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DOI: 10.1055/a-2655-3305
Quality of mammography images taken by medical assistants under remote medical surveillance compared to images taken by radiologic technologists within the German mammography screening program: a non-inferiority study
Article in several languages: English | deutschAuthors
Summary
Can acquisition of mammography images within the mammography screening program also
be carried out in screening units by medical assistants with the necessary knowledge
of radiation protection under remote/digital medical surveillance without loss of
quality?
This non-inferiority study was approved by the radiation protection authorities and
addresses this question by evaluating the mammography examinations of 37808 screening
participants who were examined by a total of 14 technicians over a period of 18 months.
The following radiation protection-related endpoints were assessed: image quality,
repetitions, average glandular dose and examination abortions, each in comparison
of the examinations performed by 4 medical assistants (MA) vs. 10 radiologic technologists
(RT) on 4 mammography devices from the same manufacturer, 2 of which were used at
a stationary location under direct supervision of a medical doctor, and 2 in mobile
screening units under remote supervision.
The quality requirements for the acquisition of screening mammography images are regularly
met by all technicians, regardless of their professional group and form of surveillance.
The study results not only prove the non-inferiority of qualified MAs but also show
a significant superiority of MAs in terms of image quality and repeat exposures in
the present study.
The acquisition of images in the mammography screening program for early detection
of breast cancer can be carried out by qualified medical assistants with the necessary
knowledge of radiation protection under remote surveillance without loss of quality.
Keywords
Mammography screening program - Radiation Protection - Radiography technician - Reserved medical examination - Medical surveillanceIntroduction
The legal basis for implementing the breast cancer screening programme in Germany is the Breast cancer screening ordinance (BrKrFrühErkV [1]) which is based on the Radiation Protection Act (StrlSchG) [2]. The detailed implementation procedures are defined by the Cancer Screening Guideline (KFE)[3] of the Federal Joint Committee (G-BA) and by the Federal Framework Agreement for Physicians (BMV-Ä) Annex 9.2 [4], issued by the organisations responsible for the Mammography Screening Programme, namely the National Association of Statutory Health Insurance Physicians (KBV) and the National Association of Statutory Health Insurance Funds (GKV-SV).
The qualification of personnel performing screening mammography examinations is regulated under radiation protection law by the Radiation Protection Ordinance (StrlSchV) [5]. The BMV-Ä Annex 9.2 stipulates further specific requirements in the form of qualifying courses and guided activities [4]. The physicians responsible for a screening unit are generally responsible for the acquisition of the the X-ray images. In doing so, members of medical-technical professions may also perform tasks without the direct supervision of the responsible physician, in accordance with the Medical Technology Professions Act (MTBG) [6]. Persons with other completed medical training who have knowledge of radiation protection, however, may, according to the StrlSchV, only carry out activities under the continuous supervision and responsibility of a physician with expertise in radiation protection.
To provide eligible women in structurally weaker regions with low-threshold, local access to breast cancer screening, more than 60 mobile examination units, dubbed Mammobiles, are deployed nationwide without direct physician supervision. There is a nationwide shortage of skilled personnel, particularly in medical-technical professions. In view of the standardised nature of the examination, the comparatively low radiation exposure, and the high level of quality assurance, the question arises whether the technical execution of the screening examination by persons with completed medical training and the required knowledge of radiation protection could be carried out under remote physician supervision, without any loss of quality.
Materials and methods
Over a total period of 18 months (01.01.2022–30.06.2023), a pilot study was conducted in a dedicated screening unit in coordination with the Federal Office for the Environment, Nuclear Energy and Nature Conservation (BMUKN) and the Federal Office for Radiation Protection (BfS). At that time, the unit had an official special authorisation allowing medical assistants with the required knowledge of radiation protection and prior experience in performing screening mammograms to operate under remote supervision.
All examinations were performed on 4 Siemens Healthineers FFDM mammography devices, with a stationary site under direct supervision and 2 mobile sites under remote supervision.
