Adaptive Statistical Iterative Reconstruction Images Research Articles

Value Comparison of Iterative Reconstruction Algorithm-Based Chest CT and Ultrasound in the Diagnosis of Community-Acquired Pneumonia in Children

This study aimed to explore the diagnostic value of chest computed tomography (CT) based on adaptive statistical iterative reconstruction (ASiR) in the optimal weight range for children with community-acquired pneumonia (CAP) and find the differences between chest CT and ultrasound in the diagnosis of CAP. 106 children who were diagnosed as CAP were selected as the research objects. All objects underwent CT and ultrasound scans to measure the noise of CT images after iterative reconstruction and the contrast-to-noise ratio (CNR) of the thoracic aorta and the back muscles. The correlation between ASiR weight, noise, and CNR was analyzed and compared further. In addition, the differences in imaging manifestations of lung consolidation, abnormal pleural line, alveolar interstitial syndrome, and pleural effusion were observed under the ultrasound and CT scans of the patients. The sensitivity, specificity, positive predicted value (PV), and negative PV of the CT scan and ultrasound were analyzed further for the diagnosis of CAP in children. The results showed that ASiR weight and image noise were extremely and negatively correlated ( P < 0.001 ) and that CNR and ASiR weight were extremely and positively correlated ( P < 0.001 ). 40–60% of ASiR image noise was in the middle position, and the muscle space and subcutaneous fat in CT images were clearer when ASiR was at 40% and 60%. 60.38% of children were diagnosed as CAP. The proportions of children with lung consolidation, interstitial changes, pleural effusion, and atelectasis after ultrasound and CT examination were not greatly different ( P > 0.05 ). After ASiR, the sensitivity of CT in detecting the abnormal pleural line + B-line/consolidation feature was the highest, 93.75%. The results of ultrasound diagnosis were consistent with those of chest CT diagnosis ( P < 0.01 ). This indicated that the sensitivity, specificity, positive PV, and negative PV of ASiR-based chest CT in the diagnosis of CAP were close to those of ultrasound.

Improving image quality with model-based iterative reconstruction algorithm for chest CT in children with reduced contrast concentration.

To evaluate model-based iterative reconstruction (MBIR) in improving the image quality of chest CT in children with reduced concentration contrast medium (CM). Fifty-six children (median age of 4years) who received low-dose enhanced chest CT were enrolled as the study group and compared with the control group of 56 children. Both groups used the automatic tube current modulation to achieve age-based noise index values of 11-15HU. The study group used 100kVp and reduced CM concentration of 270mgI/ml, and the images in this group were reconstructed with 50% adaptive statistical iterative reconstruction (ASIR) and MBIR. The control group used 120kV and standard CM of 320mgI/ml, and the images in this group were reconstructed with ASIR only. Subjective image quality and objective image quality of the three image sets were evaluated. The subjective quality included overall image noise, enhancement degree, lesion (including mediastinum mass, pulmonary space-occupying lesions, and parenchymal infiltrative lesions) conspicuity, and beam-hardening artifacts. The objective quality included the measurement of noise in the left ventricle and back muscle to calculate signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of ventricle. There was no difference in radiation dose between the study (CTDIvol of 1.79 ± 1.45mGy) and control (1.68 ± 0.92mGy) groups (p = 0.65). However, the study group used 19.7% lower CM dose than the control group (5.84 ± 2.69 vs. 7.27 ± 3.80gI), and the enhancement in all images met the diagnostic requirements. MBIR reduced image noise by 58.6% and increased SNR and CNR by 143.6% and 165.7%, respectively, compared to ASIR images in the control group. The two ASIR image sets had similar image quality. MBIR improved the image quality of low-radiation-dose chest CT in children at 19.3% reduced CM dose.

The Application of a New Model-Based Iterative Reconstruction in Low-Dose Upper Abdominal CT

