Friedrich Knollmann

Reduction aortoplasty for dilatation of the ascending aorta in patients with bicuspid aortic valve

BACKGROUND Individuals with bicuspid aortic valve tend to develop a dilatation of the ascending aorta. It is controversial whether the dilated ascending aorta should be replaced with a tube graft or whether the diameter of the aorta should be reduced by reduction aortoplasty. Furthermore, it is unclear whether an external prosthetic support of the reduction aortoplasty is necessary. The aim of this study is to analyze the results of reduction aortoplasty with and without external prosthetic support. METHODS Between 1985 and 1999, a total of 115 patients with bicuspid aortic valve and dilatation of the ascending aorta underwent reduction aortoplasty in combination with other types of open-heart procedure at our institution. The diameter of the ascending aorta was measured before and early after surgery and then later between 12 and 144 months (mean 40 months) postoperatively using echocardiography and computed tomography. RESULTS The reduction aortoplasty decreased the internal diameter of the aorta from 48.7+/-5.1 mm preoperatively to 36.9+/-3.6 mm early after surgery (p = 0.0001). During follow-up, there was no increase of the aortic diameter either in patients with external prosthetic support or in 97 of 106 patients without external prosthetic support. The diameter increased only in 9 (8.5%) of 106 patients without external aortic support by 4 to 8 mm. In patients with postoperative diameter increase, the aortic diameter after operation had been higher than in patients without a postoperative increase of the aortic diameter (41.4+/-3.1 mm vs 36.6+/-3.4 mm; p < 0.0001). CONCLUSIONS Reduction aortoplasty showed good long-term results in patients with bicuspid aortic valve and dilatation of the ascending aorta. Redilation of the aorta occurred only in patients with a suboptimal diameter reduction.

A Computational Geometry Approach to Automated Pulmonary Fissure Segmentation in CT Examinations

Identification of pulmonary fissures, which form the boundaries between the lobes in the lungs, may be useful during clinical interpretation of computed tomography (CT) examinations to assess the early presence and characterization of manifestation of several lung diseases. Motivated by the unique nature of the surface shape of pulmonary fissures in 3-D space, we developed a new automated scheme using computational geometry methods to detect and segment fissures depicted on CT images. After a geometric modeling of the lung volume using the marching cubes algorithm, Laplacian smoothing is applied iteratively to enhance pulmonary fissures by depressing nonfissure structures while smoothing the surfaces of lung fissures. Next, an extended Gaussian image based procedure is used to locate the fissures in a statistical manner that approximates the fissures using a set of plane ldquopatchesrdquo. This approach has several advantages such as independence of anatomic knowledge of the lung structure except the surface shape of fissures, limited sensitivity to other lung structures, and ease of implementation. The scheme performance was evaluated by two experienced thoracic radiologists using a set of 100 images (slices) randomly selected from 10 screening CT examinations. In this preliminary evaluation 98.7% and 94.9% of scheme segmented fissure voxels are within 2 mm of the fissures marked independently by two radiologists in the testing image dataset. Using the scheme detected fissures as reference, 89.4% and 90.1% of manually marked fissure points have distance les2 mm to the reference suggesting a possible under-segmentation of the scheme. The case-based root mean square (rms) distances (ldquoerrorsrdquo) between our scheme and the radiologist ranged from 1.48plusmn0.92 to 2.04plusmn3.88 mm. The discrepancy of fissure detection results between the automated scheme and either radiologist is smaller in this dataset than the interreader variability.

Pulmonary Lobe Segmentation in CT Examinations Using Implicit Surface Fitting

Lobe identification in computed tomography (CT) examinations is often an important consideration during the diagnostic process as well as during treatment planning because of their relative independence of each other in terms of anatomy and function. In this paper, we present a new automated scheme for segmenting lung lobes depicted on 3-D CT examinations. The unique characteristic of this scheme is the representation of fissures in the form of implicit functions using radial basis functions (RBFs), capable of seamlessly interpolating ldquoholesrdquo in the detected fissures and smoothly extrapolating the fissure surfaces to the lung boundaries resulting in a ldquonaturalrdquo segmentation of lung lobes. A previously developed statistically based approach is used to detect pulmonary fissures and the constraint points for implicit surface fitting are selected from detected fissure surfaces in a greedy manner to improve fitting efficiency. In a preliminary assessment study, lobe segmentation results of 65 chest CT examinations, five of which were reconstructed with three section thicknesses of 0.625 mm, 1.25 mm, and 2.5 mm, were subjectively and independently evaluated by two experienced chest radiologists using a five category rating scale (i.e., excellent, good, fair, poor, and unacceptable). Thirty-three of 65 examinations (50.8%) with a section thickness of 0.625 mm were rated as either ldquoexcellentrdquo or ldquogoodrdquo by both radiologists and only one case (1.5%) was rated by both radiologists as ldquopoorrdquo or ldquounacceptable.rdquo Comparable performance was obtained with a slice thickness of 1.25 mm, but substantial performance deterioration occurred in examinations with a section thickness of 2.5 mm. The advantages of this scheme are its full automation, relative insensitivity to fissure completeness, and ease of implementation.

