Utility of Imaging Modalities in Neurological disorders |
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Objectives:
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Topics that will be covered: Brain
Spine
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Skull x-Ray PA viewSkull x-rays are rarely used in the modern days for evaluation of neurological problems. CT and MRI have replaced plain x-rays. It is primarily useful to evaluate skull bones, base of skull and sinuses. It used to be the initial imaging study in head trauma. CT has replaced skull x-rays as the initial imaging study for trauma and to evaluate skull and sinuses. Skull x-rays have not been useful to evaluate brain and intracranial contents. MR is the current imaging modality for that purpose. |
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Skull x-Ray Lateral viewSkull x-rays can detect bony abnormalities.
CT is superior to plain films in evaluating skull bones and sinuses. MR is the optimal study for evaluating intracranial structures brain, meninges, ventricles etc. |
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CT scan of the BrainAdvantages:
Disadvantages:
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MRI Scan of the BrainAdvantages:
Disadvantages:
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Ultrasound (US)US does not penetrate bone easily. Hence, it's not useful with adult head. It is useful in children where fontanels are not closed. US of normal neonatal child is shown on left. No radiation is involved with US and hence, ideal for use in neonatal skull. Children have unique neurological problems like congenital abnormalities, brain tumors and hydrocephalus where US is useful. It is a non-invasive study with no complications and can be done by the bedside. |
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Ultrasound (US)Normal neonatal child |
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Digital Subtraction Contrast AngiogramAn angiogram uses iodinated contrast agent to make the blood vessels visible under x-ray. It requires arterial puncture (femoral artery commonly used) followed by advancement of guide wire. Then a catheter is advanced over guide wire to desired location of the vessel. Contrast is injected and pictures are taken rapidly before the dye dissipates. Advantages:
Disadvantages:
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CT angiogram (CTA)In CTA contrast material is injected into a vein to produce detailed images of blood vessels. CT imaging produces multiple images and the computer joins them together in multidimensional views. Advantages:
Disadvantages:
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MR AngiogramMR angiogram, unlike CT angiogram and invasive digital subtraction angiogram, does not display the lumen of the vessel, but rather the blood flowing through the vessel. Contrast is not required for the study, which is an advantage. Circle of Willis is shown in the adjacent box. MR angiogram is less sensitive in detecting smaller intracranial vessels when compared to CT angiogram. MR angiogram is a screening test. |
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Plain film of lumbar spineX-rays are widely available to rule out gross fractures, vertebral pathology or spinal instability. Normal lateral lumbar spine shown on left. Plain films of spine can detect
Plain films of spine are usually the starting imaging study for back pain either based on clinical examination or bone scan. CT scan is done if further evaluation of bony lesions is necessary. MR is done for evaluation of spinal cord, dura, nerve roots and disc. |
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CT cervical spineNormal CT cervical spine shown on left. CT scans are commonly used to identify vertebral bone pathology. CT scans are axial images.
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Reconstructed CT cervical spineCT studies are axial images. Images can be reconstructed for better assessment of the extent of the lesion and relationship to other structures. |
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Normal CT cervical spineCT scans are commonly used to identify vertebral bone pathology.
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MR spineOptimal procedure for evaluating spinal cord and spine. MR provides exquisite detailed anatomy and alterations from any pathology. Various pulse sequences are utilized in MR to study the problem. T1 wtd image and Gadolinium contrast studies should always be looked as a pair of images. When there is enhancement with contrast it indicates that the blood brain barrier is broken. MR Spine T1 wtd image is seen on left. CSF is dark in T1 wtd image.
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MR spine T2 wtd image
Bone: Hypointense and appears gray CSF: Hyperintense and appears bright Cord and nerve roots: Hypointense and appears dark Disc: Hypointense and appears gray |
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Normal Axial MR ScanThis scan is taken below the level of the cord. The nerve roots (black) are seen floating in the CSF (white). Axial scans are useful to study disc herniation, compression on cord and neural foramen. |
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Normal Bone ScanWhole body nuclear bone scan, a screening test to rule out metastasis to the entire skeleton. Abnormal sites in bone scan will need further evaluation by CT scan. Normal bone scan in a patient with breast carcinoma. The study was done to rule out metastasis. |
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BMD test is the best way to identify patients with osteoporosis, determine risk for fractures and measure response to osteoporosis treatment. A DXA test measures bone mineral density and compares it to that of an established norm or standard to give a score. |
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Common indications for imaging study of the brain: Clinical symptoms:
Clinical signs:
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Common indications for MRI spine: Clinical symptoms:
Clinical signs:
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Identification of blood, air, fat, CSF and bone in imaging studies
Be familiar with the terms used in CT, MR and US and plain films. Each tissue is recognized by its unique characteristics. In addition with CT you can obtain Hounsfield units that specifically indicate which tissue we are dealing with. | |||||||||||||||||||||||||||||||||||||||||||
CT Head |
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MR spine T2 wtd. imageBone: Hypointense / Gray Disc: Hypointense / Gray CSF: Hyperintense / Bright Spinal cord and nerve roots: Hypointense / Dark Fat: Hyperintense / Bright |