To compare upper abdominal computed tomography (CT) image quality of new model-based iterative reconstruction (MBIR) with low-contrast resolution preference (MBIRNR40), conventional MBIR (MBIRc), and adaptive statistical iterative reconstruction (ASIR) at low dose with ASIR at routine-dose. Study included phantom and 60 patients who had initial and follow-up CT scans. For patients, the delay phase was acquired at routine-dose (noise index = 10 HU) for the initial scan and low dose (noise index = 20 HU) for the follow-up. The low-dose CT was reconstructed with 40% and 60% ASIR, MBIRc, and MBIRNR40, while routine-dose CT was reconstructed with 40% ASIR. CT value and noise measurements of the subcutaneous fat, back muscle, liver, and spleen parenchyma were compared using one-way ANOVA. Two radiologists used semiquantitative 7-scale (-3 to +3) to rate image quality and artifacts. The phantom study revealed superior low-contrast resolution with MBIRNR40. For patient scans, the CT dose index for the low-dose CT was 3.00 ± 1.32 mGy, 75% lower than the 11.90 ± 4.75 mGy for the routine-dose CT. Image noise for the low-dose MBIRNR40 images was significantly lower than the low-dose MBIRc and ASIR images, and routine-dose ASIR images (p < 0.05). Subjective ratings showed higher image quality for low-dose MBIRNR40, with lower noise, better low-contrast resolution for abdominal structures, and finer lesion contours than those of low-dose MBIRc and ASIR images, and routine-dose ASIR images (p < 0.05). MBIRNR40 with low-contrast resolution preference provides significantly lower noise and better image quality than MBIRc and ASIR in low-dose abdominal CT; significantly better objective and subjective image quality than the routine-dose ASIR with 75% dose reduction.

Evaluation of the Quality of CT Images Acquired with Smart Metal Artifact Reduction Software.

ObjectiveTo evaluate the practical effectiveness of smart metal artifact reduction (SMAR) in reducing artifacts caused by metallic implants.MethodsPatients with metal implants underwent computed tomography (CT) examinations on high definition CT scanner, and the data were reconstructed with adaptive statistical iterative reconstruction (ASiR) with value weighted to 40% and smart metal artifact reduction (SMAR) technology. The comparison was assessed by both subjective and objective assessment between the two groups of images. In terms of subjective assessment, three radiologists evaluated image quality and assigned a score for visualization of anatomic structures in the critical areas of interest. Objectively, the absolute CT value of the difference (ΔCT) and artifacts index (AI) were adopted in this study for the quantitative assessment of metal artifacts.ResultsIn subjective image quality assessment, three radiologists scored SMAR images higher than 40% ASiR images (P<0.01) and the result suggested that visualization of critical anatomic structures around the region of the metal object was significantly improved by using SMAR compared with 40% ASiR. The ΔCT and AI for quantitative assessment of metal artifacts showed that SMAR appeared to be superior for reducing metal artifacts (P<0.05) and indicated that this technical approach was more effective in improving the quality of CT images.ConclusionA variety of hardware (dental filling, embolization coil, instrumented spine, hip implant, knee implant) are processed with the SMAR algorithm to demonstrate good recovery of soft tissue around the metal. This artifact reduction allows for the clearer visualization of structures hidden underneath.

Low-dose CT with adaptive statistical iterative reconstruction for evaluation of urinary stone.

PurposeTo prospectively determine the diagnostic performance of low-dose CT (LDCT) with adaptive statistical iterative reconstruction (ASIR) technique for the detection of urinary stone disease.ResultsThe average DLP and ED was 408.16 ± 119.04 mGy and 6.12 ± 1.79 mSv in CDCT, and 138.19 ± 76.87 mGy and 2.07 ± 1.15 mSv in LDCT, respectively. The dose reduction rate of LDCT was nearly 66.1% for both DLP and ED (P < 0.05). LDCT–80% ASIR images showed great image quality (mean score = 4.09), which was similar to CDCT-FBP images (mean score = 4.17) (P > 0.05), but higher than LDCT-FBP images (mean score = 2.77) (P < 0.05).Materials and Methods70 consetutive patients with clinically suspected urolithiasis underwent non-enhanced CT. Followed by both conventional-dose CT (CDCT) and low-dose CT (LDCT) scans. Automatic tube current modulation (ATCM) scanning was used, with a noise index setting of 13 in CDCT and 25 in LDCT. Reconstructions were performed with filtered back projection (FBP) and different settings of adaptive statistical iterative reconstruction [ASIR(40%, 60%, 80%)]. Urinary calculi (size, location, number), image quality (scale 1–5), image noise (scale 1–3) and diagnostic confidence levels (scale 1–3) were evaluated and measured by two radiologists independently. Radiation dose was recorded by calculating dose length product (DLP) and effective dose (ED). Statistical analyses included Mann-Whitney U test and Paired t tests.ConclusionsLDCT with ASIR can reduce the radiation dose while maintain relatively high image quality in the diagnosis of urinary stone diseases.

Adaptive statistical iterative reconstruction use for radiation dose reduction in pediatric lower-extremity CT: impact on diagnostic image quality.