Causes of Death of Patients With Lung Cancer

CONTEXT The causes of death for patients with lung cancer are inadequately described. OBJECTIVE To categorize the immediate and contributing causes of death for patients with lung cancer. DESIGN The autopsies from 100 patients who died of lung cancer between 1990 and February 2011 were analyzed. RESULTS Tumor burden was judged the immediate cause of death in 30 cases, including 26 cases of extensive metastases and 4 cases with wholly or primarily lung tumor burden (causing respiratory failure). Infection was the immediate cause of death for 20 patients, including 8 with sepsis and 12 with pneumonia. Complications of metastatic disease were the immediate causes of death in 18 cases, including 6 cases of hemopericardium from pericardial metastases, 3 from myocardial metastases, 3 from liver metastases, and 3 from brain metastases. Other immediate causes of death were pulmonary hemorrhage (12 cases), pulmonary embolism (10 cases, 2 tumor emboli), and pulmonary diffuse alveolar damage (7 cases). From a functional (pathophysiologic) perspective, respiratory failure could be regarded as the immediate cause of death (or mechanism of death) in 38 cases, usually because of a combination of lung conditions, including emphysema, airway obstruction, pneumonia, hemorrhage, embolism, resection, and lung injury in addition to the tumor. For 94 of the 100 patients, there were contributing causes of death, with an average of 2.5 contributing causes and up to 6 contributing causes of death. CONCLUSIONS The numerous and complex ways lung cancer kills patients pose a challenge for efforts to extend and improve their lives.

Characterization of Atherosclerotic Plaques in Human Coronary Arteries With 16-Slice Multidetector Row Computed Tomography by Analysis of Attenuation Profiles

RATIONALE AND OBJECTIVES We investigated if 16-slice multidetector row computed tomography (MDCT) allows correct classification of coronary plaques into calcified or noncalcified and further subclassification of noncalcified plaques into either lipid-rich with a necrotic core or fibrous. MATERIALS AND METHODS Coronary arteries of 30 isolated hearts were filled postmortem with a contrast medium and scanned with a 16-slice MDCT imager (Light Speed 16 pro, GEMS, Milwaukee, WI). Imaging parameters: collimation 16 x 0.625 mm, pitch 0.325, tube voltage 120 kV, tube current 250 mA, and gantry rotation time 500 milliseconds. The images were reformatted perpendicular to the axis of the coronary arteries (AW 4.2 software, GEMS) and analyzed by establishing attenuation profiles of the coronary cross sections (ImageJ 1.33n software, NIH, Bethesda, MD). Results were compared with the correlating histopathologic sections of the arteries. RESULTS Analysis of 195 CT cross-sections showed a sensitivity and specificity for the correct classification of calcified plaques of 100% and 97.3% and for noncalcified plaques of 80.8% and 95.1%, respectively. The attenuation of epicardial fat ranged from -119 Hounsfield units (HU) to 23 HU (median -71 HU), and from 93 HU to 625 HU (308 HU) for the contrast medium. Calcified plaques showed an attenuation between 333 HU and 1944 HU (1,089 HU), noncalcified plaques between 26 HU and 124 HU (52 HU). Further subclassification of noncalcified plaques showed attenuation values between 26 HU and 67 HU (median 44 HU) for lipid-rich plaques with a necrotic core and from 37 HU to 124 HU (median 67 HU) for fibrous plaques. CONCLUSIONS Coronary atherosclerotic plaques can be reliably identified and classified as either calcified or noncalcified by 16-slice MDCT in postmortem studies. Further differentiation of noncalcified plaques in either lipid-rich or fibrous is not reliably feasible because of substantial overlap of the attenuation.

