Neonatal transcranial ultrasound
Ultrasound examination of the newborn brain is used to identify congenital developmental anomalies. A striking example of pathology is agenesis of the corpus callosum (агенезия мозолистого тела).
On sagittal and coronal scans, specialists evaluate brain structures. A characteristic radiological and sonographic sign of this condition is the absence of the corpus callosum in its typical anatomical zone, as well as the specific sign of radially diverging gyri — 'sunray' appearance.
Advantages and historical milestones of neuroimaging
The development of imaging techniques began with the creation of the first clinical CT scanner by Sir Godfrey Hounsfield. The historic EMI Mark I device was used exclusively for brain examinations and required immersing the patient's head in a special rubber water cap to compensate for density differences.
Main advantages of modern techniques:
- Obtaining data in unstable patients directly during resuscitation procedures.
- A significant reduction in radiation exposure compared to earlier counterparts.
- Improved spatial resolution and scanning speed.
Technological breakthrough: from slip-ring to MSCT
In the 1980s, the introduction of slip-ring technology allowed the tube to rotate continuously, reducing the scan time per slice to 1 second. Later, spiral scanning and multislice computed tomography (MSCT) were developed.
Modern multidetector systems (e.g., 64- and 320-slice) generate truly isometric voxels with identical dimensions in all planes. To process such data arrays, a complex computational method called z-interpolation is used, transferring spiral data into a single axial plane.
Scanning principles and detector design
CT scanners operate by rotating an X-ray tube that emits a fan-shaped beam of rays. Body tissues attenuate radiation unevenly depending on density, after which the transmitted rays are captured by a detector.
The detector design includes two main elements:
- Scintillator — absorbs X-ray quanta and converts them into visible light.
- Photodiode — captures this light and generates the final electrical signal.
Dual-source systems use two tube-detector pairs, providing ultra-short data acquisition times within 80–200 ms.
Briefly: answers to topical questions
What ultrasound signs are characteristic of agenesis of the corpus callosum?
The characteristic signs of agenesis of the corpus callosum on neonatal transcranial ultrasound include:
- absence of the corpus callosum in its typical location;
- the 'sunrays' sign — radially diverging gyri visualized on a sagittal scan.
What are the indications for neurosonography in newborns?
Indications for neurosonography in newborns include:
- prematurity;
- low Apgar score;
- dysmorphic features;
- seizures;
- suspected intracranial or intraventricular hemorrhage;
- craniosynostosis.
Neurosonography is also part of the recommended diagnostic panel for respiratory distress syndrome in newborns.
Through which acoustic windows is transcranial ultrasound performed in newborns?
Transcranial ultrasound of the brain in newborns is performed through the fontanelles, which serve as acoustic windows.
What pathologies, other than agenesis of the corpus callosum, are detected using neurosonography?
Neurosonography detects:
- intraventricular hemorrhage — echogenic material within the lateral ventricles;
- periventricular hemorrhagic infarction — a hyperechoic focus that in later stages may communicate with the lateral ventricle and lead to porencephalic cyst formation;
- periventricular leukomalacia — hyperechogenic periventricular white matter ("flares" or flares);
- ventriculomegaly;
- in congenital infections — calcifications, cysts, signs of ventriculitis, and intraventricular hemorrhages.
To remember the sign of corpus callosum agenesis, use the association: sun rays ('sunray') fan out from the center, like the gyri on a sagittal scan.
Class and exam questions
What is the main ultrasound sign of agenesis of the corpus callosum?
The main sign is the absence of the corpus callosum in the typical zone and the specific 'sunray' appearance, which represents radially diverging gyri.
What was the specific feature of the first EMI Mark I CT scanner?
It was used exclusively for brain examinations and utilized a special rubber water cap to smooth out the differences in radiation attenuation at the boundary between air and the skull.
What did slip-ring technology provide?
It allowed the X-ray tube to rotate continuously, thereby reducing the acquisition time for a single axial slice to 1 second.
What role do the scintillator and photodiode play in a CT detector?
The scintillator converts X-rays into visible light, and the photodiode transforms this light emission into an electrical signal for further computer reconstruction.
What else to study on this topic
- History of the development and introduction of CT at Massachusetts General Hospital (MGH)
- Principles of dual-energy CT and CT perfusion
- The 'flying focal spot' technology in MSCT
- Development of CT angiography (CTA) and 3D reconstruction methods
- The contribution of Allan Cormack and Godfrey Hounsfield, recognized by the 1979 Nobel Prize
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