TALISMAN: Eine Softwareumgebung für die interaktive Verarbeitung medizinischer Bildserien

Fur die kardiologische Diagnostik eroffnen sich durch die interaktive Auswertung digitalisierter Bildserien zahlreiche neue Moglichkeiten. Die entstehenden Hardware- und Softwaresystem sind interaktiv zu erproben und unterliegen einer schnellen Entwicklung und Veranderung der Algorithmen und der Benutzeroberflachen. Die TALISMAN- Softwareumgebung erleichtert diese Vorgange durch folgende Eigenschaften: 1. Unterstutzung eines modularen Aufbaus der Anwendungsprogramme durch Bereitstellung eines Botschaftensystems (vgl. objektorientierte Umgebungen wie z. B. Smalltalk). 2. Standardisierung der Struktur der bildverarbeitenden Programm-Module (z.B. Daten-struktur und visuelle Darstellung der Bot…

Parametric assessment of myocardial perfusion by densitometric evaluation of digital subtraction coronary angiograms: a comparison with tomographic TL-201 scintigraphy results

Densitometric results about local myocardial perfusion are compared with those derived from a quantitative analysis of TL-201 single photon emission computer tomograms (TL-201 SPECT). Ten patients underwent conventional TL-201 SPECT at rest and after maximum bicycle stress and dipyridamole infusion the day prior to the investigation. SPECT was applied to provide improved spatial resolution for the detection of perfusion abnormalities. During the catheterization procedure four digital subtraction coronary angiograms were performed, two of the left and two of the right coronary artery both before and after pharmacologically induced hyperemia by intracoronary papaverine. The densitometric para…

Importance of calibration for diameter and area determination by intravascular ultrasound

Intravascular ultrasound (IVUS) permits quantitative assessment of the lumen diameter and area of coronary arteries. The experimental study was performed to evaluate the accuracy of diameter and area measurements.Lumen quantitation (lumen diameter D and cross-sectional area A) in lucite tubes (lumen diameter 2.5 to 5.7 mm, Plexiglas) was performed using a mechanical IVUS system (HP console, 3.5 F catheter, Boston Scientific, 30 MHz). The influence of fluid type (blood, water and saline solution), fluid temperature (20 degrees C/37 degrees C), catheter to catheter variation, gain setting and ultrasound frequency (12, 20 and 30 MHz) was determined. In blood at 20 degrees C there was a constan…

Verlustbehaftete Bilddatenreduktion von digitalen Koronarangiogrammen: Vergleich der Bildqualität durch einen objektiven Paramter

Assessment of image quality of intracoronary ultrasound systems with tissue-equivalent vessel phantoms

Imaging of vascular structures by intracoronary ultrasound (ICUS) is finding more and more applications in coronary diagnosis and in the assessment of interventional access. The authors describe a method for easy and quick production of tissue-equivalent vessel phantoms from a special hydrocolloid. The mechanical tolerance is less than 3/100 mm. With these phantoms the authors tested the calibration and measured the resolution properties of the SONOS intravascular ultrasonic system (Hewlett Packard). The measurements revealed a slight space related underestimation of diameters up to 280 /spl mu/m. Using cross correlation and auto correlation functions the authors analyzed digitized ultrason…

Quantitative comparison of new image processing methods for volumetric analysis of left ventricular contrast echocardiograms

An effort has been made to develop image processing methods which allow a definite and precise tracking of the borderline of the ventricle in two-dimensional echocardiograms. Experience is reported with two new methods, which are based on the gray-level rise (GL) and the signal-to-noise ratio (SNR) in combined heart-phase-triggered image series. A quantitative comparison of these time-series methods is presented with respect to the interpretation of a single native image (noncontrast image), a single contrast-material image, the corresponding subtraction image, and the corresponding color superposition image. The comparison is based on the calculation of the ejection fraction using the abov…

Three dimensional reconstruction of intracoronary ultrasound images: roadmapping with simultaneously digitised coronary angiograms

