1. All " Members" IMA Pathankot
“ IMA PRAYER ”
May happiness comes to all May all be free from disease May everyone of us ensure that no one suffer from pain or sorrow Neither do I desire the crown nor heaven nor rebirth I only desire to alleviate the sufferings of the creatures burning in the fire of pain or sorrow
Friday, 07-August-15
All " Members" IMA Pathankot

2. BASICS OF CT HEAD By Dr. Vinay Sharma MD Consultant Radiologist
Sharma Diagnostic Centre
Pathankot

3. Wilhelm Conrad Röntgen discovers x-rays in 1895
William David Coolidge invents the hot cathode x-ray tube in 1913
 Hounsfield scale used measure of radiodensity
 used in evaluating CT scans. 
Nobel Prize 
(1979)
Hounsfield units (symbol HU)
Air at −1000 HU
water at 0 HU
Cortical Bone at HU
( 1919 – 2004)
Sir Godfrey Newbold Hounsfield

4. 1972 2004 Used for head examinations – 64 slice scanner
Water bath required
80 x 80 matrix
4 minutes per revolution
1 image per revolution
8 levels of grey
Overnight image reconstruction
2004
– 64 slice scanner
1024 x 1024 matrix
0.33s per revolution
64 images per revolution
0.4mm slice thickness
20 images reconstructed/second

5. CT Scan Basics

9. CT - SCAN
Has assumed a critical role in the daily practice of Emergency Medicine for evaluating intracranial emergencies. (e.g. Trauma, Stroke, SAH, ICH).
Most practitioners have limited experience with interpretation.
In many situations, the Emergency Physician must initially interpret and act
on the CT without specialist assistance.

12. CT Scan Basics:-
A CT image is a computer-generated picture based on multiple x-ray exposures taken around the periphery of the subject.
X-rays are passed through the subject, and a scanning device measures the transmitted radiation.
The denser the object, the more the beam is attenuated, and hence fewer x-rays make it to the sensor.

13. Hounsfield units
Densities on CT Scan

14. Focuses the spectrum of gray-scale used on a particular image.
CT Scan Basics:
Windowing
Focuses the spectrum of gray-scale used on a particular image.

15. What Is Bright on CT? Air CSF/H20 What Is Dark on CT? Blood Contrast
Bone
Calcium
Metal
What Is Bright on CT?
Air
CSF/H20
What Is Dark on CT?

16. Advantages to CT Disadvantages to CT
Costs less than MRI
Better access
Shows up acute bleed
A good quick screen
Good visualization of bony structures and calcified lesions
Resolution
Beam-hardening artifact
Limited views of the posterior fossa and poor visualization of white-matter disease

17. CT Artifacts

18. CT Protocolling CT head protocols Variables With or Without contrast
CT Brain
CT Brain with posterior fossa images
CT Angiogram/Venogram
CT Perfusion
CT of Sinuses
CT of Orbit
CT of Temporal bones
CT of Mastoid bones
CT of Skull
CT of Face
Variables
Plain or contrast enhanced
Slice positioning
Slice thickness
Slice orientation
Slice spacing and overlap
Timing of imaging and contrast administration
Reconstruction algorhithm
Radiation dosimetry
Patient Information
Is the patient pregnant?
Radiation safety
Can the patient cooperate for the exam?

19. Normal CT

20. Normal CT Older person

21. Normal Enhanced CT

22. HOW TO READ CT-SCAN 1)…Normal Radiological Anatomy
2)… How to look at the images?
(a) Where to look?
Systematic approach
(b) what look for:
(i) abnormal opacity
(ii) abnormal radiolucency
(iii) distortion or displacement of a normal structure
3)…How to interpret the abnormality?
(a) Recognizing the abnormality,
(b) Describing it in generic terms,
(c) Giving a specific diagnosis

23. How to build up a normal mental image ?
Normal Radiological Anatomy
Normal radiological image of certain age and sex is a “Mental Image” that must be developed
How to build up a normal mental image ?
By developing a “Systematic Approach” to examine the radiological image
Advantages
Minimizes the chance of missing an abnormality
Makes complex images easier to read with practice
Builds up a mental databank of what is normal

