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Neuroradiology

Neuroradiology. Dr Mohamed El Safwany, MD. Intended learning outcome. The student should learn at the end of this lecture neuroradiological Imaging. Neuroradiology. Plain Film CT US MRI Interventional Angiography Myelography Biopsy Nuclear Medicine. CT Basics.

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Neuroradiology

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  1. Neuroradiology Dr Mohamed El Safwany, MD.

  2. Intended learning outcome The student should learn at the end of this lecture neuroradiological Imaging.

  3. Neuroradiology • Plain Film • CT • US • MRI • Interventional • Angiography • Myelography • Biopsy • Nuclear Medicine

  4. CT Basics • Computed tomography (CT) • Computed axial tomography or computer –assisted tomography (CAT)

  5. CT Basics

  6. CT Basics • Neuroradiology • The BASICS of CT • Protocol • Terminology • Contrast • Radiation Safety

  7. CT Basics • Neuroradiology • The BASICS of CT • Protocol • Terminology • Contrast • Radiation Safety

  8. CT Protocolling • What happens when an exam is requested? • A requisiton is completed. • The requested exam is protocolled according to history, physical exam and previous exams. • The patient information is confirmed. • The exam is then performed. • Images are ready to be interpreted in … • Uncomplicated exam – 5-10 minutes after completion • Complicated exams with reconstructions take at least 1 hour but usually 1-2 hours.

  9. CT Protocolling • CT head protocols • 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

  10. CT Protocolling • 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

  11. CT Protocolling • Patient Information • Is the patient pregnant? • Radiation safety • Can the patient cooperate for the exam?

  12. CT Basics • Neuroradiology • The BASICS of CT • Protocol • Terminology • Contrast • Radiation Safety

  13. CT Terminology • Exams using Ionizing radiation • Plain film • CT • 1/10 of all exams • 2/3 OF RADIATION EXPOSURE • Fluoroscopy • Angiography, barium studies • Nuclear medicine • V/Q scan, bone scan

  14. CT Terminology • Attenuation • Hyperattenuating (hyperdense) • Hypoattenuating (hypodense) • Isoattenuating (isodense) • Attenuation is measured in Hounsfield units • Scale -1000 to 1000 • -1000 is air • 0 is water • 1000 is cortical bone

  15. CT Terminology • What we can see • The brain is grey • White matter is usually dark grey (40) • Grey matter is usually light grey (45) • CSF is black (0) • Things that are brite on CT • Bone or calcification (>300) • Contrast • Hemorrhage (Acute ~ 70) • Hypercellular masses • Metallic foreign bodies

  16. CT Terminology • Voxel • Volume element • A voxel is the 2 dimensional representation of a 3 dimensional pixel (picture element). • Partial volume averaging

  17. CT Terminology

  18. CT Terminology • Window Width • Number of Hounsfield units from black to white • Level or Center • Hounsfield unit approximating mid-gray

  19. CT Terminology

  20. CT Artifacts

  21. CT Terminology • Digital reading stations are the standard of care in interpretation of CT and MRI. • Volume of images • Ability to manipulate and reconstruct images

  22. CT Terminology • DICOM • Digital Imaging and Communications in Medicine • DICOM provides standardized formats for images, a common information model, application service definitions, and protocols for communication.

  23. CT Basics • Neuroradiology • The BASICS of CT • Protocol • Terminology • Contrast • Radiation Safety

  24. Contrast • Iodinated • Water

  25. Contrast • Types of iodinated contrast • Ionic • Nonionic - standard of care • No change in death rate from reaction but number of reactions is decreased by factor of 4. • If an enhanced study is needed, patient needs to be NPO at least 4 hours and have no contraindication to contrast, ie allergy or renal insufficiency.

  26. Contrast • What are the risks of iodinated contrast? • Contrast reaction • 1 in 10,000 have true anaphylactic reaction • 1 in 100,000 to 1 in 1,000,000 will die • Medical Issues • Acute renal failure • Lactic acidosis in diabetics • Cardiac • Extravasation

  27. Contrast • Who is at risk for an anaphylactic reaction? • Patients with a prior history of contrast reaction • Patients with a history asthma react at a rate of 1 in 2,000 • Patients with multiple environmental allergies, ie foods, hay fever, medications

  28. Contrast • Pretreatment for anaphylaxis • 50 mg Oral Prednisone 13, 7 and 1 hour prior to exam • In emergency, 200 mg iv hydrocortisone 2-4 hours prior to exam

  29. Contrast • What are the risk factors for contrast induced acute renal failure? • Pre-existing renal insufficiency • Contrast volume • Dehydration • Advanced age • Drugs • Multiple myeloma • Cardiac failure

  30. Contrast • Considerations in patients with renal insufficiency • Is the exam necessary? • Is there an alternative exam that can answer the question? • Decrease contrast dose

  31. Contrast • Contrast induced renal failure • Elevated creatinine 24-48 hours after contrast which resolves over 7-21 days. • Can require dialysis

  32. CT Basics • Neuroradiology • The BASICS of CT • Protocol • Terminology • Contrast • Radiation Safety

  33. Radiation Safety • Diagnostic CT Scans: Assessment of Patient, Physician, and Radiologist Awareness of Radiation Dose and Possible Risks

  34. Radiation Safety • Deterministic Effects • Have a threshold below which no effect will be seen. • Stochastic Effects • Have no threshold and the effects are based on the dose x quality factor.

  35. Radiation Safety • Terminology • Gy = Gray is the absorbed dose (SI unit) • The equivalent of 1 joule/kg of tissue • Rad = radiation absorbed dose • Sv = Sievert is the dose equivalent (SI unit) • Absorbed dose multiplied by a quality factor • Rem = radiation equivalent man

  36. Radiation Safety • Relative values of CT exam exposure • Background radiation is 3 mSv/year • Water, food, air, solar • CXR = 0.1 mSv • CT head = 2 mSv • CT Chest = 8 mSv • CT Abdomen and Pelvis = 20 mSv -The equivalent of 200 CXR

  37. Radiation Safety • Effects of X rays. • Absorption of photons by biological material leads to breakage of chemical bonds. • The principal biological effect results from damage to DNA caused by either the direct or indirect action of radiation.

  38. Radiation Safety • Tissue/Organ radiosensitivity • Fetal cells • Lymphoid and hematopoietic tissues; intestinal epithelium • Epidermal, esophageal, oropharyngeal epithelia • Interstitial connective tissue, fine vasculature • Renal, hepatic, and pancreatic tissue • Muscle and neuronal tissue

  39. Radiation Safety • The pregnant patient • Can another exam answer the question? • What is the gestational age? • Counsel the patient • 3% of all deliveries have some type of spontaneous abnormality • The mother’s health is the primary concern.

  40. Text Book David Sutton’s Radiology Clark’s Radiographic positioning and techniques

  41. Assignment Two students will be selected for assignment.

  42. Question Describe variables in CT protocoling?

  43. Thank You

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