DOSESTAT-QC® is a stand-alone automated quality control (QC) system used for daily quality assurance of X-ray equipment in Jönköping Region, Sweden. The software has been implemented for all mammography systems and inter...DOSESTAT-QC® is a stand-alone automated quality control (QC) system used for daily quality assurance of X-ray equipment in Jönköping Region, Sweden. The software has been implemented for all mammography systems and interventional systems in the region. One of the image analysis included in the DOSESTAT-QC® software is performed in homogenous images and focuses on the standard deviations in mean pixel value (MV) and signal-to-noise ratio (SNR) in the images. Initially, the analyses were performed in 1 cm2 regions of interest (ROIs) and the obtained values in each ROI were compared to the corresponding values for the entire image. While MV remained relatively stable over time, fluctuations in SNR together with imprecise localization of pixel errors, especially in the automatic exposure control (AEC) area, highlighted limitations. In this paper, an improved method for image evaluation is presented, which enables precise SNR baseline settings and clear visualization of deviations and dead pixels. Additionally, the adaption and clinical implementation of DOSESTAT-QC® to conventional X-ray systems in the region are described.
Polymeri E, Johnsson ÅA, Enqvist O
… +9 more, Ulén J, Kindblom J, Braide K, Wiltz HJ, Tanyasiová M, Trägårdh E, Edenbrandt L, Kjölhede H, Svalkvist A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821468
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This study aimed to evaluate the clinical acceptability of artificial intelligence (AI)-based organ segmentations on pretreatment CT images of prostate cancer patients using manual organ delineations as a reference. Pair...This study aimed to evaluate the clinical acceptability of artificial intelligence (AI)-based organ segmentations on pretreatment CT images of prostate cancer patients using manual organ delineations as a reference. Paired AI-based segmentations and manual delineations of the prostate, urinary bladder, and rectum were evaluated by three observers, according to a 4-grade Likert-scale, based on quality criteria, developed through a Delphi process. Visual grading characteristics (VGC) analysis was performed. When comparing the ratings of AI-based (n = 360) and manual delineations (n = 360), the area under the VGC-curve (AUCVGC) was 0.36 (95% CI 0.27-0.44), 0.35 (95% CI 0.28-0.41), and 0.3 (95% CI 0.22-0.40) for the prostate, urinary bladder, and rectum, respectively, indicating inferior ratings for the algorithm. Few AI segmentations (8%) were considered clinically unacceptable, while in 67% no or minor changes were needed. Despite superior ratings for manual delineations, most AI-segmentations needed no or minor changes, indicating clinical acceptability.
Radiation protective drapes are sometimes placed on the patient during fluoroscopically guided procedures to reduce scattered radiation to medical personnel. However, there are concerns that these drapes may increase pat...Radiation protective drapes are sometimes placed on the patient during fluoroscopically guided procedures to reduce scattered radiation to medical personnel. However, there are concerns that these drapes may increase patient radiation dose due to backscattered radiation. In this study, thermoluminescent dosimeters (TLDs) were used to quantify backscattered radiation from three protective drapes, on top of and at different depths, in a polymethyl methacrylate (PMMA phantom). Monte Carlo simulations were also performed to theoretically quantify backscattered radiation from lead. The results showed that the backscattered radiation varied with the material of the drape and was less than a factor of 0.001 of the radiation dose from the primary radiation beam (including backscatter from the PMMA phantom). This minor increase in patient radiation dose does not need to be considered if the use of such drapes has been justified from an occupational radiation protection perspective.
Cone-beam computed tomography (CBCT) is widely used in radiology and radiotherapy, yet accurate dose assessment remains challenging due to wide X-ray beams, nonstandardized dosimetry protocols, and limited beam-collimati...Cone-beam computed tomography (CBCT) is widely used in radiology and radiotherapy, yet accurate dose assessment remains challenging due to wide X-ray beams, nonstandardized dosimetry protocols, and limited beam-collimation options. This study investigated a practical method for obtaining reference Computed Tomography Dose Index (CTDI) measurements on a CBCT system by introducing an external tungsten slit to generate a narrow beam compatible with the adopted dosimetry formalisms. Computed tomography air-kerma index measurements were performed using a 10-cm pencil ionization chamber, and dose-area product (DAP) values were obtained directly from the CBCT unit. The effective beam width was determined from projection images, and the system's geometric behaviour was characterized to support future modelling. A conversion factor between CTDI and DAP was derived for a head phantom, illustrating the feasibility and limitations of applying CTDI methodology to CBCT. The findings provide experimental data and geometric information that may support future Monte Carlo simulations and contribute to more standardized CBCT dose assessment.
