Transcranial Doppler (TCD), first described in 1982 [1], is a noninvasive ultrasound (US) study that involves the use of a low-frequency (â¤2 MHz) transducer probe to insonate the basal cerebral arteries through relatively thin bone windows.
Details. as.character and is.character are generic: you can write methods to handle specific classes of objects, see InternalMethods. Further, for as.character the default method calls as.vector, so dispatch is first on methods for as.character and then for methods for as.vector.
Character 6: Device. The device is specified in character 6 and is only assigned for those devices that. remain in the patientâs body at the conclusion of the procedure. There are four. different types of devices used in the PCS system, which will be discussed in. greater detail in chapter 3.