[MRI for therapy control in patients with aortic isthmus stenosis]. / MRT zur Therapiekontrolle bei Patienten mit Aortenisthmusstenose.

Aortic isthmus stenosis is the most common congenital aortic anomaly and is often a problem for therapy surveillance. In addition to possible comorbidities (e.g. bicuspid aortic valve) it is accompanied by various middle and long-term complications depending on the primary choice of the therapeutic procedure. Magnetic resonance imaging (MRI) plays an important role for the mostly young patients in the control of the aortic isthmus stenosis and therapy because it is non-invasive and there is no X-ray exposure. Radiologists should be well-informed on the principles of the therapeutic procedure in order to be competent in the interpretation of MRI findings. Due to the continuous development of MRI technology, techniques for functional evaluation (e.g. dynamic MRA, 4D PC flow measurement) are increasingly becoming available in addition to high-resolution MR angiography (MRA), which could predict the risk of possible complications, such as aneurysms. However, in this aspect further studies are necessary. Interventional therapy with stents and stent grafts is often employed for the therapy of possible complications following an operation (aneurysms, restenosis) but because of massive metal artefacts the use of MRI is often sometimes severely limited.

[Cardiac functional analysis with MRI]. / Kardiale Funktionsanalyse mittels MRT.

Cardiovascular diseases (CVD) are among the leading causes of death worldwide. Even in the 21(st) century CVD will still be the most frequent cause of morbidity and mortality. Precise evaluation of cardiac function is therefore mandatory for therapy planning and monitoring. In this article the contribution of MRI-based analysis of cardiac function will be addressed. Nowadays cine-MRI is considered as the standard of reference (SOR) in cardiac functional analysis. ECG-triggered steady-state free precession (SSFP) sequences are mainly used as they stand out due to short acquisition times and excellent contrast between the myocardium and the ventricular cavity. An indispensible requirement for cardiac functional analysis is an exact planning of the examination and based on that the coverage of the whole ventricle in short axial slices. By means of dedicated post-processing software, manual or semi-automatic segmentation of the endocardial and epicardial contours is necessary for functional analysis. In this way end-diastolic volume (EDV), end-systolic volume (ESV) and the ejection fraction (EF) are defined and regional wall motion abnormalities (RWMA) can be detected.

[Late gadolinium enhancement in the diagnostics of ischemic heart disease: technical principles, contrast optimization and clinical application]. / Late-Gadolinium-Enhancement in der Diagnostik der koronaren Herzerkrankung : Technische Grundlagen, Kontrastoptimierung und klinische Anwendung.

BACKGROUND: The purpose of the study was to explore a "dark blood" technique and to compare it with a standard inversion recovery gradient echo (IR GRE) sequence in the visualization of myocardial infarction. PATIENTS AND METHODS: A total of 9 patients were examined with standard IR GRE and a "dark blood" sequence 15 mins after contrast medium application (0.2 mmol/kg body weight gadobenate dimeglumine). Contrast-to-noise ratios (CNR) were calculated for each sequence. RESULTS: The CNR(inf-lvc) was significantly higher in the "dark blood" technique compared to the IR GRE sequence, while the CNR(inf-myo) was significantly lower. CONCLUSIONS: Small subendocardial infarctions may be easier to detect with the "dark blood" technique. However, the standard IR GRE sequence is superior in the demarcation of infarctions in relation to the myocardium and cannot be replaced by the "dark blood" technique.

MRI of respiratory dynamics with 2D steady-state free-precession and 2D gradient echo sequences at 1.5 and 3 Tesla: an observer preference study.

To compare the image quality of dynamic lung MRI with variations of steady-state free-precession (SSFP) and gradient echo (GRE) cine techniques at 1.5 T and 3 T. Ventilated porcine lungs with simulated lesions inside a chest phantom and four healthy human subjects were assessed with SSFP (TR/TE=2.9/1.22 ms; 3 ima/s) and GRE sequences (TR/TE=2.34/0.96 ms; 8 ima/s) as baseline at 1.5 and 3 T. Modified SSFPs were performed with nine to ten images/s (parallel imaging factors 2 and 3). Image quality for representative structures and artifacts was ranked by three observers independently. At 1.5 T, standard SSFP achieved the best image quality with superior spatial resolution and signal, but equal temporal resolution to GRE. SSFP with improved temporal resolution was ranked second best. Further acceleration (PI factor 3) was of no benefit, but increased artifacts. At 3 T, GRE outranged SSFP imaging with high lesion signal intensity, while artifacts on SSFP images increased visibly. At 1.5 T, a modified SSFP with moderate parallel imaging (PI factor 2) was considered the best compromise of temporal and spatial resolution. At 3 T, GRE sequences remain the best choice for dynamic lung MRI.

