Volumetric assessment of solid pulmonary nodules on ultralow-dose CT: a phantom study.

BACKGROUND: To reduce the radiation exposure from chest computed tomography (CT), ultralow-dose CT (ULDCT) protocols performed at sub-millisievert levels were previously tested for the evaluation of pulmonary nodules (PNs). The purpose of our study was to investigate the effect of ULDCT and iterative image reconstruction on volumetric measurements of solid PNs. METHODS: CT datasets of an anthropomorphic chest phantom containing solid microspheres were obtained with a third-generation dual-source CT at standard dose, 1/8th, 1/20th and 1/70th of standard dose [CT volume dose index (CTDIvol): 0.03-2.03 mGy]. Semi-automated volumetric measurements were performed on CT datasets reconstructed with filtered back projection (FBP) and advanced modelled iterative reconstruction (ADMIRE), at strength level 3 and 5. Absolute percentage error (APE) evaluated measurement accuracy related to the effective volume. Scan repetition differences were evaluated using Bland-Altman analysis. Two-way analysis of variance (ANOVA) assessed influence of different scan parameters on APE. Proportional differences (PDs) tested the effect of dose settings and reconstruction algorithms on volumetric measurements, as compared to the standard protocol (standard dose-FBP). RESULTS: Bland-Altman analysis revealed small mean interscan differences of APE with narrow limits of agreement (-0.1%±4.3% to -0.3%±3.8%). Dose settings (P<0.001), reconstruction algorithms (P<0.001), nodule diameters (P<0.001) and nodule density (P=0.011) had statistically significant influence on APE. Post-hoc Bonferroni tests showed slightly higher APE when scanning with 1/70th of standard dose [mean difference: 3.4%, 95% confidence interval (CI): 2.5-4.3%; P<0.001], and for image reconstruction with ADMIRE5 (mean difference: 1.8%, 95% CI: 1.0-2.5%; P<0.001). No significant differences for scanning with 1/20th of standard dose (P=0.42), and image reconstruction with ADMIRE3 (P=0.19) were found. Scanning with 1/70th of standard dose and image reconstruction with FBP showed the widest range of PDs (-16.8% to 23.4%) compared to standard dose-FBP. CONCLUSIONS: Our phantom study showed no significant difference between nodule volume measurements on standard dose CT (CTDIvol: 2 mGy) and ULDCT with 1/20th of standard dose (CTDIvol: 0.10 mGy).

Chest pain CT in the emergency department: Watch out for the myocardium.

RATIONALE AND OBJECTIVES: To evaluate the frequency and relevance of hypodense myocardium (HM) encountered in patients undergoing chest-pain CT in the emergency department (ED). MATERIAL AND METHODS: In this IRB-approved retrospective study, ECG-gated chest-pain CT examinations of 300 consecutive patients (mean age 60 ± 17 years) presenting with acute chest-pain to our ED were evaluated. Once ST-segment elevation infarction was excluded, chest-pain CT including the coronary arteries (rule-out acute coronary syndrome (ACS), pulmonary embolism (PE) and acute aortic syndrome (AAS): chest-pain CTcoronary, n = 121) or not including the coronary arteries was performed (rule-out PE and AAS: chest-pain CTw/o coronary, n = 179). Each myocardial segment was assessed for the presence of HM; attenuation was measured and compared to normal myocardium. RESULTS: HM was identified in 27/300 patients (9%): 12/179 in chest-pain CTw/o coronary (7%) and 15/121 in chest-pain CTcoronary (12%). Mean attenuation of HM (40 ± 17 HU) was significantly lower than that of healthy myocardium (103 ± 18 HU, p < 0.001), with a mean difference of 61 ± 19 HU. In 15/27 patients (55.6%) with HM, the final diagnosis was acute MI, and in the remaining 12/27 patients (44.4%) previous MI was found in the patients' history. Chest-pain CTw/o coronary identified HM in 10/15 patients (66.6%) with a final diagnosis of acute MI. CONCLUSION: HM indicating acute MI are often encountered in chest pain CT in the ED, also in chest-pain CTw/o coronary when MI is not suspected. This indicates that the myocardium should always be analyzed for hypodense regions even when MI not suspected.

Diagnostic accuracy and added value of dual-energy subtraction radiography compared to standard conventional radiography using computed tomography as standard of reference.

