Procedures · Positioning basics2 min read5-question check
Body habitus and centering
Big and broad means organs sit high and lateral; thin and slender means low and near the midline.
Four types
Body habitus is the general build of the body, and it predicts where the thoracic and abdominal organs lie. There are four types. Sthenic is the average build and the most common, about half of patients. Hyposthenic is a slightly thinner version of sthenic, roughly a third of patients. Asthenic is very slender, about one in ten. Hypersthenic is large and broad, about one in twenty. Standard centering points assume a sthenic patient.
Where organs sit
In a hypersthenic patient the thorax is broad and deep from front to back but short from top to bottom, the lungs are short, and the diaphragm sits high. The stomach and gallbladder are high and lateral, and the stomach lies almost transverse. The large intestine is high and spread to the periphery. In an asthenic patient everything is the reverse: the thorax is long and narrow, the lungs are long, and the diaphragm sits low. The stomach and gallbladder are low and near the midline, and the colon is low and folded on itself. Hyposthenic patients fall between sthenic and asthenic.
Changing the setup
Change two things for habitus: where you center and how you turn the receptor. For a hypersthenic chest, place the receptor crosswise so both costophrenic angles fit. For a hypersthenic abdomen, one lengthwise field often clips the sides, so use two crosswise images, one centered for the upper abdomen and one for the lower. For an asthenic chest, keep the receptor lengthwise and check that the long lungs and the costophrenic angles are included. For the stomach, center higher for hypersthenic patients and lower for asthenic patients.
In practice
Obliquity follows the same logic. For oblique stomach and duodenum projections, such as the RAO and LPO, hypersthenic patients usually need more rotation, because the stomach lies high and transverse, and asthenic patients need less, because the stomach hangs low and nearly vertical near the midline. A sthenic patient falls in between, at about 45 degrees. Always palpate landmarks and check the first image rather than guessing from size alone.
Clinical Example
A tall, very thin patient arrives for an upper GI. Knowing the stomach sits low and near the midline, you center lower than your usual sthenic point, then check the scout image. The whole stomach is included on the first try with no repeat.
Common Mistakes
- Using sthenic centering on every patient and clipping the diaphragm or the bladder.
- Placing a hypersthenic chest lengthwise and cutting off the costophrenic angles.
- Reversing the rule and centering low for a hypersthenic stomach.
- Opening the collimation wide instead of using a second receptor.
Why It Matters
Matching the setup to habitus prevents clipped anatomy and repeat exposures. The registry describes a patient's build and asks where an organ lies, how to orient the receptor, or how to adjust centering or obliquity.
Key Relationships
- Sthenic is most common; hypersthenic is least common
- Hypersthenic: high diaphragm, organs high and lateral, stomach transverse
- Asthenic: low diaphragm, organs low and medial
- Hypersthenic chest: receptor crosswise; hypersthenic abdomen: two crosswise images