Ultrasound examination: Positioning techniques and equipment

Corresponding to the guidelines in the MKP, the ultrasound examinations were conducted within the first week of life and/or between the sixth and eighth week. All examinations were carried out by one member of the research team (AW). The collected images were saved for subsequent evaluation and all necessary data were entered into an Excel table. This file contained all primary parameters relating to the evaluability of images. The following secondary parameters were also collected:

Participant number

Group

Parents’ assistance

Sex

Age in days (birthdate)

Duration of the examination (< 5 min; 5–10 min, 10–15 min, 15–20 min)

Premature birth

Babies assigned to Group 1 were examined according to Graf’s principles using a foam shell [2]. This shell consists of a pillow-like head section and a lower fixating part with a lengthwise gap (Fig. ​(Fig.1)1) which can be spread apart to position the baby (Fig. ​(Fig.2).2). A cloth diaper is placed on the fixation device, allowing it to hang into the gap like a hammock. Depending on the baby’s weight, the diaper can be loosened or tightened to the needs of the examining doctor, just so the baby’s hip slightly protrudes the edges of the fixation device. The baby’s legs should not be stretched to promote better fixation and stay in their natural slightly flexed position to avoid excessive rotation of the hip. The knee joint should not protrude from the fixation device, so as not to turn the greater trochanter dorsally and, hence, hinder the scanning process.

Graf’s fixation device as used in Group 1

Graf’s fixation device as used in Group 1 (with baby in it)

According to Graf’s original principles [2], the examiner is supposed to conduct the ultrasound scan in a standing position and hold the fixated probe in both hands. In our setting, the examinations were conducted in a sitting position with the probe only being manually fixated by the examiner. This was due to empirical experience and the expectation that no difference in image quality would result from this approach.

In Group 2, the newborns were placed on the examination couch and gently rolled over to a sideways position. The parent was advised to hold the baby and its legs to prevent it from rolling over (Fig. ​(Fig.33).

Manual fixation of an infant as applied in Group 2

In the Excel table the examining doctor indicated whether help was needed from parents during the scanning process due to agitation or restlessness of the baby. This assistance mainly included manual fixation of the legs and the upper body to prevent rotation.

Two ultrasound scanners were used in the course of this study: the Ambisea ComboScan HD, manufactured in 2010, an all-in-one colour Doppler scanner with integrated PC and LCD and Ultra-frequencies between 2 and 10 MHz [15] and the Alpinion E-CUBE 9 DIAMOND, manufactured in 2012, with a single-crystal transducer technology and Ultra-frequencies between 1 and 17 MHz [16].