For the past several years, increased levels of imaging radiation and cumulative radiation to children has been a significant concern. Although several measures have been taken to reduce radiation dose during computed tomography (CT) scan, the newer dose reduction software adaptive statistical iterative reconstruction (ASIR) has been an effective technique in reducing radiation dose. To our knowledge, no studies are published that assess the effect of ASIR on extremity CT scans in children. To compare radiation dose, image noise, and subjective image quality in pediatric lower extremity CT scans acquired with and without ASIR. The study group consisted of 53 patients imaged on a CT scanner equipped with ASIR software. The control group consisted of 37 patients whose CT images were acquired without ASIR. Image noise, Computed Tomography Dose Index (CTDI) and dose length product (DLP) were measured. Two pediatric radiologists rated the studies in subjective categories: image sharpness, noise, diagnostic acceptability, and artifacts. The CTDI (p value = 0.0184) and DLP (p value <0.0002) were significantly decreased with the use of ASIR compared with non-ASIR studies. However, the subjective ratings for sharpness (p < 0.0001) and diagnostic acceptability of the ASIR images (p < 0.0128) were decreased compared with standard, non-ASIR CT studies. Adaptive statistical iterative reconstruction reduces radiation dose for lower extremity CTs in children, but at the expense of diagnostic imaging quality. Further studies are warranted to determine the specific utility of ASIR for pediatric musculoskeletal CT imaging.

Iterative Reconstructions in Reduced-Dose CT: Which Type Ensures Diagnostic Image Quality in Young Oncology Patients?

To compare adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) algorithms for reduced-dose computed tomography (CT). Forty-four young oncology patients (mean age 30 ± 9 years) were included. After routine thoraco-abdominal CT (dose 100%, average CTDIvol 9.1 ± 2.4 mGy, range 4.4-16.9 mGy), follow-up CT was acquired at 50% (average CTDIvol 4.5 ± 1.2 mGy, range 2.2-8.4 mGy) in 29 patients additionally at 20% dose (average CTDIvol 1.9 ± 0.5 mGy, range 0.9-3.4 mGy). Each reduced-dose CT was reconstructed using both ASIR and MBIR. Four radiologists (two juniors and two seniors) blinded to dose and technique read each set of CT images regarding objective and subjective image qualities (high- or low-contrast structures), subjective noise or pixilated appearance, diagnostic confidence, and lesion detection. At all dose levels, objective image noise was significantly lower with MBIR than with ASIR (P < 0.001). The subjective image quality for low-contrast structures was significantly higher with MBIR than with ASIR (P < 0.001). Reduced-dose abdominal CT images of patients with higher body mass index (BMI) were read with significantly higher diagnostic confidence than images of slimmer patients (P < 0.001) and had higher subjective image quality, regardless of technique. Although MBIR images appeared significantly more pixilated than ASIR images, they were read with higher diagnostic confidence, especially by juniors (P < 0.001). Reduced-dose CT during the follow-up of young oncology patients should be reconstructed with MBIR to ensure diagnostic quality. Elevated body mass index does not hamper the quality of reduced-dose CT.

Image quality improvement using model-based iterative reconstruction in low dose chest CT for children with necrotizing pneumonia

BackgroundModel-based iterative reconstruction (MBIR) is a promising reconstruction method which could improve CT image quality with low radiation dose. The purpose of this study was to demonstrate the advantage of using MBIR for noise reduction and image quality improvement in low dose chest CT for children with necrotizing pneumonia, over the adaptive statistical iterative reconstruction (ASIR) and conventional filtered back-projection (FBP) technique.MethodsTwenty-six children with necrotizing pneumonia (aged 2 months to 11 years) who underwent standard of care low dose CT scans were included. Thinner-slice (0.625 mm) images were retrospectively reconstructed using MBIR, ASIR and conventional FBP techniques. Image noise and signal-to-noise ratio (SNR) for these thin-slice images were measured and statistically analyzed using ANOVA. Two radiologists independently analyzed the image quality for detecting necrotic lesions, and results were compared using a Friedman’s test.ResultsRadiation dose for the overall patient population was 0.59 mSv. There was a significant improvement in the high-density and low-contrast resolution of the MBIR reconstruction resulting in more detection and better identification of necrotic lesions (38 lesions in 0.625 mm MBIR images vs. 29 lesions in 0.625 mm FBP images). The subjective display scores (mean ± standard deviation) for the detection of necrotic lesions were 5.0 ± 0.0, 2.8 ± 0.4 and 2.5 ± 0.5 with MBIR, ASIR and FBP reconstruction, respectively, and the respective objective image noise was 13.9 ± 4.0HU, 24.9 ± 6.6HU and 33.8 ± 8.7HU. The image noise decreased by 58.9 and 26.3% in MBIR images as compared to FBP and ASIR images. Additionally, the SNR of MBIR images was significantly higher than FBP images and ASIR images.ConclusionsThe quality of chest CT images obtained by MBIR in children with necrotizing pneumonia was significantly improved by the MBIR technique as compared to the ASIR and FBP reconstruction, to provide a more confident and accurate diagnosis for necrotizing pneumonia.