Three dimensional reconstruction of intracoronary ultrasound images offers a better appreciation of the axial relationship of vessel features and permits volumetric assessment, both of which depend critically on the spatial accuracy of the technique. This in turn is dependent on precise longitudinal orientation of the transducer in the vessel. The authors have developed a system which utilises simultaneously digitised fluoroscopic tracking of the radio-opaque transducer to orient the corresponding 2D ICUS images. This system may offer improved spatial accuracy of the three dimensional reconstruction and a means of precise identification of the 2D ICUS image which corresponds with a selected…

A query language for medical statistical analysis

While standard query languages support primarily the definition of single queries, in the evaluation of medical studies one usually formulates large sets of interdependent queries. A set of this type is called an integrated transaction. Our system for the definition of integrated transactions is based on the observation that in medicine a large number of statistical evaluations is founded on a conceptional model that can be structured as a tree. We describe a screen oriented tree editor for the relational data base system DBase and report on our experience with its application in the evaluation of the success rate of PTCA interventions.

Impact of routine angiographic follow-up after angioplasty

Abstract Background There is an ongoing controversy as to whether repeat coronary angiography should be routinely performed after successful percutaneous transluminal coronary angioplasty (PTCA). Methods We examined the 10-year outcome in 400 patients who had or had not undergone an angiographic control 6 months after successful PTCA and a subsequent event-free 6-month period. Our comparison was based on data gathered by questionnaire and telephone interview in 315 patients with (group A) and 85 patients without (group B) a routine 6-month angiographic control. Multivariate analysis (Cox model) was performed to identify predictors of adverse events. Results During the 10-year follow-up peri…

Factors Correlating with Restenosis after PTCA

Since its introduction in 1977 [7, 8], PTCA has been widely used in patients with coronary artery disease. Restenosis with recurrence of angina remains the major problem, limiting the long-term success after PTCA. Reported restenosis rates vary from 17% to 47% [9–19, 22–26]. In larger series [12, 15, 26] a restenosis rate of about 30% was constantly found, irrespective of the definition of restenosis in use.

Patient documentation for the ultrasound laboratory

The development of a PC based system for the storage of patient data in the echocardiography laboratory is described. Special design objectives were low cost and user friendliness, including an integrated special query language. After 3 years of use, the system stores 80000 diagnoses from 12000 patients without any relevant slowdown of response. Future developments concerning the communication between the database system and an echocardiographic sector scanner are discussed.

Requirements on resolution of digital imaging equipment in the cardiac catheterization laboratory.

We evaluated the requirements on spatial resolution of digital imaging equipment in the cardiac catheterization laboratory. Fifty cinefilms of the heart as the biological object and one film of a lead-ladder-pattern as an objective test were used. The patient films were examined for the visibility of the left ventricular angiogram, coronary arterial tree, coronary artery lesions, branching of septal arteries and the number of septal arteries. All films were viewed three times: with a 625 line TV-system, with a 1249 line TV-system and with a cineprojector. It was found that two application areas with different demands on the spatial and temporal resolution can be distinguished: 1) low spatia…

Color superposition: a new modality for contrast echocardiography.

To improve the estimation of endocardial borders in echocardiography, a technique has been developed to combine images from contrasted and noncontrasted echocardiograms of the same heart-phase using a color superposition mode. This method allows both experienced as well as less experienced examiners to define the endocardial borders more reproducibly and objectively. This is achieved by displaying tissue structures as gray level images while the ventricular cavity is marked selectively by the color display of the contrast material zone. Results of volume estimations of the left ventricle by different examiners using several imaging modes including color superposition display are presented.

Color-Doppler Flow Mapping of the Heart in Normal Subjects

Left ventricular volume determination using colour superpositioning of contrast echocardiograms

Abstract Objective: To delineate the endocardium, selective colouring of contrast regions in left ventricular contrast echocardiograms was performed using digital image processing. Methods: Volume determinations were performed in end-diastolic and end-systolic frames before and after the injection of contrast agent into the left ventricle and were compared to cineventriculograms in 30 patients by two independent investigators. Results: The mean end-diastolic volume measured was 114 ± 44 ml in the native, 235 ± 79 ml in the contrast, 175 ± 70 ml in the color-superimposed (observer 1), and 187 ± 79 ml in the cineventriculographic images. Thus, native echocardiograms underestimated angiographi…

