Image Quality Evaluation in Dual-Energy CT of the Chest, Abdomen, and Pelvis in Obese Patients With Deep Learning Image Reconstruction.

OBJECTIVE: The aim of this study was to evaluate image quality in vascular and oncologic dual-energy computed tomography (CT) imaging studies performed with a deep learning (DL)-based image reconstruction algorithm in patients with body mass index of ≥30. METHODS: Vascular and multiphase oncologic staging dual-energy CT examinations were evaluated. Two image reconstruction algorithms were applied to the dual-energy CT data sets: standard of care Adaptive Statistical Iterative Reconstruction (ASiR-V) and TrueFidelity DL image reconstruction at 2 levels (medium and high). Subjective quality criteria were independently evaluated by 4 abdominal radiologists, and interreader agreement was assessed. Signal-to-noise ratio (SNR) and contrast-to-noise ratio were compared between image reconstruction methods. RESULTS: Forty-eight patients were included in this study, and the mean patient body mass index was 39.5 (SD, 7.36). TrueFidelity-High (DL-High) and TrueFidelity-Medium (DL-Med) image reconstructions showed statistically significant higher Likert scores compared with ASiR-V across all subjective image quality criteria ( P < 0.001 for DL-High vs ASiR-V; P < 0.05 for DL-Med vs ASiR-V), and SNRs for aorta and liver were significantly higher for DL-High versus ASiR-V ( P < 0.001). Contrast-to-noise ratio for aorta and SNR for aorta and liver were significantly higher for DL-Med versus ASiR-V ( P < 0.05). CONCLUSIONS: TrueFidelity DL image reconstruction provides improved image quality compared with ASiR-V in dual-energy CTs obtained in obese patients.

CT automated exposure control using a generalized detectability index.

PURPOSE: Identifying an appropriate tube current setting can be challenging when using iterative reconstruction due to the varying relationship between spatial resolution, contrast, noise, and dose across different algorithms. This study developed and investigated the application of a generalized detectability index ( d gen ' ) to determine the noise parameter to input to existing automated exposure control (AEC) systems to provide consistent image quality (IQ) across different reconstruction approaches. METHODS: This study proposes a task-based automated exposure control (AEC) method using a generalized detectability index ( d gen ' ). The proposed method leverages existing AEC methods that are based on a prescribed noise level. The generalized d gen ' metric is calculated using lookup tables of task-based modulation transfer function (MTF) and noise power spectrum (NPS). To generate the lookup tables, the American College of Radiology CT accreditation phantom was scanned on a multidetector CT scanner (Revolution CT, GE Healthcare) at 120 kV and tube current varied manually from 20 to 240 mAs. Images were reconstructed using a reference reconstruction algorithm and four levels of an in-house iterative reconstruction algorithm with different regularization strengths (IR1-IR4). The task-based MTF and NPS were estimated from the measured images to create lookup tables of scaling factors that convert between d gen ' and noise standard deviation. The performance of the proposed d gen ' -AEC method in providing a desired IQ level over a range of iterative reconstruction algorithms was evaluated using the American College of Radiology (ACR) phantom with elliptical shell and using a human reader evaluation on anthropomorphic phantom images. RESULTS: The study of the ACR phantom with elliptical shell demonstrated reasonable agreement between the d gen ' predicted by the lookup table and d ' measured in the images, with a mean absolute error of 15% across all dose levels and maximum error of 45% at the lowest dose level with the elliptical shell. For the anthropomorphic phantom study, the mean reader scores for images resulting from the d gen ' -AEC method were 3.3 (reference image), 3.5 (IR1), 3.6 (IR2), 3.5 (IR3), and 2.2 (IR4). When using the d gen ' -AEC method, the observers' IQ scores for the reference reconstruction were statistical equivalent to the scores for IR1, IR2, and IR3 iterative reconstructions (P > 0.35). The d gen ' -AEC method achieved this equivalent IQ at lower dose for the IR scans compared to the reference scans. CONCLUSIONS: A novel AEC method, based on a generalized detectability index, was investigated. The proposed method can be used with some existing AEC systems to derive the tube current profile for iterative reconstruction algorithms. The results provide preliminary evidence that the proposed d gen ' -AEC can produce similar IQ across different iterative reconstruction approaches at different dose levels.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 3: Vascular, Cardiac, Pulmonary, and Musculoskeletal Applications.

