Jan-Erik Scholtz

Comprehensive Comparison of Virtual Monoenergetic and Linearly Blended Reconstruction Techniques in Third-Generation Dual-Source Dual-Energy Computed Tomography Angiography of the Thorax and Abdomen.

ObjectivesThe aim of this study was to perform an objective and subjective image analysis of traditional and advanced noise-optimized virtual monoenergetic imaging (VMI) algorithms and standard linearly blended images in third-generation dual-source dual-energy computed tomography angiography (DE-CTA) of the thorax and abdomen. Materials and MethodsThoracoabdominal DE-CTA examinations of 55 patients (36 male; mean age, 64.2 ± 12.7 years) were included in this retrospective institutional review board–approved study. Dual-energy computed tomography angiography data were reconstructed using standard linearly blended M_0.6 (merging 60% low kiloelectron volt [90 kV] with 40% high kiloelectron volt [150 kV] spectrum), traditional (VMI), and advanced VMI (VMI+) algorithms. Monoenergetic series were calculated ranging from 40 to 120 keV with 10 keV increments. Attenuation and standard deviation of 8 arteries and various anatomical landmarks of the thorax and abdomen were measured to calculate contrast-to-noise ratio values. Two radiologists subjectively assessed image quality, contrast conditions, noise, and visualization of small arterial branches using 5-point Likert scales. ResultsVascular attenuation of VMI and VMI+ series showed a gradual increase from high to low kiloelectron volt levels without significant differences between both algorithms (P < 0.894). VMI+ 40-keV series showed the highest contrast-to-noise ratio for both thoracic and abdominal DE-CTA (P < 0.001), albeit revealing higher noise than M_0.6 images (objectively and subjectively, P < 0.001) and were rated best for visualization of small arterial branches in the subjective analysis (P < 0.109). Substantially increased noise was found for VMI 40 and 50 keV series compared with all other reconstructions (objectively and subjectively, P < 0.001). VMI+ images at 100 keV+ were rated best regarding image noise (P < 0.843), whereas VMI+ reconstructions at 70 keV were found to have superior subjective image quality (P < 0.031) compared with other series except for 60 and 80 keV VMI+ series (P < 0.587). Contrast conditions at 50 keV VMI+ were rated superior compared with 60 to 100 keV VMI and VMI+ reconstructions (P < 0.012). ConclusionsGeneral image quality of DE-CTA examinations can be substantially improved using the VMI+ algorithm with observer preference of 70 keV, while 40 to 50 keV series provide superior contrast and improved visualization of small arterial branches compared with traditional VMI and standard linearly blended series.

Dual-Energy CT–based Display of Bone Marrow Edema in Osteoporotic Vertebral Compression Fractures: Impact on Diagnostic Accuracy of Radiologists with Varying Levels of Experience in Correlation to MR Imaging

Purpose To evaluate whether a dual-energy (DE) computed tomographic (CT) virtual noncalcium technique can improve the detection rate of acute thoracolumbar vertebral compression fractures in patients with osteoporosis compared with that at magnetic resonance (MR) imaging depending on the level of experience of the reading radiologist. Materials and Methods This retrospective study was approved by the institutional ethics committee. Informed consent was obtained from all patients. Forty-nine patients with osteoporosis who were suspected of having acute vertebral fracture underwent DE CT and MR imaging. Conventional linear-blended CT scans and corresponding virtual noncalcium reconstructions were obtained. Five radiologists with varying levels of experience evaluated gray-scale CT scans for the presence of fractures and their suspected age. Then, virtual noncalcium images were evaluated to detect bone marrow edema. Findings were compared with those from MR imaging (the standard of reference). Sensitivity and specificity analyses for diagnostic performance and matched pair analyses were performed on vertebral fracture and patient levels. Results Sixty-two fractures were classified as fresh and 52 as old at MR imaging. The diagnostic performance of all readers in the detection of fresh fractures improved with the addition of virtual noncalcium reconstructions compared with that with conventional CT alone. Although the diagnostic accuracy of the least experienced reader with virtual noncalcium CT (accuracy with CT alone, 61%; accuracy with virtual noncalcium technique, 83%) was within the range of that of the most experienced reader with CT alone, the latter improved his accuracy with the noncalcium technique (from 81% to 95%), coming close to that with MR imaging. The number of vertebrae rated as unclear decreased by 59%-90% or from 15-53 to 2-13 in absolute numbers across readers. The number of patients potentially referred to MR imaging decreased by 36%-87% (from 11-23 to 2-10 patients). Considering the gain in true decisions with the virtual noncalcium technique on a patient level, between 12 (most experienced reader) and 17 (least experienced reader) MR examinations could have been avoided. Conclusion The DE CT-based virtual noncalcium technique may enable depiction of bone marrow edema in thoracolumbar vertebral compression fractures in patients with osteoporosis, with good accordance with MR imaging when images are read by experienced radiologists. Although less experienced readers improved their diagnostic performance to some degree, the experienced readers diagnostic performance approached that with MR imaging. (©) RSNA, 2016.