PURPOSE: To retrospectively evaluate diagnostic performance of dual-energy subtraction radiography (DESR) for interpretation of chest radiographs compared to conventional radiography (CR) using computed tomography (CT) as standard of reference. MATERIAL AND METHODS: A total of 199 patients (75 female, median age 67) were included in this institutional review board (IRB)-approved clinical trial. All patients were scanned in posteroanterior and lateral direction with dual-shot DE-technique. Chest CT was performed within ±72 hours. The system provides three types of images: bone weighted-image, soft tissue weighted-image, herein termed as DESR-images, and a standard image, termed CR-image (marked as CR-image). Images were evaluated by two radiologists for presence of inserted life support lines, pneumothorax, pleural effusion, infectious consolidation, interstitial lung changes, tumor, skeletal alterations, soft tissue alterations, aortic or tracheal calcification and pleural thickening. Inter-observer agreement between readers and diagnostic performance were calculated. McNemar's test was used to test for significant differences. RESULTS: Mean inter-observer agreement throughout the investigated parameters was higher in DESR images compared to CR-images (kDESR = 0.935 vs. kCR = 0.858). DESR images provided significantly increased sensitivity compared to CR-images for the detection of infectious consolidations (42% vs. 62%), tumor (46% vs. 57%), interstitial lung changes (69% vs. 87%) and aortic or tracheal calcification (25 vs. 73%) (p<0.05). There were no significant differences in sensitivity for the detection of inserted life support lines, pneumothorax, pleural effusion, skeletal alterations, soft tissue alterations or pleural thickening (p>0.05). CONCLUSION: DESR increases significantly the sensibility without affecting the specificity evaluating chest radiographs, with emphasis on the detection of interstitial lung diseases.

Dose-Optimized Computed Tomography for Screening and Follow-Up of Solid Pulmonary Nodules in Obesity: A Phantom Study.

To determine the lowest CT radiation dose-level at maintained image-quality and high sensitivity for detection of pulmonary-nodules in obesity. Single-energy CT with tin-filtration was performed in a chest-phantom with solid pulmonary-nodules simulating over-weight and obesity. CTDIvol of the standard-protocol was 0.41 mGy, subsequent scans were obtained at 1/2 and 1/4 dose-levels. Images were reconstructed using FBP and advanced-modeled iterative reconstruction (ADMIRE). Noise, image-quality, and sensitivity for nodule-detection were assessed. Noise was significantly reduced with ADMIRE (standard-dose: 73%; 1/2 dose: 73%; 1/4 dose: 71.2%; p < 0.001) compared to FBP. Image-quality was diagnostic for all images reconstructed with ADMIRE5. Sensitivity for nodule-detection was 100% at 1/2 and 1/4 dose-level for the phantom simulating over-weight and 97.37% (1/2 dose-level) and 81.58% (1/4 dose-level) for the phantom simulating obesity using ADMIRE5. In conclusion, single-energy CT with tin-filtration and ADMIRE shows potential for dose reduction in a phantom experiment down to 0.1 mGy in over-weight and 0.21 mGy obese subjects, while image quality and sensitivity for detection of solid pulmonary nodules remains high.

Diagnostic Value of Bronchoalveolar Lavage for Diagnosis of Suspected Peripheral Lung Cancer.

BACKGROUND: There is a paucity of data concerning the benefit of bronchoalveolar lavage (BAL) for the diagnosis of suspected peripheral lung cancer (PLC). The aim of this study was to investigate the diagnostic value of BAL for the diagnosis of suspected PLC. PATIENTS AND METHODS: All flexible bronchoscopies that included BAL among other modalities (brush, forceps, washing) for the diagnosis of a suspected PLC performed between 2009 and 2013 were analyzed in this retrospective study. RESULTS: A total of 260 patients were included. Malignancy was present in 61%. BAL's sensitivity for the diagnosis of malignancy was 29%, and overall diagnostic yield of BAL was 46%. However, only 1% of cancer diagnoses would have been missed in the absence of BAL. In the multivariable analysis, the size of lesion (odds ratio [OR], 1.17; 95% confidence interval [CI], 1.02-1.33; P = .023), the presence of bronchus sign (OR, 4.73; 95% CI, 1.06-21.08; P = .042), and the presence of mediastinal/hilar lymphadenopathy (OR, 3.37; 95% CI, 1.53-7.41; P = .002) were associated with improved BAL true-positive ratio relating to diagnosis of malignancy. However, the effect of lesion size on sensitivity was small (area under the curve, 0.31; 95% CI, 0.23-0.40; P < .001). Ground-glass lesions were not associated with improved BAL diagnostic value. The number needed to test for BAL for the diagnosis of malignancy or pulmonary infection was 37. CONCLUSION: Conventional BAL has a low diagnostic value for the diagnosis of suspected PLC, and the low number needed to test does not qualify BAL as a recommended routine investigation for the diagnosis of suspected PLC for either solid or ground-glass lesions.

Influence of Sinogram-Affirmed Iterative Reconstruction on Computed Tomography-Based Lung Volumetry and Quantification of Pulmonary Emphysema.

OBJECTIVE: The purpose of this study was to evaluate the influence of sinogram-affirmed iterative reconstruction (SAFIRE) on quantification of lung volume and pulmonary emphysema in low-dose chest computed tomography compared with filtered back projection (FBP). METHODS: Enhanced or nonenhanced low-dose chest computed tomography was performed in 20 patients with chronic obstructive pulmonary disease (group A) and in 20 patients without lung disease (group B). Data sets were reconstructed with FBP and SAFIRE strength levels 3 to 5. Two readers semiautomatically evaluated lung volumes and automatically quantified pulmonary emphysema, and another assessed image quality. Radiation dose parameters were recorded. RESULTS: Lung volume between FBP and SAFIRE 3 to 5 was not significantly different among both groups (all P > 0.05). When compared with those of FBP, total emphysema volume was significantly lower among reconstructions with SAFIRE 4 and 5 (mean difference, 0.56 and 0.79 L; all P < 0.001). There was no nondiagnostic image quality. CONCLUSIONS: Sinogram-affirmed iterative reconstruction does not alter lung volume measurements, although quantification of lung emphysema is affected at higher strength levels.

