| 1. |
- Brodén, Cyrus, et al.
(författare)
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Low-dose CT-based implant motion analysis is a precise tool for early migration measurements of hip cups : a clinical study of 24 patients
- 2020
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Ingår i: Acta Orthopaedica. - : Informa UK Limited. - 1745-3674 .- 1745-3682. ; 91:3, s. 260-265
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose - Early implant migration is known to be a predictive factor of clinical loosening in total hip arthroplasty (THA). Radiostereometric analysis (RSA) is the gold standard used to measure early migration in patients. However, RSA requires costly, specialized imaging equipment and the image process is complex. We determined the precision of an alternative, commercially available, CT method in 3 ongoing clinical THA studies, comprising 3 different cups.Materials and methods - 24 CT double examinations of 24 hip cups were selected consecutively from 3 ongoing prospective studies: 2 primary THA (1 cemented and 1 uncemented) and 1 THA (cemented) revision study. Precision of the CT-based implant motion analysis (CTMA) system was calculated separately for each study, using both the surface anatomy of the pelvis and metal beads placed in the pelvis.Results - For the CTMA analysis using the surface anatomy of the pelvis, the precision ranged between 0.07 and 0.31 mm in translation and 0.20° and 0.39° for rotation, respectively. For the CTMA analysis using beads the precision ranged between 0.08 and 0.20 mm in translation and between 0.20° and 0.43° for rotations. The radiation dose ranged between 0.2 and 2.3 mSv.Interpretation - CTMA achieved a clinically relevant and consistent precision between the 3 different hip cups studied. The use of different hip cup types, different CT scanners, or registration method (beads or surface anatomy) had no discernible effect on precision. Therefore, CTMA without the use of bone markers could potentially be an alternative to RSA to measure early migration.
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| 2. |
- Sandberg, Olof H., et al.
(författare)
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Computed tomography-based radiostereometric analysis in orthopedic research: practical guidelines
- 2023
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Ingår i: ACTA ORTHOPAEDICA. - : Medical Journals Sweden. - 1745-3674 .- 1745-3682. ; 94, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- - Early implant migration is an indicator of the long-term survival/failure of implants. CT-based radio-stereometric analysis (CT-RSA) is a precise method for mea-suring and visualizing implant migration in vivo using image processing of CT scans. This makes the method widely applicable to orthopedic researcher. Since its development in the early 2000s, CT-RSA has benefited from breakthroughs in CT and computing technol-ogy. These advancements have allowed for the acquisition of images with higher resolution at a much lower radiation dose. As a result, the measurement precision of CT-RSA is now comparable to that of the current gold standard technol-ogy while still compatible with most ethical considerations regarding radiation exposure. In this review we present bests practices for the successful execution of CT-RSA research projects. These practices are based on experience from projects on the hip, knee, shoulder, lower back, cervical spine, foot, pelvis, and wrist.
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| 3. |
- Ferritsius, Rita, et al.
(författare)
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Development of fibre properties in mill scale high- And low consistency refining of thermomechanical pulp (Part 1)
- 2020
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Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 35:4, s. 589-599
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate changes in fibre properties with high (HC)- and low consistency (LC) refining of TMP and determine how these contribute to tensile index. Two process configurations, one with only HC refining and another with HC refining followed by LC refining were evaluated in three TMP mainline processes in two mills using Norway spruce. An increase in tensile index for a given applied specific energy was similar for all LC refiners in the three lines, despite differences in the fibre property profiles of the feed pulps. Compared with only HC refined pulps at a given tensile index, HC+LC refined pulps had greater fibre wall thickness, similar fibre length, strain at break and freeness, but lower light scattering coefficient, fibre curl and external fibrillation. The degree of internal fibrillation, determined by Simons' stain measurements, was similar for both configurations at a given tensile index. The results indicate that the increase in tensile index in LC refining is largely influenced by a decrease in fibre curl and in HC refining by peeling of the fibre walls. Compared at a given tensile index, the shive content (Somerville mass fraction) was similar for both HC+LC and HC refining.
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| 4. |
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| 5. |
- Hyll, Kari, et al.