Model-Based Iterative Reconstruction in CT Enterography.

The purpose of this study was to analyze the performance of pure model-based iterative reconstruction (MBIR) in low-dose CT enterography. Forty-four patients with Crohn disease referred for CT enterography were included. Low-dose modified-protocol and conventional-protocol CT datasets were contemporaneously acquired. Conventional-protocol image formation was performed with 40% adaptive statistical iterative reconstruction (ASIR). Modified-protocol data were reconstructed with 100% MBIR and 40% ASIR. Image quality was assessed subjectively and objectively at six levels. Independent clinical interpretations by two fully blinded radiologists were compared with reference standard consensus reviews by two nonblinded readers who had access to clinical information, previous imaging studies, and medical records. A 74.7% average radiation dose reduction was seen: low-dose modified-protocol effective dose, 1.61 ± 1.18 mSv (size-specific-dose-estimate, 2.47 ± 1.21 mGy); conventional-protocol effective dose, 6.05 ± 2.84 mSv (size-specific-dose-estimate, 9.25 ± 2.9 mGy). Image quality assessment yielded 9372 data points. Objective noise on modified-protocol MBIR images was superior (p < 0.05) to that with the conventional protocol at three of six levels and comparable at the other three levels. Modified-protocol images were superior to conventional-protocol ASIR images (p < 0.05 in all cases) for subjective noise, spatial resolution, contrast resolution, streak artifact, and diagnostic acceptability on coronal reconstructions. Axial diagnostic acceptability was superior for conventional-protocol ASIR (p = 0.76). For both readers, modified-protocol MBIR clinical readings agreed more closely with reference standard readings than did conventional-protocol ASIR readings with regard to bowel wall disease assessment (κ = 0.589 and 0.700 vs 0.583 and 0.564). Overall Crohn disease activity grade (κ = 0.549 and 0.441 vs 0.315 and 0.596) and detection of acute complications (κ = 1.0 and 0.689 vs 0.896 and 0.896) were comparable when evaluated on conventional-protocol ASIR and modified-protocol MBIR images. Low-dose CT enterography with MBIR yields images that are comparable to or superior to conventional images.

CT Dose Reduction for Visceral Adipose Tissue Measurement: Effects of Model-Based and Adaptive Statistical Iterative Reconstructions and Filtered Back Projection

The objective of our study was to evaluate the effects of radiation dose reduction and the reconstruction algorithm used--filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), or model-based iterative reconstruction (MBIR)--on the measurement of abdominal visceral fat using CT. Standard-dose and low-dose abdominal CT examinations were performed simultaneously with automatic exposure control in 59 patients; the noise index for a 5-mm slice thickness was 12 for routine-dose CT and 24 for low-dose CT. The routine-dose CT images were reconstructed using FBP (reference standard), and the low-dose CT images were reconstructed using FBP, ASIR (so-called hybrid iterative reconstruction [IR]), and MBIR (so-called pure IR). In the 236 image series obtained, the visceral fat area was measured. Data were analyzed by the Pearson correlation coefficient test and a Bland-Altman difference analysis. The radiation dose of the low-dose abdominal CT examinations was 73.0% (mean) lower than that of routine-dose CT examinations. Excellent correlations were observed between the visceral fat areas measured on the routine-dose FBP images and those measured on the low-dose FBP, low-dose ASIR, and low-dose MBIR images (r = 0.998, 0.998, and 0.998, respectively; p < 0.001). A Bland-Altman difference analysis revealed excellent agreements, with mean biases of -0.47, -0.41, and 0.18 cm(2) for the visceral fat area between the routine-dose FBP images and the low-dose FBP, low-dose ASIR, and low-dose MBIR images, respectively. A 73.0% reduction of the radiation dose would be possible in CT for the measurement of the abdominal visceral fat regardless of which reconstruction algorithm is used (i.e., FBP, hybrid IR, or pure IR).

