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Andrew D. Perron, MD, FACEP 1 How to Read a Head CT (or “How I learned to stop worrying and love computed tomography”)

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Presentation on theme: "Andrew D. Perron, MD, FACEP 1 How to Read a Head CT (or “How I learned to stop worrying and love computed tomography”)"— Presentation transcript:

1 Andrew D. Perron, MD, FACEP 1 How to Read a Head CT (or “How I learned to stop worrying and love computed tomography”)

2 Andrew D. Perron, MD, FACEP EM Residency Program Director Department of Emergency Medicine Maine Medical Center Portland, ME Andrew D. Perron, MD, FACEP 2

3 3 Head CT 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.

4 Andrew D. Perron, MD, FACEP 4 Head CT Most EM training programs have no formalized training process to meet this need. Many Emergency Physicians are uncomfortable interpreting CTs. Studies have shown that EPs have a significant “miss rate” on cranial CT interpretation.

5 Andrew D. Perron, MD, FACEP 5 Head CT In medical school, we are taught a systematic technique to interpret ECGs (rate, rhythm, axis, etc.) so that all aspects are reviewed, and no findings are missed.

6 Andrew D. Perron, MD, FACEP 6 Head CT The intent of this session is to introduce a similar systematic method of cranial CT interpretation, based on the mnemonic…

7 Andrew D. Perron, MD, FACEP 7 Head CT “Blood Can Be Very Bad”

8 Andrew D. Perron, MD, FACEP 8 Blood Can Be Very Bad Blood Cisterns Brain Ventricles Bone

9 Andrew D. Perron, MD, FACEP 9 Blood Can Be Very Bad Blood Cisterns Brain Ventricles Bone

10 Andrew D. Perron, MD, FACEP 10 Blood Can Be Very Bad Blood Cisterns Brain Ventricles Bone

11 Andrew D. Perron, MD, FACEP 11 Blood Can Be Very Bad Blood Cisterns Brain Ventricles Bone

12 Andrew D. Perron, MD, FACEP 12 Blood Can Be Very Bad Blood Cisterns Brain Ventricles Bone

13 Andrew D. Perron, MD, FACEP 13 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.

14 Andrew D. Perron, MD, FACEP 14 CT Scan Basics The denser the object, the whiter it is on CT –Bone is most dense = + 1000 Hounsfield U. –Air is the least dense = - 1000H Hounsfield U.

15 Andrew D. Perron, MD, FACEP 15 CT Scan Basics: Windowing Focuses the spectrum of gray-scale used on a particular image.

16 2 Sheet Head CT

17 Andrew D. Perron, MD, FACEP 17 Brainstem Cerebellum Skull Base –Clinoids –Petrosal bone –Sphenoid bone –Sella turcica –Sinuses Posterior Fossa

18 Andrew D. Perron, MD, FACEP 18 CT Scan

19

20 Sagittal View C Circummesencephalic Cistern

21 Andrew D. Perron, MD, FACEP 21 CT Diagnostics Where is the most sensitive area to examine the CT for increased ICP? A.Lateral Ventricles B.IVth ventricle C.Basilar Cisterns D.Gyral pattern

22 Andrew D. Perron, MD, FACEP 22 Cisterns

23 Andrew D. Perron, MD, FACEP 23 CT Scan

24 Andrew D. Perron, MD, FACEP 24 Brainstem Lateral View

25 Andrew D. Perron, MD, FACEP 25 2 nd Key Level 2 nd Key Level Sagittal View Circummesencephalic Cistern

26 Andrew D. Perron, MD, FACEP 26 Cisterns at Cerebral Peduncles Level

27 Andrew D. Perron, MD, FACEP 27 CT Scan

28 Andrew D. Perron, MD, FACEP 28 Suprasellar Cistern

29 Andrew D. Perron, MD, FACEP 29 CT Diagnostics Where is the most sensitive area to examine the CT for ventricular dilation? A.IIIrd ventricle B.IVth ventricle C.Temporal horns of lateral ventricles

30 Andrew D. Perron, MD, FACEP 30 CT Scan

31 Andrew D. Perron, MD, FACEP 31 3 rd Key Level Sagittal View Circummesencephalic Cistern

32 Andrew D. Perron, MD, FACEP 32 Cisterns at High Mid-Brain Level

33 CT Scan

34 Andrew D. Perron, MD, FACEP 34 Ventricles

35 Andrew D. Perron, MD, FACEP 35 CSF Production Produced in choroid plexus in the lateral ventricles  Foramen of Monroe  IIIrd Ventricle  Acqueduct of Sylvius  IVth Ventricle  Lushka/Magendie 0.5-1 cc/min Adult CSF volume is approx. 150 cc’s. Adult CSF production is approx. 500- 700 cc’s per day.

36 Andrew D. Perron, MD, FACEP 36 CT Scan

37 CT Scans Andrew D. Perron, MD, FACEP 37

38 Andrew D. Perron, MD, FACEP 38 A Few Kid-Specific Thoughts

39 Andrew D. Perron, MD, FACEP 39 A Few Kid-Specific Thoughts Premature Infants (30-34 weeks): Larger sylvian, basilar (circummesencephalic) cisterns. Larger subarachnoid spaces Thin cerebral cortex (Gray matter) Prominent white matter (with higher water content) Limited cortical gyral pattern Ventricles are variable: slit-like to well-developed Term Infant (36-41 weeks): Small, slit-like lateral ventricles Continued white-matter prominence More prominent sulcal pattern Temporal horns unlikely to be seen 1st & 2nd years of Life: Marked growth of all lobes of the brain (proportionally greatest in frontal lobes) Wide variation in lateral ventricle size (3rd and 4th fairly constant) Temporal horns unlikely to be seen.

