The radiology reading room today is busier than ever with increasing numbers of cases that contain more images, sequences, and complex findings. Consequently, radiologists are becoming more fatigued and burned out. To ad...The radiology reading room today is busier than ever with increasing numbers of cases that contain more images, sequences, and complex findings. Consequently, radiologists are becoming more fatigued and burned out. To address this growing problem, studies have been conducted to objectively measure fatigue and its impact on diagnostic accuracy and efficiency, with growing evidence that the impact is negative and significant after just 8 h of clinical work. The impact (increased errors, reduced ability to focus) may be greater for residents than for experienced radiologists. Artificial intelligence (AI) may be a potential solution to address fatigue, but we need to understand exactly how it affects users and their decision-making processes to optimally use it as a decision aid in clinical practice.
Accurate extremity dosimetry is essential in nuclear medicine due to finger exposure being one of the major radiation protection concerns. Instinctive ring wearing habits, such as facing decorative elements outwards or '...Accurate extremity dosimetry is essential in nuclear medicine due to finger exposure being one of the major radiation protection concerns. Instinctive ring wearing habits, such as facing decorative elements outwards or 'diamond-up', frequently leads to incorrectly orientated thermoluminescence dosemeter (TLD) ring placement. This study investigated how the orientation of TLD rings can affect recorded extremity dose when handling 99mTc. A two-part method was undertaken involving a physical experiment using a constructed finger phantom followed by a Geant4 Monte Carlo simulation to validate the findings. The results highlighted that doses were significantly reduced by a ratio of 19:1 (-95%) when TLD dosemeter rings were orientated outward when compared to inward, primarily due to the additional attenuation introduced by the finger. Greater awareness on the influence of ring orientation is essential for improving the accuracy of extremity dosimetry, addressing a simple yet often overlooked aspect of radiation protection.
Dustler M, Ohashi A, Tomic H
… +4 more, Johnson K, Zackrisson S, Tingberg A, Bakic PR
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821447
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Rapid adoption of artificial intelligence methods in breast imaging research emphasizes the need for large, appropriately curated image databases for development and validation. For digital breast tomosynthesis (DBT), th...Rapid adoption of artificial intelligence methods in breast imaging research emphasizes the need for large, appropriately curated image databases for development and validation. For digital breast tomosynthesis (DBT), there are few public databases with only limited lesion annotation. Recently, we have developed Malmö Breast ImaginG (M-BIG), a large database of 104 791 women screened at Skåne University Hospital, Malmö. M-BIG also includes all images from the Malmö Breast Tomosynthesis Screening Trial, MBTST of 14 848 women, with 139 biopsy-confirmed cancers from DBT screening. To annotate lesions in M-BIG, we designed a semi-automated custom software tool for DBT, and corresponding digital mammography (DM) images. A reader manually draws an outline; or marks nodes around the lesion which are automatically connected by an edge-following algorithm. Our custom tool enables detailed annotation of DBT and DM lesions, as opposed to the rectangular regions present in other published material, allowing extensive evaluation of tumor segmentation, and analysis of size and shape descriptors.
Markbo JH, Bakic PR, Isaksson H
… +2 more, Johnson K, Dustler M
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821446
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The focus of this study was to evaluate the feasibility of incorporating Perlin noise, a method that has previously been used to model the tissue distribution of software breast phantoms, when creating a 'compressible' s...The focus of this study was to evaluate the feasibility of incorporating Perlin noise, a method that has previously been used to model the tissue distribution of software breast phantoms, when creating a 'compressible' software breast phantom used in finite element analysis. Several compressible phantoms were created to represent different stages of aging in a virtual patient when younger, fibroglandular tissue is more prevalent than adipose tissue. During the ageing process, this ratio changes so that the breast contains more adipose tissue and less fibroglandular tissue. When simulating the compression of these phantoms, the determined reaction forces on the simulated compression plate increase with higher breast density. The resulting reaction forces on the compression plates are well above the values from in vivo measurements performed by our research group. However, when considering the differences between the procedures in the two studies, the simulated results are arguably comparable to the in vivo measurements.
