Small Intracranial Aneurysms: Diagnostic Accuracy of CT Angiography.

Purpose To assess the accuracy of computed tomographic (CT) angiography for diagnosis of cerebral aneurysms 5 mm or smaller, with digital subtraction angiography (DSA) as the reference standard, in a large patient cohort Materials and Methods This retrospective study was approved by the local institutional review board with a waiver of written informed consent. A total of 1366 patients who underwent cerebral CT angiography followed by DSA were included. The performance of CT angiography for depiction of aneurysms was evaluated by two readers on a per-patient and per-aneurysm basis and based on size of aneurysm, location, and status of rupture. The performance of CT angiography for diagnosis of aneurysms of different size, location, and rupture status was compared by using χ2 test. κ statistic was used to assess interreader agreement for diagnosis of aneurysms. Results Of 1366 patients, 579 patients had 711 small aneurysms at DSA. By using DSA as the reference standard, the respective sensitivity, specificity, and accuracy of CT angiography for readers 1 and 2 for detection of small aneurysms on a per-patient basis were 97.1% (562 of 579) and 97.4% (564 of 579), 98.5% (451 of 458) and 99.1% (454 of 458), and 97.7% (1013 of 1037) and 98.2% (1018 of 1037) and those on a per-aneurysm basis were 95.2% (677 of 711) and 95.4% (678 of 711), 96.6% (451 of 467) and 97.0% (454 of 468), and 95.8% (1128 of 1178) and 96.0% (1132 of 1179). The sensitivities of CT angiography were lower for detection of aneurysms smaller than 3 mm and unruptured compared with aneurysms that were 3-5 mm and ruptured (P < .001). No difference existed for the sensitivities of CT angiography for diagnosis of aneurysms in the anterior versus posterior circulation (P > .0167). Excellent or good interreader agreement was found for detection of intracranial aneurysms on a per-patient (κ = 0.982) and per-aneurysm (κ = 0.748) basis. Conclusion This large cohort study demonstrated that CT angiography had high accuracy for detection of small cerebral aneurysms, including those smaller than 3 mm. © RSNA, 2017 Online supplemental material is available for this article.

Detection of pulmonary fat embolism with dual-energy CT: an experimental study in rabbits.

OBJECTIVES: To evaluate the use of dual-energy CT imaging of the lung perfused blood volume (PBV) for the detection of pulmonary fat embolism (PFE). METHODS: Dual-energy CT was performed in 24 rabbits before and 1 hour, 1 day, 4 days and 7 days after artificial induction of PFE via the right ear vein. CT pulmonary angiography (CTPA) and lung PBV images were evaluated by two radiologists, who recorded the presence, number, and location of PFE on a per-lobe basis. Sensitivity, specificity, and accuracy of CTPA and lung PBV for detecting PFE were calculated using histopathological evaluation as the reference standard. RESULTS: A total of 144 lung lobes in 24 rabbits were evaluated and 70 fat emboli were detected on histopathological analysis. The overall sensitivity, specificity and accuracy were 25.4 %, 98.6 %, and 62.5 % for CTPA, and 82.6 %, 76.0 %, and 79.2 % for lung PBV. Higher sensitivity (p < 0.001) and accuracy (p < 0.01), but lower specificity (p < 0.001), were found for lung PBV compared with CTPA. Dual-energy CT can detect PFE earlier than CTPA (all p < 0.01). CONCLUSION: Dual-energy CT provided higher sensitivity and accuracy in the detection of PFE as well as earlier detection compared with conventional CTPA in this animal model study. KEY POINTS: • Fat embolism occurs commonly in patients with traumatic bone injury. • Dual-energy CT improves diagnostic performance for pulmonary fat embolism detection. • Dual-energy CT can detect pulmonary fat embolism earlier than CTPA.

Image quality, radiation dose, and diagnostic accuracy of prospectively ECG-triggered high-pitch coronary CT angiography at 70 kVp in a clinical setting: comparison with invasive coronary angiography.