Spectral estimators for Doppler analysis of intracoronary ultrasound catheters

With the zero-cross-detection method (ZCD) it has been shown that it is not possible to achieve a reproducible quantitative, and robust evaluation of an inter-coronary audio signal. The authors define spectral estimators to analyze the Doppler-audio signal. Measurements in a blood flow model have shown that the ZCD method underestimates the expected velocity at all speeds. Spectral analysis allows the determination of the actual and peak velocity more robustly and precisely. >

Quantitative Coronary Angiography and Digital Densitometric Perfusion Measurements?How to Assess the Success of Intracoronary Balloon Dilatation

Densitometric evaluation of digital subtraction angiocardiograms allows the assessment of local myocardial perfusion before and after pharmacological stimulation of coronary flow reserve during the catheterization procedure. This report deals with a case of a severe stenosis of the left coronary artery in which PTCA was regarded successful based on an appropriate increase in luminal diameter while an intima and media dissection at the dilatation site was documented. The perfusion measurements, however, pointed out a clear impairment of poststenotic myocardial perfusion after PTCA.

Variations in acoustical beam properties of intracoronary Doppler catheters.

The limitations of coronary angiography in assessing the functional significance of coronary obstructions is well known. While the critical variable of coronary blood flow cannot be readily measured, intraluminal Doppler sonography offers useful related functional information on blood flow velocity. In order to fully evaluate Doppler signals it is essential to have exact knowledge of the transducer transmission characteristics and of the ultrasound beam topology. In an experimental set-up, the transmitter-receiver characteristics of five commonly used Doppler catheters were investigated. In comparing the beam characteristics we found inhomogeneities in the lateral beam spread. At a penetrat…

Tissue classification by texture and spectral analysis of intracoronary ultrasound radio-frequency data

Imaging of vascular structures by intracoronary ultrasound allows in principal the recognition of different lesion types due to the echomorphology in the B-mode image. The subjective visual diagnosis is often difficult, especially the differentiation between thrombi and non-calcified plaque. The aim of this study was the extraction of features from the ultrasound radio-frequency signal for an objective characterization of coronary tissue. Methods of texture analysis and frequency analysis were used to differentiate red and white thrombi in vitro. Eight texture parameters of first and second order significantly differentiated red and white thrombi. The backscatter transfer function of red th…

Echocardiographic Image Analysis Based on the Evaluation of first Order Speckle Statistics

Basic theoretical considerations on the statistical properties of the speckle phenomenon indicate that a conventional quantization (intervals of uniform width) of the received and envelope detected RF — signal is not adequate. We therefore propose a quantization scheme which is based on the application of quantization intervals producing always the same confidence level (adaptive quantization). The advantages are: homogenous distribution of speckle noise reduction to about 10 – 20 significant quantization levels (with neglectable loss of morphological information) quantitative measure (confidence level) of the separability of regions represented with different quantization levels. We furthe…

Enhanced detection of contrast regions in echocardiograms by adaptive quantization

The statistics of ultrasound echo images are governed by Rayleigh statistics. The authors derive some experimentally verifiable predictions of this theory, compare them with experimental results obtained from echocardiographic images, and derive a new color coding scheme, (adaptive quantization) that is adapted to the signal-dependent noise predicted by theory. This results in some technical advantages and in an improved discrimination of regions of the echo image that are enhanced by echo contrast material. >

Ten-year outcome after coronary angioplasty in patients with single-vessel coronary artery disease and comparison with the results of the Coronary Artery Surgery Study (CASS).

