Objective Image Noise Research Articles

Benefits of Low-Dose CT Scan of Head for Patients With Intracranial Hemorrhage.

Objectives:For patients with intracranial hemorrhage (ICH), routine follow-up computed tomography (CT) scans are typically required to monitor the progression of intracranial pathology. Remarkable levels of radiation exposure are accumulated during repeated CT scan. However, the effects and associated risks have still remained elusive. This study presented an effective approach to quantify organ-specific radiation dose of repeated CT scans of head for patients with ICH. We also indicated whether a low-dose CT scan may reduce radiation exposure and keep the image quality highly acceptable for diagnosis.Methods:Herein, 72 patients with a history of ICH were recruited. The patients were divided into 4 groups and underwent CT scan of head with different tube current–time products (250, 200, 150, and 100 mAs). Two experienced radiologists visually rated scores of quality of images according to objective image noise, sharpness, diagnostic acceptability, and artifacts due to physiological noise on the same workstation. Organ-/tissue-specific radiation doses were analyzed using Radimetrics.Results:In conventional CT scan group, signal to noise ratio (SNR) and contrast to noise ratio (CNR) of ICH images were significantly higher than those in normal brain structures. Reducing the tube current–time product may decrease the image quality. However, the predilection sites for ICH could be clearly identified. The SNR and CNR in the predilection sites for ICH were notably higher than other areas. The brain, eye lenses, and salivary glands received the highest radiation dose. Reducing tube current–time product from 250 to 100 mA can significantly reduce the radiation dose.Discussion:We demonstrated that low-dose CT scan of head can still provide reasonable images for diagnosing ICH. The radiation dose can be reduced to ∼45% of the conventional CT scan group.

Improving Low-Dose Pediatric Abdominal CT by Using Convolutional Neural Networks.

To evaluate the efficacy of convolutional neural networks (CNNs) to improve the image quality of low-dose pediatric abdominal CT images. Images from 11 pediatric abdominal CT examinations acquired between June and July 2018 were reconstructed with filtered back projection (FBP) and an iterative reconstruction (IR) algorithm. A residual CNN was trained using the FBP image as the input and the difference between FBP and IR as the target such that the network was able to predict the residual image and simulate the IR. CNN-based postprocessing was applied to 20 low-dose pediatric image datasets acquired between December 2016 and December 2017 on a scanner limited to reconstructing FBP images. The FBP and CNN images were evaluated based on objective image noise and subjective image review by two pediatric radiologists. For each of five features, readers rated images on a five-point Likert scale and also indicated their preferred series. Readers also indicated their "overall preference" for CNN versus FBP. Preference and Likert scores were analyzed for individual and combined readers. Interreader agreement was assessed. The CT number remained unchanged between FBP and CNN images. Image noise was reduced by 31% for CNN images (P < .001). CNN was preferred for overall image quality for individual and combined readers. For combined Likert scores, at least one of the two score types (Likert or binary preference) indicated a significant favoring of CNN over FBP for low contrast, image noise, artifacts, and high contrast, whereas the reverse was true for spatial resolution. FBP images can be improved in image space by a well-trained CNN, which may afford a reduction in dose or improvement in image quality on scanners limited to FBP reconstruction.© RSNA, 2019.

Initial clinical experience with high-pitch dual-source CT as a rapid technique for thoraco-abdominal evaluation in awake infants and young children

To evaluate dual-source high-pitch computed tomography (HPCT) imaging of the chest and abdomen as a rapid scanning technique to obtain diagnostic-quality imaging evaluation of infants and young children without sedation. Fifty-three paediatric patients (age 24.1±2 months) who underwent chest or abdomen HPCT (≥1.5) and standard pitch CT (SPCT, <1.5) on a dual-source 128-row multidetector CT system were included in the study. Image quality assessment was performed by two paediatric radiologists for diagnostic confidence, image artefacts, and image noise. Objective image noise was measured. Most of the CT examinations were performed in children who were >1 year old (n=15 and n=20) followed by ≤1 year old (n=8 and n=10) in SPCT and HPCT, respectively. The mean radiation dose (SSDE) from HPCT was 1.96±1 mGy compared to 2.2±1 mGy for SPCT (p=0.3). No major artefacts were reported and overall image quality of all HPCT examinations was acceptable diagnostically. In addition, objective image noise values were not significantly different between HPCT compared with SPCT (11±3 versus 11±5, p=0.7). Ultra-fast, HPCT can be performed without the need for sedation as a potential alternative to anaesthetised magnetic resonance imaging in infants and young children.

