Radiation dose and image quality inK-edge subtraction computed tomography of lungin vivo

2014 ◽  
Vol 21 (6) ◽  
pp. 1305-1313 ◽  
Author(s):  
S. Strengell ◽  
J. Keyriläinen ◽  
P. Suortti ◽  
S. Bayat ◽  
A. R. A. Sovijärvi ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Radiation Dose ◽  
Signal To Noise Ratio ◽  
Regional Distribution ◽  
Lung Ventilation ◽  
Structural Features ◽  
Reconstruction Algorithms ◽  
Human Thorax

K-edge subtraction computed tomography (KES-CT) allows simultaneous imaging of both structural features and regional distribution of contrast elements inside an organ. Using this technique, regional lung ventilation and blood volume distributions can be measured experimentallyin vivo. In order for this imaging technology to be applicable in humans, it is crucial to minimize exposure to ionizing radiation with little compromise in image quality. The goal of this study was to assess the changes in signal-to-noise ratio (SNR) of KES-CT lung images as a function of radiation dose. The experiments were performed in anesthetized and ventilated rabbits using inhaled xenon gas in O2at two concentrations: 20% and 70%. Radiation dose, defined as air kerma (Ka), was measured free-in-air and in a 16 cm polymethyl methacrylate phantom with a cylindrical ionization chamber. The dose free-in-air was varied from 2.7 mGy to 8.0 Gy. SNR in the images of xenon in air spaces was above the Rose criterion (SNR > 5) whenKawas over 400 mGy with 20% xenon, and over 40 mGy with 70% xenon. Although in human thorax attenuation is higher, based on these findings it is estimated that, by optimizing the imaging sequence and reconstruction algorithms, the radiation dose could be further reduced to clinically acceptable levels.

Image quality in coronary computed tomography angiography: influence of adaptive statistical iterative reconstruction at various radiation dose levels

2018 ◽  
Vol 59 (10) ◽  
pp. 1194-1202 ◽  
Author(s):  
Helle Precht ◽  
Oke Gerke ◽  
Jesper Thygesen ◽  
Kenneth Egstrup ◽  
Søren Auscher ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Radiation Dose ◽  
Iterative Reconstruction ◽  
Quality Criteria ◽  
Left Ventricular ◽  
Reconstruction Algorithms ◽  
Adaptive Statistical Iterative Reconstruction ◽  
Low Contrast ◽  
Statistical Iterative Reconstruction

Background Computed tomography (CT) technology is rapidly evolving and software solution developed to optimize image quality and/or lower radiation dose. Purpose To investigate the influence of adaptive statistical iterative reconstruction (ASIR) at different radiation doses in coronary CT angiography (CCTA) in detailed image quality. Material and Methods A total of 160 CCTA were reconstructed as follows: 55 scans with filtered back projection (FBP) (650 mA), 51 scans (455 mA) with 30% ASIR (ASIR30), and 54 scans (295 mA) with 60% ASIR (ASIR60). For each reconstruction, subjective image quality was assessed by five independent certified cardiologists using a visual grading analysis (VGA) with five predefined image quality criteria consisting of a 5-point scale. Objective measures were contrast, noise, and contrast-to-noise ratio (CNR). Results The CTDIvol resulted in 10.3 mGy, 7.4 mGy, and 4.6 mGy for FBP, ASIR30, and ASIR60, respectively. Homogeneity of the left ventricular lumen was the sole aspect in which reconstruction algorithms differed with a decreasing effect for ASIR60 compared to FBP (estimated odds ratio [OR] = 0.49 [95% confidence interval (CI) = 0.32–0.76; P = 0.001]). Decreased sharpness and spatial- and low-contrast resolutions were observed when using ASIR instead of FBP, but differences were not statistically significant. Concerning objective measurements, noise increased significantly for ASIR30 (OR = 1.08; 95% CI = 1.02–1.14; P = 0.006) and ASIR60 (OR = 1.06; 95% CI = 1.01–1.12; P = 0.034) compared to FBP. Conclusion ASIR significantly decreased the subjectively assessed homogeneity of the left ventricular lumen and increased the objectively measured noise compared to FBP. Considering these results, ASIR at a reduced radiation dose should be implemented with caution.

scholarly journals Simulated Annealing-Based Image Reconstruction for Patients With COVID-19 as a Model for Ultralow-Dose Computed Tomography