Dose reduction and image quality in MDCT colonography using tube current modulation.

OBJECTIVE: The purpose of our study was to evaluate the dose reduction potential of combined online (x- and y-axes) and topogram-based (l) X-ray tube current modulation in CT colonography in a screening population. MATERIALS AND METHODS: Eighty asymptomatic individuals underwent CT colonography screening for colon polyps. A 16-MDCT scanner (Somatom Sensation 16) was used. Forty patients were examined at 120 kVp and 120 effective mAs (supine) and 40 effective mAs (prone) using online x- and y-axis tube current modulation. Another 40 patients were scanned using combined x-, y-, and z-axis tube current modulation. Individual patient radiation exposure was determined using the dose-length product. Image noise was determined by Hounsfield unit measurements in the colonic lumen at four anatomic levels. Image quality was rated on a 5-point confidence scale by two independent reviewers. The unpaired Student's t test (for radiation dose, image noise) and Wilcoxon's test (for image quality) were used to test for statistically significant differences between these values. RESULTS: Radiation dose was significantly lower in the patient group scanned with x-, y-, and z-axis tube current modulation than in the group scanned with x- and y-axis tube current modulation (supine: 4.24 vs 6.50 mSv, p < 0.0001; prone: 1.61 vs 2.38 mSv, p < 0.0001). Radiation dose was reduced by 35% (supine) and 33% (prone). No statistically significant difference was seen in overall image noise (supine: 15.9 vs 16.3 H, p = 0.13; prone: 23.5 vs 24.8 H, p = 0.44) or image quality (supine: 4.6 vs 4.5, p = 0.62; prone: 3.5 vs 3.6, p = 0.54). CONCLUSION: Combined x-, y-, and z-axis tube current modulation leads to a significant reduction of radiation exposure in CT colonography without loss of image quality.

Non-invasive coronary bypass graft imaging after multivessel revascularisation.

Non-invasive imaging techniques for the detection of graft patency after multivessel coronary revascularisation may be useful for follow-up after surgery. Forty consecutive asymptomatic patients (38 men, age 59.9+/-1.3 years) who had undergone coronary bypass surgery with at least three grafts were examined by spiral computed tomography or magnetic resonance angiography 24.9+/-0.3 months after surgery, using conventional angiography as reference. In total, 133 grafts (37 internal mammary artery, 96 venous grafts) were analysed. Spiral computed tomography studies were performed with a subsecond scanner; for magnetic resonance angiography, a three-dimensional contrast-enhanced gradient echo technique with ultrashort echo time during breath holding was used. For spiral computed tomography, sensitivities were 76% (internal mammary artery) and 100% (venous graft). This was compared with 100% (internal mammary artery) and 92% (venous graft) assessed by magnetic resonance angiography (P=ns). The positive predictive values were 100% for internal mammary artery and venous graft (spiral computed tomography) and 100% (internal mammary artery), 92% for venous grafts studied by magnetic resonance angiography (P=ns). Both subsecond spiral computed tomography and contrast-enhanced magnetic resonance angiography are highly accurate and relatively non-invasive approaches of assessing coronary graft patency after multivessel revascularisation and have potential for follow-up assessment in the long term.

Assessment of myocardial perfusion using multisection first-pass MRI and color-coded parameter maps: a comparison to 99mTc Sesta MIBI SPECT and systolic myocardial wall thickening analysis.

The most recently reported magnetic resonance first-pass myocardial perfusion studies were restricted to single slice imaging or a data analysis based on interactively placed regions of interest. This study was designed to investigate a new saturation recovery TurboFLASH sequence for multisection myocardial perfusion imaging and to develop a pixel-based software tool to calculate qualitative perfusion parameters. The findings of perfusion imaging were compared to percent systolic myocardial wall thickening analysis and 99mTc Sesta MIBI SPECT. Six healthy volunteers and twelve patients with proven coronary artery disease (CAD) or chronic myocardial infarction were examined. Diagnostic images were acquired for all volunteers and patients with the multisection saturation recovery TurboFLASH sequence. Perfusion defects could be visualized on parameter maps for signal intensity increase over baseline and signal intensity upslope. Sensitivity and specificity were 76.9% and 97.1% for first-pass perfusion MRI, and respectively 84.6% and 94.3% for CINE imaging. All perfusion defects determined with 99mTc Sesta MIBI SPECT were identified by the combined analysis of myocardial perfusion and wall thickening. The presented software demonstrated a pixel-based analysis of first-pass perfusion studies and simplified image interpretation in a clinical setting. The combination of perfusion and wall motion imaging provided complementary information for the treatment of patients suffering from CAD.