PURPOSE: To investigate image quality, radiation dose, and diagnostic performance of prospectively ECG-triggered high-pitch coronary CT angiography (CCTA) at 70 kVp compared to invasive coronary angiography (ICA) as reference standard. MATERIALS AND METHODS: Forty-three patients underwent prospectively ECG-triggered high-pitch CCTA at 70 kVp using 30 cc (11 g iodine) contrast medium and ICA. Subjective and objective image quality was evaluated for each CCTA study. CCTA performance for diagnosing ≥50% stenosis was assessed. Results were stratified according to heart rate (HR), body mass index (BMI), Agatston score, and image quality. RESULTS: At CCTA, 94.3% (500/530) of coronary segments were of diagnostic quality. Using ICA as reference standard, sensitivity and accuracy were 100% and 93.0% on a per-patient basis. Per-vessel and per-segment performances were 92.2% and 89.5%; 79.5% and 88.3%, respectively. No differences were found in diagnostic accuracy between different HR, BMI, and calcification subgroups (all P > 0.05) on a per-patient basis. However, low image quality reduced diagnostic accuracy on a per-patient, per-vessel and per-segment basis (all P < 0.05). The mean effective radiation dose was 0.2 ± 0.0 mSv. CONCLUSION: Our presented protocol results in an effective radiation dose of 0.2 mSv and high diagnostic accuracy for stenosis detection in a selected, non-obese population. KEY POINTS: Prospectively ECG-triggered high-pitch CCTA at 70 kVp is feasible. This protocol has a high diagnostic accuracy for stenosis detection. The mean effective radiation dose was 0.2 ± 0.0 mSv. Only 30 cc of contrast material is used in this protocol. Low image quality reduced diagnostic accuracy of CCTA.

Image quality and radiation dose of lower extremity CT angiography at 70 kVp on an integrated circuit detector dual-source computed tomography.

BACKGROUND: Despite the well-established requirement for radiation dose reduction there are few studies examining the potential for lower extremity CT angiography (CTA) at 70 kVp. PURPOSE: To compare the image quality and radiation dose of lower extremity CTA at 70 kVp using a dual-source CT system with an integrated circuit detector to similar studies at 120 kVp. MATERIAL AND METHODS: A total of 62 patients underwent lower extremity CTA. Thirty-one patients were examined at 70 kVp using a second generation dual-source CT with an integrated circuit detector (70 kVp group) and 31 patients were evaluated at 120 kVp using a first generation dual-source CT (120 kVp group). The attenuation and image noise were measured and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Two radiologists assessed image quality. Radiation dose was compared. RESULTS: The mean attenuation of the 70 kVp group was higher than the 120 kVp group (575 ± 149 Hounsfield units [HU] vs. 258 ± 38 HU, respectively, P < 0.001) as was SNR (44.0 ± 22.0 vs 32.7 ± 13.3, respectively, P = 0.017), CNR (39.7 ± 20.6 vs 26.6 ± 11.7, respectively, P = 0.003) and the mean image quality score (3.7 ± 0.1 vs. 3.2 ± 0.3, respectively, P < 0.001). The inter-observer agreement was good for the 70 kVp group and moderate for the 120 kVp group. The dose-length product was lower in the 70 kVp group (264.5 ± 63.1 mGy × cm vs. 412.4 ± 81.5 mGy × cm, P < 0.001). CONCLUSION: Lower extremity CTA at 70 kVp allows for lower radiation dose with higher SNR, CNR, and image quality when compared with standard 120 kVp.

Hemodynamic alterations in unilateral chronic middle cerebral artery stenosis patients and the effect of percutaneous transluminal angioplasty and stenting: a perfusion-computed tomography study.

BACKGROUND: The Stenting and Aggressive Medical Management for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial indicated that most patients with symptomatic intracranial atherosclerosis are not good candidates for percutaneous transluminal angioplasty and stenting (PTAS) because of a higher complication risk than with conservative treatment. However, enrollment of SAMMPRIS patients was based on lesion severity only, without functional imaging. PURPOSE: To determine whether perfusion computed tomography (PCT) can effectively evaluate hemodynamic compromise in unilateral chronic middle cerebral artery stenosis and the alterations of hemodynamics after PTAS. MATERIAL AND METHODS: In this prospective study, 89 patients with unilateral middle cerebral artery (MCA) stenosis/occlusion were enrolled and classified into four groups according to the degree of stenosis. Cerebral hemodynamics was evaluated by measuring cerebral blood flow (CBF), cerebral blood volume (CBV), and time to peak (TTP) in the ipsilateral and contralateral hemispheres by PCT before and after intervention with PTAS. Differences in hemodynamic parameters before and after intervention were analyzed. RESULTS: Three different hemodynamic patterns were observed in these patients. Patients with severe MCA stenosis (70-99%) or MCA occlusion demonstrated a significant increase of ipsilateral CBV and TTP, indicating hemodynamic compromise. Ten severe stenosis patients with recurrent ischemic symptoms despite of maximal conservative therapy were selected for PTAS. PTAS induced a rapid recovery of cerebral hemodynamics (especially TTP) at 1 week post intervention. CONCLUSION: PCT appears to be a valuable noninvasive technique to evaluate hemodynamic compromise in unilateral chronic MCA stenosis and the improvements after PTAS.

