For a hyperthermia planning environment the main requirements for the following numerical computation and visualization of the temperature field are the separation of several anatomical objects. Since different contrast objects cannot be seen at the same resolution, a segmentation technique using multiresolution segmentation planes is described here. The computation of these planes is based on the technique of region growing using watersheds in digital images. First, the watershed transformation is applied on the gradient image. The resulting image is then transformed into a graph on which a region growing process is performed. The iteration of these two actions results in hierarchical segmentation planes which differ in region amount and region size. Consequently low contrast objects can be separated in the lower planes whereas high contrast objects can be extracted in the higher planes.

One of the basic algorithm for the determination of the watershed transformation is the Meyer 2 algorithm. Unfortunately, the algorithm can lead to isolated regions and like other watershed approaches it also results in some inaccuracies due to the general approach of the WST. We developed a new strategy for the Meyer 2 algorithm resulting in the solution for these problems. For this the algorithm is applied on a more precise derivative with subpoint accuracy computing the derivatives for each direction separately. The labeled local derivatives are then used to label the image points. Immediately closed contours at subpoint locations are obtained and each point is assigned to a label or region respectively.

A cohort of 378 asthmatic children was studied from 7 to 35 yr of age at 7-yr intervals. On selection for inclusion in the study sample, the children had a wide range of severity of wheezing. At each 7-yr review, asthma severity, the presence of eczema or hay fever, and skin test reactivity to house dust mite or rye grass were recorded by questionnaire or clinical interview. We report on the course of asthma and these atopic conditions over the study period and discuss associations between the two phenomena. The presence of an atopic condition in childhood was found to increase the odds of more severe asthma in later life (odds ratio [OR] = 1.66, 95% confidence interval [CI]: 1.17 to 2.36 in the case of eczema; OR = 1. 39, 95% CI: 1.00 to 1.92 for hay fever; and OR = 2.25, 95% CI: 1.49 to 3.39 for skin test reactivity). Additionally, the odds of eczema and hay fever in later life increased with severity of asthma in childhood. The findings of this study provide substantially new quantitative information on the extent of association between asthma and atopic conditions from childhood into middle adulthood.

PURPOSE:To investigate the safety and imaging artifacts with different coronary arterial stents and magnetic resonance (MR) imaging sequences.MATERIALS AND METHODS:The heating, artifacts, and ferromagnetism with different stents were studied with a 1.5-T MR tomograph with ultrafast gradients by using turbo spin-echo, turbo gradient-echo, and echo-planar imaging sequences. Nineteen stents, which were 8-25 mm in length and 3.0-4.5 mm in diameter, were evaluated. Stent deviation induced by the magnetic field and during MR imaging, migration, and heating caused by the radio-frequency pulses were examined. The size of imaging artifacts was measured with all the stents under standardized conditions and with six stents after their implantation into the coronary arteries of freshly explanted pig hearts.RESULTS:All except two types of stents showed minimal ferromagnetism. No device migration or heating was induced. Turbo spin-echo images had minimal artifacts; larger artifacts were seen on the turbo gradient-echo and echo-planar images. With ultrafast gradients, the artifacts on the echo-planar images were substantially reduced.CONCLUSION:The studied coronary stents were not influenced by heating or motion during 1.5-T MR imaging. Artifact size differed according to the type and size of the stent and the MR imaging sequence used. Thus, patients with these stents can be safely examined.