Non-contrast CT at comparable dose to an abdominal radiograph in patients with acute renal colic; impact of iterative reconstruction on image quality and diagnostic performance

ObjectivesThe aim was to assess the performance of low-dose non-contrast CT of the urinary tract (LD-CT) acquired at radiation exposures close to that of abdominal radiography using adaptive statistical iterative reconstruction (ASiR).MethodsThirty-three patients with clinically suspected renal colic were prospectively included. Conventional dose (CD-CT) and LD-CT data sets were contemporaneously acquired. LD-CT images were reconstructed with 40 %, 70 % and 90 % ASiR. Image quality was subjectively and objectively measured. Images were also clinically interpreted.ResultsMean ED was 0.48 ± 0.07 mSv for LD-CT compared with 4.43 ± 3.14 mSv for CD-CT. Increasing the percentage ASiR resulted in a step-wise reduction in mean objective noise (p < 0.001 for all comparisons). Seventy % ASiR LD-CT images had higher diagnostic acceptability and spatial resolution than 90 % ASiR LD-CT images (p < 0.001). Twenty-seven calculi (diameter = 5.5 ± 1.7 mm), including all ureteric stones, were correctly identified using 70 % ASiR LD-CT with two false positives and 16 false negatives (diameter = 2.3 ± 0.7 mm) equating to a sensitivity and specificity of 72 % and 94 %. Seventy % ASiR LD-CT had a sensitivity and specificity of 87 % and 100 % for detection of calculi >3 mm.ConclusionReconstruction of LD-CT images with 70 % ASiR resulted in superior image quality than FBP, 40 % ASIR and 90 % ASIR. LD-CT with ASIR demonstrates high sensitivity and specificity for detection of calculi >3 mm.Teaching Points• Low-dose CT studies for urinary calculus detection were performed with a mean dose of 0.48 ± 0.07 mSv• Low-dose CT with 70 % ASiR detected calculi >3 mm with a sensitivity and specificity of 87 % and 100 %• Reconstruction with 70 % ASiR was superior to filtered back projection, 40 % ASiR and 90 % ASiR images

Model-based Iterative Reconstruction: Effect on Patient Radiation Dose and Image Quality in Pediatric Body CT

To retrospectively compare image quality and radiation dose between a reduced-dose computed tomographic (CT) protocol that uses model-based iterative reconstruction (MBIR) and a standard-dose CT protocol that uses 30% adaptive statistical iterative reconstruction (ASIR) with filtered back projection. Institutional review board approval was obtained. Clinical CT images of the chest, abdomen, and pelvis obtained with a reduced-dose protocol were identified. Images were reconstructed with two algorithms: MBIR and 100% ASIR. All subjects had undergone standard-dose CT within the prior year, and the images were reconstructed with 30% ASIR. Reduced- and standard-dose images were evaluated objectively and subjectively. Reduced-dose images were evaluated for lesion detectability. Spatial resolution was assessed in a phantom. Radiation dose was estimated by using volumetric CT dose index (CTDI(vol)) and calculated size-specific dose estimates (SSDE). A combination of descriptive statistics, analysis of variance, and t tests was used for statistical analysis. In the 25 patients who underwent the reduced-dose protocol, mean decrease in CTDI(vol) was 46% (range, 19%-65%) and mean decrease in SSDE was 44% (range, 19%-64%). Reduced-dose MBIR images had less noise (P > .004). Spatial resolution was superior for reduced-dose MBIR images. Reduced-dose MBIR images were equivalent to standard-dose images for lungs and soft tissues (P > .05) but were inferior for bones (P = .004). Reduced-dose 100% ASIR images were inferior for soft tissues (P < .002), lungs (P < .001), and bones (P < .001). By using the same reduced-dose acquisition, lesion detectability was better (38% [32 of 84 rated lesions]) or the same (62% [52 of 84 rated lesions]) with MBIR as compared with 100% ASIR. CT performed with a reduced-dose protocol and MBIR is feasible in the pediatric population, and it maintains diagnostic quality.