Diniz MO, Johnsson ÅA, Norrlund RR
… +5 more, Vikgren J, Ramirez WC, Ku S, Båth M, Svalkvist A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821465
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To assess how computed tomography (CT) image reconstruction techniques affect perceived diagnostic image quality at varying radiation dose levels in chest imaging. A PBU-50 anthropomorphic phantom (small adult-sized mode...To assess how computed tomography (CT) image reconstruction techniques affect perceived diagnostic image quality at varying radiation dose levels in chest imaging. A PBU-50 anthropomorphic phantom (small adult-sized model) and an air-dried human lung specimen were scanned on the same CT system (Revolution Apex™, GE Healthcare) at six dose levels (CTDIvol) from 0.07 to 2.19 mGy for the smallest phantom size. Images were reconstructed using deep learning image reconstruction-high (DLIR-H), adaptive statistical iterative reconstruction at 40 per cent (ASiR-V), and filtered back projection (FBP). Five radiologists assessed anatomical reproduction, noise, artefacts, and diagnostic quality using ViewDEX. Descriptive statistics and visual grading characteristics analysis were used. In general, DLIR-H scored higher than ASiR-V and FBP. While maintaining image quality, DLIR-H allowed dose reduction compared to FBP. All methods were deemed acceptable for diagnosing pulmonary nodules, fibrosis, and peribronchial pathology. The results indicate that DLIR-H improves image quality in comparison to FBP and ASiR-V and may enable radiation dose reduction while maintaining clinical image quality.
This study evaluates radiation dose and risk in computed tomography angiography (CTA) of the carotid arteries by comparing a low-dose protocol with conventional settings. A total of 100 patients were included and equally...This study evaluates radiation dose and risk in computed tomography angiography (CTA) of the carotid arteries by comparing a low-dose protocol with conventional settings. A total of 100 patients were included and equally divided into two groups: 50 underwent scanning with 100 kV and 30 ml of contrast, and 50 with 120 kV and 100 ml. The low-dose protocol significantly reduced the effective dose and the estimated risk of exposure-induced death. Risk prediction was modelled using multiple linear regression: a pre-procedure model based on tube voltage, age, and sex, and a post-procedure model incorporating the volume CT air kerma index, which showed higher precision. These models enable individual risk estimation with or without dosimetric data. The findings support low-dose CTA for carotid imaging to minimize radiation risk while maintaining objective image-quality parameters, and they provide a practical approach to personalized risk assessment in stroke patients.
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821463
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In Sweden, the recommendation for intraoral X-ray exposure in dental radiology is that pregnant females should not use any extra protection than the mandatory thyroid lead collar. This recommendation is based on the know...In Sweden, the recommendation for intraoral X-ray exposure in dental radiology is that pregnant females should not use any extra protection than the mandatory thyroid lead collar. This recommendation is based on the knowledge that the dose to the fetus will be very low or negligible and therefore no extra protection is needed. However, we think it is important to test this recommendation using calculations based on the new International Commission on Radiological Protection (ICRP) phantoms for pregnant women. This project aims to do a Monte Carlo simulation of the absorbed dose distribution to a fetus at 25 weeks of pregnancy from a bitewing exposure, which is the most commonly used dental X-ray exposure. The project also aims to calculate the absorbed dose to organs and tissue in both the 25-week fetus and the pregnant mother. A lead collar, equivalent to 0.25 mm lead, was created and added to the ICRP pregnant mesh phantom with a 25-week male fetus. A 60 kV bitewing exposure was simulated using MCNP6.3. The radiation source was simulated using an RQR60 source and 10^7 photons. The fetal organ absorbed doses are calculated for a bitewing exposure with a tube voltage of 60 kV and an exposure time of 0.25 s for the phosphor plate receptor and 0.05 s for the digital sensors. The fetal organs that received the highest absorbed dose for phosphor plate were the brain 27 nGy; red bone marrow, 25 nGy; and bone endosteum, 25 nGy. The simulations show that the absorbed dose to the 25-week fetus is significantly reduced due to absorption by the tissue of the mother. In general, the fetus receives an absorbed dose that is 0.0015 of the mother's dose. For the 25-week fetus, the radiation exposure is low, and no extra protection is needed, e.g. covering the mother with a lead apron. These results could be of interest to the dentist, the physician, and the pregnant women before they agree to proceed with an intraoral dental exposure.