(författare)
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CT-skanning som verktyg för detektering av törskateangrepp på tall
- 2022
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Rapport (refereegranskat)abstract
- Scots pine blister rust fungi (Cronartium pini) is expected to become an increasing problem for both forest owners and sawmills in the Nordic region, and there is great uncertainty about the economic consequences. There is also a lack of knowledge about the biology of Scots pine blister rust, as well as the tree's response and defence against ongoing infection. The tree is known to defend itself by enriching resin at the infected area, creating a damaged area of resin-wood. There is currently no reliable way to detect and assess the degree of damage in sawn timber, which leads to waste, as entire sawlogs are usually downgraded when parts or most of the timber could possibly be used. The objectives of this preliminary study were to: (1) investigate whether X-ray computed tomography (CT scanning) can detect blister rust damage in pine timber, in order to optimise sawing and save the value of the sawn timber; (2) to compare the 3-dimensional CT image description of the fungal attack with how the damage looks on the outside, to enable recommendations for external assessment of the damage attack, for example during felling; and (3) to assess the possibilities for describing the course of the damage and the tree's defence against the fungal attack.Eight rust-infested and two non-infested trees (Scots pine) were collected from a thinning stand and a mature stand outside Bjurselet, Norsjö municipality in Västerbotten. The trees were felled in January 2022. After felling, the stems were visually inspected, and infected parts were marked with paint on the mantle surface. The stems were cut into logs of suitable length for transport and scanning. Cuts through fungal-infested regions were avoided. The wood was transported to LTU’s Wood Science and Engineering facility in Skellefteå for CT scanning.The CT scan of the sample trees showed that damage due to pine blister rust can be detected in a way that enables further development of an industrial detection method and optimisation of the wood decomposition. However, one difficulty discovered was that fungal-infested sapwood areas have similar image intensity as non-infested heartwood. It could also be established that the distribution of damage inside the volume of the stem is greater than can be detected visually on the mantle, especially in the longitudinal direction. In this study the temporal development of the infection from the time of infestation to the time of CT scanning could not be analysed. However, annual rings could be distinguished in both damaged and undamaged wood, making it possible to monitor the evolution of the damage from year to year. DNA analysis detected the presence of blister rust fungus in the wood, both in and outside resin-rich areas. The highest amount of fungus-specific DNA was measured outside the resin-rich area in the outer parts of the sapwood.
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| 6. |
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| 7. |
- Lovera, Davide, et al.
(författare)
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Cost-effectiveness of implant movement analysis in aseptic loosening after hip replacement: a health-economic model.
- 2023
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Ingår i: Cost effectiveness and resource allocation : C/E. - 1478-7547. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the cost-effectiveness of using Implant Movement Analysis (IMA) to follow up suspected aseptic loosening when the diagnosis after an initial X-ray is not conclusive, compared with a diagnostic pathway with X-ray follow-up.A health-economic model in the form of a decision tree was developed using quality-adjusted life years (QALY) from the literature, cost-per-patient data from a university hospital and the probabilities of different events from expert physicians' opinions. The base case incremental cost-effectiveness ratio (ICER) was compared with established willingness-to-pay thresholds and sensitivity analyses were performed to account for assumptions and uncertainty.The base case ICER indicated that the IMA pathway was cost effective (SEK 99,681, compared with the SEK 500,000 threshold). In the sensitivity analysis, the IMA pathway remained cost effective during most changes in parameters. ICERs above the threshold value occurred in cases where a larger or smaller proportion of people receive immediate surgery.A diagnostic pathway using IMA after an inconclusive X-ray for suspected aseptic loosening was cost effective compared with a pathway with X-ray follow-up.
