How does ultrasound penetrate the skull?
Bone does not transmit ultrasound well, so the study is carried out through natural “windows”: the temporal bone, the orbit and the foramen magnum. Through them, it is possible to assess blood flow in the middle, anterior and posterior cerebral arteries, as well as in the vertebral and basilar arteries. The method shows vascular spasm, stenosis, collateral circulation and vascular response to stress tests. Prescribed for headaches, dizziness, noise in the head, after a stroke and for suspected vascular insufficiency in the vertebrobasilar region. Limitation: in some patients, often older women, the temporal fenestra is impenetrable to ultrasound.
Why ultrasound is the first line method
Ultrasound does not use ionizing radiation, is fast, inexpensive, and provides images in real time. Therefore, it begins with the diagnosis of most diseases of internal organs, thyroid and mammary glands, blood vessels, joints and soft tissues.
A separate advantage is the ability to evaluate not only structure, but also movement: blood flow in the vessels, heart contractions, peristalsis, and fetal movements. Neither CT nor MRI in standard mode show this.
Ultrasound modes
- B-mode - a conventional two-dimensional gray scale image of the organ structure
- Dopplerography - assessment of the speed and direction of blood flow in the vessels
- duplex scanning - a combination of vessel imaging and blood flow analysis
- 4D - volumetric image in real time
What influences the quality of research
Ultrasound does not pass through air and does not pass well through dense bone tissue. Therefore, gases in the intestines interfere with examination of the pancreas, and the lungs and brain of an adult are inaccessible for examination. This explains the preparation requirements: diet and fasting study significantly improve visualization.
The second important factor is the doctor: ultrasound diagnostics largely depends on the experience of the specialist, since the image is assessed at the time of the examination.