Pulmonary embolism and renal vein thrombosis in patients with nephrotic syndrome: prospective evaluation of prevalence and risk factors with CT.

PURPOSE: To prospectively determine the prevalence of pulmonary embolism ( PE pulmonary embolism ) and renal vein thrombosis ( RVT renal vein thrombosis ) with computed tomography (CT) and to identify markers predictive of PE pulmonary embolism and/or RVT renal vein thrombosis in a large consecutive cohort of patients with nephrotic syndrome. MATERIALS AND METHODS: This study was approved by the local institutional review board, and all patients or their guardians provided written informed consent. Consecutive patients with nephrotic syndrome (24-hour urine protein > 3.5 g) underwent combined CT pulmonary angiography for PE pulmonary embolism and renal CT venography for RVT renal vein thrombosis . Prevalence of PE pulmonary embolism and/or RVT renal vein thrombosis was estimated for different ages, sexes, and histopathologic types of nephrotic syndrome. Multivariate analysis was used to determine independent predictors for PE pulmonary embolism and/or RVT renal vein thrombosis in patients with nephrotic syndrome. RESULTS: There were 512 patients in the study cohort (331 male patients, 181 female patients; mean age, 37 years ± 17 [standard deviation]; range, 9-81 years), including 80 children. One hundred eighty (35%) of 512 patients had PE pulmonary embolism and/or RVT renal vein thrombosis , with PE pulmonary embolism the more common condition (85% [153 of 180]). PE pulmonary embolism was associated with RVT renal vein thrombosis in 85 (56%) of 153 patients and was isolated in 68 patients (44%). Most patients with PE pulmonary embolism (84% [128 of 153]) were asymptomatic. One hundred twelve (22%) of 505 patients had RVT renal vein thrombosis . PE pulmonary embolism and/or RVT renal vein thrombosis was found in 15 (19%) of 80 children with nephrotic syndrome, while 165 (38%) of 432 adult patients with nephrotic syndrome had PE pulmonary embolism and/or RVT renal vein thrombosis (P = .001). Membranous nephropathy was the most common histopathologic type associated with PE pulmonary embolism and/or RVT renal vein thrombosis (48% [88 of 183]). Membranous nephropathy, age greater than 60 years, high hemoglobin level, long prothrombin time, and high creatinine level were independent predictors of PE pulmonary embolism and/or RVT renal vein thrombosis (P < .05 for all). CONCLUSION: PE pulmonary embolism and RVT renal vein thrombosis are common in patients with nephrotic syndrome. PE pulmonary embolism is more common than RVT renal vein thrombosis , is most often asymptomatic, and is most frequently found in patients with membranous nephropathy. A high index of suspicion and a low threshold for diagnostic work-up is warranted in these patients.

High-pitch computed tomography pulmonary angiography with iterative reconstruction at 80 kVp and 20 mL contrast agent volume.

OBJECTIVES: To evaluate the image quality, radiation dose and diagnostic accuracy of 80kVp, high-pitch CT pulmonary angiography (CTPA) with iterative reconstruction using 20 ml of contrast agent. METHODS: One hundred patients with suspected pulmonary embolism (PE) were randomly divided into two groups (n = 50 each; group A, 100 kVp, 1.2 pitch, 60 ml of contrast medium and filtered back projection algorithm; group B, 80 kVp, 2.2 pitch, 20 ml of contrast medium and sinogram affirmed iterative reconstruction). Image quality, diagnostic accuracy and radiation dose were evaluated and compared. RESULTS: Mean CT numbers of pulmonary arteries in group B were higher than those in group A (all P < 0.001). Contrast-to-noise ratio and signal-to-noise ratio of group B were higher than those of group A (both P < 0.001). There was no significant difference in subjective image quality scores between two groups (P = 0.807). The interobserver agreement was excellent (k = 0.836). There was no significant difference in diagnostic accuracy between the two groups (P > 0.05). Compared with group A, radiation dose of group B was reduced by 50.3% (P < 0.001). CONCLUSIONS: High-pitch CTPA at 80 kVp can obtain sufficient image quality in normal-weight individuals with 20 ml of contrast agent and half the radiation dose of a conventional CTPA protocol. KEY POINTS: CTPA is feasible at 80 kVp using only 20 ml of contrast agent. High-pitch CTPA at 80 kVp has an effective dose under 1 mSv. This CTPA protocol can obtain sufficient image quality in normal-weight individuals.

