Introduction to the angle of cranial CT scan.
1. Overview of cranial CT examination.
There are various methods of cranial CT examination, and the appropriate examination method should be selected according to the needs of the patient, so as to meet the requirements of clinical diagnosis, better show the whole picture and characteristics of the lesion, and reduce the X-ray radiation of the patient. Non-contrast CT scans mostly use non-spiral cross-sectional scanning. Cranial coronal scan is an option for better visualization of intracranial structures and lesions, suspected pituitary tumors, lesions near the base of the skull, and postcranial lesions.
2. Introduction to the angle of cranial CT examination.
The baseline scan is the starting line of the scan that best visualizes the lesion or some anatomical structure on the body surface or positioning image before a cross-sectional CT scan of the skull. Baseline CT cross-sectional scan of the brain: there were auditory eyebrow line (EML), auditory line (OML), and orbital line (RBL).
Listening to the eyebrow line (EML): The line between the midpoint of the outer ear hole and the arch of the eyebrow.
Auditorial line (OML): The line between the midpoint of the external ear hole and the outer canthus.
Orbital line (RBL). The line between the midpoint of the external auricular foramen and the inferior orbital border.
3. Application of cranial CT scan baseline.
Listen to the eyebrow line (EML).
It is better to show the fourth ventricle and basal ganglia (caudate nucleus head, lenticular nucleus, amygdala). The lens can be avoided during head scans in children, which is good for protection.
Orbital line (RBL).
It is beneficial to show the eye socket, middle cranial fossa, and posterior cranial fossa. Structures such as parallel or perpendicular pons, brainstem, medulla oblongata, and sellar region are better for the other two baselines. Although this line can pass through the entire orbit in its entirety, the optic nerve does not show as well as a scan parallel to the canthal line.
Auditorial line (OML).
CT of the head is often done with this line as the baseline for scanning. The upper part is at a 10° angle to the eyebrow line, and the lower part is at a 12° to 15° angle to the orbital line. It is better to listen to the eyebrow line than to the fourth ventricle, and not to hear the orbital line for the midbrain, pons, brainstem, and medulla oblongata. Therefore, in the actual scanth, the canthal line is between the two lines, so it can take into account the structure shown by the other two baselines.
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