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.

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.

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.

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.

Contrast-enhanced ultrasound for differentiating benign from malignant solid small renal masses: comparison with contrast-enhanced CT.

PURPOSE: The study aimed to compare the diagnostic efficiency of contrast-enhanced ultrasound (CEUS) with that of contrast-enhanced computed tomography (CECT) in the evaluation of benign and malignant small renal masses (SRMs) (<4 cm) confirmed by pathology. METHODS: A total of 118 patients with 118 renal masses smaller than 4 cm diagnosed by both CEUS and CECT were enrolled in this study, including 25 benign lesions and 93 malignant lesions. All lesions were confirmed by histopathologic diagnosis after surgical resection. The diagnostic imaging studies of the patients were retrospectively reviewed by two independent ultrasonologists and two independent radiologists blinded to the CT or ultrasound findings and final histological results. All lesions on both CEUS and CECT were independently scored on a 3-point scale (1: benign, 2: equivocal, and 3: malignant). The concordance between interobserver agreement was interpreted using a weighted kappa statistic. The diagnostic efficiency of the evaluation of benign and malignant lesions was compared between CEUS and CECT. RESULTS: All the 118 included lesions were detected by both CEUS and CECT. In CEUS and CECT imaging evaluation of the 118 lesions, the weighted kappa value interpreting the concordance between interobserver agreement was 0.89 (95% CI 0.79-0.98) and 0.93 (95% CI 0.87-0.99), respectively. Both CEUS and CECT demonstrated good diagnostic performance in differential diagnosis of benign and malignant SRMs with sensitivity of 93.5% and 89.2%, specificity of 68% and 76%, PPV of 91.6% and 93.3%, NPV of 73.9% and 65.5%, and AUC of 0.808 and 0.826, respectively. There was no statistically significant difference in any of the diagnostic performance indices between these two methods (P > 0.05). However, the qualitative diagnosis of small papillary renal cell carcinoma (RCC) by CEUS was significantly better than that by CECT (P < 0.05), while there was no significant difference in qualitative diagnostic accuracy on other histotypes of SRMs between CEUS and CECT (P > 0.05). CONCLUSIONS: Both CEUS and CECT imaging modalities are effective for the differential diagnosis of benign and malignant SRMs. Furthermore, CEUS may be more effective than CECT for the qualitative diagnosis of small papillary RCC.

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.

Radiation Optimized Dual-source Dual-energy Computed Tomography Pulmonary Angiography: Intra-individual and Inter-individual Comparison.

OBJECTIVES: This study aimed to intra-individually and inter-individually compare image quality, radiation dose, and diagnostic accuracy of dual-source dual-energy computed tomography pulmonary angiography (CTPA) protocols in patients with suspected pulmonary embolism (PE). METHODS: Thirty-three patients with suspected PE underwent initial and follow-up dual-energy CTPA at 80/Sn140 kVp (group A) or 100/Sn140 kVp (group B), which were assigned based on tube voltages. Subjective and objective CTPA image quality and lung perfusion map image quality were evaluated. Diagnostic accuracies of CTPA and perfusion maps were assessed by two radiologists independently. Effective dose (ED) was calculated and compared. RESULTS: Mean computed tomography (CT) values of pulmonary arteries were higher in group A than group B (P = .006). There was no difference in signal-to-noise ratio and contrast-to-noise ratio between the two groups (both P > .05). Interobserver agreement for evaluating subjective image quality of CTPA and color-coded perfusion images was either good (κ = 0.784) or excellent (κ = 0.887). Perfusion defect scores and diagnostic accuracy of CTPA showed no difference between both groups (both P > .05). Effective dose of group A was reduced by 45.8% compared to group B (P < .001). CONCLUSIONS: Second-generation dual-source dual-energy CTPA with 80/Sn140 kVp allows for sufficient image quality and diagnostic accuracy for detecting PE while substantially reducing radiation dose.

Single Phase Dual-energy CT Angiography: One-stop-shop Tool for Evaluating Aneurysmal Subarachnoid Hemorrhage.

