7 research outputs found
Evaluation of MRI-only based online adaptive radiotherapy of abdominal region on MR-linac
Purpose A hybrid magnetic resonance linear accelerator (MRL) can perform magnetic resonance imaging (MRI) with high soft-tissue contrast to be used for online adaptive radiotherapy (oART). To obtain electron densities needed for the oART dose calculation, a computed tomography (CT) is often deformably registered to MRI. Our aim was to evaluate an MRI-only based synthetic CT (sCT) generation as an alternative to the deformed CT (dCT)-based oART in the abdominal region. Methods The study data consisted of 57 patients who were treated on a 0.35 T MRL system mainly for abdominal tumors. Simulation MRI-CT pairs of 43 patients were used for training and validation of a prototype convolutional neural network sCT-generation algorithm, based on HighRes3DNet, for the abdominal region. For remaining test patients, sCT images were produced from simulation MRIs and daily MRIs. The dCT-based plans were re-calculated on sCT with identical calculation parameters. The sCT and dCT were compared in terms of geometric agreement and calculated dose. Results The mean and one standard deviation of the geometric agreement metrics over dCT-sCT-pairs were: mean error of 8 +/- 10 HU, mean absolute error of 49 +/- 10 HU, and Dice similarity coefficient of 55 +/- 12%, 60 +/- 5%, and 82 +/- 15% for bone, fat, and lung tissues, respectively. The dose differences between the sCT and dCT-based dose for planning target volumes were 0.5 +/- 0.9%, 0.6 +/- 0.8%, and 0.5 +/- 0.8% at D-2%, D-50%, and D-98% in physical dose and 0.8 +/- 1.4%, 0.8 +/- 1.2%, and 0.6 +/- 1.1% in biologically effective dose (BED). For organs-at-risk, the dose differences of all evaluated dose-volume histogram points were within [-4.5%, 7.8%] and [-1.1 Gy, 3.5 Gy] in both physical dose and BED. Conclusions The geometric agreement metrics were within typically reported values and most average relative dose differences were within 1%. Thus, an MRI-only sCT-based approach is a promising alternative to the current clinical practice of the abdominal oART on MRL.Peer reviewe
An expression analysis of markers of radiation-induced skin fibrosis and angiogenesis in wound healing disorders of the head and neck
Miljöbeslut vid tillstÄndsprövning : Natura 2000 och rÀtten till en rÀttvis rÀttegÄng
Miljöbeslut vid tillstÄndsprövning : Natura 2000 och rÀtten till en rÀttvis rÀttegÄng
Miljöbeslut vid tillstÄndsprövning : Natura 2000 och rÀtten till en rÀttvis rÀttegÄng
Tuotantoprosessin kustannusten mallintaminen ja laskentainformaation hyödyntÀminen prosessin kehityksessÀ
Modelling the costs of a production process is a management accounting tool, which provides essential information for leading a company.
This study examines the subject both from theoretical perspective and on the other hand from practical point of view with a field study in a Finnish service company.
The approach of this research is objective aimed accounting, which means that the needed information is defined first and then the accounting process is performed guided by the information need.
The field study goes particularly deep into accounting that supports process development.
The information needed to develop the process is formed by modelling the total costs of the service production process by dividing the process into activities.
The environment of a company and the accounting condition are the main factors that affect the cost accounting.
The type of the company, the type of the production process and the size and structure of the organisation are the company dependent factors that set demands on accounting.
The accounting condition is mainly defined by the objective of the cost accounting.
The objective thus determines the type of costs used in accounting process, the time horizon of the analysis, the accuracy of the calculations and the way to value resources.
The performed field study created a model that describes the structure of the production process costs.
On the other hand it outlined the development ideas about performing the activities and resource utilization.
In addition, the field study showed the possibilities and the costs of the renewed accounting to the company management.
This information makes it possible to evaluate the benefits of implementing the new accounting model and to deliberate the chance to extend the usage of the model to the entire company.
The most essential development concepts relate to rationalizing the resource usage throughout the production process.
Service production causes the workload to distribute unevenly both in regard to resources and time.
Managing this distribution by planning more efficiently, directing selling and improving the activities of production resources provides an opportunity to substantially lower the total cost of the enveloping production process.Tuotantoprosessin kustannusten mallintaminen on johdon laskentatoimeen kuuluva keino hankkia yrityksen johtamisen kannalta oleellista informaatiota.
TÀssÀ tutkimuksessa perehdytÀÀn kyseiseen aiheeseen toisaalta teoreettisesta nÀkökulmasta sekÀ toisaalta suorittamalla tapaustutkimus suomalaisessa palvelutuotantoyrityksessÀ.
Tutkimus korostaa tavoiteohjautuvaa laskentaa, jossa mÀÀritellÀÀn laskennasta haluttava informaatio sekÀ suoritetaan laskentaprosessi tÀmÀn informaatiotarpeen ohjaamana.
Tavoiteohjautuvuus ilmenee tutkimuksessa perehtymisenÀ erityisesti prosessin kehitystÀ tukevaan laskentaan.
KehitystÀ tukevaa informaatiota muodostetaan mallintamalla palvelutuotantoprosessin kokonaiskustannukset yksittÀisten työsuoritusten eli toimintojen kautta.
YritysympÀristö ja laskentatilanne asettavat suoritettavalle laskennalle reunaehtoja.
YritysympÀristön kannalta tuotantotyyppi, valmistusprosessi, organisaation koko ja rakenne mÀÀrittÀvÀt tilanteeseen soveltuvat laskentatavat.
Tavoitteesta riippuvainen laskentatilanne puolestaan mÀÀrittÀÀ laskentaan soveltuvat kustannukset, tarkastelun aikahorisontin, laskennan tarkkuuden sekÀ tavat arvostaa resursseja.
Suoritettu tapaustutkimus muodosti sekÀ mallin, joka kuvaa kuoritusprosessin kustannusten muodostumista ettÀ hahmotteli niin toimintojen tehostamiseen kuin resurssien kÀyttöön liittyvien keskeisimpien kehitysajatusten sisÀllön.
LisÀksi tapaustutkimus pilottiluonteisuudessaan osoitti yritysjohdolle uudistetun laskennan mahdollisuudet, eroavaisuudet verrattuna nykyiseen laskentaan sekÀ kustannukset, joiden perusteella yritysjohto voi suorittaa arvioinnin laskentamenettelyn kÀyttöönotosta sekÀ mahdollisen laajentamisen kannattavuudesta koko yritykseen.
KeskeisimmÀt kehitysajatukset liittyvÀt resurssien kÀytön tehostamiseen lÀpi tuotantoprosessin.
Palvelutuotanto aiheuttaa työkuorman epÀtasaisen jakautumisen niin resurssien kuin ajankin suhteessa.
TÀmÀn jakauman hallinta suunnittelua tehostamalla, myyntiÀ ohjaamalla sekÀ tuotantoresurssien toimintaa parantamalla tarjoaa mahdollisuuden alentaa kuorituksen palvelutuotantoprosessin kokonaiskustannuksia merkittÀvÀsti