Alessandro Mazzarisi

In vivo radiofrequency-based ultrasonic tissue characterization of the atherosclerotic plaque.

Background and Purpose The ultrasonic image can offer unique information on the composition of atherosclerotic plaque, ie, the relative content of lipids, fibrous tissue, and calcific deposits. To date, however, the echographic assessment of plaque structure is based on a subjective, qualitative evaluation of the bidimensional images. We evaluated the feasibility and accuracy of assessing, in vivo, the acoustic properties of arterial carotid plaques by means of a suitably modified echographic apparatus allowing direct access to the radiofrequency signal. Methods In 15 patients undergoing carotid thromboendarterectomy, the ultrasonic findings in 70 discrete sites (within the plaque, n=54; normal sites, n=11; or intraluminal thrombi, n=5) were correlated with the histological analysis (hematoxylin-eosin and Mallory trichrome stains) independently performed on the arterial samples. The pathological examination was carried out at a similar level of the insonation; the sites analyzed within the plaque were chosen because of their uniform echoic characteristics. In each ultrasonic region of interest selected from the echographic image, the integrated amplitude of the rectified radiofrequency signal was measured as the integrated backscatter index. Results The intimal-medial layer of normal carotid wall (n=11) exhibited values of −32.5 ± 9.4 dB. The integrated backscatter index in fatty sites (n=11, −40.3 ± 5.4 dB) differed from that of fibrous (n=12, −23.8 ± 5.0 dB) and calcified (n=26, −11.5 ± 5.2 dB, P < .01 for all intergroup differences) sites. Intraluminal thrombotic sites (n=5, −42 ± 5.1 dB, P < .01) differed from fibrous and calcified subsets (P < .01) but overlapped (P=NS) with fatty sites. Histological sampling also showed two sites of intraplaque hemorrhage that exhibited very low backscatter values (−53 and −58 dB) and three fibrofatty sites showing backscatter values (−28, −28, and −32 dB) intermediate between the fibrous and the fatty subsets. Conclusions Quantitative analysis of integrated backscatter of the arterial wall is feasible in humans and provides an operator-independent assessment of plaque echoic structure. In particular, integrated backscatter is effective in distinguishing lipidic, fibrotic, and calcific components in human atherosclerotic plaques.

Quantitative assessment of ultrasonic myocardial reflectivity in hypertrophic cardiomyopathy

The purpose of this study was to investigate the relation between acoustic properties of the myocardium and magnitude of left ventricular hypertrophy in patients with hypertrophic cardiomyopathy. An on-line radio frequency analysis system was used to obtain quantitative operator-independent measurements of the integrated backscatter signal of the ventricular septum and posterior free wall in 25 patients with hypertrophic cardiomyopathy and 25 normal age-matched control subjects. The integrated values of the radio frequency signal were normalized for the pericardial interface and expressed in percent. Tissue reflectivity was significantly increased in the hypertrophied ventricular septum, as well as in the nonhypertrophied posterior free wall, in patients with hypertrophic cardiomyopathy (58 +/- 15% and 37 +/- 12%, respectively) compared with values in normal subjects (33 +/- 10% and 18 +/- 5%, respectively; p less than 0.001). Furthermore, measurements of reflectivity of the septum or posterior free wall, or both, were beyond 2 SD of normal values in greater than 90% of the patients and were also abnormal in each of the five study patients who had only mild and localized left ventricular hypertrophy. No correlation was identified between myocardial tissue reflectivity and left ventricular wall thickness in the patients with hypertrophic cardiomyopathy (correlation coefficient r = 0.4; p = NS). These findings demonstrate that myocardial reflectivity is abnormal in most patients with hypertrophic cardiomyopathy and is largely independent of the magnitude of left ventricular hypertrophy. Moreover, quantitative analysis of ultrasonic reflectivity can differentiate patients with hypertrophic cardiomyopathy from normal subjects independently of clinical features and conventional echocardiographic measurements.

Flow quantitation by radio frequency analysis of contrast echocardiography.