70 kVp computed tomography pulmonary angiography: potential for reduction of iodine load and radiation dose.

Purpose: The purpose of the study was to evaluate 70 kVp dual-source computed tomography pulmonary angiography (CTPA) with reduced iodine load in comparison with single-source 70 and 100 kVp CTPA with standard iodine load regarding image quality and radiation dose. Materials and Methods: Three groups with 40 consecutive patients each underwent either standard single-source 100 kVp (120 mAs; group A), single-source 70 kVp (208 mAs; group B), or dual-source 70 kVp CTPA (416 mAs; group C). A volume of 70 mL of contrast material with 400 mg I/mL (groups A, B) or 300 mg I/mL (group C) was administered. Chest diameter, dose-length product, intravascular signal attenuation, image noise, signal to noise ratio (SNR), and contrast to noise ratio (CNR) were compared. Two observers rated subjective image quality regarding intravascular enhancement and image noise using 5-point scales. Results: Chest diameter and age were similar (P≥0.28) for all groups. Compared with group A, the average dose-length product was 59% lower in group B (67.3±11.8 vs. 164.7±50.6 mGy cm, P<0.001) and similar between groups A and C (167.7±41.2 mGy cm, P=0.39). Average SNR and CNR were significantly higher for group C (21.5±4.7 and 19.0±4.5, respectively) compared with groups A (18.3±3.5 and 15.8±3.4, respectively) and B (17.3±5.8 and 15.6±5.5, respectively; all Ps⩽0.001). Subjective image quality ratings regarding enhancement and noise were highest for group C (1.73±0.62 and 2.03±0.66, respectively). Conclusions: Compared with standard 100 kVp CTPA, single-source 70 kVp CTPA allows for significant radiation dose savings with comparable SNR and CNR, whereas dual-source 70 kVp CTPA results in a superior objective image quality albeit a reduction of iodine concentration.

Automated Tube Voltage Adaptation in Combination with Advanced Modeled Iterative Reconstruction in Thoracoabdominal Third-Generation 192-Slice Dual-Source Computed Tomography: Effects on Image Quality and Radiation Dose

