Augmented navigation

Spinal fixation procedures have the inherent risk of causing damage to vulnerable anatomical structures such as the spinal cord, nerve roots, and blood vessels. To prevent complications, several technological aids have been introduced. Surgical navigation is the most widely used, and guides the surgeon by providing the position of the surgical instruments and implants in relation to the patient anatomy based on radiographic images. Navigation can be extended by the addition of a robotic arm to replace the surgeon’s hand to increase accuracy. Another line of surgical aids is tissue sensing equipment, that recognizes different tissue types and provides a warning system built into surgical instruments. All these technologies are under continuous development and the optimal solution is yet to be found. The aim of this thesis was to study the use of Augmented Reality (AR), Virtual Reality (VR), Artificial Intelligence (AI), and tissue sensing technology in spinal navigation to improve precision and prevent surgical errors. The aim of Paper I was to develop and validate an algorithm for automatizing the intraoperative planning of pedicle screws. An AI algorithm for automatic segmentation of the spine, and screw path suggestion was developed and evaluated. In a clinical study of advanced deformity cases, the algorithm could provide correct suggestions for 86% of all pedicles—or 95%, when cases with extremely altered anatomy were excluded. Paper II evaluated the accuracy of pedicle screw placement using a novel augmented reality surgical navigation (ARSN) system, harboring the above-developed algorithm. Twenty consecutively enrolled patients, eligible for deformity correction surgery in the thoracolumbar region, were operated on using the ARSN system. In this cohort, we found a pedicle screw placement accuracy of 94%, as measured according to the Gertzbein grading scale. The primary goal of Paper III was to validate an extension of the ARSN system for placing pedicle screws using instrument tracking and VR. In a porcine cadaver model, it was demonstrated that VR instrument tracking could successfully be integrated with the ARSN system, resulting in pedicle devices placed within 1.7 ± 1.0 mm of the planed path. Paper IV examined the feasibility of a robot-guided system for semi-automated, minimally invasive, pedicle screw placement in a cadaveric model. Using the robotic arm, pedicle devices were placed within 0.94 ± 0.59 mm of the planned path. The use of a semi-automated surgical robot was feasible, providing a higher technical accuracy compared to non-robotic solutions. Paper V investigated the use of a tissue sensing technology, diffuse reflectance spectroscopy (DRS), for detecting the cortical bone boundary in vertebrae during pedicle screw insertions. The technology could accurately differentiate between cancellous and cortical bone and warn the surgeon before a cortical breach. Using machine learning models, the technology demonstrated a sensitivity of 98% [range: 94-100%] and a specificity of 98% [range: 91-100%]. In conclusion, several technological aids can be used to improve accuracy during spinal fixation procedures. In this thesis, the advantages of adding AR, VR, AI and tissue sensing technology to conventional navigation solutions were studied

Bud burst of birch in Finland and the United Kingdom - Logistic regression analysis and modeling

The day of bud burst (DBB) of different tree species are known to be affected by factors such as growing degree days and temperature. In this paper a two state Markov chain is used to model DBB for birch. The model is fit using logistic regression and LASSO regularization is used to evaluate which of many potential factors best forecast DBB. Data of birch from both Finland and the United Kingdom is studied and differences between the models adapted to the two countries are investigated. For modeling purposes to capture the environment of forecasting, estimated interpolated gridded climate data was used and not directly measured climate data. It is found that the models give very accurate predictions on the DBB. For Finland it is little more than 2 days in mean absolute error (MAE). The model is also fairly compact having less than 10 explaining covariates. The covariate, accumulated growing degree days, was as expected part of the models as well as among others variation of precipitation

Using Logistic Regression and Variable Selection to Model Time-To-Event Data:Applications to Tree Phenology and Graduation Time of Engineers

The day of bud burst (DBB) and leaf senescence are two examples of time-to-event phenological processes influenced by climate factors. Time to graduation or quitting for engineering students is another example of time-to-event data, with the added complication of having multiple possible outcomes, or absorbing states. This master thesis elaborates upon the models presented in Song (2010) "Stochastic Process Based Regression Modeling of Time-to-event Data". The time-to-event model is extended to use many different covariates, and Lasso regularization techniques are used for variable selection, resulting in compact and statistically relevant models. Models with multiple outcomes are shown to be able to perform classification of students sequentially over time. For the phenological examples, DBB is predicted with an accuracy of a couple of days while leaf senescence proves to be a harder problem, possibly in need of additional climate data not included in this analysis. Overall the model of Song is shown to have great promise and versatility for modeling of time-to-event data

