{"id":643,"date":"2015-04-22T18:31:53","date_gmt":"2015-04-22T23:31:53","guid":{"rendered":"http:\/\/test.pegasuslectures.com\/blog\/?p=643"},"modified":"2015-04-22T18:34:11","modified_gmt":"2015-04-22T23:34:11","slug":"quick-concepts-apparent-snr","status":"publish","type":"post","link":"https:\/\/www.pegasuslectures.com\/blog\/index.php\/2015\/04\/22\/quick-concepts-apparent-snr\/","title":{"rendered":"Quick Concepts: Apparent SNR"},"content":{"rendered":"

\"QuickConceptsSeries_Screen_FINALA previous \u2018Quick Concepts<\/a>\u2019 discussed the significance of signal-to-noise ratio<\/a> in ultrasound technology. Briefly summarized, sonographers and ultrasound professionals are trained to optimize signal strength relative to noise in order to produce good clinical or diagnostic data<\/strong>.<\/p>\n

Poor signal-to-noise ratio results in an inferior image quality.\u00a0 However, not all inferior ultrasound images are the result of poor signal-to-noise ratios.\u00a0 This leads to the discussion of \u201capparent<\/strong>\u201d versus \u201ctrue<\/strong>\u201d SNR.<\/p>\n

\"Graphical

Graphical Representation of Apparent SNR<\/p><\/div>\n

The distinction behind apparent signal-to-noise involves situations in which the system adjustments may be set inappropriately<\/span>. In these cases, the SNR may appear to be poor, even when the true SNR is relatively good.<\/em><\/p>\n

The quality of an ultrasound scan is dependent on the equipment<\/strong>, the patient<\/strong>, and the power to observe<\/span><\/strong> the results.\u00a0 Because of the inherent limitations of the human eye and ear, ultrasound systems employ \u201ccompression\u201d techniques to map the larger dynamic range of an ultrasound device into the significantly smaller dynamic range of an operator (or interpreter).<\/p>\n

\"Receive

Receive gain too high, creating poor apparent SNR<\/p><\/div>\n

In some circumstances, the signal is not mapped well into a range that we can see or hear.\u00a0 This will create imaging that APPEARS poor, when in fact it is simply mapped outside the viewer\u2019s detectable range.<\/span>\u00a0 This can happen in two ways.\u00a0 Either the receive gain can be set too high, which maps noise into the visible range, OR the receive gain can be set too low, resulting in a darker, weak image.<\/p>\n

In my outline of strategies to improve SNR, two of the strategies involved changing system settings, which is critical in discerning whether you are dealing with \u201capparent\u201d or \u201ctrue\u201d signal-to-noise challenges.<\/p>\n