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821445
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Diagnostic reference levels (DRLs) were introduced as a tool to optimize radiation protection in medical imaging. Conditions for dose assessment have evolved significantly. This study explores how effectively the current...Diagnostic reference levels (DRLs) were introduced as a tool to optimize radiation protection in medical imaging. Conditions for dose assessment have evolved significantly. This study explores how effectively the current DRL system functions and whether it requires adjustment. The analysis focuses on the national DRL system in Sweden and includes European projects and guidelines for reference. The variability in typical doses has decreased. National DRL values have been lowered; however, values in nuclear medicine have seen minimal change. These developments present challenges in revising the values. The increased availability of digital data offers both opportunities and challenges. The DRL system may include specific indications, larger patient cohorts, and consideration of patient size. To remain relevant, the DRL system must be updated to reflect changes in clinical practice. The integration of image quality assessment into the DRL framework is one critical area that requires further development.
Photon counting computed tomography (PCCT) provides exceptional image quality with reduced radiation dose in temporal bone imaging and is emerging as a potential new gold standard. This study aims to assess the feasibili...Photon counting computed tomography (PCCT) provides exceptional image quality with reduced radiation dose in temporal bone imaging and is emerging as a potential new gold standard. This study aims to assess the feasibility of an in-house micro-computed tomography (micro-CT) system equipped with Photon Counting Detector (PCD) technology and to compare it with a clinical PCCT scanner for temporal bone evaluation. A fresh-frozen temporal bone specimen was scanned with both systems, focusing on four anatomical landmarks: stapes, lateral semicircular canal, tympanic segment of the facial nerve canal, and modiolus. Two radiologists assessed the landmarks, using clinical PCCT images as the reference. The in-house micro-CT achieved a high resolution of 32.5 μm, enabling excellent visualization of the landmarks. These results demonstrate that the PCD micro-CT system is a feasible and valuable tool, offering important insights into the complex structures of the middle and inner ear for advancing both clinical and research applications.
Reject rate analysis focuses traditionally on frequency rather than radiation impact, thus limiting its alignment with radiation protection goals. This study examined reject rates by body part in digital radiography at a...Reject rate analysis focuses traditionally on frequency rather than radiation impact, thus limiting its alignment with radiation protection goals. This study examined reject rates by body part in digital radiography at a Finnish imaging department and introduced an evaluation of their relative contribution to patients' additional radiation exposure by calculating a median effective dose-weighted reject rate. The resulting metric may serve as a practical tool to support optimization of radiation burden. The pelvic region and lumbar spine rejected radiographs contributed the highest additional radiation dose, followed by the chest, where the high examination volume outweighed the low relative rejection rate in population-wide dose impact. Extremities contributed negligibly to additional effective dose irrespective of their reject rates, primarily due to a substantially lower radiation sensitivity. These findings emphasize the value of integrating effective dose metrics into reject analysis to better reflect patient risk and enhance quality assurance.
Mehrara E, Mohamed M, Van-Essen M
… +1 more, Lopez Urdaneta J
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821442
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Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) quantifies changes in radiotracer uptake to assess therapeutic response in cancer. However, the accuracy of these quantifications depends on imagin...Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) quantifies changes in radiotracer uptake to assess therapeutic response in cancer. However, the accuracy of these quantifications depends on imaging parameters, tumor size, and the local tumor-to-background uptake ratio (local-TBR). In this study, 'background' refers to the surroundings of the lesion rather than a standardized reference tissue. A NEMA Image Quality phantom was filled with 18F-FDG at varying sphere-to-background ratios to simulate clinical scenarios corresponding to PERCIST-defined thresholds for partial metabolic response (-30%) and progressive metabolic disease (+30%). Positron emission tomography (PET)/computed tomography imaging revealed that measured uptake changes systematically underestimated the true ±30% differences, particularly in smaller spheres. These findings indicate a potential source of systematic error in PET-based tumor response assessment, which may influence clinical interpretation. Further studies are recommended to investigate the effects of varying imaging parameters, tumor types, and clinical settings to improve the robustness of PERCIST-based evaluations.
