Computed Tomography Scanning Parameters Research Articles

Intra‐arterial contrast enhanced computed tomography of the deep digital flexor tendon and palmar veins in the distal forelimb in Jeju horses: Evaluating contrast‐enhancing factors

AbstractBackgroundFew studies have investigated the adequate contrast enhancement (CE) evaluation depending on concentration, volume, and rate of administration of contrast media (CM) and the scan parameters in equine contrast enhanced computed tomography (CECT).ObjectivesTo investigate CE of the deep digital flexor tendon (DDFT) and veins depending on the computed tomography (CT) voltage and concentration, volume, and rate of CM administration during intra‐arterial CECT of equine distal forelimbs.Study DesignIn vivo experiments.MethodsSix horses underwent 54 CT scans. First, the CE of DDFT and veins was evaluated depending on the voltage (80 kV and 250 mA or 120 kV and 150 mA) and CM concentration (150, 120, or 90 mg I/mL in 50 mL of CM). Second, CE of DDFT and veins was evaluated depending on the CM volume (50, 100, or 150 mL) and administration rate (2, 4, or 6 mL/s) with a fixed iodine delivery rate (IDR; 300 or 180 mg I/s).ResultsContrast enhancement of DDFT was significantly higher at 80 kV of voltage and 150 mg I/mL of CM concentration (Median: 29.65; IQR: 1.74; p < 0.05). CE of the DDFT positively correlated with CM concentration (p < 0.001; r = 0.75). At 180 mg I/s IDR, contrast attenuation in the medial and lateral palmar veins significantly decreased at a CM of 30 mg I/mL, rate of 6 mL/s, and volume of 150 mL (median and IQR: 985.93 and 71.8 Hounsfield units [HU] and 988.73 and 41.16 HU, respectively); the CE was sufficient to distinguish between the vessels and the adjacent structures.Main LimitationsThe number of animals was small.ConclusionsOur results suggest that a low CM concentration could yield sufficient CE of the DDFT and arteries with adjusted CT scanning parameters or volume and injection rate of CM.

Task-based assessment for radiation dose optimization in CT abdominal examinations: A phantom study

Recent advancements in Computed Tomography (CT) imaging technology have significantly enhanced healthcare delivery. However, public concern regarding the safety and health risks associated with increased exposure to ionizing radiation has escalated. In response, this study performs a quantitative analysis comparing the image quality of the standard CT abdomen protocol (P1 protocols) with alternative optimization techniques. Adjustments to standard CT scan parameters, including tube potential (P2 protocols), effective mAs value (P3), and pitch factor (P4, P5, P6 protocols), were made to evaluate the effectiveness of these optimization strategies. A 64-slice CT scanner (Canon, Japan) and a polymethylmethacrylate (PMMA) textural water phantom was utilized in this study. CT dose descriptors, volume weighted CT Dose Index (CTDIvol) and dose-length product (DLP) alongside evaluation parameters such as Hounsfield Unit (HU) number, noise levels, Signal-to-Noise Ratio (SNR), and Contrast-to-Noise Ratio (CNR) were measured and analysed. Furthermore, this research introduced a Figure of Merit (FOM) based on the ratio of image quality parameters (SNR and CNR) to the CTDIvol, establishing a quantitative measure for optimization. A notable reduction in radiation dose—34.85% below the standard protocol (P1)—was observed in protocol P6, attributed to an increased pitch factor. Conversely, increase the effective mAs value has improved SNR and CNR values. The findings reveal that protocols P1 and P2 deliver the highest FOM for soft tissue and fat imaging, respectively. Protocol P1, with its higher attenuation factor, is optimal for abdominal examinations targeting soft tissues. Meanwhile, protocol P2's increase effective mAs value enhances beam intensity, improving CT numbers for fat tissues with their high-density composition. The study also found a strong correlation between FOM based on SNR and CNR values. In conclusion, adjustments to primary CT parameters significantly influence image quality. The FOM serves as an effective tool for measuring the overall performance of image quality, facilitating post-optimization assessment and contributing to the development of safer, more efficient CT imaging protocols.

