CT Head 2 BY JR 1 PGIMER CHANDIGARH.pptx

CT HEAD. DESCRIPTION ABOUT COMPUTED TOMOGRAPHY

1. CT HEAD Presenter-Dr . Anshika Saxena Moderator- Dr. Janani Anandkumar CT HEAD

2. CONTENTS Introduction History Basic principles of CT and image reconstruction Importance of CT in acute trauma Role of CT in Emergency Triage Basic anatomy of brain Windowing CT in neurocranial pathologies Advances and future trends Conclusion

3. INTRODUCTION A Computed Tomography (CT) scan( tomos — meaning section, graphy —picture in Greek) It is an X-ray based imaging procedure that uses a computer to create detailed cross-sectional pictures of the body's bones, muscles, fat, organs, and blood vessels

4. HISTORY AND BASICS GN Hounsfield , a senior research scientist in England announced the invention of a revolutionary imaging technique. In the year 1972, that he called computed axial transverse scanning 1917— Radon developed the basic mathematical equations. • 1940— Frank and Takahashi published the basic principles of axial CT.

5. • 1956— Cormack developed theory of image reconstruction . • 1967— Hounsfield developed the clinically useful CT scanner . • 1973—First clinical brain scanner in Mayo Clinic Hounsfield and Cormack shared the 1979 Nobel Prize for their development of CT

6. Basic principle of CT

7. In early versions of CT scanners, both the x-ray tube and detectors rotated synchronously about the patient. In more recent design the detectors form a continuous ring about the patient and the x-ray tube moves in a circle within the fixed detector ring .

8. IMAGE RECONSTRUCTION The computer receives a signal in analog form and converts it to a binary digit . The digital signal is stored and the image is reconstructed after the scan is over. Each picture is displayed on a matrix, each square in a matrix is called a pixel , its assigned a number based on the amount of energy reaching the detector. This number is called as Hounsfield unit The reconstructed anatomy of an object is in the digital format composed of a volume of tissue called voxel

9. CT Numbers and Hounsfield Units The digital value ascribed to each pixel is called the Hounsfield units or HU, which lies on a scale were water has a value of 0 and air has a value of –1000. Bone has a value in order of +1000.

10. IMPORTANCE OF CT IN ACUTE TRAUMA CT is fast and readily available in emergency settings, making it primary imaging modality for quick assessment. Highly sensitive to detecting intracranial haemorrhage(bleeding). It excels at visualizing skull fractures and bone injuries that may be missed by other imaging techniques. CT can identify other brain injuries, including contusions (bruised brain tissue), hematomas (blood clots ), and swelling.

11. ROLE OF CT IN EMERGENCY TRIAGE NON TRAUMA CASES BRAIN ATROPHY HYDROCEPHALUS CEREBRAL INFARCT TRAUMA CASES SUBARACHNOID HEMORRHAGE SUBDURAL HEMORRHAGE EXTRADURAL HEMORRHAGE INTRAVENTRICULAR HEMORRHAGE SKULL BONE FRACTURES PNEUMOCEPHALUS

12. CONTRAINDICATIONS OF CT C/I in pregnancy- Radiation exposure during a CT scan can pose a risk to the fetus . Severe allergy to contrast material- If iodine-based contrast media is used, it can cause an anaphylactic reaction.

13. LIMITATIONS OF CT Sensitivity to small lesions -CT scans are not as sensitive as MRI for detecting small, non- haemorrhagic lesions like cortical contusions or diffuse axonal injuries Limited Soft Tissue Detail: CT scans provide less precise details of soft tissues compared to MRI.

14. RADIATION CONSIDERATIONS Typical Radiation Dose CT head dose (adult): ~ 1.5–2.5 mSv (millisieverts). Equivalent to about 8–12 months of background radiation . Children: More radiosensitive → dose should be minimized (ALARA principle: As Low As Reasonably Achievable ). Dose Comparison So 1 CT head ≈ 300 IOPA X-rays (range 200–500 depending on technique). So 1 CT head ≈ 75 OPGs (range 50–100).

15. NON CONTRAST CT(NCCT) Non-Contrast CT Head What it is: A scan performed without the use of any contrast dye.  What it shows: Differentiates tissues based on their natural density, making it excellent for detecting bone, acute bleeding (like hemorrhage), and fractures .   Common uses: Emergency evaluation for trauma and head injuries. Rapid detection of acute intracranial hemorrhage or stroke. 

