Mobile Workflow in Computed Tomography of the Chest
- 241 Downloads
A CT system with a tablet as mobile user interface and a wireless remote control for positioning and radiation release has recently been presented. Our aim was to evaluate the effects of a mobile CT examination workflow on the radiographers’ performance compared to conventional examinations. A prototype of a radiation protection cabin was installed besides the gantry of a CT system. The CT system was equipped with a simplified user interface on a portable tablet and a mobile remote control. 98 patients with an indication for CT of the chest were randomly assigned to examination using the mobile devices (study group, n = 47) or using the conventional stationary workflow on the console (reference group, n = 51). Three ceiling mounted fisheye cameras were used for motion tracking of the radiographers, two in the examination room and one in the control room. Relative density of detection heat-maps and area counts were assessed using a dedicated software tool to quantify radiographers’ movements. Duration of each task of the examination was manually recorded using a stopwatch. In the reference group 25% of the area counts were located inside of the examination room, while it was 48% in the study group. The time spent in the same room with the patient increased from 3:06 min (29%) to 6:01 min (57%) using the mobile workflow (p < 0.05), thereof 0:59 min (9%) were spent in moderate separation with maintained voice and visual contact in the radiation protection cabin. Heat-maps showed an increase of the radiographer’s working area, indicating a higher freedom of movement. Total duration of the examination was slightly less in the study group without statistical significance (median time: study 10:36, reference 10:50 min; p = 0.29). A mobile CT examination transfers the radiographers’ interaction with the scanner from the control room into the examination room. There, radiographers’ freedom of movement is higher, without any tradeoffs regarding the examination duration.
KeywordsX-ray computed tomography Mobile workflow Thorax Tablets Heatmaps
Digitalization and the introduction of radiological information systems (RIS) and picture archiving and communication systems (PACS) allowed for digital image interpretation and established a linear workflow operating a computed tomography (CT) . Advancements in hardware (tube, detector, or gantry) and software components (reconstruction algorithms, dose saving algorithms) evolved to faster acquisitions with higher resolutions at reduced radiation doses . However, the CT acquisition sequence almost stayed the same until today: registration – positioning – planning – examination – release – reconstruction – archiving. Patient contact of the medical staff is limited to positioning and release of the patient in the examination room during this sequence. The majority of settings and adjustments are controlled from an operating console in a separate control room, where communication is limited to microphones and speakers. This separation between patients and medical staff strongly interferes with efforts to enforce compliance, especially in uncooperative patients. Injured patients, critically ill patients, demented patients or pediatric patients are especially at risk and may require assistance and surveillance during the entire examination, also during radiation . Additional staff in the examination room, wrapped up with lead aprons, is still the only solution to overcome these situations. However, additional human resources are often limited, especially during nightshifts, weekends and holidays, in rural areas and in underdeveloped countries.
Mobile devices are already established in the consumer market and are also increasingly used for home medicine applications . Since they are continuously improving in computing power and battery capacity, many implementations have recently been evaluated in radiologic departments, e.g. for patient briefing , diagnostic procedures , clinical knowledge assistance , case database management  or augmented reality for interventional procedures . Recently a complete user interface application for mobile tablet devices has been presented for CT systems. A redesign of the examination workflow, bringing the radiographer closer to the patient, seems to be possible by integrating these mobile devices in the daily clinical routine. The aim of this study was to evaluate if the time spent together with the patient, which we consider as surrogate for patient contact and interaction, can be increased for radiographers using a mobile workflow to operate a CT of the chest in comparison to the conventional stationary console workflow. Patient proximity and patient experience are hardly measurable parameters. Therefore, camera surveillance and chronographic measurements were chosen for assessment of the surrogate. A prototype of x-ray protection cabin was additionally designed for this study to avoid the time consuming and inconvenient process of dressing and undressing lead aprons.
