| 1. |
- Adjeiwaah, Mary, 1980-, et al.
(författare)
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Dosimetric Impact of MRI Distortions : A Study on Head and Neck Cancers
- 2019
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 103:4, s. 994-1003
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate the effect of magnetic resonance (MR) imaging (MRI) geometric distortions on head and neck radiation therapy treatment planning (RTP) for an MRI-only RTP. We also assessed the potential benefits of patient-specific shimming to reduce the magnitude of MR distortions for a 3-T scanner.Methods and Materials: Using an in-house Matlab algorithm, shimming within entire imaging volumes and user-defined regions of interest were simulated. We deformed 21 patient computed tomography (CT) images with MR distortion fields (gradient nonlinearity and patient-induced susceptibility effects) to create distorted CT (dCT) images using bandwidths of 122 and 488 Hz/mm at 3 T. Field parameters from volumetric modulated arc therapy plans initially optimized on dCT data sets were transferred to CT data to compute a new plan. Both plans were compared to determine the impact of distortions on dose distributions.Results: Shimming across entire patient volumes decreased the percentage of voxels with distortions of more than 2 mm from 15.4% to 2.0%. Using the user-defined region of interest (ROI) shimming strategy, (here the Planning target volume (PTV) was the chosen ROI volume) led to increased geometric for volumes outside the PTV, as such voxels within the spinal cord with geometric shifts above 2 mm increased from 11.5% to 32.3%. The worst phantom-measured residual system distortions after 3-dimensional gradient nonlinearity correction within a radial distance of 200 mm from the isocenter was 2.17 mm. For all patients, voxels with distortion shifts of more than 2 mm resulting from patient-induced susceptibility effects were 15.4% and 0.0% using bandwidths of 122 Hz/mm and 488 Hz/mm at 3 T. Dose differences between dCT and CT treatment plans in D-50 at the planning target volume were 0.4% +/- 0.6% and 0.3% +/- 0.5% at 122 and 488 Hz/mm, respectively.Conclusions: The overall effect of MRI geometric distortions on data used for RTP was minimal. Shimming over entire imaging volumes decreased distortions, but user-defined subvolume shimming introduced significant errors in nearby organs and should probably be avoided.
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| 2. |
- Adjeiwaah, Mary, 1980-
(författare)
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Quality assurance for magnetic resonance imaging (MRI) in radiotherapy
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of Magnetic Resonance Imaging (MRI) in the radiotherapy (RT) treatment planning workflow is increasing. MRI offers superior soft-tissue contrast compared to Computed Tomography (CT) and therefore improves the accuracy in target volume definitions. There are, however concerns with inherent geometric distortions from system- (gradient nonlinearities and main magnetic field inhomogeneities) and patient-related sources (magnetic susceptibility effect and chemical shift). The lack of clearly defined quality assurance (QA) procedures has also raised questions on the ability of current QA protocols to detect common image quality degradations under radiotherapy settings. To fully implement and take advantage of the benefits of MRI in radiotherapy, these concerns need to be addressed.In Papers I and II, the dosimetric impact of MR distortions was investigated. Patient CTs (CT) were deformed with MR distortion vector fields (from the residual system distortions after correcting for gradient nonlinearities and patient-induced susceptibility distortions) to create distorted CT (dCT) images. Field parameters from volumetric modulated arc therapy (VMAT) treatment plans initially optimized on dCT data sets were transferred to CT data to compute new treatment plans. Data from 19 prostate and 21 head and neck patients were used for the treatment planning. The dCT and CT treatment plans were compared to determine the impact of distortions on dose distributions. No clinically relevant dose differences between distorted CT and original CT treatment plans were found. Mean dose differences were < 1.0% and < 0.5% at the planning target volume (PTV) for the head and neck, and prostate treatment plans, respectively. Strategies to reduce geometric distortions were also evaluated in Papers I and II. Using the vendor-supplied gradient non-linearity correction algorithm reduced overall distortions to less than half of the original value. A high acquisition bandwidth of 488 Hz/pixel (Paper I) and 488 Hz/mm (Paper II) kept the mean geometric distortions at the delineated structures below 1 mm. Furthermore, a patient-specific active shimming method implemented in Paper II significantly reduced the number of voxels with distortion shifts > 2 mm from 15.4% to 2.0%.B0 maps from patient-induced magnetic field inhomogeneities obtained through direct measurements and by simulations that used MR-generated synthetic CT (sCT) data were compared in Paper III. The validation showed excellent agreement between the simulated and measured B0 maps.In Paper IV, the ability of current QA methods to detect common MR image quality degradations under radiotherapy settings were investigated. By evaluating key image quality parameters, the QA protocols were found to be sensitive to some of the introduced degradations. However, image quality issues such as those caused by RF coil failures could not be adequately detected.In conclusion, this work has shown the feasibility of using MRI data for radiotherapy treatment planning as distortions resulted in a dose difference of less than 1% between distorted and undistorted images. The simulation software can be used to produce accurate B0 maps, which could then be used as the basis for the effective correction of patient-induced field inhomogeneity distortions and for the QA verification of sCT data. Furthermore, the analysis of the strengths and weaknesses in current QA tools for MRI in RT contribute to finding better methods to efficiently identify image quality errors.