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| 8. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 9. |
- Olofsson, Linus
(författare)
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Machine Learning for Appearance Grading of Sawn Timber using Cameras and X-ray Computed Tomography
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis deals with a new approach for the appearance grading of sawn timber adapted to the requirements of modern sawmilling industries and timber market situations. Appearance grading of sawn timber allows wood products to be made with a specific visual style due to wood features such as knots. Identifying and grading sawn timber by its visual style is a holistic-subjective task that is inherently suitable for humans. However, with the ever-increasing demand for a faster and more consistent grading operation, humans have been replaced by automatic systems during the past few decades. However, the human perception of the appearance of sawn timber is not something easily defined coherently and concisely for use in automatic systems, resulting in automatic systems struggling to perform appearance grading using conventional rule-based grading. As shown in this thesis, machine-learning methods can be used to teach an automatic system to perform holistic-subjective grading in a way that emulates manual grading while still performing the fast and consistent grading associated with automatic systems. This thesis introduced machine learning for product-adapted appearance grading of sawn timber and studied the use of machine learning to appearance grade sawn timber according to standardised quality grades, using an X-ray computed tomography (CT) scanner and a camera-based board scanner.In the studies presented in this thesis, measurement data from the CT scan-ner and the board scanner was used to create a set of variables only regarding knots. The variable sets and the grades of the sawn timber were modelled by projection to latent structures (PLS) models. The grade of the sawn timber was determined in three ways; firstly, manual grading according to standard-ised quality grades; secondly, called the product grade, the sawn timber was delivered to a wall-panelling customer, and the grade of the sawn timber was determined by the quality yield at the customer; and thirdly, called the image grade, images were extracted from the board scanner and used to estimate the quality yield of the wall-panelling customer manually. The grading in each scanning system was performed using a machine-learning method and a conventional rule-based approach, and their performances were compared.Seven data sets were collected in the studies presented in this thesis, each with a combination of variable sets from the scanners and quality grades as described above. In each study, one or more PLS models were trained to model the relationship between a variable set and a quality grade and used to predict the quality of the sawn timber. A PLS model predicts a score for each piece of sawn timber, and if that score passes a classification threshold, the model assigns a quality grade. This classification threshold could be tuned manually to introduce a bias in the model and thereby change the sorting outcome.When performing standardised appearance grading of dried sawn timber, both a PLS model and rule-based grading achieved about 80% grading accuracy, while a manual grader agreed to 95% with the PLS model and to 81% with the rule-based grading in a verification test. Furthermore, when performing customer-adapted grading of the standardised grades, a PLS model managed an 84% grading accuracy compared to 64% of the rule-based approach. These results show how a conventional rule-based ap-proach struggled with performing customer-adapted grading compared to a PLS model. When performing standardised grading, however, both meth-ods achieved similar grading accuracy, but only the grading performed by the PLS model could not be significantly distinguished from the targeted standardised grades.Using a PLS model to perform product-adapted grading of dried sawn tim-ber resulted in a grading accuracy of about 70%–80% for di˙erent scenarios. These gradings resulted in a quality yield, pass or fail, of about 80% for the wall-panelling customer. According to the customer, rule-based grad-ing did not yield impressive product-adapted results, and no metric was given. Furthermore, this thesis showed that the image grade was as useful as the product grade for training the PLS models, which greatly simplifies the logistical process of creating a data set for training a product-adapted machine-learning model. Had a traceability method been used to collect the data from the scanners automatically, the image grade would allow for completely software-based data collection, which is very much in line with the industry 4.0 concept.A CT scanner enables the appearance grading of virtual sawn timber in the 3D images of the scanned logs, which allows the logs to be sawn for maxi-mum value or quality yield. The CT scanner was made to perform a primary product-adapted grading using either a PLS model or a rule-based approach. In addition to this primary grading, the CT scanner and board scanner were programmed to perform a small secondary grading by limiting a small set of measurements that the CT scanner could not suÿciently account for. For example, large pith deviations were limited in the CT scanner, and rotten knots were forbidden by the board scanner, as these measurements were associated with a high risk of resulting in poor quality wall panels for the customer. With this setup, a dataset of 300 pieces of virtual sawn timber was studied. Using rule-based primary grading, the sawmill delivered about 200 pieces of sawn timber with a product yield of 77% for the customer, after the board scanner rejected 28 pieces (12%). Then, by controlling the classification threshold of a PLS model to make the primary grading very strict, meaning that the log was sawn to only yield very likely high-quality pieces of sawn timber, the sawmill could deliver 114 pieces of sawn timber with a product yield of 90%, after the board scanner rejected 9 pieces (7%). These results show that a PLS model achieved higher grading accuracy and higher quality yield than a rule-based approach. Furthermore, the classifica-tion threshold of the PLS model allows for easy and intuitive control over the sorting outcome, something that the rule-based approach does not support.This thesis showed that a PLS-based machine-learning model could be used to perform holistic-subjective appearance grading by both a CT scanner and a board scanner, where a rule-based approach struggled in all but the most familiar case of standardised grading. Once a framework for a machine-learning method such as PLS has been implemented, this thesis showed the ease of customising and fine-tuning the grading performance to be in line with customers needs. A customer or product adaptation could conceivably be initiated and finalised completely in software by automatically collecting the data using a traceability method, collecting the reference grades needed for training by grading images of sawn timber, and using the intuitive clas-sification threshold to fine-tune the sorting outcome.
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| 10. |
- Olofsson, Linus, et al.