The 10-year results of randomized trials comparing percutaneous transluminal coronary angioplasty (PTCA) in patients with single-vessel coronary artery disease (CAD) with coronary artery bypass grafting (CABG) and medical treatment are not available yet. The aim of this evaluation was to compare our 10-year follow-up results after PTCA in patients with single-vessel CAD with the 10-year follow-up results after CABG and medical treatment in the Coronary Artery Surgery Study (CASS) trial. We evaluated the clinical outcome of 509 patients with single-vessel CAD 10 years after coronary angioplasty. The data were compared with the results of 214 patients with single-vessel CAD after CABG or medi…

Densitometry and parametric imaging with quality control

X-ray contrast image series of the myocardium were studied using the approaches of densitometry and parametric imaging accompanied by quality control. Contrast angiograms were digitized at six predefined phases of the heart cycle. For densitometry, regions of interest (ROIs) were defined semi-automatically for all phases. The resulting six densograms were summed up and weighted according to their quality determined by a measure. Previously validated parameters such as rise time were calculated. The enddiastolic images were only used for the calculation of color-coded parametric images accompanied by pixel-densogram-quality information. An observer gives a score for the perfusion of roughly …

Analysis of risk factors for restenosis after PTCA

To identify risk factors for restenosis, we evaluated data in 473 patients with single-vessel percutaneous transluminal coronary angioplasty (PTCA) and control angiography after 6 months. Restenosis, defined as (1) loss greater than 50% of the initial gain, and (2) stenosis greater than 50% was found in 138 patients (29.2%). Univariate analysis revealed eight factors related to restenosis: (1) duration of symptoms less than 1 month (P = 0.005), (2) unstable angina (P = 0.004), (3) high-grade stenosis before PTCA (P = 0.014), (4) large residual stenosis after PTCA (P = 0.001), (5) insufficient improvement of stenosis (P = 0.042), (6) prolonged single inflation time (P = 0.017), (7) prolonged…

Non-invasive determination of cardiac output by transesophageal Doppler ultrasound-clinical application and validation

The authors describe the development and validation of a device using transesophageal (TE) Doppler ultrasound to provide continuous and noninvasive monitoring of cardiac output (CO) and related parameters. In intubated and artificially ventilated patients who underwent pulmonary artery catherization for hemodynamic monitoring, CO was determined by the esophageal Doppler ultrasound probe and compared to the results obtained simultaneously by means of thermodilution. A very close correlation was found between the results (r=0.99), with a standard estimate of error less than 5% as well as good reproducibility (r=0.96 and r=0.98). >

Angiocardiographic digital still images compressed via irreversible methods: concepts and experiments.

Abstract We defined, implemented and tested two new methods for irreversible compression of angiocardiographic still images: brightness error limitation (BEL) and pseudo-gradient adaptive brightness and contrast error limitation (PABCEL). The scan path used to compress the digital images is based on the Peano–Hilbert plane-filling curve. The compression methods limit, for each pixel, the brightness errors introduced when approximating the original image (i.e. the difference between the values of corresponding pixels as grey levels). Additional limitations are imposed to the contrast error observed when considering along the scan path consecutive pixels of both the original and the reconstru…

Einfluß von qualitativen Stenosecharakteristika auf die Meßqualität verschiedener QCA-Systeme (Impact of lesion characteristics on the quality of measurements with different QCA systems)

Die neueren QCA-Systeme weisen bei In-vitro-Messungen eine vergleichbare Reproduzierbarkeit und Genauigkeit der Mesergebnisse auf. Wir untersuchten, welchen Einflus die Morphologie von Koronararterienstenosen und die Bildqualitat auf die Mesergebnisse von drei fuhrenden QCA-Systemen (AWOS, Cardio und CMS) hat. Hierzu wahlten wir 57 Stenosen aus, die eine klinisch reprasentative Verteilung bezuglich des Stenosegrades, verschiedener Lasionscharakteristika und der Bildqualitat aufwiesen. Prozedurale Fehlerquellen wurden, soweit moglich, eliminiert. Drei Untersucher fuhrten je Stenose funf Messungen mit jedem der drei Systeme durch. Bei drei Stenosen war eine Auswertung nicht moglich.

Reliability and Accuracy of Echocardiography for Follow-up Studies after Intervention

By two-dimensional echocardiography limitations of M-mode echocardiography have been eliminated. As a direct and noninvasive method two-dimensional echocardiography seems to be an ideal method for analysis of left ventricular function in follow-up studies. In relation to other methods there are no limitations concerning x-ray exposure, physicians and patients safety. Before different studies can be discussed, reliability and accuracy of two-dimensional echocardiography have to be evaluated. Beat-to-beat, day-to-day, intra- and interobserver variability will be discussed, followed by description of follow-up studies after intervention.

