Rajoitteilla ohjattu gradienttivahvistus-menetelmä

Tiivistelmä. Tutkielmassa tarkastellaan tekoälyyn rinnastettavien mallintamismenetelmien — valintapuiden — toimintaa vertaamalla asiantuntijoiden tietoa hyödyntävän valintapuun ja tavanomaisen valintapuun tarkkuutta toisiinsa. Lisäksi tutkielmassa käsitellään valintapuihin liitettyä mallintamisen tarkkuutta parantavaa algoritmia, joka perustuu jyrkimmän laskun menetelmään. Tavoitteena tutkielmassa on selvittää mainittujen valintapuiden toimivuutta terästen kristallisoitumislämpötilojen ennustamisessa. Tavanomainen valintapuun toiminta perustuu puun ennustamien arvojen virheiden minimoimiseen käyttämällä virheen muodostamaa funktiota. Valintapuut koulutetaan ennustamaan mahdollisimman oikeita arvoja mallintamisen kohteena olevasta systeemistä kerätyn datan avulla. Valintapuiden muokattavuuden johdosta niiden mallintamisen tarkkuutta voidaan parantaa yhdistämällä niihin erilaisia tehostamisalgoritmeja. Tutkielmassa tarkasteltava asiantuntijan tietoon pohjautuva valintapuumenetelmä perustuu virheen minimoimisen lisäksi asiantuntijan tiedosta muodostettuihin rajoitteisiin, jotka ohjaavat puuta rakentumaan haluttuun suuntaan toimimalla ylimääräisenä sakkona, joka lisätään virheeseen silloin kun puu ei noudata annettua rajoitetta. Mallinnettaessa kristallisoitumislämpötiloja käytetyn aineiston avulla, ei tuloksissa havaittu merkittävää eroa eri menetelmien kesken. Asiantuntijatiedon saatavuus työtä tehden oli kuitenkin rajoitettu, joten algoritmia ohjaavien rajoitteiden muodostaminen oli epävarmaa. Valintapuut ovat toimiva mallintamisen menetelmä kyseisen aineiston kohdalla johtuen aineiston monipuolisuudesta ja laajuudesta. Jatkoa ajatellen tutkielma antaa hyvän pohjan sekä toisenlaisten valintapuumenetelmien vertailuun, että entistä parempien menetelmien ja algoritmien löytämiseen

Early and late outcomes after open ascending aortic surgery: 47-year experience in a single centre

The aims of the study are to describe the long-term survival of patients undergoing primary open ascending aortic surgery and to portray the evolution of aortic surgery during six decades in a single centre. Included were all 614 patients who underwent primary ascending aortic surgery in 1968–2014 at one Nordic university hospital. Patients were identified and data were collected from patient records and surgical logs. Mortality data were acquired from the national registry. Median follow-up was 11.2 years using reverse Kaplan–Meier method. Overall 30-day survival was 91.2% and for 30-day survivor rates were 86.9, 77.6, 52.1, 38.3 and 26.7% at 5, 10, 20, 30 and 40 years. There was no significant difference in long-term survival for 30-day survivors (p = 0.105) between patients treated emergently for dissection/rupture and electively (mainly ascending aortic aneurysms). On Cox regression era of surgery (p = 0.006), increasing age (p < 0.001) and indication (p < 0.001) were predictors of 30-day mortality. Arch involvement indicated twofold risk (HR 2.09, p = 0.05) compared to non-arch involved. Only increasing age (p < 0.001) predicted long-term mortality. There was a sixfold risk of 30-day mortality in the earliest era compared to the latest (p = 0.03). After the early postoperative phase following ascending aortic surgery, the surgical indication and urgency of the index operation have no significant impact on long-term survival. The very long term survival after ascending aortic surgery is excellent for 30-day survivors and improved through the era. Surgical treatment has improved and perioperative mortality has decreased significantly in 47 years

Accuracy of echocardiographic area-length method in chronic myocardial infarction: comparison with cardiac CT in pigs

Background: We evaluated echocardiographic area-length methods to measure left ventricle (LV) volumes and ejection fraction (EF) in parasternal short axis views in comparison with cardiac computed tomography (CT) in pigs with chronic myocardial infarction (MI).Methods: Male farm pigs with surgical occlusion of the left anterior descending coronary artery (n = 9) or sham operation (n = 5) had transthoracic echocardiography and cardiac-CT 3 months after surgery. We measured length of the LV in parasternal long axis view, and both systolic and diastolic LV areas in parasternal short axis views at the level of mitral valve, papillary muscles and apex. Volumes and EF of the LV were calculated using Simpson's method of discs (tri-plane area) or Cylinder-hemiellipsoid method (single plane area).Results: The pigs with coronary occlusion had anterior MI scars and reduced EF (average EF 42 +/- 10%) by CT. Measurements of LV volumes and EF were reproducible by echocardiography. Compared with CT, end-diastolic volume (EDV) measured by echocardiography showed good correlation and agreement using either Simpson's method (r = 0.90; mean difference -2, 95% CI -47 to 43 mL) or Cylinder-hemiellipsoid method (r = 0.94; mean difference 3, 95% CI -44 to 49 mL). Furthermore, End-systolic volume (ESV) measured by echocardiography showed also good correlation and agreement using either Simpson's method (r = 0.94; mean difference 12 ml, 95% CI: -16 to 40) or Cylinder-hemiellipsoid method (r = 0.97; mean difference: 13 ml, 95% CI: -8 to 33). EF was underestimated using either Simpson's method (r = 0.78; mean difference -6, 95% CI -11 to 1%) or Cylinder-hemiellipsoid method (r = 0.74; mean difference -4, 95% CI-10 to 2%).Conclusion: Our results indicate that measurement of LV volumes may be accurate, but EF is underestimated using either three or single parasternal short axis planes by echocardiography in a large animal model of chronic MI