[Contrast enhanced MR angiography in the preoperative evaluation of living kidney donors]. / Die kontrastverstärkte MR-Angiographie in der präoperativen Diagnostik von Lebendnierenspendern.

PURPOSE: To compare Gadolinium-enhanced MR angiography with conventional DSA in the preoperative evaluation of living kidney donors. MATERIAL AND METHODS: 27 potential living kidney donors were examined with contrast-enhanced MR angiography after conventional angiography. The MR angiograms were evaluated for the number of renal arteries, the presence of early arterial branching and vascular pathologies by two independent readers. The results were compared with those of selective conventional angiography and intraoperative findings. RESULTS: Conventional angiography detected 14 accessory renal arteries. Reader A detected 13 of 14 accessory arteries with no false positive result (sensitivity 93%, specificity 100%). Reader B detected 11 of 14 accessory vessels with one false positive finding (sensitivity 79%, specificity 98%). Early arterial branching was detected by both readers in 9 of 12 vessels with no false positive result (sensitivity 75%, specificity 100%). None of the patients had additional vascular pathology. DISCUSSION: Gadolinium-enhanced MR angiography is a non-invasive alternative to conventional angiography in the preoperative evaluation of living kidney donors. In order to achieve high accuracy in detecting accessory renal arteries and early arterial branching extensive experience with the method and the specific preoperative needs is required. Selective conventional angiography is still superior in detecting very small accessory vessels and early arterial branching.

[Evaluation of right heart load with spiral CT in patients with acute lung embolism]. / Beurteilung der Rechtsherzbelastung in der Spiral-CT bei Patienten mit akuter Lungenembolie.

PURPOSE: Purpose of this study was to evaluate whether spiral-CT allows judgment of right ventricular failure in patients with acute pulmonary embolism. MATERIALS AND METHODS: 61 patients underwent spiral-CT due to suspicion of acute pulmonary embolism. Patients with pulmonary embolism were divided into subpopulations according to the severity of pulmonary embolism in the CT scan. Cardiac measurements were performed on axial spiral-CT images and compared to those of patients without suspicion of pulmonary embolism or cardiac diseases. RESULTS: In 30 patients spiral-CT revealed acute pulmonary embolism. Significant differences in cardiac measurements in patients with severe and less severe pulmonary embolism were found on comparing the following dimensions: left ventricular width (p = 0.0003), left (p = 0.008) and right (p = 0.009) ventricular cross-sectional area, proportion of right to left ventricular width (p = 0.0003) and proportion of right to left ventricular cross-sectional area (p = 0.0001). The proportion of the cross-sectional areas (r = 0.65) and the proportion of the width (r = 0.60) of both ventricles correlated well with the severity of central pulmonary embolism. CONCLUSION: Besides reliable assessment of pulmonary embolism spiral-CT allows the evaluation of cardiac dimensions for judgment of right ventricular failure.

[Contrast media enhanced magnetic resonance angiography for determining patency of a coronary bypass. A comparison with coronary angiography]. / Kontrastmittelverstärkte Magnetresonanzangiographie zur Uberprüfung der Durchgängigkeit koronarer Bypasses. Vergleich zur Koronarangiographie.

AIM: Assessment of graft patency with current non-invasive MRA techniques is particularly difficult for evaluating internal mammary artery grafts. Our aim is to determine the accuracy of a contrast enhanced MRA technique is assessing graft patency. METHODS: We examined 19 patients with a total of 53 grafts (32 venous/21 arterial), using an ultrafast contrast enhanced 3D gradient-echo technique and compared this with the results of selective angiography. RESULTS: Sensitivity of the contrast enhanced method was 95.2% for venous grafts, 94.4% for IMA grafts and 94.8% overall. Specificity was 85.7% overall, 90.9% for venous and 66.7% for IMA grafts. Positive predictive value was 94.4%. CONCLUSION: Compared with previous studies, visualisation of IMA grafts was improved by using contrast enhanced MRA. In this preliminary study, contrast enhanced MRA proved promising for the assessment of graft patency.