Comparison of Statistical Methods for the Detection of Contrast Material in Echocardiographic Image Sequences

Ultrasonic imaging of the heart is a diagnostic tool which is increasingly used in cardiology. In addition to the representation of important anatomical information two dimensional images provided by mechanical or electronically steered sector scanners can be used for the extraction of functional parameters of the heart (as e.g. enddiastolic volume or ejection fraction). A poor definition of the endocardial border especially resulting from the noisy appearance of the images and from qualitatively restricted echocardiograms leads to uncertainties in the quantitative analysis and therefore requires refined methods for the determination of functional parameters. Our investigations which are ba…

The effect of balloon dilatation on post-stenotic myocardial perfusion before and after stimulation of coronary flow reserve: evaluation by the densitometric parameter 'mean rise time'.

From densitometric evaluation of digital subtraction cineangiocardiograms the parameter 'Mean Rise Time' (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximal opacification can be derived; this parameter revealed a close correlation with the results on myocardial perfusion obtained by Thallium-201 scintigraphy. A prolonged 'Mean Rise Time' was indicative of an impairment of myocardial perfusion. We have developed a heart-phase gated real-time digitization procedure and computer-supported method for the densitometric estimation of the MRT to obtain information about the effect of coronary balloon dilatation on myocardial perfusion…

Intraluminal Doppler-Sonography: Analysis and “in Vitro Test” of a New Device

In treating patients with coronary heart disease it’ s necessary first to determine what influence the stenose has on the coronary blood flow. This is a prerequisite for any invasive treatment method. Coronary angiography explosures are only partially useful in attaining a functional evaluation of the haemodynamic stenoses.

New techniques for visualization of losses due to image compression in grayscale medical still images

To evaluate the visual influence of irreversible compression on medical images, changes of the images have to be visualized. The authors have explored alternative techniques to be used instead of the usual side-by-side comparison, where the information contained in both images is perceived in a single image, preserving the context between compression errors and image structures. Thus fast and easy comparison can be done. These techniques make use of the human ability to perceive information also in the dimensions of color, space, and time. A study was performed with JPEG-compressed coronary angiographic images. Changes in the resulting images for six compression factors from 7 to 30 were sc…

Parametric assessment of myocardial perfusion during interventional cardiac catheterization by means of X-ray densitometry-short-and long-term results.

X-ray densitometric evaluation of digital subtraction angiocardiograms allows an assessment of myocardial perfusion by means of the parameter 'MEAN RISE TIME' (MRT), defined as the time from the onset of local myocardial contrast medium opacification to the point of maximum opacification. Best results are obtained when the response of that parameter is compared before and after stimulation of coronary flow by papaverine. A prolongation of this parameter, especially after papaverine, was indicative of an impairment of myocardial perfusion, when compared to the results of TL-201 scintigraphy. In 50 patients with single vessel coronary artery disease the results of MRT pre and post papaverine …

Intraluminal Doppler-sonography: a new device for data analysis and its in vitro test

Summary form only given. A special data acquisition unit has been developed which allows to process on-line not only the mean-phasic Doppler shift signal but also to analyze the spectral contents and the received A-mode signal. The probe consists of a 3f-catheter which is activated by a pulsed transmitter-receiver (Millar). The carrier frequency is 20 MHz and the impulse repetition rate is 62.5 kHz. Two modular A/D converters are used. One digitizes directly the Doppler shift frequencies in the range less than 20 kHz (sampling rate 100 kHz, resolution 12 bit); the other digitizes the RF-signal (sampling rate 200 MHz, resolution 8 bit). For further processing, data are transferred via separa…

Intravascular ultrasound detected classification of coronary lesions as a predictor of dissections after balloon angioplasty.