Ultralow-dose CT with tin filtration for detection of solid and sub solid pulmonary nodules: a phantom study.

OBJECTIVES: To investigate the diagnostic performance of advanced modelled iterative reconstruction (ADMIRE) to filtered back projection (FBP) when using an ultralow-dose protocol for the detection of solid and subsolid pulmonary nodules. METHODS: Single-energy CT was performed at 100 kVp with tin filtration in an anthropomorphic chest phantom with solid and subsolid pulmonary nodules (2-10 mm, attenuation, 20 to -800 HU at 120 kVp). The mean volume CT dose index (CTDIvol) of the standard chest protocol was 2.2 mGy. Subsequent scans were obtained at 1/8 (0.28 mGy), 1/20 (0.10 mGy) and 1/70 (0.03 mGy) dose levels by lowering tube voltage and tube current. Images were reconstructed with FBP and ADMIRE. One reader measured image noise; two readers determined image quality and assessed nodule localization. RESULTS: Image noise was significantly reduced using ADMIRE compared with FBP (ADMIRE at a strength level of 5 : 70.4% for 1/20; 71.6% for 1/8; p < 0.001). Interobserver agreement for image quality was excellent (k = 0.88). Image quality was considered diagnostic for all images at 1/20 dose using ADMIRE. Sensitivity of nodule detection was 97.1% (100% for solid, 93.8% for subsolid nodules) at 1/20 dose and 100% for both nodule entities at 1/8 dose using ADMIRE 5. Images obtained with 1/70 dose had moderate sensitivity (overall 85.7%; solid 95%; subsolid 73.3%). CONCLUSION: Our study suggests that with a combination of tin filtration and ADMIRE, the CTDIvol of chest CT can be lowered considerably, while sensitivity for nodule detection remains high. For solid nodules, CTDIvol was 0.10 mGy, while subsolid nodules required a slightly higher CTDIvol of 0.28 mGy. ADVANCES IN KNOWLEDGE: Detection of subsolid nodules is feasible with ultralow-dose protocols.

Screening for interstitial lung disease in systemic sclerosis: performance of high-resolution CT with limited number of slices: a prospective study.

OBJECTIVES: Early diagnosis of interstitial lung disease (ILD), currently the main cause of death in systemic sclerosis (SSc), is needed. The gold standard is high-resolution CT (HRCT) of the chest, but regular screening faces the risk of increased radiation exposure. We performed a prospective validation of a dedicated, 9-slice HRCT protocol with reduced radiation dose for the detection of ILD in patients with SSc. METHODS: We analysed 170/205 consecutive patients with SSc. Whole-chest HRCT, serving as standard of reference, and the reduced HRCT with nine slices allocated according to a basal-apical gradient were obtained. ILD presence, extent (> or <20%) and diagnostic confidence were assessed. The reduced HRCT was independently analysed by two blinded radiologists, who also evaluated image quality. Radiation dose parameters were calculated. RESULTS: Standard chest HRCT showed ILD in 77/170 patients. With the reduced HRCT, 68/77 cases with ILD were identified (sensitivity 88.3%, both readers). The accuracy (91.8%, reader 1; 94.7%, reader 2), diagnostic confidence (98.8%, reader 1; 95.3%, reader 2) and image quality rates were high. Minimal ILD was correctly quantified in 73.1% (reader 1)/71.2% (reader 2) and extensive ILD in 88% (reader 1)/100% (reader 2). Importantly, the reduced HRCT had a significantly lower radiation dose. The mean dose length product (effective dose) was only 5.66±4.46 mGycm (0.08±0.06 mSv) compared with the standard protocol dose of 149.00±95.90 mGycm (2.09±1.34 mSv). CONCLUSIONS: The above-described reduced chest HRCT protocol reliably detects even mild SSc-ILD in clinical practice, with the advantage of a much lower radiation dose compared with standard whole-chest HRCT.

Bicuspid aortic valves: diagnostic accuracy of standard axial 64-slice chest CT compared to aortic valve image plane ECG-gated cardiac CT.