Assessing the effect of scanning parameter on the size and density of pulmonary nodules: a phantom study

BackgroundLung cancer remains a leading cause of death among cancer patients. Computed tomography (CT) plays a key role in lung cancer screening. Previous studies have not adequately quantified the effect of scanning protocols on the detected tumor size. The aim of this study was to assess the effect of various CT scanning parameters on tumor size and densitometry based on a phantom study and to investigate the optimal energy and mA image quality for screening assessment.MethodsWe proposed a new model using the LUNGMAN N1 phantom multipurpose anthropomorphic chest phantom (diameters: 8, 10, and 12 mm; CT values: − 100, − 630, and − 800 HU) to evaluate the influence of changes in tube voltage and tube current on the size and density of pulmonary nodules. In the LUNGMAN N1 model, three types of simulated lung nodules representing solid tumors of different sizes were used. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were used to evaluate the image quality of each scanning combination. The consistency between the calculated results based on segmentation from two physicists was evaluated using the interclass correlation coefficient (ICC).ResultsIn terms of nodule size, the longest diameters of ground-glass nodules (GGNs) were closest to the ground truth on the images measured at 100 kVp tube voltage, and the longest diameters of solid nodules were closest to the ground truth on the images measured at 80 kVp tube voltage. In respect to density, the CT values of GGNs and solid nodules were closest to the ground truth when measured at 80 kVp and 100 kVp tube voltage, respectively. The overall agreement demonstrates that the measurements were consistent between the two physicists.ConclusionsOur proposed model demonstrated that a combination of 80 kVp and 140 mA scans was preferred for measuring the size of the solid nodules, and a combination of 100 kVp and 100 mA scans was preferred for measuring the size of the GGNs when performing lung cancer screening. The CT values at 80 kVp and 100 kVp were preferred for the measurement of GGNs and solid nodules, respectively, which were closest to the true CT values of the nodules. Therefore, the combination of scanning parameters should be selected for different types of nodules to obtain more accurate nodal data.

Diagnostic reference levels for common pediatric computed tomography studies: A retrospective study.

With the rapid increase in computed tomography (CT) examinations among pediatric patients, the concern about the effects of radiation exposure in this population has increased. Therefore, it is necessary to measure and regulate radiation exposure, which can be done using diagnostic reference levels (DRLs). This study aimed to calculate typical values for common pediatric studies at the radiology department of King Abdulaziz University Hospital Jeddah, Saudi Arabia. For a single institute, these are calculated as the median of computed tomography dose index (CTDIvol, mGy) or dose length product (DLP, mGy.cm) values. Pediatric patient data from January 2015 to December 2020 were collected, including CT examinations, dose descriptors, imaging protocols, and scanning parameters. A total of 8717 radiological studies were included in the sample. They were categorized into three age groups; more than half of the 5102 (58.5%) belonged to Group 1 (0–5 years), 1790 (20.5%) were in Group 2 (6–10 years), and 1826 (20.9%) were in Group 3 (11–15 years). Brain CT angiogram, non-enhanced brain CT, and Internal Auditory Canal (IAC) CT had the highest mean CTDI Vol and DLP, while virtual bronchoscopy contrast-enhanced chest and neck CT angiography had the lowest mean CTDI Vol. The values of DRLs in the current study were approximately lower than and comparable with those reported in other studies.

Aortic Valve Replacement: Understanding Predictors for the Optimal Ministernotomy Approach.

The most common minimally invasive approach for aortic valve replacement (AVR) is the partial upper mini-sternotomy. The aim of this study is to understand which preoperative computed tomography (CT) features are predictive of longer operations in terms of cardio-pulmonary bypass timesand cross-clamp times. From 2011 to 2022, we retrospectively selected 246 patients which underwent isolated AVR and had a preoperative ECG-gated CT scan. On these patients, we analysed the baseline anthropometric characteristics and the following CT scan parameters: aortic annular dimensions, valve calcium score, ascending aorta length, ascending aorta inclination and aorta-sternum distance. We identified augmented body surface area (>1.9 m2), augmented annular diameter (>23 mm), high calcium score (>2500 Agatson score) and increased aorta-sternum distance (>30 mm) as independent predictors of elongated operation times (more than two-fold). Identifying the preoperative predictive factors of longer operations can help surgeons select cases suitable for minimally invasive approaches, especially in a teaching context.