2022 ◽  
Vol 12 ◽  
Author(s):  
Shahzad Ahmad Qureshi ◽  
Aziz Ul Rehman ◽  
Adil Aslam Mir ◽  
Muhammad Rafique ◽  
Wazir Muhammad
Keyword(s):  
Computed Tomography ◽  
Simulated Annealing ◽  
Image Reconstruction ◽  
Image Quality ◽  
Radiation Dose ◽  
Signal To Noise Ratio ◽  
Absolute Error ◽  
Signal To Noise ◽  
X Ray ◽  
Squared Error

The proposed algorithm of inverse problem of computed tomography (CT), using limited views, is based on stochastic techniques, namely simulated annealing (SA). The selection of an optimal cost function for SA-based image reconstruction is of prime importance. It can reduce annealing time, and also X-ray dose rate accompanying better image quality. In this paper, effectiveness of various cost functions, namely universal image quality index (UIQI), root-mean-squared error (RMSE), structural similarity index measure (SSIM), mean absolute error (MAE), relative squared error (RSE), relative absolute error (RAE), and root-mean-squared logarithmic error (RMSLE), has been critically analyzed and evaluated for ultralow-dose X-ray CT of patients with COVID-19. For sensitivity analysis of this ill-posed problem, the stochastically estimated images of lung phantom have been reconstructed. The cost function analysis in terms of computational and spatial complexity has been performed using image quality measures, namely peak signal-to-noise ratio (PSNR), Euclidean error (EuE), and weighted peak signal-to-noise ratio (WPSNR). It has been generalized for cost functions that RMSLE exhibits WPSNR of 64.33 ± 3.98 dB and 63.41 ± 2.88 dB for 8 × 8 and 16 × 16 lung phantoms, respectively, and it has been applied for actual CT-based image reconstruction of patients with COVID-19. We successfully reconstructed chest CT images of patients with COVID-19 using RMSLE with eighteen projections, a 10-fold reduction in radiation dose exposure. This approach will be suitable for accurate diagnosis of patients with COVID-19 having less immunity and sensitive to radiation dose.

High-quality low-dose cardiovascular computed tomography (CCT) in pediatric patients using a 64-slice scanner

2018 ◽  
Vol 59 (10) ◽  
pp. 1247-1253 ◽  
Author(s):  
Paola Maria Cannaò ◽  
Francesco Secchi ◽  
Marco Alì ◽  
Ida Daniela D'Angelo ◽  
Marco Scarabello ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Radiation Dose ◽  
Effective Dose ◽  
Low Dose ◽  
Signal To Noise Ratio ◽  
High Quality ◽  
Dose Length Product ◽  
Noise Ratio ◽  
Estimate Radiation Dose

Background Cardiovascular computed tomography (CCT) technology is rapidly advancing allowing to perform good quality examinations with a radiation dose as low as 1.2 mSv. However, latest generation scanners are not available in all centers. Purpose To estimate radiation dose and image quality in pediatric CCT using a standard 64-slice scanner. Material and Methods A total of 100 patients aged 6.9 ± 5.4 years (mean ± standard deviation) who underwent a 64-slice CCT scan using 80, 100, or 120 kVp, were retrospectively evaluated. Radiation effective dose was calculated on the basis of the dose length product. Two independent readers assessed the image quality through signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and a qualitative score (3 = very good, 2 = good, 1 = poor). Non-parametric tests were used. Results Fifty-five exams were not electrocardiographically (ECG) triggered, 20 had a prospective ECG triggering, and 25 had retrospective ECG triggering. The median effective dose was 1.3 mSv (interquartile range [IQR] = 0.8–2.7 mSv). Median SNR was 30.6 (IQR = 23.4–33.6) at 120 kVp, 29.4 (IQR = 23.7–34.8) at 100 kVp, and 24.7 (IQR = 19.4–34.3) at 80 kVp. Median CNR was 21.0 (IQR = 14.8–24.4), 19.1 (IQR = 15.6–23.9), and 25.3 (IQR = 19.4–33.4), respectively. Image quality was very good, good, and poor in 56, 39, and 5 patients, respectively. No significant differences were found among voltage groups for SNR ( P = 0.486), CNR ( P = 0.336), and subjective image quality ( P = 0.296). The inter-observer reproducibility was almost perfect (κ = 0.880). Conclusion High-quality pediatric CCT can be performed using a 64-slice scanner, with a radiation effective dose close to 2 mSv in about 50% of the cases.

scholarly journals Computed Tomography Angiography with a 192-slice Dual-source Computed Tomography System: Improvements in Image Quality and Radiation Dose

