For a pluri-directional system, evaluate:
(b) The degree of exposure overlap.
Motions should be closed (no open gaps).
(d) Any overlap should not exceed 20 degrees.
d. Record the information on the data form.
6-17. PREVENTIVE MAINTENANCE
The uniformity of exposure test should be performed:
a. At six-month intervals.
b. After any service performed on the tomographic drive mechanism.
c. If a mechanical problem is suspected.
6-18. CORRECTIVE MAINTENANCE
a. Perform a retest before proceeding with corrective maintenance.
b. Call a service representative or engineer if the retest reveals:
Large non-uniformities of density.
Waviness of trace.