| atrial echo | Electrical reactivation of the atrium by a retrograde impulse returning from the A-V node while the antegrade impulse continues to the ventricle; characterised electrocardiographically, by a pair of P waves enclosing a QRS complex, the second P wave being inverted, indicating that it is the reverse (the retrograde pathway) of the pathway of the first P wave (the antegrade pathway). (05 Mar 2000) |
|---|---|
| spin echo | A commonly used technique to recover T2 relaxation signals in magnetic resonance imaging, by using a 180 |
| nodus sinuatrialis echo | A postectopic sinus beat occurring earlier than would be expected from the preceding sinus node discharge interval; i.e., the interval following a premature beat of supraventricular origin is less than the ordinary cycle length between sinus beats, whereas ordinarily the interval would be expected to exceed cycle length. (05 Mar 2000) |
| echo | Origin: L. Echo, Gr. Echo, sound, akin to, sound, noise; cf. Skr. Va to sound, bellow; perh. Akin to E. Voice: cf. F. Echo. 1. A sound reflected from an opposing surface and repeated to the ear of a listener; repercussion of sound; repetition of a sound. "The babbling echo mocks the hounds." (Shak) "The woods shall answer, and the echo ring." (Pope) 2. Sympathetic recognition; response; answer. "Fame is the echo of actions, resounding them." (Fuller) "Many kind, and sincere speeches found an echo in his heart." (R. L. Stevenson) 3. A wood or mountain nymph, regarded as repeating, and causing the reverberation of them. "Sweet Echo, sweetest nymph, that liv'st unseen Within thy airy shell." (Milton) A nymph, the daughter of Air and Earth, who, for love of Narcissus, pined away until nothing was left of her but her voice. "Compelled me to awake the courteous Echo To give me answer from her mossy couch." (Milton) Echo organ, a stop upon a harpsichord contrived for producing the soft effect of distant sound. To applaud to the echo, to give loud and continuous applause. "I would applaud thee to the very echo, That should applaud again." (Shak) Source: Websters Dictionary (01 Mar 1998) |
| echo beat | Extrasystole produced by the return of an impulse in the heart retrograde to a focus near its origin which then returns antegradely to produce a second depolorization. (05 Mar 2000) |
| echo-free | The property of appearing echo-free or without echoes on a sonographic image; a clear cyst appears anechoic. See: transonic. Synonym: echo-free. Origin: G. An-priv. + echo + ic (05 Mar 2000) |
| echo planar | A method of magnetic resonance imaging that allows rapid image acquisition during free induction decay, using technically difficult rapidly oscillating radiofrequency gradients. (05 Mar 2000) |
| echo-planar imaging | A type of magnetic resonance imaging that uses only one nuclear spin excitation per image and therefore can obtain images in a fraction of a second rather than the minutes required in traditional mri techniques. It is used in a variety of medical and scientific applications. (12 Dec 1998) |
| echo reaction | A disorder of speech where there is an involuntary repetition several times of the same word. (27 Sep 1997) |
| echo speech | A disorder of speech where there is an involuntary repetition several times of the same word. (27 Sep 1997) |
| absent nasal septum | <radiology> Cocaine, Wegener's (midline lethal granuloma), surgery, trauma, syphilis, sarcoid (12 Dec 1998) |
| alveolar septum | The tissue intervening between two adjacent pulmonary alveoli; it consists of a close-meshed capillary network covered on both surfaces by very thin alveolar epithelial cells, one of the bony partitions between the tooth sockets. Synonym: septum interalveolare, alveolar septum, septal bone. (05 Mar 2000) |
| anterior vein of septum pellucidum | Vein draining the anterior part of the transparent septum; it empties into the superior thalamostriate vein. Synonym: vena septi pellucidi anterior. (05 Mar 2000) |
| aortopulmonary septum | The spiral septum which, during development, separates the truncus arteriosus into a ventral pulmonary trunk and dorsal aorta. See: bulbar ridge. (05 Mar 2000) |
| atrial septum | The wall between the two upper chambers (the right and left atrium) of the heart. (12 Dec 1998) |