Both textbooks describe an SMV for the sphenoid sinus, but it leaves ARRT's sinus list on March 1, 2027

Bontrager’s and Merrill’s both describe an SMV (submentovertical, also called the full basal) that shows the sphenoid sinus. If you test on or after March 1, 2027, it’s no longer on ARRT®‘s sinus list. Check your test date before spending time on it.

What changes on March 1, 2027?

Sinus projection	Through Feb 28, 2027	From Mar 1, 2027
Lateral, horizontal beam	Listed	Listed
PA axial (Caldwell), horizontal beam	Listed	Listed
Parietoacanthial (Waters), horizontal beam	Listed	Listed
Submentovertex (full basal), horizontal beam	Listed	Not listed

The SMV of the skull stays on the 2027 list. The outline lists projections only. It doesn’t say which one is “best” for a sinus. See our 2027 changes page for the wider update.

Is the SMV really the best, or is the lateral better?

The textbooks don’t crown one projection. Bontrager’s lists the sphenoid first among the anatomy shown on its SMV, and files that SMV as a special projection, not a routine one. Merrill’s titles its SMV for the ethmoidal and sphenoidal sinuses.

The lateral also shows the sphenoid, though. Bontrager’s and Merrill’s both show all four sinus groups on it, and Merrill’s says the sphenoid is the group best demonstrated on that view. So we no longer call the lateral a wrong answer. Both books also offer the open-mouth Waters as an alternative when a patient can’t manage the SMV, though it isn’t on either ARRT list.

How do you position the sinus SMV?

1. Seat the patient upright if possible, to show air-fluid levels.
2. Raise the chin and hyperextend the neck. Don’t tuck it. On a trauma patient, don’t attempt this until a cervical spine fracture or subluxation is ruled out. Bontrager’s gives that warning on its skull SMV, which uses the same head position.
3. Rest the head on its vertex, with the IOML parallel to the receptor.
4. Keep the midsagittal plane perpendicular to the midline of the grid, with no rotation or tilt.
5. Direct the CR perpendicular to the IOML, and suspend respiration.

The books describe the same centering in different ways. Bontrager’s goes midway between the mandibular angles, 4 to 5 cm (1.5 to 2 in) below the mandibular symphysis. Merrill’s goes through the sella turcica, about 1.9 cm (3/4 in) anterior to the EAM.

If the neck won’t extend enough, angle the tube to keep the CR perpendicular to the IOML. Merrill’s warns that air-fluid levels may then be harder to show, because the beam is no longer horizontal. The position is uncomfortable, so set your factors first.

Compare the sinus SMV with the sinus lateral. Our free skull, facial bones and sinuses chapter and the Procedures guide cover the routine series, and you can drill it with the head, spine and pelvis questions.