Effect of a novel denoising technique on image quality and diagnostic accuracy in low-dose CT in patients with suspected appendicitis

ObjectivesTo determine the effect of a vendor unspecific, DICOM-based denoising technique on image quality and diagnostic performance in low-dose simulated abdominal computed tomography (CT) examinations in patients with suspected appendicitis. Methods and MaterialsWe included 51 patients who underwent contrast-enhanced abdominal CT with Filtered Back Projection due to suspected appendicitis. Realistic Low-Dose simulation generated low-dose datasets at 25% of the original exposition. QuantaStream Denoising, a novel DICOM-based technique denoised the simulated low-Dose datasets. Original (O100), low-dose (LD25) and denoised (DN25) datasets (n = 153) were evaluated regarding subjective image quality (5-point Likert scale; overall quality/image noise/diagnostic confidence), presence/absence of acute appendicitis, free abdominal air and abscess formation and objective image quality (Signal-to-Noise Ratio (SNR) and noise level) by two independent readers. ResultsSubjective image quality was rated highest for O100, followed by DN25 and LD25 with significant differences (p = 0.001). Appendicitis was correctly identified in all datasets (n = 30). Appendicitis specific diagnostic confidence was highest for O100 (p = 0.001), followed by DN25 and LD25 without significant difference. All complications were correctly identified on O100 and DN25. On LD25, diagnostic accuracy decreased for abscess formations (sensitivity:0.714; specificity:1.0) and for free abdominal air (sensitivity:0.750; specificity:0.936). Regarding noise levels DN25 showed non-inferiority to O100. SNRs of O100 and DN25 showed no significant difference (p = 0.06). ConclusionOur findings indicate that QuantaStream Denoising allows for maintained diagnostic image quality and diagnostic accuracy of low-dose abdominal CT examinations (25% of original exposition) in patients with suspected appendicitis without the need for raw sinogram data.

Low-dose computed tomography of urolithiasis in obese patients: a feasibility study to evaluate image reconstruction algorithms.

Purpose: Retrospective evaluation and comparison of image quality generated by low-dose computed tomography (LDCT) from obese patients with urolithiasis using alternative reconstruction algorithms.Materials and methods: Twenty-five obese patients (body mass index [BMI]>25 kg/m2) underwent LDCT scans for suspected urolithiasis. The scans were recompiled using filtered-back projection (FBP), statistical iterative reconstruction (iDose) and iterative model-based reconstruction (IMR). Dose-length product (DLP) and patient details were obtained from the CT dose report and clinical charts, respectively. Objective image noise was assessed by measuring the SD of Hounsfield units (HUs) in defined locations. Additionally, subjective image evaluation was independently performed by two radiologists using a 3-point Likert scale. The inter-reviewer agreement of image quality was calculated.Results: Ureteral concretions were observed in all CT scans, two of which revealed bilateral stones. The assessed patients’ mean BMI was 29.29±3.74 kg/m2, and the DLP of the CT scans was 100.04±10.00 mGy*cm. All scans were rated diagnostic with the iDose and iterative model-based reconstructions, whereas 41% of the scans performed with FBP reconstruction were nondiagnostic. With respect to image quality, IMR was superior to iDose and FBP, both in the objective (P<0.001) and overall subjective (P≤0.008) evaluation of the respective data sets. The inter-reviewer agreement for overall image quality was “almost perfect” for IMR, “substantial” for iDose and “moderate” for FBP (κ values of 1.0, 0.6 and 0.46, respectively).Conclusion: Using iterative image reconstruction algorithms, LDCT of urolithiasis is feasible in overweight patients with a BMI between 25 and 35 kg/m2. Due to higher image quality, IMR is the preferred algorithm for scan reconstruction as it may help to avoid repeated examinations due to initial nondiagnostic scans.

