Abstract
Using the HITACHI craniocervical CT scanner, we devised a method to take direct coronal head scans with the patient in a sitting position. The scanner takes two simultaneous adjacent slices, 0.5 or 1.0 cm thick, in a scanning time of 3min 40 sec. The image is reconstructed on a 256×256 matrix, displayed on black-and-white and color TV monitors, and recorded by polaroid film. The X-ray generator is operated at 120 kV and 30 mA.
The scanner has a large and accessible scanning region. The accessibility of the scanner permits the patient to be scanned easily in a coronal plane while in a sitting position. In patients able to sit, coronal scans are easier to obtain with the patient seated rather than in a prone or supine position. No excessive flexion or extension of the head and neck is necessary. Coronal sections can be readily obtained at any anterior or posterior cranial levels by this method.
The level of the coronal slice is measured and decided through the observation window which is located at the lateral side of the scanner. The standard point and the standard line are the external auditory meatus (the upper edge = 0 point)and the Reid's base line. Coronal sections through the clivus and the parietooccipital region can be readily obtained at the position of 0 ?? 1.5 cm anterior and 0 ?? 0.5 cm posterior from the external auditory meatus, and75 ?? 90 degrees from the Reid's base line. Coronal sections through the foramen magnum and occipital region can be readily obtained at the position of 0.5 ?? 4.5 cm posterior from the external auditory meatus, and 60 ?? 75 degrees from the Reid's base line.
As a result, coronal sections give not only vertical planes of the lesions, but also provide precise relationships to the tentorium, tentorial notch, clivus, petrous pyramid, foramen magnum and upper cervical regions. They are very important in determining the attachment of the tumor, their location, extent and the relationship with neighboring structures of lesions. The addition of contrast-enhanced coronal CT often demonstrated the lesion to a better advantage. Furthermore, three dimensional orientation method by transverse and coronal CT (biplane CT) has proven to be the most important technique in neurosurgical planning of posterior fossa tumors.
