[Value of dual-energy computed tomography for detection of left atrial appendage thrombus]. / Mehrwert der Dual-Energy-Computertomographie zur Detektion von Thromben des linken Vorhofohrs.

OBJECTIVE: Contrast-enhanced computed tomography (CT) is a convenient method to visualize left atrial appendage (LAA) thrombi. We determined whether diagnostic accuracy improves by including dual-energy as compared to transesophageal echocardiography (TEE). Furthermore, the influence of protocol parameters on radiation dose were quantified. METHODS: Patients were assigned to the different CT protocols. All CTs were assessed qualitatively for presence of LAA thrombi and dual-energy CT scans quantitatively for iodine concentration. TEE was assessed qualitatively for the presence of thrombi. RESULTS: Of 32 enrolled patients, 6 had a thrombus in TEE. Qualitative CT assessment yielded 83% sensitivity and 88% specificity. In the 26 patients who underwent dual-energy CT, median iodine concentration was 8.6 mg/cm3 and significantly lower in patients with than without LAA thrombi ; furthermore, it provided value for detecting LAA thrombi (AUC: 0.950 vs 0.867 for combined vs. only qualitative assessment, p = 0.04). The median radiation dose was 1.83 mSv; independently lower in scanning only LAA and with prospective gating , while arrhythmia and dual-energy did not contribute independently. CONCLUSION: CT provides good diagnostic accuracy for detecting LAA thrombi, which can further be improved if iodine density measurements by dual-energy are incorporated. With an optimized protocol, reasonably low radiation dose can be achieved.

In-vitro evaluation of coronary stents and 64-detector-row computed tomography using a newly developed model of coronary artery stenosis.

BACKGROUND: Stent implantation is the predominant therapy for non-surgical myocardial revascularization in patients with coronary artery disease. However, despite substantial advances in multidetector computed tomography (MDCT) coronary imaging, a reliable detection of coronary in-stent restenosis is currently not possible. PURPOSE: To examine the ability of 64-detector-row CT to detect and to grade in-stent stenosis in coronary stents using a newly developed ex-vivo vessel phantom with a realistic CT density pattern, artificial stenosis, and a thorax phantom. MATERIAL AND METHODS: Four different stents (Liberté and Lunar ROX, Boston Scientific; Driver, Medtronic; Multi-Link Vision, Guidant) were examined. The stents were placed on a polymer tube with a diameter of 2.5, 3.0, 3.5, or 4.0 mm. Different degrees of stenosis (0%, 30%, 50%, 70-80%) were created inside the tube. For quantitative analysis, attenuation values were measured in the non-stenotic vessel outside the stent, in the non-stenotic vessel inside the stent, and in the stenotic area inside the stent. The grade of stenosis was visually assessed by two observers. RESULTS: All stents led to artificial reduction of attenuation, the least degree of which was found in the Liberté stent (11.3+/-10.2 HU) and the Multi-Link Vision stent (17.6+/-17.9 HU; P = 0.25). Overall, the non-stenotic vessel was correctly diagnosed in 55.5%, the low-grade stenosis in 58.3%, the intermediate stenosis in 63.8%, and the high-grade stenosis in 80.5%. In the 3.0-, 3.5-, and 4.0-mm vessels, in none of the cases was a non-stenotic or low-grade stenotic vessel misdiagnosed as intermediate or high-grade stenosis. The average deviation from the real grade of stenosis was 0.40 for the Liberté stent, 0.46 for the Lunar ROX stent, 0.45 for the Driver stent, and 0.58 for the Multi-Link Vision stent. CONCLUSION: Our ex-vivo data show that non-stenotic stents and low-grade in-stent stenosis can be reliably differentiated from intermediate and high-grade in-stent stenosis in vessels with a diameter of 3 to 4 mm. With regard to artifacts and the grading of stenoses, the Liberté stent was best suited for CT coronary angiography.

In vitro evaluation of coronary stents and in-stent stenosis using a dynamic cardiac phantom and a 64-detector row CT scanner.