Aneurysmal subarachnoid hemorrhages have extremely high case fatality in clinic. Early and rapid identifications of ruptured intracranial aneurysms seem to be especially important. Here we evaluate clinical value of single phase contrast-enhanced dual-energy CT angiograph (DE-CTA) as a one-stop-shop tool in detecting aneurysmal subarachnoid hemorrhage. One hundred and five patients who underwent true non-enhanced CT (TNCT), contrast-enhanced DE-CTA and digital subtraction angiography (DSA) were included. Image quality and detectability of intracranial hemorrhage were evaluated and compared between virtual non-enhanced CT (VNCT) images reconstructed from DE-CTA and TNCT. There was no statistical difference in image quality (P > 0.05) between VNCT and TNCT. The agreement of VNCT and TNCT in detecting intracranial hemorrhage reached 98.1% on a per-patient basis. With DSA as reference standard, sensitivity and specificity on a per-patient were 98.3% and 97.9% for DE-CTA in intracranial aneurysm detection. Effective dose of DE-CTA was reduced by 75.0% compared to conventional digital subtraction CTA. Thus, single phase contrast-enhanced DE-CTA is optimal reliable one-stop-shop tool for detecting intracranial hemorrhage with VNCT and intracranial aneurysms with DE-CTA with substantial radiation dose reduction compared with conventional digital subtraction CTA.

Chronic thromboembolic pulmonary hypertension: Comparison of dual-energy computed tomography and single photon emission computed tomography in canines.

PURPOSE: To compare diagnostic accuracy between dual-energy CT lung perfused blood volume (Lung PBV) imaging and single photon emission computed tomography (SPECT) in detecting chronic thromboembolic pulmonary hypertension (CTEPH) with histopathological results as reference standard in a canine model. MATERIALS AND METHODS: Eighteen CTEPH canines were included into this experimental study. All procedures including paracentesis, embolization, scanning, pressure measurement and feeding medicine were repeated each two weeks, until systolic/diastolic pressure in canines was ≥ 30/15 mm Hg or mean pulmonary artery pressure ≥ 20 mm Hg, and then sacrificed for histopathology examination. Two radiologists (readers 1 and 2) and two nuclear radiologists (readers 3 and 4) analyzed images of conventional CT pulmonary angiography in dual-energy CT mode, Lung PBV imaging and SPECT, respectively. The presence, numbers, and locations of pulmonary emboli (PE) were recorded on a per-lobe basis. Pathological examination was served as reference standard. Sensitivity, specificity and accuracy of Lung PBV and SPECT were calculated. Kappa statistics were used to quantify inter-reader agreement. RESULTS: With histopathological results as reference standard, the sensitivities of 72.2%, 78.8%, 81.2%, specificities of 75.9%, 87.5%, 84.8%, accuracies of 73.8%, 83.1%, 83.1%, for readers 1, 2 and both with Lung PBV, respectively. Readers 3, 4 and both had sensitivities of 14.3%, 25.7%, 33.3%, specificities of 90.0%, 86.7%, 93.3%, accuracies of 49.2%, 53.8%, 60.0% with SPECT for detecting CTEPH. Inter-reader agreements were good for dual-energy CT (kappa=0.662) and SPECT (k=0.706) for detecting CTEPH. CONCLUSION: Dual-energy CT had a higher accuracy to detect CTEPH than SPECT in this canine model study.

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.

Seventy-Peak Kilovoltage High-Pitch Thoracic Aortic CT Angiography without ECG Gating: Evaluation of Image Quality and Radiation Dose.

RATIONALE AND OBJECTIVES: To assess the feasibility of 70-kVp high-pitch non-ECG-gated thoracic aortic computed tomography angiography (CTA) with 40-mL contrast agent compared to 100-kVp standard-pitch CTA with 60-mL contrast agent. MATERIALS AND METHODS: Sixty-seven patients (51 men and 16 women; mean age, 55 ± 14 years) received non-ECG-gated aortic CTA at 70 kVp, high pitch of 3.4, and 40-mL contrast agent (group A, n = 31) or CTA at 100-kVp, pitch of 1.2, and 60-mL contrast agent (group B, n = 36). Iterative reconstruction was used in all patients. For image quality assessment, CTA images were evaluated on a three-point scale and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared. Furthermore, computed tomography (CT) dose index was recorded. RESULTS: Mean CT values and noise levels were higher in group A compared to group B (all P < .001), whereas SNR and CNR were lower than those in group B (all P < .001). Furthermore, the image quality of the aorta at the level of the diaphragm was lower in group A than that in group B (P < .05). However, image quality was graded as diagnostic in all patients, and motion artifacts of the aortic arch were significantly decreased in group A (P <.05). Interreader agreement was good or excellent for image quality assessment (k = 0.625-0.835). The 70-kVp CTA protocol, which allows dose reduction of 85%, was considered diagnostic in all instances by two readers. CONCLUSIONS: Our proposed thoracic aortic CTA protocol provides diagnostic information with substantial reduction of both radiation and contrast agent doses compared to standard-pitch CTA at 100 kVp.

