Spectral Doppler refers to the combination of either continuous wave Doppler or pulsed Doppler with a spectral display. Spectral Doppler provides a quantitative analysis of the velocity and direction of blood flow.
The Fourier spectrum analyzer performs a fast Fourier transformation on the Doppler signal. The amplitudes of the resulting spectra are encoded as brightness. In the 2D spectral display, the frequency shift is depicted in the vertical and the time in the horizontal axis. The range of blood velocities in the volume produces a corresponding range of frequency shifts.

See also Acceleration Index and Triplex Exam.

Ultrasound biomicroscopy utilizes high frequency (10 - 50 MHz) diagnostic ultrasound to examine living tissue at a microscopic level and allows to image the skin with extremely high resolution to a depth of 2-3 centimeters. Ultrasound biomicroscopy images provide detailed anatomical information that can lead to better and more accurate treatments and avoid a biopsy.
Ultrasound biomicroscopy improves also the spatial resolution of US images of the anterior segment of the eye. US biomicroscopy of the eye operates in the 50 MHz range with a possible axial resolution on the order of 30 μm. In this frequency range, tissue penetration of only approximately 5 mm is attainable. Both continuous wave Doppler and high-frequency pulsed Doppler can be used.

See also Ultrasound Imaging Procedures, A-Scan, B-Scan and C-Scan.

Variance is the modification of Doppler frequencies within each pixel during a pulse packet with color Doppler flow imaging. Variance is mapped to the color green and is used to detect turbulence. At low variance (laminar flow) pixels within each range gate are encoded in red or blue according to flow direction. At high variance (turbulent flow) a percentage of pixels within each range gate are encoded with green according to the degree of spectral broadening.

From Siemens Medical Systems;
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From ALOKA Co., Ltd.;
'Superior Performance and Versatility
Based on decades of experience, the SSD-1000 is a high performance and versatile diagnostic ultrasound system. It uses our advanced technologies and over 5 decades of innovative ultrasound experience. Using the same technology as our more expensive systems, the SSD-1000 provides superior imaging capabilities in a compact and mobile setting.
We also employ Super High Density transducers (found our high-end systems) to enhance imaging resolution. High-quality images help you accurately diagnose patients in less time.
The SSD-1000 provides a fine balance of superb imaging and ergonomic design, well suited for a wide range of clinical examinations.'