Oliver Klass

Multienergy Photon-counting K-edge Imaging: Potential for Improved Luminal Depiction in Vascular Imaging

The purpose of this study was to investigate whether spectral computed tomography (CT) has the potential to improve luminal depiction by differentiating among intravascular gadolinium-based contrast agent, calcified plaque, and stent material by using the characteristic k edge of gadolinium. A preclinical spectral CT scanner with a photon-counting detector and six energy threshold levels was used to scan a phantom vessel. A partially occluded stent was simulated by using a calcified plaque isoattenuated to a surrounding gadolinium chelate solution. The reconstructed images showed an effective isolation of the gadolinium with subsequent clear depiction of the perfused vessel lumen. The calcified plaque and the stent material are suppressed.

Diffusion-weighted MR imaging in comparison to integrated [18F]-FDG PET/CT for N-staging in patients with lung cancer

PURPOSE The purpose of this study was to prospectively determine the diagnostic accuracy of diffusion-weighted imaging (DWI) using MRI in the staging of thoracic lymph nodes in patients with lung cancer, and to compare the performance to that of PET/CT. PATIENTS AND METHOD 20 consecutive patients (pts) with histologically proven lung cancer were included in this study. In all pts FDG-PET/CT was routinely performed to stage lung carcinoma. Additionally, MRI (1.5T) was performed including native T1w, T1w post contrast medium, T2w, and DWI sequences. Regarding the N stage based on the results of the PET/CT there were 5 patients with N0, 3 patients with N1, 5 patients with N2 and 7 patients with N3. Image analysis was performed by two radiologists (R1 and R2), respectively. The reviewers had to chose between 1 (at least one lymph node within a station is malignant) or 0 (no lymph nodes suspicious for malignancy). First the T1 post contrast sequence was analyzed. In a second step the DWI sequence (b=800) was analyzed. Both steps were performed in a blinded fashion. RESULTS MR imaging with or without DWI only agreed with the results of the PET/CT regarding the N stage in 80% of the patients-15% were understaged and 5% overstaged. There was excellent interobserver agreement; the N-staging result only differed in 1 patient for DWI, resulting in correlation coefficients of 0.98 for DWI and 1.0 for MRI. Compared to PET-CT MRI overstaged one and understaged 4 patients, while DWI overstaged one and understaged 3 patients. This resulted in correlation coefficients of 0.814 (R1 and R2) for MRI and 0.815 (R1) and 0.804 (R2) for DWI. Regarding the ADC values there were no significant differences between ipsilateral hilar (1.03 mm(2)/s ± 0.13), subcarinal (0.96 mm(2)/s±0.24), ipsilateral mediastinal (1.0mm(2)/s ± 0.18), contralateral mediastinal (0.93 mm(2)/s ± 0.23) and supraclavicular (0.9 mm(2)/s ± 0.23) lymph nodes. CONCLUSION Diffusion-weighted imaging does not show a clear advantage over conventional MR protocols in the N-staging of lung cancer. MRI with or without DWI shows a moderately correlation with PET/CT with a tendency for understaging.

Coronary plaque imaging with 256-slice multidetector computed tomography: interobserver variability of volumetric lesion parameters with semiautomatic plaque analysis software

The purpose of this study was to evaluate the potential clinical value of coronary plaque imaging with a new generation CT scanner and the interobserver variability of coronary plaque assessment with a new semiautomatic plaque analysis application. Thirty-five isolated plaques of the left anterior descending coronary artery from 35 patients were evaluated with a new semiautomatic plaque analysis application. All patients were scanned with a 256-slice MDCT scanner (Brilliance iCT, Philips Healthcare, Cleveland OH, USA). Two independent observers evaluated lesion volume, maximum plaque burden, lesion CT number mean and standard deviation, and relative lesion composition. We found 10 noncalcified, 16 mixed, and 9 calcified lesions in our study cohort. Relative interobserver bias and variability for lesion volume were −37%, −13%, −49%, −44% and 28%, 16%, 37%, and 90% for all, noncalcified, mixed, and calcified lesions, respectively. Absolute interobserver bias and variability for relative lesion composition were 1.2%, 0.5%, 1.5%, 1.3% and 3.3%, 4.5%, 7.0%, and 4.4% for all, noncalcified, mixed, and calcified lesions, respectively. While mixed and calcified lesions demonstrated a high degree of lesion volume interobserver variability, noncalcified lesions had a lower degree of lesion volume interobserver variability. In addition, relative noncalcified lesion composition had a very low interobserver variability. Therefore, there may a role for MDCT in serial noncalcified plaque assessment with semiautomatic analysis software.

