Radiographic Procedures · ARRT 2025
Bony Thorax
The RAO sternum and its breathing technique, true vs false vs floating ribs, the rib decision table, and above or below diaphragm breathing rules for the ARRT Radiography exam.
Overview
Bony Thorax covers the sternum, the sternoclavicular joints and all 12 pairs of ribs, and nearly every question is a decision about position and breathing. The sternum is about 7 inches long in three divisions (manubrium, body, xiphoid process) and sits directly in front of the thoracic spine, so a straight PA barely shows it. The fix is a 15 to 20 degree RAO, which slides the sternum left of the spine onto the uniform heart shadow, paired with an orthostatic breathing technique: low mA and a 3 to 4 second exposure so shallow breathing blurs the lungs while the bone stays sharp.
Anterior landmarks map to vertebral levels asked word for word: sternoclavicular joints at T1, jugular notch at T2-T3, sternal angle at T4-T5, xiphoid tip at T9-T10. Rib classification: ribs 1 to 7 are true, 8 to 12 are false, and 11 and 12 are floating. Every rib forms a costovertebral joint, but only ribs 1 to 10 form costotransverse joints.
The rib routine follows one rule: place the area of interest closest to the receptor and rotate the spine away from it. Posterior ribs get an AP plus a posterior oblique, anterior ribs get a PA plus the opposite anterior oblique, and both rib obliques use 45 degrees. Breathing splits at the diaphragm: expose upper ribs erect on inspiration so ribs 1 through 9 clear the dome, and lower ribs supine on expiration so ribs 10 through 12 show below it.
SC joint obliques use only 10 to 15 degrees and demonstrate the downside joint. Flail chest (adjacent ribs broken in two or more places) is imaged erect when tolerated, and rib trauma routinely adds a PA and lateral chest to rule out pneumothorax. Procedures carries 72 of the 200 scored questions on the exam.
What you’ll learn in this chapter
The 29 lessons in this chapter break down as follows. The full lesson content is unlocked when you start a free account.
Bony Thorax
- Bony Thorax: Ribs, Sternum & SC Joints
Anatomy
- The Sternum
- Landmarks and Their Vertebral Levels
- Ribs: True, False and Floating
- Anatomy of a Typical Rib
- Quiz
- Joints of the Bony Thorax
Technique
- Sternum Technique, and Why RAO
Sternum
- RAO Sternum
- Quiz
- Lateral Sternum
SC joints
- Sternoclavicular Joints
- Quiz
Ribs
- Above or Below the Diaphragm
- Quiz
- The Rib Decision Table
- Quiz
- AP and PA Rib Projections
- Axillary Ribs
Clinical indications
- Clinical Indications
Image critique
- Critiquing a Bony Thorax Film
- Quiz
Summary
- Every Projection in One Place
Recap
- What to Carry Out of This Chapter
- Quiz
- Quiz
- Quiz
- Quiz
- Quiz
Key terms in this chapter
These are the 8 terms most likely to appear on the ARRT registry from this chapter. Use them as a flashcard pre-quiz.
- RAO Sternum
- The routine sternum oblique at 15 to 20 degrees, shifting the sternum just left of the spine onto the homogeneous heart shadow. A deep barrel chest needs about 15 degrees, a thin chest about 20.
- Orthostatic (Breathing) Technique
- Low mA with an exposure of at least 3 seconds while the patient breathes shallowly. Lung markings blur over the sternum while the bony margins stay sharp; not used on young pediatric patients.
- True, False and Floating Ribs
- Ribs 1 to 7 reach the sternum by their own costocartilage (true); ribs 8 to 12 do not (false); ribs 11 and 12 also float, with no costocartilage or anterior attachment at all.
- Costovertebral vs Costotransverse
- The rib head meets a vertebral body on all 12 ribs (costovertebral). The rib tubercle meets a transverse process only on ribs 1 to 10 (costotransverse), so ribs 11 and 12 lack that joint.
- Rib Positioning Rule
- Place the area of interest closest to the image receptor and rotate the spine away from it. Right posterior ribs take an AP plus RPO; left anterior ribs take a PA plus RAO.
