The introduction of a flat panel system in a filmless computerised radiology unit allows the productivity of a radiology department to be noticeably increased, while providing ergonomic comfort and ease of use. It is particularly suitable for the field of paediatric radiology.
There are numerous factors that drive a radiology department to adopt digital imaging technology. The use of the Picture Archiving and Communications System (PACS) and hospital managements' need to optimise operating costs for higher efficiency are only two examples.
With these factors and the impending obsolescence of the existing conventional radiography system in some regions, the radiology department (University Hospital of Nancy, France) decided on a fully automated digital flat detector radiography system. Reasons for this decision were the preference for a Flat Detector (FD) system that delivers a high level of automated system movements. Numerous independent studies have proved that flat detector imaging systems improve productivity and deliver significant dose-saving advantages.
Comparing FD and CR systems
This study was performed in a paediatric radiology department of a university hospital with an annual patient throughput of 30,000 for general radiography. 40% of these imaging examinations are emergency cases with the patient throughput remaining at a stable level in recent years. There are two general radiography rooms. The digital flat detector radiography system is installed in one of them while the other room has a conventional radiography unit with a Computerised Radiography (CR) imaging system. The study focussed on the comparative evaluation of the FD system and the CR system with regard to three key indicators: patient throughput, changes of workload within the rooms and user satisfaction.
The equipment that allowed the radioluminescent plate system to be tested is the Siemens (with a free-floating table and of variable height) installation (ceiling-suspended installation), connected to a PCR AC 3000 Philips RLMS system.
The tested DR system is an Axiom Aristos FX Siemens installation (Erlangen – Germany) with a flat panel (Trixell, Moirans – France), large screen (43 cm x 43 cm), with a matrix of 3000 pixels x 3000 pixels. Movements of the panel and the X-ray tube are completely automatic. The computer interface is provided by means of a syngo platform running on Microsoft Windows.
Methods and evaluation
The first part of the study focussed on the comparative evaluation of overall patient throughput. A total of 193 patients were evaluated during the study, with 94 patients examined on the conventional/CR system and 99 patients examined on the FD system. Of these 193 patients, five categories of examinations were evaluated; chest, abdomen, pelvis as well as upper and lower extremities. The examinations were further divided into those with a single exposure and those with two exposures (where frontal and lateral projections are standard). Throughput and average examination time of these procedures were also measured. Additionally, each examination was broken into three phases to analyse where the most benefits were experienced. The three phases were:
• Positioning phase: Patient positioning and placement of detector or CR cassette for each respective system.
• Execution phase: Execution of the imaging process including exposure, access to patient data, CR cassette processing and visualisation of image for FD system.
• Acquisition phase: Consisting of archiving via PACS for the two radiographic systems.
The comparison of the different times for each step of the execution of the action, then by anatomic area explored was done by comparison to averages, using the t test and the Mann-Whitney nonparametric test (SPSS 11.0 software).
The second focus of the study assessed the workload distribution of patients to the two different radiographic rooms over the one year study period. Activity curves were created to allow a time comparison of results and an evaluation of stability over the long-term.
Changes in organisation and division of duties among technicians occasionally involved in the installation of the DR were likewise studied.
Finally, a satisfaction survey was carried out among fourteen technicians of the paediatric radiology department, for a total of 16 persons. To find out the opinion of the users regarding ease of use, speed of examination, image quality and user-friendliness of each of the two systems the following valuation system was used:
• +2 for DR much better than RLMS
• +1 for DR better than RLMS
• 0 if the two systems are equivalent
• -1 for RLMS better than DR
• -2 for RLMS much better than DR
Results of comparison
Comparative evaluation of the complete patient treatment time found a 30% reduction from 403 seconds to 266 seconds with the FD system compared to the CR system. The patient treatment time was defined as the time when the patient arrived at the waiting room to the time the acquired image was available on the internal network. On an average, time savings between 48% and 59% were achieved for the various examinations from chest to pelvis, with the greatest time savings for pelvis examinations. It was also measured that on an average, 55% time savings could be achieved for single exposure studies and 51% for double exposure studies. While the time requirements of the installation phases were comparable, most timesavings occurred in the film execution phase and especially in the image-processing phase with timesavings values of 42% and 83% respectively. It should be noted that a distance of about 15 meters between the room connected to the RLMS reading system requires an average movement of the technician of about 15 seconds, with sometimes a waiting time if the other room is in use.
