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

Tuotantoprosessin kustannusten mallintaminen ja laskentainformaation hyödyntäminen prosessin kehityksessä

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. Tässä tutkimuksessa perehdytään kyseiseen aiheeseen toisaalta teoreettisesta näkökulmasta sekä toisaalta suorittamalla tapaustutkimus suomalaisessa palvelutuotantoyrityksessä. Tutkimus korostaa tavoiteohjautuvaa laskentaa, jossa määritellään laskennasta haluttava informaatio sekä suoritetaan laskentaprosessi tämän informaatiotarpeen ohjaamana. Tavoiteohjautuvuus ilmenee tutkimuksessa perehtymisenä erityisesti prosessin kehitystä tukevaan laskentaan. Kehitystä tukevaa informaatiota muodostetaan mallintamalla palvelutuotantoprosessin kokonaiskustannukset yksittäisten työsuoritusten eli toimintojen kautta. Yritysympäristö ja laskentatilanne asettavat suoritettavalle laskennalle reunaehtoja. Yritysympäristön kannalta tuotantotyyppi, valmistusprosessi, organisaation koko ja rakenne määrittävät tilanteeseen soveltuvat laskentatavat. Tavoitteesta riippuvainen laskentatilanne puolestaan määrittää laskentaan soveltuvat kustannukset, tarkastelun aikahorisontin, laskennan tarkkuuden sekä tavat arvostaa resursseja. Suoritettu tapaustutkimus muodosti sekä mallin, joka kuvaa kuoritusprosessin kustannusten muodostumista että hahmotteli niin toimintojen tehostamiseen kuin resurssien käyttöön liittyvien keskeisimpien kehitysajatusten sisällön. Lisäksi tapaustutkimus pilottiluonteisuudessaan osoitti yritysjohdolle uudistetun laskennan mahdollisuudet, eroavaisuudet verrattuna nykyiseen laskentaan sekä kustannukset, joiden perusteella yritysjohto voi suorittaa arvioinnin laskentamenettelyn käyttöönotosta sekä mahdollisen laajentamisen kannattavuudesta koko yritykseen. Keskeisimmät kehitysajatukset liittyvät resurssien käytön tehostamiseen läpi tuotantoprosessin. Palvelutuotanto aiheuttaa työkuorman epätasaisen jakautumisen niin resurssien kuin ajankin suhteessa. Tämän jakauman hallinta suunnittelua tehostamalla, myyntiä ohjaamalla sekä tuotantoresurssien toimintaa parantamalla tarjoaa mahdollisuuden alentaa kuorituksen palvelutuotantoprosessin kokonaiskustannuksia merkittävästi