Achieving optimal image quality in computed tomography (CT) is essential for accurate diagnosis. This study explores the relationship between objective and subjective image quality, using the detectability index ($d^{\pr...Achieving optimal image quality in computed tomography (CT) is essential for accurate diagnosis. This study explores the relationship between objective and subjective image quality, using the detectability index ($d^{\prime}$) as a quantitative performance metric. A 3D-printed anthropomorphic abdominal phantom was used to assess how variations in tube voltage, current, slice thickness, and reconstruction kernel affect image quality. Signal-to-noise ratio, contrast-to-noise ratio, and edge sharpness were evaluated alongside radiologist assessments. A strong correlation between $d^{\prime}$ and subjective quality confirmed $d^{\prime}$ as a reliable predictor of visual image perception. Multiple linear regression identified $d^{\prime}$, object size, and the peak spatial frequency of the noise power spectrum as independent predictors of perceived quality. These results support the integration of $d^{\prime}$ into routine CT image quality evaluation, helping to align technical image parameters with clinical expectations and improve protocol optimization.
This study describes a practical and scalable preliminary method for optimizing paediatric chest X-ray examinations. The study was carried out in a large private healthcare network containing digital radiography and comp...This study describes a practical and scalable preliminary method for optimizing paediatric chest X-ray examinations. The study was carried out in a large private healthcare network containing digital radiography and computed radiography systems from multiple vendors. The aim was to achieve a harmonized dose optimization strategy consistent with the national diagnostic reference level and achievable dose level curves established by the Finnish Radiation and Nuclear Safety Authority in paediatric chest X-ray examinations. By using a reference device and calculating conversion factors for mAs normalization, similar or almost similar optimized exposure values could be applied to a wide range of systems. The method was proven to be effective, demonstrating its potential for broader implementation. Following this preliminary optimization, device-specific optimization should continue, particularly for equipment representing newer technology that enables further dose reduction.
Celander M, Krüger R, Peruzzi N
… +2 more, Aurumskjöld ML, Bech M
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821460
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The imaging capabilities of an in-house X-ray setup for micro computed tomography, consisting of a photon-counting detector and a liquid target source, are reported here. The effect of the finite X-ray source spot size o...The imaging capabilities of an in-house X-ray setup for micro computed tomography, consisting of a photon-counting detector and a liquid target source, are reported here. The effect of the finite X-ray source spot size on the image resolution is measured using the slanted edge method at different sample-to-detector distances, and the energy response of the detector is probed using clinically relevant contrast agents. The results show that the spatial resolution is limited to $12$ $\mu$m at large sample magnification. The energy resolution of the detector could not be estimated based on the present experiment and data analysis. The method used to measure the spatial resolution could be useful for research groups wanting to characterize similar X-ray setups.
Beta-amyloid positron emission tomography/computed tomography (PET/CT) with [18F]flutemetamol is used to demonstrate presence of Alzheimer's disease. With the possibility to use [18F]flutemetamol PET/CT for early detecti...Beta-amyloid positron emission tomography/computed tomography (PET/CT) with [18F]flutemetamol is used to demonstrate presence of Alzheimer's disease. With the possibility to use [18F]flutemetamol PET/CT for early detection of mild cognitive impairment and the development of prevention drugs, the demand for the procedure may increase significantly. The biokinetics and dosimetry of [18F]flutemetamol in 7 patients (62-73 y) were studied. Knee-to-head PET/CT scans were acquired 15 min, 1, 2, 3, 4, and 5 hours after intravenous injection of 185 MBq. Activity in blood samples and 20-hour urine was analyzed. Volumes of interest for organs with enhanced activity content were segmented in the PET-images. A biokinetic compartment model was created to derive time-activity data for different organs. Organ doses and effective dose were calculated using IDAC-Dose 2.1 in accordance with ICRP publication 103. The effective dose coefficient for [18F]flutemetamol was 21 μSv/MBq (4 mSv@185 MBq). The colon received highest absorbed dose, 17 mGy.