INTRODUCTION: The aim of the study was to examine the ability of a 64-slice MDCT to detect in-stent stenoses in an ex vivo model of coronary stents. METHODS: Five different stents (Liberté, Boston Scientific; Driver, Medtronic; Multi-Link Vision, Guidant; Taxus Express, Boston Scientific; Cypher, Cordis) were examined using a dynamic cardiac phantom. The stents were pulled over a vessel model that consists of a polymer tube with diameters of 3.0, 3.5, and 4.0 mm and four different degrees of stenoses (0%; 30%; 50%; 70-80%). This model was moved with a rate of 60 bpm to mimic cardiac motion. To assess the degree of artificial signal reduction (artificial reduction of attenuation (ARA)) by the different stents, attenuation values were measured in the vessel outside the stent, and in the non-stenotic vessel inside the stent. Furthermore the grade of stenosis was assessed by two clinical observers. RESULTS: Highest ARA was found for the Cypher Stent (35 HU), whereas the Liberté Stent presented the lowest ARA (16 HU). Depending on the stent and the vessel diameter, up to 87.5% of the stenoses were correctly diagnosed. In the 3.0 and 3.5 mm vessels, a nonstenotic or low-grade stenotic vessel was diagnosed as intermediate or high-grade stenosis in 22.5%, whereas in the 4.0 mm vessels, this kind of overestimation did not occur. A 50% stenosis was diagnosed as a 30% stenosis in 30%. On the other hand, high-grade stenoses were underestimated in only 10%. On a four-point scale, the average deviation from the real grade of stenosis was 0.21 for the Liberté stent, 0.54 for the Taxus Express stent, 0.29 for Driver stent, 0.62 for the Multi-Link Vision stent, and 0.37 for the Cypher stent. CONCLUSIONS: In a dynamic cardiac phantom model, high grade stenoses in vessels with a diameter of 4 mm could be reliably detected irrespective of the stent type used in this study. Vice versa, high grade stenoses (> or = 50%) could only be ruled out with certainty in vessels with a diameter of 4 mm. In smaller vessels, the ability to correctly diagnose high-grade stenoses was dependent on the type of stent and the imaging artifacts associated with it.

Noninvasive coronary angiography using 64-detector-row computed tomography in patients with a low to moderate pretest probability of significant coronary artery disease.

PURPOSE: To evaluate the value of 64-detector-row computed tomography for ruling out high-grade coronary stenoses in patients with a low to moderate pretest probability of significant coronary artery disease. MATERIAL AND METHODS: The study included 61 patients with a suspicion of coronary artery disease on the basis of atypical angina or ambiguous findings in noninvasive stress testing and a class II indication for invasive coronary angiography (ICA). All patients were examined by 64-detector-row computed tomography angiography (CTA) and ICA. On a coronary segmental level, the presence of significant (> or = 50% diameter) stenoses was examined. RESULTS: In a total of 915 segments, CTA detected 62 significant stenoses. Thirty-four significant stenoses were confirmed by ICA, whereas 28 stenoses could not be confirmed by ICA. Twenty-two of them showed wall irregularities on ICA, and six were angiographically normal. Accordingly, on a coronary segmental basis, 28 false-positive and 0 false-negative findings resulted in a sensitivity of 100%, a specificity of 96.8%, a positive predictive value of 54.8%, and a negative predictive value of 100%. The diagnostic accuracy was 96.9%. CONCLUSION: Sixty-four-detector-row computed tomography reliably detects significant coronary stenoses in patients with suspected coronary artery disease and appears to be helpful in the selection of patients who need to undergo ICA. Calcified and non-calcified plaques are detected. Grading of stenoses in areas with calcification is difficult. Frequently, stenosis severity is overestimated by 64-detector-row computed tomography.

Assessment of left ventricular function and mass in patients undergoing computed tomography (CT) coronary angiography using 64-detector-row CT: comparison to magnetic resonance imaging.