Multidetector computed tomography of superior mesenteric artery: anatomy and pathologies.

The recent introduction of multidetector computed tomography scanners has significantly improved computed tomography angiographic (CTA) applications, especially for the evaluation of medium- and small-arterial structures. CTA of the superior mesenteric artery has been reported previously. However, there have been few systematic and detailed reviews of the superior mesenteric artery pathologies that use CTA. The purpose of this pictorial essay is mainly to review the various superior mesenteric artery pathologies at CTA with our own experiences.

Dual-energy CT lung ventilation/perfusion imaging for diagnosing pulmonary embolism.

OBJECTIVES: To evaluate the feasibility and findings of combined dual-energy computed tomography (DECT) lung ventilation/perfusion imaging in patients with suspected pulmonary embolism (PE). METHODS: This study was institutional review board-approved and written informed consent was obtained from each patient. Thirty-two subjects (aged 11-61 years) underwent combined xenon-enhanced ventilation and iodine-enhanced perfusion DECT. Ventilation, perfusion and morphological information were visually interpreted. Ventilation/perfusion information was classified as mismatch (differing patterns) or match (concordant patterns). Adverse reactions and radiation doses were recorded for each subject. RESULTS: Of 32 patients undergoing xenon-enhanced DECT, six patients reported adverse reactions (shortness of breath, n = 2; mild dizziness, n = 3; limb numbness, n = 1). Twenty-eight of 32 patients could be included into the data analysis. PE was detected in 10/28 patients. PE-related ventilation/perfusion mismatch was found in 17 lung lobes in 8/10 patients and matched ventilation/perfusion was detected in 2 patients. Eighteen patients had no PE. In this group, there was no case of a ventilation/perfusion mismatch. Matched ventilation/perfusion impairment was seen in one patient. The overall radiation dose from two DECT acquisitions was 4.8 ± 1.4 mSv (range 2.7-7.5 mSv). CONCLUSIONS: DECT lung ventilation/perfusion imaging is feasible and can visualise ventilation/perfusion match or mismatch in patients with suspected PE. KEY POINTS: • Combined dual-energy CT lung ventilation/perfusion imaging is feasible. • Combined dual-energy CT ventilation/perfusion imaging provides lung morphological and functional information. • Dual-energy CT can demonstrate ventilation/perfusion mismatch in patients with pulmonary embolism.

Dual-energy CT of the lung.

OBJECTIVE: The introduction of dual-energy CT (DECT) has ushered in the ability of material differentiation and tissue characterization beyond the traditional CT attenuation scale. This quality has been exploited for visualizing and quantifying the specific tissue content using radiographic contrast agents, such as iodine-based contrast media or inhaled xenon gas. Applications of this paradigm in the thorax include characterization of the pulmonary blood pool in the setting of acute or chronic pulmonary embolism (PE) and characterization of diseases of the lung parenchyma. Selective xenon detection is being explored for imaging of lung ventilation. In addition, the usefulness of DECT-based selective iodine uptake measurements has been described for the diagnosis and surveillance of thoracic malignancies. This article reviews the current applications of DECT-based imaging techniques in the chest with an emphasis on the diagnosis and characterization of pulmonary thromboembolic disorders. CONCLUSION: DECT can provide both anatomic and functional information about the lungs in a variety of pulmonary disease states based on a single contrast-enhanced CT examination. This quality has been shown to improve the diagnosis of acute and chronic PEs, other vascular disorders, lung malignancies, and parenchymal diseases. Further developments in DECT techniques and CT scanner technology will further foster and enhance the utility of this application and open new avenues in lung imaging.

[Incidence and classification diagnosis of coronary artery fistula at dual-source CT coronary angiography].