Alström L, Bjerkén A, Dahlblom V
… +3 more, Timberg P, Dustler M, Tingberg A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821441
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To assess the robustness of risk scores provided by an artificial intelligence (AI) system for digital mammography (DM), when varying the exposure conditions. An anthropomorphic breast phantom containing a lesion, was im...To assess the robustness of risk scores provided by an artificial intelligence (AI) system for digital mammography (DM), when varying the exposure conditions. An anthropomorphic breast phantom containing a lesion, was imaged with DM at different tube voltages (kV), tube loadings (mAs), and anode/filter combinations (W/Rh, Mo/Mo, and Mo/Rh). The organ doses were extracted from the DICOM header and used as a substitute for average glandular dose. The images were analyzed with an AI system, which provided a lesion risk score which translates to suspicion for malignancy. Correlations between the lesion risk score and the exposure conditions were investigated. In most imaging conditions, weak to moderately strong positive associations between lesion risk scores and kV and mAs, respectively, were reported (varying by anode/filter combinations). When organ dose increased the AI risk scores plateaued, and further increase did not increase the lesion risk score. For typical clinical settings (W/Rh, 27 kV and 71 mAs) the range of lesion risk scores was 33-56 (mean: 42, SD: 9). Greatest reported variability (range: 36-63, mean: 51, SD: 12) was found at 27 kV and 36 mAs (using W/Rh). Images of suboptimal quality may result in inaccurate AI system performance. The unexpectedly large intra-group variability of AI risk scores should be further investigated.
Larsson J, Grönqvist Z, Carlstein O
… +1 more, Asplund S
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821440
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A unified computed tomography dose index (CTDI) which includes all scattered radiation was used to investigate the difference in absorbed dose to the patient between a computed tomography (CT) and a cone beam CT (CBCT)....A unified computed tomography dose index (CTDI) which includes all scattered radiation was used to investigate the difference in absorbed dose to the patient between a computed tomography (CT) and a cone beam CT (CBCT). The unified CTDI, denoted CTDI300,w, was measured using a 100 mm pencil ionization chamber at three positions covering 300 mm at each of the five phantom slots in three CTDI body phantoms. The dose length product of a lumbar spine protocol for the modalities was comparable (CT: 153 mGycm, CBCT: 126 mGycm), though the normalized CTDI300,w for the CT was 4.6 times higher than for the CBCT. The comparison between CTDI300,w and the two dose indexes provided by the systems showed a substantial underestimation for both modalities. The most accurate, but also the most inconvenient method to compare absorbed dose is to use the CTDI300,w. Most important is to always use the same dose index.
Gianko E, Oliveira Diniz M, Cifuentes Ramirez W
… +4 more, Rossi Norrlund R, Johnsson ÅA, Båth M, Svalkvist A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821439
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Deep learning image reconstruction (DLIR) utilizes neural networks to generate high-quality computed tomography (CT) images. One commercially available DLIR software is TrueFidelity from GE Healthcare. The Standard kerne...Deep learning image reconstruction (DLIR) utilizes neural networks to generate high-quality computed tomography (CT) images. One commercially available DLIR software is TrueFidelity from GE Healthcare. The Standard kernel was the only available reconstruction kernel previously, but recently other kernels, including the Lung kernel, have been introduced by GE. This study aimed to evaluate the image quality of chest CT scans acquired at full-dose (FD, 2.5 mSv) and ultra-low-dose (ULD, 0.05 mSv) when reconstructed using TrueFidelity with both Standard and Lung kernels. Twenty-five patients underwent chest CT scans at Sahlgrenska University Hospital. The images were reconstructed and then evaluated by four radiologists in two different studies, one including ULD CT axial images and the other one the FDCT. Visual Grading Characteristics (VGC) analysis was applied, using the Standard kernel as reference and the area under the VGC curve (AUCVGC) for comparison. At FD, the Standard kernel yielded better results regarding the visualization of six structures and the general image quality. However, in ULD scans, the differences between kernels were not statistically significant. The FD images were mostly rated as acceptable, while ULD images were often rated as probably acceptable or unacceptable, especially for emphysema assessment. Overall, TrueFidelity seems to perform better with the Standard kernel than with the Lung kernel in FD protocols, but no reliable conclusions can be drawn for the ULD protocol.