Determinants of social inequalities in child mortality in Mozambique: What do we know? What could be done?*

Health inequalities are no longer an issue only for developed countries. In recent years there is agreement that all countries present health inequalities regardless of their level of wealth. In low-income countries and especially in sub-Saharan Africa where the majority of the poor people live as well as their children, research on child health inequalities is still scarce. This review of evidence suggests that if Mozambique is to achieve the millennium development goals (MDGs) by 2015 further research on important determinants of disparities in child mortality is urgently needed. African Journal of Health Sciences Vol. 13 (1-2) 2008: pp. 139-14

Delineation of thinning tracts at Holmen Skog : an evaluation of problems and possibilities

A common goal in practical forest management is to maximize the yield, measured in economical terms. When a forest stand is thinned a so called inoptimality loss can arise due to non-optimal decisions. This means that the selected management schedule results in a lower net present value than the optimal one which lowers the profitability for the forest owner. Holmen Skog uses the term tract which means an aggregation of stands made before a management action. A tract should be delineated in different tract parts in connection with pre-thinning planning if there is different bearing capacity within the tract, different thinning grades should be used or if the tract contains a weaker part that should not be thinned. If this delineation is neglected and a standardized forest management is practiced over a bigger thinning area, there is a risk of non-optimal decisions. Inaccurate estimation of forest variables in the pre-thinning planning, e.g. basal area, has also been a problem at Holmen Skog´s region Örnsköldsvik. There is also a fear that the volume production capacity is not fully used. The aim of this study was to examine the planning of tracts done at Holmen Skog as today and analyze the possible consequences of insufficient tract delineation. 53 tracts where inventoried with an objective plot survey and the differences between the estimated basal area and dominant height and the planners’ judgments of these values were calculated. An examination was also done of how often tracts were delineated by the planners through a search in Holmen Skog´s tract bank. This was followed by two analyzes in Heureka PlanWise to determine how much of the inoptimality loss that can be assigned to erroneous forest data respective insufficient tract delineation. Interviews were done with employees at Holmen Skog to look into the possibilities and difficulties with tract delineation. The results show that planners overestimated the basal area with 3,4 m2/ha on average while dominant height on average was underestimated with 1,8 m. The planners judgments were aggregated around the average basal area in a typical thinning stand and the overestimation can partly be explained by the fact that the planners did not exclude weaker parts from thinning in a sufficient way. The extent of tract delineation varied also a great deal between different districts at region Örnsköldsvik. The analyzes in PlanWise showed an inoptimality loss of just over 2 % because of erroneous forest data and about 1 % due to insufficient delineation of the tract. The interview respondents had in general a positive attitude to tract delineation since the work becomes easier for the machine drivers, especially if areas without need for thinning are excluded. They also thought that tract delineation for different thinning grade and thinning form is good as long as the map over the tract is intelligible. The possibility to in practice delineate a tract in parts is mostly dependent on how much time the planners have vacant for this. They work under time pressure since every district has to reach a minimum limit according to the estimated harvest level made at the head office.Holmen Skog använder begreppet traktindelning när en gallringstrakt delas efter skillnader i bärighet, gallringsuttag eller ifall svagare delar undantas från gallring. Om inte det bästa åtgärdsalternativet väljs inför gallring uppstår en förlust i nuvärde, en s.k. inoptimalförlust, Inoptimalförluster kan uppstå om föreslagna åtgärder baseras på en felaktigt skattade beståndsdata men även om samma skötsel tillämpas på ett större och heterogent område, d.v.s. vid bristande traktindelning. Syftet med detta arbete var att se hur traktplaneringar görs vid Holmen Skog och vilka konsekvenserna kan bli vid en bristande traktindelning. En objektiv fältinventering gjordes för 53 trakter följt av differensberäkningar mellan uppmätt grundyta och övre höjd respektive traktplanerarnas motsvarande värden. Omfattningen av traktindelning undersöktes genom att analysera traktbanken och analyser gjordes i Heureka för att beräkna inoptimalförluster p.g.a. felaktiga indata respektive bristande traktindelning. Intervjuer genomfördes för att undersöka anställdas syn på traktplanering men även möjligheter och svårigheter med traktindelning. Resultaten visar att traktplanerarna i snitt överskattade grundytan innan gallring med 3,4 m2/ha. En dragning mot mitten bland angivna värden i traktdirektiven var tydlig och överskattningen förklaras delvis av att traktplanerarna missat att exkludera sämre delar från trakten. Omfattningen av traktindelning varierade också mycket mellan olika distrikt på region Örnsköldsvik. Heureka-analyserna visade en inoptimalförlust på ca 2 % p.g.a. felaktiga indata och ca 1 % p.g.a. bristande traktindelning. Intervjurespondenterna var överlag positivt inställda till traktindelning då skogsskötseln kan varieras mer på en trakt samtidigt som maskinförarnas arbete underlättas. Möjligheten till traktindelning beror dock till stor del på traktplanerarnas arbetssituation eftersom de jobbar under tidspress