40 Andrew D. Perron, MD, FACEP 40 1 day 1 year 2 years

41 Trauma Pictures

42 Andrew D. Perron, MD, FACEP 42 B is for Blood 1 st decision: Is blood present? 2 nd decision: If so, where is it? 3 rd decision: If so, what effect is it having?

43 Andrew D. Perron, MD, FACEP 43 CT Diagnostics At what point does blood become isodense with brain? A.About 48 hours B.About 1 week C.About 2 weeks D.After 1 month

44 Andrew D. Perron, MD, FACEP 44 B is for Blood Blood becomes hypodense at approximately 2 weeks. Blood becomes isodense at approximately 1 week. Acute blood is bright white on CT (once it clots).

45 Andrew D. Perron, MD, FACEP 45 B is for Blood Blood becomes hypodense at approximately 2 weeks. Blood becomes isodense at approximately 1 week. Acute blood is bright white on CT (once it clots).

46 Andrew D. Perron, MD, FACEP 46 B is for Blood Blood becomes hypodense at approximately 2 weeks. Blood becomes isodense at approximately 1 week. Acute blood is bright white on CT (once it clots).

47 Andrew D. Perron, MD, FACEP 47 Epidural Hematoma Lens shaped Does not cross sutures Classically described with injury to middle meningeal artery Low mortality if treated prior to unconsciousness ( < 20%)

48 Andrew D. Perron, MD, FACEP 48 CT Scans

49 Andrew D. Perron, MD, FACEP 49 Subdural Hematoma Typically falx or sickle- shaped. Crosses sutures, but does not cross midline. Acute subdural is a marker for severe head injury. (Mortality approaches 80%) Chronic subdural usually slow venous bleed and well tolerated.

50 CT Scan Andrew D. Perron, MD, FACEP 50

51 Andrew D. Perron, MD, FACEP 51 Subarachnoid Hemorrhage

52 Andrew D. Perron, MD, FACEP 52 Subarachnoid Hemorrhage Blood in the cisterns/cortical gyral surface –Aneurysms responsible for 75-80% of SAH –AVM’s responsible for 4-5% –Vasculitis accounts for small proportion (<1%) –No cause is found in 10-15% –20% will have associated acute hydrocephalus

53 Andrew D. Perron, MD, FACEP 53 CT Diagnostics What is the sensitivity of CT for SAH? A.100% B.95% C.80% D.Depends…I need a lot more information to answer.

54 Andrew D. Perron, MD, FACEP 54 98-99% at 0-12 hours 90-95% at 24 hours 80% at 3 days 50% at 1 week 30% at 2 weeks  Depends on generation of scanner and who is reading scan and how much blood there is. CT Scan Sensitivity for SAH

55 Andrew D. Perron, MD, FACEP CT Scan 55

56 CT Scan Andrew D. Perron, MD, FACEP 56

57 Andrew D. Perron, MD, FACEP 57 Intraventricular/ Intraparenchymal Hemorrhage

58 CT Scan Andrew D. Perron, MD, FACEP 58

59 Andrew D. Perron, MD, FACEP 59 C is for CISTERNS 4 key cisterns –Circummesencephalic –Suprasellar –Quadrigeminal –Sylvian (Blood Can Be Very Bad) Circummesencephalic

60 Andrew D. Perron, MD, FACEP 60 Cisterns 2 Key questions to answer regarding cisterns: –Is there blood? –Are the cisterns open?

61 Andrew D. Perron, MD, FACEP 61

62 Andrew D. Perron, MD, FACEP 62

63 Andrew D. Perron, MD, FACEP 63

64 Andrew D. Perron, MD, FACEP 64 B is for BRAIN (Blood Can Be Very Bad)

65 Andrew D. Perron, MD, FACEP 65

66 Tumor Andrew D. Perron, MD, FACEP 66

67 Atrophy Andrew D. Perron, MD, FACEP 67

68 Andrew D. Perron, MD, FACEP 68 CT Diagnostics What percentage of mass lesions will require IV contrast to be identified? A.100% B.50% C.30-40% D.10-20%

69 Abscess Andrew D. Perron, MD, FACEP 69

70 Hemorrhagic Contusion Andrew D. Perron, MD, FACEP 70

71 Andrew D. Perron, MD, FACEP 71

72 Mass Effect Andrew D. Perron, MD, FACEP 72

73 Stroke Andrew D. Perron, MD, FACEP 73

74 Andrew D. Perron, MD, FACEP 74 Intracranial Air

75 Andrew D. Perron, MD, FACEP 75

76 Intracranial Air Andrew D. Perron, MD, FACEP 76

77 Andrew D. Perron, MD, FACEP 77 V is for VENTRICLES (Blood Can Be Very Bad)

78 Andrew D. Perron, MD, FACEP 78

79 Andrew D. Perron, MD, FACEP 79

80 Ex-Vacuo Phenomenon Andrew D. Perron, MD, FACEP 80

81 Andrew D. Perron, MD, FACEP 81

82 Andrew D. Perron, MD, FACEP 82

83 Andrew D. Perron, MD, FACEP 83

84 BONE Andrew D. Perron, MD, FACEP 84

85 Andrew D. Perron, MD, FACEP 85

86 Andrew D. Perron, MD, FACEP 86

87 Andrew D. Perron, MD, FACEP 87

88 Andrew D. Perron, MD, FACEP 88

89 Andrew D. Perron, MD, FACEP 89 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. Blood Can Be Very Bad

90 RIP

91 Andrew D. Perron, MD, FACEP 91Questions ferne_acep_2005_peds_perron_ich_bcbvb_fshow.ppt4/30/2015 10:02 PM www.ferne.org ferne@ferne.org Andrew D. Perron, MD, FACEP 207) 662-7015 perroa@mmc.org (207) 662-7015


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