Synkrotronisäteilyyn perustuva funktionaalinen keuhkokuvantaminen

Functional lung CT using synchrotron radiation was applied for studying regional ventilation distribution in vivo in animal lungs. This quantitative method employs the K-edge subtraction (KES) technique, which takes advantage of the sharp rise of the absorption coefficient at the binding energy of K-shell electron of a contrast agent. In KES technique two images are taken simultaneously at energies bracketing the K-edge energy of stable xenon (Xe) gas. This technique produces absorption CT images for structural evaluation and Xe density images and at the same time it allows the study of the regional ventilation heterogeneity, calculated based on wash-in series of Xe inhalation images. In this work the analysis of KES CT images was developed to show the regional differences in the airway reactions produced by the direct constrictor agonist, methacholine (MCh), and the indirect constrictor agonist, ovalbumin (OVA), in healthy and asthmatic rabbits. Moreover these constrictors were tested under the influence of cigarette smoke. The effect in airways of different administration routes of MCh, inhaled or intravenous (i.v.), was studied using low radiation dose Xe density CT images. The radiation dose in synchrotron radiation imaging of rabbit lungs in vivo, with and without Xe, was calculated and measured using several methods and compared to the image quality. Results showed that i.v. MCh caused bronchoconstriction primarily in central airways in healthy and asthmatic animals, whereas i.v. OVA only in asthmatic animals. Inhaled MCh, in both groups, affected more the periphery. On the other hand cigarette smoke inhibited the bronchoconstriction in both healthy and asthmatic animals. Theoretical and measured values of synchrotron radiation dose were consistent in this setup. Dose dependency of the image quality, defined by signal to noise ratio, was evaluated, and a threshold for detectable signal contrast was found. The optimal imaging setup was estimated using these results. These findings show the feasibility of the KES CT method for functional lung imaging of airway reactions by providing information on the regional ventilation distributions. By optimizing the image acquisition and reconstruction algorithms with existing methods, KES CT lung imaging could be adaptable for human studies in the near future.Astma on yleinen sairaus teollisissa maissa ja Suomessa siihen sairastuu noin 9 % väestöstä. Astmassa keuhkojen alueellinen toiminta on häiriintynyttä. Perinteisesti keuhkojen toimintaa on tutkittu spirometrialla tai radionuklidimenetelmillä, joiden erotuskyky tai kvantitatiivisuus eivät ole riittäviä paikantamaan keuhkojen ääreisosien toimintaa tai rakennetta. Keuhkojen toimintaa voidaan tutkia aiempaa tarkemmin synkrotronilla tuotettuun röntgensäteilyyn perustuvalla funktionaalisella tietokonetomografialla (TT), joka perustuu kontrastiaineen, xenonin, K-reunan vähennystekniikkaan (KES). Tekniikalla voidaan tuottaa samanaikaisesti sekä perinteisiä TT-kuvia keuhkorakenteen tutkimiseen että xenonin tiheyskuvia, joista saadaan kvantitatiivista tietoa kuten absoluuttisia tiheyksiä tai hengityskuvia paikallisen keuhkotuuletuksen määrittämiseen. Väitöskirjatyössä KES-TT analyysiä kehitettiin määrittämään keuhkojen toiminnan paikallisia muutoksia astmankaltaisessa tai allergeenin aiheuttamassa reaktiossa terveillä ja astmaattisilla kaneilla. Myös tupakansavun vaikutusta näihin reaktioihin testattiin. Lisäksi tutkittiin suonensisäisesti annetun tai hengitetyn astmareaktiota aiheuttavan lääkkeen vaikutuksen eroa keuhkojen toimintaan. Kuvauksessa käytetyn synkrotronisäteilyn annos määritettiin sekä teoreettisesti että mittaamalla. Säteilyannoksen ja kuvanlaadun keskinäistä riippuvuutta tutkittiin. Löydösten perusteella KES-TT menetelmän avulla voidaan tutkia sekä funktionaalisesti keuhkojen tuuletuksen jakautumista ja sen muutoksia paikallisesti että saada tietoa keuhkojen anatomiasta. Kehittämällä laitteistoa ja optimoimalla rekonstruktioalgoritmit on mahdollista soveltaa KES-TT tekniikkaa myös ihmiskeuhkojen kuvaukseen

Tahdistinpotilaan sädehoito

English summar

Contemporary radiation doses in interventional cardiology: a nationwide study of patient doses in Finland

The amount of interventional procedures such as percutaneous coronary intervention (PCI), transcatheter aortic valve implantation (TAVI), pacemaker implantation (PI) and ablations has increased within the previous decade. Simultaneously, novel fluoroscopy mainframes enable lower radiation doses for patients and operators. Therefore, there is a need to update the existing diagnostic reference levels (DRLs) and propose new ones for common or recently introduced procedures. We sought to assess patient radiation doses in interventional cardiology in a large sample from seven hospitals across Finland between 2014 and 2016. Data were used to set updated national DRLs for coronary angiographies (kerma-air product (KAP) 30 Gycm2) and PCIs (KAP 75 cm2), and novel levels for PIs (KAP 3.5 Gycm2), atrial fibrillation ablation procedures (KAP 25 Gycm2) and TAVI (KAP 90 Gycm2). Tentative KAP values were set for implantations of cardiac resynchronization therapy devices (CRT, KAP 22 Gycm2), electrophysiological treatment of atrioventricular nodal re-entry tachycardia (6 Gycm2) and atrial flutter procedures (KAP 16 Gycm2). The values for TAVI and CRT device implantation are published for the first time on national level. Dose from image acquisition (cine) constitutes the major part of the total dose in coronary and atrial fibrillation ablation procedures. For TAVI, patient weight is a good predictor of patient dose.</p