24. Normal VS, Abnormal
It is not possible to call an image abnormal if the normal appearance is not known!!

25. CT SCAN WITHOUT CONTRAST

26. The documentary evidence of name and age
Technical factors

28. On non-contrast head CT:
In order to recognize the abnormal, you first need to know the appearance of the normal.
On non-contrast head CT:
Bone is white
Calcium is white;
Acute hemorrhage is usually white
Brain parenchyma is light grey;
White matter is darker than grey matter
CSF is very dark grey;
Sulci, cisterns and ventricles
Air is black;
Nasal cavity, sinuses, mastoid air cells
White
Light Grey
Charcoal
Grey
Black

29. Bone is white CSF is very dark grey Air is black;
Brain parenchyma is light grey;
White matter is darker than grey matter

30. (Normal anatomical structures)
Areas of interest
(Normal anatomical structures)
I. Check Brain Parenchyma
Check grey/white differentiation
Gyri
Look for blood
Surgeons need to know (size of hematoma, extent of midline shift, herniation)
II. Check CSF spaces: Ventricles, Cisterns and Sulci
CSF spaces (ventricles and cisterns)
size, symmetry, midline shift
herniation
Subfalcine – cingulate gyrus crosses falx
Transtentorial – temporal lobe into tentorial notch
Cerebellar – cerebellum into foramen magnum

31. (Normal anatomical structures)
Areas of interest
(Normal anatomical structures)
III. Check face and skull bones on bone windows
Do not confuse sutures with fracture especially in pediatric patients
IV. Check “air spaces”
Sinuses
Nasal airway
Ear Canals and Mastoid air cells

40. Learn and Know Different Parts of Brain

41. Correlate Different Parts of Brain at Particular Slice of CT Scan

42. Correlate Different Parts of Brain at Particular Slice of CT Scan

43. Correlate Different Parts of Brain at Particular Slice of CT Scan

44. What to look for? (In CT Head)
Brain tissue (window)
Bone detail (window)

45. Brain tissue (window) Brain tissue Without Contrast
Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT
Brain tissue Without Contrast
Brain tissue With Contrast

46. Brain tissue Without Contrast Brain tissue With Contrast
Nonenhanced CT scan shows a hyperdense mass resulted in midline shift to the right aspect in the left frontal lobe
Contrast enhanced CT shows a homogeneous enhancing mass located in the left frontal lobe.

47. What to look for : (i) abnormal opacity (ii) abnormal radiolucency (iii) distortion or displacement of a normal structure
Normal
Distortion or displacement of a normal structure
abnormal radiolucency
Frontal lobe
Midbrain
Cerebellum
RIGHT
LEFT
abnormal opacity

48. What to look for…….. Film findings:
Rt. frontoparietal subdural hematoma (6 mm)
Midline marker
Rt. temperoparietal epidural hematoma (1.8 cm)
6 mm leftward shift of lateral ventricles
Right lateral ventricle
Left lateral ventricle
Effacement of R sulci
BIDMC

49. Epidural Subdural Hematoma Parenchymal Hemorrhage
Subarachnoid Hemorrhage

50. A subarachnoid hemorrhage occurs with injury of small arteries or veins on the surface of the brain. The ruptured vessel bleeds into the space between the pia and arachnoid matter. The most common cause of subarachnoid hemorrhage is trauma. In the absence of significant trauma, the most common cause of subarachnoid hemorrhage is the rupture of a cerebral aneurysm. When traumatic, subarachnoid hemorrhage occurs most commonly over the cerebral convexities or adjacent to otherwise injured brain (i.e. adjacent to a cerebral contusion). If there is a large amount of subarachnoid hemorrhage, particularly in the basilar cisterns, the physician should consider whether a ruptured aneurysm led to the subsequent trauma. Cerebral angiography may be needed for further evaluation. On CT, subarachnoid hemorrhage appears as focal high density in sulci and fissures or linear hyperdensity in the cerebral sulci. Again, the most common location of posttraumatic subarachnoid hemorrhage is over the cerebral convexity. This may be the only indication of cerebral injury.
High density blood (arrowheads) fills the sulci over the  right cerebral convexity in this subarachnoid hemorrhage.