2016 ◽  
Vol 6 ◽  
pp. 44 ◽  
Author(s):  
Philip V M Linsen ◽  
Adriaan Coenen ◽  
Marisa M Lubbers ◽  
Marcel L Dijkshoorn ◽  
Mohamed Ouhlous ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Heart Rate ◽  
Image Quality ◽  
Radiation Dose ◽  
Computed Tomography Angiography ◽  
Signal To Noise Ratio ◽  
High Pitch ◽  
Subjective Image Quality ◽  
Dual Source ◽  
Noise Ratio

Purpose: This study aims to compare image quality, radiation dose, and the influence of the heart rate on image quality of high-pitch spiral coronary computed tomography angiography (CCTA) using 128-slice (second generation) dual-source CT (DSCT) and a 192-slice DSCT (third generation) scanner. Materials and Methods: Two consecutive cohorts of fifty patients underwent CCTA by high-pitch spiral scan mode using 128 or 192-slice DSCT. The 192-slice DSCT system has a more powerful roentgen tube (2 × 120 kW) that allows CCTA acquisition at lower tube voltages, wider longitudinal coverage for faster table speed (732 m/s), and the use of iterative reconstruction. Objective image quality was measured as the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective image quality was evaluated using a Likert scale. Results: While the effective dose was lower with 192-slice DSCT (1.2 ± 0.5 vs. 0.6 ± 0.3 mSv; P < 0.001), the SNR (18.9 ± 4.3 vs. 11.0 ± 2.9; P < 0.001) and CNR (23.5 ± 4.8 vs. 14.3 ± 4.1; P < 0.001) were superior to 128-slice DSCT. Although patients scanned with 192-slice DSCT had a faster heart rate (59 ± 7 vs. 56 ± 6; P = 0.045), subjective image quality was scored higher (4.2 ± 0.8 vs. 3.0 ± 0.7; P < 0.001) compared to 128-slice DSCT. Conclusions: High-pitch spiral CCTA by 192-slice DSCT provides better image quality, despite a higher average heart rate, at lower radiation doses compared to 128-slice DSCT.

Using 100- instead of 120-kVp computed tomography to diagnose pulmonary embolism almost halves the radiation dose with preserved diagnostic quality

2010 ◽  
Vol 51 (3) ◽  
pp. 260-270 ◽  
Author(s):  
Peter Björkdahl ◽  
Ulf Nyman
Keyword(s):  
Computed Tomography ◽  
Pulmonary Embolism ◽  
Image Quality ◽  
Radiation Dose ◽  
Effective Dose ◽  
Ct Number ◽  
Subjective Image Quality ◽  
Diagnostic Quality ◽  
X Ray ◽  
Tube Potential

Background: Concern has been raised regarding the mounting collective radiation doses from computed tomography (CT), increasing the risk of radiation-induced cancers in exposed populations. Purpose: To compare radiation dose and image quality in a chest phantom and in patients for the diagnosis of pulmonary embolism (PE) at 100 and 120 peak kilovoltage (kVp) using 16-multichannel detector computed tomography (MDCT). Material and Methods: A 20-ml syringe containing 12 mg I/ml was scanned in a chest phantom at 100/120 kVp and 25 milliampere seconds (mAs). Consecutive patients underwent 100 kVp ( n = 50) and 120 kVp ( n = 50) 16-MDCT using a “quality reference” effective mAs of 100, 300 mg I/kg, and a 12-s injection duration. Attenuation (CT number), image noise (1 standard deviation), and contrast-to-noise ratio (CNR; fresh clot = 70 HU) of the contrast medium syringe and pulmonary arteries were evaluated on 3-mm-thick slices. Subjective image quality was assessed. Computed tomography dose index (CTDIvol) and dose–length product (DLP) were presented by the CT software, and effective dose was estimated. Results: Mean values in the chest phantom and patients changed as follows when X-ray tube potential decreased from 120 to 100 kVp: attenuation +23% and +40%, noise +38% and +48%, CNR −6% and 0%, and CTDIvol −38% and −40%, respectively. Mean DLP and effective dose in the patients decreased by 42% and 45%, respectively. Subjective image quality was excellent or adequate in 49/48 patients at 100/120 kVp. No patient with a negative CT had any thromboembolism diagnosed during 3-month follow-up. Conclusion: By reducing X-ray tube potential from 120 to 100 kVp, while keeping all other scanning parameters unchanged, the radiation dose to the patient may be almost halved without deterioration of diagnostic quality, which may be of particular benefit in young individuals.