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| 3. |
- Adjeiwaah, Mary, et al.
(författare)
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Quantifying the Effect of 3T Magnetic Resonance Imaging Residual System Distortions and Patient-Induced Susceptibility Distortions on Radiation Therapy Treatment Planning for Prostate Cancer
- 2018
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 100:2, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the effect of magnetic resonance system- and patient-induced susceptibility distortions from a 3T scanner on dose distributions for prostate cancers.Methods and Materials: Combined displacement fields from the residual system and patient-induced susceptibility distortions were used to distort 17 prostate patient CT images. VMAT dose plans were initially optimized on distorted CT images and the plan parameters transferred to the original patient CT images to calculate a new dose distribution.Results: Maximum residual mean distortions of 3.19 mm at a radial distance of 25 cm and maximum mean patient-induced susceptibility shifts of 5.8 mm were found using the lowest bandwidth of 122 Hz per pixel. There was a dose difference of <0.5% between distorted and undistorted treatment plans. The 90% confidence intervals of the mean difference between the dCT and CT treatment plans were all within an equivalence interval of (−0.5, 0.5) for all investigated plan quality measures.Conclusions: Patient-induced susceptibility distortions at high field strengths in closed bore magnetic resonance scanners are larger than residual system distortions after using vendor-supplied 3-dimensional correction for the delineated regions studied. However, errors in dose due to disturbed patient outline and shifts caused by patient-induced susceptibility effects are below 0.5%.
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| 4. |
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| 5. |
- Ambjörnsson, Joakim, et al.
(författare)
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Prehospital suspicion and identification of adult septic patients : Experiences of a screening tool
- 2016
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Ingår i: 2nd Global Conference on Emergency Nursing and Trauma Care, Melia Sitges, September 22-24, 2016.
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Konferensbidrag (refereegranskat)abstract
- Introduction: Sepsis is life threatening and requires urgent healthcare to reduce suffering and death. Therefore it is important that septic patients are identified early to enable treatment. Aim: To investigate to what extent EMS personnel identified patients with sepsis using the “BAS 90-30-90” model, and to describe assessments and medical procedures that were undertaken by the personnel.Methods: This was a retrospective study where 185 EMS medical records were reviewed. The inclusion was based on patients who were later diagnosed with sepsis in the hospital. Results: A physician assessed the patients in 74 of the EMS cases, which lead to exclusion of these records in regard to the EMS personnel’s ability to identify sepsis. The personnel documented suspicion of severe sepsis in eight (n=8) of the remaining 111 records (7.2%). The proportion of patients ˃65 years of age was 73% (n=135) of which 37% (n=50) were over 80 years old. Thirty-nine percent (39%, n=72) were females. The personnel documented blood pressure in 91% (n=168), respiratory rate in 76% (n=140), saturation in 100% (n=185), temperature in 76% (n=141), and heart rate in 94% (n=174) of the records. Systolic blood pressure <90 mmHg was documented in 14,2% (n=24), respiratory rate ˃30 in 36% (n=50), saturation <90 in 49% (n=91), temperature >38°C in 37.6% (n=53), and heart rate ˃90 in 70% (n=121) of the records. Documented medical procedures and treatments were intravenous lines (70%, n=130), intravenous fluids (10%, n=19) and administration of oxygen (72%, n=133).Conclusion: The EMS personnel identified only a few septic patients with the help of the BAS 90-30-90 model when all three criteria would be met for severe sepsis. Either advanced age (>65 years), fever (>38°C) or tachypnea (˃20 breaths/min) appeared to increase the personnel’s suspicion of sepsis. Oxygen, but not intravenous fluids, was given in an adequate way.
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| 7. |
- Andersson, Joakim, 1964, et al.