OBJECTIVE: To evaluate the incidence, types and clinical significance of coronary artery fistula (CAF) on CT coronary angiography (CTCA). METHODS: A total of 48 533 consecutive patients undergoing CTCA at 4 Chinese hospitals were retrospectively analyzed. The incidence, types and clinical significance of CAF were retrospectively summarized. RESULTS: One hundred and two patients had CAF with the incidence of 0.21% (102/48 533). Among them, coronary to pulmonary artery fistulas were seen in 92 patients (90.2%, 92/102), coronary to right atrium fistula in 4 (3.9%, 4/102), coronary to right ventricular fistula in 2 (2.0%, 2/102), coronary to right ventricular fistula in 2 (2.0%, 2/102), coronary to left atrium fistula in 1 (1.0%, 1/102) and coronary to small cardiac vein in 1 (1.0%, 1/102). Among 92 coronary to pulmonary artery fistulas, fistulas originated from both coronary arteries in 46 patients (50.0%, 46/92), from left coronary artery in 28 (30.4%, 28/92) and right coronary artery in 11 (12.0%, 11/92) and the remaining 7 (7.6%, 7/92) coronary to pulmonary artery fistulas were associated with extracardiac communications. CONCLUSION: The incidence of CAF is 0.21% with a predominance of coronary to pulmonary artery fistulas (90.2%). The most common type of CAF is coronary to pulmonary artery fistulas from both coronary arteries (50.0%). Dual source CTCA can clearly visualize types and abnormal vessels so that it plays an important role in the diagnosis and preoperative evaluation of CAF.

Dual-energy CT angiography in the evaluation of intracranial aneurysms: image quality, radiation dose, and comparison with 3D rotational digital subtraction angiography.

OBJECTIVE: The purpose of this study was to evaluate the image quality, radiation dose, and diagnostic accuracy of dual-energy CT angiography (CTA) compared with 3D rotational digital subtraction angiography (DSA) in the detection of intracranial aneurysms. SUBJECTS AND METHODS: Forty-six patients with clinically suspected intracranial aneurysms underwent dual-source dual-energy CTA and 3D DSA. For the analysis of the image quality and radiation dose of dual-energy CTA, 46 patients who underwent digital subtraction CTA were recruited as a control group. The image quality of dual-energy CTA and digital subtraction CTA was rated on a 4-point scale as excellent, good, moderate, or poor. The radiation dose of CTA was recorded according to patient protocol. Aneurysm detection with dual-energy CTA compared with 3D DSA was analyzed on a per-patient and on a peraneurysm basis. Sensitivity, specificity, and positive and negative predictive values for aneurysm presence were determined. The mean maximum diameter and dome and neck dimensions of aneurysms were measured on dual-energy CTA and 3D DSA images. Correlation analysis between the two techniques was performed. RESULTS: There was no statistical difference between the image quality of dual-energy CTA and that of digital subtraction CTA (p>0.05). Patients undergoing dual-energy CTA received a smaller radiation dose (volume CT dose index, 20.6+/-0.1 mGy [mean+/-SD]; dose-length product, 398.6+/-19.0 mGy x cm) than those undergoing digital subtraction CTA (volume CT dose index, 50.4+/-3.4 mGy; dose-length product, 1,095.6+/-114.2 mGyxcm) (p<0.05). Three-dimensional DSA showed no aneurysm in 11 patients and 40 aneurysms in 35 patients. The mean maximum diameter of the aneurysms was 6+/-3 mm; the dome measurement, 5+/-3 mm; and the neck dimension, 3+/-2 mm. With dual-energy CTA, 38 aneurysms in 34 patients were correctly detected, and two aneurysms in two patients were missed. With DSA as the standard of reference, the sensitivity, specificity, and positive and negative predictive values of dual-energy CTA in the detection of intracranial aneurysm were 97.1%, 100%, 100%, and 91.7% on a per-patient basis and 95.0%, 100%, 100%, and 99.7% on a per-aneurysm basis. Dual-energy CTA had sensitivities of 93.8%, 100%, and 80.0% and specificities of 100%, 100%, and 100% in the detection of aneurysms larger than 5 mm, those measuring 3.1-5 mm, and aneurysms 3 mm or smaller. At dual-energy CTA, the mean maximum diameter and dome and neck dimensions were 6+/-3 mm, 5+/-3 mm, and 3+/-2 mm. Excellent correlation was found between DSA and dual-energy CTA findings with respect to mean maximum diameter and dome and neck dimensions (r=0.969, 0.957, and 0.870; p = 0.000). CONCLUSION: On the basis of the findings in the small series of patients evaluated, contrast-enhanced dual-energy CTA had diagnostic image quality at a lower radiation dose than digital subtraction CTA and high diagnostic accuracy compared with 3D DSA in the detection of intracranial aneurysms.

Automatic bone removal dual-energy CT angiography for the evaluation of intracranial aneurysms.

