We installed DoseTrack (Sectra Medical Systems, Sweden) and integrated the system in our picture archive and communication system (PACS, same vendor). Several CT scanners, angiography and fluoroscopy suites and x-ray units were connected to the DMS, which transmit radiation dose structured reports (RDSRs) for further processing in the DMS. Amongst others, RDSRs include information about the examination type, patient characteristics (age, weight), the employed acquisition parameters and exposure data. The examination type, patient age and weight are required to associate the exposure data with the correct DRL value. The acquisition parameters help to investigate DRL exceedances.
In collaboration with the DoseTrack specialists from sectra, we worked on the further development of the functions and tools the DMS provides. We customized the DMS for our modalities and purposes. In the following, the main customization steps are described:
Configuration of dose alerts
Patient age and weight-specific DRLs for the different examinations, as provided by the federal agency of radiation protection (Bundesamt für Strahlenschutz), were stored in the DMS. The assignment of examinations to DRLs is acquisition-based and not study-based since some studies may contain acquisitions with different DRL-value. One example are staging CTs, where the arterial phase only covers the liver whereas the venous phase covers the complete trunk. The individual acquisition names were matched to the correct DRL. In case of new acquisition names or typos, a list of unknown and unassigned names was created and is constantly updated in case of new or unknown acquisition names.
To determine examinations with a DAP >20000cGycm² (threshold value for diagnostic angiographies), a dose alert was activated when exceeding a DAP of 20000cGycm². Although there is another threshold value for interventions (DAP>50000cGycm²), we stick to the lower threshold as alert for any angiographic examination.
For every examination, the DMS compares the incoming exposure and patient data with the stored DRLs or threshold values (figure 1). If no DRL is available, data is stored in the DMS for individual later analysis. For every DRL or threshold exceedance, dose alerts are subsequently sent to a radiation protection work-group with details of the specific examination (figure 2). Since our DMS is integrated in our PACS system, the examination is highlighted in a web-banner (figure 3).
Customization of dose alert reasons:
The DMS provides a predefined list of “investigation statuses” (equipment fault, operator error, large patient) to specify explanations and annotate dose exceedances directly in PACS. During this work, this list was customized to detect examinations, modalities and patient characteristics that often result in DRL exceedance (figure 4 and 5).
- Arms not elevated
- Patient is heavy
- Long scan coverage desired
- Metal implants in patient
- Foreign material in FOV (stiffneck, ECLS, resuscitation board)
- User error
- Repetition of examination due to patient movement
- Scanner error
- Complicated examination (interventions)
- Faulty surview
- Others (individual justification)
Either the radiologist, the technician or the medical physicist can specify explanations and annotate dose exceedances directly in PACS via the customized “investigation status” drop-down menu and annotation field.
Work in progress
Currently, a dose alert is created for any dose exceedance, independent of its extent. This might cause a complex accumulation of alerts, where important exceedances might be missed. A special notification for patients exceeding the DRL by 200% is planned in a next version of the DMS. An exceedance by 200% additionally implicates a further investigation of 19 past examinations employing the identical protocol to determine whether a patient-specific or a protocol-specific issue caused the DRL exceedance. The next version of the DMS should implement this analysis option.
Furthermore, the DMS counts bi-planar angiography suites as two different dose entries without calculation of the total DAP. Dose alerts are only emerging if a single head exceeds the DAP for an examination or the threshold value. The total DAP can be manually calculated from the information of both heads, but this misses the point of having an automatic DMS. The summed DAP from both heads will be included in the next version.
Currently, national DRLs are included in our DMS for generating dose alerts. However, with national DRLs, disproportionate exposures might stay unnoticed in small patients not exceeding DRLs. Institutional and size-specific DRLs offer a more comprehensive analysis and quality assurance and need to be implemented in a second step.
Finally, not all of our x-ray units are capable of sending RDSRs. In the next step, we will connect those x-ray units to the DMS, which have the required dose and examination information stored in the DICOM header.