Evaluating the effects of variation in CT scanning parameters on the image quality and Hounsfield units for optimization of dose in radiotherapy treatment planning: A semi-anthropomorphic thorax phantom study

The diagnosis accuracy of computed tomography (CT) systems and the reliability of calculated Hounsfield Units (HUs) are critical in tumor detection and cancer patients' treatment planning. This study evaluated the effects of scan parameters (Kilovoltage peak or kVp, milli-Ampere-second or mAS reconstruction kernels and algorithms, reconstruction field of view, and slice thickness) on image quality, HUs, and the calculated dose in the treatment planning system (TPS). A quality dose verification phantom was scanned several times by a 16-slice Siemens CT scanner. The DOSIsoft ISO gray TPS was applied for dose calculations. The SPSS.24 software was used to analyze the results and the P-value <0.05 was considered significant. Reconstruction kernels and algorithms significantly affected noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). The noise increased and CNR decreased by raising the sharpness of reconstruction kernels. SNR and CNR had considerable increments at iterative reconstruction compared with the filtered back-projection algorithm. The noise decreased by raising mAS in soft tissues. Also, KVp had a significant effect on HUs. TPS--calculated dose variations were less than 2% for mediastinum and backbone and less than 8% for rib. Although HU variation depends on image acquisition parameters across a clinically feasible range, its dosimetric impact on the calculated dose in TPS can be neglected. Hence, it can be concluded that the optimized values of scan parameters can be applied to obtain the maximum diagnostic accuracy and calculate HUs more precisely without affecting the calculated dose in the treatment planning of cancer patients.

Multi-domain CT translation by a routable translation network

Objective. To unify the style of computed tomography (CT) images from multiple sources, we propose a novel multi-domain image translation network to convert CT images from different scan parameters and manufacturers by simply changing a routing vector. Approach. Unlike the existing multi-domain translation techniques, our method is based on a shared encoder and a routable decoder architecture to maximize the expressivity and conditioning power of the network. Main results. Experimental results show that the proposed CT image conversion can minimize the variation of image characteristics caused by imaging parameters, reconstruction algorithms, and hardware designs. Quantitative results and clinical evaluation from radiologists also show that our method can provide accurate translation results. Significance. Quantitative evaluation of CT images from multi-site or longitudinal studies has been a difficult problem due to the image variation depending on CT scan parameters and manufacturers. The proposed method can be utilized to address this for the quantitative analysis of multi-domain CT images.

INFLUENCE OF COMPUTED TOMOGRAPHY PARAMETERS ON THE RADIOTHERAPY PLAN CALCULATION

Contouring, planning and dose calculation in treatment planning systems (TPS) are based on computedtomography (CT) images. Therefore, it is important to have developed, optimized and adapted scanning protocolsfor specific anatomic regions and special radiotherapy modalities such as stereotactic radiosurgery (SRS). The aimof this study was to determine influence of tube voltage, field of view size (FOV) and reconstruction kernels on CTnumbers and the resulting radiotherapy (RT) dose calculation.This study was performed at Clinic of Oncology, Clinical Center University of Sarajevo. Verification electrondensity and CT number values was performed using CIRS Thorax 002LFC phantom, while anthropomorphic CIRS038 phantom for stereotactic end-to-end verification was used for the purpose of dose plan calculation analysis withlarge bore CT simulator Canon Aquillion LB.The significant correlation between the tube voltage and the measuredvalues of CT numbers is significant for all materials (p &lt; 0.05), except for water (p = 0.310). No significantcorrelation between FOV and obtained values of CT numbers was found in any of the evaluated tissue equivalentmaterials. Evaluating the impact of reconstruction kernels on Hounsfield units (HU), significant deviations werefound for the FC62, FC68 and FC07 reconstruction kernels. Also, analyzing the influence of reconstruction kernelson the RT dose calculation, the extreme values are associated with Dmin/D in PTV for kernels FC41 and FC68, wheredeviations from the values obtained using the baseline scanning parameters were -1.3% and -1.9%. For deviation of1 HU in muscle tissue of CIRS 002LFC, the calculated Dmin/D in PTV of CIRS STEEV phantom will reduce by0.79%. Similarly, the reduction of D₉₈ and D₂ would be 6.8 cGy and 3.03 cGy for 1 HU, respectively. Change of thereconstruction kernels caused differences of 0.4% in Dmin/D calculation in clinical target volume (CTV).CT scanning and reconstruction parameters may affect Hounsfield units, which could have an impact on dosecalculations in RT plan. Hence, it is recommended to standardize the scanning protocol used in calibration curvegeneration for TPS. One should avoid use of different tube voltages and kernels, while according to this study, thechange of FOV will have no impact on dose calculations

