Introduction to Radiographic Interpretation

Question 1

What is a Roentgen sign?

Answer 1

fundamental unit for assessing the accuracy of an imaging study —> visual cue that represents a pathologic change

Question 2

What is radiographic sensitivity, specificity, and accuracy?

Answer 2

SENSITIVITY = (TP/TP+FN) x 100 = predicts patients with disease

SPECIFICITY = (TN/TN+FP) x 100 = predicts patients without disease

ACCURACY = total true results divided by total true + false results = ability to truly diagnose a disease

Question 3

What is the cone of certainty?

Answer 3

a non-specific change cannot help reach a specific diagnosis, but combining various findings can add value and narrow the scope of diagnosis

Question 4

What are the 6 Roentgen signs?

Answer 4

1. size - ratio to another structure (vertebrae) or relative to other anatomy
2. shape - sharp, rounded, flattened, angular; round, oval, lobular, fusiform, pedunculated
3. number - liver lobes, kidneys, lesions, organs affected
4. position/location - lesion/organ, displacement
5. margin/contour - irregular and ill-defined (malignant), sharp and well-defined (less concerning)
6. opacity - soft tissue and fluid-filled masses cannot be differentiated, mineralization

How are these different from expected/known normal radiographic appearances? Sum of all of these signs is most important

Question 5

What are the 5 fundamental radiographic opacities from radiolucent to radiopaque?

Answer 5

1. gas
2. fat
3. fluid/soft tissue
4. bone/mineral
5. metal

Question 6

How does cortical and medullary bone opacity compare?

Answer 6

CORTICAL = very dense, more radiopaque

MEDULLA = contains trabeculae and fat, more radiolucent

Question 7

What is summation?

Answer 7

when objects in different planes are superimposed, the resultant opacity represents the degree of X-ray absorption by all of the superimposed objects, even though the actual density has not changed

NOT IN CONTACT WITH ONE ANOTHER

Question 8

What is border effacement?

Answer 8

when 2 objects of the same opacity are in contact with one another, their borders cannot be distinguished

• cannot observe hepatic veins, fluid in bladder, or chambers of the heart
• (retro)peritoneal effusion, intestinal contents

Question 9

In what 5 ways should radiographic data be organized?

Answer 9

1. QUALITY CONTROL: Is the study complete? 3 views? Technique? Appropriate position? Artifacts?
2. DESCRIPTION: recognize and describe radiographic abnormalities; use Roentgen signs and a paradigm
3. CONCLUSION: What do the abnormalities mean? What value do we ascribe to each finding?
4. DDX: What diseases may cause the pattern of abnormalities we have found? How does this relate to Hx, clinical signs, and PE findings?
5. NEXT STEPS: more diagnostics, medications, biopsies, FNA, staging neoplasia, surgery

Question 10

What is a framing bias?

Answer 10

opposing answers to the same problem depending on how the problem is posed

• distracted by one or more pieces of historical information that may erroneously implicate a system
• dog with acute vomiting and client is worried they ate something: most likely FB, but still consider pancreatitis

Question 11

What is a confirmation bias?

Answer 11

you only see what you look for and recognize what you know

Question 12

What is satisfaction of search?

Answer 12

decreased vigilance for abnormalities after the first one is found

• there is often more than one abnormalities that do not have to do with chief complaint, but should still be noted

Question 13

What is availability bias?

Answer 13

judging probability of a diagnosis based on the ease with which it comes to mind

Question 14

What is inattentional bias?

Answer 14

missing things in plain sight due to unexpected location or nature

• most common when a diagnostic paradigm isn’t followed

Question 15

What is the main scheme of categorizing differential diagnoses?

Answer 15

Degenerative/developmental
Autoimmune/anomalous
Metabolic
Neoplasia/nutritional
Infectious/iatrogenic/inflammatory
Traumatic
Vascular

Question 16

What Roentgen signs are associated with distribution?

Answer 16

number and location

• helps prioritize Ddx

Question 17

What is homogeneity? Heterogeneity?

Answer 17

the opacity of a structure is uniform (if found in the GIT, it can suggest fluid, chyme, or foreign bodies rather than undigested food)

the opacity of a structure is non-uniform, commonly resulting from a complex process that involves gas and mineralization, or non-uniform ingesta in the GIT

Question 18

What does enlarged mean? Distended?

Answer 18

larger than it should be, usually in reference to other structures in a ratio

PATHOLOGY - when something is filled beyond its natural capacity, or normal distention of a filled bladder or stomach

Question 19

What is a filling defect?

Answer 19

in contrast studied —> signifies disruption in the normal opacification of a region of an organ

• upper GI series or excretory uropgraphy: presence of a mass or luminal structure (FB, urolith)

Question 20

What does mural mean? Luminal?

Answer 20

of or having to do with the wall of a structure or organ

channel within a tube —> lumen of GIT, ureters, urethra

Question 21

What are 3 characteristics of a good differential diagnosis list?

Answer 21

1. prioritized
2. succinct
3. based on pathophysiology