(författare)
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Big Data in spare parts supply chains: The potential of using product-in-use data in aftermarket demand planning
- 2018
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Ingår i: International Journal of Physical Distribution and Logistics Management. - 0960-0035. ; 48:5, s. 524-544
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to explore and propose how product-in-use data can be used in, and improve the performance of, the demand planning process for automotive aftermarket services. A literature review and a single-case study investigate the underlying reasons for the demand for spare parts by conducting in-depth interviews, observing actual demand-generating activities, and studying the demand planning process. This study identifies the relevant product-in-use data and divides them into five main categories. We have analysed how product-in-use data is best utilised, in planning spare parts with different attributes, e.g. different life-cycle phases and demand frequencies. Furthermore, we identify eight potentially relevant areas of application of product-in-use data in the demand planning process, and elaborate on their performance effects. This study details the understanding of what impact context has on the potential performance effects of using product-in-use data in aftermarket demand planning. Propositions generate several strands for future research. This study shows the potential impact of using product-in-use data, using eight different types of interventions for spare parts, in the aftermarket demand planning. The literature focuses on single applications of product-in-use data, but would benefit from considering the context of application. This study presents interventions and explores how these enable improved demand planning by analysing usage and effects.
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| 8. |
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| 9. |
- Andersson, Joakim, 1964, et al.
(författare)
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Sales and operations execution: An explorative study on potential effects
- 2020
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Ingår i: Proceedings of the Nofoma conference 2020.
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Konferensbidrag (refereegranskat)abstract
- Purpose Sales and operations planning have a long history in practice and has been researched extensively. It has been proposed that this tactical concept needs to be aligned with a more operational, short-term concept, hence the purpose of this paper is to investigate how sales and operations execution (S&OE) can enhance the performance of a supply chain by analyzing contingency factors regarding design and use. Methodology A multiple-case study approach investigates the potential outcome of implementing a S&OE process in various contexts. Empirical data from several firms in various industries are analyzed according to common and unique factors affecting the potential result. Findings his study identifies critical design for an S&OE process to have a positive outcome in different contexts. Furthermore, relevant data is identified, as well as actors essential for successful usage. Finally, we present, by using knowledge management theory, the importance of integrating S&OE in the planning hierarchy and how the S&OE practice leads to results. Research implications This study details the understanding of how sales and operations execution affects the supply chain performance, given different contextual aspects. Practical implications This study shows the potential impact of implementing S&OE for different types of businesses, as well as giving guiding principles for its design. Original/value S&OE as a concept is today merely described as white papers and consultancy reports. To our best knowledge, this is the first academic study that explores the sales and execution phenomenon in a real-world context.
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| 10. |
- Andersson, Mattias, et al.
(författare)
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Editor's Choice – Structured Computed Tomography Analysis can Identify the Majority of Patients at Risk of Post-Endovascular Aortic Repair Rupture
- 2022
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier BV. - 1078-5884 .- 1532-2165. ; 64, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The main objective was to report mechanisms and precursors for post-endovascular aneurysm repair (EVAR) rupture. The second was to apply a structured protocol to explore whether these factors were identifiable on follow up computed tomography (CT) prior to rupture. The third objective was to study the incidence, treatment, and outcome of post-EVAR rupture. Methods: This was a multicentre, retrospective study of patients treated with standard EVAR at five Swedish hospitals from 2008 to 2018. Patients were identified from the Swedvasc registry. Medical records were reviewed up to 2020. Index EVAR and follow up data were recorded. The primary endpoint was post-EVAR rupture. CT at follow up and at post-EVAR rupture were studied, using a structured protocol, to determine rupture mechanisms and identifiable precursors. Results: In 1 805 patients treated by EVAR, 45 post-EVAR ruptures occurred in 43 patients. The cumulative incidence was 2.5% over a mean follow up of 5.2 years. The incidence rate was 4.5/1 000 person years. Median time to post-EVAR rupture was 4.1 years. A further six cases of post-EVAR rupture in five patients found outside the main cohort were included in the analysis of rupture mechanisms only. The rupture mechanism was type IA in 20 of 51 cases (39%), IB in 20 of 51 (39%) and IIIA/B in 11 of 51 (22%). One of these had type IA + IB combined. One patient had an aortoduodenal fistula without another mechanism being identified. Precursors had been noted on CT follow up prior to post-EVAR rupture in 16 of 51 (31%). Retrospectively, using the structured protocol, precursors could be identified in 43 of 51 (84%). In 17 of 27 (63%) cases missed on follow up but retrospectively identifiable, the mechanisms were type IB/III. Overall, the 30 day mortality rate after post-EVAR rupture was 47% (n = 24/51) and the post-operative mortality rate was 21% (n = 7/33). Conclusions: Most precursors of post-EVAR rupture are underdiagnosed but identifiable before rupture using a structured follow up CT protocol. Precursors of type IB and III failures caused the majority of post-EVAR ruptures.
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