RATIONALE AND OBJECTIVES To evaluate image quality and radiation exposure of portal venous-phase thoracoabdominal third-generation 192-slice dual-source computed tomography (DSCT) with automated tube voltage adaptation (TVA) in combination with advanced modeled iterative reconstruction (ADMIRE). MATERIALS AND METHODS Fifty-one patients underwent oncologic portal venous-phase thoracoabdominal follow-up CT twice within 7 months. The initial examination was performed on second-generation 128-slice DSCT with fixed tube voltage of 120 kV in combination with filtered back projection reconstruction. The second examination was performed on a third-generation 192-slice DSCT using automated TVA in combination with ADMIRE. Attenuation and image noise of liver, spleen, renal cortex, aorta, vena cava inferior, portal vein, psoas muscle, and perinephric fat were measured. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Radiation dose was assessed as size-specific dose estimates (SSDE). Subjective image quality was assessed by two observers using five-point Likert scales. Interobserver agreement was calculated using intraclass correlation coefficients (ICC). RESULTS Automated TVA set tube voltage to 90 kV (n = 8), 100 kV (n = 31), 110 kV (n = 11), or 120 kV (n = 1). Average SSDE was decreased by 34.9% using 192-slice DSCT compared to 128-slice 120-kV DSCT (7.8 ± 2.4 vs. 12.1 ± 3.2 mGy; P < .001). Image noise was substantially lower; SNR and CNR were significantly increased in 192-slice DSCT compared to 128-slice DSCT (all P < .005). Image quality was voted excellent for both acquisition techniques (5.00 vs. 4.93; P = .083). CONCLUSIONS Automated TVA in combination with ADMIRE on third-generation 192-slice DSCT in portal venous-phase thoracoabdominal CT provides excellent image quality with reduced image noise and increased SNR and CNR, whereas average radiation dose is reduced by 34.9% compared to 128-slice DSCT.

Low-dose abdominal computed tomography for detection of urinary stone disease − Impact of additional spectral shaping of the X-ray beam on image quality and dose parameters

OBJECTIVES To evaluate a novel tin filter-based abdominal CT protocol for urolithiasis in terms of image quality and CT dose parameters. METHODS 130 consecutive patients with suspected urolithiasis underwent non-enhanced CT with three different protocols: 48 patients (group 1) were examined at tin-filtered 150kV (150kV Sn) on a third-generation dual-source-CT, 33 patients were examined with automated kV-selection (110-140kV) based on the scout view on the same CT-device (group 2), and 49 patients were examined on a second-generation dual-source-CT (group 3) with automated kV-selection (100-140kV). Automated exposure control was active in all groups. Image quality was subjectively evaluated on a 5-point-likert-scale by two radiologists and interobserver agreement as well as signal-to-noise-ratio (SNR) was calculated. Dose-length-product (DLP) and volume CT dose index (CTDIvol) were compared. RESULTS Image quality was rated in favour for the tin filter protocol with excellent interobserver agreement (ICC=0.86-0.91) and the difference reached statistical significance (p<0.001). SNR was significantly higher in group 1 and 2 compared to second-generation DSCT (p<0.001). On third-generation dual-source CT, there was no significant difference in SNR between the 150kV Sn and the automated kV selection protocol (p=0.5). The DLP of group 1 was 23% and 21% (p<0.002) lower in comparison to group 2 and 3, respectively. So was the CTDIvol of group 1 compared to group 2 (-36%) and 3 (-32%) (p<0.001). CONCLUSION Additional shaping of a 150kV source spectrum by a tin filter substantially lowers patient exposure while improving image quality on un-enhanced abdominal computed tomography for urinary stone disease.

Noise-optimized advanced image-based virtual monoenergetic imaging for improved visualization of lung cancer: Comparison with traditional virtual monoenergetic imaging

PURPOSE To assess the effect of a noise-optimized image-based virtual monoenergetic imaging (VMI+) algorithm in direct comparison with the traditional VMI technique and standard linearly-blended images emulating 120-kVp acquisition (M_0.3) on image quality at dual-energy CT in patients with lung cancer. MATERIALS AND METHODS Dual-source dual-energy CT examinations of 48 patients with biopsy-proven primary (n=31) or recurrent (n=20) lung cancer were evaluated. Images were reconstructed as M_0.3, and VMI+ and traditional VMI series at 40, 55, and 70keV. Attenuation of tumor, descending aorta, pulmonary trunk, latissimus muscle, and noise were measured. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Five-point scales were used by three observers to subjectively evaluate general image impression, tumor delineation, image sharpness, and image noise. RESULTS Background noise was consistently lower with VMI+ compared to VMI at all keV levels (all p<0.0001) and M_0.3 (all p≤0.0004). Tumor SNR and CNR peaked in the 40keV VMI+ series, significantly higher compared to all VMI and M_0.3 series (all p<0.0008). Observers preferred the 55keV VMI+ series regarding general image impression and tumor delineation compared to all other series (all p<0.0001). Image sharpness and image noise ratings were highest in the 55keV VMI+ and 70keV VMI and VMI+ reconstructions. CONCLUSIONS Tumor CNR peaked at 40keV VMI+ while observers preferred 55keV VMI+ series overall other series for dual-energy CT of lung cancer. The noise-optimized VMI+ technique showed significantly lower background noise and higher SNR and CNR compared to the traditional VMI technique at matching keV levels.