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821438
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The nonprewhitening matched filter (NPWMF) is frequently used to assess task-based image quality in computed tomography (CT). However, modern reconstruction algorithms, based on iterative reconstruction (IR) or Deep Lear...The nonprewhitening matched filter (NPWMF) is frequently used to assess task-based image quality in computed tomography (CT). However, modern reconstruction algorithms, based on iterative reconstruction (IR) or Deep Learning image reconstruction (DLIR), exhibit properties that undermine Fourier domain approaches. One alternative is to abandon the NPWMF. Here, instead, calculation of the NPWMF in the spatial domain is explored with and without assumption of Gaussian observer response. Model observer predictions of area-under-the-curve were determined for a Revolution CT scanner (GE Healthcare) and a NAEOTOM Alpha scanner (Siemens Healthineers). For the former, the vendor's IR and DLIR were investigated. For the latter, the vendor's IR was used and compared to results from a reader study. Results support the conclusion that Fourier domain calculations can exaggerate benefits of denoising and that spatial domain calculations can provide good agreement with human observers. Assumption of Gaussian observer response did not lead to substantial errors.
Thor D, Söderberg M, Poludniowski G
… +1 more, Brismar TB
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821437
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Localizer orientation can significantly impact the automatic tube-current modulation (ATCM) in computed tomography (CT). The purpose of this study was to introduce a methodology for assessing ATCM consistency and to comp...Localizer orientation can significantly impact the automatic tube-current modulation (ATCM) in computed tomography (CT). The purpose of this study was to introduce a methodology for assessing ATCM consistency and to compare the outcomes in image noise and radiation dose between a single anterior-posterior (AP) localizer and a combination of lateral and AP (LAT + AP) localizers. A total of 299 prospective patients referred for a routine CT thorax examination were randomly assigned to a single AP or LAT + AP localizer. Measurements of image noise and patient size were performed in the thorax and liver, and the corresponding effective milliampere-second (mAseff) at these positions were collected. Performance analysis was conducted using the normalized root mean squared error (nRMSE) of mAseff and image noise relative to patient size. A smaller nRMSE indicates more consistent inter-patient variance in image noise and mAseff for a given size. The LAT + AP group had a statistically significant lower nRMSE for mAseff and image noise in the thorax region, and for mAseff (but not image noise) in the liver region. A post-hoc finding indicated that a subgroup of female patients with laterally protruding breasts was overexposed (+57% radiation dose) in the thorax region when using the AP localizer. Using LAT + AP localizer resulted in more consistent image noise levels and radiation doses compared to single AP localizer. The effect was small, except for the subgroup of females, where radiation doses were higher in the AP group. The findings are specific to the CT system used in this study and may not be generalizable to other CT models or software versions. Nonetheless, the proposed methodology provides a valuable approach for evaluating ATCM consistency.
Svalkvist A, Hultenmo M, Jonasson P
… +2 more, Sund P, Larsson M
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821436
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The optimization process is an important part of image-based diagnostics and treatments, requiring collaboration among medical physicists, radiologists, physicians, radiographers, nurses, engineers, and vendors. However,...The optimization process is an important part of image-based diagnostics and treatments, requiring collaboration among medical physicists, radiologists, physicians, radiographers, nurses, engineers, and vendors. However, such teamwork can be challenging in some departments. In spring 2024, questionnaires were sent to Swedish medical physicists working with radiology, interventional radiology, or surgery facilities using radiological equipment. The surveys included modality-specific questions about optimization processes. The aim was to explore differences in optimization processes between modalities and departments, identify common challenges, and understand factors facilitating effective optimization. Results showed variations in optimization processes across different modalities, where successful optimization processes were harder to achieve for stationary fluoroscopy systems and mobile fluoroscopy systems than for the other modalities. Common challenges included limited time and lack of knowledge about image quality issues, while close collaboration, continuous meetings with focus on optimization, and good communication were mentioned as important factors for obtaining successful optimization processes.