Materials and methods
During a period of 6 months 360 CTs of the chest were examined with the new CT system. The study was limited to examinations of the chest in order to avoid a bias on the workflow evaluation by other influencing factors, such as different positioning techniques, multi-region or multi-phase protocols. Additionally, CT of the chest is a frequent clinical routine examination that promised to provide a large patient collective. 98 of the 360 patients met the inclusion criteria of regular patients´ mobility (including wheelchair users), informed consent of video surveillance and available monitoring staff. We excluded patients that were confined to bed (like intensive care unit patients) in order to avoid patients’ capabilities becoming a bias between the collectives. Unavailable monitoring staff was the reason for the vast majority of excluded patients. All 98 monitored patients were randomized to examination with the mobile workflow in the study group (n = 47) or the conventional workflow in the reference group (n = 51). The dedicated flowchart of the study design is shown in Fig. 1.
Three fisheye video cameras were mounted on the ceiling of the control room and the examination room as shown in Fig. 2. Camera 1 covered the control room, camera 2 the examination room in front of the gantry, and camera 3 the examination room behind the gantry and the radiation protection cabin. Video recordings were manually started at the beginning of each examination and manually stopped at the end by an additional observer, who was positioned in the control room. The starting point was signalized by the radiographer if the following conditions were met: next patient sits fully prepared in the waiting room - no other persons than the maximum of one leading radiographer, the patient and one supportive radiographer if needed are in the examination room or control room - no pending tasks on the CT system. Completion of all data transfers to the picture archiving and communication system (PACS) and documentation in the radiological information system (RIS) was defined as endpoint. Minimum recommended duration of the video file was 1 h according to the vendor. Therefore, a single cumulative video file of all patients was created for each group. The software is not able to distinguish between different persons.
To support the validity of the video recordings, duration of all workflow tasks was simultaneously assessed manually by the observer using a simple stopwatch: registration, positioning, planning, contrast media injection, release, and post-processing. The examinations were mainly carried out and coordinated by one leading radiographer. When clinically needed, he was supported by a second radiographer in the mobile and the conventional workflow. Tasks fulfilled by the supporting radiographer were limited to patient transfer and management of contrast injections. However, extensive work-sharing was intentionally avoided. As soon as two radiographers were working simultaneously, a second stopwatch was started, and time measurements were noted separately and summed in order to avoid a bias to the complete duration of the examination.
All statistical analyses were performed using the software package SPSS Statistics Version 21 (IBM). Normality of distribution was tested using the Kolmogorov-Smirnov test. Median and range are provided in case of negative test results. Differences in time measurements between the study and the reference group, and subgroup analyses were carried out using the non-parametric Mann-Whitney-U test. The significance level was defined as p < 0.05.
Total number of patients
Mean age (years)
Mean body mass index
Contrast media injection
Mean CTDI (mGy)
Mean DLP (mGy*cm)
Mean estimated ED (mSv)
Heat-maps of the radiographers’ movements provide a comprehensive overview of the radiographers’ location throughout the examination sequence (Fig. 3). Hot areas decreased in the control room, especially in front of the console and across the floor area. A remaining hot area is located in front of the RIS-system, for which a mobile integration is not yet available. The rather constant hot area in front of the surveillance monitor in the control room can be explained by the stationary interaction of the observer. In the examination room, the focal hot spot beneath the top of the patient table and the front cover of the gantry in the reference group evolved to a large hot area spread out over the entire left side in the study group. Also, the area around the injector at the backside of the gantry increased in size and decreased in density, most probably because of an increased freedom of movement using the tablet and remote control. Exemplary benefits from this increased freedom of movement that were found in the videos were: registration and identification while walking into the examination room - selection of the procedure while discussing symptoms with the patient - instruction of rough positioning while moving the table into a first position - precise patient positioning while preparing the contrast injection or fetching cushions - obtaining a view from the end of the patient table aligned to the gantry for precise adjustment of the table to the isocenter. Cold areas were registered in front of the patient table and on the right side in both collectives, but these few detections were also slightly higher in these areas for the mobile workflow. A new area of high relative target density occurred in the radiation protection cabin in the study group.