OBJECTIVES: To assess the diagnostic accuracy of standard axial 64-slice chest CT compared to aortic valve image plane ECG-gated cardiac CT for bicuspid aortic valves. MATERIALS AND METHODS: The standard axial chest CT scans of 20 patients with known bicuspid aortic valves were blindly, randomly analyzed for (i) the appearance of the valve cusps, (ii) the largest aortic sinus area, (iii) the longest aortic cusp length, (iv) the thickest aortic valve cusp and (v) valve calcification. A second blinded reader independently analyzed the appearance of the valve cusps. Forty-two age- and sex-matched patients with known tricuspid aortic valves were used as controls. Retrospectively ECG-gated cardiac CT multiphase reconstructions of the aortic valve were used as the gold-standard. RESULTS: Fourteen (21%) scans were scored as unevaluable (7 bicuspid, 7 tricuspid). Of the remainder, there were 13 evaluable bicuspid valves, ten of which showed an aortic valve line sign, while the remaining three showed a normal Mercedes-Benz appearance owing to fused valve cusps. The 35 evaluable tricuspid aortic valves all showed a normal Mercedes-Benz appearance (P=0.001). Kappa analysis=0.62 indicating good interobserver agreement for the aortic valve cusp appearance. Aortic sinus areas, aortic cusp lengths and aortic cusp thicknesses of ≥ 3.8 cm(2), 3.2 cm and 1.6mm respectively on standard axial chest CT best distinguished bicuspid from tricuspid aortic valves (P<0.0001 for all). Of evaluable scans, the sensitivity, specificity, positive and negative predictive values of standard axial chest CT in diagnosing bicuspid aortic valves was 77% (CI 0.54-1.0), 100%, 100% and 70% respectively. CONCLUSION: The aortic valve is evaluable in approximately 80% of standard chest 64-slice CT scans. Bicuspid aortic valves may be diagnosed on evaluable scans with good diagnostic accuracy. An aortic valve line sign, enlarged aortic sinuses and elongated, thickened valve cusps are specific CT features.

Ultralow-dose chest computed tomography for pulmonary nodule detection: first performance evaluation of single energy scanning with spectral shaping.

PURPOSE: The purpose of this study was to evaluate the image quality and sensitivity of ultralow radiation dose single-energy computed tomography (CT) with tin filtration for spectral shaping and iterative reconstructions for the detection of pulmonary nodules in a phantom setting. METHODS: Single-energy CT was performed using third-generation dual-source CT (SOMATOM Force; 2 × 192 slices) at 70 kVp, 100 kVp with tin filtration (100Sn kVp), and 150Sn kV with tube current-time product adjustments resulting in standard dose (CT volume dose index, 3.1 mGy/effective dose, 1.3 mSv at a scan length of 30 cm), 1/10th dose level (0.3 mGy/0.13 mSv), and 1/20th dose level (0.15 mGy/0.06 mSv). An anthropomorphic chest phantom simulating an intermediate-sized adult with randomly distributed solid pulmonary nodules of various sizes (2-10 mm; attenuation, 75 HU at 120 kVp) was used. Images were reconstructed with advanced model-based iterative reconstruction (ADMIRE; strength levels 3 and 5) and were compared with those acquired with second-generation dual-source CT at 120 kVp (reconstructed with filtered back projection) and sinogram-affirmed iterative reconstruction (strength level 3) at the lowest possible dose at 120 kVp (CT volume dose index, 0.28 mGy). One blinded reader measured image noise, and 2 blinded, independent readers determined overall image quality on a 5-grade scale (1 = nondiagnostic to 5 = excellent) and marked nodule localization with confidence rates on a 5-grade scale (1 = unsure to 5 = high confidence). The constructional drawing of the phantom served as reference standard for calculation of sensitivity. Two patients were included, for proof of concept, who were scanned with the 100Sn kVp protocol at the 1/10th and 1/20th dose level. RESULTS: Image noise was highest in the images acquired with second-generation dual-source CT and reconstructed with filtered back projection. At both the 1/10th and 1/20th dose levels, image noise at a tube voltage of 100Sn kVp was significantly lower than in the 70 kVp and 150Sn kV data sets (ADMIRE 3, P < 0.01; ADMIRE 5, P < 0.05). Sensitivity of nodule detection was lowest in images acquired with second-generation dual-source CT at 120 kVp and the lowest possible dose. Protocols at 100Sn kVp and ADMIRE 5 showed highest sensitivity at the 1/10th and 1/20th dose levels. Highest numbers of false-positives occurred in second-generation dual-source CT images (range, 12-15), whereas lowest numbers occurred in the 1/10th and 1/20th dose data sets acquired with third-generation dual-source CT at 100Sn kVp and reconstructed with ADMIRE strength levels 3 and 5 (total of 1 and 0 false-positives, respectively). Diagnostic confidence at 100Sn kVp was significantly higher than at 70 kVp or 150Sn kV (ADMIRE 3, P < 0.05; ADMIRE 5, P < 0.01) at both the 1/10th and 1/20th dose levels. Images of the 2 patients scanned with 100Sn kVp at the 1/10th and 1/20th dose levels were of diagnostic quality. CONCLUSIONS: Our study suggests that chest CT for the detection of pulmonary nodules can be performed with third-generation dual-source CT producing high image quality, sensitivity, and diagnostic confidence at a very low effective radiation dose of 0.06 mSv when using a single-energy protocol at 100 kVp with spectral shaping and when using advanced iterative reconstruction techniques.