Contrast echocardiography has the potential for measuring cardiac output and regional blood flow. However, accurate quantitation is limited both by the use of non-standard contrast agents and by the electronic signal distortion inherent to the echocardiographic instruments. Thus, the aim of this study is to quantify flow by combining a stable contrast agent and a modified echo equipment, able to sample the radio frequency (RF) signal from a region of interest (ROI) in the echo image. The contrast agent SHU-454 (0.8 ml) was bolus injected into anin vitro calf vein, at 23 flow rates (ranging from 376 to 3620 ml/min) but constant volume and pressure. The ROI was placed in the centre of the vein, the RF signal was processed in real time and transferred to a personal computer to generate time-intensity curves. In the absence of recirculation, contrast washout slope and mean transit time (MTT) of curves (1.11–8.52 seconds) yielded excellent correlations with flow: r=0.93 and 0.95, respectively. To compare the accuracy of RF analysis with that of conventional image processing as to flow quantitation, conventional images were collected in the same flow model by two different scanners: a) the mechanical sector scanner used for RF analysis, and b) a conventional electronic sector scanner. These images were digitized off-line, mean videodensity inside an identical ROI was measured and time-intensity curves were built. MTT by RF was shorter than by videodensitometric analysis of the images generated by the same scanner (p<0.001). In contrast, MTT by RF was longer than by the conventional scanner (p<0.001). Significant differences in MTT were also found with changes in the gain setting controls of the conventional scanner. To study the stability of the contrast effect, 6 contrast injections (20 ml) were performed at a constant flow rate during recirculation: the spontaneous decay in RF signal intensity (t1/2=64±8 seconds) was too long to affect MTT significantly.In conclusion, the combination of a stable con trast agent and a modified echocardiographic instrument provides accurate quantitation of flow in anin vitro model; RF analysis is more accurate than conventional processing as to flow quantitation by contrast echocardiography.

Flow quantitation by contrast echocardiography. Effects of intervening tissue and of the angle of incidence between flow and ultrasonic beam.

The combination of a standardized echographic contrast agent with the analysis of the ultrasonic radio frequency (RF) signal allowedin vitro flow quantitation in a circulation model. The purpose of this study was to investigate both the effects of biological tissues, intervening between probe and insonated structure, and the effects of the angle of incidence between flow and ultrasonic beam on RF flow quantitation. Thus, the contrast agent SHU 454 was intravenously injected (0.4 ml) as a bolus into a circulation model, at variable flow rates, while keeping the pressure and volume of the vessel constant. Injections were performed with saline interposed between probe and vessel and after the addition of the subcutaneous tissue of a pig; injections were also performed using the probe normal to the flow and with an angle of incidence of 45°. Echographic data were recorded by a mechanical sector scanner, capable of sampling the RF signal from a region of interest positioned in the center of the vein. Contrast echo time-intensity curves were generated. As expected, both peak intensity and the area under the curves decreased with intervening tissue (− 58 and − 70% of baseline values, respectively, p<0.001). Surprisingly, mean transit time also decreased with intervening tissue (from 1.12±0.25 seconds with saline, to 0.92±0.13 seconds with tissue, p<0.001), thus producing a systematic overestimation of flow (21% on the average). To compensate for signal attenuation, contrast injections were repeated in the presence of tissue after increasing the electronic signal amplification (10 dB), and transit time did not significantly differ from control. Moreover, mean transit time was slightly shorter with an angle of 45° (1.03 ° 0.19 seconds) than with an angle of 90° (1.12±0.25 seconds, p<0.05). However, when the data collected with both angles of incidence were plotted together, the correlation with flow remained very close (r=0.94). In conclusion: intervening tissue influences flow quantitation by contrast echocardiography: these modifications can be compensated for by increasing the electronic signal amplification; the angle of incidence between flow and ultrasonic beam also influences flow quantitation: however, this influence is trivial, and can be neglected for practical purposes.

New standards for cardiology report and data communication: an experience with HL7 CDA release 2 and EbXML

The diffusion of health standards, connected to technological infrastructure, finally opens the road to a new way of interconnecting and integrating different clinical solutions. New standards coming from established Organizations such as HL7 and DICOM, are going to be integrated with Communication Organization to build the Health environment Info-structure of the next decade. The purpose of this work is to show how this is possible, using simple and affordable methods: The recently approved HL7 Clinical Document Architecture Release 2 standard for message packaging and the newly approved ebXML 3.0 specifications. These promising standards can be used in conjunction with Web-Services and Web Service Description Language (WSDL) technology. This type of solution allows to be totally independent from the development platform, from the programming language and the operating system used. EbXML is an XML framework for business-to-business (B2B) environment developed by the ebXML Initiative

HL7 clinical document architecture to share cardiological images and structured data in next generation infrastructure

In medicine and in cardiology different standards are used for treatment of clinical and iconographic information. Among the most relevant there are HL7 for clinical data and DICOM for images and signals. The advent of electronic health record systems (EHR) and the request for data integration coming from different imaging modalities and diagnostic instrumentation, offer us a technological panorama difficult to manage. There is an increasing demand to select the most meaningful information in a simple and effective way, without the duty and the necessity to create from scratch new ways of data communication and sharing. Hence an agreement, in order to be able to feed a new multidisciplinary information databases, is necessary. To reach this goal, we used the emergent development of HL7 in the field of the structure of clinical document architecture (CDA).