Dose reduction with adaptive statistical iterative reconstruction for paediatric CT: phantom study and clinical experience on chest and abdomen CT

To assess the benefit and limits of iterative reconstruction of paediatric chest and abdominal computed tomography (CT). The study compared adaptive statistical iterative reconstruction (ASIR) with filtered back projection (FBP) on 64-channel MDCT. A phantom study was first performed using variable tube potential, tube current and ASIR settings. The assessed image quality indices were the signal-to-noise ratio (SNR), the noise power spectrum, low contrast detectability (LCD) and spatial resolution. A clinical retrospective study of 26 children (M:F = 14/12, mean age: 4years, range: 1-9years) was secondarily performed allowing comparison of 18 chest and 14 abdominal CT pairs, one with a routine CT dose and FBP reconstruction, and the other with 30% lower dose and 40% ASIR reconstruction. Two radiologists independently compared the images for overall image quality, noise, sharpness and artefacts, and measured image noise. The phantom study demonstrated a significant increase in SNR without impairment of the LCD or spatial resolution, except for tube current values below 30-50mA. On clinical images, no significant difference was observed between FBP and reduced dose ASIR images. Iterative reconstruction allows at least 30% dose reduction in paediatric chest and abdominal CT, without impairment of image quality. • Iterative reconstruction helps lower radiation exposure levels in children undergoing CT. • Adaptive statistical iterative reconstruction (ASIR) significantly increases SNR without impairing spatial resolution. • For abdomen and chest CT, ASIR allows at least a 30% dose reduction.

Assessment of a Model-Based, Iterative Reconstruction Algorithm (MBIR) Regarding Image Quality and Dose Reduction in Liver Computed Tomography

The purpose of this study was to assess the image quality of half-dose (HD) liver computed tomography (CT) using a model-based iterative reconstruction algorithm (MBIR) compared with reference dose (RD) using filtered back projection (FBP) and the HD CT images using FBP and adaptive statistical iterative reconstruction (ASIR). A total of 103 patients suspected of having liver metastases underwent liver CT including HD portal venous phase imaging. Among these patients, 73 had undergone RD liver CT reconstructed using FBP, and the HD portal phase CT scans were separately reconstructed using FBP and MBIR. For the other 30 patients, the HD CT images were reconstructed using FBP, ASIR, and MBIR. The CT attenuation coefficients and the mean image noise of various sites, including the liver, the aorta, the main portal vein (MPV), and the subcutaneous fat, were measured, and the contrast-to-noise ratios (CNRs) of the metastatic lesion to the liver and the MPV to the liver were calculated. Two radiologists reviewed each image set with regard to image noise, image quality, lesion conspicuity, and diagnostic acceptability. Compared with RD CT, there was a 46.1% decrease in CT dose index volume with HD CT. Image noise was significantly lower in the HD images reconstructed with MBIR than in both the HD FBP images and the RD FBP images (P < 0.001). Compared with the RD FBP and HD FBP images, the CNRs of the metastatic lesion to the liver and the MPV to the liver were higher in the HD MBIR images (P < 0.001). Despite the presence of the unique whirling artifacts of the MBIR images, the HD MBIR images were of good to excellent quality and were not inferior to RD FBP images regarding the lesion conspicuity, the image quality, and the diagnostic acceptability (P > 0.05). Half-dose MBIR also showed less image noise, higher CNRs, and superior image quality compared with HD ASIR (P < 0.001). The HD MBIR images showed less noise, higher CNR, and better image quality than the HD ASIR and HD FBP images did; they also provided less image noise, higher CNR, and similar image quality compared with those of RD FBP images.

GW24-e2928 Computed tomography metal artifact reduction for evaluation of lead calcification in patients with implantable cardiac defibrillator

ObjectivesPatients with implantable cardiac defibrillator (ICD) may require lead extraction if there is presence of lead fibrosis and calcification but such procedure requires specialist equipment and skills and is associated...

4:02 PM Abstract No. 227 - Optimization of iterative reconstruction technique for CT pulmonary arteriography: systemic assessment in a porcine model