Magnusson M, Sandborg M, Carlsson Tedgren Å
… +1 more, Malusek A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821435
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Accurate computed tomography (CT) numbers derived from dual-energy CT (DECT) have numerous applications, including optimising the precision of radiation treatment planning. The dual-energy iterative reconstruction algori...Accurate computed tomography (CT) numbers derived from dual-energy CT (DECT) have numerous applications, including optimising the precision of radiation treatment planning. The dual-energy iterative reconstruction algorithm (DIRA) utilizes material decomposition in the iterative loop to generate monoenergetic images free of beam-hardening artifacts. In simulations, the reconstructed CT numbers closely matched reference tabulated values. This study evaluates the feasibility of applying DIRA to experimental data. Transitioning from simulations required several adaptations: (i) removal of the patient table, (ii) modeling of the bow-tie filter, and (iii) application of an inverse water beam-hardening correction. Axial scans of a cylindrical polymethyl methacrylate phantom containing four rod inserts of distinct materials were acquired using a clinical Siemens SOMATOM Force scanner. By the sixth iteration, DIRA yielded CT numbers that closely matched tabulated values. The algorithm also demonstrated strong performance on an anthropomorphic head phantom (Computerized Imaging Reference Systems, Inc. (CIRS) model 731-HN) with known material composition.
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821434
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Dental radiology accounts for 26% of all medical radiological examinations worldwide and 0.2% of the overall collective dose. The most common dental exposure is intraoral bitewing radiography, which is a procedure used t...Dental radiology accounts for 26% of all medical radiological examinations worldwide and 0.2% of the overall collective dose. The most common dental exposure is intraoral bitewing radiography, which is a procedure used to examine the interproximal surfaces of the teeth and is particularly useful for the detection of dental caries and the evaluation of alveolar bone levels. In Sweden, regulations require patients to have a 0.25 mm lead-equivalent thyroid shield during intraoral exposures. The aim of this project is to do a Monte Carlo simulation of the absorbed doses from a bitewing exposure and investigate the radiation protection effect of a lead collar. In this study, a Monte Carlo simulation was done of an intraoral bitewing examination, using the latest International Commission on Radiological Protection (ICRP) human adult mesh phantom. A thyroid collar was added to the mesh phantom to generate the exposure situation of a bitewing exposure. A 60 kV bitewing exposure was simulated using the Monte Carlo software MCNP6.3. The radiation source was simulated using RQR60 with 107 simulated X-ray photons. The simulations were performed both with and without thyroid collar. Absorbed doses were calculated for different organs and tissues in the ICRP adult mesh phantom. The results are calculated for a bitewing exposure with a tube voltage of 60 kV and an exposure time of 0.25 s on a phosphor plate receptor and 0.05 s for the digital sensors. The thyroid protection collar examined in this study did not significantly impact the absorbed dose to the thyroid. However, the absorbed dose to several other organs and tissues was reduced. The absorbed dose reduction was dependent on the distance to the X-ray primary beam, where a greater distance resulted in a greater reduction. The difference in effective dose between use of lead apron and without lead apron is, however, neglectable.
Malusek A, Malmodin S, Magnusson M
… +2 more, Sandborg M, Carlsson Tedgren Å
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821433
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Accurate elemental decomposition in dual-energy computed tomography (DECT) is crucial for precision in radiation therapy planning. We present a comparative study of linear regression and fully connected neural networks (...Accurate elemental decomposition in dual-energy computed tomography (DECT) is crucial for precision in radiation therapy planning. We present a comparative study of linear regression and fully connected neural networks (FCNNs) for voxel-wise prediction of tissue elemental composition, using synthetic datasets that incorporate realistic intra- and inter-patient variability. Both models performed well under noise-free conditions, with linear regression yielding slightly lower errors. Under noisy conditions, performance degraded for both models, though the linear model generally retained lower numerical error. The FCNNs, however, consistently produced physically plausible (non-negative) elemental mass-fraction estimates. These models are well suited for integration into model-based iterative reconstruction algorithms to support artificial intelligence-driven radiation treatment planning. Future work should incorporate elemental covariances and spatial context to enhance accuracy and clinical utility.
