Practical Panoramic Imaging
Incorrect Head Orientation

There are three possible planes in which the patient’s head may be positioned incorrectly: 1) Horizontal, 2) Vertical and 3) Anteroposterior. Incorrect positioning in each plane produces characteristic effects. Of course, there is the possibility of multiple errors in more than one plane – this will produce multiple and sometimes compounding effects and, in this instance, have are referred to as “compound” errors. The analysis of positioning errors therefore involves stepwise recognition of the radiographic features associated with each planar discrepancy.

Horizontal plane discrepancies – Essentially alter the position of the teeth and jaws on one side relative to the path of the effective rotation center and x-ray beam projection. The two possible options are that the patient is a.) twisted with respect to the machine, or b.) that their head is tilted. Both result because the midsagittal plane of the patient is not correctly aligned at the time of exposure. This can occur if the patient “follows” the receptor during exposure and move off-center.

• This error can be prevented by ensuring the midsagittal reference line of the panoramic unit coincides with the patient’s midline and that this line is perpendicular to the floor. Prevention of patient movement can be facilitated by adjustment of the lateral head supports to stabilize the patient and prevent movement during exposure.
• The principle effect of mal-positioning the patient is to offset more lateral and posterior structures, like the posterior dentition and ramus, with respect to the focal trough and x-ray beam projection.

Twisting – The most obvious image effects from the patient “twisting” within the machine are anatomic. Most noticeably:

1. The width of ramus on one side reduces (closer to the film) and becomes closer to the spine.
2. The width of the ramus on other side increases (farther away) and is further away from the spine – it may also be off the image.
3. The conchae on the side opposite the twisting are more pronounced.
4. The maxillary sinus and nasal fossa of the same side as the twisting become more noticeable.

While the anterior teeth remain relatively normal, there are two secondary effects on the dentition:

1. The first is that tooth size increases posteriorly on the side opposite to the direction of head tilt and,
2. Secondly, there appears to be increased overlapping of contacts on the opposite side of the tilt.

Tilting – The principle effect of tilting the patient is to create artifacts in the dentition and ramus superoinferiorly. The most obvious image effects are also anatomic. Most noticeably:

1. The lower border of the mandible slopes markedly on the side to which the head is tilted.
2. The mandible also appears elongated and tilted up.

The effects of tilting on the dentition include:

1. A reduction in the size of the teeth on the tilted side.
2. A greater overlap of the teeth on the opposite side.
3. Canting (sloping) of the occlusal plane towards the tilted side.

Vertical plane discrepancies – Essentially alter the relative position of the occlusal plane of the teeth and condyles of the mandible. The possible options are that the patient’s chin positioned too far up, too far down or that it is not positioned on the chin rest (when this is used to position the patient). Vertical errors occur when the patient’s head is incorrectly positioned superiorly inferiorly in the machine. The instructions in the manufacturer’s manual may vary in which plane is used to adjust the patient’s head up or down. Prevention of this error can be accomplished by ensuring that the patient’s horizontal reference line is parallel to the floor or the lateral reference markers.

• Head/chin tilted too high – The first possibility is that the patient’s head is positioned too high or tilted up.

1. 1. Most noticeably, this produces a frown configuration of the occlusal plane.
   2. The hard palate is superimposed over the maxillary teeth apices.
   3. The TMJs are pushed posteriorly and in many cases are projected off the sides of the image.
   4. The nasal cavity and other superior structures are blurred and out of focus.
   5. The maxillary anterior teeth may appear elongated and fuzzy.

• Head/chin tilted too low – The second possibility is that the patient’s head is positioned tilted too far down. The principle effect of tilting the chin down is to position more of the maxillae into the focal trough, align the maxillary teeth and to bring less of the lower anterior mandibular area into the focal trough. The anatomic effects of positioning the head too far down can be severe and may necessitate retaking the radiograph.

1. 1. Most noticeably, this produces a grin or “Jack-O-Lantern” configuration of the occlusal plane.
   2. The TMJs are positioned higher and in many cases are projected off the top of the image.
   3. The hyoid bone comes into the doubling diamond and forms a single widened line. The hyoid may superimpose over the lower border of the mandible.
   4. The anterior mandible is usually widened and out of focus.
   5. The mandibular anterior teeth may display pronounced foreshortening and appear out of focus.

• Chin not on chin rest – The third possibility is that the patient’s chin is lifted from the chin rest. This is usually because the initial height of the machine is lower than the height required for the patient. Often a patient will stoop to enter a panoramic machine but once they are positioned and immediately before exposure will straighten themselves up.
  
  The main visual effect of the chin being lifted from the chin rest is to create an image with a shift of anatomic structures superiorly. This may result in the top of the sinus and the condyles being cut off.

Anterioroposterior plane discrepancies – Essentially alter the position of the teeth, especially the anterior teeth in the focal trough. The two possible options are that the patient is positioned either too far forward or too far backward.

Too far forward – Anterior positioning of the patient too far forward occurs either due to patient slipping forward, sucking the bite block or not using a bite block.

Prevention of this error first necessitates that a bite block is used; secondly it requires that the patient’s anterior teeth are placed in an end-to-end position in the bite block. Prevention of subsequent patient movement can be aided by adjustment of the forehead support, when available, to prevent the patient from sliding forward.

The effect of positioning the patient too far forward is to position structures that are normally within the focal trough, like the anterior dentition, further anteriorly and out of focus and to bring more posterior structures, like the spine, nasal fossa and maxillary sinus into the focal trough.

1. Most noticeably, spine is superimposed over the ramus bilaterally.
2. The anterior teeth are narrowed in width on both arches and out of focus.
3. Severe overlapping of the teeth, particularly the premolars.

Prevention of this error, as with anterior positioning errors, necessitates that a bite block is used; secondly it requires that the patient’s anterior teeth are placed in an end-to-end position in the bite block.

The principle effect of positioning the patient too far back is to position structures that are normally within the focal trough, like the anterior dentition, further posteriorly and out of focus.

1. Most noticeably, severe ghosting of the ramus and mandible.
2. The anterior teeth are widened on both arches and out of focus.
3. Blurring of the turbinates (nasal conchae) across the sinus.
4. Widening of the entire image, cutting off posterior structures.