PURPOSE: To quantify left ventricular function and mass derived from retrospectively ECG-gated 64-detector-row computed tomography coronary angiography data sets in comparison to cine magnetic resonance (MR) imaging as the reference standard. We hypothesized that the administration of beta-blockers prior to multidetector computed tomography (MDCT) coronary angiography has a significant impact on left ventricular functional parameters. MATERIAL AND METHODS: Multiplanar reformations in the short-axis orientation were calculated from axial contrast-enhanced CT images in 21 patients (16 male, five female; age range 41-75 years, mean 64.3+/-6.8 years) referred for CT coronary angiography. Patients whose heart rates exceeded 60 bpm received 5 mg bisoprolol orally 1 hour before the MDCT examination. In case of insufficient heart-rate reduction, up to four vials (20 mg) of metoprolol were injected intravenously. The end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), cardiac output (CO), and left ventricular mass (LVM) of the reformatted images were analyzed compared to volumetric measurements based on continuous short-axis steady-state free-precession cine MR sequences (TR 3 ms, TE 1.5 ms, FA 60 degrees ). RESULTS: On average, each patient received 15.5 mg metoprolol (range 0-20 mg) and 3.85 mg bisoprolol (range 0-5 mg). The mean heart rate was 56+/-5 bpm during CT and 73+/-9 bpm during MRI examination. This difference was statistically significant (P<0.05). Mean EDV and ESV measured on MDCT were significantly higher compared to MR (MDCT vs. MR: EDV 164.2+/-52.5 vs. 144.2+/-46.7 ml, ESV 77.3+/-46.6 vs. 63.8+/-47.3 ml; P<0.05). Mean EF and CO derived from MDCT images were significantly lower compared to MR (MDCT vs. MR: EF 55.4+/-11.8 vs. 59.3+/-15.4%, CO 4822+/-779 vs. 5755+/-1267 ml; P<0.05). Mean SV and LVM were not significantly different between both methods (MDCT vs. MR: SV 86.8+/-18.1 vs. 80.3+/-15.6 ml, P = 0.44; LVM 132.4+/-42.5 vs. 138.7+/-39.1 g, P = 0.31). CONCLUSION: Left ventricular volumes assessed by the newest-generation MDCT scanners are significantly higher compared with MRI, whereas ejection fraction and cardiac output are significantly lower in MDCT. This appears to be a result of the frequent application of beta-blockers prior to MDCT examinations.

[MRI safety aspects and artifacts of atrial septal defect and patent foramen ovale occluders at 1.5 tesla: a phantom study]. / MRT-Sicherheitsaspekte und -Artefakte von Vorhofseptum-Okkludersystemen bei 1,5 Tesla: eine Phantomstudie.

PURPOSE: To investigate the magnetic resonance safety and magnetic resonance artifact intensities of patent foramen ovale and atrial septal occluders in a phantom study. MATERIALS AND METHODS: Seven different commercial occluder models (Amplatzer ASD, Angel Wing ASD, Helex Septal Occluder, Cardia PFO-Star Generation I & III, Sideris Buttoned Device, Starflex ASD) were tested in a 1.5 Tesla whole-body MR scanner. Following a deflection test, the non-magnetic devices were imaged using different MRI pulse sequences including conventional spin echo, spoiled gradient echo as well as fast refocused steady-state pulse sequences (trueFISP) commonly used for cardiac MRI. Additionally, device temperatures were measured in the MR scanner during two imaging protocols (trueFISP, HASTE) with an MR-compatible fiber-optical thermometer. RESULTS: One ferromagnetic device (Sideris Buttoned Device) did not pass the deflection test and was excluded from further experiments. For typical cardiac imaging protocols, the remaining non-ferromagnetic devices showed only minor image artifacts with artifact sizes not exceeding 2 mm next to a strut. Heating was not observed in the devices. CONCLUSION: Non-ferromagnetic occluder models used in this study can safely be imaged with typical cardiac MRI protocols at 1.5 Tesla. The device artifact sizes are small enough to allow anatomical and functional MRI even in the immediate vicinity of the occluders.

[Comparison of contrast-enhanced MR angiography of the aortoiliac vessels using a 1.0 molar contrast agent at 1.0 T with intra-arterial digital subtraction angiography]. / Ergebnisse der kontrastverstärkten MR-Angiographie der aortoiliakalen Gefässe mit einem 1-molaren Kontrastmittel bei 1,0 T: Vergleich zur i. a. DSA.