This investigation aimed to compare perceived lesion detectability and visibility between limited-angle cone-beam computed tomography (CBCT) photon-counting (PC) and flat-panel (FP) mammography at equivalent radiation-do...This investigation aimed to compare perceived lesion detectability and visibility between limited-angle cone-beam computed tomography (CBCT) photon-counting (PC) and flat-panel (FP) mammography at equivalent radiation-dose levels. Projection data were collected by rotating a lesion-containing, humanlike breast phantom and acquiring images at every other degree using both a PC and an FP system, resulting in 5-13 projections over an 8-24° angular range. Feldkamp-Davis-Kress (FDK) and simultaneous iterative reconstruction technique (SIRT) algorithms were used to reconstruct three-dimensional (3D) volumes for each system. A reader study evaluated lesion detectability and visibility in the 3D data. PC-CBCT showed better detectability and visibility of masses compared to FP-CBCT, with 90% sensitivity versus 70% and an area under the visual grading curve (AUCVGC) of 0.66-0.71 (P < .05). FDK image volumes demonstrated improved calcification visibility (P < .05) with PC-CBCT over FP-CBCT; however, for SIRT, calcification visibility was lower (AUCVGC = 0.46). This study emphasizes the need to reassess photon-counting in 3D mammography to improve lesion detection and visibility.
Accredited calibration laboratories operating under ISO/IEC 17025 must demonstrate compliance of their facilities with technical standards such as ISO 4037 when performing calibrations in gamma and X-ray fields, typicall...Accredited calibration laboratories operating under ISO/IEC 17025 must demonstrate compliance of their facilities with technical standards such as ISO 4037 when performing calibrations in gamma and X-ray fields, typically using ionization chambers as reference instruments. In this framework, the accurate determination of the air-kerma rate is a critical step to ensure both calibration reliability and international traceability in radiation protection dosimetry. This study reports a comparative evaluation of two ionization chambers with different geometries: the PTW 32002 (spherical, 1 L) and the PTW 23361 (cylindrical, 30 cm3). Both were employed to characterize 137Cs and 60Co reference radiation fields at the CNESTEN calibration laboratory. The experimental results were compared against a theoretical benchmark provided by Monte Carlo simulations using the MCNP6.1 code to perform a comparative study with the measured values. The aim was to verify the installation's compliance with the inverse square law and to assess the metrological suitability of the two detectors. The results showed overall agreement between experiment and simulation, with deviations ranging from ~0.2% to 10.5%, depending on photon energy and source-to-detector distance. The spherical PTW 32002 chamber demonstrated greater stability in 60Co beams, while the cylindrical PTW 23361 exhibited better accuracy in 137Cs fields. These findings highlight the importance of chamber selection with respect to photon energy and dose rate, and confirm the compliance of the CNESTEN facility with international standards, thereby supporting reduced uncertainties and improved metrological traceability in calibration services.
Recent Boron neutron capture therapy (BNCT) has shifted to accelerator-based systems. One of them is a compact neutron generator developed using silicon carbide (SiC) semiconductors by Fukushima SiC Applied Technology Co...Recent Boron neutron capture therapy (BNCT) has shifted to accelerator-based systems. One of them is a compact neutron generator developed using silicon carbide (SiC) semiconductors by Fukushima SiC Applied Technology Co. However, neutron penetration remains a critical challenge for treating deep-seated tumors. This study investigated the potential of neutron sieve therapy, originally developed to enhance the depth dose distribution in X-ray therapy, to improve BNCT dose distribution via Monte Carlo simulations based on the Fukushima SiC BNCT system. Dose distribution changes were investigated using polyethylene and 6LiF-plastic in block and sieve shapes. The results show that the maximum thermal neutron fluence depth was shallower (deeper) with polyethylene (6LiF-plastic) filters. The sieve filter moderately altered the dose distribution compared to the block filter due to density differences. The maximum dose point shifted 8 mm deeper using a sieve filter composed of 6LiF-plastic and polyethylene, with a 5.5% increase at 20 mm depth in neutron fluence at the same skin dose.