Stefan Bulla

Dual-Energy CT Virtual Noncalcium Technique: Detecting Posttraumatic Bone Marrow Lesions—Feasibility Study

PURPOSE To evaluate traumatized bone marrow with a dual-energy (DE) computed tomographic (CT) virtual noncalcium technique. MATERIALS AND METHODS In this prospective institutional review board-approved study, 21 patients with an acute knee trauma underwent DE CT and magnetic resonance (MR) imaging. A software application was used to virtually subtract calcium from the images. Presence of fractures was noted, and presence of bone bruise was rated on a four-point scale for six femoral and tibial regions by two radiologists. CT numbers were obtained in the same regions. Consensus reading of independently read MR images served as the reference standard. Image ratings and CT numbers were subjected to receiver operating characteristic curve analysis. RESULTS After exclusion of 16 regions owing to artifacts, MR imaging revealed 59 bone bruises in the remaining 236 regions (19 of 114 femoral, 40 of 122 tibial). Fractures were present in eight patients. Visual rating revealed areas under the curve of 0.886 and 0.897 in the femur and 0.974 and 0.953 in the tibia for observers 1 and 2, respectively. For CT numbers, the respective areas under the curve were 0.922 and 0.974. If scores of 1 and 2 (strong or mild bone bruise) were counted as positive, sensitivities were 86.4% and 86.4% and specificities were 94.4% and 95.5% for observers 1 and 2, respectively. The kappa statistic demonstrated good to excellent agreement (femur, kappa = 0.78; tibia, kappa = 0.87). CONCLUSION This DE CT virtual noncalcium technique can subtract calcium from cancellous bone, allowing bone marrow assessment and potentially making posttraumatic bone bruises of the knee detectable with CT.

Prospective electrocardiography-triggered CT angiography of the great thoracic vessels in infants and toddlers with congenital heart disease: Feasibility and image quality

PURPOSE To investigate feasibility and image quality and to calculate radiation dose estimates for computed tomography angiography (CTA) of the great thoracic vessels in infants and toddlers with congenital heart disease (CHD) using end-systolic prospective electrocardiography-triggered sequential dual-source data acquisition. METHODS This study was institutional review board approved; informed consent was obtained. Twenty children (age 1.2±1.1 years) underwent 22 prospective ECG-triggered sequential dual-source CTA examinations (Somatom Definition, Siemens) with tube current (250 mAs/rot) centered at 250 ms past the R-peak in the cardiac cycle (end-systole). Tube voltage was set to 80 kV. Image quality was evaluated by two readers independently using a four-point grading scale (4=excellent, 1=non-diagnostic). Radiation dose estimates were calculated from the dose-length-product (DLP). RESULTS All CT images showed diagnostic image quality (mean score 3.67±0.67, κ=0.85). Stair-step artifacts were present in one and breathing artifacts in 4 patients, with neither impairing diagnostic image quality. Mean heart rate (bpm) was 107.6±12.1 (76-130), mean heart rate variability (bpm) was 2.5±2.0 (1-9). Mean scan length (mm) was 90.7±22.7 (50-134). Mean estimated effective dose was 0.32±0.11 mSv. CONCLUSION Prospective ECG-triggered sequential dual source CTA is feasible in infants and toddlers with CHD, thereby allowing almost motion-free imaging of the great thoracic vessels with the benefit of a low radiation dose.

Reducing the radiation dose for low-dose CT of the paranasal sinuses using iterative reconstruction: Feasibility and image quality

PURPOSE To evaluate image quality of dose-reduced CT of the paranasal-sinus using an iterative reconstruction technique. METHODS In this study 80 patients (mean age: 46.9±18 years) underwent CT of the paranasalsinus (Siemens Definition, Forchheim, Germany), with either standard settings (A: 120 kV, 60 mAs) reconstructed with conventional filtered back projection (FBP) or with tube current-time product lowering of 20%, 40% and 60% (B: 48 mAs, C: 36 mAs and D: 24 mAs) using iterative reconstruction (n=20 each). Subjective image quality was independently assessed by four blinded observers using a semiquantitative five-point grading scale (1=poor, 5=excellent). Effective dose was calculated from the dose-length product. Mann-Whitney-U-test was used for statistical analysis. RESULTS Mean effective dose was 0.28±0.03 mSv(A), 0.23±0.02 mSv(B), 0.17±0.02 mSv(C) and 0.11±0.01 mSv(D) resulting in a maximum dose reduction of 60% with iterative reconstruction technique as compared to the standard low-dose CT. Best image quality was observed at 48 mAs (mean 4.8; p<0.05), whereas standard low-dose CT (A) and maximum dose reduced scans (D) showed no significant difference in subjective image quality (mean 4.37 (A) and 4.31 (B); p=0.72). Interobserver agreement was excellent (κ values 0.79-0.93). CONCLUSION As compared to filtered back projection, the iterative reconstruction technique allows for significant dose reduction of up to 60% for paranasal-sinus CT without impairing the diagnostic image quality.