The aortic root: Comparison of measurements from ECG-gated CT angiography with transthoracic echocardiography

Purpose The purpose of this study was to compare the measurements of the aortic root obtained from electrocardiographically (ECG)-gated computed tomography (CT) angiography (CTA) to the measurements obtained from transthoracic echocardiography (TTE). Materials and Methods This was a retrospective study in a patient population scanned at our institution between December 2005 and January 2007 with retrospectively ECG-gated CTA. ECG-gated CTA was performed with a 64-section helical CT scanner (Light speed, VCT, GE, Milwaukee, WI). Sixty-eight patients; 51 men and 17 women were included in this study. Aortic root diameters were measured by using double oblique reconstruction from axial source images. The TTE measurements of the aortic root were obtained from the reports that were performed within 2 months of CTA. Results The average aortic root diameter measured by TTE was 33±4.1 mm; on CTA it was 36.9±3.8 mm. The median difference between the 2 measurements was 3.9 mm which was significant (P<0.0001). In patients whose aortic root measurements with CTA were normal, the TTE measurements were also normal. However, in the group of patients with dilated aortic roots by CTA, TTE measurements were significantly lower and many were normal. In the group of patients with dilated aortic root by TTE, the CTA measurements of the aortic root were similarly increased. Conclusions Retrospective comparison of TTE and CTA measurements of the aortic root reveal that TTE measurements are substantially lower or even normal in patients found to have dilated aortic root by CTA.

Implantation of MicroMed DeBakey VAD through left thoracotomy after previous median sternotomy operations

A left lateral thoracotomy was used for implantation of the continuous-flow MicroMed DeBakey left ventricular assist device in 12 patients with previous heart operations through a median sternotomy. This approach avoids reopening the chest through a median sternotomy and reduces the risk of bleeding and subsequent complications.

The biocompound method in coronary artery bypass operations: surgical technique and 3-year patency

BACKGROUND Complete arterial revascularization may be unsafe in patients with a high operative risk. In patients with varicose ectatic veins, the biocompound technique, which uses unsuitable autologous veins, enables the surgeon to influence the bypass graft wall stress levels and diameter. This report summarizes the 3-year patency of 53 patients, the survival rate of 200 patients, and operative technical considerations. METHODS Biocompound grafts were used for aortocoronary bypass in 200 patients who were considered inappropriate subjects for complete arterial revascularization and who had unsuitable saphenous veins. RESULTS The mortality rate (30 days) of 200 patients was 3.5%. The 3-year survival rate was 88.5%. The patency rate of the left internal thoracic artery (LITA) after 3 years was 97.3%, of the native vein was 68.7%, and of the biocompound graft was 68.3%. The LITA showed a superior patency rate (p = < 0.05). CONCLUSIONS The LITA is the first choice in coronary bypass operation. The biocompound technique is a reliable method to achieve complete revascularization in patients with a lack of suitable saphenous veins.

Einsatz moderner Schnittbildverfahren in der Diagnostik von Herzklappenerkrankungen