This is the third of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its Task Force on dual-energy computed tomography. This paper, part 3, describes computed tomography angiography and thoracic, cardiac, vascular, and musculoskeletal clinical applications. At the end of the discussion of each application category (vascular, cardiac, pulmonary, and musculoskeletal), we present our consensus opinions on the current clinical utility of the application and opportunities for further research.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 4: Abdominal and Pelvic Applications.

This is the fourth of a series of 4 white papers that represent expert consensus documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This article, part 4, discusses DECT for abdominal and pelvic applications and, at the end of each, will offer our consensus opinions on the current clinical utility of the application and opportunities for further research.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 1: Technology and Terminology.

This is the first of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography (DECT). This article, part 1, describes the fundamentals of the physical basis for DECT and the technology of DECT and proposes uniform nomenclature to account for differences in proprietary terms among manufacturers.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 2: Radiation Dose and Iodine Sensitivity.

This is the second of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This paper, part 2, addresses radiation dose and iodine sensitivity in dual-energy computed tomography.

Image-based quantification of 3D morphology for bifurcations in the left coronary artery: Application to stent design.

BACKGROUND: Improved strategies for stent-based treatment of coronary artery disease at bifurcations require a greater understanding of artery morphology. OBJECTIVE: We developed a workflow to quantify morphology in the left main coronary (LMCA), left anterior descending (LAD), and left circumflex (LCX) artery bifurcations. METHODS: Computational models of each bifurcation were created for 55 patients using computed tomography images in 3D segmentation software. Metrics including cross-sectional area, length, eccentricity, taper, curvature, planarity, branching law parameters, and bifurcation angles were assessed using open-sources software and custom applications. Geometric characterization was performed by comparison of means, correlation, and linear discriminant analysis (LDA). RESULTS: Differences between metrics suggest dedicated or multistent approaches should be tailored for each bifurcation. For example, the side branch of the LCX (i.e., obtuse marginal; OM) was longer than that of the LMCA (i.e., LCXprox) and LAD (i.e., first diagonal; D1). Bifurcation metrics for some locations (e.g., LMCA Finet ratio) provide results and confidence intervals agreeing with prior findings, while revised metric values are presented for others (e.g., LAD and LCX). LDA revealed several metrics that differentiate between artery locations (e.g., LMCA vs. D1, LMCA vs. OM, LADprox vs. D1, and LCXprox vs. D1). CONCLUSIONS: These results provide a foundation for elucidating common parameters from healthy coronary arteries and could be leveraged in the future for treating diseased arteries. Collectively the current results may ultimately be used for design iterations that improve outcomes following implantation of future dedicated bifurcation stents. © 2015 Wiley Periodicals, Inc.

Pancreas transplant imaging: how I do it.

Pancreas transplantation aims to restore physiologic normoglycemia in diabetic patients with glomerulopathy and avoid or delay the onset of diabetic retinopathy and arteriopathy. Simultaneous pancreas-kidney transplant is the most common approach, using a cadaveric pancreas donation in conjunction with either cadaveric or live donor renal transplant. Alternative techniques include pancreas after kidney transplant, in which the pancreas transplant is performed some years after renal transplant. Pancreas transplant alone is utilized rarely in diabetic patients with compensated renal function. Pancreas grafts have vascular and enteric connections that vary in their anatomic approach, and understanding of this is critical for imaging with ultrasonography, computed tomography, or magnetic resonance imaging. Imaging techniques are directed to display the pancreatic transplant arterial and venous vasculature, parenchyma, and intestinal drainage pathway. Critical vascular information includes venous thrombosis (partial or complete), arterial occlusion, or aneurysm. Parenchymal abnormalities are nonspecific and occur in pancreatitis, graft rejection, and subsequent graft ischemia. Peripancreatic fluid collections include hematoma/seroma, pseudocyst, and abscess. The latter two are related to pancreatitis, duct disruption, or leak from the duodenojejunostomy. An understanding of transplant anatomy and complications will lead to appropriate use of imaging techniques to diagnose or exclude important complications.

The effects of gantry tilt on breast dose and image noise in cardiac CT.