The use of portable computed tomography (PCT) in intensive care units (ICU) allows critically ill patients to undergo brain computed tomography examinations without the need for invasive intrahospital transportations. Th...The use of portable computed tomography (PCT) in intensive care units (ICU) allows critically ill patients to undergo brain computed tomography examinations without the need for invasive intrahospital transportations. The aim of this study was to determine the radiation doses around a PCT unit to establish routines for radiation protection. Scattered radiation was measured around a Siemens Somatom On.site PCT system during scans of anthropomorphic and computed tomography dose index (CTDI) phantoms. The ambient dose equivalents in the ICU were estimated by summing the dose contributions from all computed tomography scan locations. Results suggest that ~15 scans per week can be performed in an ICU with six to eight patient beds without exceeding the annual effective dose of 0.1 mSv to members of the public, while also maintaining personnel exposure below 1 mSv. These findings support the feasibility of integrating PCT use into the ICU workflow as a safer alternative to intrahospital transport for neuroimaging.
Magnusson M, Sandborg M, Carlsson Tedgren Å
… +1 more, Malusek A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821457
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Simultaneous quantification of two contrast agents in dual-energy CT (DECT) is promising for clinical diagnostics. This simulation study demonstrates that accurate estimation of iodine and gadolinium concentrations in un...Simultaneous quantification of two contrast agents in dual-energy CT (DECT) is promising for clinical diagnostics. This simulation study demonstrates that accurate estimation of iodine and gadolinium concentrations in unmixed aqueous solutions can be achieved using two-material decomposition and beam-hardening suppression with the dual-energy iterative reconstruction algorithm (DIRA). A simulated DECT imaging chain was used for evaluation. The phantom comprised a lipid cylinder containing five inserts filled with water, iodine (25 and 50 mg/mL), and gadolinium (25 and 50 mg/mL) solutions. X-ray projections at 80 and Sn140 kV were generated using Siemens' DRASIM code. DIRA was configured for two-material decomposition with water-bone, water-iodine, and water-gadolinium bases, and cylinder positions were manually defined during reconstruction. After approximately six iterations, accurate estimates of contrast agent mass fractions were obtained. These results confirm the feasibility of simultaneous iodine and gadolinium quantification in DECT and support further development toward a clinical application.
Khan J, Rydén T, van Essen M
… +4 more, Svensson J, Mehrara E, Båth M, Bernhardt P
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821456
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A power-law model was introduced to characterize the relationship between spherical volumes-of-interest (SVs) and whole kidney parenchyma (WKP)-derived absorbed dose estimates, enabling quantitative precision for image-b...A power-law model was introduced to characterize the relationship between spherical volumes-of-interest (SVs) and whole kidney parenchyma (WKP)-derived absorbed dose estimates, enabling quantitative precision for image-based dosimetry. Single photon emission computed tomography/computed tomography (SPECT/CT) images were acquired at 24, 48, and 168 h after [177Lu]Lu-DOTATATE treatment in 18 patients. Kidney activity was quantified using WKP and SV-based methods (2 and 0.6 ml) on SPECT-images. WKP and both SV approaches showed good agreement in kidney dosimetry, with normalization factors of 1.12 and 1.23 (standard error mean ≤1.2%), and improved precision when multiple SVs were used. The power-law model demonstrated excellent fit (R2 > 0.97) and high precision (~7%), with no significant difference between SV sizes (P = .15) and minimal bias (<0.003%). This power law model presents a novel method for quantifying the relative precision of SPECT-derived kidney dosimetry. Further validation is warranted to address residual uncertainty and complex noise correlation in the SV-based dose estimates.
Simkó A, Sund P, Mirzai M
… +4 more, Ivarsson J, Johnsson Å, Svalkvist A, Båth M
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821455
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Digital chest tomosynthesis refers to the 3D reconstruction of low-dose projection images acquired within a limited angular range. The reconstructions have lower depth resolution and are more prone to motion artifacts co...Digital chest tomosynthesis refers to the 3D reconstruction of low-dose projection images acquired within a limited angular range. The reconstructions have lower depth resolution and are more prone to motion artifacts compared to computed tomography (CT). While recent deep learning approaches aim to reconstruct full-resolution CT volumes from projections, they are computationally demanding due to the high resolution and inherently 3D nature of the task. In this study, we propose a more efficient alternative. Our deep learning-based framework reconstructs sagittal CT slices from small patches of projection data, significantly lowering memory demands. Rather than predicting continuous Houndsfield unit (HU) values, we segment voxels into air, soft tissue, or bone classes. Our results show that the method captures coarse structural features and depth information with high consistency, but struggles to reconstruct fine details. While not yet suitable for clinical deployment, the approach highlights a promising direction for low-resource tomosynthesis-based volumetric imaging.