PURPOSE: To evaluate the diagnostic accuracy of contrast-enhanced MR angiography (CE-MRA) using a 1.0 molar contrast agent at 1.0 T for the diagnosis of abdominal aortic aneurysms and stenoses of renal or iliac arteries in comparison to intraarterial digital subtraction angiography (DSA). MATERIALS AND METHODS: A total of 19 patients with the suspicion of abdominal aortic aneurysm or stenosis of renal or iliac arteries were examined with CE-MRA at 1.0 T. Intra-arterial DSA served as reference in all cases. After test bolus tracking, 10 or 8 ml of the 1.0 molar contrast agent Gadobutrol corresponding to a dose of 0.1 - 0.15 mmol/kg bw were injected and imaging performed using a FLASH-3D sequence. To evaluate the interobserver-variability, the blinded images were analyzed by two radiologists. Besides the rating of overall image quality on a 4-point-scale, the images were evaluated for aneurysms and arteriosclerotic lesions with a stenosis of < 50 % or > 50 % or occlusion. RESULTS: A total of 144 segments were analyzed. The mean value of the CE-MRA image quality was 3.4 on a 4-point-scale. The sensitivity of CE-MRA in depicting relevant pathological findings was 96 % and the specificity 99 %. The positive predictive value was 96 % and the negative predictive value 99 %. Inter-observer variability was low with a kappa value of 0.82. CONCLUSION: CE-MRA using a 1.0 molar contrast agent at 1.0 T enables an excellent diagnosis or exclusion of pathologies of the aortoiliac vessels.

[Entrapment-syndrome of the popliteal artery: morphological and functional diagnosis using MRT inclusive provocation test]. / Entrapment-Syndrom der A. poplitea: Morphologische und funktionelle Diagnose mittels MRT einschliesslich Provokationstest.

A 30-year old man with pain in the right calf was submitted. Typical cardiovascular risk factors were excluded. Contrast enhanced MR-angiography at rest showed occlusion of right popliteal artery with collateral vessels due to an abnormal origin of medial head of gastrocnemius muscle at femoral diaphysis. In contrast to a normal MR-angiography at rest the exercise test detected a lateral deviation and a severe functional stenosis of the left popliteal artery. This was caused by an abnormal medial origin of medial head of gastrocnemius muscle at the inner femoral condylus. The patient has been treated with vascular reconstruction combined with myectomy on the right side and with myectomy only on the left side. These findings showed two different types of popliteal artery entrapment syndrome in one patient. MRI is able to detect the different types especially in different stages. Irreversible damages of popliteal artery in early diagnosed stages may thereby be prevented.

[Cardio-MRT. The multimodal functional analysis of the future]. / Kardio-MRT. Die multimodale Funktionsanalyse der Zukunft.

Since initial reports in the early 1990s cardiac magnetic resonance imaging (CMR) has matured and is likely to become an established method for routine cardiac diagnostics. The development of faster gradient-echo sequences and stronger magnetic fields has led to improved temporal and spatial resolution. Myocardial viability can be examined by morphological and functional analysis. Contrast enhanced MRI (ceMRI), perfusion measurements and regional wall motion analysis are the major diagnostic tools. The ability to image in arbitrary double oblique planes provides comprehensive visualization of the heart. The introduction of the MR navigator technique allowed for free-breathing motion corrected 3D coronary MR angiography with improved spatial resolution. Using this approach proximal and mid parts of the coronary arteries have been visualized. Subsequently, sensitivity and specificity for the detection of significant coronary stenoses has been evaluated in a multicenter trial demonstrating good sensitivity and specificity for the detection of significant left main and three vessel disease. However, specificity for the detection of single vessel disease was relatively low. Improved motion compensation techniques and novel imaging sequences (SSFP) are currently under investigation to further refine this technique. Despite these promising results coronary MR-angiography is not likely to replace conventional coronary angiography especially with regard to in-plane spatial resolution, coronary collateralization and in-stent restenosis. In contrast, coronary MR-angiography can provide useful morphological informations including functional analysis of the coronary vascular bed. The combination of a conventional cathlab with CMR may provide CMR-guided myocardial interventions. With further improvements in the catheter technology, CMR interventions using real-time imaging guidance will allow to take advantage of the excellent soft tissue contrast of CMR and the simultaneous visualization of the pulmonary, aortic and coronary vessels. CMR is advantageous for screening and follow-up examinations, and it offers comprehensive assessment of cardiac morphology and function in one single examination.

[Noonan's syndrome with an unusual combination of hypertrophic cardiomyopathy, congenital bicuspid aortic valve, coarctation of the aorta and hypoplastic aortic arch]. / Noonan-Syndrom mit der ungewöhnlichen Kombination von hypertropher Kardiomyopathie, konnatal bikuspider Aortenklappe und Aortenisthmusstenose mit hypoplastischem Aortenbogen.