Evaluation of image quality and dose reduction of 80 kVp neck computed tomography in patients with suspected peritonsillar abscess

AIM To evaluate neck computed tomography (CT) with a reduced tube voltage of 80 kVp in patients with suspected peritonsillar abscess (PTA) regarding objective and subjective image quality, and the potential for dose reduction. MATERIALS AND METHODS Forty-seven patients with clinically suspected PTA were retrospectively analysed. Patients were examined using dual-source CT in dual-energy mode. The objective and subjective image quality of 80 kVp images were compared with linearly blended 120 kVp images (M_0.3; 30% of 80 kV, 70% of 140 kV spectrum). Attenuation of abscess rim enhancement, central necrosis, and several other anatomical landmarks were measured. The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and rim-to-abscess CNR (raCNR) were calculated. Radiation dose was assessed as size-specific dose estimates (SSDE). Subjective image quality was assessed according to the European guidelines on quality criteria for CT. Interobserver agreement was calculated using the intraclass correlation coefficient (ICC). RESULTS Attenuation of inflamed soft tissue (141.7 ± 16.3 versus 93.7 ± 9.3 HU, p < 0.001), CNR (9.6 ± 4.8 versus 5.6 ± 3.8, p = 0.001), raCNR (14.3 ± 5.9 versus 12.4 ± 4.4, p = 0.02), and subjective image sharpness (3.6 ± 0.6 versus 2.8 ± 0.7, p < 0.001) were significantly increased in the 80 kVp compared to 120 kVp, whereas subjective and objective image noise were significantly increased with 80 kVp acquisition (p < 0.001). Overall interobserver agreement was almost perfect (ICC, 0.87). Calculated SSDE of 80 kVp acquisition was decreased by 49.7% compared to 120 kVp (10.58 ± 0.76 versus 21.04 ± 1.43 mGy, p < 0.001). CONCLUSION Low-tube-voltage 80 kVp neck CT provides increased enhancement of soft-tissue inflammation, CNR, raCNR, and improved abscess delineation in patients with PTA compared to standard 120 kVp acquisition while resulting in a significant reduction of radiation exposure.

Comparative evaluation of non-contrast CAIPIRINHA-VIBE 3T-MRI and multidetector CT for detection of pulmonary nodules: In vivo evaluation of diagnostic accuracy and image quality

PURPOSE To evaluate the diagnostic accuracy, subjective image quality, and interobserver agreement of non-contrast Controlled Aliasing In Parallel Imaging Results In Higher Acceleration (CAIPIRINHA) volumetric interpolated breath-hold examination (VIBE) 3T magnetic resonance imaging (MRI) for the detection of pulmonary nodules with intra-individual comparison to computed tomography (CT). MATERIALS AND METHODS We evaluated 54 patients (27 male, 27 female; mean age, 60.8 ± 11.5 years) who prospectively underwent thoracic 3T-MRI using CAIPIRINHA-VIBE sequences and chest CT. Diagnostic accuracy for the detection of lung nodules on CAIPIRINHA-VIBE MRI by three independent observers were compared to the reference standard CT. Subjective image quality was rated using a 5-point grading scale. Diagnostic accuracy was calculated and interobserver agreement was assessed using intraclass correlation coefficient (ICC). RESULTS Sensitivity of 3T-MRI for the detection of pulmonary lesions compared to CT was 88.1% (95% confidence interval [CI]: 0.81-0.93) and specifity was 79.1% (95% CI: 0.50-0.95). Sensitivity for lesions <5mm was 77.2% (95% CI: 0.59-0.90) and for lesions from 5 to 10mm was 87.2% (95% CI: 0.76-0.94). Sensitivity for lesions >10mm was 100%. Observer ratings regarding subjective image quality were good to excellent for 3T-MRI (1.54) and CT (1.14) with almost perfect interobserver agreement for 3T-MRI and CT (ICC=0.83, 95% CI: 0.78-0.89; ICC=0.89, 95% CI: 0.85-0.94). CONCLUSIONS Non-contrast CAIPIRINHA-VIBE 3T-MRI allows for the reliable detection of pulmonary lesions with a diameter >5mm in comparison with chest CT with high diagnostic accuracy, subjective image quality, and interobserver agreement.

