryam, et al.
(författare)
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Accuracy of gross tumour volume delineation with [68Ga]-PSMA-PET compared to histopathology for high-risk prostate cancer
- 2024
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Ingår i: Acta Oncologica. - : MJS Publishing, Medical Journals Sweden. - 0284-186X .- 1651-226X. ; 63, s. 503-510
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The delineation of intraprostatic lesions is vital for correct delivery of focal radiotherapy boost in patients with prostate cancer (PC). Errors in the delineation could translate into reduced tumour control and potentially increase the side effects. The purpose of this study is to compare PET-based delineation methods with histopathology.MATERIALS AND METHODS: The study population consisted of 15 patients with confirmed high-risk PC intended for prostatectomy. [68Ga]-PSMA-PET/MR was performed prior to surgery. Prostate lesions identified in histopathology were transferred to the in vivo [68Ga]-PSMA-PET/MR coordinate system. Four radiation oncologists manually delineated intraprostatic lesions based on PET data. Various semi-automatic segmentation methods were employed, including absolute and relative thresholds, adaptive threshold, and multi-level Otsu threshold.RESULTS: The gross tumour volumes (GTVs) delineated by the oncologists showed a moderate level of interobserver agreement with Dice similarity coefficient (DSC) of 0.68. In comparison with histopathology, manual delineations exhibited the highest median DSC and the lowest false discovery rate (FDR) among all approaches. Among semi-automatic approaches, GTVs generated using standardized uptake value (SUV) thresholds above 4 (SUV > 4) demonstrated the highest median DSC (0.41), with 0.51 median lesion coverage ratio, FDR of 0.66 and the 95th percentile of the Hausdorff distance (HD95%) of 8.22 mm.INTERPRETATION: Manual delineations showed a moderate level of interobserver agreement. Compared to histopathology, manual delineations and SUV > 4 exhibited the highest DSC and the lowest HD95% values. The methods that resulted in a high lesion coverage were associated with a large overestimation of the size of the lesions.
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