Over the entire study period, examinations of 37,808 participants were performed by a total of 14 radiology professionals (RF): 10 radiologic technologists (MTRs) and 4 medical assistants (MFAs) with the required knowledge of radiation protection ([Fig. 1]). A total of 55% of the 9,064 examinations performed by medical assistants with the required knowledge of radiation protection were conducted under remote supervision in one of the two mobile units. Four out of the 10 MTRs were deployed exclusively in mobile units.
In this overall cohort, the proportion of radiation protection-relevant incidents, the rate of incorrect or repeat exposures, and examination discontinuations, as well as the assessment of the average glandular dose were analysed according to the type of supervision and professional group.
In a subgroup of 25,456 participants, the diagnostic image quality was additionally assessed using standardised classifications ([4], Appendix 3), anonymised with respect to the radiology technologist, by 2 experienced physicians ([Fig. 2]). A total of 57% of the 5,146 examinations performed by MFAs with the required knowledge of radiation protection were conducted under remote supervision.
Obtaining an additional ethics approval for the study was deemed unnecessary, as the evaluation of the screened participants is already provided for on the basis of anonymised, or respectively aggregated, data in the KFE, in Annex 9.2 of the BMV-Ä, and under the BrKrFrühErkV. From the perspective of the participating radiology professionals, continuous quality control, supplemented by spot checks, is also enshrined in Annex 9.2 of the BMV-Ä and forms part of the employment contracts within the screening unit.
The technical implementation of remote supervision was achieved through the continuous real-time transmission of the acquisition workstation monitor displays and the local MaSc software [7] via a VPN connection, taking into account transmission delays in the millisecond range due to network limitations. A video splitter (ATEN VanCryst VS172 video/audio splitter 2 × DVI) was integrated between the acquisition workstation and the associated screen to duplicate the signal from the acquisition workstation. The duplicated signal was transferred to a video capture card (HDMI Game Capture Card, USB-C/Type-C 4K HDMI) and routed to an additional PC on which the necessary video software (PotPlayer) for displaying the card contents and the software for remote access (TeamViewer) were installed. Mammography images were also available in diagnostic quality on dedicated workstations for the supervising physician immediately after they were taken via PACS (Picture Archiving and Communication System). A dedicated telephone connection was available to allow the radiology professionals under remote supervision and the supervising physician to communicate directly.There was also the option of communicating with an instant messenger (pidgin)in real-time, as mutual notifications can be displayed directly in pop-up windows.
Data exports for study purposes were made from the certified mammography screening software MaSc via integrated export protocols for general quality assurance according to the protocols for documentation and evaluation in the mammography screening programme [8].
Statistical evaluations were carried out with the software R (v4.3.0; R Core Team 2023) and the statistics package “Stats”. The proportion of participants requiring repeat exposures and the proportion of images rated as quality level I were compared under different conditions. Pearson Χ2 tests without continuity correction were used to calculate the 95% confidence intervals (CI0.95) and significance. The non-inferiority threshold was determined using pre-baseline MTR averages. For non-inferiority in image repetition, the limit value could be set to +2%, for the image quality levels a limit value of –5% could be defined. It was important to adhere to all quality specifications set out in BMV-Ä Annex 9.2. The t-test was used to compare the average dose.
Results
The quality requirements according to BMV-Ä Annex 9.2 are regularly met by both occupational groups, irrespective of the occupational group and the type of supervision ([Fig. 3]).
Repeat images
A total of 691 out of 37,808 participants required repeat images, corresponding to an overall repeat rate of 1.83%, which is below the specified limit of <3%. Regardless of the type of supervision, the average repeat rate was 2.04% for the MTRs and 1.17% for the MFAs.
The detailed results ([Table 1]) of the image quality analysis in relation to participants with image repetition show a quality advantage in favour of the MFAs compared to the MTRs, both under direct supervision (1.08 vs. 2.53%; p <0.001) as well as under remote supervision (1.24 vs. 1.81%; p = 0.016).
A quality advantage for MTRs is evident in the repeat rate under remote supervision compared with direct supervision (p = 0.003). For MFAs, however, there are no statistically significant differences in the type of supervision for the repeat rate (p = 0.472).
