Integrated shielding on a mobile head CT system substantially reduced occupational radiation exposure in a neurointensive care unit and may remove the need for additional protective equipment under defined conditions. The findings, published in the British Journal of Radiology, come from measurements at Karolinska University Hospital in Stockholm, Sweden. The system uses a foldable lead curtain at the front of the gantry and a detachable lead shield at the back. With suitable radiation safety training, staff exposure remained low, particularly when personnel stayed behind the operator console or maintained sufficient distance from the gantry.
Integrated Shielding Reshapes Scatter Exposure
Measurements around the mobile scanner showed that its integrated shielding reduced scatter radiation by 91% to 99% in most assessed directions. The exception was the position behind the operator console, where the reduction was smaller because the gantry itself already provided substantial shielding and exposure was low even without the additional covers. The protection consists of a foldable 0.5-mm lead curtain over the front opening and a detachable 1-mm lead shield at the back.
The safest location was along the short side of the gantry where the operator console is positioned. Areas beside the patient and behind the gantry were less protected, although the upper part of the gantry reduced scatter at eye level behind the unit. Across all measured positions, however, the integrated shielding substantially reduced scatter radiation. Measurements were designed around several realistic staff locations, including observing from a distance, attending the patient, operating the scanner and managing equipment behind the gantry.
The scanner’s moving gantry also changed how exposure developed during an examination. On the patient-table side, dose rate decreased as the scan progressed, while the opposite pattern occurred behind the gantry. Because the gantry moves over the patient rather than remaining fixed while the table advances, the distance between the scatter source and staff positions changes during scanning. As a result, scatter dose per examination did not scale linearly with scan length, making dose-length product unsuitable for assessing staff exposure in this setting.
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Staff Positioning Keeps Personal Dose Low
Three months of passive monitoring found no ambient dose readings above the dosimeters’ minimum detectable level of 0.05 mSv. Eye lens dosimeters worn by 2 radiology nurses also remained below their 0.1 mSv detection threshold. The monitoring covered cumulative exposure in the neurointensive care unit rather than individual scans. These findings were limited by the local workload because the mobile head CT was used for fewer than 3-4 examinations per week, reducing the usefulness of cumulative passive monitoring alone.
Active dosimeters provided scan-by-scan measurements during 31 adult patient examinations. Average personal dose per examination was 0.07 ± 0.03 µSv for the radiology nurse operating the scanner and 0.03 ± 0.02 µSv for the primary clinician attending the examination. The highest recorded dose, approximately 1 µSv, occurred on the only occasion when the integrated shielding was not used. Even then, the recorded exposure remained limited, which was linked to deliberate staff positioning during the scan.
Positioning helped explain the difference between staff roles. The operating nurse could substantially reduce exposure by standing directly behind the console, while the attending clinician could remain behind the console or at a considerable distance from the gantry. In practice, the primary clinician typically left the room during scanning, which accounted for generally lower exposure than that of the operator. The measured staff doses remained well below the occupational and public exposure limits cited in the analysis.
Training Supports Reduced Use of Protective Equipment
The low measured exposure with the integrated covers in place suggests that mobile head CT examinations can, under certain conditions, be performed without additional personal protective equipment such as protective aprons. This conclusion depends on the shielding being correctly deployed and on staff following basic radiation protection measures, including limiting time near the scanner and maintaining distance when proximity is not necessary. The approach may improve staff comfort and supports use in hospital areas with limited radiation shielding.
Based on the measured doses, staff would have to be involved in more than 1000 examinations to reach a cumulative effective dose of 0.1 mSv when the integrated shielding is used. Without the integrated shielding, the same threshold would be reached after approximately 100 examinations. These projections assume consistent working practices and routine application of basic precautions. They therefore depend on staff continuing to avoid unnecessary proximity to the gantry and using the shielding as intended.
Radiation safety training remains central to the approach. Staff operating the system need to know how to position the frontal lead curtain correctly, secure the back cover and apply the principles of time, distance and shielding. The system also allows the patient to remain visible through bore lighting and a camera feed displayed at the operator console while the front cover is closed. When clinical circumstances prevent use of the integrated shielding, protective equipment such as aprons and leaded eyewear should be considered to keep exposure as low as reasonably achievable.
Mobile head CT with integrated shielding can markedly reduce staff exposure in the neurointensive care setting, with the lowest exposure achieved when personnel remain behind the operator console or keep sufficient distance from the gantry. The findings also indicate that additional protective equipment may not always be necessary when the built-in shielding is used correctly. That approach depends on appropriate staff training and consistent radiation safety practice. The results are also tied to the relatively low local examination rate, which limits the value of passive cumulative monitoring on its own.
Source: British Journal of Radiology
Image Credit: iStock
References:
Hillergren P, Hulthén M, Vorbau R & Omar A (2026) Mobile head CT with integrated radiation shielding reduces the need for additional personal protective equipment. British Journal of Radiology, 99 (1182):1156–1161.