Quantification of aortic valve area at 256-slice computed tomography: Comparison with transesophageal echocardiography and cardiac catheterization in subjects with high-grade aortic valve stenosis prior to percutaneous valve replacement

PURPOSE The purpose of this study was to compare planimetric aortic valve area (AVA) measurements from 256-slice CT to those derived from transesophageal echocardiography (TEE) and cardiac catheterization in high-risk subjects with known high-grade calcified aortic stenosis. METHODS AND MATERIALS The study included 26 subjects (10 males, mean age: 79±6; range, 61-88 years). All subjects were clinically referred for aortic valve imaging prior to percutaneous aortic valve replacement from April 2008 to March 2009. Two radiologists, blinded to the results of TEE and cardiac catheterization, independently selected the systolic cardiac phase of maximum aortic valve area and independently performed manual CT AVA planimetry for all subjects. Repeated AVA measurements were made to establish CT intra- and interobserver repeatability. In addition, the image quality of the aortic valve was rated by both observers. Aortic valve calcification was also quantified. RESULTS All 26 subjects had a high-grade aortic valve stenosis (systolic opening area <1.0 cm(2)) via CT-based planimetry, with a mean AVA of 0.62±0.18. In four subjects, TEE planimetry was precluded due to severe aortic valve calcification, but CT-planimetry was successfully performed with a mean AVA of 0.46±0.23 cm(2). Mean aortic valve calcium mass score was 563.8±526.2 mg. Aortic valve area by CT was not correlated with aortic valve calcium mass score. A bias and limits of agreement among CT and TEE, CT and cardiac catheterization, and TEE and cardiac catheterization were -0.07 [-0.37 to 0.24], 0.03 [-0.49 to 0.55], 0.12 [-0.39 to 0.63]cm(2), respectively. Differences in AVA among CT and TEE or cardiac catheterization did not differ systematically over the range of measurements and were not correlated with aortic valve calcium mass score. CONCLUSION Planimetric aortic valve area measurements from 256-slice CT agree well with those derived from TEE and cardiac catheterization in high-risk subjects with known high-grade calcified aortic stenosis.

Evaluation of Accordance of Magnetic Resonance Volumetric and Flow Measurements in Determining Ventricular Stroke Volume in Cardiac Patients

Background: Cardiovascular magnetic resonance imaging (CMR) has become an established noninvasive method for evaluating ventricular function utilizing three-dimensional volumetry. Postprocessing of volumetric measurements is still tedious and time consuming. Stroke volumes obtained by flow quantification across the aortic root or pulmonary trunk could be utilized to increase both speed of workflow and accuracy. Purpose: To assess accuracy of stroke volume quantification using MR volumetric imaging compared to flow quantification in patients with various cardiac diseases. Strategies for the augmentation of accuracy in clinical routine were deduced. Material and Methods: 78 patients with various cardiac diseases—excluding intra- or extracardiac shunts, regurgitant valvular defects, or heart rhythm disturbance—underwent cardiac function analysis with flow measurements across the aortic root and cine imaging of the left ventricle. Forty-six patients additionally underwent flow measurements in the pulmonary trunk and cine imaging of the right ventricle. Results: Left ventricular stroke volume (LVSV) and stroke volume of the aortic root (SVAo) correlated with r=0.97, and Bland-Altman analysis showed a mean difference of 0.11 ml and a standard error of estimation (SEE) of 4.31 ml. Ninety-two percent of the data were within the 95% limits of agreement. Right ventricular stroke volume (RVSV) and stroke volume of the pulmonary trunk (SVP) correlated with a factor of r=0.86, and mean difference in the Bland-Altman analysis was fixed at –2.62 ml (SEE 8.47 ml). For RVSV and SVP, we calculated r=0.82, and Bland-Altman analysis revealed a mean difference of 1.27 ml (SEE 9.89 ml). LVSV and RVSV correlated closely, with r=0.91 and a mean difference of 2.79 ml (SEE 7.17 ml). SVAo and SVP correlated with r=0.95 and a mean difference of 0.50 ml (SEE 5.56 ml). Conclusion: Flow quantification can be used as a guidance tool, providing accurate and reproducible stroke volumes of both ventricles. Combining both offers a highly accurate tool to gauge ventricular function in a routine clinical setting, increasing workflow speed.