Incidence of Raynaud's phenomenon in relation to hand-arm vibration exposure among male workers at an engineering plant a cohort study

<p>Abstract</p> <p>Background</p> <p>The objective of this study was to assess the incidence of Raynaud's phenomenon in relation to hand-arm vibration exposure in a cohort consisting of male office and manual workers.</p> <p>Methods</p> <p>The baseline population consisted of 94 office and 147 manual workers at an engineering plant. Raynaud's phenomenon (RP) was assessed at baseline and at follow up (at 5, 10 and 15 years). A retrospective and a prospective cohort analysis of data were done. Hand-arm vibration exposure dose was defined as the product of exposure duration and the weighted hand-arm vibration exposure value according to ISO 5349-1.</p> <p>Results</p> <p>The retrospective/prospective incidence of Raynaud's phenomenon was 16/14 per 1000 exposure years among exposed and 2.4/5.0 per 1000 years among the not exposed. The retrospective dose response curve based on 4 dose classes showed that class 2, 3 and 4 had similar response and showed higher incidence than the not-exposed. The dose with RP response to hand-arm vibration corresponded to a 10 year A(8) value between 0.4–1.0 m/s².</p> <p>Conclusion</p> <p>The results indicate that the EU directive on an action value for hand-arm vibration of 2.5 m/s²is not too low. Rather, it suggests that employers should take on actions even at exposure values of 1 m/s²A(8).</p

Rätt gallringskvalitet med automatisk gallringsuppföljning

För att kunna kvalitetssäkra och garantera en bra utförd gallring är maskinförarnas egenuppföljning av stor vikt. Idag utförs den manuella uppföljningen ute i fält, vilket är tidsödande och sänker produktiviteten i avverkningsarbetet. För att kunna automatisera stora delar av denna uppföljning har Skogforsk tagit fram en programvara, hprGallring, där skördarföraren kan följa uppgifter om det kvarvarande beståndet direkt i maskinens dator. Huvudsyftet med denna studie var att undersöka om hprGallring leder till att förarna följer Norra Skogsägarnas gallringmallar bättre och därmed får en bättre kvalitet på gallringarna. En manuell referensmätning av 12 bestånd gjordes för att jämföra grundyteuttaget och andra beståndsvariabler med resultatet beräknat från hprGallring i skördaren. Resultaten från dessa bestånd jämfördes även med nio bestånd som manuellt följdes upp av praktikanter på Norra Skogsägarna under sommaren 2015, där maskinerna inte hade tillgång till hprGallring. Omfattningen av för hårt gallrade bestånd undersöktes därefter genom att analysera grundyteuttaget i Norra Skogsägarnas gallringsmallar för respektive bestånds ståndortsindex. En intervju genomfördes även med maskinförarna för att ta reda på vilka möjligheter och svårigheter som finns med automatisk gallringsuppföljning. Maskinförarna var överlag positivt inställda till programmet eftersom de menade att programmet medförde tidsbesparingar, mycket tack vare att de flesta beståndsvariablerna för det kvarvarande beståndet gick att följa direkt i maskinen. Resultatet visade att 25 % av de 12 gallrade bestånden med hprGallring var gallrade för hårt enligt gallringsmallen medan drygt hälften (56 %) av de 9 bestånd Norra Skogsägarna gjorde en manuell gallringsuppföljning på hade en grundyta som låg under den nedre begränsningslinjen. Slutsatserna som dras från denna studie är att med det nya programmet följer förarna Norra Skogsägarnas gallringsmallar bättre. Vidare tror jag att detta kommer att ersätta den manuella gallringsuppföljningen i stor utsträckning och att markägarnas skogsbruksplaner i framtiden kommer att kunna uppdateras automatiskt direkt efter utförd gallring.To ensure the quality of the thinning, and to guarantee a good own monitoring done by the machine operators are of vital importance. Today the manual monitoring is carried out in the field, which is time consuming and reduces productivity in harvesting work. In order to automate large parts of this, Skogforsk developed a software, hprGallring, where the harvester operator can follow the details of the remaining stand directly in the machine's computer. The main purpose of this study was to investigate whether hprGallring results in drivers follow the thinning templates for Norra Skogsägarna better and thus get a better quality of the thinning. A manual reference measurement of 12 stands was done to compare the basal are harvest and other stand variables with the results calculated from hprGallring in the harvester. The results of these stands were also compared with nine stands that were inventoried by the trainees at Norra Skogsägarna in the summer of 2015, and where the machines had not used hprGallring. The effect of too intensively thinned stands was then investigated by analyzing harvest based on basal area in thinning templates of Norra Skogsägarna for the site index for different stands. An interview was also conducted with the drivers to find out what opportunities and challenges available with the program. The drivers were generally positive about the program. They felt that the program resulted in time savings, thanks to the possibility to follow variables for the remaining stands directly in the machine. The results showed that 25 % of the 12 thinned stands with hprGallring was thinned too hard according to the thinning templates while just over half (56 %) of the 9 stocks that Norra Skogsägarna made a manual thinning follow-up had a basal area that was below the lower limit line. The conclusions from this study are that the drivers at Norra Skogsägarna follow the thinning templates better with the new program. Furthermore, I believe that this will replace the manual thinning follow-up to a large extent and that landowners forest management plans in the future will be updated automatically directly after performing the thinning