Purpose To evaluate the quantitative and qualitative image quality of pulmonary CT arteriography images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR) scanned at differential radiation doses. Materials and Methods A healthy 56.1 kg Yorkshire pig underwent fluoroscopic placement of a femoral central venous catheter. The catheter was subsequently injected with macerated, previously clotted autologous blood. After pulmonary emboli were visualized in the left lower lobe segmental pulmonary arteries, successive pulmonary arterial CT angiography on a Discovery 750HD MDCT scanner (GE Healthcare) was performed at 700, 400, 200, 100, and 50 mA at 120, 100, and 80 kVp, for a total of 15 scans. Each scan was reconstructed FBP, ASIR (50% blend) and MBIR. Noise (SD) and contrast-to-noise ratios were calculated from ROIs over the left lower lobe segmental pulmonary artery and paraspinous muscle. Selected axial images were scored subjectively for PE visibility and overall image quality. Results Averaged across all doses, MBIR reduced noise and improved contrast to noise ratio (CNR) compared to FBP by 73% and 232%, and reduced noise and improved CNR compared to ASIR by 69% and 110%, respectively. The effect was more pronounced in higher noise settings. Averaged across all doses, MBIR improved subjective image quality and diagnostic sensitivity for pulmonary embolism (PE) compared to FBP by 50% and compared to ASIR by 25%. Subjective improvements in image quality were most pronounced in higher noise settings. At 120 kVp/400 mA, readers scored FBP, ASIR, and MBIR images equally. At 100 mA/120 kVp, readers scored FBP and ASIR images as nondiagnostic for detection of PE, while MBIR images were considered of moderate quality but remained diagnostic for detection of PE. Conclusion MBIR reduced image noise and improved CNR for the pulmonary arteries compared to ASIR and FBP across all dose levels. Furthermore, MBIR resulted in higher subjective image quality and improved diagnostic sensitivity for pulmonary embolism, particularly in higher noise settings.

Comparison of pure and hybrid iterative reconstruction techniques with conventional filtered back projection: Image quality assessment in the cervicothoracic region

ObjectivesTo evaluate the impact on image quality of three different image reconstruction techniques in the cervicothoracic region: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP). MethodsForty-four patients underwent unenhanced standard-of-care clinical computed tomography (CT) examinations which included the cervicothoracic region with a 64-row multidetector CT scanner. Images were reconstructed with FBP, 50% ASIR-FBP blending (ASIR50), and MBIR. Two radiologists assessed the cervicothoracic region in a blinded manner for streak artifacts, pixilated blotchy appearances, critical reproduction of visually sharp anatomical structures (thyroid gland, common carotid artery, and esophagus), and overall diagnostic acceptability. Objective image noise was measured in the internal jugular vein. Data were analyzed using the sign test and pair-wise Student's t-test. ResultsMBIR images had significant lower quantitative image noise (8.88±1.32) compared to ASIR images (18.63±4.19, P<0.01) and FBP images (26.52±5.8, P<0.01). Significant improvements in streak artifacts of the cervicothoracic region were observed with the use of MBIR (P<0.001 each for MBIR vs. the other two image data sets for both readers), while no significant difference was observed between ASIR and FBP (P>0.9 for ASIR vs. FBP for both readers). MBIR images were all diagnostically acceptable. Unique features of MBIR images included pixilated blotchy appearances, which did not adversely affect diagnostic acceptability. ConclusionsMBIR significantly improves image noise and streak artifacts of the cervicothoracic region over ASIR and FBP. MBIR is expected to enhance the value of CT examinations for areas where image noise and streak artifacts are problematic.

Filtered Back Projection, Adaptive Statistical Iterative Reconstruction, and a Model-based Iterative Reconstruction in Abdominal CT: An Experimental Clinical Study

To compare objective and subjective image quality parameters of three image reconstruction algorithms of different generations at routine multidetector computed tomographic (CT) examinations of the abdomen. This institutional review board-approved study included 22 consecutive patients (mean age, 56.1 years ± 15.8 [standard deviation]; mean weight, 79.1 kg ± 14.8) who underwent routine CT examinations of the abdomen. A low-contrast phantom was used for objective quality control. Raw data sets were reconstructed by using filtered back projection (FPB), adaptive statistical iterative reconstruction (ASIR), and a model-based iterative reconstruction (MBIR). Radiologists used a semiquantitative scale (-3 to +3) to rate subjective image quality and artifacts, comparing both FBP and MBIR images with ASIR images. The Wilcoxon test and the intraclass correlation coefficient were used to evaluate the data. Measurements of objective noise and CT numbers of soft tissue structures were compared with analysis of variance. The phantom study revealed an improved detectability of low-contrast targets for MBIR compared with ASIR or FBP. Subjective ratings showed higher image quality for MBIR, with better resolution (median value, 2; range, 1 to 3), lower noise (2; range, 1 to 3), and finer contours (2; range, 1 to 2) compared with ASIR (all P < .001). FBP performed inferiorly (0, range, -2 to 0]; -1 [range, -3 to 0]; 0 [range, -1 to 0], respectively; all, P < .001). Mean interobserver correlation was 0.9 for image perception and 0.7 for artifacts. Objective noise for FBP was 14%-68% higher and for MBIR was 18%-47% lower than that for ASIR (P < .001). The MBIR algorithm considerably improved objective and subjective image quality parameters of routine abdominal multidetector CT images compared with those of ASIR and FBP.

