The three anatomy planes are:
1) the horizontal plane which is perpendicular to the long axis of the patient.
2) the coronal (frontal) plane which is the vertical plane that divides the body in a ventral and a dorsal half.
3) the sagittal plane which is a plane that passes from posterior to anterior and divides the body in a left and a right half.
The probe is moved in order to display the best possible ultrasound image of the target structure on the monitor:
1) Translation: Parallel shift of the foot print of the probe while keeping a fixed angle between the probe and the skin surface.
2) Rotation: The probe is rotated around an axis which is perpendicular to the footprint. In this way the target structure can be visualised in two orthogonal planes.
3) Tilting: The probe is rotated around the long axis of the footprint of the probe.
4) Panning: The probe is rotated around the short axis of the footprint of the probe.
The ultrasound beam is equivalent to the image on the screen as seen on the picture on the right only when the orientation marker (OM) of the probe is pointing to the same side as the orientation indicator (OI) on the screen.
The image of a blood vessel on the ultrasound monitor represents a thin slice of tissue.
The size of the slice is determined by the profile of the ultrasound beam and can be described by height, width and thickness.
The ultrasound beam is approximately 1 mm in thickness in the focus zone for all probes.
Width is determined by the width of the foot print of the transducer.
Height can be changed by adjusting the image depth on the ultrasound system.
Parallel shifting of the probe back and forth and from side to side and rotating and tilting the probe allow you to capture the best possible cross sectional view of your target structure in the best possible position.
It is critically important to apply plenty of gel on the skin to facilitate acoustic coupling between the probe and the patient.
Normally, the orientation indicator (OI) on the monitor is placed in the top left corner of the screen. The exception is cardiac ultrasound where the OI is placed in the top right corner of the screen.
Conventionally, the orientation marker (OM) on the probe has to be oriented towards the patient’s right side – except for cardiac ultrasound – when scanning in the horizontal plane. When scanning in the frontal (coronal) plane or the sagittal plane, the OM has to be oriented cranially. In this way the OM always points towards the OI on the left side of the monitor – except for cardiac ultrasound.
The orientation of the probe can be checked by tapping a finger on one end of the gel covered foot print of the probe and watching the gel movement on the monitor. This is called the “finger-orientation-test”.
We recommend that the “finger-orientation-test” is performed routinely before every ultrasound examination.
The standard position of the patient is lying down, face up, with the arms along the sides and the ultrasound operator on the right side of the patient.
Sometimes, however, the hands have to be placed over the head or on the chest to expose the target region for scanning. Or the patient has to be turned on the side to facilitate cardiac scanning.
Align the monitor and your anatomical target in front of you, in such a way that you can scan and insert the needle ergonomically correct without turning your head or twisting your neck or your body.
The probe is fitted with an orientation marker (OM).
In the image on the right, the OM is indicated by a green arrow.
The OM facilitates the correct orientation of the probe on the patient.
The OM has to be oriented in correct relationship with the corresponding orientation indicator (OI) on the monitor.
There are basically two ways to hold the probe properly.
The screw driver grip:
With either the back or the palm of the operator hand placed on the patient during scanning.
The pencil or lipstick grip:
The grip on the probe is made with the thumb and index finger.
The third digit can be used to strengthen the stability of the grip on probe.