BACKGROUND:Myocardial perfusion reserve can be noninvasively assessed with cardiovascular MR. In this study, the diagnostic accuracy of this technique for the detection of significant coronary artery stenosis was evaluated. METHODS AND RESULTS:In 15 patients with single-vessel coronary artery disease and 5 patients without significant coronary artery disease, the signal intensity-time curves of the first pass of a gadolinium-DTPA bolus injected through a central vein catheter were evaluated before and after dipyridamole infusion to validate the technique. A linear fit was used to determine the upslope, and a cutoff value for the differentiation between the myocardium supplied by stenotic and nonstenotic coronary arteries was defined. The diagnostic accuracy was then examined prospectively in 34 patients with coronary artery disease and was compared with coronary angiography. A significant difference in myocardial perfusion reserve between ischemic and normal myocardial segments (1.08+/-0.23 and 2.33+/-0.41; P<0.001) was found that resulted in a cutoff value of 1.5 (mean minus 2 SD of normal segments). In the prospective analysis, sensitivity, specificity, and diagnostic accuracy for the detection of coronary artery stenosis (> or =75%) were 90%, 83%, and 87%, respectively. Interobserver and intraobserver variabilities for the linear fit were low (r=0.96 and 0.99). CONCLUSIONS:MR first-pass perfusion measurements yielded a high diagnostic accuracy for the detection of coronary artery disease. Myocardial perfusion reserve can be easily and reproducibly determined by a linear fit of the upslope of the signal intensity-time curves.

With the growing importance of proteomics in biomedical and pharmaceutical sciences a need has emerged for computing tools that are capable of digitally visualizing and analyzing protein spot patterns within two-dimensional electrophoresis (2-DE) gel. Matching programs need to meet requirements such as interlaboratory comparison and the comparison of samples from different origins. For such research purposes, we have developed the CAROL system that implements new algorithms for spot detection and matching, which enable researchers to take a different approach to protein spot identification and comparison. The present short communication discusses how the system deals with uncertain geometric spot information that arises from streaks and complex spot regions and how this can be amplified for the matching procedure.

The goal of the study was the validation of an accurate method for three-dimensional reconstruction and quantitative assessment of volumes, lengths and diameters of coronary vascular branches and segments from biplane angiographic projections. Methods: The accuracy was tested in a complex phantom. In vivo, inter- and intraobserver agreement were assessed by analysis of routine angiograms. The sensitivity was evaluated using angiograms of patients having diagnostic vasoactive pharmacological intervention. Two-dimensional quantitative coronary angiography (2-D QCA) and 3-D QCA were compared concerning the accuracy of diameter evaluation. Results: 3-D QCA yields accurate results ( <3% error) even based on nonorthogonal views, provided that projections parallel to the object are avoided. The inter- and intraobserver variability is ≤ 5%. Significant (p < 0.01) changes of the volume (36–39%) and the diameter (19–21%) are detected following pharmacological intervention. 2-D QCA and 3-D QCA agree in short matched segments without foreshortening. 2-D QCA is rather sensitive to foreshortening and not suitable for evaluation of diameters of longer branches or total coronaries. Conclusion: 3-D QCA permits an accurate, reproducible and sensitive comprehensive three-dimensional geometric analysis of the coronaries and is superior to 2-D QCA with respect to extended diameter evaluation.

For the spot detection in 2D electrophoresis images an approach which is based on the combination of the watershed transformation (WST) with a-priori knowledge is presented. To identify spot regions in the over segmented result of the WST two types of regions have to be found: Regions that correspond to a complete spot and regions that cover only a part of a spot. The first localization step, the gray value analysis, is based on the assumptions that spot regions have significantly higher gray values than the background and that they border on a background region. Since not all remaining regions are spot or partial spot regions, additionally a curvature analysis is done. Here the a-priori knowledge is used that regarding a gel image as a surface, the shape of a spot is obviously convex. Consequently, considering the second derivative all required spot and partial spot regions can be obtained by the regions of convex curvature. In a final merging step all partial spot regions covering one spot have to be combined to only one spot region. As merging criterion two spot characteristics are used. A spot should have an approximately elliptical shape and partial spot regions of one spot should have a local convex curvature in a small neighborhood along their boundary.

Myocardial perfusion reserve can be noninvasively assessed with cardiovascular magnetic resonance. With magnetic resonance (MR) multislice dynamic imaging techniques it is possible to acquire the complete heart during the first pass of a contrast agent bolus. For diagnostic reasons an important question is to obtain quantitative parameters of the perfusion of the myocardium. We developed a model for the analysis of the contrast agent bolus pass in the myocardium and established a process for the complete task, which will support a routine clinical use delivering these quantitative parameters in a reproducible way. To evaluate the analysis in a collective of patients with single vessel disease and without significant coronary artery disease the signal intensity curves of the first pass of a gadolinium-DTPA bolus injected via a central vein were estimated before and after dipyridamole infusion.

