c. Oblique Trunk Positions. For full field coverage (FFC) obliques, the
marker corresponds to the side of the body. For oblique projections, the technologist
must first decide whether to do a FFC radiograph or a restricted conefield (CF) radiograph.
In an FFC, the central ray is not coned down so that the entire film is exposed. In a
restricted CF, the CR is coned down so that only a portion of the film is exposed. The
requesting physician might, for example, request a hip series, in which case it would be up
to you to determine if you are going to do a full pelvis or a right or left AP hip depending on
the entry in the reasons requested block. (In some cases, of course, the physician might
specifically request both views.) Once you have determined which views to take, you will
have to prepare the film accordingly with the correct letter marker(s). For the pelvis view,
which is FFC, both hips will appear in the radiograph. For an FFC, the letter marker must
correspond to the side of the body. Thus, you could label the film with either the L marker
near the position on the film corresponding to the place where the left hip will be visualized.
Or, you could use the R marker, in which case, you would place it near the portion of the film
where the right hip will be visualized. (You don't need to place both markers on the film because
one identifier suffices to provide the positional orientation for both sides of the image.)
d. Oblique Trunks (Restricted Conefield ). For an oblique trunk with a restricted
entered, the letter marker corresponds to the part demonstrated (figure 4-32). In an AP
hip, a restricted CF radiograph, the collimator is coned down to demonstrate only one
hip. Therefore, the LM you select to identify the film must correspond to the hip being
demonstrated: R for the right hip or L for the left hip. You cannot use either marker, as
for a FFC radiograph (that is, using an L to indicate the left side of the right hip). If the
right hip is visualized in a restricted CF, you must use the R. If you mislabeled a right
hip radiograph with an L, you would mislead the radiologist and quite possibly
compromise the patient's treatment.
Figure 4-32. In his AP hip with a restricted CF, the letter marker (L) corresponds to the
hip being demonstrated.