Adult Computed Tomography examinations in Uganda: Towards determining the National Diagnostic Reference Levels

IntroductionDiagnostic Reference Levels (DRLs), typically set at the 75th percentile of the dose distribution from surveys conducted across a broad user base using a specified dose-measurement protocol, are recommended for radiological examinations. There is a need to develop and implement DRLs as a standardisation and optimisation tool for the radiological protection of patients at Computed Tomography (CT) facilities.MethodsThis was a retrospective cross-sectional study conducted in seven (7) different CT scan facilities in which participants were recruited by systematic random sampling. The study variables were dose length product (DLP) and volume-weighted CTDI (CTDIvol) for the radiation doses for head, chest, abdomen and lumbar spine CT examinations. The DRLs for CTDIvol and DLP were obtained by calculating the 3rd quartiles of the radiation doses per study site by anatomical region. The national diagnostic reference levels were determined by computation of DRLs using the 75th centile of the median values.ResultsA total of 574 patients were examined with an average age of 47.1 years. For CTDIvol estimates; there was a strong positive significant relationship between the CTDIvol and examination mAs (rs = 0.9017, p-value < 0.001), and reference mAs (rs = 0.0.7708, p-value < 0.001). For DLP estimates; there was a moderate positive significant relationships between DLP and total mAs (rs = 0.6812, p-value < 0.001), reference mAs (rs = 0.5493, p-value < 0.001). The DRLs were as follows; for head CT scan – the average median CTDIvol was 56.02 mGy and the DLP was 1260.3 mGy.cm; for Chest CT, the CTDI volume was 7.82 mGy and the DLP was 377.0 mGy.cm; for the abdomen CT, the CTDI volume 12.54 mGy and DLP 1418.3 mGy.cm and for the lumbar spine 19.48 mGy and the DLP was 843 mGy.cm, respectively.ConclusionThis study confirmed the need to optimize the CT scan parameters in order to lower the national DRLs. This can be achieved by extensive training of all the CT scan radiographers on optimizing the CT scan acquisition parameters. Continuous dose audits are also advised with new equipment or after every three years to ensure that values out of range are either justified or further investigated.

Association of CT Scan Parameters with the Risk of Renal Angiomyolipoma Rupture; a Brief Report.