Radiation Dose Reduction at Multidetector CT with Adaptive Statistical Iterative Reconstruction for Evaluation of Urolithiasis: How Low Can We Go?

To evaluate the performance of computed tomographic (CT) examinations at 80 and 100 kV with tube current-time products of 75-150 mA and the effect of adaptive statistical iterative reconstruction (ASIR) on CT image quality in patients with urinary stone disease. In this HIPAA-compliant institutional review board-approved study, verbal consent for prospective low-dose CT and waivers of consent for retrospective review of CT scans were obtained. Between November 2010 and April 2011, 25 patients (15 men, 10 women; mean age, 35 years) with urolithiasis underwent 64-section multidetector CT with 75-150 mA and noise index of 30. Modified protocol was based on body weight (<200 lb [90 kg], 80 kV; >200 lb [90 kg], 100 kV). Images of 5-mm section thickness were reconstructed with filtered back projection (FBP) and 60% and 80% ASIR techniques, with 3-mm coronal and sagittal reformations. Two readers independently reviewed FBP and ASIR data sets for image quality (scale, 1-5), noise (scale , 1-3), and calculi (number, size, location). Confidence levels for urolithiaisis and alternate diagnoses were rated (scale, 1-3). In 13 patients, FBP CT images acquired with the reference standard departmental protocol were available for comparison. Radiation dose was compared between imaging series. Statistical analysis was performed with Wilcoxon signed rank and paired t tests. Modified-protocol FBP images showed low image quality (score, 2.5), with improvement on modified-protocol ASIR images (score, 3.4) (P=.03). All 33 stones (mean diameter, 6.1 mm; range, 2-28 mm) at modified-protocol CT were diagnosed by both readers. In 20 of 25 patients (80%), ASIR images were rated adequate for rendering other diagnoses in the abdomen (score, 2.0), as opposed to FBP images (score, 1.3). Mean radiation dose for modified-protocol CT was 1.8 mGy (1.3 mGy for patients<200 lb; 2.3 mGy for patients>200 lb) in comparison with 9.9 mGy for reference-protocol CT (P=.001). Image quality improvements with ASIR at reduced radiation dose of 1.8 mGy enabled effective evaluation of urinary calculi without substantially affecting diagnostic confidence. © RSNA, 2012.

Radiation Dose Reduction with Hybrid Iterative Reconstruction for Pediatric CT

To assess image quality and radiation dose reduction with hybrid iterative reconstruction of pediatric chest and abdominal computed tomographic (CT) data compared with conventional filtered back projection (FBP). A total of 234 patients (median age, 12 years; age range, 6 weeks to 18 years) underwent chest and abdominal CT in this institutional review board-approved HIPAA-compliant retrospective study. CT was performed with a hybrid adaptive statistical iterative reconstruction (ASIR)-enabled 64-detector row CT scanner. Scanning protocols were adjusted for clinical indication and patient weight to enable acquisition of reduced-dose CT images in all patients, and tube current was further lowered for ASIR protocols. Weight, age, and sex were recorded, and objective noise was measured in the descending thoracic aorta for chest CT and in the liver for abdominal CT. Of the 234 consecutive patients who underwent ASIR-enabled CT (115 chest and 119 abdominal examinations), 70 patients had undergone prior FBP CT. ASIR and FBP CT studies (29 chest and 41 abdominal studies) in these 70 patients were reviewed for image quality, artifacts, and diagnostic confidence by two pediatric radiologists working independently. Data were analyzed with multiple paired t tests. Compared with FBP, ASIR enabled dose reduction of 46.4% (3.7 vs 6.9 mGy) for chest CT and 38.2% (5.0 vs 8.1 mGy) for abdominal CT (P < .0001). Both radiologists deemed image quality of and diagnostic confidence with ASIR and FBP CT images as acceptable, without any artifacts. Despite the lower radiation dose used, ASIR images (chest, 10.7 ± 2.5 [mean ± standard deviation]; abdomen, 11.8 ± 3.4) had substantially less objective noise than did FBP images (chest, 13.3 ± 3.8; abdomen, 13.8 ± 5.2) (P = .001, P =.006, respectively). Use of a hybrid iterative reconstruction technique, such as ASIR, enables substantial radiation dose reduction for pediatric CT when compared with FBP and maintains image quality and diagnostic confidence.