(författare)
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Product-adapted grading of Scots pine sawn timber by an industrial CT-scanner using a visually-trained machine-learning method
- 2021
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 16:4, s. 279-286
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Tidskriftsartikel (refereegranskat)abstract
- Computed tomography (CT) scanning of logs makes appearance-grading virtual sawn timber possible before the log is sawn. A CT-scanner can measure the knot structure inside a scanned log, inferring how to saw the log. The knot structure of virtual sawn timber was graded as being suitable or not for a specific product by the existing rule-based approach and used to create a set of descriptive statistical variables used by two machine learning models. The PLS models were trained on two quality references; the quality grade of the finished product or the image-grade based on images of the sawn timber, extracted from the dry-sorting station's automatic grading system and graded by two experienced researchers. The results show that the two PLS models perform equally well when sorting sawn timber to the customer, indicating that the quality references are equally useful for training a PLS model. The PLS models both delivered 93% of the dried sawn timber to the customer, leaving very little sawn timber with customer-specific properties at the sawmill, of which 89% and 90% of the delivered sawn timber passed the intended product's quality demands. The rule-based approach delivered 85% dried sawn timber with a 73% pass rate.
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| 11. |
- Olofsson, Linus, et al.
(författare)
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The effect of class-balance and class-overlap in the training set for multivariate and product-adapted grading of Scots pine sawn timber
- 2021
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Ingår i: Wood Material Science & Engineering. - London : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 16:1, s. 58-63
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Tidskriftsartikel (refereegranskat)abstract
- Using multivariate partial least squares regression (PLS) to perform visual quality grading of sawn timber requires a training set with known quality grades for the training of a grading model. This study evaluated the grading accuracy of an independent test set of sawn timber when changing the aspects of class-balance and class-overlap of the training set consisting of 251 planks. The study also compared two ways of expressing the reference-grade of the training set; by grading images picturing the planks, and by grading the product produced from the planks. Two grading models were trained using each reference-grade to establish a baseline for comparison. Both models achieved a 76% grading accuracy of the test set, indicating that both reference-grades can be used to train comparable models. To study the class-balance and class-overlap aspects of the training set, 25% of the training set was removed in two training scenarios. The models trained on class-balanced data indicated that class-imbalance of the training set was not a problem. The models trained on data with less class-overlap using the product-grade reference suffered a 4%-points grading accuracy loss due to the smaller training set, while the model trained using the image-grade reference retained its grading accuracy.
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| 12. |
- Sandberg, Christer, 1962-, et al.
(författare)
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Energy efficiency in mechanical pulping-definitions and considerations
- 2021
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 36:3, s. 425-434
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Tidskriftsartikel (refereegranskat)abstract
- Production of mechanical pulps requires high specific electrical energy compared to many other attrition processes. In Scandinavia, the lowest specific refining energy for production of thermomechanical pulp is around 1800 kWh/t for newsprint quality, which is roughly 60 times higher than for crushing of stone to a similar size distribution. The high specific energy demand for refining has naturally motivated large efforts in the search for improved efficiency. It is always practical to be able to quantify improvements in efficiency for comparison of process designs and of different machine types. However, there is no commonly accepted definition of efficiency for mechanical pulping processes. In published work within mechanical pulping, energy efficiency has been presented in different ways. In this paper, we discuss definitions of energy efficiency and aspects that ought to be considered when energy efficiency is presented. Although focus of this work is on energy efficiency for refiner processes, the principles can be applied to other types of mechanical pulping processes such as stone groundwood.
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| 13. |
- Sandberg, Olof, et al.
(författare)
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Inducible displacement CT increases the diagnostic accuracy of aseptic loosening in primary total hip arthroplasty
- 2022
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Ingår i: Acta Orthopaedica. - : Taylor & Francis. - 1745-3674 .- 1745-3682. ; 93, s. 831-836
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Inducible displacement CT compares 2 CTs acquired in series but with alternated rota-tion of the femur. This provides visual and quantitative clues as to the mechanical situation, i.e., loosening, of a total hip arthroplasty. We report the accuracy of this method as well as the experience of integrating it into a clinical workflow.Patients and methods: This was a retrospective single centre study of 72 cases of suspected aseptic loosening were the surgeon after reviewing a standard plain radiograph saw a need for more information. The displacement CT and plain radiograph were compared either to intraoperative findings or a 1-3 year follow up questionnaire for patients that did not have revision surgery. Patients reporting degradation in status since the time of the displacement CT were called for a follow up plain radiograph. Sensitivity and specificity were assessed, and user experience gathered.Results: Of 72 enrolled patients 15 were lost to follow-up. Of the remaining 57, 17 were judged by in-traoperative findings or follow-up to have had loose implants. For plain radiography the sensitivity and specificity were 59% (95% CI 35-82) and 85% (74-96). For displacement CT the cor-responding values were 77% (56-97), and 100% (100-100) respectively. The tool was adaptable to clinical routine.Conclusion: Displacement CT with alternated rota-tions of the femur is a viable option to improve the diag-nostic process for identifying aseptic loosening in a total hip arthroplasty.