Palliative intensity modulated radiotherapy of bone metastases based on diagnostic instead of planning computed tomography scans

Background and purpose: Radiotherapy (RT) treatment planning is as a standard based on a computed tomography (CT) scan obtained at the planning stage (pCT), while most of the decisions whether to treat by RT are based on diagnostic CT scans (dCT). Bone metastases (BM) are the most common palliative RT target. The objective of this study was to investigate if a palliative RT treatment plan of BMs could be made based on a dCT with sufficient accuracy and safety, without sacrificing any treatment quality. Materials and methods: A retrospective study with 60 BMs of 8 anatomical sites was performed. RT planning was performed using intensity-modulated radiation therapy/volumetric modulated arc therapy techniques in dCT and transferred to pCT. The dose of clinical target volumes (CTVs), D(CTVV95%, V50%), were compared between plans for dCT and pCT. Patient setup was investigated in cone-beam CT scans. Results: The differences of D(CTVV95%, V50%) between dCT and pCT plans were the lowest in the pelvis (1.2%, 1.3%), lumbar spine (1.3%, 1.4%) and thoracic spine (1.3%, 2.1%), while the differences were higher in cervical spine (3.7%, 3.1%), long bones (2.3%, 1.5%), and costae (1.9%, 1.8%). The patient set-up was acceptable for 100% of the pelvic and lumbar, for 92% of thoracic spine cases, and for <80% of cases in other sites. Conclusion: This study showed the feasibility of using dCT images in palliative RT planning of BMs in thoracic, lumbar spine and pelvic sites, indicating the potential suitability of this strategy for clinical use

Performance of ESD protective materials at low relative humidity

We have studied the surface resistivity and charge decay times of different kinds of electrostatic discharge (ESD) protective materials as a function of relative humidity. The measurements have been done in the humidity range of 5–70% RH. The studied materials are frequently used in personnel and process protection and in packaging. Both surface resistivity and charge decay measurements are required to obtain reliable information on the performance of the materials in ESD control. According to the results, a great care should be done in the ESD management if conditions below 20–30% RH are anticipated. In such conditions some ESD protective materials may become insulators

Effect of positive end-expiratory pressure on regional ventilation distribution during mechanical ventilation after surfactant depletion

Ventilator-induced lung injury occurs due to exaggerated local stresses, repeated collapse, and opening of terminal air spaces in poorly aerated dependent lung, and increased stretch in nondependent lung. The aim of this study was to quantify the functional behavior of peripheral lung units in whole-lung lavage-induced surfactant depletion, and to assess the effect of positive end-expiratory pressure

Effect of surfactant on regional lung function in an experimental model of respiratory distress syndrome in rabbit

We assessed the changes in regional lung function following instillation of surfactant in a model of respiratory distress syndrome (RDS) induced by whole lung lavage and mechanical ventilation, in 8 anaesthetized, paralyzed, and mechanically ventilated New-Zealand White rabbits. Regional specific ventilation (sV· ) was measured using K-edge subtraction synchrotron CT imaging during xenon washin. Lung regions were classified as poorly-aerated (PA), normally aerated (NA) or hyperinflated (HI) based on regional density. A functional category was defined within each class, based on sV· distribution (High, Normal, and Low). Airway resistance (Raw), respiratory tissue damping (G) and elastance (H) were measured by forced oscillation technique (FOT) at low frequencies before and after whole lung saline lavage-induced (100 ml/kg) RDS, and 5 and 45 minutes after intratracheal instillation of beractant (75 mg/kg). Surfactant instillation improved Raw, G and H (p<0.05, respectively) and gas exchange and decreased atelectasis (p<0.001). It also significantly improved lung aeration and ventilation in atelectatic lung regions. However, in regions that had remained normally-aerated after lavage, it decreased regional aeration and increased sV· (p<0.001) and sV· heterogeneity. Although surfactant treatment improved both central airway and tissue mechanics and improved regional lung function of initially poorly-aerated and atelectatic lung, it deteriorated regional lung function when local aeration was normal prior to administration. Local mechanical and functional heterogeneity can potentially contribute to the worsening of RDS, and gas exchange. These data underscore the need for reassessing the benefits of routine prophylactic vs. CPAP and early "rescue" surfactant therapy in very immature infants

Pressure-regulated volume control vs. volume control ventilation in healthy and injured rabbit lung: An experimental study

It is not well understood how different ventilation modes affect the regional distribution of ventilation, particularly within the injured lung

Imaging of lung function using synchrotron radiation computed tomography: what's new?

There is a growing interest in imaging techniques as non-invasive means of quantitatively measuring regional lung structure and function. Abnormalities in lung ventilation due to alterations in airway function such as those observed in asthma and COPD are highly heterogeneous, and experimental methods to study this heterogeneity are crucial for better understanding of disease mechanisms and drug targeting strategies. In severe obstructive diseases requiring mechanical ventilation, the optimal ventilatory strategy to achieve recruitment of poorly ventilated lung zones remains a matter of considerable debate. We have used synchrotron radiation computed tomography (SRCT) for the in vivo study of regional lung ventilation and airway function. This imaging technique allows direct quantification of stable Xenon (Xe) gas used as an inhaled contrast agent using K-edge subtraction imaging. Dynamics of Xe wash-in can be used to calculate quantitative maps of regional specific lung ventilation. More recently, the development of Spiral-CT has allowed the acquisition of 3D images of the pulmonary bronchial tree and airspaces. This technique gives access to quantitative measurements of regional lung volume, ventilation, and mechanical properties. Examples of application in an experimental model of allergic asthma and in imaging lung recruitment as a function of mechanical ventilation parameters will be presented. The future orientations of this technique will be discussed