Diagnostic performance of a non-contrast-enhanced magnetic resonance imaging protocol for potential living related kidney donors.

RATIONALE AND OBJECTIVES: The objective of the study was to evaluate the performance of a non-contrast-enhanced magnetic resonance (MR) imaging protocol for preoperative screening of living related kidney donors. MATERIALS AND METHODS: Forty consecutive subjects (mean age 52.2 ± 11.3 years, range 29-73 years) underwent MR imaging with T2-weighted sequences (coronal and axial plane), with a non-contrast-enhanced respiratory-gated three-dimensional steady state free precession MR angiography (NCE-MRA) sequence and with contrast-enhanced magnetic resonance MR angiography (CE-MRA) sequences in the arterial and venous phases. Two blinded readers independently assessed arterial and venous anatomy and potential kidney lesions. Results of non-contrast-enhanced images were compared to CE-MRA and in a subgroup of 21 subjects to surgery as standard of reference. RESULTS: Regarding arterial anatomy, NCE-MRA yielded sensitivity, specificity, and accuracy of 100%, 89%, and 91% compared to CE-MRA. Three kidneys were found to have more accessory renal arteries at NCE-MRA than at CE-MRA. In the subgroup of 21 subjects, 1 surgically proven accessory artery was depicted with NCE-MRA but not with CE-MRA. Accuracy of T2-weighted images regarding accessory veins or variant venous course was 99%, with one missed circumaortic vein on T2-weighted images. Two simple cysts were missed on T2-weighted and NCE-MRA but not on CE-MRA images. CONCLUSION: A non-contrast-enhanced MR imaging protocol including NCE-MRA and T2-weighted images allows for the accurate screening of living related kidney donors and may serve as an alternative to CE-MRA.

Automated attenuation-based kilovoltage selection: preliminary observations in patients after endovascular aneurysm repair of the abdominal aorta.

OBJECTIVE: The objective of our study was to assess prospectively the impact of automated attenuation-based kilovoltage selection on image quality and radiation dose in patients undergoing body CT angiography (CTA) after endovascular aneurysm repair (EVAR) of the abdominal aorta. SUBJECTS AND METHODS: Thirty-five patients (five women, 30 men; mean age ± SD, 69 ± 13 years; mean body mass index ± SD, 27.3 ± 4.5 kg/m(2)) underwent 64-MDCT angiography of the thoracoabdominal aorta using a fixed 120-kVp protocol (scan A: 120 mAs [reference]; rotation time, 0.33 second; pitch, 1.2) and, within a median time interval of 224 days, using a protocol with automated kilovoltage selection (scan B: tube voltage, 80-140 kVp). Subjective image quality (5-point scale: 1 [excellent] to 5 [nondiagnostic]) and objective image quality (aortic attenuation at four locations of the aortoiliac system, noise, contrast-to-noise ratio [CNR]) were assessed independently by two blinded radiologists. The volume CT dose index (CTDI(vol)) was compared between scans A and B. RESULTS: The subjective image quality of scans A and B was similar (median score for both, 1; range, 1-4; p = 0.74), with all datasets being of diagnostic quality. Automated attenuation-based kilovoltage selection led to a reduction to 80 kVp in one patient (2.9%) and 100 kVp in 18 patients (51.4%). Fifteen of 35 patients (42.9%) were scanned at 120 kVp, whereas in one patient (2.9%) the kilovoltage setting increased to 140 kVp. Image noise (scan A vs scan B: mean ± SD, 12.8 ± 2.3 vs 13.7 ± 2.9 HU, respectively) was significantly (p < 0.05) higher in scan B than in scan A, whereas CNR was similar among scans (A vs B: mean ± SD, 15.7 ± 7.0 vs 16.9 ± 9.7; p = 0.43). The CTDI(vol) was significantly lower in scan B (mean ± SD, 8.9 ± 2.9 mGy; scan A, 10.6 ± 1.5 mGy; average reduction, 16%; p = 0.002) despite a higher tube current-exposure time product (B vs A: mean ± SD, 152 ± 27 vs 141 ± 29 mAs; p = 0.01). CONCLUSION: In patients undergoing follow-up after EVAR of the abdominal aorta, body CTA using automated attenuation-based kilovoltage selection yields similar subjective image quality and CNR at a significantly reduced dose compared with a protocol that uses 120 kVp.

Low-dose CT of the lung: potential value of iterative reconstructions.