51. High density, crescent shaped hematoma (arrowheads)overlying the right cerebral hemisphere. Note the shift of the normally midline septum pellucidum due to the mass effect arrow.
The hypodense region (arrow) within the high density hematoma (arrowheads) may indicate active bleeding.
Deceleration and acceleration or rotational forces that tear bridging veins can cause an acute subdural hematoma. The blood collects in the space between the arachnoid matter and the dura matter. The hematoma on CT has the following characteristics: - Crescent shaped - Hyperdense, may contain hypodense foci due to serum, CSF or active bleeding - Does not cross dural reflections

52. Sub - acute subdural hematoma (arrowheads).
Subacute SDH may be difficult to visualize by CT because as the hemorrhage is reabsorbed it becomes isodense to normal gray matter. A subacute SDH should be suspected when you identify shift of midline structures without an obvious mass. Giving contrast may help in difficult cases because the interface between the hematoma and the adjacent brain usually becomes more obvious due to enhancement of the dura and adjacent vascular structures. Some of the notable characteristics of subacute SDH are: - Compressed lateral ventricle - Effaced sulci - White matter "buckling" - Thick cortical "mantle"
Note ….The compression of gray and white matter in the left hemisphere due to the mass effect.

53. Crescent shaped chronic subdural hematoma (arrowheads)
Crescent shaped chronic subdural hematoma (arrowheads). Notice the low attenuation due to reabsorbtion of the hemorrhage over time
This chronic subdural hematoma (arrowheads) shows the septations and loculations that often occur over time.

54. Biconvex (lenticellular) epidural hematoma (arrowheads), deep to the parietal skull fracture (arrow).
An epidural hematoma is usually associated with a skull fracture. It often occurs when an impact fractures the calvarium. The fractured bone lacerates a dural artery or a venous sinus. The blood from the ruptured vessel collects between the skull and dura. On CT, the hematoma forms a hyperdense biconvex mass. It is usually uniformly high density but may contain hypodense foci due to active bleeding. Since an epidural hematoma is extradural it can cross the dural reflections unlike a subdural hematoma. However an epidural hematoma usually does not cross suture lines where the dura tightly adheres to the adjacent skull.

55. Hemorrhage in the corpus callosum (arrow).
Hemorrhage of the posterior limb of the internal capsule (arrow) and hemorrhage of the thalamus (arrowhead).
Hemorrhage in the corpus callosum (arrow).
Diffuse axonal injury is often referred to as "shear injury". It is the most common cause of significant morbidity in CNS trauma. Fifty percent of all primary intra-axial injuries are diffuse axonal injuries. Acceleration, deceleration and rotational forces cause portions of the brain with different densities to move relative to each other resulting in the deformation and tearing of axons. Immediate loss of consciousness is typical of these injuries. The CT of a patient with diffuse axonal injury may be normal despite the patient's presentation with a profound neurological deficit. With CT, diffuse axonal injury may appear as ill-defined areas of high density or hemorrhage in characteristic locations. The injury occurs in a sequential pattern of locations based on the severity of the trauma. The following list of diffuse axonal injury locations is ordered with the most likely location listed first followed by successively less likely locations: - Subcortical white matter  - Posterior limb internal capsule - Corpus callosum - Dorsolateral midbrain

56. Multiple foci of high density corresponding to hemorrhage (arrows) in an area of low density (arrowheads) in the left frontal lobe due to cerebral contusion.
Intraventricular hemorrhage (arrow) found in a trauma patient. Note the subarachnoid hemorrhage in the sulci in the subarachnoid space (arrowheads).
Cerebral contusions are the most common primary intra-axial injury. They often occur when the brain impacts an osseous ridge or a dural fold. The foci of punctate hemorrhage or edema are located along gyral crests. The following are common locations: - Temporal lobe - anterior tip, inferior surface, sylvian region - Frontal lobe - anterior pole, inferior surface - Dorsolateral midbrain - Inferior cerebellum On CT, cerebral contusion appears as an ill-defined hypodense area mixed with foci of hemorrhage. Adjacent subarachnoid hemorrhage is common. After hours, hemorrhagic transformation or coalescence of petechial hemorrhages into a rounded hematoma is common.

57. Abscess

58. Intracranial Air 58

59. Mass Effect 59

60. Hydrocephalus

61. cerebral atrophy is parenchymal volume loss

62. BONE WINDOW Normal Linear fracture Linear fracture Depressed fracture
SELLA TURCICA
CORONAL SUTURE
GROOVE FOR MCA
EXT.AUD MEATUS
ORBITAL GROOVE
Depressed fracture
Normal
BONE WINDOW
Linear fracture
Linear fracture

63. CONCLUSION
If no blood is seen, all cisterns are present and open, the brain is symmetric with normal gray-white differentiation, the ventricles are symmetric without dilation, and there is no fracture, then there is no emergent diagnosis from the CT scan.

64. THANKS
FOR
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