16. CONTRAST ENHANCED CT(CECT) Contrast CT Head What it is: A scan where a special contrast dye is injected into the bloodstream What it shows: The dye highlights blood vessels and certain tissues, improving the clarity and detail of soft tissues.  Common uses: Detecting tumors. Diagnosing infections and inflammation. Visualizing vascular malformations or vascular diseases. Providing detailed information for surgical planning

17.  Section at the level of basal cisterns shows hyperdensity of arteries at the Circle of Willis

18. WHEN TO USE CT/MRI? CT Scan for Head Trauma When it's used : For patients in the emergency setting after a head injury.   What it finds: Intracranial hemorrhage (bleeding inside or around the brain). Skull fractures. Brain swelling (edema). Mass effect (swelling or bleeding that puts pressure on the brain). MRI Scan for Head Trauma When it's used: When clinical symptoms are more severe than what the initial CT scan shows. To detect diffuse axonal injury (DAI ), which is often not visible on a CT scan. To look for subtle, non-hemorrhagic brain injuries or lesions with predominantly edema . After the initial acute phase (often 24-48 hours after injury) for better detection of certain lesions.  What it finds:Non-hemorrhagic contusions (bruises) and lesions with predominant edema

19. Simplified Rule in Trauma Emergency / Unstable → NCCT Head (rule out bleed, fracture, mass effect). DAI/ tumor / vascular malformation- CECT Head Stable patient / suspected subtle injury → MRI Brain (DAI, posterior fossa, brainstem, chronic changes). Often both are complementary : CT = quick diagnosis, surgical planning. MRI = detailed prognostication, long-term evaluation.

20. CT IMAGE OF BRAIN

21. WINDOWING Window Width (W): This parameter controls the range of X-ray attenuation (density) values that are assigned a grayscale value on the image. A narrower window displays a smaller range of densities, increasing the contrast and showing fine details Window Level (L): This is the midpoint of the window width and determines the average density of the tissue that will be displayed as mid-gray

22. BRAIN WINDOW- The standard setting for brain imaging, this window is used to differentiate between gray and white matter and view soft tissues. A typical setting is W: 80, L: 40 Hounsfield Units (HU ). BONY WINDOW- This window emphasizes bone structures. It uses a much wider range (e.g., W: 2800-4000 HU),L:400 to show bone density. SUBDURAL WINDOW- Used to highlight acute subdural hematomas (blood)W= 130-300 HU,L=30   A specific setting (e.g., W: 8 L: 32 or W: 40 L: 40 ) that helps detect early ischemic changes and subtle abnormalities, especially within the brain. 

23. BONE WINDOW

24. STROKE WINDOW We generate lot of contrast between gray and white matter. In yellow area, we see brain parenchyma looks hypodense and we cannot see the clear contrast. This is an early ischemic stroke. If we compare with normal side, we can appreciate clear contrast.

25. SUBDURAL WINDOW

26. ARTIFACTS

27. MOTION ARTIFACT

28. BEAM HARDENING ARTEFACT

29. PARTIAL VOLUME ARTEFACT

30. Physiological hyperdensities

31. ANATOMY OF BRAIN ON CT

32. BONES OF CRANIUM AXIAL CT

33. CRANIAL BASE-CT FORAMINA,NASAL CAVITY,PARANASAL SINUS

34. PARANASAL SINUS CT

35. DURAL VENOUS SINUSES

36. VENTRICULAR SYSTEM OVERVIEW

37. The openings connecting the lateral and the third ventricles are called foramen Monro . It is crucial while evaluating hydrocephalus. The nodular thickening in the middle is called septum pellucidum.

38. 4 th ventricle is located infratentorially between brainstem and cerebellum. The passage connecting third and fourth ventricle is the cerebral aqueduct.

39. NEUROCRANIAL PATHOLOGIES

40. STROKE Rapidly developed clinical signs of focal (or global) disturbance of cerebral function, lasting more than 24 hours or leading to death, with no apparent cause other than that of vascular origin.

41. Acute haemorrhage is hyperdense on ct. Pathology containing lot of water like cerebral edema or ischemic stroke will be hypodense. Here in the second image, territory of middle cerebral artery is affected with ischemic stroke. Also, the parenchyma looks swollen and hypodense.

42. CEREBRAL EDEMA Cerebral edema in CT is seen as loss of differentiation of gray and white matter . Early total infarction is due to involvement of any one of the major arteries. Sometimes only a branch of artery would get affected and the area involved would be smaller and known as early partial media infarction.

43. EPIDURAL HEMATOMA Located between skull and periosteum Due to laceration of middle meningeal artery and veins mostly Can cross dural reflections but cannot cross suture lines Lentiform shape or lens shaped. Symptoms like a severe headache and loss of consciousness, often with a "lucid interval ," necessitate immediate medical intervention. where a person experiences a brief period of lucidity after initially losing consciousness, only to deteriorate rapidly afterward due to the growing epidural hematoma.