OBJECTIVES: To prospectively assess the impact of sinogram-affirmed iterative reconstruction (SAFIRE) on image quality of nonenhanced low-dose lung CT as compared to filtered back projection (FBP). METHODS: Nonenhanced low-dose chest CT (tube current-time product: 30 mAs) was performed on 30 patients at 100 kVp and on 30 patients at 80 kVp. Images were reconstructed with FBP and SAFIRE. Two blinded, independent readers measured image noise; two readers assessed image quality of normal anatomic lung structures on a five-point scale. Radiation dose parameters were recorded. RESULTS: Image noise in datasets reconstructed with FBP (57.4 ± 15.9) was significantly higher than with SAFIRE (31.7 ± 9.8, P < 0.001). Image quality was significantly superior with SAFIRE than with FBP (P < 0.01), without significant difference between FBP at 100 kVp and SAFIRE at 80 kVp (P = 0.68). Diagnostic image quality was present with FBP in 96% of images at 100 kVp and 88% at 80 kVp, and with SAFIRE in 100% at 100 kVp and 98% at 80 kVp. There were significantly more datasets with diagnostic image quality with SAFIRE than with FBP (P < 0.01). Mean CTDI(vol) and effective doses were 1.5 ± 0.7 mGy·cm and 0.7 ± 0.2 mSv at 100 kVp, and 1.4 ± 2.8 mGy · cm and 0.5 ± 0.2 mSv at 80 kVp (P < 0.001, both). CONCLUSIONS: Use of SAFIRE in low-dose lung CT reduces noise, improves image quality, and renders more studies diagnostic as compared to FBP. KEY POINTS: Low-dose computed tomography is an important thoracic investigation tool. Radiation dose can be less than 1 mSv with iterative reconstructions. Iterative reconstructions render more low-dose lung CTs diagnostic compared to conventional reconstructions.

Performance of unenhanced respiratory-gated 3D SSFP MRA to depict hepatic and visceral artery anatomy and variants.

OBJECTIVES: To prospectively evaluate the performance of unenhanced respiratory-gated magnetization-prepared 3D-SSFP inversion recovery MRA (unenhanced-MRA) to depict hepatic and visceral artery anatomy and variants in comparison to contrast-enhanced dynamic gradient-echo MRI (CE-MRI) and to digital subtraction angiography (DSA). METHODS: Eighty-four patients (55.6±12.4 years) were imaged with CE-MRI (TR/TE 3.5/1.7ms, TI 1.7ms, flip-angle 15°) and unenhanced-MRA (TR/TE 4.4/2.2ms, TI 200ms, flip-angle 90°). Two independent readers assessed image quality of hepatic and visceral arteries on a 4-point-scale. Vessel contrast was measured by a third reader. In 28 patients arterial anatomy was compared to DSA. RESULTS: Interobserver agreement regarding image quality was good for CE-MRI (κ=0.77) and excellent for unenhanced-MRA (κ=0.83). Unenhanced-MRA yielded diagnostic image quality in 71.6% of all vessels, whereas CE-MRI provided diagnostic image quality in 90.6% (p<0.001). Vessel-based image quality was significantly superior for all vessels at CE-MRI compared to unenhanced-MRA (p<0.01). Vessel contrast was similar among both sequences (p=0.15). Compared to DSA, CE-MRI and unenhanced-MRA yielded equal accuracy of 92.9-96.4% for depiction of hepatic and visceral artery variants (p=0.93). CONCLUSIONS: Unenhanced-MRA provides diagnostic image quality in 72% of hepatic and visceral arteries with no significant difference in vessel contrast and similar accuracy to CE-MRI for depiction of hepatic and visceral anatomy.

Thoraco-abdominal high-pitch dual-source CT angiography: experimental evaluation of injection protocols with an anatomical human vascular phantom.

OBJECTIVE: To experimentally evaluate three different contrast injection protocols at thoraco-abdominal high-pitch dual-source computed tomography angiography (CTA), with regard to level and homogeneity of vascular enhancement at different cardiac outputs. MATERIALS AND METHODS: A uniphasic, a biphasic as well as an individually tailored contrast protocol were tested using a human vascular phantom. Each protocol was scanned at 5 different cardiac outputs (3-5L/min, steps of 0.5L/min) using an extracorporeal cardiac pump. Vascular enhancement of the thoraco-abdominal aorta was measured every 5 cm. Overall mean enhancement of each protocol and mean enhancement for each cardiac output within each protocol were calculated. Enhancement homogeneity along the z-axis was evaluated for each cardiac output and protocol. RESULTS: Overall mean enhancement was significantly higher in the uniphasic than in the other two protocols (all p<.05), whereas the difference between the biphasic and tailored protocol was not significant (p=.76). Mean enhancement among each of the 5 cardiac outputs within each protocol was significantly different (all p<.05). Only within the tailored protocol mean enhancement differed not significantly at cardiac outputs of 3.5L/min vs. 5L/min (484 ± 25 HU vs. 476 ± 19 HU, p=.14) and 4 vs. 5L/min (443 ± 49 HU vs. 476 ± 19 HU, p=.05). Both, uniphasic and tailored protocol yielded homogenous enhancement at all cardiac outputs, whereas the biphasic protocol failed to achieve homogenous enhancement. CONCLUSION: This phantom study suggests that diagnostic and homogenous enhancement at thoraco-abdominal high-pitch dual-source CTA is feasible with either a uniphasic or an individually tailored contrast protocol.

Automated attenuation-based tube potential selection for thoracoabdominal computed tomography angiography: improved dose effectiveness.

