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.

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.

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.

BACKGROUND/AIM:Photon-counting detector computerised tomography (PCD-CT) is a novel imaging technique that may be beneficial in diagnostics and follow-up of pancreatic ductal adenocarcinoma (PDAC). PATIENTS AND METHODS:A prospective pilot including eight patients with confirmed PDAC was designed. Patients underwent conventional energy integrating detector CT (EID-CT) and PCD-CT, and corresponding arterial and venous phase images were compared in quantitative and qualitative manners. Five independent and method blinded reviewers scored each intra-individual pair of images. RESULTS:Quantitative assessment showed an advantage favouring PCD-CT in terms of signal to noise ratio (SNR) in aortic, pancreatic, and PDAC tissue (p=0.003, 0.001, and 0.040, respectively). There was a non-significant tendency towards better edge sharpness in the PCD-CT images. Qualitative assessments of image quality revealed minor differences in some aspects of arterial phase, favouring the conventional EID-CT, however no statistically significant differences in terms of overall or venous phase parameters between the methods were evident. CONCLUSION:PCD-CT offers a novel method with potential benefits in imaging of pancreatic tumours. Further development of the protocol, including optimisation and validation in larger cohorts of patients, are necessary to define a potential role of PCD-CT in the management of PDAC.

Non-linear properties of iterative reconstruction (IR) algorithms can alter image texture. We evaluated the effect of a model-based IR algorithm (advanced modelled iterative reconstruction; ADMIRE) and dose on computed tomography thorax image quality. Dual-source scanner data were acquired at 20, 45 and 65 reference mAs in 20 patients. Images reconstructed with filtered back projection (FBP) and ADMIRE Strengths 3-5 were assessed independently by six radiologists and analysed using an ordinal logistic regression model. For all image criteria studied, the effects of tube load 20 mAs and all ADMIRE strengths were significant (p < 0.001) when compared to reference categories 65 mAs and FBP. Increase in tube load from 45 to 65 mAs showed image quality improvement in three of six criteria. Replacing FBP with ADMIRE significantly improves perceived image quality for all criteria studied, potentially permitting a dose reduction of almost 70% without loss in image quality.

Introduction Low contrast resolution in abdominal computed tomography (CT) may be negatively affected by attempts to lower patient doses. Iterative reconstruction (IR) algorithms play a key role in mitigating this problem. The reconstructed slice thickness also influences image quality. The aim was to assess the interaction and influence of patient dose, slice thickness, and IR strength on image quality in abdominal CT. Method With a simultaneous acquisition, images at 42 and 98 mAs were obtained in 25 patients. Multiplanar images with slice thicknesses of 1, 2, and 3 mm and advanced modeled iterative reconstruction (ADMIRE) strengths of 3 (AD3) and 5 (AD5) were reconstructed. Four radiologists evaluated the images in a pairwise manner based on five image criteria. Ordinal logistic regression with mixed effects was used to evaluate the effect of tube load, ADMIRE strength, and slice thickness using the visual grading regression technique. Results For all assessed image criteria, the regression analysis showed significantly (p < 0.001) higher image quality for AD5, but lower for tube load 42 mAs, and slice thicknesses of 1 mm and 2 mm, compared to the reference categories of AD3, 98 mAs, and 3 mm, respectively. AD5 at 2 mm was superior to AD3 at 3 mm for all image criteria studied. AD5 1 mm produced inferior image quality for liver parenchyma and overall image quality compared to AD3 3 mm. Interobserver agreement (ICC) ranged from 0.874 to 0.920. Conclusion ADMIRE 5 at 2 mm slice thickness may allow for further dose reductions due to its superiority when compared to ADMIRE 3 at 3 mm slice thickness. Implications for practice Combination of thinner slices and higher ADMIRE strength facilitates imaging at low dose.

Background and purpose: Manual treatment planning for cervical brachytherapy is a challenging task; therefore, we investigated a method for inverse treatment planning using pseudo-structures to control the dwell distribution. Our hypothesis was that this method could produce treatment plans with a pear-shaped dose distribution and a high central dose, that comply with clinical constraints. Materials and methods: Data from 16 previously treated patients were used to compare three treatment planning methods: i) manual, ii) straightforward inverse, and iii) inverse with pseudo-structures. The treatment plans were compared using dose-volume histogram parameters and by analysing the dwell times, and the distribution of total reference air-kerma (TRAK) in the different parts of the applicator. Methods were evaluated in one treatment planning system and verified in a second treatment planning system. Results: The median dose to 90 % of the clinical tumor volume was 7.6 Gy, 7.8 Gy and 8.1 Gy for manual, pseudostructure and straightforward methods respectively. Distribution of TRAK for the different parts of the applicator for the three methods (manual, pseudo-structures, and straightforward), with combined intracavitary and interstitial treatments, were for vaginal part 39 %, 33 % and 15 %, for intra-uterine part 47 %, 50 % and 47 % and for interstitial part 13 %, 17 % and 38 % respectively. The results were similar in the second treatment planning system. Conclusion: The developed pseudo-structures worked as intended in shaping the dwell time distribution and in meeting the clinical constraints for both investigated treatment planning systems.