Introduction:Rupture of renal angiomyolipoma (AML) is an emergency and life-threatening complication. This study aimed to evaluate the association of computed tomography (CT) scan parameters with the risk of rupture in renal AMLs.Methods:In this retrospective cross-sectional study, patients who were referred to a referral university hospital with diagnosis of AML, between 2007 and 2019, were included. Patients were divided into ruptured and non-ruptured cases based on surgery and CT scan findings and the baseline characteristics as well as CT scan parameters were compared between the two groups.Results:20 AML patients with the mean age of 39.6 ± 12.5 years were included (75% female). The lesion was ruptured in 8 (40%) patients. The mean size of the lesion was ‎97.0 ± 15.9 mm‎‏ in the ruptured and ‏‎72.0 ± 29.4‎‏ in the non‎-‎ruptured AML ‏‎(‎p ‎= ‎‏0.045). The ‎mean fat density based on non-contrast enhanced CT (NCCT) scan (-‎56.1 ± 16.3 ‎vs ‎-‎‎74.9±24.1; ‏p = ‏‎0.018) and contrast enhanced CT (CECT) scan (-‎20.8 ± 16.9 ‎vs ‎-‎‎50.5 ± 31.7; ‏p ‏= ‏‎0.‎016) was significantly higher in the ruptured cases. Total tumor density based on NCCT scan was significantly greater in the ruptured ‎AMLs ‏(‏‎19.6 ± 25.9 ‎‏ vs‎ ‎-22.7±41.6, p=0.033). Conclusion:It seems that some CT scan parameters such as mean fat density and ‎total tumor density ‏could be used for differentiation between ruptured and non-ruptured AMLs.

Intraoperative Chertsey Test, is it a Reliable Alternative to Computed Tomography Scan for Diagnosing Syndesmotic Injuries of the Ankle?

Background:The present study aims to evaluate the diagnostic exactitude of the intraoperative Chertsey test in tibiofibular syndesmotic injuries in patients with malleolar fractures, in comparison with a computed tomography (CT) scan.Materials and Methods:In this study, patients with malleolar fractures operated between 2018 and 2020 were examined. Thirty-nine patients were enrolled in the study. A three-dimensional preoperative CT scan was obtained. The opposite unfractured ankle was also scanned and considered as the control group. The Chertsey test was performed during the operation to assess the syndesmosis injury. Then, patients were partitioned into two distinct groups, considering the condition of their ankle, namely the Chertsey positive (unstable syndesmosis) group and the Chertsey negative (stable syndesmosis) group.Results:The outcomes of the present survey illustrated that the Chertsey test was positive in 16 patients (41.03%) and negative in 23 patients (59.07%). The median of all CT scan parameters (anterior tibiofibular distances (TFD), middle TFD, posterior TFD, and maximal TFD and volume) before surgery in the group of patients with a positive Chertsey test was significantly higher, measured against the unfractured control group (P < 0.001 for all parameters). Furthermore, a comparison of CT scan parameters and syndesmosis space volume before surgery between the two groups of patients with positive and negative Chertsey test results showed that the measurement of parameters in Chertsey-positive patients was significantly higher than the Chertsey-negative patients (P < 0.001).Conclusion:Chertsey test could be used to diagnose syndesmosis injuries in patients with malleolar fractures due to its high importance in the outcome of patients.

A Quarter-split Domain-adaptive Network for EGFR Gene Mutation Prediction in Lung Cancer by Standardizing Heterogeneous CT image.

Epidermal growth factor receptor (EGFR) gene mutation status is crucial for the treatment planning of lung cancer. The gold standard for detecting EGFR mutation status relies on invasive tumor biopsy and expensive gene sequencing. Recently, computed tomography (CT) images and deep learning have shown promising results in non-invasively predicting EGFR mutation in lung cancer. However, CT scanning parameters such as slice thickness vary largely between different scanners and centers, making the deep learning models very sensitive to noise and therefore not robust in clinical practice. In this study, we propose a novel QuarterNetadaptive model to predict EGFR mutation in lung cancer, which is robust to CT images of different thicknesses. We propose two components: 1) a quarter-split network to sequentially learn local lung features from different lung lobes and global lung features; 2) a domain adaptive strategy to learn CT thickness-invariant features. Furthermore, we collected a large dataset including 1413 patients with both EGFR gene sequencing and CT images of various thicknesses to evaluate the performance of the proposed model. Finally, the QuarterNetadaptive model achieved AUC over 0.88 regarding CT images of different thicknesses, which improves largely than state-of-the-art methods.Clinical relevance-We proposed a non-invasive model to detect EGFR gene mutation in lung cancer, which is robust to CT images of different thicknesses and can assist lung cancer treatment planning.

Association of Craniofacial and Upper Airway Morphology with Cardiovascular Risk in Adults with OSA.