PURPOSE: To introduce a novel algorithm of automated attenuation-based tube potential selection and to assess its impact on image quality and radiation dose of body computed tomography angiography (CTA). MATERIALS AND METHODS: In all, 40 patients (mean age 71±11.8 years, body mass index (BMI) 25.7±3.8 kg/m², range 18.8-33.8 kg/m²) underwent 64-slice thoracoabdominal CTA (contrast material: 80 mL, 5 mL/s) using an automated tube potential selection algorithm (CAREkV), which optimizes tube-potential (70-140 kV) and tube-current (138.8±18.6 effective mAs, range 106-177 mAs) based on the attenuation profile of the topogram and on the diagnostic task. Image quality was semiquantitatively assessed by 2 blinded and independent readers (scores 1: excellent to 5: nondiagnostic). Attenuation and noise were measured by another 2 blinded and independent readers. Contrast-to-noise ratio was calculated. The CT dose index (CTDIvol) was recorded and compared with the estimated CTDIvol of a standard 120 kV protocol without using the algorithm in each patient. Selected tube potentials were correlated with BMI and attenuation of the topogram. RESULTS: Diagnostic image quality was obtained in all patients (excellent: 14; good: 21; moderate: 5; interreader agreement: κ=0.78). Mean attenuation, noise, and contrast-to-noise ratio were 260.8±63.5 Hounsfield units, 15.5±3.3 Hounsfield units, and 14±4.2, respectively, with good to excellent agreement between readers (r=0.50-0.99, P<0.01 each). Automated attenuation-based tube potential selection resulted in a kV-reduction from 120 to 100 kV in 23 patients and to 80 kV in 1 patient, whereas tube potential increased to 140 kV in 1 patient. Automatically selected tube potential showed a significant correlation with both BMI (r=0.427, P<0.05) and attenuation of the topogram (r=0.831, P<0.001). CTDIvol (7.95±2.6 mGy) was significantly lower when using the algorithm compared with the standard 120 kV protocol (10.59±1.8 mGy, P<0.001), corresponding to an overall dose reduction of 25.1%. CONCLUSION: Automated attenuation-based tube potential selection based on the attenuation profile of the topogram is feasible, provides a diagnostic image quality of body CTA, and reduces overall radiation dose by 25% as compared with a standard protocol with 120 kV.

Computed tomography of the lung in the high-pitch mode: is breath holding still required?

OBJECTIVES: To prospectively investigate whether the high-pitch mode (HPM) for computed tomography (CT) enables the diagnostic visualization of the lung parenchyma without suspended respiration. MATERIALS AND METHODS: A total of 40 consecutive patients (age, 67 ± 11 years) underwent 128-slice dual-source CT of the chest including nonenhanced, arterial, and venous phase of contrast. CT was performed in the HPM with a pitch of 3.2 during continuous breathing (group A) and during breath-hold (group B), and at standard pitch of 1 during deep-inspiratory breath-hold (group C). The 3 protocols were scanned in a random order in each patient. Two blinded readers independently assessed the image quality of 5 regions in both the lungs using a semiquantitative 3-point score. Image noise was measured as the standard deviation of attenuation. Presence and size of pulmonary nodules were noted and measured on each CT dataset. Lung volume was measured using dedicated semi-automated segmentation software. RESULTS: Interobserver agreement for image quality ratings was excellent (κ = 0.91). There were no significant differences in the number of lung regions having an image quality other than excellent between group A (2.5%) and B (1.5%, P = 0.48), whereas significantly less regions had impaired image quality in group B compared with group C (5.5%, P < 0.01). Image quality impairment in group C was because of breathing in 36% and cardiac pulsation in 64%. Image noise in group C (9 ± 2 HU) was significantly lower than that in group B (30 ± 2 HU, P < 0.001) whereas no significant difference was found between group A and B (P = 0.52). There were no significant differences for the depiction (P = 1.0) and size (P = 0.94) of lung nodules among the 3 modes. Average lung volume in group A was 75% ± 15% of that in deep inspiration (group B/C) being significantly smaller (P < 0.05). Estimated effective radiation doses in group C and group B were 5.8 ± 0.5 mSv and 1.6 ± 0.1 mSv, respectively. CONCLUSIONS: CT of the lung can be accomplished using the HPM at a low radiation dose with a diagnostic image quality even without suspended respiration.

Maximum diameter measurements of aortic aneurysms on axial CT images after endovascular aneurysm repair: sufficient for follow-up?