PURPOSE: To evaluate the diagnostic accuracy of dual-energy computed tomographic angiography (DE-CTA) in the detection of intracranial aneurysms and to determine whether DE-CTA provides adequate information to guide treatment choice. MATERIALS AND METHODS: Eighty patients (31 men and 49 women; mean [SD] ages of 52 [9] years) with spontaneous subarachnoid hemorrhage underwent DE-CTA. The performance of DE-CTA was compared with conventional CTA created from average weighted images and digital subtraction angiography (DSA). Sensitivity and specificity for aneurysm detection were determined on a per-patient and per-aneurysm basis. The treatment choice was assessed on the basis of aneurysm neck size and/or the dome/neck ratio. RESULTS: With DSA as reference standard (n = 61; 47 aneurysms in 41 patients), DE-CTA correctly detected 45 aneurysms in 41 patients corresponding to sensitivity and specificity of 100% and 95.0% on a per-patient basis versus 95.7% and 95.0% on a per-aneurysm basis, whereas conventional CTA correctly detected 43 aneurysms in 39 patients corresponding to sensitivity and specificity of 95.1% and 95.0% on a per-patient basis versus 91.5% and 95.0% on a per-aneurysm basis. No statistical difference between DE-CTA and conventional CTA was found for the diagnostic evaluation of intracranial aneurysms. Surgery was performed to treat 38 aneurysms, coiling in 26 aneurysms, stent in one patient, and follow-up in the remaining 5 aneurysms. Dual-energy CTA correctly predicted treatment choice in 44 aneurysms, with 15 aneurysms coiled and 29 aneurysms clipped. CONCLUSIONS: Compared with DSA, DE-CTA had a comparable diagnostic accuracy for the detection of intracranial aneurysms, visualization of the morphology of aneurysms at the skull base, and prediction of aneurysm treatment choice in most patients with spontaneous subarachnoid hemorrhage based on this study.

Sinogram-Affirmed Iterative Reconstruction Negatively Impacts the Risk Category Based on Agatston Score: A Study Combining Coronary Calcium Score Measurement and Coronary CT Angiography.

PURPOSE: To assess the impact of sinogram-affirmed iterative reconstruction (SAFIRE) on risk category for coronary artery disease by combining coronary calcium score measurement and coronary CT angiography (CCTA). MATERIALS AND METHODS: Eighty-nine patients (64.0% male) older than 18 years (64.4 ± 10.3 years) underwent coronary artery calcium scanning and prospectively ECG-triggered sequential CCTA examination. All raw data acquired in coronary artery calcium scanning were reconstructed by both filtered back projection (FBP) and SAFIRE algorithms with 5 different levels. Objective image quality and calcium quantification were evaluated and compared between FBP and all SAFIRE levels by the Sphericity Assumed test or Greenhouse-Geisser ε correction coefficient. Coronary artery stenosis was assessed in CCTA. Risk categories of all patients and of the patients with coronary artery stenosis in CCTA were compared between FBP and all SAFIRE levels by the Friedman test. RESULTS: The reconstruction protocol from traditional FBP to SAFIRE 5 was associated with a gradual reduction in CT value and image noise (P < 0.001) but associated with a gradual improvement in the signal-to-noise ratio (P < 0.001). There was a gradual reduction in coronary calcification quantification (Agatston score: from 73.5 in FBP to 38.1 in SAFIRE 5, P < 0.001) from traditional FBP to SAFIRE 5. There was a significant difference for the risk category between FBP and all levels of SAFIRE in all patients (from 3.5 in FBP to 3.2 in SAFIRE 5, P < 0.001) and in the patients with coronary artery stenosis in CCTA (from 4.0 in FBP to 3.6 in SAFIRE 5, P < 0.001). CONCLUSIONS: SAFIRE significantly reduces coronary calcification quantification compared to FBP, resulting in the reduction of risk categories based on the Agatston score. The risk categories of the patients with coronary artery stenosis in CCTA may also decline. Thus, SAFIRE may lead risk categories to underestimate the existence of significant coronary artery stenosis.

Pulmonary embolism detection with dual-energy CT: experimental study of dual-source CT in rabbits.

