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This is an imaging modality in diagnostic field which has a great potential to expand and will find many new horizon in near future. The principle of USG is that a sound wave of higher frequency generated by a transducer and received by another device, incorporated in same transducer, so that on analysis by computer of sound wave which has returned in different strength by absorption and reflection from various tissue surfaces we get graph, wave or images. Accordingly USG is divided into A) A mode, B) B mode, and C) M mode.

A-Mode: Also called as amplitude modulation is the most basic form of diagnostic Ultrasound. Here a single beam of ultrasound is analyzed. This helpful in determining the distance between transducer and the structures you want to evaluate. A scan is useful now mainly in ophthalmic practice.

B-Mode: In this mode signals are converted into dots, which vary in brightness depending on the strength of the returning echo. A stronger echo will display a brighter dot than a weaker echo. The depth of the reflector is displayed by the location of the dot. Multiple B-mode images may be displayed together to form a two dimensional B scan. Initial technology used to build a single image and it was termed as B - mode static scan. At present it is Real time B-scan. This provides a cinematic view of the area being evaluated by displaying a rapid series of images sequentially.

M-Mode: In this mode, a series of B-mode dots are displayed on a moving time base graphing the motion of mobile structures. M - Mode imaging forms the basis of echocardiography.

In routine USG we use Real time B -mode ultrasonography. For abdomen we use 3.5 MHz curvilinear probe (transducer). Whereas for transvaginal & transrectal one has to use 5.0 to 6.5 MHz probes. Higher the frequency of probe better is the resolution but smaller is the depth of penetration. In transvaginal the part you want scan is very near, about 1 -5 cm deep. So we can use high frequency probe to see the organ very clearly.

Patient preparation
Upper Abdomen (Gallbladder and pancreas scan) Patient should remain Nil By Mouth (NBM) 8 hours preceding the sonogram. Gall bladder should not contract. Distended GB gives better visualization.

Lower Abdomen (Pelvic Scan)
The bladder should be distended to provide a window for visualization of deep pelvic structures. (Fluid is friendly to USG). Patient should be instructed to drink enough fluid (about ¾ liter) to make their bladder slightly uncomfortable at the time of scanning.

View Obstetric Ultrasonography 1
View Obstetric Ultrasonography 2
View Obstetric Ultrasonography 1st trimester