Optimizing radiation dose while maintaining image quality remains a key challenge in computed tomography (CT). This study used a thorax-specific anthropomorphic phantom to assess patient dose, image quality, and artefact...Optimizing radiation dose while maintaining image quality remains a key challenge in computed tomography (CT). This study used a thorax-specific anthropomorphic phantom to assess patient dose, image quality, and artefact presence under automated tube current modulation settings and to evaluate the effect of tube voltage on Hounsfield Unit (HU) response for different iodine concentrations. Dose metrics, noise levels, and image quality indicators were extracted from Digital Imaging and Communications in Medicine (DICOM) metadata and image analysis. The study examined how patient positioning affects modulation performance and how tube voltage influences HU values in iodinated inserts. Results revealed inconsistencies in dose modulation across CT systems and highlighted the importance of synchronized protocols. A methodology was proposed to harmonize scanning protocols, ensuring consistent image quality and improved patient safety. These findings demonstrate the value of anthropomorphic phantoms in validating and optimizing CT protocols across clinical environments.
This paper outlines the development of the specialist medical physicist role in Sweden. Since introducing certification in 1999, the need for advanced expertise in patient safety, technology, optimization, and regulation...This paper outlines the development of the specialist medical physicist role in Sweden. Since introducing certification in 1999, the need for advanced expertise in patient safety, technology, optimization, and regulation became evident. In response, the Swedish Medical Physicist Association and the Swedish Society for Radiation Physics launched a national specialist training program in 2004, further refined in 2010. The program includes registration, clear competency goals, and supervision requirements and is endorsed by most Swedish hospitals. Following the EU Council Directive 2013/59/Euratom, Sweden committed to establishing the Medical Physics Expert role, prompting a proposed legislative amendment mandating specialist training in radiotherapy, radiology and nuclear medicine, and MRI, as this area is highly specialized within the expertise of Swedish medical physicists. This paper is meant to inspire similar initiatives internationally.
Pettersson E, Thilander Klang A, Gillies C
… +2 more, Clarke M, Bäck A
Radiat Prot Dosimetry
· 2026 Mar · PMID 41821452
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The efficacy of proton beam therapy is limited by stopping power ratio (SPR) prediction uncertainties in patient tissues. This study compared image artefacts and SPR prediction accuracy across a single-energy computed to...The efficacy of proton beam therapy is limited by stopping power ratio (SPR) prediction uncertainties in patient tissues. This study compared image artefacts and SPR prediction accuracy across a single-energy computed tomography (SECT) and three dual-energy computed tomography (DECT) workflows: SECT with a clinical Hounsfield look-up table (HLUT), two commercial DECT algorithms (DirectSPR and MMSim), and an in-house developed model applied to material density (MD) images, called MD-SPR. SPR images of a head-sized phantom with 24 inserts of tissue surrogate and non-tissue materials were evaluated for image artefacts and compared with measured reference SPRs of the inserts. The root-mean-square SPR differences for tissue surrogates were 0.011 (HLUT), 0.005 (DirectSPR), 0.007 (MMSim), and 0.005 (MD-SPR). For non-tissue materials, the differences were 0.167, 0.028, 0.034, and 0.011, respectively. These results indicate that DECT-based SPR prediction workflows, particularly MD-SPR, can reduce both image artefacts and range uncertainties, compared with a SECT-based HLUT workflow.
Technological advances in computed tomography (CT) have highlighted limitations of traditional dose descriptors such as computed tomography dose indexvol and dose-length product, particularly for wide-beam and modulated...Technological advances in computed tomography (CT) have highlighted limitations of traditional dose descriptors such as computed tomography dose indexvol and dose-length product, particularly for wide-beam and modulated acquisitions. This study investigates a CT-specific, operational air kerma-area product derived from time-resolved measurements using small solid-state dosemeters mounted at the gantry aperture. A mathematical framework is presented that accounts for tube rotation, bow-tie filtration, beam geometry, and the longitudinal dose profile. Model validation was performed using measured air-kerma rate waveforms under free-in-air and phantom conditions, demonstrating that a reproducible kerma-area quantity can be derived from fixed-detector measurements. By excluding the kerma-area contribution associated with radiation that does not intersect the object, the proposed approach yields a quantity that is more closely related to patient-incident radiation than conventional output-based KAP concepts in CT. The methodology provides a practical tool for system characterization and quality control in CT dosimetry.