Radiographers’ time spent in the same room with the patient, which we consider as a surrogate for patient contact and quality in patient care, increased if a CT of the chest was examined with the help of mobile devices. Contact to the patient could be easily increased without a mobile workflow if the radiographers simply take more time for the procedures in the examination room. The drawback of this approach would be an extended total duration of the procedure and therefore a reduced number of patients that could be done per day. The main advantage of the mobile workflow found in this study is that the time spent together with the patient in the same room can be almost doubled without extending the total duration of the examination. Usage of an additional radiation protection cabin adds another 9% of the total duration to patient-vicinity in voice and visual contact.
It is well known that the efficiency of a CT system is mainly limited to the clinical workflow . Several studies evaluated different techniques like intelligent scheduling or multiple radiographer workflows to increase the patient throughput of a CT system in literature  . However, to our knowledge, no approach has yet been presented to redesign the conventional workflow sequence. Lin et al. were able to show that physicians’ time spent with patients is a determinant of patient satisfaction . Although we didn’t assess patient satisfaction, our experience from this study is that the increased proximity of the radiographers to the patients is also beneficial for the compliance during the examination, especially in critical cases like excited or confused patients. It is also well known that children’s compliance often depends on their parents to be in the examination room . The in-room radiation protection cabin presented in this study could be used for these cases as well to minimize the time of separation and to stay in voice and visual contact without increased radiation dose burden. Moreover, parents could also shortly walk in and out the cabin between the localizer and the tomogram to further reduce the separation from their children.
The radiographers’ increased freedom of movement and in-room solution of a radiation protection area presented in this study also opens up for additional concepts to further improve the cost-effectiveness of CT, even if not yet proven by our results. Future software versions of the mobile application could increase in functionality, so that in its strongest form mobile devices could completely replace the stationary console. If also a RIS was integrated on a mobile device, completely new room concepts would be feasible. Architectural planning could then discard the entire control room in favor of a radiation protection area in the examination room. Interventional procedures could benefit from applications like the one for image guidance that has already been reported by Hirata et al. , or as interventional suites in general without requiring other additional equipment than the tablet screen and mobile remote control.
Some limitations must be respected when interpreting our result: First, the mobile workflow was completely new to our radiographers while the conventional workflow has already been well established. Hence, it remains unclear if the rather little reduction of the total duration is due to the increased patient interaction, to the software or room concept in general, or to adaptation problems with the new situation. We expect that a learning effect and further improvements of the mobile workflow, like for example implementing a post-processing option on the tablet, could lead to additional time savings. Second, radiographers that operate a CT cannot be blinded to the procedure. Third, the camera surveillance was unable to differentiate between different radiographers and patients. The second supporting radiographer and patients that had to cross over from the preparation or changing room to the patient table imply a measurement bias. We assume this bias to be small because the frequency of a second assisting radiographer was comparable (30% and 20%) and patients’ interference should be identical and very short in both groups. The erroneous detection during transfer to and from the patient table only takes a few seconds, which we consider negligible in relation to the total duration. Moreover, this bias should not be represented in the time measurements since a second stopwatch was started whenever the second radiographer participated in the examination. Fourth, active time measurements using a stopwatch introduce their own errors. However, we consider the clinical collective large enough to overcome these rather slight inaccuracies. Fifth, we included all consecutive chest CT examinations in order to obtain a high sample size, with the drawback that we are unable to provide information about a special disease or degree of mobility. Sixth, contrast-enhanced and non-enhanced studies cannot be separated in the video evaluation. The knowledge from the time samplings that the contrast application accounts for approximately 10% of the total duration should be respected for the interpretation of the subjective maps. Anyway, we assume that the asymmetric ratio in the study (native/contrast = 3.7) and the reference (1.2) group rather favors an underestimation of area counts in the examination room for the mobile workflow. Seventh, counts in the control room decreased in all areas for the mobile workflow, although stable counts in the ‘RIS Area’ and the ‘Observer Area’ were expected. We attribute this effect to an inaccuracy of the video surveillance software. Persons moving on the edge of one area might overlap into adjacent areas. Eighth, the video surveillance software is limited to a cumulative assessment. Hence, we are unable to provide other statistical evaluation than the presented descriptive values.
