CT values in orbital hydatid cyst.

The CT values of 15 cases of orbital hydatid cyst operated upon by the author were reviewed. It was found that hydatid cyst of the orbit has high CT value, contrary to the low CT value of nonorbital hydatid. This discrepancy was confirmed by an experiment using human skull and two balls simulating hydatid cyst. One ball was put in the orbit and the other in the cranial cavity. When the skull was CT scanned it was found that the orbital ball CT value was about five times higher than the cranial ball, in spite of the fact that both balls had the same content. It was concluded that the orbital bony pyramid is the cause of this high CT value in orbital hydatid. Hence it is recommended that an orbital lesion with a high CT value can be a hydatid cyst.