Background and ObjectiveClinical and population-based studies have demonstrated a strong association between obstructive sleep apnea (OSA) and cardiovascular disease (CVD). Anatomical abnormalities of the craniofacial region and upper airway are important risk factors for OSA. The objective of this study was to investigate the association of craniofacial and upper airway morphology with CVD risk biomarkers.MethodsOne hundred and sixty-nine male patients with OSA underwent in-laboratory polysomnography (PSG) and upper airway computed tomography (CT) scanning. Ten-year Framingham CVD risk score (FRS) was calculated and categorized into low- and moderate-to-high-risk groups. N-terminal pro B-type natriuretic peptide (NT-proBNP) was measured as a biomarker of increased myocardial wall stress.ResultsCompared to the low-risk group, total sleep time (TST), the proportion of N3 (N3%) and mean oxygen saturation (SpO2mean) were lower, while the arousal index of non-rapid eye movement (NREM) sleep, apnea index (AI) of NREM sleep, apnea hypopnea index (AHI) of NREM sleep, oxygen desaturation index (ODI) and percentage of total sleep time spent with oxyhemoglobin saturation below 90% (TST90) were higher in the moderate-to-high risk group. The corrected upper airway length (UAL), ANB angle and gonion-gnathion-hyoid angle were larger for subjects in the moderate-to-high risk group than those in the low-risk group. In multiple regression analysis, TST, AINREM and adjusted UAL were independently associated with moderate-to-high CVD risk. Plasma NT-proBNP levels were higher in patients in the moderate- to high-risk group, and among the PSG and CT scan parameters, only SPO2mean was marginally associated with NT-proBNP (r=0.183, P=0.054).ConclusionCraniofacial and upper airway features may contain valid cues about CVD risk, and sleep duration, obstructive event type and occurrence phase may be closely related to CVD risk for patients with OSA.

Estimating Organ Doses from Pediatric Cerebral Computed Tomography Using the WAZA-ARI Web-Based Calculator

Background: The use of computed tomography (CT) device has increased in the past few decades in Japan. Dose optimization is strongly required in pediatric CT examinations, since there is concern that an unreasonably excessive medical radiation exposure might increase the risk of brain cancer and leukemia. To accelerate the process of dose optimization, continual assessment of the dose levels in actual hospitals and medical facilities is necessary. This study presents organ dose estimation using pediatric cerebral CT scans in the Kyushu region, Japan in 2012 and the web-based calculator, WAZA-ARI (https://waza-ari.nirs.qst.go.jp). Materials and Methods: We collected actual patient information and CT scan parameters from hospitals and medical facilities with more than 200 beds that perform pediatric CT in the Kyushu region, Japan through a questionnaire survey. To estimate the actual organ dose (brain dose, bone marrow dose, thyroid dose, lens dose), we divided the pediatric population into five age groups (0, 1, 5, 10, 15) based on body size, and inputted CT scan parameters into WAZA- ARI. Results and Discussion: Organ doses for each age group were obtained using WAZA-ARI. The brain dose, thyroid dose, and lens dose were the highest in the Age 0 group among the age groups, and the bone marrow and thyroid doses tended to decrease with increasing age groups. All organ doses showed differences among facilities, and this tendency was remarkable in the young group, especially in the Age 0 group. This study confirmed a difference of more than 10- fold in organ doses depending on the facility and CT scan parameters, even when the same CT device was used in the same age group. Conclusion: This study indicated that organ doses varied widely by age group, and also suggested that CT scan parameters are not optimized for children in some hospitals and medical facilities.

Correlation of Computed Tomography Parameters with Histology, Stage and Prognosis in Surgically Treated Thymomas.