Breathing motion artifacts reduce the quality of MR coronary artery images. Real-time adaptive navigator correction with different correction factors (0%, 30%, 60%, 80% of diaphragmatic displacement) was used to correct for respiratory motion in 3D coronary artery imaging. Significant improvements of image quality were achieved by adaptive motion correction in comparison with conventional navigator gating. A close correlation between the correction factor, which yielded optimal image quality, and cardiac displacement relative to diaphragmatic displacement was found. The quality of coronary artery imaging can be improved using real-time adaptive navigator correction. Correction factors have to be adjusted for each segment of the coronary arteries and for each patient. Magn Reson Med 42:408-411, 1999.

Fluid-filled systems are generally used for invasive pressure measurements in cardiology, anesthesiology and intensive care medicine. Wave reflection and attenuation cause considerable signal distortion. Methods. The transducer signal is amplified (no filtering) and sampled (rate 1 kHz) using an autocorrelation based algorithm to detect instantaneous cycle length. A digital Fourier transformation (DFT) for each heart cycle is performed. Amplitude and phase distortion are corrected using data matrices determined in in vitro experiments or calibration measurements for each fluid-filled system to be used. As a measure for accuracy the maximum of the difference of reference and corrected pressures (DIFF) was selected. 960 analyses were performed to assess the impact of correction, used system, mean pressure, time and A/D sampling rate on the agreement with reference pressure. Clinical examples are presented. Results. Mean pressure was correlated with DIFF (r = 0.83). The correction algorithm achieves a significant (p < 0.001) reduction of DIFF from 20-30 mm Hg to 0–5 mm Hg in the high pressure range and from 1–3 mm Hg to 0–1.5 mm Hg in the low pressure system in in vitro experiments and in clinical pressure recordings. Sampling frequency <1 kHz reduces accuracy. Conclusions. High fidelity correction of pressure signals from fluid-filled systems by harmonic analysis is feasible.

Protein spot identification in two-dimensional electrophoresis gels can be supported by the comparison of gel images accessible in different World Wide Web two-dimensional electrophoresis (2-DE) gel protein databases. The comparison may be performed either by visual cross-matching between gel images or by automatic recognition of similar protein spot patterns. A prerequisite for the automatic point pattern matching approach is the detection of protein spots yielding the x(s),y(s) coordinates and integrated spot intensities i(s). For this purpose an algorithm is developed based on a combination of hierarchical watershed transformation and feature extraction methods. This approach reduces the strong over-segmentation of spot regions normally produced by watershed transformation. Measures for the ellipticity and curvature are determined as features of spot regions. The resulting spot lists containing x(s),y(s),i(s)triplets are calculated for a source as well as for a target gel image accessible in 2-DE gel protein databases. After spot detection a matching procedure is applied. Both the matching of a local pattern vs, a full 2-DE gel image and the global matching between full images are discussed. Preset slope and length tolerances of pattern edges serve as matching criteria. The local matching algorithm relies on a data structure derived from the incremental Delaunay triangulation of a point set and a two-step hashing technique. For the incremental construction of triangles the spot intensities are considered in decreasing order. The algorithm needs neither landmarks nor an a priori image alignment. A graphical user interface for spot detection and gel matching is written in the Java programming language for the Internet. The software package called CAROL (http://gelmatching.inf.fu-berlin.de) is realized in a client-server architecture.

The combination of the watershed transformation on graphs with a tissue classification is presented. The watershed transformation on graphs results in hierarchical segmentation volumes that differ in region number and size. If an anatomical object corresponds to a region in a segmentation volume it has to be selected, since the region would be merged with the most similar neighbor region in the following volume. Such an object selection can be done using object descriptions. A possible approach is presented in this paper.