Influence of different self-expanding stent-graft types on remodeling of the aortic neck after endovascular aneurysm repair.

Purpose: To evaluate aortic neck changes, specifically aortic neck dilatation, over a 10-year period in patients undergoing endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm. Methods: All patients who underwent elective EVAR at our institution from 1998 through 2007 were analyzed retrospectively. Among these, 103 patients (96 men; mean age 71 years, range 35–84) who received the 3 most frequently implanted self-expanding stent-grafts (35 Talent, 39 Excluder, and 29 Zenith) and had a minimum 3-month imaging follow-up at our department were selected for this study. All diameters were measured perpendicular to the centerline of flow on computed tomography; baseline data were derived from the first postoperative scan. Stent-graft migration was measured from the lowermost renal artery to the first strut of the stent-graft. Based on intra- and interobserver error measurements, a minimum change of 2 mm defined aortic neck dilatation. Results: During a mean follow-up of 39.4 months (range 3–108.8), infrarenal aortic neck dilatation (>2 mm) was found in 10 patients (28.6%, 95% CI 14.6–46.3) in the Talent group, 4 (10.3%, 95% CI 2.9–24.2) in the Excluder group, and 9 (31.0%, 95% CI 15.3–50.8) in the Zenith group (p = 0.299). In 7 (31%) of the 23 patients with neck dilatation, additional therapy was necessary. Suprarenal changes were found in 6 patients (17.1%, 95% CI 6.6–33.6), 8 patients (20.5%, 95% CI 9.3–36.5), and 5 patients (17.2%, 95% CI 5.8–35.8), respectively (p=0.218). Stent-graft migration >2 mm was seen in 2 (1.9%) of the 103 patients in follow-up. The overall endoleak rates were 37.1% for Talent, 30.8% for Excluder, and 37.9% for Zenith (p>0.05). Two patients were converted to open repair owing to Talent stent-graft migration and persistent type I leak (Zenith). The overall reintervention rate was 13.6% (13/103). Conclusion: Only a small number of the patients treated with self-expanding stent-grafts show notable infrarenal aortic neck dilatation, which does not appear to be related to the stent-graft model. Almost all cases of aortic neck dilatation exceeded the percentage of oversizing; less than a third of patients with aortic neck dilatation required therapy.

Multidetector computed tomography coronary angiography: sublingual nitroglycerine improves image quality significantly because of peripheral coronary vasodilatation.

Purpose: In this study, we investigated the influence of sublingual nitroglycerine (NTG) on the peripheral diameter, intraluminal contrast agent density, and image quality of coronary arteries during computed tomography coronary angiography (CTCA). Materials and Methods: Thirty patients with sublingual NTG application were matched to 30 patients without NTG. The diameters of the left anterior descending coronary artery (LAD), the left circumflex coronary artery and the right coronary artery were measured at 1-, 4-, and 8-cm length of each vessel as well as the intraluminal contrast agent density along the LAD. Vessel diameters and contrast attenuation at 4 and 8 cm were referenced against the values at 1 cm and processed as percentage reduction. Image quality of the posterior descending artery was assessed subjectively by 2 independent observers. Results: The percentage of peripheral vessel diameter reduction and the peripheral attenuation of contrast agent density for all measured coronary arteries was significantly smaller in the group with NTG administration. The image quality of the posterior descending artery was significantly higher in the group with NTG. Conclusions: Sublingual administration of NTG before CTCA results in improved diagnostic image quality because of a significant dilatation and improved intraluminal contrast agent density of the peripheral vessels.