[Multislice CT of the heart: clinical applications]. / TC multicorte (TCMC) cardiaca: aplicaciones clínicas.

Since the introduction of last generation multislice MSCT systems and the development of simultaneous electrocardiographic-tracing image acquisition and retrospective reconstruction techniques into clinical routine, cardiac MSCT has been considered a very useful non-invasive technique for the study of cardiac pathology in the daily clinical practice. One of the main clinical applications of this diagnostic technique is the evaluation of the coronary arteries including detection and quantification of coronary calcium, multislice CT coronary angiography (anatomy, anatomical variants and anomalies of the origin and course), the angiographic evaluation of the patency of aortocoronary by-pass grafts and coronary stents, and plaque characterization. The new reconstruction and postprocessing programs allow to obtain, in addition, parameters of myocardial morphology and contraction and cardiac function. Other clinical applications include the characterization of cardiac masses and the evaluation of the pericardium.

Quantitative assessment of left ventricular function with dual-source CT in comparison to cardiac magnetic resonance imaging: initial findings.

Cardiac magnetic resonance imaging and echocardiography are currently regarded as standard modalities for the quantification of left ventricular volumes and ejection fraction. With the recent introduction of dual-source computedtomography (DSCT), the increased temporal resolution of 83 ms should also improve the assessment of cardiac function in CT. The aim of this study was to evaluate the accuracy of DSCT in the assessment of left ventricular functional parameters with cardiac magnetic resonance imaging (MRI) as standard of reference. Fifteen patients (two female, 13 male; mean age 50.8 +/- 19.2 years) underwent CT and MRI examinations on a DSCT (Somatom Definition; Siemens Medical Solutions, Forchheim, Germany) and a 3.0-Tesla MR scanner (Magnetom Trio; Siemens Medical Solutions), respectively. Multiphase axial CT images were analysed with a semiautomatic region growing algorithms (Syngo Circulation; Siemens Medical Solutions) by two independent blinded observers. In MRI, dynamic cine loops of short axis slices were evaluated with semiautomatic contour detection software (ARGUS; Siemens Medical Solutions) independently by two readers. End-systolic volume (ESV), end-diastolic volume (EDV), ejection fraction (EF) and stroke volume (SV) were determined for both modalities, and correlation coefficient, systematic error, limits of agreement and inter-observer variability were assessed. In DSCT, EDV and ESV were 135.8 +/- 41.9 ml and 54.9 +/- 29.6 ml, respectively, compared with 132.1 +/- 40.8 ml EDV and 57.6 +/- 27.3 ml ESV in MRI. Thus, EDV was overestimated by 3.7 ml (limits of agreement -46.1/+53.6), while ESV was underestimated by 2.6 ml (-36.6/+31.4). Mean EF was 61.6 +/- 12.4% in DSCT and 57.9 +/- 9.0% in MRI, resulting in an overestimation of EF by 3.8% with limits of agreement at -14.7 and +22.2%. Rank correlation rho values were 0.81 for EDV (P = 0.0024), 0.79 for ESV (P = 0.0031) and 0.64 for EF (P = 0.0168). The kappa value of inter-observer variability were amounted to 0.85 for EDV, ESV and EF. DSCT offers the possibility to quantify left ventricular function from coronary CT angiography datasets with sufficient diagnostic accuracy, adding to the value of the modality in a comprehensive cardiac assessment. The observed differences in the measured values may be due to different post-processing methods and physiological reactions to contrast material injection without beta-blocker medication.

[CT angiography of the aorta]. / CT Angiographie der Aorta.

Aortic disease is associated with high morbidity and mortality and thus require an efficient and accurate diagnostic approach, especially in the acute setting. Multislice computed tomography (MSCT) with the option of high-resolution CT angiography (CTA) has emerged as the standard of reference in diagnosis and follow-up of patients with acquired aortic disease. Aortic dissection is the most common aortic emergency, but it remains undiscovered in up to 38% of cases. Sensitivity and specificity of MSCT in the assessment of aortic dissection are greater than 99%. The sensitivity of CT in the detection of inflammatory changes is 83%; its specificity is almost 100%; and its diagnostic accuracy is ca. 94%. This article outlines state-of-the-art principles in diagnostic CT imaging of acquired aortic disease.

Interventional embolization of a giant pulmonary arteriovenous malformation with right-left-shunt associated with hereditary hemorrhagic telangiectasia.

