Habits Over Routines: Remarks on Control Room Practices and Control Room Studies

The evolution of computer tools has had profound impacts on many aspects of control rooms and control room studies. In this paper, we discuss some key assumptions underpinning these studies based on a new case of the electricity distribution control rooms, where the reliability of the electricity infrastructure is managed by a combination of planning and real-time maintenance. Some of these practices have changed remarkably little – partially because they have been considered to have been ‘digitalized’ since the 1950s and have continued to amass digital solutions from different periods. Hence, the gradual transformation of control room work demands nuanced attention, both conceptual and empirical. To outline a framework for this work, we provide a conceptualization of organizational routines, habits, and reflectivity and synthesize existing CSCW and control room literature. We then present an empirical study that demonstrates our concepts and shows how they can be applied to study cooperative work. By addressing these aims the paper complements, and advances, the important topics recognized in this special theme issue and hence develops new research openings in CSCW. We address the necessity to avoid implicit determinism when analyzing new digital support tools and suggest focusing on how working habits mediate social changes, distribution, and decentralization in representing the power distribution in control rooms

Bath concentration of anionic contrast agents does not affect their diffusion and distribution in articular cartilage in vitro

Objective: Differences in contrast agent diffusion reflect changes in composition and structure of articular cartilage. However, in clinical application the contrast agent concentration in the joint capsule varies, which may affect the reliability of contrast enhanced cartilage tomography (CECT). In the present study, effects of concentration of x-ray contrast agents on their diffusion and equilibrium distribution in cartilage were investigated. Design: Full-thickness cartilage discs (d = 4.0 mm, n = 120) were detached from bovine patellae (n = 24). The diffusion of various concentrations of ioxaglate (5, 10, 21, 50 mM) and iodide (30, 60, 126, 300 mM) was allowed only through the articular surface. Samples were imaged with a clinical peripheral quantitative computed tomography scanner before immersion in contrast agent, and after 1, 5, 9, 16, 25, and 29 hours in the bath. Results: Diffusion and partition coefficients were similar between different contrast agent concentrations. The diffusion coefficient of iodide (473 ± 133 μm2/s) was greater (P ≤ 0.001) than that of ioxaglate (92 ± 46 μm2/s). In full-thickness cartilage, the partition coefficient (at 29 h) of iodide (71 ± 5%) was greater (P ≤ 0.02 with most concentrations) than that of ioxaglate (62 ± 6%). Conclusions: Significant differences in partition and diffusion coefficient of two similarly charged (-1) contrast agents were detected, which shows the effect of steric interactions. However, the increase in solute concentration did not increase its partition coefficient. In clinical application, it is important that contrast agent concentration does not affect the interpretation of CECT imaging

Contrast agent-enhanced computed tomography of articular cartilage: Association with tissue composition and properties

Background: Contrast agent-enhanced computed tomography may enable the noninvasive quantification of glycosaminoglycan (GAG) content of articular cartilage. It has been reported that penetration of the negatively charged contrast agent ioxaglate (Hexabrix) increases significantly after enzymatic degradation of GAGs. However, it is not known whether spontaneous degradation of articular cartilage can be quantitatively detected with this technique. Purpose: To investigate the diagnostic potential of contrast agent-enhanced cartilage tomography (CECT) in quantification of GAG concentration in normal and spontaneously degenerated articular cartilage by means of clinical peripheral quantitative computed tomography (pQCT). Material and Methods: In this in vitro study, normal and spontaneously degenerated adult bovine cartilage (n=32) was used. Bovine patellar cartilage samples were immersed in 21 mM contrast agent (Hexabrix) solution for 24 hours at room temperature. After immersion, the samples were scanned with a clinical pQCT instrument. From pQCT images, the contrast agent concentration in superficial as well as in full-thickness cartilage was calculated. Histological and functional integrity of the samples was quantified with histochemical and mechanical reference measurements extracted from our earlier study. Results: Full diffusion of contrast agent into the deep cartilage was found to take over 8 hours. As compared to normal cartilage, a significant increase (11%, P0.05) in contrast agent concentration was seen in the superficial layer of spontaneously degenerated samples. Significant negative correlations were revealed between the contrast agent concentration and the superficial or full-thickness GAG content of tissue (|R|0.5, P0.01). Further, pQCT could be used to measure the thickness of patellar cartilage. Conclusion: The present results suggest that CECT can be used to diagnose proteoglycan depletion in spontaneously degenerated articular cartilage with a clinical pQCT scanner. Possibly, the in vivo use of clinical pQCT for CECT arthrography of human joints is feasible