PURPOSE: This study investigated the effects of tilted-gantry acquisition on image noise and glandular breast dose in females during cardiac computed tomography (CT) scans. Reducing the dose to glandular breast tissue is important due to its high radiosensitivity and limited diagnostic significance in cardiac CT scans. METHODS: Tilted-gantry acquisition was investigated through computer simulations and experimental measurements. Upon IRB approval, eight voxelized phantoms were constructed from previously acquired cardiac CT datasets. Monte Carlo simulations quantified the dose deposited in glandular breast tissue over a range of tilt angles. The effects of tilted-gantry acquisition on breast dose were measured on a clinical CT scanner (CT750HD, GE Healthcare) using an anthropomorphic phantom with MOSFET dosimeters in the breast regions. In both simulations and experiments, scans were performed at gantry tilt angles of 0°-30°, in 5° increments. The percent change in breast dose was calculated relative to the nontilted scan for all tilt angles. The percent change in noise standard deviation due to gantry tilt was calculated in all reconstructed simulated and experimental images. RESULTS: Tilting the gantry reduced the breast dose in all simulated and experimental phantoms, with generally greater dose reduction at increased gantry tilts. For example, at 30° gantry tilt, the dosimeters located in the superior, middle, and inferior breast regions measured dose reductions of 74%, 61%, and 9%, respectively. The simulations estimated 0%-30% total breast dose reduction across the eight phantoms and range of tilt angles. However, tilted-gantry acquisition also increased the noise standard deviation in the simulated phantoms by 2%-50% due to increased pathlength through the iodine-filled heart. The experimental phantom, which did not contain iodine in the blood, demonstrated decreased breast dose and decreased noise at all gantry tilt angles. CONCLUSIONS: Tilting the gantry reduced the dose to the breast, while also increasing noise standard deviation. Overall, the noise increase outweighed the dose reduction for the eight voxelized phantoms, suggesting that tilted gantry acquisition may not be beneficial for reducing breast dose while maintaining image quality.

Noninvasive assessment of liver fibrosis in adult patients following the Fontan procedure.

OBJECTIVE: Recent data indicate that patients after the Fontan procedure are at risk for significant liver dysfunction; however, the prevalence and extent of liver disease in the Fontan population remains unknown. Furthermore, limited data exist in regard to screening for liver disease in adult Fontan patients. We sought to determine the prevalence of liver disease in adult patients following the Fontan procedure using computed tomography (CT) and serum biomarkers of liver fibrosis. DESIGN: Adult Fontan patients underwent screening for liver disease as part of their annual evaluation. Screening consisted of laboratory evaluation and dual-phase liver CT scan. Laboratory evaluation included analysis of liver function, viral hepatitis serologies, and FibroSURE panel (LabCorp), a test that analyzes the results of serum biomarkers to provide a quantitative surrogate marker for liver fibrosis. RESULTS: Sixteen patients, mean age 30.3 (range 20-41) years, were enrolled in the study. Mean length of follow-up from time of Fontan palliation was 20.5 (range 11-33) years. No patients had serologic evidence of viral hepatitis or synthetic liver dysfunction. Twelve patients (75%) had abnormal FibroSURE scores, seven (44%) had elevated FibroSURE scores predictive of Metavir fibrosis stage F2 or greater on liver biopsy, and one (6%) had a FibroSURE score predictive of cirrhosis on biopsy. All 16 patients had abnormal radiologic liver findings identified on CT, including heterogeneous enhancement in 11 (69%), varices in six (38%), and liver nodules in five patients (31%). Length of time since Fontan surgery correlated significantly with an elevated FibroSURE score (P = .05) and having more CT scan abnormalities (P = .04). CONCLUSIONS: Liver fibrosis detected by serum biomarkers and dual phase CT scan is common in adult patients following the Fontan procedure. Further studies are needed to determine the long-term clinical significance of these findings.

ACR Appropriateness Criteria(®) on suspected lower extremity deep vein thrombosis.

