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Ct brain presentation
The document provides information about CT brain imaging including terminology used, differences between CT and MRI, how a CT scan works, tissue densities visualized on CT, common anatomical structures seen on brain CT, approaches to interpreting a CT brain scan, and various pathological conditions that can be identified on CT including trauma, vascular insults, infections, tumors and other disorders. Key points covered include how CT provides clear bone images while MRI better depicts soft tissue contrast, how CT reconstruction works to create cross-sectional images, and examples of some common abnormalities that manifest as hyperdense or hypodense lesions on CT scans.
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Ct brain presentation
- 1. CT BRAIN forMedical and Neurology residents Qamar zaman FCPS,SCE(NEUROLOGY)
- 2. Terminology used inCT. • Section of the study (most commonly axial is used). • Right and left side of the image. • Density of a structure is taken relative to the density of water and described as isodense, hyperdense and hypodense. • Location and anatomical structures involved. • Should be able to formulate radiological differentials.
- 3. Which one isCT brain
- 4. How to differentiateCT from MRI • Bone is dense(white) on CT brain while hypo intense(dark) on MRI(outer bright signals on MRI are due to subcutaneous fats). • Grey-white matter differentiation is clear on MRI compared to the CT. • Presence of periventricular lucent areas in MRI. • MRI usually have multiple films compared to commonly single in CT
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- 6. Mechanism • X-ray emitterand detector rotate in circular fashion. • When radiation pass through exposed structure they behave differently depending on the density and physical properties. • A visual representation of the raw data obtained is called a sinogram which is raw form. • The data must be processed using a form of tomographic reconstruction which produces a series of cross-sectional images.
- 7. Image acquisition • Unitused to measure the density are called as Hounsfield. • It can range on a scale from +3071 (most attenuating) to −1024 (least attenuating) on the Hounsfield scale.
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- 9. • Contrast usedfor X-ray CT, as well as for plain film X-ray, are called radiocontrasts. Radiocontrasts for X-ray CT are, in general, iodine-based. Often, images are taken both with and without radiocontrast
- 10. Precautions • If youare pregnant or suspect that you may be pregnant, you should notify your doctor. Radiation exposure during pregnancy may lead to birth defects • Nursing mothers may want to wait 24 hours after contrast material is injected before resuming breastfeeding. • there is a risk for allergic reaction to the dye
- 11. • Patients withkidney failure or other kidney problems should notify their doctor. • patients taking the diabetes medication metformin (Glucophage) should alert their doctors before having IV contrast as it may cause a rare condition called metabolic acidosis.
- 12. When to preferCT over MRI • Trauma or acute emergency settings where time is important. • When ruling out bony injuries and bleeds that are easily picked. • Contraindications to MRI eg metallic objects. • Claustrophobic patients. • Cost and availibilty factors.
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- 17. Modalities of CTused in brain • Plain non contrast CT (with parenchymal and bone windows). • CT with contrast. • CT perfusion. • CT Angiogram. • CT Venogram. • CT with special cuts like orbit, Pituatrity fossa.
- 19. Anatomical Land marks. •Cortex and division into various lobes. • Subcortical structures including basal ganglia,thalamus . • Pituatry area and cavernous sinus region. • Brainstem. • CSF system. • Arterial and venous system.
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- 24. Fig 2a: T1MRI axial projection. 1: inter- hemispheric scissure; 2: lateral sulcus; 3: frontal lobe; 4: insula lobe; 5: temporal lobe; 6: occipital lobe.
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- 51. orientation • Two-dimensional CTimages are conventionally rendered so that the view is as though looking up at it from the patient's feet. • Hence, the left side of the image is to the patient's right and vice versa, while anterior in the image also is the patient's anterior and vice versa.
- 52. Approach to CT •Check name ,identification and date of study, orientation. • Start from upper most or lower most cuts. • Look from outside to inside or inside to outside. • Look for bones, sinuses,orbits. • Extradural, subdural and meningeal details and enhancement if contrast film.