BACKGROUND:Accurate diagnostic imaging is crucial for managing facial fractures, which are a common global occurrence. This study aimed to compare the image quality of Photon Counting Detector CT (PCD-CT) with state-of-the-art Energy Integrating Detector CT (EID-CT) and intraoperative C-arm CBCT (CBCT) in visualizing maxillofacial anatomy using a cadaveric sheep head model. METHODS:Three fresh sheep heads were used, with surgical interventions simulating metal implants in two of them. The specimens were imaged using PCD-CT, EID-CT, and CBCT, following which quantitative assessments of signal-to-noise ratio, sharpness, and artifacts were conducted. A visual grading study was performed by six observers, using criteria focusing on the mandible, orbit, and soft tissues. Statistical analyses included Friedman tests for comparing modalities and Kendall's W and Gwet's AC1 for assessing inter- and intrarater agreement. RESULTS:PCD-CT demonstrated a significantly higher signal-to-noise ratio (p = 0.03) and bone sharpness (p < 0.001) compared to CBCT. In visual grading, PCD-CT outperformed CBCT, but not EID-CT, particularly in delineating mandibular and orbital structures. EID-CT and PCD-CT showed slightly more severe hypodense artifacts (p = 0.01) but were comparable in streak artifact presentation. The interrater and intrarater agreements indicated consistent evaluations across and within observers. CONCLUSION:PCD-CT exhibits superior image quality over CBCT in key parameters essential for maxillofacial imaging, while no apparent improvement was shown compared to state-of-the-art EID-CT. PCD-CT offers enhanced visualization of critical anatomical structures, suggesting its potential as a preferred modality in managing maxillofacial trauma. The findings in this study align with limited existing research on PCD-CT, underscoring its promise for advanced diagnostic imaging in maxillofacial applications.

Objectives: Images reconstructed with higher strengths of iterative reconstruction algorithms may impair radi-ologists' subjective perception and diagnostic performance due to changes in the amplitude of different spatial frequencies of noise. The aim of the present study was to ascertain if radiologists can learn to adapt to the unusual appearance of images produced by higher strengths of Advanced modeled iterative reconstruction al-gorithm (ADMIRE). Methods: Two previously published studies evaluated the performance of ADMIRE in non-contrast and contrast -enhanced abdominal CT. Images from 25 (first material) and 50 (second material) patients, were reconstructed with ADMIRE strengths 3, 5 (AD3, AD5) and filtered back projection (FBP). Radiologists assessed the images using image criteria from the European guidelines for quality criteria in CT. To ascertain if there was a learning effect, new analyses of data from the two studies was performed by introducing a time variable in the mixed -effects ordinal logistic regression model. Results: In both materials, a significant negative attitude to ADMIRE 5 at the beginning of the viewing was strengthened during the progress of the reviews for both liver parenchyma (first material:-0.70, p < 0.01, second material:-0.96, p < 0.001) and overall image quality (first material:-0.59, p < 0.05, second materi-al::-1.26, p < 0.001). For ADMIRE 3, an early positive attitude for the algorithm was noted, with no significant change over time for all criteria except one (overall image quality), where a significant negative trend over time (-1.08, p < 0.001) was seen in the second material.Conclusions: With progression of reviews in both materials, an increasing dislike for ADMIRE 5 images was apparent for two image criteria. In this time perspective (weeks or months), no learning effect towards accepting the algorithm could be demonstrated.

BACKGROUND:As guidelines endorse the use of computed tomography (CT) for examining coronary artery disease (CAD), it is important to compare the advantages and disadvantages of the novel photon counting detector CT (PCD-CT) technology with the established energy integrating detector CT (EID-CT).PURPOSE:To compare the image quality of coronary computed tomography angiography (CCTA) and the Agatston scores (AS) derived from EID-CT and PCD-CT.MATERIAL AND METHODS:In this prospective observational study, 28 patients underwent clinical calcium score and CCTA scans on an EID-CT and a PCD-CT scanner. CCTA images were qualitatively analyzed by five observers using visual grading characteristics. The correlation and agreement of the AS were assessed using Spearman's rank correlation and Bland-Altman plots.RESULTS:This qualitative analyses demonstrated a high fraction of "good" or "excellent" ratings for the image criteria in both CT systems. The sharpness of the distal lumen and image quality regarding motion artifacts were rated significantly higher for EID-CT (P < 0.05). However, the sharpness of coronary calcification was rated significantly higher for PCD-CT (P < 0.05). Spearman's rank correlation and Bland-Altman plots showed good correlation (P = 0.95) and agreement regarding the AS between EID-CT and PCD-CT.CONCLUSION:Both CT systems exhibited high CCTA image quality. The sharpness of calcifications was rated significantly higher for PCD-CT. A good correlation was observed between the AS derived from the two systems.