Imaging of αvβ3 integrin expression in experimental myocardial ischemia with [68Ga]NODAGA-RGD positron emission tomography

BACKGROUND: Radiolabeled RGD peptides detect αvβ3 integrin expression associated with angiogenesis and extracellular matrix remodeling after myocardial infarction. We studied whether cardiac positron emission tomography (PET) with [68Ga]NODAGA-RGD detects increased αvβ3 integrin expression after induction of flow-limiting coronary stenosis in pigs, and whether αvβ3 integrin is expressed in viable ischemic or injured myocardium.METHODS: We studied 8 Finnish landrace pigs 13 ± 4 days after percutaneous implantation of a bottleneck stent in the proximal left anterior descending coronary artery. Antithrombotic therapy was used to prevent stent occlusion. Myocardial uptake of [68Ga]NODAGA-RGD (290 ± 31 MBq) was evaluated by a 62 min dynamic PET scan. The ischemic area was defined as the regional perfusion abnormality during adenosine-induced stress by [15O]water PET. Guided by triphenyltetrazolium chloride staining, tissue samples from viable and injured myocardial areas were obtained for autoradiography and histology.RESULTS: Stent implantation resulted in a partly reversible myocardial perfusion abnormality. Compared with remote myocardium, [68Ga]NODAGA-RGD PET showed increased tracer uptake in the ischemic area (ischemic-to-remote ratio 1.3 ± 0.20, p = 0.0034). Tissue samples from the injured areas, but not from the viable ischemic areas, showed higher [68Ga]NODAGA-RGD uptake than the remote non-ischemic myocardium. Uptake of [68Ga]NODAGA-RGD correlated with immunohistochemical detection of αvβ3 integrin that was expressed in the injured myocardial areas.CONCLUSIONS: Cardiac [68Ga]NODAGA-RGD PET demonstrates increased myocardial αvβ3 integrin expression after induction of flow-limiting coronary stenosis in pigs. Localization of [68Ga]NODAGA-RGD uptake indicates that it reflects αvβ3 integrin expression associated with repair of recent myocardial injury.</p

Systemic Dosing of Thymosin Beta 4 before and after Ischemia Does Not Attenuate Global Myocardial Ischemia-Reperfusion Injury in Pigs

The use of cardiopulmonary bypass (CPB) and aortic cross-clamping causes myocardial ischemia-reperfusion injury (I-RI) and can lead to reduced postoperative cardiac function. We investigated whether this injury could be attenuated by thymosin beta 4 (TB4), a peptide which has showed cardioprotective effects. Pigs received either TB4 or vehicle and underwent CPB and aortic cross-clamping for 60 min with cold intermittent blood-cardioplegia and were then followed for 30 h. Myocardial function and blood flow was studied by cardiac magnetic resonance and PET imaging. Tissue and plasma samples were analyzed to determine the amount of cardiomyocyte necrosis and apoptosis as well as pharmacokinetics of the peptide. In vitro studies were performed to assess its influence on blood coagulation and vasomotor tone. Serum levels of the peptide were increased after administration compared to control samples. TB4 did not decrease the amount of cell death. Cardiac function and global myocardial blood flow was similar between the study groups. At high doses a vasoconstrictor effect on mesentery arteries and a vasodilator effect on coronary arteries was observed and blood clot firmness was reduced when tested in the presence of an antiplatelet agent. Despite promising results in previous trials the cardioprotective effect of TB4 was not demonstrated in this model for global myocardial I-RI

Viiveen optimointi lisätyn todellisuuden sovelluksessa

Lisätyn todellisuuden sovellukset suorittavat konenäön ja kuvankäsittelyn tehtäviä, joita voidaan toteuttaa eri menetelmillä ja vaihtelevalla tehokkuudella. Tämä dokumentti esittää tehokkuusvertailun lisätyn todellisuuden ilmakiekkopelin kautta. Vertailu keskittyy pääkohtien tunnistimiin ja piirteiden kuvaajiin niiden ollessa merkittävin muokattava tekijä pelissä. Pääkohtien tunnistimista testattiin ORB-, MSER-, FAST-, BRISK-, SIFT- ja SURF-algoritmeja ja piirteiden kuvaajista testattiin ORB-, BRISK-, BRIEF-, FREAK-, SIFT- ja SURF-algoritmeja. Testi suoritettiin ilmakiekkopelissä nauhoitetulle videolle, jossa ympäristö vastasi lisätyn todellisuuden pelin normaalia peliympäristöä. ORB-algoritmia pidetään parhaana vaihtoehtona tehokkuutta vaativiin sovelluksiin ja SIFT-algoritmia pidetään parhaana tarkkuutta vaativiin sovelluksiin. Myös testitulokset osoittavat ORB-algoritmin olevan paras vaihtoehto tämän työn tavoitteena olleessa ilmakiekkopelissä.Augmented reality applications require computer vision and image processing functions that can be implemented using different methods and with varying degrees of efficiency. This document presents a comparison of the efficiency with the air hockey game. The comparison focuses on keypoint detectors and feature descriptors as they are the most important factor in the game that can be changed. We tested ORB, MSER, FAST, BRISK, SIFT and SURF algorithms from all keypoint detectors and ORB, BRISK, BRIEF, FREAK, SIFT and SURF algorithms from all feature descriptors. The test was carried out with a recorded video from the air hockey game, that corresponded to the normal game environment of an augmented reality game. The ORB algorithm is considered to be the best option for demanding applications and the SIFT algorithm is considered to be the best option in precision applications. Also, the test results show that the ORB algorithm is the best option in the air-hockey game that was one objective of this work