Feasibility of radiation dose reduction with iterative reconstruction in abdominopelvic CT for patients with inappropriate arm positioning.

BackgroundThe arms-down position increases computed tomography (CT) radiation dose. Iterative reconstruction (IR) could enhance image quality without increasing radiation dose in patients with arms-down position.AimTo investigate the feasibility of reduced-dose CT with IR for patients with inappropriate arm positioningMethodsTwenty patients who underwent two-phase abdominopelvic CT including standard-dose and reduced-dose CT (performed with 80% of the radiation dose of the standard protocol) with their arms positioned in the abdominal area were included in this study. Reduced-dose CT images were reconstructed using filtered back projection (FBP), hybrid IR, and iterative model reconstruction (IMR). These images were compared with standard-dose CT images reconstructed with FBP. Objective image noise in the liver and subcutaneous fat was measured by standard deviation for the quantitative analysis. Then, two radiologists qualitatively assessed beam hardening artifacts, artificial texture, noise, sharpness, and overall image quality in consensus.ResultsReduced-dose CT with all IR levels had lower objective image noise compared to standard-dose CT with FBP reconstruction (P < 0.05). Quantitatively measured beam hardening artifacts were similar in reduced-dose CT with iDose levels 5–6 and fewer with IMR compared to standard-dose CT. In the qualitative analysis, beam hardening artifacts and noise decreased as the IR levels increased. However, artificial texture was significantly aggravated with iDose 5–6 and IMR, and overall image quality significantly worsened with IMR.ConclusionsIR algorithms can reduce beam hardening artifacts in a reduced-dose CT setting in patients with arms-down position, and an intermediate level of hybrid IR allows radiologists to obtain the best image quality. Because the retrospective and single-center nature of our study limited the number of patients, multicenter prospective clinical studies are required to validate our results.

Low-tube-voltage CT assessment of Adamkiewicz artery: Precise comparison between 100-kVp- and 120-kVp protocols

PurposePreoperative identification of Adamkiewicz artery (AKA) for preventing postoperative spinal cord ischemia is still challenging because of its small diameter. Low-tube-voltage technique might improve the delineation of AKA due to its higher contrast enhancement and contrast-to-noise ratio (CNR). Our purpose was to evaluate the usefulness of low-tube-voltage CTA in visualization of AKA compared with the conventional voltage protocol on the condition with the same imaging parameters aside from tube voltage. MethodsEighty-three patients undergoing CTA for the evaluation of aorta were retrospectively included. All CTA was performed with 320-detector-row CT with the tube voltage of either 100-kVp (41 patients) or 120-kVp (42 patients). The CNR, CT value of aorta and objective image noise were assessed. Visualization of AKA was evaluated based on the continuity from aorta using the four-grade score by two independent reviewers. The estimated radiation dose (volumetric CT dose index) was also compared. ResultsThe 100-kVp group showed significantly higher CNR and CT value than 120-kVp protocol (P = 0.010 and < 0.001, respectively). The visual score was also significantly higher in 100-kVp group than in 120-kVp group (2.73 ± 0.98 and 2.02 ± 1.00, respectively; P = 0.002). There was no significant difference on objective image noise and radiation dose between the groups (P = 0.24 and 0.72, respectively). ConclusionCTA with low-tube-voltage was significantly more sensitive for AKA visualization than conventional voltage protocol.

Low-dose CT imaging of the acute abdomen using model-based iterative reconstruction: a prospective study.