44. CASE REPORT 📌 Case Summary 57-year-old male , h/o hypertension & alcohol-related seizures. Trauma activation → altered sensorium (GCS 10). Findings: right parietal scalp hematoma + abrasion, no skull fracture. C/F: brief loss of consciousness → regained consciousness → deteriorated rapidly. During CT → seizures → controlled with IV lorazepam (4 mg). CT head : multiple ICHs → right extradural hematoma (EDH) + left subdural hematoma (SDH). Neurosurgery : emergency bilateral craniotomies, EVD, and cerebral microdialysis catheters.

45. SUBDURAL HEMATOMA Occurs between the dura and arachnoid Can cross the sutures but not dural reflections Due to disruption of the bridging cortical veins Hypodense( hyperacute,chronic ) isodense (subacute),hyperdense(acute). Headache, confusion, slurred speech, dizziness, change in vision. For large or acute hematomas, a  craniotomy , surgery to create an opening in the skull, may be necessary to remove the blood clot.

46. CASE REPORT 📌 Case Summary (31M with chronic SDH) 31-year-old male , no medical history. Symptoms : headache ×3 weeks, worsens lying down, relieved sitting; left eye diplopia. No trauma, no vomiting, seizures, weakness, or altered sensorium. Exam : GCS 15/15, pupils equal/reactive, CNs normal except diplopia; normal motor/sensory/reflexes. Consciousness: gradual deterioration ; fluctuating consciousness, confusion, drowsiness Right frontal SDH : very small, no mass effect, managed conservatively. The indications for surgical intervention are the following: The patient is experiencing symptoms, or/and Midline shift more than 5 mm, or/and thickness more than 1 cm on imaging. Patient was planned for surgical).

47. SUBARACHNOID HEMORRHAGE It is often marked by a sudden, severe headache, dubbed a " thunderclap headache ," accompanied by symptoms like nausea, vomiting, confusion, and a stiff neck . Can originate from a direct vessel injury, contused cortex or intraventricular hemorrhage .  The primary cause is the rupture of a brain aneurysm , but traumatic head injuries also contribute We must check the interpeduncular cistern and sylvian fissure . Drugs are used to relieve pain, control blood pressure, and prevent complications like cerebral vasospasm. Procedures like neurosurgical clipping are performed to seal off the ruptured aneurysm and stop the bleeding. 

48. SAH due to Trauma or Aneurysm? How to differentiate? Aneurysmal SAH is mostly seen in the basal cisterns. Traumatic SAH can be located anywhere.

49. CASE REPORT Case Summary Patient: 36-year-old male History: Headache (frontal, continuous), vomiting; hypertensive (4 months), not on medication; no head injury. CT Findings: Subarachnoid hemorrhage (SAH) in medial longitudinal fissure, basal/prepontine/ambient cisterns, bilateral sylvian fissures, and tentorium. Periventricular white matter hyperintensities suggest chronic small vessel ischemic changes. Management: Nimodipine prescribed → prevents vasospasm. Endovascular embolization / surgical clipping → definitive treatment for ruptured aneurysm

50. INTRAVENTRICULAR HEMORRHAGE Most commonly due to rupture of subependymal vessels Can occur due to reflex of SAH or contiguous extension of an intracerebral haemorrhage. This condition is most common in premature babies due to their fragile, underdeveloped brain blood vessels. It occurs when the delicate blood vessels in the brain’s germinal matrix rupture, causing bleeding to extend into ventricles. Look for blood-cerebrospinal fluid level in occipital horns and other ventricles. It occurs when the delicate blood vessels in the brain's germinal matrix rupture, causing bleeding to extend into the ventricles.  It occurs when the delicate blood vessels in the brain's germinal matrix rupture, causing bleeding to extend into the ventricles.  It occurs when the delicate blood vessels in the brain's germinal matrix rupture, causing bleeding to extend into the ventricles.  It occurs when the delicate blood vessels in the brain's germinal matrix rupture, causing bleeding to extend into the ventricles. 

51. SURFACE CONTUSION/ LACERATION Most common source of traumatic subarachnoid haemorrhage . Contusion- must involve superficial grey matter Laceration- contusion+ tear of pia arachnoid Affects crests of gyri

52. Hemorrhage present in half cases and occur at right angles to cortical surface. Located near irregular bony contours : poles of frontal lobes, temporal lobes , inferior cerebellar hemispheres. Appear as patchy areas in the ct scan

53. On a CT scan, a surface brain contusion is seen as a localized area of blood (hyperdense) mixed with brain tissue and often surrounded by swelling (hypodense). A  brain laceration , on the other hand, is a direct tear of the brain tissue itself, which can accompany contusions and may be associated with a skull fracture

54. INTRAPARENCHYMAL HAEMORRHAGE Focal collections of blood that most commonly arise from shear strain injury to intraparenchymal vessels. Usually located in the fronto temporal white matter or basal ganglia. Hematoma within normal brain Differential diagnosis: DAI, hemorrhagic contusion.