Dissection after balloon angioplasty of coronary arteries may give rise to an unfavourable early outcome. Compared with coronary angiography, intravascular ultrasound (IVUS) allows more detailed characterisation of dissections. We investigated the incidence and type of dissections after balloon angioplasty in calcified coronary lesions. IVUS was performed in 43 patients with 48 lesions before and after percutaneous balloon angioplasty. Significant calcification was defined as an arc of more than 90 degrees with typical acoustic shadowing. Dissections were classified as type A when the media was not involved by the dissection and as type B when media involvement had occurred. In the group wi…

New balloon catheter for prolonged percutaneous transluminal coronary angioplasty and bypass flow in occluded vessels.

A new balloon catheter was developed for continuous perfusion of coronary arteries during angioplasty (CPC catheter). Steerable Gruntzig balloon catheters (3.7 mm) with two lumina were formed. The first lumen was used for balloon inflation. Side holes to the second lumen proximally and distally to the balloon were created for coronary perfusion even during inflation phase. At a perfusion pressure of 120 mmHg, a flow rate of 63 +/- 3 ml/min with 0.9% saline and 43 +/- 1 ml/min with plasma expander were measured. In experiments on five dogs, dilation time until appearance of signs of ischemia could be prolonged in three of five dogs from 30 to 40 s, 120 to 203 s, and 180 to 420 s comparing co…

A framework for PACS development in cardiology

The authors develop a framework for the integration of cardiology into hospitalwide picture archiving and communication systems (PACSs) by the definition of user requirements in cardiology image information systems. These user requirements have to be based on the consensus of users and industry. A topdown layered scheme is proposed for the development of documents based on user requirements. The structure of committees within the European Society of Cardiology that are working in this field is discussed. >

Computerized estimation of quality standards for the X-ray densitometric assessment of myocardial perfusion

The densitometric evaluation of heart-phase-gated digital subtraction coronary angiograms derives different parameters which provide information about coronary blood flow, myocardial perfusion, and coronary flow reserve: appearance time, rise time, mean ascending time, and maximum intensity. The reliability and reproducibility of these measurements and of the derived parameters were investigated. Four digital subtraction coronary angiograms were obtained in ten patients, including two baseline measurements and two measurements under hyperemia induced by papaverine ic. Different reproducibility results were found for the parameters, depending on the heart phase of the densogram (diastolic be…

Ein diagnostisch-therapeutischer Stufenplan bei instabiler Angina pectoris

Unter instabiler Angina pectoris wird 1. eine Crescendo-Angina-pectoris verstanden, die an Starke und Haufigkeit zunimmt oder sich auf eine bestehende typische Belastungs-Angina-pectoris aufpfropft, 2. eine Angina pectoris in Ruhe und bei minimaler Belastung und 3. eine neu auftretende Angina pectoris, die bei geringster Belastung ausgelost wird [3].

Determination of myocardial perfusion and coronary flow reserve by densitometric measurements: a selective classification of regions of interest

To evaluate the functional effect of a coronary artery stenosis on the dependent myocardium, digitized coronary angiograms (DCAs) were recorded. The DCAs, acquired during heart catheterization, provide information about myocardial perfusion and coronary flow reserve of areas supplied by this coronary artery. For each analysis the myocardium is separated into different regions of interest (ROIs); 16 ROIs in the distribution of the LCA and 8 ROIs for the RCA. In addition to that, the ROIs of the diseased vessels are divided into ROIs which are proximal, within and distal to the stenosis. Using a semiautomatic procedure, densograms are constructed from which the parameter rise time is calculat…

Intravascular ultrasound imaging of arterial wall architecture.

Intravascular ultrasound (IVUS) is a promising new technique for assessing vascular morphology and structure. Controversy exists whether the three-layer appearance of the arterial wall correctly reflects the histologic structures of the intima, media, and adventitia. We performed an experimental study to clarify the three-layer appearance. The vessel wall architecture was analyzed by IVUS on eight different kinds of plastic cylinders, 24 normal blood vessels from pigs, and 59 human arterial segments. A distinct three-layer appearance was observed on all the plastic cylinders when the ultrasound beam was perpendicular to the wall. A three-layer appearance was also seen in the arterial wall, …