Performance of a modified abdominopelvic CT protocol reconstructed using full iterative reconstruction (IR) was assessed for imaging patients presenting with acute abdominal symptoms. Fifty-seven patients (17 male, 40 female; mean age of 56.5 ± 8years) were prospectively studied. Low-dose (LD) and conventional-dose (CD) CTs were contemporaneously acquired between November 2015 and March 2016. The LD and CD protocols imparted radiation exposures approximating 10-20% and 80-90% those of routine abdominopelvic CT, respectively. The LD images were reconstructed with model-based iterative reconstruction (MBIR), and CD images with hybrid IR (40% adaptive statistical iterative reconstruction (ASIR)). Image quality was assessed quantitatively and qualitatively. Independent clinical interpretations were performed with a 6-week delay between reviews. A 74.7% mean radiation dose reduction was achieved: LD effective dose (ED) 2.38 ± 1.78mSv (size-specific dose estimate (SSDE) 3.77 ± 1.97mGy); CD ED 7.04 ± 4.89mSv (SSDE 10.74 ± 5.5mGy). LD-MBIR images had significantly lower objective and subjective image noise compared with CD-ASIR (p < 0.0001). Noise reduction for LD-MBIR studies was greater for patients with BMI < 25kg/m2 than those with BMI ≥ 25kg/m2 (5.36 ± 3.2Hounsfield units (HU) vs. 4.05 ± 3.1HU, p < 0.0001). CD-ASIR studies had significantly better contrast resolution, and diagnostic acceptability (p < 0.0001 for all). LD-MBIR studies had significantly lower streak artifact (p < 0.0001). There was no difference in sensitivity for primary findings between the low-dose and conventional protocols with the exception of one case of enteritis. Low-dose abdominopelvic CT performed with MBIR is a feasible radiation dose reduction strategy for imaging patients presenting with acute abdominal pain.

Impact of Single-Energy Metal Artifact Reduction on CT image quality in patients with dental hardware

BackgroundTo evaluate whether Canon's Single-Energy Metal Artifact Reduction (SEMAR) algorithm can significantly improve subjective and objective image quality of patients with nonremovable dental hardware undergoing CT imaging of the oral cavity and oropharynx. Materials and methodsSEMAR was reconstructed from routine Adaptive Iterative Dose Reduction (AIDR) images in 154 patients (46 females and 108 males; mean age 66.3 ± 10.5 years). Subjective SEMAR and AIDR image quality of the mouth floor, sublingual glands, lymphatic ring and overall impression were evaluated by two independent radiologists on a 6-point scale (1 = very good image quality, 6 = poor image quality) and compared to ratings of an oral and maxillofacial surgeon. Interrater agreement was assessed using the intraclass correlation coefficient (ICC). Objective image analysis was performed by placing regions of interest (ROIs) on the mouth floor and measuring CT attenuation in Hounsfield units (HU) and standard deviation (SD). ResultsSEMAR significantly improved subjective image quality in all evaluated structures for all raters (p < 0.001). Furthermore, SEMAR significantly reduced objective metal artifacts and image noise (p < 0.001). ConclusionSEMAR significantly improved diagnostic quality of CT images of the oral cavity and oropharynx by reducing artifacts caused by dental hardware.

A phantom study of the performance of model-based iterative reconstruction in low-dose chest and abdominal CT: When are benefits maximized?

IntroductionThe aim of this study was to assess and compare the effects of CT image reconstruction techniques on low-dose CT image quality using phantoms. MethodsAnthropomorphic torso and spatial/contrast-resolution phantoms were scanned at decreasing tube currents between 400 and 10 mA. CT thorax and abdomen/pelvis series were reconstructed with filtered back projection (FBP) alone, combined 40% adaptive statistical iterative reconstruction & FBP (ASIR40), and model-based iterative reconstruction (MBIR) [(resolution-preference 05 (RP05) and RP20 in the thorax and RP05 and noise-reduction 05 (NR05) in the abdomen)]. Two readers rated image quality quantitatively and qualitatively. ResultsIn thoracic CT, objective image noise on MBIR RP05 data sets outperformed FBP at 200, 100, 50 and 10 mA and outperformed ASIR40 at 50 and 10 mA (p < 0.001). MBIR RP20 outperformed FBP at 50 and 10 mA and outperformed ASIR40 at 10 mA (p < 0.001). Compared with both FBP and ASIR40, MBIR RP05 demonstrated significantly better signal-to-noise ratio (SNR) at 10 mA. In abdomino-pelvic CT, MBIR RP05 and NR05 outperformed FBP and ASIR at all tube current levels for objective image noise. NR05 demonstrated greater SNR at 200, 100, 50 and 10 mA and RP05 demonstrated greater SNR at 50 and 10 mA compared with both FBP and ASIR. MBIR images demonstrated better subjective image quality scores. Spatial resolution, low-contrast detectability and contrast-to-noise ratio (CNR) were comparable between image reconstruction techniques. ConclusionCTs reconstructed with MBIR have lower image noise and improved image quality compared with FBP and ASIR. These effects increase with reduced radiation exposure confirming optimal use for low-dose CT imaging.