- 53. Approach to theCT • Look parenchyma for hypodensities ,hyperdensities, their location, shape, homogenous/heterogenous,any mass effect or odema. • Grey-white matter differentiation, any enhacement if contrast film. • Ventricles symmetry and cisterns any effacement.
- 55. Density of variousstructures
- 56. Hyperdensities • Blood. • Clot •Calcium. • Prosthesis. • Contrast uptake. • Choriod plexsus calcification and bone are the do main hyperdensities that are present in normal CT.
- 57. Hypodense • Most commonlyodema secondary to: • Infection • Inflamation. • Stroke. • Mass lesion. • Fat containing structures. • Air • Paranasal sinuses and mastiod are structures that are hypodense in normal cases.
- 58. Approach to theCT • Explain the findings in systematic manner. • Mention the Shape, size, density, location and extent and any mass effects related to the findings. • Compare to the other side if applicable. • Any contrast uptake. • Formulate major or likely differentials related to observed findings. • What further imaging or test may be helpful to clear likely diagnosis.
- 59. Causes of air •Air filled spaces. • Base of the skull fracture. • Craniotomy or after other surgeries
- 61. Disorders of Sinuses •Acute bacterial sinusistis. • Chronic purulent sinusitis. • Fungal infection. • Mucocoele. • Tumors.
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- 68. Sinus tumor withwidespread intracranial extension
- 69. Sinus disease withorbital extension
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- 73. Grey and whitematter differentiation • Normally Grey matter is outer denser structure and white matter in inner hypodenser. • Grey matter contains neurons cell bodies while white matter contain axons with rich fatty myelin sheath making it hypodense. • This differentiation is loss in case of cerebral odema.
- 74. Normal Grey whitematter
- 75. Causes of cerebralodema • Infection. • Mass lesion. • Stroke. • Metabolic causes.
- 79. • In trueisolated cytotoxic oedema little change is evident on CT as a mere redistribution of water from extracellular to intracellular compartments does not result in attenuation changes. The changes colloquially ascribed to 'cytotoxic oedema' are in fact mostly due to ionic oedema, and are described separately. This is why brain CT is often normal in patients with an acute ischaemic stroke.
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- 82. • grey-white matterdifferentiation is maintained and the oedema involves mainly white matter, extending in finger-like fashion • secondary effects of vasogenic oedema are similar to cytotoxic oedema, with effacement of cerebral sulci, with or without midline shift
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- 92. Disoders of CSFspaces • Hydrocephalus communicating and non communicating including IIH,NPH. • Loss of csf spaces usually secondary to degenerative and other secondary processes.
- 100. CNS herniations • Thereare a number of different patterns of cerebral herniation which describe the type of herniation occurring: • subfalcine herniation • transalar herniation: ascending and descending • transtentorial herniation – downward: uncal herniation – upward: ascending transtentorial herniation* • tonsillar herniation* • extracranial herniation
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- 106. Trauma • Soft tissueinjuries. • Skull fractures. • Extradural,subdural and subarachniod hemorrhage. • Contusions and diffuse axonal injury with associated cerebral odema.
- 107. Skull fracture withextradural hematoma
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- 110. Skull base fracturewith pneumocephalus
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- 117. Vascular Insults • SubarachniodHemorrhage. • Lobar and basal ganglia bleeds. • Ischemic strokes. • Venous infarcts. • Disections
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- 129. Cerebellar infarct withhemorrhagic conversion
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- 139. Infections • Meningial enhancementand thickness, extradural and subdural collection, with associated communicating hydroceph. • Focal parenchymal injury and abscess, mass lesions with mass affects. • Ventriculitis and diffuse cerebral odema.
- 144. • Tumors andmasses. • Congenital abnormalities. • Toxic metabolic insults. • Disections and aneurysms. • Hypoxic injury. • States where CT is useless.
Editor's Notes
- #4 Pic referennce:Medscape.