RAD 324
Note: In this section, many anatomical labels are covered with a which means you are not responsible for these structures.
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CT/HU Numbers Based on Attenuation Coefficients
Air
Lung
Fat
Substance
Water
CSF
Blood
Muscle
Soft Tissue
Bone
HU
−1000
−500
−84
0
15
+30 to +45
+40
+100 to +300
+700(cancellous bone) to
+3000 (dense bone

CT/HU Numbers Based on Attenuation Coefficients
RAD 324 Newell

RAD 324 Newell

A
Window Level – Window Width
B
(A) L=50; W= 200 (B) L=50; W=400
A demonstrates ↑ contrast B demonstrates ↓ contrast: ↑ gray scale
A suggests ↓ *SNR B suggests ↑ SNR
* Signal to Noise Ratio
RAD 324 Newell

Soft Tissue Window Bone Window
Extradural Hematoma
RAD 324 Newell

RAD 324 Newell
Normal Brain Symmetry
Normal Air-Filled Spaces

Hemorrhage
RAD 411 Newell
New New and Old

Normal CSF Spaces
Subdural Hematoma :
A.
Mid line effacement/shift
RAD 324 Newell

Isodense Subdural Hematoma
Considered subacute due to becoming symptomatic 3 days to 3 weeks post trauma. Effects of severe anemia and very low hematocrit? ( mass attenuation and CT contrast). So, when suspected CT contrast is performed. Mid line effacement?

Subarachnoid Hemorrhage
Subarachnoid
Hemorrhage
A. Blood in Basilar
Cistern
B. Blood in Sylvian fissure
C. Blood in posterior horns lat. ventricles
D. Blood in sulci
RAD 324 Newell

Epidural Hematoma
Epidural Hematoma Signs:
A. Lens like or bi convex shaped in this temporal bone fx.
C . Mass effect with mid-line
shift
RAD 324 Newell

Normal Gray and White Matter
White matter has a greater fat content than does gray matter. Thus, White matter has a lower density and appears darker on a CT image (lipids are more radiolucent).
So, white matter is dark and gray matter is gray.
RAD 324 Newell

Progressive Ischemic (diminished blood flow) Changes with subsequent brain infarction.
Day 2 Day 4
Note: hypodensity changes between day 2 and day 4.
Hypodense changes may be visible within three hours

A
C
Contrast Media Enhancement
B
A.
No contrast enhancement.
B. Arterial phase contrast enhancement.
C.
Venous phase contrast enhancement
Note tumor enhancement in B & C.
RAD 411 Newell

Hydrocephalus
Note: Enlarged Basilar cistern, sulci, lateral and third ventricle
RAD 324 Newell

17

18

19

20

21

22

RAD 411 Newell
*
Partial obstruction seen two ways, with distended small bowel loops on KUB and dilated loops of fluid filled small bowel on CT

24

25

26

27

28

29

30

31

32

fini