Reduction of the radiation dose and the amount of contrast material in hepatic dynamic CT using low tube voltage and adaptive iterative dose reduction 3-dimensional.

The purpose of this study was to prospectively evaluate the image quality and the diagnostic ability of low tube voltage and reduced contrast material dose hepatic dynamic computed tomography (CT) reconstructed with adaptive iterative dose reduction 3-dimensional (AIDR 3D).Eighty-nine patients underwent hepatic dynamic CT using one of the 2 protocols: tube voltage of 120 kVp, contrast dose of 600 mgI/kg, and filtered back projection in Protocol A (n = 46), and tube voltage of 100 kVp, contrast dose of 500 mgI/kg, and AIDR 3D in Protocol B (n = 43). The volume CT dose index (CTDIvol) and size-specific dose estimates (SSDEs) were compared between the 2 groups. Objective image noise and tumor to liver contrast-to-noise ratio (CNR) were also compared. Three radiologists independently reviewed image quality. The jackknife alternative free-response receiver-operating characteristic (JAFROC) analysis was performed to compare diagnostic performance.The mean CTDIvol and SSDE of Protocol B (14.3 and 20.2, respectively) were significantly lower than those of Protocol A (22.1 and 31.4, P < .001). There were no significant differences in either objective image noise or CNR. In the qualitative analysis, 2 readers assigned significant lower scores to images of Protocol B for at least one of the 3 phases regarding overall image quality (P < .05). There was no significant difference in the JAFROC1 figure of merit between protocols.Low tube voltage CT with AIDR 3D yielded a reduction in radiation dose and in the amount of contrast material while maintaining diagnostic performance.

Determination of a suitable low‐dose abdominopelvic CT protocol using model‐based iterative reconstruction through cadaveric study

Cadaveric studies provide a means of safely assessing new technologies and optimizing scanning prior to clinical validation. Reducing radiation exposure in a clinical setting can entail incremental dose reductions to avoid missing important clinical findings. The use of cadavers allows assessment of the impact of more substantial dose reductions on image quality. Our aim was to identify a suitable low-dose abdominopelvic CT protocol for subsequent clinical validation. Five human cadavers were scanned at one conventional dose and three low-dose settings. All scans were reconstructed using three different reconstruction algorithms: filtered back projection (FBP), hybrid iterative reconstruction (60% FBP and 40% adaptive statistical iterative reconstruction (ASIR40)), and model-based iterative reconstruction (MBIR). Two readers rated the image quality both quantitatively and qualitatively. Model-based iterative reconstruction images had significantly better objective image noise and higher qualitative scores compared with both FBP and ASIR40 images at all dose levels. The greatest absolute noise reduction, between MBIR and FBP, of 34.3 HU (equating to a 68% reduction) was at the lowest dose level. MBIR reduced image noise and improved image quality even in CT images acquired with a mean radiation dose reduction of 62% compared with conventional dose studies reconstructed with ASIR40, with lower levels of objective image noise, superior diagnostic acceptability and contrast resolution, and comparable subjective image noise and streak artefact scores. This cadaveric study demonstrates that MBIR reduces image noise and improves image quality in abdominopelvic CT images acquired with dose reductions of up to 62%.