Thoracic Aorta: Prospective Electrocardiographically Triggered CT Angiography with Dual-Source CT—Feasibility, Image Quality, and Dose Reduction

PURPOSE To prospectively investigate the feasibility, image quality, and radiation dose for prospective electrocardiographically (ECG) triggered sequential dual-source computed tomographic (CT) angiography of the thoracic aorta in comparison to retrospective ECG-gated helical dual-source CT angiography. MATERIALS AND METHODS This study was approved by the institutional review board; informed consent was obtained. One hundred thirty-nine patients referred for ECG-assisted dual-source CT angiography of the thoracic aorta were prospectively enrolled. Inclusion criteria were stable sinus rhythm and heart rate of 80 beats per minute or less. Tube voltage was adjusted to body mass index (< 25.0 kg/m(2), 100 kV, n = 58; > or = 25.0 kg/m(2), 120 kV, n = 81). In both cohorts, patients were randomly assigned to prospective or retrospective ECG-assisted data acquisition. In both groups, tube current (250 mAs per rotation) was centered at 70% of the R-R cycle. The presence of motion or stair-step artifacts of the thoracic aorta was independently assessed by two readers. Effective radiation dose was calculated from the dose-length product. RESULTS Subjective scoring of motion and stair-step artifacts was equivalent for both techniques. Scan length was not significantly different (23.8 cm +/- 2.4 [standard deviation] vs 23.7 cm +/- 2.5 for prospective and retrospective ECG-triggered CT angiography, respectively; P = .54). Scanning time was significantly longer for prospective ECG-triggered CT angiography (18.8 seconds +/- 3.4 vs 16.4 seconds +/- 3.3, P < .001). Mean estimated effective dose was significantly lower for prospective data acquisition (100 kV, 1.9 mSv +/- 0.5 vs 4.1 mSv +/- 0.7, P < .001; 120 kV, 5.3 mSv +/- 1.1 vs 9.5 mSv +/- 3.0, P < .001). CONCLUSION Prospective ECG-gated sequential dual-source CT angiography of the thoracic aorta is feasible, despite the slightly longer acquisition time. Thus, motion-free imaging of the thoracic aorta is possible at significantly lower radiation exposure than retrospective ECG-gated helical dual-source CT angiography in certain patients with a regular heart rate.

The new mid-scala electrode array: a radiologic and histologic study in human temporal bones.

Hypothesis To analyze the quality of insertion of the newly developed midscala (MS) electrode, which targets a midscalar electrode position to reduce the risk of trauma to the lateral wall and the modiolus. Background Modern cochlear implant surgery aims for a safe intracochlear placement of electrode arrays with an ongoing debate regarding cochleostomy or round window (RW) insertion and the use of lateral wall or perimodiolar electrode placement. Intracochlear trauma after insertion of different electrodes depends on insertion mode and electrode design and may result in trauma to the delicate structures of the cochlear. Methods We performed a temporal bone (TB) trial with insertion of the MS electrode in n = 20 TB‘s after a mastoidectomy and posterior tympanotomy. Insertion was performed either via the RW or a cochleostomy. Electrode positioning, length of insertion, and angle of insertion were analyzed with rotational tomography (RT). TBs were histologically analyzed. Results of RT and histology were compared. Results Scala tympani (ST) insertion could be accomplished reliably by both RW and via a cochleostomy approach. In 20 TBs, 1 scala vestibuli insertion, 1 incomplete (ST), and 1 elevation of basilar membrane were depicted. No trauma was found in 94.7% of all ST insertions. RT allowed determination of the intracochlear electrode position, which was specified by histologic sectioning. Conclusion The new MS electrode seems to fulfill reliable atraumatic intracochlear placement via RW and cochleostomy approaches. RT is available for evaluation of intracochlear electrode position, serving as a potential quality control instrument in human implantation.