Cross-analyses of repeat rates demonstrate a quality advantage of the MFAs over the MTRs regardless of the type of supervision.
Image quality classification by level
The detailed results of the subgroup classification of image quality by level are presented in [Table 2].
The classification is standardised into 3 image quality levels for each of the 4 standard projections per study: compliant (level I), minor deficiencies (level II) and major deficiencies (level III).
In accordance with the BMV-Ä Annex 9.2 Appendix 3, the proportion of deficiencies-free images must be at least 68.75% in a sample test. A maximum of 30% of the images may contain minor deficiencies and a maximum of 1.25% may contain major deficiencies.
Both occupational groups under both forms of supervision comply with the requirements of the BMV-Ä. The level classifications show a quality advantage on the part of the MFA over the MTRs both under direct supervision (level I 97.91 vs. 93.48%; p <0.001) and remote supervision (level I 96.58 vs. 93.03%; p <0.001).
Image quality, as classified by levels, was significantly higher for MFAs under direct supervision than under remote supervision (p <0.001). In the case of the MTRs, image quality under direct supervision did not significantly (p = 0.123) outweigh remote supervision.
Cross-analyses further confirm a quality advantage of MFAs over MTRs, regardless of the type of supervision.
Events relevant to radiation protection
The equipment available ensured that the physicians responsible for a screening unit (PVÄ) were able to intervene immediately without delay, as they would with direct supervision. Radiation protection-related events, defined as exposures that did not contribute to imaging, were observed over the entire study period in 10 participants (0.026% of examinations, 11 events). In 3 participants, the exposure was interrupted by the automatic exposure control of the device after the pre exposition; in 6 participants the release button was accidentally released too early. In one case, the device malfunctioned. Radiation protection-related events occurred in 0.031% of examinations performed by MTRs and in 0.022% of those performed by MFAs. Under remote supervision, MFAs had no exposure interruptions, while MTRs had 5 such interruptions (0.026%).
Cancellation of examinations were negligible over the entire study period, accounting for 0.161%. In just one examination performed by an MFA, the procedure was halted after 2 exposures, before all 4 standard projections could be obtained, with no additional information available. In the remaining cases, there was no radiation exposure. Either there were temporary contraindications, e.g. fresh rib fracture, or the required minimum compression was felt to be too painful. In procedures run by the MTRs, 0.150% of the participants dropped out of the examination. Under the responsibility of the MFAs, this was 0.199%. Under remote supervision, the proportion of interruptions is slightly higher in both professional groups compared with direct supervision, amounting to 0.157% for MTRs under remote supervision versus 0.136% under direct supervision. Among MFAs, the interruption rate was 0.200% under remote supervision, compared with 0.196% under direct supervision. Due to the small number of cases, the determination of a significance level is not necessary.
Average Glandular Dose (AGD)
The organ dose, called average glandular dose (AGD) in mammography, was evaluated for all images. Excluding the supervisory typ, the mean AGD of acquisitions by MTRs is 1.137 mGy (CI0.95 = 1.135; 1.139) and 1.116 mGy (CI0.95 = 1.113; 1.120) for MFAs (p <0.001). For remote supervision, the mean AGD for MTR examinations is 1.149 mGy (CI0.95 = 1.147; 1.151) and for MFA is 1.142 mGy (CI0.95 = 1.138; 1.146).
The distribution of the dose by occupation and mammography device is shown in ([Fig. 4]). The median radiation dose does not exceed the diagnostic reference level (DRL) for mammographic examinations set by the Federal Office for Radiation Protection (BfS) at 2.0 mGy for any occupational group or type of supervision [9]. Overall, the dose is greater than 2.0 mGy in 1.5% of exposures.
Discussion
The present study was designed as a non-inferiority study to clarify the extent to which screening mammography images can also be taken by MFAs with knowledge of radiation protection under remote supervision without loss of examination quality. Regardless of the form of supervision, both occupational groups meet the quality requirements of the BMV-Ä. The present study was able to demonstrate not only non-inferiority but actually showed superiority of the occupational group of the MFAs involved with statistical significance ([Fig. 5]).