A 46-year old woman experienced an episode of arterial desaturation despite administration of 100% oxygen during anesthetization for an elective laparoscopy. Further evaluation revealed a giant pulmonary arteriovenous malformation (PAVM) with right-left shunt associated with previously undiagnosed hereditary hemorrhagic telangiectasia (HHT, Morbus Osler- Weber-Rendu). The PAVM was treated interventionally with an Amplatzer duct occluder. Transcatheter embolization of the PAVM was well tolerated with symptomatic and hemodynamic improvement. CT scan after six months demonstrated correct position of the duct occluder in the left pulmonary artery with nearly complete occlusion of the feeding vessel.PAVMs are rare direct communications between pulmonary arteries and veins, associated with HHT in the majority of cases and often presenting with dyspnea or major neurological complications due to paradoxic embolism. In this case report, we present a rational and stepwise diagnostic workup for this rare medical condition and show that transcatheter embolization is an appropriate treatment for larger malformations.

[Diagnosis of aortic aneurysm]. / Diagnostik des Aortenaneurysmas.

The aim of the study was to analyze the use and indication of 3 imaging modalities (CT, DSA and MRI) for patients with suspicion of aortic aneurysm. During 18 months 383 patients with suspicion of aortic aneurysm were examined with CT (SCT/MSCT), 17 with digital subtraction angiography (DSA), and 15 with MRI. Diagnostic DSA was performed in 7 cases for planning endoluminal therapy, in 7 cases because of unclear findings in CT and in 4 cases because of dissection of the aorta. MRI was performed in 12 cases with previously performed CT and in 3 cases as the only imaging modality because of intolerance to iodinated contrast material. CT is a well established and in most cases sufficient method for the examination of patients with the suspicion of aortic aneurysm. CT is widely available, and provides good image quality and a high diagnostic accuracy. Additional examinations with DSA or MRI are necessary in less than 5% of the patients.

[Reconstruction methods in postprocessing of CT- and MR-angiography of the aorta]. / Rekonstruktionsverfahren bei der Nachverarbeitung von CT- und MR-Angiographie der Aorta.

The aim of the study was to investigate the use of 2D and 3D reconstructions in examinations of the aorta with CT and MRI. Postprocessing of 5 data sets including 2D MPR reconstructions, 3D MIP reconstructions and 3D volume rendering reconstructions acquired with contrast enhanced CTA and 5 data sets acquired with contrast enhanced MRA were performed. The luminal diameter, the length of the aneurysm and the detection of dissection was assessed for the reconstructions and the source images. Aneurysms and dissections of the aorta were correctly identified on source images. 2D MPR reconstructions and source images allow for a clear and easy image analysis including cases with high signal intensity or density of surrounding tissue and complex anatomical structures. The diameter and length of pathological findings can be determined correctly wit 2D MPR reconstructions, even when the vessel orientation is not exactly inplane or throughplane in relation to the source images. MIP reconstructions are suitable for contrast enhanced MRA data sets with high C/N ratio and volume rendering reconstructions are suitable for contrast enhanced CTA data sets, where calcifications and bone have also high density. For 3D visualization of large volumes MIP reconstructions are the method of choice for MRA and volume rendering reconstructions for CTA, respectively. In addition, 2D MPR can be necessary to determine the diameter and length of pathological findings.

Minimally invasive extirpation of a left-ventricular myxoma.

As myxomas usually are benign neoplasms a minimally invasive technique would be an interesting alternative for their extirpation because the surgical trauma is reduced. In one male patient with a diagnosed left-ventricular myxoma minimally invasive surgery was carried out using the Port-Access method. 2D echocardiography, EBT, and MRI were performed preoperatively to obtain exact information about topography, calcifications, and malignity. Minimally invasive extirpation was successful and the mitral valve could be preserved. Histopathological examination revealed a cardiac myxoma extirpated in toto. At one-year follow-up there was no recurrence of the tumor.

[Control of the patency of coronary artery bypasses with contrast enhanced magnetic resonance angiography]. / Kontrolle der Offenheit von Koronarbypässen mittels kontrastverstärkter Magnetresonanzangiographie.

Contrast-enhanced 3D magnetic resonance angiography (MRA) has the potential for being a reliable method for CABG visualization and CABG patency determination in early postoperative period. 3D reconstruction was helpful in delineating CABG course and in several cases in detecting stenosis of coronary arteries. Compared to coronary angiography MRA is a non-invasive examination technique without iodine contrast medium and X-ray and is practicable in 30 min with minimal risk and low costs.