Diffusion and near-equilibrium distribution of MRI and CT contrast agents in articular cartilage

Charged contrast agents have been used both in vitro and in vivo for estimation of the fixed charge density (FCD) in articular cartilage. In the present study, the effects of molecular size and charge on the diffusion and equilibrium distribution of several magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents were investigated. Full thickness cartilage disks ( = 4.0 mm, n = 64) were prepared from fresh bovine patellae. Contrast agent (gadopentetate: Magnevist, gadodiamide: Omniscan™, ioxaglate: Hexabrix™ or sodium iodide: NaI) diffusion was allowed either through the articular surface or through the deep cartilage. CT imaging of the samples was conducted before contrast agent administration and after 1, 5, 9, 16, 25 and 29 h (and with three samples after 2, 3, 4 and 5 days) diffusion using a clinical peripheral quantitative computed tomography (pQCT) instrument. With all contrast agents, the diffusion through the deep cartilage was slower when compared to the diffusion through the articular surface. With ioxaglate, gadopentetate and gadodiamide it took over 29 h for diffusion to reach the near-equilibrium state. The slow diffusion of the contrast agents raise concerns regarding the validity of techniques for FCD estimation, as these contrast agents may not reach the equilibrium state that is assumed. However, since cartilage composition, i.e. deep versus superficial, had a significant effect on diffusion, imaging of the nonequilibrium diffusion process might enable more accurate assessment of cartilage integrity

CT arthrography of the human knee to measure cartilage quality with low radiation dose

SummaryObjectiveRecently, CT arthrography (CTa) was introduced as a non-destructive technique to quantitatively measure cartilage quality in human knees. This study investigated whether this is also possible using lower radiation dose CT protocols. Furthermore, we studied the ability of (lower radiation) CTa to distinguish between local sulphated glycosaminoglycan (sGAG) content differences.DesignOf ten human cadaveric knee joints, six CT scans using different radiation doses (81.33–8.13 mGy) were acquired after intra-articular ioxaglate injection. The capability of CTa to measure overall cartilage quality was determined in seven anatomical regions of interest (ROIs), using equilibrium partitioning of an ionic contrast agent using (EPIC)-microCT (μCT) as reference standard for sGAG content. To test the capability of CTa to spatially distinguish between local differences in sGAG content, we calculated the percentage of pixels incorrectly predicted as having high or low sGAG content by the different CTa protocols.ResultsLow radiation dose CTa correlated well with EPIC-μCT in large ROIs (R = 0.78; R2 = 0.61; P < 0.0001). CTa can also distinguish between high and low sGAG content within a single slice. However, the percentage of incorrectly predicted quality pixels increases (from 35% to 41%) when less radiation is used. This makes is hard or even impossible to differentiate between spatial differences in sGAG content in the lowest radiation scans.ConclusionsCTa acquired using low radiation exposure, comparable to a regular knee CT, is able to measure overall cartilage quality. Spatial sGAG distribution can also be determined using CTa, however for this purpose a higher radiation dose is necessary. Nevertheless, radiation dose reduction makes CTa suitable for quantitative analysis of cartilage in clinical research

Effects of irradiation in the mandibular bone loaded with dental implants. An experimental study with a canine model

Radiation therapy may compromise the quality of bone around dental implants, and its ability to regenerate, remodel, and revascularize. This study aimed to describe the irradiation effect on the bone microstructure of the mandible using dental implants in a canine model. Five beagle dogs were exposed to 40 Gy fractionated radiation. In total, 20 dental implants were inserted, two in the irradiated and two in the non-irradiated side. The mandible bone blocks were subjected to 3D micro-computed tomography (µCT) imaging, later evaluated histomorphometrically by light microscopy and scanning electron microscopy. Alterations in irradiated bone were observed under µCT imaging showing an increased anisotropy, porosity, and pore volume. Bone surface-to-bone volume decreased. The bone to implant contact index was significantly reduced in the irradiated bone (75.6% ± 5.8%) as compared to the non-irradiated bone (85.1% ± 6.8%). In the irradiated mandible, osteocytes with their filopodial processes, the bone beneath the periosteum, and subperiosteal veins showed structural differences but were not significant, whereas the diameter of Haversian canals were smaller statistical significant as compared to the control side. The study highlights that radiation dosage of fractioned 40 Gy causes alterations in the alveolar bone microstructure with compatible osseointegration and clinically stable dental implants