Background and objectives: The histological classification and staging of thymic tumors remains a matter of debate. The correlation of computed tomography (CT) parameters with tumor histology and stage also still has to be completely assessed. The aim of this study was therefore to analyze the correlation of radiological parameters with histological and staging classifications of thymomas evaluating their prognostic role. Materials and Methods: Data of 50 patients with thymoma submitted to a complete surgical treatment between 2005 and 2015 were retrospectively analyzed. Tumors were classified according to the WHO and Suster and Moran (S&M) histological classifications and to the Masaoka–Koga and tumor, node and metastases (TNM) staging systems. The correlation of CT features with histology and stage and the prognostic role of histopathological and radiological features were assessed. Results: Five-year overall (OS) and disease-free survival (DFS) were 90.3% and 81.1%, respectively. A significant correlation of DFS with the Masaoka–Koga (p = 0.001) and TNM staging systems (p = 0.002) and with the S&M (p = 0.02) and WHO histological classifications (p = 0.04) was observed. CT scan features correlated with tumor stage, histology and prognosis. Moderately differentiated tumors (WHO B3) had a significantly higher incidence of irregular shape and contours (p = 0.002 and p = 0.001, respectively) and pericardial contact (p = 0.036). A larger tumor volume (p = 0.03) and a greater length of pleural contact (p = 0.04) adversely influenced DFS. The presence of pleural (p < 0.001) or lung invasion (p = 0.02) and of pleural effusion (p = 0.004) was associated with a significantly worse OS. Conclusions: Pre-operative CT scan parameters correlate with stage and histology, and have a prognostic role in surgically treated thymomas.

EVALUATION OF ORGAN DOSE BASED ON PATIENT DATA IN EAST ASIAN DESCENT PEDIATRIC HEAD CT EXAMINATIONS.

The purpose of this study was to investigate other indices estimating absorbed dose for eye lens and brain, using clinical images of East Asian pediatric patients. We simulated head computed tomography (CT ) examinations in 104 pediatric patients. Effective diameter (deff) and water equivalent diameter (dw) were measured on clinical images. Various size metrics and age were compared with absorbed dose normalised by CTDIvol (nD). The nD was estimated for eye and brain. The nD tended to decrease with advancing age. R2 between age and nD were 0.38 and 0.31 for eye and brain, respectively. Increasing head diameters decreased each nD. R2 between deff and dw, and nD were 0.20-0.24 and 0.51-0.53 for eye and brain, respectively. Head sizes allowed us to estimate absorbed dose in brain CT on East Asian pediatric patients. Scanning parameters for pediatric head CT may need to be based on individual patient information.

Correlation analysis of organ doses determined by Monte Carlo simulation with dose metrics for patients undergoing chest-abdomen-pelvis CT examinations

ObjectivesThis study aimed to determine organ doses based on Monte Carlo (MC) simulations for individual patients undergoing routine adult chest abdomen-pelvis computed tomography (CT) examinations and to evaluate the correlations of organ doses with patient size and dose metrics. MethodsMC simulations were performed by reading detailed descriptions of the CT scanner, scanning parameters, and CT images of phantoms and patients into the simulation software. The simulation models were validated by comparing the simulated doses with the doses measured by in-phantom dosimetry using radiophotoluminescent glass dosimeters and an adult anthropomorphic phantom, and organ doses for 80 patients were determined from the simulation results. To obtain patient size and dose metrics, body mass index and volume computed tomography dose index (CTDIvol) data were collected. Water equivalent diameter (WED) was calculated from the CT images of each patient. Size-specific dose estimates (SSDE) were calculated using CTDIvol and average WED over the scan range, and organ specific SSDE were calculated using the average CTDIvol and WED over each organ position. The correlations of organ doses with dose metrics were evaluated using coefficients of determination. ResultsOrgan doses increased with patient size, and the doses for obese were approximately two to three times higher than those for underweight patients. Organ doses exhibited stronger linear relationships with organ specific SSDE (R2 ≥ 0.82) than other dose metrics. ConclusionsThe linear regression fits between organ doses determined by MC simulation and organ-specific SSDE are valuable for simplified and accurate organ dose estimation for individual patients undergoing CT examinations.