Left Ventricular Bronchogenic Cyst

In a 42-year-old woman presenting with intermittent atypical angina, transthoracic echocardiography revealed a tumor of the left posterolateral ventricular wall (Movie I in the online-only Data Supplement and Figure 1). The patient was referred for cardiovascular magnetic resonance imaging. Left ventricular ejection fraction was calculated at 72%. Cardiovascular magnetic resonance revealed an irregular, intramyocardial cystic lesion that measured 2×3 cm. The lesion did not show any contrast enhancement and was located in the posterolateral wall of the left …

Coronary MR Imaging : Navigator Echo Biofeedback Increases Navigator Efficiency-Initial Experience

RATIONALE AND OBJECTIVES The aim of this study was to investigate whether a respiratory biofeedback system could increase navigator efficiency and maintain image quality compared to conventional respiratory-gated magnetic resonance coronary angiography (MRCA). MATERIALS AND METHODS Eighteen healthy volunteers underwent MRCA using three different respiratory-gating protocols. A conventional expiratory free-breathing (FB) sequence was compared to two approaches using navigator echo biofeedback (NEB), a midinspiratory approach (NEBin) and an expiratory approach (NEBex). Navigator data reflecting the position of the diaphragm relative to a 3-mm gating window were made available to the subject using a video projector in combination with a Plexiglas screen and mirror goggles. Image quality was graded by two radiologists in consensus using a visual score ranging from 1 (not visible) to 4 (excellent vessel depiction). RESULTS The NEB approaches improved navigator efficiency (71.1% with NEBex and 68.0% with NEBin vs 42.2% with FB), thus reducing total imaging time. This difference was statistically significant (P(NEBin)=.007; P(NEBex)=.001). Image quality in the NEBex group was comparable to that in the FB group (median score, 2.44 vs 2.52), but it proved to be significantly lower (median score, 1.94 vs 2.52) for the right coronary artery and the left anterior descending coronary artery in the NEBin group. CONCLUSION NEB maintains image quality and significantly increases navigator efficiency, thereby decreasing total imaging time by about 40% compared to a conventional FB acquisition strategy.

Technical reportCoronary MR Imaging: Navigator Echo Biofeedback Increases Navigator Efficiency—Initial Experience

RATIONALE AND OBJECTIVES The aim of this study was to investigate whether a respiratory biofeedback system could increase navigator efficiency and maintain image quality compared to conventional respiratory-gated magnetic resonance coronary angiography (MRCA). MATERIALS AND METHODS Eighteen healthy volunteers underwent MRCA using three different respiratory-gating protocols. A conventional expiratory free-breathing (FB) sequence was compared to two approaches using navigator echo biofeedback (NEB), a midinspiratory approach (NEBin) and an expiratory approach (NEBex). Navigator data reflecting the position of the diaphragm relative to a 3-mm gating window were made available to the subject using a video projector in combination with a Plexiglas screen and mirror goggles. Image quality was graded by two radiologists in consensus using a visual score ranging from 1 (not visible) to 4 (excellent vessel depiction). RESULTS The NEB approaches improved navigator efficiency (71.1% with NEBex and 68.0% with NEBin vs 42.2% with FB), thus reducing total imaging time. This difference was statistically significant (P(NEBin)=.007; P(NEBex)=.001). Image quality in the NEBex group was comparable to that in the FB group (median score, 2.44 vs 2.52), but it proved to be significantly lower (median score, 1.94 vs 2.52) for the right coronary artery and the left anterior descending coronary artery in the NEBin group. CONCLUSION NEB maintains image quality and significantly increases navigator efficiency, thereby decreasing total imaging time by about 40% compared to a conventional FB acquisition strategy.