PURPOSE: To evaluate feasibility and added value of dual-energy computed tomography (CT) in diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: This institutional animal experimental committee-approved study was performed in accordance with animal care guidelines. Eight New Zealand rabbits underwent standard unenhanced and contrast material-enhanced dual-source CT. Gelatin sponge particles were injected into the pulmonary artery, and rabbits underwent contrast-enhanced dual-source CT pulmonary angiography, from which blood-flow (BF) and fusion images were created. Immediately after dual-source CT, rabbits were sacrificed, their lungs were removed and fixed in 10% formalin, and detailed pathologic determination of location and number of lung lobes with PE was performed. Two rabbits were excluded: One died during the procedure. In the other, the catheter tip was retained in the left inferior pulmonary artery. This caused marked postembolization CT image artifacts in adjacent regions. Six rabbits were included in final analysis. Two radiologists without knowledge of pathologic results evaluated five pulmonary lobes in each rabbit and recorded whether PE was present. Pathologic results served as the reference standard. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the techniques were calculated. Weighted kappa values were calculated to evaluate agreement between modalities. RESULTS: Pathologic analysis revealed PE in 18 of 30 pulmonary lobes. Conventional CT angiography was used to correctly identify PE in 12 lobes and absence of emboli in 18 lobes, which corresponded to sensitivity, specificity, PPV, and NPV of 67%, 100%, 100%, and 67%, respectively. A kappa value of 0.65 indicated good correlation with pathologic findings. On BF images, segments with an embolic region showed low perfusion compared with segments with a normal pulmonary region. BF images and fused images correctly showed PE in 16 of 18 pulmonary lobes and absence of emboli in 11 of 12 lobes, which corresponded to sensitivity, specificity, PPV, and NPV of 89%, 92%, 94%, and 85%, respectively, in detection of PE. A kappa value of 0.80 indicated good correlation with pathologic findings. CONCLUSION: Dual-source CT can depict normal and abnormal blood perfusion distribution in a rabbit's lung. Abnormal pulmonary blood distribution, as shown at dual-source CT, improves detection of acute PE in rabbits.

Detection of pulmonary embolism by dual energy CT: correlation with perfusion scintigraphy and histopathological findings in rabbits.

The purpose of the study was to compare the ability of dual energy CT (DECT) and perfusion scintigraphy (PS) to detect pulmonary embolism (PE) in a rabbit model. Gelfoam (n = 20) or saline (n = 4) was injected into the femoral vein of rabbits. After 2 h, DECT pulmonary angiography (CTPA) was used to create blood flow imaging (BFI) and fusion images. The rabbits then underwent PS. Pathological determination of locations and numbers of lung lobes with PE was recorded. The sensitivity and specificity for BFI, CTPA, fused images and PS were calculated using the pathological results as reference standards. Compared with pathological evaluation, CTPA correctly identified PE in 40 lobes and absence of emboli in 80 lobes, corresponding to a sensitivity and specificity of 100%. BFI and fused images correctly identified PE in 40 lobes and the absence of emboli in 78 lobes, corresponding to a sensitivity and specificity of 100% and 98%, respectively. PS correctly detected 27 lobes with PE and 65 lobes without PE, corresponding to a sensitivity and specificity of 68% and 81%, respectively. BFI, CTPA and fused images derived from a single contrast-enhanced DECT provide a higher diagnostic accuracy of detecting PE than PS in a rabbit model.

Detection of pulmonary embolism using dual-energy computed tomography and correlation with cardiovascular measurements: a preliminary study.

BACKGROUND: Detection of a suspected pulmonary embolism (PE) has been the focus of considerable research over the past few decades. Recently developed dual-source computed tomography (DSCT) scanners with dual-energy mode have been used to detect PE, but the studies on this topic are few. PURPOSE: To assess the clinical value of dual-source, dual-energy CT (DECT) for the diagnosis of suspected PE and to correlate with cardiovascular measurements. MATERIAL AND METHODS: 31 patients with suspected PE underwent contrast-enhanced DSCT scanning with dual-energy mode. Dedicated software for lung perfusion blood volume (PBV) was used in postprocessing. The numbers and locations of PE in PBV images and CT pulmonary angiography (CTPA) were recorded. Sensitivity and specificity were measured, comparing to CTPA as a standard of reference. The relationship between range of iodine mapping abnormality in PBV images and cardiovascular measurements was analyzed. RESULTS: 33 DECT scans were performed in 31 patients. Seventeen patients had PE, while 14 patients had negative results. Filling defects were detected in pulmonary arteries in 44 pulmonary lobar and 99 segmental arteries. Compared to CTPA as a standard of reference, sensitivity and specificity of PBV images were 93.8% and 93.3% on a per-patient basis, 93.2% and 94.7% on a per-lobe basis, and 76.1% and 97.6% on a per-segment basis, respectively. Spearman correlation test showed good positive correlation between the right ventricle (RV)/left ventricle (LV) diameter ratio and pulmonary lobes with emboli for PBV images (R=0.663; P=0.004). CONCLUSION: DECT can provide morphological and functional information of the whole lung in a single contrast-enhanced acquisition; the perfusion defects visualized in PBV images appear to have a positive relationship with the patients' right heart dysfunction.