Variations in MTF and NPS between CT scanners with two different IR algorithms and detectors

The use of iterative reconstruction (IR) in computed tomography (CT) has become a useful tool for improved image quality or for reduced dose in CT examinations. In this study, the image quality of the two different Siemens IR algorithms, sinogram affirmed iterative reconstruction (SAFIRE) and advanced modelled iterative reconstruction (ADMIRE), were evaluated and compared. Differences between the Stellar detector and the conventional detector and similarities between scanners with the same detector and IR algorithm were also examined. The objective image quality parameters modulation transfer function (MTF) and noise power spectrum (NPS) were measured on a Catphan 600 phantom (The Phantom Laboratory Incorporated, NY) for five different Siemens CT scanners. MTF was calculated from the circular edge of the sensitometry targets in Catphan to facilitate measurements at different contrasts and dose levels. The results showed that the image quality was improved by using ADMIRE compared to SAFIRE on the same CT scanner equipped with the Stellar detector for certain specific tasks. The MTF was higher for the three low contrast objects when the sharp reconstruction kernel was applied. The CT scanners equipped with the Stellar detector showed an improved image quality compared to the CT scanners equipped with the conventional detector. Larger differences in MTF and NPS were observed between the detectors than between SAFIRE and ADMIRE.

Experience With Iterative Reconstruction Techniques for Abdominopelvic Computed Tomography in Morbidly and Super Obese Patients.

The aim of this study was to investigate the diagnostic performance of abdominopelvic computed tomography (CT) images reconstructed using filtered back projection (FBP) and iterative reconstruction (IR) algorithms in morbidly and super obese patients. One hundred eighty-seven abdominopelvic CT examinations in portal venous phase were performed between February 2015 and February 2016 in 182 patients (mean age = 52 years, mean body mass index = 45.5). One hundred fourteen of 187 examinations were reconstructed using IR and 73 examinations were processed using FBP. Patients were further stratified based on body mass index. Sixty CT scans were reviewed by a single reader for image quality, image noise, and artifacts. Objective noise and attenuation were also determined. Size-specific dose estimate and CT dose index volume were compared and statistically analyzed. A diagnostic interpretation was rendered for all 187 examinations. A single-reader review of 60 cases showed greater diagnostic acceptability for IR when compared with FBP (image quality = 4.2 and 3.8 [P = 0.035], noise = 1.5 and 1.6 [P = 0.692], artifact = 1.4 and 1.5 [P = 0.759], respectively). For all examinations, the IR group had lower objective image noise (IR = 9.3 and FBP = 14.3; P < 0.001) and higher contrast-to-noise ratio (IR = 17.2 and FBP = 11.7; P < 0.001) without increase in radiation dose (size-specific dose estimate [IR = 15.1, FBP = 16.5 mGy; P = 0.045] and CT dose index volume [IR = 17.6, FBP = 18 mGy; P = 0.62]). In morbidly and super obese patients, diagnostic quality images could be reliably generated with minimal artifacts and noise using newer generation scanners integrated with IR without increasing radiation dose.

Screening for lung cancer using sub-millisievert chest CT with iterative reconstruction algorithm: image quality and nodule detectability.

To investigate the image quality and nodules detectability using ultra-low dose (ULD) protocol with iterative model reconstruction (IMR) algorithm when compared to routine low dose (LD) chest CT in lung cancer screening. Chest CT scans were acquired using a 256-slice scanner for 300 subjects. The scan protocol for theULD group was 120kVp/17mAs while forthe LD group was 120kVp/30mAs. All images were reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR) and IMR algorithms. Effective dose was recorded. Image quality assessments were performed by two radiologists. SD of CT attenuation was measured as objective image noise. The number of non-calcified nodules detected in both groups with different reconstruction algorithms were calculated and compared. The effectivedose of ULD group (0.67 ± 0.08 mSv) was about 44% reduced compared with LD group (1.20 ± 0.08 mSv) (p < 0.01). IMR improved image quality and reduced image noise significantly than HIR and FBP in both groups (all, p < 0.01). IMR enabled a higher number of nodule detected compared to FBP and HIR in both LD and ULD groups, especially for solid nodules less than 4 mm. IMR may improve the diagnostic accuracy of ULD CT lung screening with potential nodule detectability improvement. IMR enables significant reduction of the image noise and improvement of image quality in sub-mSv (66% reduction) chest scans.

Assessment of noise reduction potential and image quality improvement of a new generation adaptive statistical iterative reconstruction (ASIR-V) in chest CT.