PURPOSE: To assess the accuracy of maximum diameter measurements of aortic aneurysms after endovascular aneurysm repair (EVAR) on axial computed tomographic (CT) images in comparison to maximum diameter measurements perpendicular to the intravascular centerline for follow-up by using three-dimensional (3D) volume measurements as the reference standard. MATERIALS AND METHODS: Forty-nine consecutive patients (73 ± 7.5 years, range 51-88 years), who underwent EVAR of an infrarenal aortic aneurysm were retrospectively included. Two blinded readers twice independently measured the maximum aneurysm diameter on axial CT images performed at discharge, and at 1 and 2 years after intervention. The maximum diameter perpendicular to the centerline was automatically measured. Volumes of the aortic aneurysms were calculated by dedicated semiautomated 3D segmentation software (3surgery, 3mensio, the Netherlands). Changes in diameter of 0.5 cm and in volume of 10% were considered clinically significant. Intra- and interobserver agreements were calculated by intraclass correlations (ICC) in a random effects analysis of variance. The two unidimensional measurement methods were correlated to the reference standard. RESULTS: Intra- and interobserver agreements for maximum aneurysm diameter measurements were excellent (ICC = 0.98 and ICC = 0.96, respectively). There was an excellent correlation between maximum aneurysm diameters measured on axial CT images and 3D volume measurements (r = 0.93, P < 0.001) as well as between maximum diameter measurements perpendicular to the centerline and 3D volume measurements (r = 0.93, P < 0.001). CONCLUSION: Measurements of maximum aneurysm diameters on axial CT images are an accurate, reliable, and robust method for follow-up after EVAR and can be used in daily routine.

Prospective and retrospective ECG-gating for CT coronary angiography perform similarly accurate at low heart rates.

OBJECTIVE: To compare, in patients with suspicion of coronary artery disease (CAD) and low heart rates, image quality, diagnostic performance, and radiation dose values of prospectively and retrospectively electrocardiography (ECG)-gated dual-source computed tomography coronary angiography (CTCA) for the diagnosis of significant coronary stenoses. MATERIALS AND METHODS: Two-hundred consecutive patients with heart rates ≤70 bpm were retrospectively enrolled; 100 patients undergoing prospectively ECG-gated CTCA (group 1) and 100 patients undergoing retrospectively-gated CTCA (group 2). Coronary artery segments were assessed for image quality and significant luminal diameter narrowing. Sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and accuracy of both CTCA groups were determined using conventional catheter angiography (CCA) as reference standard. Radiation dose values were calculated. RESULTS: Both groups were comparable regarding gender, body weight, cardiovascular risk profile, severity of CAD, mean heart rate, heart rate variability, and Agatston score (all p>0.05). There was no significant difference in the rate of non-assessable coronary segments between group 1 (1.6%, 24/1404) and group 2 (1.4%, 19/1385; p=0.77); non-diagnostic image quality was significantly (p<0.001) more often attributed to stair step artifacts in group 1. Segment-based sensitivity, specificity, PPV, NPV, and accuracy were 98%, 98%, 88%, 100%, and 100% among group 1; 96%, 99%, 90%, 100%, and 98% among group 2, respectively. Parameters of diagnostic performance were similar (all p>0.05). Mean effective radiation dose of prospectively ECG-gated CTCA (2.2±0.4 mSv) was significantly (p<0.0001) smaller than that of retrospectively ECG-gated CTCA (8.1±0.6 mSv). CONCLUSION: Prospectively ECG-gated CTCA yields similar image quality, performs as accurately as retrospectively ECG-gated CTCA in patients having heart rates ≤70 bpm while being associated with a lower mean effective radiation dose.

Cardiac CT for the differentiation of bicuspid and tricuspid aortic valves: comparison with echocardiography and surgery.

OBJECTIVE: The purpose of this study is to evaluate the diagnostic performance of CT, compared with that of echocardiography and surgery, for differentiating between bicuspid and tricuspid aortic valves. MATERIALS AND METHODS: Forty-seven patients with bicuspid valve and 47 patients with tricuspid aortic valve underwent retrospectively ECG-gated dual-source CT and echocardiography. Thirty-four (72%) of the 47 patients with bicuspid aortic valve underwent valve surgery. Two independent blinded observers assessed the CT image quality of the aortic valve during diastole and systole on a 4-point scale, determined which phase allowed the differentiation of valve type, distinguished between tricuspid and bicuspid aortic valves, and assessed for the presence of a raphe. Diagnostic performance of CT was determined using echocardiography and surgery as the reference standard. RESULTS: According to echocardiography and surgery, seven (15%) of the 47 bicuspid aortic valves had no raphe, and 40 (85%) had a raphe. CT image quality was diagnostic (i.e., scores of 1-3) in all 94 patients in both diastole and systole. Among patients with bicuspid aortic valve and no raphe, differentiation between tricuspid and bicuspid aortic valves could be performed in diastole in 100% (7/7) of cases. Among patients with bicuspid aortic valve and raphe, differentiation was possible only in systole in 5% (2/40) of cases and when combining diastole and systole in 95% (38/40) of cases. In three bicuspid aortic valves with raphe, the valve was misclassified by CT as tricuspid aortic valve. Overall sensitivity and specificity of CT for the diagnosis of bicuspid aortic valve were 94% and 100%. CONCLUSION: CT is highly accurate for differentiation between bicuspid and tricuspid aortic valves. For bicuspid aortic valves without raphe, diastolic reconstructions are sufficient, whereas in those with a raphe, additional reconstructions in systole are required.