scholarly journals Low-Dose Computed Tomography for the Optimization of Radiation Dose Exposure in Patients with Crohn’s Disease

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Richard G. Kavanagh ◽  
John O’Grady ◽  
Brian W. Carey ◽  
Patrick D. McLaughlin ◽  
Siobhan B. O’Neill ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Crohn’S Disease ◽  
Image Quality ◽  
Crohn's Disease ◽  
Radiation Dose ◽  
Ionizing Radiation ◽  
Low Dose ◽  
Radiation Doses ◽  
Radiation Dose Exposure ◽  
Ct Technology

Magnetic resonance imaging (MRI) is the mainstay method for the radiological imaging of the small bowel in patients with inflammatory bowel disease without the use of ionizing radiation. There are circumstances where imaging using ionizing radiation is required, particularly in the acute setting. This usually takes the form of computed tomography (CT). There has been a significant increase in the utilization of computed tomography (CT) for patients with Crohn’s disease as patients are frequently diagnosed at a relatively young age and require repeated imaging. Between seven and eleven percent of patients with IBD are exposed to high cumulative effective radiation doses (CEDs) (>35–75 mSv), mostly patients with Crohn’s disease (Newnham E 2007, Levi Z 2009, Hou JK 2014, Estay C 2015). This is primarily due to the more widespread and repeated use of CT, which accounts for 77% of radiation dose exposure amongst patients with Crohn’s disease (Desmond et al., 2008). Reports of the projected cancer risks from the increasing CT use (Berrington et al., 2007) have led to increased patient awareness regarding the potential health risks from ionizing radiation (Coakley et al., 2011). Our responsibilities as physicians caring for these patients include education regarding radiation risk and, when an investigation that utilizes ionizing radiation is required, to keep radiation doses as low as reasonably achievable: the “ALARA” principle. Recent advances in CT technology have facilitated substantial radiation dose reductions in many clinical settings, and several studies have demonstrated significantly decreased radiation doses in Crohn’s disease patients while maintaining diagnostic image quality. However, there is a balance to be struck between reducing radiation exposure and maintaining satisfactory image quality; if radiation dose is reduced excessively, the resulting CT images can be of poor quality and may be nondiagnostic. In this paper, we summarize the available evidence related to imaging of Crohn’s disease, radiation exposure, and risk, and we report recent advances in low-dose CT technology that have particular relevance.

Image quality and radiation dose in 256-slice cardiac computed tomography: Comparison of prospective versus retrospective image acquisition protocols

2011 ◽  
Vol 80 (1) ◽  
pp. 127-135 ◽  
Author(s):  
Waldemar Hosch ◽  
Tobias Heye ◽  
Felix Schulz ◽  
Stephanie Lehrke ◽  
Martin Schlieter ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Image Quality ◽  
Radiation Dose ◽  
Cardiac Computed Tomography ◽  
Image Acquisition

scholarly journals Application of Different methods for Reducing Radiation Dose to Breast during MDCT

2018 ◽  
Author(s):  
M Keshtkar ◽  
V Saba ◽  
M A Mosleh-Shirazi
Keyword(s):  
Image Quality ◽  
Radiation Dose ◽  
Low Income ◽  
Low Income Countries ◽  
Radiological Protection ◽  
Reconstruction Algorithms ◽  
Radiation Induced Cancer ◽  
Bismuth Shielding ◽  
Ct Scanners ◽  
Radiosensitive Organs

The increased use of computed tomography (CT) and its high radiation dose have led to great concerns about its potential for radiation induced cancer risks. Breast is a radiosensitive tissue based on tissue weighting factors assigned by the International Commission on Radiological Protection (ICRP). Moreover, the dose is maximal on the surface of the patient. Therefore, strategies should be taken to reduce radiation dose to the breast. The aim of this review is to introduce methods used for reducing radiation dose to breast in thoracic CT and review related performed studies. The literature indicates that bismuth shielding increases image noise and CT numbers as well as introducing streak artifacts. Tube current modulation (TCM) technique and iterative reconstruction algorithms can provide some levels of dose reduction to radiosensitive organs and superior image quality without the disadvantages of bismuth shielding. However, they are not available on all CT scanners, especially in low-income countries. Such centers may have to continue using bismuth shields to reduce the dose until these superior techniques become available at lower costs in all CT scanners. Furthermore, design and manufacture of new shields with the lower impact on image quality are desirable.

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