- Above vs Below the Diaphragm
- Upper ribs are exposed erect on inspiration so ribs 1 to 9 clear the dome; lower ribs are exposed supine on expiration to show ribs 10 to 12 as a minimum.
- Sternal Angle
- The palpable ridge where the manubrium meets the sternal body, at the T4-T5 level. The second costal cartilage joins the sternum here, which anchors rib counting from the front.
- Flail Chest
- Fracture of adjacent ribs in two or more places from blunt trauma, threatening chest wall instability and underlying pulmonary injury. Imaged erect if the patient's condition permits.
Sample practice question: Thorax and Abdomen
One free sample from the 75-question Thorax and Abdomen bank. See the format, the rationale style, and the difficulty before you sign up.
On a properly positioned and exposed PA chest radiograph in an adult, how many posterior ribs should be visible above the diaphragm to indicate adequate inspiration?
Show answer and rationale
A, Incorrect: 8 posterior ribs typically indicates underinspiration. Repeat with full inspiration.
B, Correct: Correct. The standard is at least 10 posterior ribs visible above the diaphragm on a properly inspired adult PA chest. Underinspiration (only 8 visible) compresses lung markings and may mimic pulmonary disease.
C, Incorrect: Counting anterior ribs is less reliable because they're more variable and angle differently. Use posterior ribs as the standard.
D, Incorrect: Costophrenic angle visibility is part of quality assessment but does not specifically indicate inspiration adequacy.
Hands-on
Practice the positioning
Open the Positioning Lab to drill body position, central ray, anatomy, and common errors for each projection in this chapter.
- Chest PA Upright PA chest. SID 72". Inspiration on second breath.
- Chest AP Anteroposterior upright chest projection. SID 72".
- Chest Lateral Left or right lateral upright chest projection. SID 72".
- Chest Lateral Decubitus Patient on side with horizontal beam. SID 72".
- Chest Dorsal Decubitus Supine chest with horizontal beam. SID 72".
- Lungs AP Axial Lordotic AP lordotic for pulmonary apices. Patient leans back ~30°. SID 72".
- Ribs Posterior AP AP posterior ribs, erect. SID 40". Breathing varies by location.
- Ribs Anterior PA PA anterior ribs, erect. SID 40". Full inspiration.
- Ribs AP Oblique AP oblique ribs, 45-degree. SID 40". Full inspiration.
- Ribs PA Oblique PA oblique ribs, 45-degree. SID 40". Full inspiration.
- Sternum PA Oblique RAO PA oblique sternum (RAO), 15-20 degrees. SID 30". Breathing technique.
- Sternum Lateral Lateral sternum, erect. SID 72". Arms raised.
- Sternoclavicular Joints PA PA sternoclavicular joints. SID 40".
- Sternoclavicular Joints PA Oblique PA oblique SC joints, 15 degrees. SID 40".
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Frequently asked questions
What does the ARRT Radiography Radiographic Procedures category cover?
Bony Thorax covers the sternum, the sternoclavicular joints and all 12 pairs of ribs, and nearly every question is a decision about position and breathing. The sternum is about 7 inches long in three divisions (manubrium, body, xiphoid process) and sits directly in front of the thoracic spine, so a straight PA barely shows it. The fix is a 15 to 20 degree RAO, which slides the sternum left of the spine onto the uniform heart shadow, paired with an orthostatic breathing technique: low mA and a 3 to 4 second exposure so shallow breathing blurs the lungs while the bone stays sharp.
How many lessons are in the Bony Thorax chapter?
This chapter contains 29 lessons across 10 sections, plus a knowledge-check quiz at the end. The full lesson content is unlocked with a Premium subscription. The free tier includes 3 complete chapters.
Is this chapter aligned with the ARRT 2025 Content Specifications?
Yes. Every chapter on this site maps directly to the ARRT Radiography Content Specifications effective 2025. This chapter falls under the Radiographic Procedures domain of the official ARRT exam blueprint.