Noonan's syndrome is characterized by craniofacial anomalies, i. e. ptosis, webbing of the neck and a deep nuchal hairline, as well as skeletal deformities such as short stature, clinodactyly, pectus carinatum and funnel chest and other organ anomalies, mainly cardiac valve disease, less often testicular retention or kidney malformations. Noonan syndrome presents with aspects similar to Ullrich-Turner syndrome, but can be found in both male and female patients. In about one half of the patients with Noonan's syndrome cardiovascular anomalies occur, mostly anomalies of the right heart (mainly valvular pulmonary stenosis). Aortic stenosis and coarctation of the aorta are rarely seen. We report on a patient with four sequential potentially stenosing and stenosed parts of the proximal systemic circulation: hypertrophic cardiomyopathy, bicuspid aortic valve, coarctation of the aorta and a hypoplastic aortic arch as a part of Noonan's syndrome. This patient presents with a unique combination of anomalies, as he also shows a Madelung like deformity of the wrist.

Late improvement of regional wall motion after the subacute phase of myocardial infarction treated by acute PTCA in a 6-month follow-up.

BACKGROUND: The aim of this follow-up study was to investigate the late effects of acute coronary angioplasty (PTCA) on regional wall motion after the subacute phase of myocardial infarction (MI). METHODS AND RESULTS: Seventeen patients were investigated initially at a median of 11 days and again at 6 months after acute PTCA for myocardial infarction (< 8 hours after onset of symptoms) by cardiac magnetic resonance imaging. Corresponding short-axis slices encompassing the left ventricle (LV) were acquired using a standard cine MR for regional wall motion analysis and using delayed contrast enhanced magnetic resonance imaging (ceMRI) for infarct size quantification. The infarct size was similar in the subacute phase and the 6 month follow-up (20.8 and 21.9%, respectively; n.s.). Regional wall motion improved significantly in the area of hyperenhancement [percentage wall thickening (PWT) 21.9% and 37.9%, p < 0.05] in contrast to remote normal myocardium (46.4% and 38.4%; n.s.). Regional wall motion was significantly poorer in transmural compared with nontransmural MI in the subacute stage, and a late improvement could only be observed in transmural MI. CONCLUSION: Transmural areas of hyperenhancement displayed significant late long-term improvement of regional wall motion after acute PTCA, possibly related to prolonged stunning compared with nontransmural areas.

[Morphologic and functional assessment of vascular abnormalities of the pulmonary vasculature by breath-hold MR techniques]. / Morphologische und funktionelle Evaluation pulmonaler Gefässanomalien mittels schneller MR-Techniken.

PURPOSE: To evaluate breath-hold MR techniques for morphologic and functional assessment of vascular abnormalities of the pulmonary vasculature. PATIENTS AND METHODS: 13 patients aged 11 to 60 years with different vascular abnormalities of the pulmonary vasculature (5 patients with 16 arteriovenous malformations, 8 patients with partial anomalous pulmonary venous return) underwent MR imaging at 1.5 T. For morphological assessment, a contrast-enhanced 3D MR angiography (ce-MRA) was performed after a timing run. Segmented cine- and velocity-encoded GRE sequences were used for delineation of associated cardiac septal defects and for determination of systemic left-to-right or intrapulmonary shunt volumes. Selective intra arterial digital subtraction angiography, cardiac catheterization, and the intraoperative situs served as reference standards. RESULTS: Ce-MRA allowed for detection of all vascular abnormalities and for anatomic characterization of 14/16 arteriovenous malformations. Flow measurements in the feeding arteries allowed for determination of intrapulmonary shunt volumes in 4/5 patients. Flow measurements performed in the pulmonary arteries and the ascending aorta enabled determination of systemic left-to-right shunting in patients with anomalous pulmonary venous return. Cine-sequences clearly depicted associated cardiac septal defects. CONCLUSION: Breath-hold MR techniques allow for morphological and functional characterization of vascular anomalies of the pulmonary vasculature. Therefore, they are the non-invasive method of choice for planning further treatment.