Time-efficient and easy-to-use segmentation algorithms (contour generation) are a precondition for various applications in radiation oncology, especially for planning purposes in hyperthermia. We have developed the three following algorithms for contour generation and implemented them in an editor of the HyperPlan hyperthermia planning system. Firstly, a manual contour input with numerous correction and editing options. Secondly, a volume growing algorithm with adjustable threshold range and minimal region size. Thirdly, a watershed transformation in two and three dimensions. In addition, the region input function of the Helax commercial radiation therapy planning system was available for comparison. All four approaches were applied under routine conditions to two-dimensional computed tomographic slices of the superior thoracic aperture, mid-chest, upper abdomen, mid-abdomen, pelvis and thigh; they were also applied to a 3D CT sequence of 72 slices using the three-dimensional extension of the algorithms. Time to generate the contours and their quality with respect to a reference model were determined. Manual input for a complete patient model required approximately 5 to 6 h for 72 CT slices (4.5 min/slice). If slight irregularities at object boundaries are accepted, this time can be reduced to 3.5 min/slice using the volume growing algorithm. However, generating a tetrahedron mesh from such a contour sequence for hyperthermia planning (the basis for finite-element algorithms) requires a significant amount of postediting. With the watershed algorithm extended to three dimensions, processing time can be further reduced to 3 min/slice while achieving satisfactory contour quality. Therefore, this method is currently regarded as offering some potential for efficient automated model generation in hyperthermia. In summary, the 3D volume growing algorithm and watershed transformation are both suitable for segmentation of even low-contrast objects. However, they are not always superior to user-friendly manual programs for contour generation. When the volume growing algorithm is used, the contours have to be postprocessed with suitable filters. The watershed transformation has a large potential if appropriately developed to 3D sequences and 3D interaction features. After all, the practicality and feasibility of every segmentation method critically depend on various details of the user software as pointed out in this article.

A 3D multiresolution segmentation approach based on a hierarchical watershed transformation (WST) on graphs for Computer Tomography images is presented. This approach is a 3D extension of the 2D WST on graphs which has already been successfully tested for the segmentation of CT images of the pelvis in hyperthermia planning. Analogous to the 2D technique the oversegmentation of the 3D WST is iteratively reduced through the application of the WST on graphs. Whereas for the 2D technique a stack of segmentation slices is constructed, here a stack of segmentation volumes consisting of 3D regions that correspond to 3D anatomical objects of different resolution in each volume are obtained. In contrast to the 2D approach which is at first applied on the image plane and hereinafter iteratively on graphs, the principle WST technique for graphs is now directly applied on the image plane. Besides the usage of a gradient with subpixel accuracy additionally a new procedure for the WST on this gradient is used. The labelled subpixel gradients are then used to label the voxels representing the segmentation result.

The developments in information technologies -- computer hardware, networking and storage media -- has led to expectations that these advances make it possible to replace 35 mm film completely by digital techniques in the catheter laboratory. Besides the role of an archival medium, cine film is used as the major image review and exchange medium in cardiology. None of the today technologies can fulfill completely the requirements to replace cine film. One of the major drawbacks of cine film is the single access in time and location. For the four catheter laboratories in our institutions we have designed a complementary concept combining the CD-R, also called CD-medical, as a single patient storage and exchange medium, and a digital archive for on-line access and image review of selected frames or short sequences on adequate medical workstations. The image data from various modalities as well as all digital documents regarding to a patient are part of an electronic patient record. The access, the processing and the display of documents is supported by an integrated medical application.

The developments in information technologies - computer hardware, networking and storage media - has led to expectations that these advances make it possible to replace 35 mm film completely by digital techniques in the catheter labaratory. Besides the role of an archival medium, cine film is used as the major image review and exchange medium in cardiology. None of the today technologies can fullfill completely the requirements to replace cine film. One of the major drawbacks of cine film is the single access in time and location. For the four catheter labaratories in our institutions we have designed a complementary concept combining the CD-R, also called CD-medical, as a single patient storage and exchange medium, and a digital archive for on-line access and image review of selected frames or short sequences on adequate medical workstations. The image data from various modalities as well as all digital documents regarding to a patient are part of an electronic patient record. The access, the processing and the display of documents is supported by an integrated medical application.