To mitigate potential bias arising from the small overall number of radiology professionals, and especially the even smaller number of MFAs, this was offset by the large number of examinations performed over an extended period. Overall, screening mammograms from 37,808 participants were included in the analysis, acquired over a total period of 18 months. The longer survey period smooths out possible variations in the examination quality of individual radiologists that could not be ruled out over a short period of time.
When evaluating the study, it should be borne in mind that the professional group of MFAs was required to have a dedicated level of prior experience, as opposed to the MTRs. To obtain official special authorisation for the deployment of MFAs under remote supervision, MFAs were required to have 18 months of prior experience in the mammography screening programme and to have completed a minimum of 2,000 screening examinations. The MTRs were not subject to these requirements. It was, however, ensured that MTRs completed at least 4 months of mammography screening under the supervision of an experienced radiology professional before being deployed independently under remote supervision in a mobile examination unit. During this induction period, each MTR completed at least 500 examinations under supervision and guidance. A learning effect through continuous activity can thus be assumed for both occupational groups.
Besides professional and technical skills, a psychosocial component affects the quality of examinations, but it is not amenable to standardised assessment. Whereas MTR training focuses on medical-technical diagnostics, MFAs function as the medical interface with patients, carrying out both clinical assistance and administrative duties. If the number of cancelled examinations with or without radiation exposure was taken as an indicator, the total number would still be too small to make a reliable statement.
As with all screening tests, only the group of people who have the disease actually benefits from the screening programme. On the other hand, undesirable effects can affect any participant. From a radiation protection point of view, the medical benefit of the examination must clearly outweigh the radiation risk, and the radiation dose must not be higher than necessary to clarify the medical question. Analyses of the AGD (median) showed that the diagnostic reference level (DRL) was not exceeded in any cases. The DRL is not to be interpreted as an optimal or limit value for individual examinations ([9], p. 12) rather, DRL is defined as the 75th percentile of a distribution of dose values from different users and manufacturers. The dose increases with increasing breast size/compressed breast thickness and breast density. Dose values of > 2.0 mGy are unavoidable in individual cases (1.5%) for anatomical reasons. The mammography devices used operate at different dose levels. Factors that determine the radiation dose are the automatic exposure control and the interaction of the detector and X-ray tube. Consequently, the mean radiation dose can only be compared for each specific mammography device and not across supervision types for all devices. When comparing the dose of examinations of the two occupational groups per device, the mean values and medians of the AGD differ in the order of 0.01 mGy. This difference, being less than 1%, is therefore considered negligible. Differences in the AGD, which are basically device- and manufacturer-dependent, are at the same level.
The study results raise the question of whether, with appropriate basic qualifications and dedicated additional training, equivalent performance in a clearly defined domain could be achieved, even independent of the form of supervision.
As a comparative example from the medical field, the difference between surgical nurses and surgical assistants (OTA) should be used here. The occupation/profession of OTA has existed since the 1990s. Since 2022, it has been officially recognised as an independent training profession under the Act on the Profession of Anaesthesia Technical Assistant and Surgical Technical Assistant (ATA-OTA-G) [10]. An operating theatre nurse is a qualified health and nursing professional who, after completing basic training generally taking 3 years, undertakes a 2-year specialist training in surgical care. Surgical technical assistants complete a dedicated 3-year training programme focused on the operating theatre, without requiring prior nursing qualifications. However, the roles of both professions are largely identical.
Conclusion
Given the number of radiology professionals included, it may not be possible to apply the observed superiority of MFAs in this study to the profession as a whole as this result may be subject to bias. The findings of this study, however, provide sufficient evidence that screening examinations may be performed by individuals with completed medical training and requisite radiation protection knowledge under remote medical supervision without compromising quality. The present study does not support conclusions concerning the general application of the special constellations in the mammography screening programme to other areas of medical-technical diagnostics.
Conflict of Interest
The authors declare that they have no conflict of interest.
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Correspondence
Publication History
Article published online:
17 December 2025
© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Georg Thieme Verlag KG
Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany
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