[Evaluation of myocardial perfusion reserve in patients with CAD using contrast-enhanced MRI: a comparison between semiquantitative and quantitative methods]. / Bestimmung der myokardialen Perfusionsreserve bei KHK-Patienten mit der kontrastmittelverstärkten MRT: Ein Vergleich zwischen semiquantitativer und quantitativer Auswertung.

OBJECTIVE: Comparison between two semiquantitative methods and a quantitative evaluation of myocardial blood flow (MBF) for assessment of myocardial perfusion reserve (MPR) in patients with CAD. MATERIAL AND METHODS: 9 patients with coronary stenoses > 50 % were examined with an ECG-gated Saturation Recovery Turbo FLASH sequence by using Gd-DTPA as contrast agent (CA). The entive measurements were performed both during rest and hyperemia induced by adenosine. The up-slopes of the signal-time S(t) curves in the myocardium and left ventricular (LV) cavity were evaluated by a linear fit. MPR was calculated from the original up-slopes of the myocardial S(t) curves and from the up-slopes, which were normalized to the up-slopes of the LV S(t) curves, respectively. For quantification of MBF values, the mathematical model MMID 4 was used and MPR was evaluated from the MBF values. RESULTS: With all tested methods, MPR was reduced in myocardial regions subtended by arteries with stenoses >/= 70 % compared with remote regions. With MMID 4 and the normalized up-slope method, differences between severe ischemic and remote regions were statistically significant. CONCLUSION: The up-slope method with normalization and quantification with MMID 4 are more sensitive methods to differentiate between remote and ischemic myocardium than the up-slope method without normalization.

[Evaluation of left ventricular aneurysms before and after surgery using Cine-MRI]. / Prä- und postoperative Evaluation von linksventrikulären Herzspitzenaneurysmen mittels Cine-MRT.

PURPOSE: To demonstrate the usefulness of cine-MRI for the evaluation of apical left ventricular aneurysms (ALVA) and for prediction of the surgical outcome. MATERIALS AND METHODS: We investigated 28 patients with ALVA, 13 of them additionally after aneurysmectomy at 1.5 T; 15 healthy volunteers served as normal controls. For cine-MRI k-space segmented Fl-2D-GE sequences were used. Analysis comprised the calculation of cardiac volume indices, cardiac function, and percentual myocardial thickening (PMT). For prediction of surgical results we divided left ventricle into an aneurysmatic and a non-aneurysmatic part. The non-aneurysmatic part was assumed as the left ventricle after surgical remodelling. RESULTS: Enddiastolic and endsystolic volume indices (EDVIs and LV-ESVIs) were higher in patients with ALVA (123.7 +/- 30.2 ml/m(2), 94.3 +/- 32.5 ml/m(2), respectively) than in volunteers (79.1 +/- 13.9 ml/m(2), 25.5 +/- 5.1 ml/m(2), respectively) (p < 0.001). Stroke volume index (SVIs), cardiac index (CIs) and ejection fraction (EFs) were significantly lower in patients (30.4 +/- 9.1 vs. 54.2 +/- 0.2 ml/beat/m(2); 2.2 +/- 0.8 vs. 3.9 +/- 0.9 l/min/m(2), 26.0 +/- 9.7 vs. 67.9 +/- 4.5 %, respectively) (p < 0.001). There was a significant decrease of LV-EDVIs and LV-ESVIs (102.8 +/- 30.3 ml/m(2), 66.3 +/- 28.0 ml/m(2), respectively) (p = 0,002, p < 0.001, respectively), no change of SVIs (36.4 +/- 6.0 ml/beat/m(2)) (p > 0.05) and a significant increase of CIs and EFs (3.0 +/- 0.6 l/min/m(2), 37.91 +/- 10.15 %, respectively) (p < 0.001) after surgery. We found a good correlation between the preoperatively calculated (32.6 +/- 10.1 %) and the measured EF after surgery (37.9 +/- 9.8 %) (r = 0.70; p = 0.035). PMT was significantly lower in patients than in volunteers (median 11.9 +/- 10.7 vs. 70.2 +/- 13.9 %; p < 0.001), especially in the aneurysmatic parts of left ventricle (median - 6.8 %; p < 0.001). CONCLUSION: Cine-MRI offers accurate evaluation of ALVA and enables preoperative estimation of left-ventricular volumes after surgery.