Transition from child healthcare to adult healthcare for adolescents with congenital heart disease

The life-prospects for adolescents with congenital heart disease (CHD) have improved, and today more than 90% survive to adulthood and need to continue their care into adulthood. During adolescence, the adolescents needs to step by step take over the responsibility for their care from their parents. This shift in responsibility seems to be difficult for both the adolescent and the parents. Many adolescents have described themselves as ill prepared for the transfer, and it has also been shown that adolescents often lack knowledge about their heart condition and the need for medical follow-up. Further, the parents might need support in how to hand over this responsibility to their child. The overall aim of this thesis was to examine the transition for adolescents with congenital heart disease and their parents prior to the transfer from pediatric health care to adult health care The thesis consists of four studies. The participants were adolescents 14–18 years old and their parents. The adolescents were under follow-up care at one of four university hospitals in Sweden: Gothenburg, Lund, Stockholm, and Umeå. The studies were based on individual interviews (I), focus group interviews (II), and questionnaires (III and IV). Study I. The aim was to identify and describe the needs of adolescents with CHD and their parents during the transition before transfer to adult cardiologic health care. The results revealed one theme for the adolescents, Safety and control, indicating a need for continuity and knowledge and a need of taking responsibility. The results also revealed one theme for the parents, Safety and trust, indicating a need for continuity and for shifting responsibility. Study II. The aim was to explore what adolescents with CHD view as important in the preparation for the transfer to adult care. The results revealed one main category, Becoming a manager of the condition, and the four subcategories of Sufficient knowledge about the health, Be a participant in the care, Parental support, and Communicate with others about the health. Study III. The aim was to (i) describe the level of readiness for transition in adolescents with CHD, (ii) to compare the level of readiness for transition as assessed by the adolescents with parental assessments, and (iii) to study potential correlates of transition readiness in adolescents with CHD. The results showed that the adolescents’ level of readiness for transition increased with age. Further, there was a significant difference in adolescents’ and their parents’ scoring, where the adolescents scored higher on overall readiness compared to their parents. Additional, empowerment and illness perception (patient’s overall perception about their disease) were associated with higher transition readiness. Study IV. The aims of the study were to (i) study parents’ levels of uncertainty related to the transfer from pediatric to adult care in adolescents with CHD and (ii) to identify any factors that might correlate with parents’ levels of uncertainty. The results showed that the mothers scored significantly higher on the uncertainty scale than the fathers and that there was a negative correlation between parental uncertainty and the adolescents’ overall readines