Noise-Optimized Virtual Monoenergetic Dual-Energy CT Improves Diagnostic Accuracy for the Detection of Active Arterial Bleeding of the Abdomen

PURPOSE To evaluate diagnostic accuracy of a noise-optimized virtual monoenergetic imaging (VMI+) reconstruction technique for detection of active arterial abdominal bleeding on dual-energy (DE) CT angiography compared with standard image reconstruction. MATERIALS AND METHODS DE CT angiography data sets of 71 patients (46 men; age 63.6 y ± 13.3) with suspected arterial bleeding of the abdomen or pelvis were reconstructed with standard linearly blended (F_0.5), VMI+, and traditional virtual monoenergetic imaging (VMI) algorithms in 10-keV increments from 40 to 100 keV. Attenuation measurements were performed in the descending aorta, area of hemorrhage, and feeding artery to calculate contrast-to-noise ratios (CNRs) in patients with active arterial bleeding. Based on quantitative image quality results, the best series for each reconstruction technique were chosen to analyze the diagnostic performance of 3 blinded radiologists. RESULTS DE CT angiography showed acute arterial bleeding in 36 patients. Mean CNR was superior in 40-keV VMI+ compared with VMI series (all P < .001), which showed highest CNRs in 70-keV VMI and F_0.5 (21.6 ± 7.9, 12.9 ± 4.7, and 10.4 ± 3.6) images. Area under the curve analysis for detection of arterial bleeding showed significantly superior (P < .001) results for 40-keV VMI+ (0.963) compared with 70-keV VMI (0.775) and F_0.5 (0.817) series. CONCLUSIONS Diagnostic accuracy in patients with active arterial bleeding of the abdomen can be significantly improved using VMI+ reconstructions at 40 keV compared with standard linearly blended and traditional VMI series in DE CT angiography.

Percutaneous cannulated screw fixation of sacral fractures and sacroiliac joint disruptions with CT-controlled guidewires performed by interventionalists: Single center experience in treating posterior pelvic instability

OBJECTIVE The purpose of our study was to evaluate minimally invasive sacroiliac screw fixation for treatment of posterior pelvic instability with the help of CT controlled guidewires, assess its accuracy, safety and effectiveness, and discuss potential pitfalls. METHODS 100 guidewires and hollow titan screws were inserted in 38 patients (49.6±19.5 years) suffering from 35 sacral fractures and/or 16 sacroiliac joint disruptions due to 33 (poly-)traumatic, 2 osteoporotic and 1 post-infectious conditions. The guidewire and screw positions were analyzed in multiplanar reconstructions. RESULTS The mean minimal distance between guidewire and adjacent neural foramina was 4.5±2.01mm, with a distinctly higher precision in S1 than S2. Eight guidewires showed cortical contacts, resulting in a total of 2% mismatched screws with subsequent wall violation. The fracture gaps were reduced from 3.6±0.53mm to 1.2±0.54mm. During follow-up 3 cases of minor iatrogenic sacral impaction (<5mm) due to the bolting and 2 cases of screw loosening were observed. Interventional time was 84.0min with a mean of 2.63 screws per patient whilst acquiring a mean of 93.7 interventional CT-images (DLP 336.7mGycm). CONCLUSIONS The treatment of posterior pelvic instability with a guidewire-based screw insertion technique under CT-imaging results in a very high accuracy and efficacy with a low complication rate. Careful attention should be drawn to radiation levels.