To evaluate the image quality improvement and noise reduction in routine dose, non-enhanced chest CT imaging by using a new generation adaptive statistical iterative reconstruction (ASIR-V) in comparison with ASIR algorithm. 30 patients who underwent routine dose, non-enhanced chest CT using GE Discovery CT750HU (GE Healthcare, Waukesha, WI) were included. The scan parameters included tube voltage of 120 kVp, automatic tube current modulation to obtain a noise index of 14HU, rotation speed of 0.6 s, pitch of 1.375:1 and slice thickness of 5 mm. After scanning, all scans were reconstructed with the recommended level of 40%ASIR for comparison purpose and different percentages of ASIR-V from 10% to 100% in a 10% increment. The CT attenuation values and SD of the subcutaneous fat, back muscle and descending aorta were measured at the level of tracheal carina of all reconstructed images. The signal-to-noise ratio (SNR) was calculated with SD representing image noise. The subjective image quality was independently evaluated by two experienced radiologists. For all ASIR-V images, the objective image noise (SD) of fat, muscle and aorta decreased and SNR increased along with increasing ASIR-V percentage. The SD of 30% ASIR-V to 100% ASIR-V was significantly lower than that of 40% ASIR (p < 0.05). In terms of subjective image evaluation, all ASIR-V reconstructions had good diagnostic acceptability. However, the 50% ASIR-V to 70% ASIR-V series showed significantly superior visibility of small structures when compared with the 40% ASIR and ASIR-V of other percentages (p < 0.05), and 60% ASIR-V was the best series of all ASIR-V images, with a highest subjective image quality. The image sharpness was significantly decreased in images reconstructed by 80% ASIR-V and higher. In routine dose, non-enhanced chest CT, ASIR-V shows greater potential in reducing image noise and artefacts and maintaining image sharpness when compared to the recommended level of 40%ASIR algorithm. Combining both the objective and subjective evaluation of images, non-enhanced chest CT images reconstructed with 60% ASIR-V have the highest image quality. Advances in knowledge: This is the first clinical study to evaluate the clinical value of ASIR-V in the same patients using the same CT scanner in the non-enhanced chest CT scans. It suggests that ASIR-V provides the better image quality and higher diagnostic confidence in comparison with ASIR algorithm.

Value of 100 kVp scan with sinogram-affirmed iterative reconstruction algorithm on a single-source CT system during whole-body CT for radiation and contrast medium dose reduction: an intra-individual feasibility study

To perform an intra-individual investigation of the usefulness of a contrast medium (CM) and radiation dose-reduction protocol using single-source computed tomography (CT) combined with 100 kVp and sinogram-affirmed iterative reconstruction (SAFIRE) for whole-body CT (WBCT; chest-abdomen-pelvis CT) in oncology patients. Forty-three oncology patients who had undergone WBCT under both 120 and 100 kVp protocols at different time points (mean interscan intervals: 98 days) were included retrospectively. The CM doses for the 120 and 100 kVp protocols were 600 and 480 mg iodine/kg, respectively; 120 kVp images were reconstructed with filtered back-projection (FBP), whereas 100 kVp images were reconstructed with FBP (100 kVp-F) and the SAFIRE (100 kVp-S). The size-specific dose estimate (SSDE), iodine load and image quality of each protocol were compared. The SSDE and iodine load of 100 kVp protocol were 34% and 21%, respectively, lower than of 120 kVp protocol (SSDE: 10.6±1.1 versus 16.1±1.8 mGy; iodine load: 24.8±4versus 31.5±5.5 g iodine, p<0.01). Contrast enhancement, objective image noise, contrast-to-noise-ratio, and visual score of 100 kVp-S were similar to or better than of 120 kVp protocol. Compared with the 120 kVp protocol, the combined use of 100 kVp and SAFIRE in WBCT for oncology assessment with an SSCT facilitated substantial reduction in the CM and radiation dose while maintaining image quality.