Mobile workflows in CT of the chest transfers the radiographers’ interaction with the scanner from the control room into the examination room. There, radiographers’ freedom of movement and time spent in the same room with the patient is higher compared to the conventional setting, without affection of the total duration.
The study was executed at the Imaging Science Institut (ISI, Erlangen, Germany), which is a research cooperation project between the Department of Radiology (University Hospital Erlangen, Erlangen, Germany) and the Siemens Healthcare GmbH, without any dedicated funding of this study.
Compliance with Ethical Standards
Conflict of Interest
Matthias Wetzl and Eleni Schrüfer declare that they have no conflict of interest. Rafael Heiss, Wolfgang Wuest, Alexander Cavallaro, Michael Uder, and Matthias Stefan May are members of Siemens Healthcare GmbH speakers’ bureau. Melanie Weller, Daniel Lerch, Carsten Thierfelder, and Patrick Amarteifio are employees of Siemens Healthcare GmbH.
There was no dedicated funding regarding this study.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Ethical approval from the local review board was waived.
This article does not contain any studies with animals performed by any of the authors.
Informed consent was obtained from all individual participants included in the study.
- 3.Thukral, B. B., Problems and preferences in pediatric imaging. 25:359–364, 2015. doi: https://doi.org/10.4103/0971-3026.169466
- 6.Mc Laughlin, P., Neill, S. O., Fanning, N., Mc Garrigle, A. M., Connor, O. J. O., Wyse, G., and Maher, M. M., Emergency CT brain: Preliminary interpretation with a tablet device: Image quality and diagnostic performance of the apple iPad. Emerg. Radiol. 19:127–133, 2012. https://doi.org/10.1007/s10140-011-1011-2 .CrossRefPubMedPubMedCentralGoogle Scholar
- 7.Schlechtweg, P. M., Kuefner, M. A., Heberlein, C., Meier-Meitinger, M., Cavallaro, A., Uder, M., and Schwab, S. A., A useful tool for routine radiological examinations : The iPhone application KM helper. Radiologe 51:392–396, 2011. https://doi.org/10.1007/s00117-011-2169-z .CrossRefPubMedPubMedCentralGoogle Scholar
- 9.Müller, M., Rassweiler, M.-C., Klein, J., Seitel, A., Gondan, M., Baumhauer, M., Teber, D., Rassweiler, J. J., Meinzer, H.-P., and Maier-Hein, L., Mobile augmented reality for computer-assisted percutaneous nephrolithotomy. Int. J. Comput. Assist. Radiol. Surg. 8:663–675, 2013. https://doi.org/10.1007/s11548-013-0828-4 .CrossRefPubMedPubMedCentralGoogle Scholar
- 10.Sanjeevkumar, A., A review on video surveillance techniques. 4:489–491, 2015.Google Scholar
- 11.Perrot, A., Bourqui, R., Hanusse, N., Lalanne, F., and Auber, D., Large interactive visualization of density functions on big data infrastructure. 2015 IEEE 5th Symposium on Large Data Analysis and Visualization (LDAV). 99–106, 2015. doi: https://doi.org/10.1109/LDAV.2015.7348077
- 12.Boland, G. W. L., Enhancing CT productivity: strategies for increasing capacity. 191:3–10, 2008. doi: https://doi.org/10.2214/AJR.07.3208
- 13.Siegel, E., and Reiner, B., Work flow redesign. 178:563–566, 2002. doi: https://doi.org/10.2214/ajr.178.3.1780563
- 17.Hirata, M., Watanabe, R., Koyano, Y., Sugata, S., Takeda, Y., Nakamura, S., Akamune, A., Tsuda, T., and Mochizuki, T., Using a motion sensor-equipped smartphone to facilitate CT-guided puncture. Cardiovasc. Intervent. Radiol. 40:609–615, 2017. https://doi.org/10.1007/s00270-017-1605-5 .CrossRefPubMedPubMedCentralGoogle Scholar
Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.