The time of the undressing phase was measured at an average of 40 seconds, while the phase following the transfer of the image to the Intranet via the PACS took 95 seconds for both systems. Consequently, a total of 135 seconds on average were reserved for handling a paediatric patient outside of the specific execution of X-ray activity.
For workload distribution, it was observed that by the end of the study, 84% of patients were assigned to the room with the installed flat detector radiography system. This is largely due to preference of the new technology by the users for its image quality, dose savings of up to 40%, and reduction in mAs values while achieving identical image density and contrast.
Eleven of the 14 users surveyed preferred the flat detector system on all performance criteria while three users found the flat detector and CR systems to be similar for one criterion each.
The values demonstrated during the time measurements are unambiguous. The flat panel system technology is significantly faster in the three examination phases. These results allowed us to quantify our technological choice of a DR system in a paediatric radiology department with much regular and emergency activity (40% of the total activity), rather than justify to the institution the benefit of the investment.
During the film phase, the flat-panel system allows the image to be visualised within 6 seconds after exposure, while it takes 35 to 55 seconds for reading based on the size of the screen for the RLMS system. The presetting of the opening of the diaphragms as well as automatic marking considerably reduce the time of the image handling phase. This leaves the installation part, which, due to its automation, allows a considerable savings of time with regard to the placement of the material. The “all in one” system which offers the flat panel system allows a large savings of time in personnel movement, as opposed to the RLMS system which requires technicians to move back and forth between the radiodiagnostics room and the plate reader.
The speed of visualising a quality image and the system’s ergonomic design make it a pleasure to use. The paediatric radiology staff is making the utmost attempt to have the patients, parents and staff from clinical departments accompanying the child benefit from this technology, which allows waiting time to be reduced.
The productivity increase of the system frees up technician time and requires a different way of thinking about patient care. This has enabled the staff to devote more time to the quality of patient reception, hygiene regulations and tracking images for archiving and distribution to clinicians. On the other hand, this requires a minimum of two, even three, technicians to ensure continuous use of the installation when there is an overflow of patients.
However, the flat panel system, in its current configuration, may not always be able to completely handle the activity of two radiology installations. The dimensions of the panel do not allow for use in patient beds or on a stretcher. As with any motorised system, manual movement of the suspended system supporting the X-ray tube proved to be difficult and required significant physical effort of the staff. Placement of the bed in the radiology room, moreover, is not easy, taking into account the installed examination table. These drawbacks cause a significant decrease in patient care, which exceed the time needed with a conventional system and cancels out timesavings. Areas of exploration greater than 43 cm (legs and femurs of adolescent patients, teleradiography of the spine and lower extremities) will soon be examinable by means of multiple exposures and image-fusing software. However, performing teleradiography of the spine or lower extremities will still remain impossible for patients with multiple handicaps requiring time for short exposure, thus the use of a single exposure.
In addition, parallel to this study, dosimetric studies confirmed that it was possible to decrease the number of necessary mAs by 40%, while still maintaining identical density and contrast, which proved satisfactory to radiologists and clinicians. This lowering of the applied dose is a major advantage for paediatric X-ray departments where radioprotection is a constant concern.
The flat panel system is a new technology, which allows for a considerable savings of time in standard examinations.
The future availability of software for performing teleradiography could further expand the uses of the system. It has been demonstrated to be particularly effective for the management of a high number of patients in a paediatric department, including an important ratio of emergency cases.