How To Focus? -Diagnostic Ultrasound (Sonography)

Unlike other dignostic procedure, ultrasound study needs the presence of an expert-either during the process or the expert must visualize a live recaording to come to a correct focus diagnosis still photographers or film are inadequate alone to surve the purpose. 

It is essential for the operator to focus the incident sound beam in the proper plane, through proper acoustic window for optimum information. 

For pelvis studies done abdominally, an Optimally full urinary bladder is mandatory it helps in two ways-

1. It rise to become an abdomino-pelvic structure thus pulling the uterus, fallopian tubes and ovaries along with it. 
2. It act as an acoustic window to study the posteriorly placed organs. About 2-3 glasses of water (400-500 ml) drunk 2hours prior to scan is sufficient. 

Points How to focus? (Focusing) 

1. Hold transducer firmly. 
2. At the onset, locate a mark on the house of transducer, given by the manufacturers/company to signify longitudinal axis. 
3. Place thumb on that mark. 
4. Expose the lower abdomen, adequately (many a study has been incomplete due to faulty exposure ) up to public hairline. Apply an even layer of coupling gel on this area with a sponge. 
5. Place transducer in the midline in longitudinal axis little above the public hairline and give sufficient downward pressure. 
6. If the bladder is optimally full the uterus comes into view. This is the uterus in longitudinal axis.  
7. At time the uterus may be slightly deviated on the right or left of midline. In such as a case, the transducer might have to be angled towards the right or left midline 
8. After the longitudinal study is completed, the transducer is turn through the structures to be studied

Here's let assume the pelvic structures to be the furniture in a dark end room whose doors and windows are all locked and we are trying to look at them through a hole in the wall with a help of beam of light of a hand held torch. 

In such case we would turn the beam through an arch to look at the furniture inside. To look at an object on the left the torch would have to be held in a right to left direction and the beam would pass through structures of the left of midline. 

Similarly, for right sided observation the beam would have to be passed from the left to the right. 

   So, once the transducer is turned to let the focus beam travel transversely rolling motion of the operator's wrist allows the modulation to rotate its incident beam for study of structures. 

It is advisable to avoid:

1. Over fullness of urinary bladder- which prevents proper study epecially for ovarian folliculometry, study of internal os, cervical canal and placenta praevia. 
2. Too thick layer of coupling gel. 
3. Leaving the transducer smeared with gel after a study. 

At the end! 

At present pelvic study is done only by vaginal route. For transvaginal study the endocavitory transducer is covered with a fresh condom, for hygienic insertion, better picture clarity (focus), to prevent cross infection amongst patients, before every study and cleaned with a soft cloth after-wards. Coupling gel is placed within the condom not on it. 

Operator must wear sterile gloves. In transabdominal aproach-most sonograms are preformed using a 5.0 MHz or 3.5 MHz transducers.