Image quality of CT angiography in young children with congenital heart disease: a comparison between the sinogram-affirmed iterative reconstruction (SAFIRE) and advanced modelled iterative reconstruction (ADMIRE) algorithms

To compare the image quality of computed tomography angiography (CTA) reconstructed by sinogram-affirmed iterative reconstruction (SAFIRE) with that of advanced modelled iterative reconstruction (ADMIRE) in children with congenital heart disease (CHD). Thirty-one children (8.23±13.92 months) with CHD who underwent CTA were enrolled. Images were reconstructed using SAFIRE (strength 5) and ADMIRE (strength 5). Objective image qualities (attenuation, noise) were measured in the great vessels and heart chambers. Two radiologists independently calculated the contrast-to-noise ratio (CNR) by measuring the intensity and noise of the myocardial walls. Subjective noise, diagnostic confidence, and sharpness at the level prior to the first branch of the main pulmonary artery were also graded by the two radiologists independently. The objective image noise of ADMIRE was significantly lower than that of SAFIRE in the right atrium, right ventricle, and myocardial wall (p<0.05); however, there were no significant differences observed in the attenuations among the four chambers and great vessels, except in the pulmonary arteries (p>0.05). The mean CNR values were 21.56±10.80 for ADMIRE and 18.21±6.98 for SAFIRE, which were significantly different (p<0.05). In addition, the diagnostic confidence of ADMIRE was significantly lower than that of SAFIRE (p<0.05), while the subjective image noise and sharpness of ADMIRE were not significantly different (p>0.05). CTA using ADMIRE was superior to SAFIRE when comparing the objective and subjective image quality in children with CHD.

Effects of pure and hybrid iterative reconstruction algorithms on high-resolution computed tomography in the evaluation of interstitial lung disease

ObjectivesTo compare image quality characteristics of high-resolution computed tomography (HRCT) in the evaluation of interstitial lung disease using three different reconstruction methods: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP). MethodsEighty-nine consecutive patients with interstitial lung disease underwent standard-of-care chest CT with 64-row multi-detector CT. HRCT images were reconstructed in 0.625-mm contiguous axial slices using FBP, ASIR, and MBIR. Two radiologists independently assessed the images in a blinded manner for subjective image noise, streak artifacts, and visualization of normal and pathologic structures. Objective image noise was measured in the lung parenchyma. Spatial resolution was assessed by measuring the modulation transfer function (MTF). ResultsMBIR offered significantly lower objective image noise (22.24±4.53, P<0.01 among all pairs, Student's t-test) compared with ASIR (39.76±7.41) and FBP (51.91±9.71). MTF (spatial resolution) was increased using MBIR compared with ASIR and FBP. MBIR showed improvements in visualization of normal and pathologic structures over ASIR and FBP, while ASIR was rated quite similarly to FBP. MBIR significantly improved subjective image noise (P<0.01 among all pairs, the sign test), and streak artifacts (P<0.01 each for MBIR vs. the other 2 image data sets). ConclusionMBIR provides high-quality HRCT images for interstitial lung disease by reducing image noise and streak artifacts and improving spatial resolution compared with ASIR and FBP.

Adaptive iterative dose reduction (AIDR) 3D in low dose CT abdomen-pelvis: Effects on image quality and radiation exposure

The widespread use of computed tomography (CT) has increased the medical radiation exposure and cancer risk. We aimed to evaluate the impact of AIDR 3D in CT abdomen-pelvic examinations based on image quality and radiation dose in low dose (LD) setting compared to standard dose (STD) with filtered back projection (FBP) reconstruction. We retrospectively reviewed the images of 40 patients who underwent CT abdomen-pelvic using a 80 slice CT scanner. Group 1 patients (n=20, mean age 41 ± 17 years) were performed at LD with AIDR 3D reconstruction and Group 2 patients (n=20, mean age 52 ± 21 years) were scanned with STD using FBP reconstruction. Objective image noise was assessed by region of interest (ROI) measurements in the liver and aorta as standard deviation (SD) of the attenuation value (Hounsfield Unit, HU) while subjective image quality was evaluated by two radiologists. Statistical analysis was used to compare the scan length, CT dose index volume (CTDIvol) and image quality of both patient groups. Although both groups have similar mean scan length, the CTDIvol significantly decreased by 38% in LD CT compared to STD CT (p<0.05). Objective and subjective image quality were statistically improved with AIDR 3D (p<0.05). In conclusion, AIDR 3D enables significant dose reduction of 38% with superior image quality in LD CT abdomen-pelvis.