Functional Evaluation of Transplanted Kidneys with Reduced Field-of-View Diffusion-Weighted Imaging at 3T.

Objective: To determine the feasibility of reduced field-of-view diffusion-weighted imaging (rFOV DWI) with multi-b values to detect functional variability in transplanted kidneys. Materials and Methods: Using a 3T MRI scanner, multi-b rFOV DWI of transplanted kidney or native kidney was performed in 40 renal transplantation recipients and 18 healthy volunteers. The patients were stratified, according to an estimated glomerular filtration rate (eGFR): Group 1, eGFR ≥ 60 mL/min/1.73 m2; Group 2, eGFR ≥ 30 mL/min/1.73 m2 and < 60 mL/min/1.73 m2; Group 3, eGFR < 30 mL/min/1.73 m2. Total apparent diffusion coefficient (ADCT), perfusion-free ADC (ADCD) and perfusion fraction (FP) of kidneys were calculated and compared among the four groups. Correlations between the imaging results and eGFR were assessed. Results: All volunteers had eGFR ≥ 60 mL/min/1.73 m2, while 16, 16, and 8 patients were included in Groups 1, 2, and 3, respectively. In the renal cortex, ADCT was higher in Group 1 ([1.65 ± 0.13] × 10-3 mm2/s) than Group 3 ([1.44 ± 0.11] × 10-3 mm2/s) (p < 0.05), and the inter-group differences of FP values were significant (all p < 0.05) (0.330 ± 0.024, 0.309 ± 0.019, 0.278 ± 0.033, and 0.250 ± 0.028 for control group, Groups 1, 2, and 3, respectively). Renal cortical ADCT, ADCD, FP, and renal medullary ADCT and FP correlated positively with eGFR (r = 0.596, 0.403, 0.711, 0.341, and 0.323, respectively; all p < 0.05). When using 0.278 as the cutoff value, renal cortical FP had a sensitivity of 97.1% and a specificity of 66.7% for predicting decreased renal function. Conclusion: Multi-b rFOV DWI presents transplanted kidneys with high resolution, which is a promising functional tool for non-invasively monitoring function of transplanted kidneys.

Prospectively ECG-triggered high-pitch coronary CT angiography at 70 kVp with 30mL contrast agent: An intraindividual comparison with sequential scanning at 120 kVp with 60mL contrast agent.

PURPOSE: To investigate image quality, radiation dose, and diagnostic efficiency of prospectively ECG-triggered high-pitch coronary CT angiography (CCTA) at 70 kVp with 30mL contrast agent intra-individually compared with routine CCTA protocol. MATERIALS AND METHODS: One hundred and thirty eight patients with suspected coronary artery disease, body mass index (BMI)≤25kg/m2 and heart rate (HR)≤70 beats per minute (bpm) underwent prospectively ECG-triggered high-pitch CCTA at 70 kVp and 30mL contrast agent (protocol A) and prospectively ECG-triggered sequential scanning at 120 kVp and 60mL contrast medium (protocol B). Objective and subjective image quality, radiation doses, and diagnostic accuracy were evaluated and compared between the two protocols. RESULTS: Higher CT attenuation, higher noise, lower signal-to-noise ratios (SNRs) and lower contrast-to-noise ratios (CNRs) were found in protocol A than in protocol B (P<0.001). However, image quality of protocol A were diagnostic. In patients with BMI<23kg/m2 or HR<60bpm, subjective image quality scores of some coronary arteries in protocol A were not significantly different from protocol B (P>0.05). Effective dose in protocol A has reduced by 96.7% compared with protocol B (P<0.001). No significant differences were found for diagnostic accuracy between the two protocols on a per-segment (P=0.513), per-vessel (P=0.317) and per-patient (P=0.125) basis. CONCLUSIONS: Prospectively ECG-triggered high-pitch CCTA at 70kVp with 30mL contrast agent can reduce radiation dose but maintain image quality and high diagnostic accuracy in a selected, non-obese population.