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| 14. |
- Sandberg, Olof, et al.
(författare)
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The anatomical SP-CL stem demonstrates a non-progressing migration pattern in the first year : a low dose CT-based migration study in 20 patients
- 2020
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Ingår i: Acta Orthopaedica. - : Taylor & Francis. - 1745-3674 .- 1745-3682. ; 91:6, s. 654-659
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: RSA is the gold standard for evaluation of early implant migration. We report the results of a new CT-based method Sectra CT micromotion analysis (CTMA) applied to assess the migration pattern in 20 patients in the 1st year after surgery, both with and without the use of tantalum beads in the bone. The patients had an SP-CL anatomical stem that uses an S-shape, designed to better fit the curvature of the femur.Patients and methods: 20 THA patients (mean age 61 years, 10 female) received SP-CL stems, tantalum markers in the femur, and low-dose CT scans at 1 day, 3 months and 12 months postoperatively. In addition, precision as well as inter- and intra-observer variability of the 12-month migration was measured.Results: The 3-month subsidence was median 0.5 mm (95% CI 0.3-1.0) and the internal rotation 1.8 degrees (CI 0.9-2.6). At 12 months the corresponding values were 0.6 (CI 0.3-1.6) mm and 1.9 degrees (CI 0.8-2.4). Precision was 0.1 to 0.3 mm and 0.1 degrees to 0.4 degrees at 3 and 12 months. Intra- and inter- observer variability yielded R-values averaging 0.96 and 0.98.Interpretation: The migration mainly took place during the 1st 3 months, in line with other uncemented stems. The number of patients with subsidence over 2 mm in the first year (5) might be due to the design of the prosthesis with an anatomical shape. Alternatively, our results might indicate a challenge when choosing the correct size for these new anatomical stems. CTMA provided precise and highly repeatable measurements of migration without the need for tantalum markers.
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| 15. |
- Sandgren, Olof, et al.
(författare)
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Using a word association task to investigate semantic depth in swedish-speaking children with developmental language disorder
- 2021
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Ingår i: Logopedics Phoniatrics Vocology. - : Informa UK Limited. - 1401-5439 .- 1651-2022. ; 46:3, s. 134-140
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Tidskriftsartikel (refereegranskat)abstract
- We examined word associations in Swedish children with Developmental Language Disorder (DLD) compared to their typically developing (TD) peers. Furthermore, the study aimed to explore the dimensions of vocabulary knowledge (breadth, depth, and fluency) in these children. Fifty children (15 DLD and 35 TD) participated in the study, aged six to nine years. This age span is commonly associated with substantial lexical reorganisation, by some referred to as the syntagmatic-paradigmatic shift. Fifty items from the Kent-Rosanoff list were used to elicit word associations (say the first word that comes to mind). Word associations were coded as paradigmatic (lion-tiger), syntagmatic (chair-sit), phonological (moon-poon), and other/no answer (foot-hello/bed- -). A semantic depth score (paradigmatic and syntagmatic associations) was calculated and analysed. The children with DLD showed significantly lower semantic depth scores than their TD peers, in line with previous research in English-speaking children. However, the vocabulary dimensions were uniformly affected for the DLD group, contradicting previous findings of semantic depth as a particular area of weakness in this group.
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| 16. |
- Sandin, Ylva, et al.
(författare)
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Experiences from the Deconstruction of a Timber Building
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This study reports on a deconstruction process followed on site, with the purpose of documenting experiences that can help us understand how to design timber buildings for future deconstruction and reuse. The deconstruction concerned three timber buildings built up by volumes (3D modules produced off-site). Modules were in good shape at the time of deconstruction except for some minor local moisture damages. They were all covered and transported to be reused elsewhere. Experiences made included that lack of information on the assumed deconstruction process delayed and complicated the work. A need for disassembly plans was highlighted, including things as order of dismantling, positions of lifting points, weight of modules and positions of screws and amount of screw used. Results indicate that simple, clearly visible joints and services, limit the potential problems and damages during deconstruction. The building should simply be designed to be taken down in the future, the amount of screw allowed should be clearly described and the number of attachments should be limited. Furthermore, the risk of burglary during deconstruction needs to be considered as this may cause damage and delay.
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