Exact visualization of valve morphology seems to be possible with the cross-sectional imaging modalities, magnetic resonance imaging (MRI) and the recently introduced technique of multidetector computed tomography (MDCT). These techniques are used, if other non-invasive imaging modalities, like echocardiography, fail or provide only insufficient information. This commonly occurs in the assessment of right ventricular valves. Quantification of valve stenosis is possible by calculating valve orifice area, which can be performed with MRI and MDCT. An estimation of the instantaneous peak gradient can only be achieved by MR flow measurements. MR flow measurement is a reliable method to quantify the degree of mild to moderate stenoses. Quantification of valve regurgitation is possible by measurement of the regurgitation fraction with MR flow measurements as well as with MR volumetry/CT volumetry. But only the MR flow measurement is suitable for the quantification of valve regurgitation in patients with multiple valves involved or cardiac shunting. MRI and probably MDCT are the most reliable methods in the evaluation of ventricular volumes and therefore suitable for the follow-up in patients with valvular heart disease, because changes in volumes are important for therapeutic decisions in these patients. The crucial advantages of MRI compared to CT in the diagnostic of valvular heart diseases however are the absence of radiation exposure, the possibility of quantitative evaluation of valves function using flow measurements and the higher temporal resolution as compared to MDCT.Exact visualization of valve morphology seems to be possible with the cross-sectional imaging modalities, magnetic resonance imaging (MRI) and the recently introduced technique of multidetector computed tomography (MDCT). These techniques are used, if other non-invasive imaging modalities, like echocardiography, fail or provide only insufficient information. This commonly occurs in the assessment of right ventricular valves. Quantification of valve stenosis is possible by calculating valve orifice area, which can be performed with MRI and MDCT. An estimation of the instantaneous peak gradient can only be achieved by MR flow measurements. MR flow measurement is a reliable method to quantify the degree of mild to moderate stenoses. Quantification of valve regurgitation is possible by measurement of the regurgitation fraction with MR flow measurements as well as with MR volumetry/CT volumetry. But only the MR flow measurement is suitable for the quantification of valve regurgitation in patients with multiple valves involved or cardiac shunting. MRI and probably MDCT are the most reliable methods in the evaluation of ventricular volumes and therefore suitable for the follow-up in patients with valvular heart disease, because changes in volumes are important for therapeutic decisions in these patients. The crucial advantages of MRI compared to CT in the diagnostic of valvular heart diseases however are the absence of radiation exposure, the possibility of quantitative evaluation of valves function using flow measurements and the higher temporal resolution as compared to MDCT. Eine genaue Visualisierung der Klappenmorphologie ist sowohl mit der MRT als auch mit Hilfe der kürzlich eingeführten Methode der Multidetektorcomputertomographie (MDCT) möglich. Diese Methoden der Visualisierung der Klappen werden immer dann eingesetzt, wenn mit anderen nichtinvasiven Verfahren, wie z.B. der Echokardiographie, keine oder eine nur unzureichende Bildgebung möglich ist. Dies ist insbesondere bei Veränderungen der Klappen des rechten Ventrikels der Fall. Eine Quantifizierung von Klappenstenosen ist durch Bestimmung der Klappenöffnungsfläche, sowohl mit der MRT als auch mit der MDCT, durchführbar. Eine Abschätzung des instantanen Druckgradienten ist jedoch nur mit Hilfe der MR-Flussmessung möglich und liefert im Bereich von geringen bis mittleren Gradienten hinreichend zuverlässige Werte. Eine Quantifizierung von Klappeninsuffizienzen ist durch Bestimmung der Regurgitationsfraktion, sowohl mit Hilfe der MR-Flussmessung als auch mit der MR-Volumetrie oder CT-Volumetrie möglich. Nur die MR-Flussmessung lässt sich allerdings auch beim Vorliegen weiterer Klappenvitien oder kardialer Shuntverbindungen zur Quantifizierung einsetzen. Die MRT und wahrscheinlich auch die MDCT stellen die exaktesten bildgebenden Methoden zur Bestimmung der Ventrikelvolumina dar und sind damit gut geeignet für das Follow-up von Patienten mit Klappenerkrankungen, da Veränderungen der Volumina häufig therapieentscheidend sind. Die entscheidenden Vorteile der MRT gegenüber der CT in der Diagnostik von Herzklappenerkrankungen stellen die fehlende Strahlenexposition, die Möglichkeit einer quantitativen Beurteilung der Klappenfunktion durch die Flussmessung sowie die höhere zeitliche Auflösung im Vergleich zur MDCT dar.

Applications of specialized coils for high-resolution MRI on a whole-body scanner

To investigate the application of a mini-coil surface system for high-resolution MRI, 60 volunteers were examined in a 1.5-T whole-body scanner. Two replaceable probe heads were available: a circular 2.5-cm coil and a quadratic 5-cm coil, both of which were placed directly on the skin. The skin layers, Achilles tendon and finger joints were examined with the 2.5-cm coil and a FOV of 25 × 25 mm2. A matrix of 256 × 256 pixels resulted in a pixel size of 0.098 × 0.098 mm2. For imaging of the carpal tunnel, the 5-cm coil was used in transverse orientation. The FOV was 50 × 50 mm2 so that a matrix of 256 × 256 pixels led to a pixel size of 0.195 × 0.195 mm2. The resulting spatial resolution permitted visualization of the epidermis, dermis and subcutis, resulting in clear definition of anatomical detail of the musculoskeletal system. MRI measurement of skin-layer thickness did not correlate with histometric data (p<0.05). This discrepancy was due in part to shrinkage of the tumor specimen on histologic preparation. Other causes include the motion artifacts and the limited accuracy of determining thickness on the MRI display unit.