TOPOGRAPHICAL LANDMARKS

• Provide useful, palpable guide points for radiographic positioning

• Helpful when well-collimated radiographic images are required of specific vertebrae.

• Variations are seen between patients for different body habitus, but these landmarks represent the anatomic relationships of an average patient

Cervical landmarks

• Mastoid process (tip) = level of C1. About 1 inch (2.5 cm) below the level of the EAM (external acoustic meatus).

• Gonion = level of C3

• Thyroid cartilage (Adam’s apple) is at the approximate level of C5. Varies between C4-C6

• Vertebra prominens = C7

Thoracic landmarks

1. Jugular (suprasternal) notch = T2 or T3 T1 is about 1.5 inches (4 cm) superior to the level of the jugular notch.

2. Sternal angle = T4 and T5 about 2 inches (5 cm) inferior to the manubrial notch.

3. T7 = 3 to 4 inches (8 to 10 cm) inferior to the jugular notch or 7 to 8 inches (18 to 20 cm) below the vertebra prominent

4. Xiphoid process (ensiform) = T9-10

Lower Spine landmarks

1. Superior margin of the symphysis pubis= the prominence of the greater trochanter

2. Anterior Superior Iliac Spine (ASIS) = the first or second sacral segment (S1-S2)

3. Iliac crest = the junction of the fourth and fifth lumbar vertebrae (L4-L5)

4. Lowest margin of the ribs or lower costal margin = L2-L3. E. The xiphoid tip is approximately at the level of T9-T10.

Cranial Topography

• The superciliary ridge (arch) is the ridge or arch of bone that extends across the forehead directly above each eye. Slightly above this ridge is a slight groove or depression, the SOG.

NOTE: The SOG is important because it corresponds to the highest level of the facial bone mass, which is also the level of the floor of the anterior fossa of the cranial vault.

• The glabella (glah-bel′-ah) is the smooth, slightly raised trian gular area between and slightly superior to the eyebrows and above the bridge of the nose.

• The nasion (na′-ze-on) is located at the junction of the two nasal bones and the frontal bone.

• The tragus, the small cartilaginous flap that covers the opening of the ear.

• TEA refers to the superior attachment of the auricle, or the part where the side frames of eyeglasses rest. This is an important landmark because it corresponds to the highest level of the petrous ridge on each side

• Canthi (kan′-thi) = junctions of the upper and lower eyelids.

• Inner canthus (kan′-thus) = is where the eyelids meet near the nose

• Outer canthus = the more lateral junction of the eyelids

• The superior rim of the bony orbit of the eye is the SOM the inferior rim is the infraorbital margin (IOM).

• Midlateral orbital margin, which is the portion of the lateral rim that is near the outer canthus of the eye.

• These three landmarks contribute to the base of the orbit.

• An average difference of 7° to 8° exists between the angles of the OML and IOML.

• There is also an approximate 7° to 8° average angle difference between the OML and GML.

• Knowing the angle differences between these three lines is helpful in making positioning adjustments for specific projections of the cranium and facial bones.

Abdominal Quadrants and Regions

FOUR QUADRANTS

NINE REGION