Lower extremity deep vein thrombosis (DVT) is a common clinical concern, with an incidence that increases with advanced age. DVT typically begins below the knee but may extend proximally and result in pulmonary embolism. Pulmonary embolism can occur in 50% to 60% of patients with untreated DVT and can be fatal. Although clinical examination and plasma d-dimer blood evaluation can often predict the presence of DVT, imaging remains critical for the diagnostic confirmation and treatment planning of DVT. Patients with above-the-knee or proximal DVT have a high risk for pulmonary embolism and are recommended to receive anticoagulation therapy. On the other hand, patients with below-the-knee or distal DVT rarely experience pulmonary embolism, and anticoagulation therapy in these patients remains controversial. However, one sixth of patients with distal DVT may experience extension of their thrombus above the knee and therefore are recommended to undergo serial imaging assessment at 1 week to exclude proximal DVT extension if anticoagulation therapy is not initiated. Ultrasound is the preferred imaging method for evaluation of patients with newly suspected lower extremity DVT. Magnetic resonance and CT venography can be especially helpful for the evaluation of suspected DVT in the pelvis and thigh. Contrast x-ray venography, the historic gold standard for DVT assessment, is now less commonly performed and primarily reserved for patients with more complex presentations such as those with suspected recurrent acute DVT.

ACR Appropriateness Criteria® on upper gastrointestinal bleeding.

Upper gastrointestinal bleeding is a significant cause of morbidity and mortality, affecting 36 to 48 per 100,000 persons annually. Aggressive resuscitation and upper endoscopy remain the cornerstones of therapy; however, in cases refractory to endoscopic diagnosis and management, radiology plays an increasingly vital and often lifesaving role, thanks to improvements in both imaging and interventional techniques. The various etiologies of upper gastrointestinal bleeding are discussed along with specific management recommendations based on an extensive literature review of current radiographic methods.

Managing incidental findings on abdominal CT: white paper of the ACR incidental findings committee.

As multidetector CT has come to play a more central role in medical care and as CT image quality has improved, there has been an increase in the frequency of detecting "incidental findings," defined as findings that are unrelated to the clinical indication for the imaging examination performed. These "incidentalomas," as they are also called, often confound physicians and patients with how to manage them. Although it is known that most incidental findings are likely benign and often have little or no clinical significance, the inclination to evaluate them is often driven by physician and patient unwillingness to accept uncertainty, even given the rare possibility of an important diagnosis. The evaluation and surveillance of incidental findings have also been cited as among the causes for the increased utilization of cross-sectional imaging. Indeed, incidental findings may be serious, and hence, when and how to evaluate them are unclear. The workup of incidentalomas has varied widely by physician and region, and some standardization is desirable in light of the current need to limit costs and reduce risk to patients. Subjecting a patient with an incidentaloma to unnecessary testing and treatment can result in a potentially injurious and expensive cascade of tests and procedures. With the participation of other radiologic organizations listed herein, the ACR formed the Incidental Findings Committee to derive a practical and medically appropriate approach to managing incidental findings on CT scans of the abdomen and pelvis. The committee has used a consensus method based on repeated reviews and revisions of this document and a collective review and interpretation of relevant literature. This white paper provides guidance developed by this committee for addressing incidental findings in the kidneys, liver, adrenal glands, and pancreas.

Contrast-induced nephropathy after a second contrast exposure.

BACKGROUND: The risk of contrast-induced nephropathy (CIN) after repeated contrast exposure has not been evaluated. METHODS: We prospectively evaluated the effects of two contrast exposures during an investigational study of a new computerized tomography (CT) scanner. Adult subjects who underwent a variety of contrast-enhanced imaging procedures with conventional apparatus, as part of routine care, were invited to undergo a second contrast-enhanced research scan. Subjects were required to have an estimated glomerular filtration rate (eGFR) >60 mL/min/1.73 m(2) and a serum creatinine (sCr) value measured immediately prior to the second contrast exposure that was <125% of that measured prior to the first imaging study. RESULTS: Twenty-eight subjects underwent a second contrast exposure after a mean interval of 20 +/- 13 days (75% males, 89% Caucasians, 21% diabetics, mean age 60.6 +/- 6 years, mean contrast volume 130 +/- 42 mL). There was a significant increase in mean sCr and decline in eGFR after the second contrast exposure (sCr 0.93 +/- 0.14 vs. 0.86 +/- 0.15 mg/dL prior, p = 0.027; eGFR 83.9 +/- 13.5 vs. 89.8 +/- 13 mL/min/1.73 m(2) prior, p = 0.028). Four subjects (14.3% of the population) developed CIN. CONCLUSION: Even in subjects with relatively preserved renal function there is a notable risk of CIN after repeated contrast exposure. This conclusion was unaltered by several sensitivity analyses.