Dose Reduction Does Not Affect Detection of Bone Marrow Lesions with Dual-energy CT Virtual Noncalcium Technique

RATIONALE AND OBJECTIVES The aim of this study was to evaluate if a dose-reduced, dose-neutral dual-energy computed tomographic (CT) virtual noncalcium technique can equally detect posttraumatic bone marrow lesions (BMLs) of the knee. MATERIALS AND METHODS Fifty patients underwent DE CT imaging with either a standard dose (group A) or a dose equal to that of a single-energy CT scan (group B) (28% dose reduction) and magnetic resonance imaging for knee trauma workup. Calcium was virtually subtracted from the images. Two radiologists rated the presence of abnormal soft tissue-like attenuation in the bone marrow in a total of 12 femoral and tibial regions and performed Hounsfield unit measurements thereafter. Receiver-operating characteristic curve analysis was used for four-point rating scores and Hounsfield unit measurements. Fractures were classified. RESULTS Magnetic resonance imaging depicted 170 BMLs (35 femoral, 135 tibial). Mean age, number of fractures, attenuation values and number of regions with BMLs were not significantly different between the groups. Visual rating revealed overall areas under the curves of 0.983 and 0.979 for observers 1 and 2, respectively. Visual judgment was superior to attenuation measurements for femoral regions regardless of the dose applied. Analysis of variance of all CT values revealed a significant influence for the presence of edema (P < .001) but no differences for the radiation dose used (P = .424). Interobserver agreement was excellent (κ = 0.944). CONCLUSIONS Dose reduction does not affect the detectability of posttraumatic BMLs with a dual-energy CT virtual noncalcium technique, thereby providing potential additional information compared with single-energy CT imaging without additional radiation dose.

Radiologic Results and Hearing Preservation With a Straight Narrow Electrode via Round Window Versus Cochleostomy Approach at Initial Activation.

Objective To evaluate the potential influence of two different cochlear implant (CI) electrode carrier approaches to the scala tympani in terms of insertion depth and angle as well as hearing preservation. Study Design Retrospective follow-up study. Setting Tertiary care academic center. Patients Forty-one adult subjects underwent cochlear implantation using the Cochlear Nucleus CI 422 slim straight electrode (Cochlear Limited, New South Wales, Australia) with the intent of achieving atraumatic electrode insertion and hearing preservation. Interventions Fourteen subjects were implanted using a cochleostomy approach and 27 via a round window approach. Main Outcome Measures Radiologic assessment of insertion depth and angle was performed on postoperative rotational tomography. Postoperative low-frequency hearing preservation, complete loss of residual low-frequency hearing, and speech perception in quiet measures were obtained in defined intervals for both groups. Results Mean insertion depth reached 21.5 mm (standard deviation, 1.1), whereas mean insertion angle of 388 degrees (standard deviation, 34.7) was revealed for all CI recipients, with no significant difference between the cochleostomy cohort and the round window cohort. The CI-aided speech perception in quiet showed significantly higher scores 3 to 4 months after activation compared with the preoperative speech perception results. The audiologic data demonstrated no statistically significant difference in probability of complete loss of residual low-frequency hearing at initial activation between the cochleostomy group and the round window group. Conclusion The present results suggest that similar insertion depth and angle as well as similar low-frequency hearing preservation can be achieved in cochlear implantation with this straight narrow electrode via either cochleostomy approach or round window approach at least at initial activation. This fact gives the surgeon the opportunity to adapt access to the scala tympani as needed.

Prospective ECG-Triggered CT Angiography of the Thoracic Aorta in Patients With Atrial Fibrillation or Accelerated Heart Rates: Feasibility and Image Quality

OBJECTIVE The objective of our study was to prospectively investigate the feasibility and image quality of and to calculate the radiation dose estimates for CT angiography (CTA) of the thoracic aorta in patients with atrial fibrillation or accelerated heart rates using prospective ECG-triggered sequential dual-source data acquisition in end-systole. CONCLUSION Prospective ECG-gated sequential dual-source CTA of the thoracic aorta is feasible despite heart rates>80 beats per minute or atrial fibrillation, making motion-free imaging of the thoracic aorta possible at a considerably low radiation dose.