Background Bone strength is related to both mineral density (BMD) and the bone microstructure. However, only the assessment of BMD is available in clinical routine care today. Purpose To analyze and study the correlation of trabecular bone microstructure from the imaging data of a prototype Multitom Rax system, using micro-computed tomography (CT) data as the reference method (Skyscan 1176). Material and Methods Imaging data from 14 bone samples from the human radius were analyzed regarding six bone structure parameters, i.e. trabecular nodes, separation, spacing, and thickness as well as bone volume (BV/TV) and structural model index (SMI). Results All six structure parameters showed strong correlations to micro-CT with Spearman correlation coefficients in the range of 0.83–0.93. BV/TV and SMI had a correlation >0.90. Two of the parameters, namely, separation and number, had mean values in the same range as micro-CT. The other four were either over- or underestimated. Conclusion The strong correlation between micro-CT and the clinical imaging system, indicates the possibility for analyzing bone microstructure with potential to add value in fracture assessment using the studied device in a clinical workflow.

PURPOSE:The aim was to evaluate a postprocessing optimization algorithm's ability to improve the spatial properties of a clinical treatment plan while preserving the target coverage and the dose to the organs at risk.The goal was to obtain a more homogenous treatment plan, minimizing the need for manual adjustments after inverse treatment planning. MATERIALS AND METHODS:The study included 25 previously treated prostate cancer patients.The treatment plans were evaluated on dose-volume histogram parameters established clinical and quantitative measures of the high dose volumes.The volumes of the four largest hot spots were compared and complemented with a human observer study with visual grading by eight oncologists.Statistical analysis was done using ordinal logistic regression.Weighted kappa and Fleiss' kappa were used to evaluate intra-and interobserver reliability. RESULTS:The quantitative analysis showed that there was no change in planning target volume (PTV) coverage and dose to the rectum.There were significant improvements for the adjusted treatment plan in: V150% and V200% for PTV, dose to urethra, conformal index, and dose nonhomogeneity ratio.The three largest hot spots for the adjusted treatment plan were significantly smaller compared to the clinical treatment plan.The observers preferred the adjusted treatment plan in 132 cases and the clinical in 83 cases.The observers preferred the adjusted treatment plan on homogeneity and organs at risk but preferred the clinical plan on PTV coverage.CONCLUSIONS: Quantitative analysis showed that the postadjustment optimization tool could improve the spatial properties of the treatment plans while maintaining the target coverage.

Vascular x-ray guided interventions are complex and may result in high occupational doses to ionising radiation if staff do not take appropriate actions to minimise their exposure. In this prospective intervention study, ten staff members wore an extra personal dosimeter on the upper body above their regular protective clothing during four consecutive periods. Between each period either additional practical radiological protection training was given or a real-time direct display dosimeter were provided to the staff. Each staff's personal dose equivalent, Hp(10) normalised to the total air kerma-area product for the procedures where each staff were involved, KAPt, was used as the dependent variable. A focus-group interview with the staff were performed about the usefulness of the training and real-time dose rate display system. Our aim was to investigate if the interventions (practical training or real-time dose rate display) did affect the staff doses in the short and long term (five months later). Significant (p < 0.05) reductions of staff doses Hp(10)/KAPt were found after practical radiological protection training, but not after using real-time dose rate displays. Significant reductions were maintained after five months without additional interventions. The results from the focus-group interview indicated that making radiation 'visible', during practical training and usage of real-time direct display dosimeter, made it easier to understand how to act to lower occupational doses.

Abstract X-ray-guided interventions have increased in number and complexity. Mandatory radiological protection training includes both theoretical and practical training sessions. A recent additional training tool is real-time display dosemeters that give direct feedback to staff on their individual dose rates. Ten staff members who regularly perform pulmonary bronchoscopy wore an extra dosemeter during four 2-month periods. We controlled for the patient air kerma area product and the number of procedures in each period. Between periods 1 and 2, radiological training sessions were held and during period 3 the staff used the real-time display system. Focus-group interviews with the staff were held to obtain their opinion about learning radiological protection. We hypothesised that neither training nor the additional real-time dose rate display alters the personal dose equivalent, Hp(d); d = 0.07 and 10 mm. Useful experiences from radiological protection training were obtained, and median staff doses did decrease, however not significantly.

Automatic segmentation of bones in computed tomography (CT) images is used for instance in beam hardening correction algorithms where it improves the accuracy of resulting CT numbers. Of special interest are pelvic bones, which-because of their strong attenuation-affect the accuracy of brachytherapy in this region. This work evaluated the performance of the JJ2016 algorithm with the performance of MK2014v2 and JS2018 algorithms; all these algorithms were developed by authors. Visual comparison, and, in the latter case, also Dice similarity coefficients derived from the ground truth were used. It was found that the 3D-based JJ2016 performed better than the 2D-based MK2014v2, mainly because of the more accurate hole filling that benefitted from information in adjacent slices. The neural network-based JS2018 outperformed both traditional algorithms. It was, however, limited to the resolution of 1283 owing to the limited amount of memory in the graphical processing unit (GPU).