Classification of arterial plaque by spectral analysis of in vitro radio frequency intravascular ultrasound data.

To test whether radio-frequency analysis of coronary plaques predicts the histological classification, r.f. data were collected using a 30 MHz intravascular ultrasound scanner. Two hundred ninety-nine regions-of-interest from eight postmortem coronary arteries were selected and identified by histology as falling into one of seven different tissue types. These are loose fibrous tissue (n = 78), moderate fibrous tissue (n = 27), dense fibrous tissue (n = 33), microcalcification (n = 14), calcified plaque (n = 55), lipid/fibrous mixture (n = 51) and homogeneous areas of lipid pool (n = 29). On the basis of a previous study, four spectral parameters were calculated for each of the regions-of-interest: maximum power (dB), mean power (dB), spectral slope (dB/MHz) over the bandwidth 18-35 MHz and the intercept of the spectral slope with the 0 Hz axis (dB). A minimum-distance classifier using the Mahalanobis (1948) distance was applied to the data. Following resubstitution of the training data into the classifier, the total correctly classified was 54%. The data were reclassified using three broader tissue groups: (1) calcified plaque, (2) lipid pool and (3) a mixed fibrous category, incorporating loose fibrous tissue, moderate fibrous tissue, dense fibrous tissue, lipid/fibrous mixture and microcalcification. The total correctly classified was 86%. Using "leave-one-out" cross-validation, the classification rates were 48% for seven tissue subgroups and 83% for three broader categories of tissue type.

Scanning techniques for three-dimensional forward-viewing intravascular ultrasound imaging.

Intravascular ultrasound (US) imaging is a useful tool for assessing arterial disease and aiding treatment procedures. Forward-viewing intravascular US imaging could be of particular use in severely stenosed or totally occluded arteries, where the current side-viewing intravascular US systems are limited by their inability to access the site of interest. In this study, five 3-D forward-viewing intravascular scanning patterns were investigated. The work was carried out using scaled-up vessel phantoms constructed from tissue-mimicking material and a PC-controlled scanning and acquisition system. The scanning patterns were examined and evaluated with regard to the image quality of dense and sparse data sets, the accuracy of quantitative measurements of lumen dimensions and the potential for clinical use. The relative merits and drawbacks of the different patterns are discussed and a preferred scanning pattern is recommended.

An instrument for the non-invasive objective assessment of velar function during speech.

This paper describes the development of a non-invasive, computer-based, clinical instrument that infers velar function by way of the measurement of nasal and oral airflow. The design criteria of the instrument were based upon a wide ranging review of current practice and available techniques. The instrument measures and displays both nasal and oral airflow, along with the envelope of the speech sound waveform. This allows the clinician to determine whether airflow is associated with oral or nasal airflow and, hence, to infer the position of the velum. Preliminary clinical trials suggest that the instrument provides valuable objective information about the movement of the soft palate, particularly within the time domain. Hence, it is believed that the device provides additional information for the assessment of velar function, complementing those techniques currently employed.

Assessment in the treatment of hypernasal speech with motor neuron disease: a clinical report.

The application of nasal anemometry in this patient's treatment proved to be of value in obtaining an objective assessment of this intervention. Nasal anemometry may be of use in other situations, for example, (1) in preassessment and postassessment of cleft palate surgery and surgical interventions to improve the velopharyngeal seal (such as pharyngoplasty), (2) in the evaluation of nasalized speech with conventional speech therapy, (3) in the evaluation of nasalized speech by use of a palatal training appliance, and (4) in the investigation of snoring.