55. If we have a spontaneous intraparenchymal haemorrhage in the deeper region of brain in an elderly patient eg basal ganglia, it is likely a hypertensive hemorrhage . If we an intraparenchymal hemorrhage located superficially in the brain(lobar) in an elderly patient, it will be secondary to CAA ( Cerebral Amyloid Angiopathy). Due to weakening of leptomeningeal or cortical arteries because of deposition of amyloid in vessel walls.

56. LET’S SUMMARIZE THE HEMORRHAGES

57. DIFFUSE AXONAL INJURY Diffuse Axonal Injury (DAI) is a type of traumatic brain injury (TBI) caused by the brain's rapid rotation and movement inside the skull, leading to the tearing and stretching of nerve fibers (axons ) in the white matter. This widespread shearing of axons causes widespread brain damage, leading to symptoms like coma, and can result in severe, long-term disability or a persistent vegetative state Patient has severe LOC on impact. Due to acceleration/deceleration of white matter

58. Grade 1= Axonal damage in white matter(WM) only-67% Grade 2= WM+ Corpus callosum(post>ant)-21% Grade 3= WM+ CC+ Brainstem Hours: haemorrhage and axonal swelling Days/weeks: clusters of microglia,astrocyte Months/ years: Wallerian degeneration

59. BRAINSTEM INJURY By direct/indirect forces Most commonly associated with DAI Involves the dorsolateral midbrain and upper pons and is usually hemorrhagic Duret haemorrhage is an eg of indirect damage: tearing of pontine perforators leading to hemorrhage in the setting transtentorial herniation.

60. BRAIN HERNIATION Brain herniation is a life-threatening medical condition where brain tissue shifts from its normal position within the skull, often due to increased pressure from causes like swelling, tumors, bleeding, or infection.  This displacement can compress vital structures, leading to symptoms such as severe headache, loss of consciousness,  pupil dilation , and eventually coma or death .

61. How to measure the midline shift

62. RECENT ADVANCES MDCT Provides high resolution thin sections , allowing multiplanar reconstructions. Critical for emergency triage , surgical planning, and prognosis. Indications- severe head trauma, deteriorating neurological status, skull fracture. Advantages- Speed : whole brain scanned in seconds. Thin slices : allows multiplanar views (axial, coronal, sagittal).

63. INTRAOPERATIVE CT Intraoperative CT ( iCT ) refers to CT imaging performed during surgery . Provides immediate feedback for precision, safety, and outcome improvement. Indications- Tumor resection Confirms extent of tumor removal, avoids residual tumor. Ventricular shunt placement Verifies accurate catheter positioning. Trauma surgery Confirms fracture reduction or hematoma evacuation.

64. Dual-Energy CT CT technique using two different X-ray energy spectra (typically high and low kVp ) to acquire images simultaneously or sequentially Clinical Applications Cardiac CT Quantifies myocardial perfusion; reduces contrast dose. Pulmonary Imaging Detects pulmonary embolism with perfusion maps. Oncology Improves tumor visualization and treatment response assessment.

65. CONCLUSION CT is the gold standard in acute head trauma imaging due to speed, availability, and sensitivity for blood and bone. Provides rapid triage between surgical and non-surgical lesions. Essential in detecting hemorrhages , fractures, edema , herniation, and vascular injuries MRI complementary in selected cases. Systematic approach improves accuracy: review bones → brain parenchyma → ventricles → cisterns → vessels. Early detection and intervention significantly improve patient outcomes."A timely CT can save a life—interpretation with precision is the key."

66. REFERENCES Grainger & Allison’s Diagnostic Radiology Essentials Contemporary Oral and Maxillofacial Surgery – James R. Hupp – has a practical section on radiology and head CT. Atlas of Emergency CT Head – Luca Saba – useful for trauma and acute neuro cases. Goubert R, Wray A, Matonis D. A Case Report of Epidural Hematoma After Traumatic Brain Injury. J Educ Teach Emerg Med. 2020 Jul 15;5(3):V22-V24. doi : 10.21980/J8R059. PMID: 37465217; PMCID: PMC10332544. Mohamed T, Swed S, Al- Mouakeh A, Sawaf B. Nontraumatic bilateral subdural hematoma: Case report. Ann Med Surg ( Lond ). 2021 Oct 8;71:102907. doi : 10.1016/j.amsu.2021.102907. PMID: 34712475; PMCID: PMC8528674.