Letter to the editor re: low-dose computed tomography of the paranasal sinus and facial skull using a high-pitch dual-source system—First clinical results

Dear Editor, We read with great interest the article “Low-dose computed tomography of the paranasal sinus and facial skull using a high-pitch dual-source system-First clinical results” by Schell et al. [1]. The authors compared image quality and radiation dose of CT examinations of the paranasal sinus and facial skull in 73 patients, which were acquired with two different CT systems: a 16-slice single source and a 128-slice dual-source CT system which was operated in either singleor dual-source mode. With the other parameters remaining constant, the dual-source mode utilized a high pitch factor of 3.0 instead of 0.9 employed for the two single-source protocols. As stated in the paper, the authors found a 50% dose reduction for the proposed dual-source high-pitch mode as compared to the single-source protocol without loss in diagnostic image quality. In our understanding the approach for estimating the radiation dose of the dual-source high-pitch protocol reported by Shell et al. is incorrect. Up to now all existing high-pitch protocols for that particular scanner (Siemens Definition Flash, Forchheim, Germany) are thoracoabdominal CT protocols based on a 32-cm body phantom. By comparison dose radiation reports of standard paranasal sinus protocols for the 16-slice as well as for the 128-dual source CT system operated in the single-source mode are based on the 16-cm head phantom. From the data and CT protocols reported by Shell we conclude that the authors used the 32-cm phantom body protocol for imaging the paranasal sinuses without considering the resulting systematic bias in dose calculation based on the reported dose protocol. To adjust the reported CTDI (32 cm) to the 16-cm phantom the CTDI (32 cm) has to be multiplied by a factor of 2.1 for the Definition Flash (according to the data provided by the manufacturer). Referring to the data by Shell et al. this would result in a CTDI of 5.82 mGy instead of the 2.77 mGy reported for the dual-source protocol. The remaining difference of 1.4 mGy as compared to the CTDI of 7.22 mGy stated for the single-source protocol can be explained by the use of an additional shaped filter which is solely employed for Flash high-pitch body protocols. According to the data provided by the manufacturer this filter accounts for an approximately 20% dose reduction. This recalculation reveals that the reported dose reduction for the dual-source high-pitch approach is not pitch-associated as claimed by the authors. In general, contrary to the dose reduction observed in electrocardiogram (ECG)-gated highpitch spiral CT [2–4], the “SureView principle”, which is employed in non ECG-gated high-pitch spiral CT, will keep the dose constant as it raises the tube current with increasing pitch factor. In conclusion CTDI adjustment to the 16-cm phantom size reveals that the reported dose reduction of the proposed none ECG-gated dual-source high-pitch protocol is lower S. Bulla : P. Blanke :M. Langer :G. Pache Department of Radiology, University Hospital Freiburg, Freiburg, Germany

Simultaneous bilateral contrast injection in computed tomography pulmonary angiography

Background Computed tomography pulmonary angiography (CTPA) has evolved as the gold standard for diagnosing pulmonary embolism. However, subsegmental arteries are often not assessed to do insufficient attenuation. Purpose To evaluate the influence of simultaneous bilateral versus unilateral injection of a fixed amount of contrast media on pulmonary artery opacification and image quality in CTPA. Material and Methods In this institutional review board-approved prospective study, 180 patients (91 women, mean age 61.9 ± 16.5 years) referred for CTPA (100 kV) due to suspected pulmonary embolism were randomized in groups of 45 patients each, with either unilateral (A:4 mL/s; B:6 mL/s) or bilateral (C: 6 mL/s; D: 8 mL/s) (Y-shaped line) injection of 50 mL contrast media. Attenuation was assessed including the subsegmental arteries (4th order). Image quality was evaluated by two readers in consensus using a three-point grading scale (3 = excellent image quality, no artifacts, 1 = non-diagnostic). Results Mean pulmonary artery attenuation was significantly higher with bilateral injection (1st to 3rd order: A: 303.6 ± 8.8HU; B: 371.1 ± 11.0HU vs. C: 443.2 ± 24.1HU; D: 562.3 ± 15.3HU, P < 0.001). Evaluation of subsegmental arteries was feasible for all patients in groups B–D, but only in 36/45 (80%) patients in group A. Subsegmental attenuation was significantly higher with bilateral injection (A: 284.7 ± 12.1HU; B: 367.4 ± 12.1HU vs. C: 494.2 ± 21.5HU; D: 562.3 ± 26.7HU, P < 0.001). Image quality was diagnostic for all patients but best for group C (A: 2.15 ± 0.4; B: 2.14 ± 0.5; C: 2.92 ± 0.3, and D: 2.51 ± 0.5). Conclusion Using the same amount of contrast media, bilateral injection yields higher pulmonary artery attenuation and better image quality than unilateral injection. This technique may improve subsegmental pulmonary artery assessment.