Reduction of power, e.g. due to passage through a medium or electrical component. Attenuation in electrical systems is commonly expressed in dB.

Quick Overview

Two types of audio-frequency problems are possible:
1. Modulation of the MR signal at an audio rate
2. Audio signal component at digitizer input
Problem 1 looks like ghosts, weak copies of the real image, displaced along the phase encoding direction. The number and intensity of the ghosts depends upon the relationship between the period of the audio modulation and the repetition time.
Problem 2 shows up as lines or spots at the appropriate points along the frequency direction. If there is no correlation between the audio period and TR, lines are generated or discrete spots occur.

Both problems can be lessened by use of AC-line synchronization (line trigger).

Aurora Imaging Technology, Inc., a private company, is located in North Andover, Massachusetts. As a leading innovator in the breast imaging industry, the company provides with its Aurora System the detection, diagnosis, biopsy and treatment of breast cancer. Aurora Imaging Technology Inc. develops and manufactures the Aurora® 1.5T Dedicated Breast MR System, the first and only FDA approved MRI system designed specifically for breast imaging.

MRI Scanners:

From Aurora Imaging Technology, Inc.;
The Aurora® 1.5T Dedicated Breast MRI System with Bilateral SpiralRODEO™ is the first and only FDA approved MRI device designed specifically for breast imaging. The Aurora System, which is already in clinical use at a growing number of leading breast care centers in the US, Europe, got in December 2006 also the approval from the State Food and Drug Administration of the People's Republic of China (SFDA).
'Some of the proprietary and distinguishing features of the Aurora System include: 1) an ellipsoid magnetic shim that provides coverage of both breasts, the chest wall and bilateral axillary lymph nodes; 2) a precision gradient coil with the high linearity required for high resolution spiral reconstruction;; 3) a patient-handling table that provides patient comfort and procedural utility; 4) a fully integrated Interventional System for MRI guided biopsy and localization; and 5) the user-friendly AuroraCAD™ computer-aided image display system designed to improve the accuracy and efficiency of diagnostic interpretations.'

Automatic bolus detection is used to trigger the begin of the MRI scan with the time the contrast agent reaches the region of interest. The acquisition process is started once the signal is increased in this region. There are similar methods used by the scanner manufacturer (see MRI Acronyms for Automatic Bolus Detection). After injection of the contrast agent the region of interest is monitored (e.g. with a spin echo or gradient echo sequence). When the signal increases the scan is automatically triggered or the operator is informed.

See also Abdominal Imaging, Bolus Injection, Fluoroscopic Triggering, Care Bolus, and Bolus Tracking.