An open source based application for integration and sharing of multi-modal cardiac image data in a heterogeneous environment

DICOM format has been recognized as the de facto standard for storage, transferring and sharing of cardiac images along different modalities like magnetic resonance imaging (MRI), nuclear medicine, computer tomography (CT), digital angiography (XA), digital radiology. However, in many medical environments there is a large need to have cardiac images available in formats (i.e. GIF, BMP or JPEG) that are compatible with widely used office automation applications. The here proposed system for multi modality image sharing and conversion is based on both the standard DICOM communication protocol and the common internet file system (CIFS) protocol. DICOM images from any DICOM compliant station can be transferred to a dedicated DICOM server, which has been implemented using the freely available DCMTK DICOM toolkit from Kuratorium OFFIS. An automatic procedure converts DICOM images into the desired image format, creating at the same time a file tree that allows fast and easy retrieval of image data. The entire proposed framework is implemented using open source software with large advantages in terms of cost reduction and software flexibility and robustness.

On-line two-dimensional evaluation of ultrasonic integrated backscatter

We describe an apparatus for the on-line evaluation of integrated backscatter from areas of tissue. The equipment is fully integrated into a B-mode ultrasonic system; there are therefore no new operating procedures to be learned. It provides a simultaneous display of conventional information, together with parameters of tissue characterization. The apparatus is fast and, over a broad diagnostic frequency range, may be used in conjunction with conventional equipment employing transducers.

ON-LINE EVALUATION OF ULTRASONIC INTEGRATED BACKSCATTER

Although it is already known that reflected ultrasonic signals (backscatter) are changed by the structure of the tissue through which they pass, clinicians are still awaiting a practical instrument in which information from backscatter reflections will serve as a diagnostic aid additional to that provided by conventional ultrasonic scans. The equipment described here is both small and fast, and is integrated into a normal ultrasound installation. No new operating procedures have to be learned. The integrated backscatter is calculated on-line and presented on an LED as tissue characterization parameters. In order to minimize noise due to physical movement of the heart during an investigation of the myocardium, the analysis is synchronized with the ECG; and as an aid to the user, the normal system VDU displays both the ECG and the activating trigger pulse derived from the R-wave peak. An A-scan display has been used but this could readily be adapted for B-scan operation and single line analysis. Tests with backscattering models and standard instrumentation have shown no significant difference between results using time domain or frequency domain analysis.

In vivo identification of mitral valve fibrosis and calcium by real-time quantitative ultrasonic analysis

Conventional echocardiography provides fundamental information about mitral valve morphology and function but has a relatively low specificity in evaluating valve calcific deposits, which is critical information for the preoperative decision to perform commisurotomy or replacement. In vitro radiofrequency ultrasonic quantitative analysis of the mitral valve has been demonstrated to be a reliable tool in identifying normal, fibrotic and calcific valves. This study evaluates quantitative ultrasound characterization of the mitral valve in vivo. Thirty-three patients, scheduled to undergo mitral valve replacement, and 20 normal subjects (10 young and 10 older control subjects) were studied with a 2.25-MHz transducer. Radiofrequency signal was analyzed by a microprocessor system (used with an M-mode commercially available echocardiograph) for on-line evaluation of ultrasonic backscatter with 8 bits of amplitude resolution, 40-MHz sampling rate and a 1-microsecond acquisition gate. The integrated value of the rectified radiofrequency signal amplitude was deemed the integrated backscatter index. The highest value recorded with the ultrasonic analysis from each valve was taken as representative and expressed as the percent value with respect to the pericardial integrated backscatter index value of that subject. The 33 excised mitral valves underwent histologic examination. Four groups were identified: young controls (group I, n = 10); older controls age-matched with patients (group II, n = 10); patients with fibrotic mitral valves (group III, n = 13); and patients with calcific mitral valves (group IV, n = 20).(ABSTRACT TRUNCATED AT 250 WORDS)