CT angiography of the lower extremities.

CT angiography (CTA) of the lower extremities has evolved into a robust noninvasive angiographic technique with the advent of 16 and 64 multidetector computed tomographic systems and advances in system design. CTA has displaced conventional catheter arteriography in a large range of applications and is predominantly used in the evaluation of atherosclerotic peripheral arterial occlusive disease in symptomatic patients who are candidates for intervention. Other disease entities including atheroembolism and thromboembolism, aneurysmal disease, and arteritides including Buerger disease and Takayasu arteritis can be precisely evaluated by CTA. Particular applications include arterial vascular mapping for free flap transfers and fibular grafts and evaluation of trauma, before and following orthopedic and plastic surgery interventions. Patients with intravascular stents and arterial bypass grafts who usually undergo serial evaluation by noninvasive, nonangiographic testing are potential candidates for angiographic study when clinical findings of noninvasive tests are in disagreement. The key to a successful clinical application is in understanding how to acquire, display, and interpret high-quality CTA in diverse clinical circumstances.

Prospective and retrospective ECG gating for thoracic CT angiography: a comparative study.

OBJECTIVE: The objective of our study was to compare radiation dose, contrast load, thoracic aortic attenuation value, and image quality parameters of MDCT thoracic aortography performed with prospective and retrospective cardiac gating. MATERIALS AND METHODS: Studies were performed on 80 patients (prospective ECG gating, n = 40; retrospective ECG gating, n = 40) either being evaluated for thoracic aortic aneurysm (n = 23) or aortic dissection (n = 36) or undergoing postsurgical or postintervention follow-up (n = 21). Image acquisition parameters and radiation dose (CT dose index volume [CTDI(vol)] and dose-length product [DLP]) were obtained from image archival data. Contrast load and aortic attenuation values were obtained from a data registry. The comparative degrees of motion artifact and banding artifact were assessed on parasagittal maximum-intensity-projection (MIP) images and reformatted images in the plane of the aortic valve. RESULTS: CTDI(vol) and DLP in the prospective ECG-gating group was 28.8 +/- 2.12 mGy (mean +/- SD) and 833.7 +/- 115.77 mGy/cm, respectively, which are significantly lower (p < 0.001) than those values in the retrospective ECG-gating group (74.7 +/- 13.42 mGy and 2,547.3 +/- 553.27 mGy/cm). The average contrast load in the prospective gating group was 109.1 +/- 14.74 mL and in the retrospective gating group, 101.3 +/- 10.45 mL (p < 0.05). The average aortic attenuation values (in Hounsfield units) for the prospective and retrospective ECG-gated groups were 447.6 and 350.2 HU, respectively, for the mid ascending aorta, 413.6 and 325.7 HU for the mid aortic arch, 418.2 and 327.6 HU for the mid descending aorta, and 355.0 and 306.2 HU for the supraceliac aorta. Subjective scores of motion artifact and banding artifact were equivalent between the two groups. CONCLUSION: Compared with retrospective ECG-gated thoracic CT angiography, prospective ECG-gated thoracic CT angiography was associated with a lower radiation dose, slightly increased contrast load, increased aortic attenuation values, and equivalent image quality.

ACR appropriateness criteria on recurrent symptoms following lower-extremity angioplasty.

Lower-extremity arteriopathy patients can be managed nonsurgically, but there is no standard algorithm for follow-up. The authors present a consensus on appropriate postangioplasty studies in the setting of claudication or a threatened limb. Physical examination with measurements of the ankle-brachial index should be the first step in patients with recurrent symptoms. When there is high clinical suspicion for a threatened limb, the patient should proceed directly to catheter angiography for possible reintervention. However, in the setting of claudication alone, segmental Doppler pressures and pulse volume recordings are the initial test of choice. Magnetic resonance angiography or ultrasound can be used in conjunction to further characterize lesions with more detail. Computed tomographic angiography may also be used to image lower-extremity vasculature but is limited by the presence of large amounts of vascular calcifications. Novel techniques, including dual-energy computed tomographic angiography and noncontrast magnetic resonance angiography, may provide clinicians with alternative approaches in patients with large amounts of vascular calcifications and renal insufficiency, respectively.