Figure 7d. Graphs show results obtained with the low-frequency transducer. Baseline instrument settings are as follows: gain, 60%; pulse repetition frequency, 1,500 Hz; filter, low; color versus echo priority, 100%; and insonation angle, 60°. The reference diameters of the feeding vessel (DO = 0.84 cm) and stenotic vessel (do = 0.24 cm) are represented on each graph as dashed and dotted lines, respectively. Variations of measurement of the diameter of the feeding vessel (bold line) and the diameter of the stenotic vessel (lighter line) are represented when one of the following settings was changed: (a) gain, (b) pulse repetition frequency (PRF), (c) and filter, for the longitudinal view, peak systolic velocity of 1 m/sec (
); longitudinal view, peak systolic velocity of 2 m/sec (
); transverse view, peak systolic velocity of 2 m/sec (x). (d) Gain setting was changed for the longitudinal view and peak systolic velocity of 2 m/sec for insonation angles of 40° (
), 60° (*), and 90° (|). Note that measurement data of the diameter of the normal vessel from the transverse view have been excluded.