Optimisation of CT scan parameters to increase the accuracy of gross tumour volume identification in brain radiotherapy

AbstractAim:This study aimed to optimise computed tomography (CT) simulation scan parameters to increase the accuracy for gross tumour volume identification in brain radiotherapy. For this purpose, high-contrast scan protocols were assessed.Materials and methods:A CT accreditation phantom (ACR Gammex 464) was used to optimise brain CT scan parameters on a Toshiba Alexion 16-row multislice CT scanner. Dose, tube voltage, tube current–time and CT dose index (CTDI) were varied to create five image quality enhancement (IQE) protocols. They were assessed in terms of contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and noise level and compared with a standard clinical protocol. Finally, the ability of the selected protocols to identify low-contrast objects was examined based on a subjective method.Results:Among the five IQE protocols, the one with the highest tube current–time product (250 mA) and lowest tube voltage (100 kVp) showed higher CNR, while another with a tube current–time product of 150 mA and a tube voltage of 135 kVp had improved SNR and lower noise level compared to the standard protocol. In contouring low-contrast objects, the protocol with the highest milliampere and lowest peak kilovoltage exhibited the lowest error rate (1%) compared to the standard protocol (25%).Findings:CT image quality should be optimised using the high-dose parameters created in this study to provide better soft tissue contrast. This could lead to an accurate identification of gross tumour volume recognition in the planning of radiotherapy treatment.

Future of Diagnostic Computed Tomography

Iodinated contrast media (CM) are utilized in approximately 40% of the 300 million computed tomography (CT) scans undertaken annually. This review focuses on the physicochemical properties and safety of iodinated CM, and the development of new x-ray CM, and it explores methods to optimize CT scanning parameters. It concludes that good x-ray CM should have high structural stability, hydrophilicity, and CT attenuation; low viscosity, osmolality, and protein binding; no metabolism and tissue accumulation; and a complete elimination.

Development of a CT number calibration audit phantom in photon radiation therapy: A pilot study.

PurposeIn photon radiation therapy, computed tomography (CT) numbers are converted into values for mass density (MD) or relative electron density to water (RED). CT‐MD or CT‐RED calibration tables are relevant for human body dose calculation in an inhomogeneous medium. CT‐MD or CT‐RED calibration tables are influenced by patient imaging (CT scanner manufacturer, scanning parameters, and patient size), the calibration process (tissue‐equivalent phantom manufacturer, and selection of tissue‐equivalent material), differences between tissue‐equivalent materials and standard tissues, and the dose calculation algorithm applied; however, a CT number calibration audit has not been established. The purposes of this study were to develop a postal audit phantom, and to establish a CT number calibration audit process.MethodsA conventional stoichiometric calibration conducts a least square fit of the relationships between the MD, material weight, and measured CT number, using two parameters. In this study, a new stoichiometric CT number calibration scheme has been empirically established, using three parameters to harmonize the calculated CT number with the measured CT number for air and lung tissue. In addition, the suitable material set and the minimal number of materials required for stoichiometric CT number calibration were determined. The MDs and elemental weights from the International Commission on Radiological Protection Publication 110 were used as standard tissue data, to generate the CT‐MD and CT‐RED calibration tables. A small‐sized, CT number calibration phantom was developed for a postal audit, and stoichiometric CT number calibration with the phantom was compared to the CT number calibration tables registered in the radiotherapy treatment planning systems (RTPSs) associated with five radiotherapy institutions.ResultsWhen a least square fit was performed for the stoichiometric CT number calibration with the three parameters, the calculated CT number showed better agreement with the measured CT number. We established stoichiometric CT number calibration using only two materials because the accuracy of the process was determined not by the number of used materials but by the number of elements contained. The stoichiometric CT number calibration was comparable to the tissue‐substitute calibration, with a dose difference less than 1%. An outline of the CT number calibration audit was demonstrated through a multi‐institutional study.ConclusionsWe established a new stoichiometric CT number calibration method for validating the CT number calibration tables registered in RTPSs. We also developed a CT number calibration phantom for a postal audit, which was verified by the performances of multiple CT scanners located at several institutions. The new stoichiometric CT number calibration has the advantages of being performed using only two materials, and decreasing the difference between the calculated and measured CT numbers for air and lung tissue. In the future, a postal CT number calibration audit might be achievable using a smaller phantom.