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.

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.

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.

Image quality and radiation dose of lower extremity CT angiography using 70 kVp, high pitch acquisition and sinogram-affirmed iterative reconstruction.

OBJECTIVES: The purpose of this study was to assess image quality and radiation dose of lower extremity CT angiography (CTA) with 70 kVp, high pitch acquisition and sinogram-affirmed iterative reconstruction (SAFIRE). METHODS: Lower extremity CTAs were performed on 44 patients: 22 patients were examined using protocol A (120 kVp, pitch of 0.85 and 120 ml of contrast agent on a first-generation dual-source CT) (120 kVp group) and 22 patients were evaluated with protocol B (70 kVp, pitch of 2.2 and 80 ml of contrast agent on a second-generation dual-source CT) (70 kVp group). Images from the 120 kVp group were reconstructed with filtered back projection (FBP) and images from the 70 kVp group with SAFIRE. The attenuation, image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Two radiologists subjectively assessed image quality of lower extremity arteries, plantar arterial enhancement and venous contamination of all patients. Radiation dose was compared between the two groups. RESULTS: Higher mean intravascular attenuation was obtained in the 70 kVp group (70 vs. 120 kVp group, 555.4 ± 83.4 HU vs. 300.9 ± 81.4 HU, P<0.001), as well as image noise (20.0 ± 2.8 HU vs. 17.5 ± 3.2 HU, P = 0.010), SNR (32.0 ± 7.0 vs. 19.1 ± 6.9, P<0.001) and CNR (28.1 ± 6.6 vs 15.9 ± 6.3, P<0.001). No difference in subjective image quality and plantar arterial enhancement was found between 120 kVp group and 70 kVp group (all P>0.05). The venous contamination score was 1.5 ± 0.8 for 120 kVp group while no venous contamination was found in 70 kVp group. The inter-observer agreement was moderate to good for both groups (0.515∼1, P<0.001). The effective dose was lower in 70 kVp group (0.3 ± 0.1 mSv) than in 120 kVp group (1.6 ± 0.7 mSv)(P<0.001). CONCLUSIONS: Lower extremity CTA using 70 kVp, high pitch acquisition and SAFIRE, except increasing imaging noise, allows for lower radiation dose and contrast material volume without compromising image quality.

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.

Diagnostic accuracy of three-dimensional contrast-enhanced MR angiography at 3-T for acute pulmonary embolism detection: comparison with multidetector CT angiography.

BACKGROUND: Three-dimensional contrast-enhanced MR pulmonary angiography (MRPA) is a suitable option for pulmonary embolism (PE) detection. However, there have been few reports on the diagnostic accuracy of MRPA for PE detection in a 3-T MR system. The purpose of this study was to evaluate the accuracy of MRPA in a 3-T MR system to detect acute PE with multidetector CT pulmonary angiography (CTPA) as reference standard. METHODS: Twenty-seven patients (18 males and 9 females, mean age 38.9±14.4 years) underwent both MRPA and CTPA within 3 days (range, 0-3 days) for evaluating PE. Pulmonary emboli in MRPA were independently analyzed on a per-patient and per-lobe basis by two radiologists. CTPA was regarded as reference standard, which was evaluated by another two radiologists in consensus. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for PE detection were calculated. Weighted κ values were calculated to evaluate agreement between readers. RESULTS: Twenty-four patients had PE in 55 lung lobes in CTPA, while 3 patients had no PE detected. Readers 1 and 2 correctly detected 47 and 46 lung lobes having clots in 24 and 23 patients, corresponding to sensitivities, specificities, PPV, NPV, and accuracies of 100%, 100%, 100%, 100%, 100%; 100%, 66.7%, 96.0%, 100%, 96.4% on a per-patient basis and 85.5%, 100%, 100%, 90.9%, 94.1%; 83.6%, 93.7%, 90.2%, 89.2%, 89.6% on a per-lobe basis; respectively. Excellent inter-reader agreement (κ values=1.00 and 0.934; both P<0.001) were found for detecting PE on a per-patient and per-lobe analysis. CONCLUSION: Three-dimensional contrast-enhanced MRPA with a 3-T MR system is a suitable alternative modality to CTPA to detect PE on a per-patient basis based on this small cohort study.

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.