You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Dye for myelography is injected in? and explain in detail?
Ans. c (Subarachnoid space). (Ref. Clark, Positioning in Radiography, 10th ed., 588)MYELOGRAPHY# Myelography is the radiographic investigation of the spinal canal for the diagnosis of space occupying & obstructive lesions & requires the contrast agent to be injected into the subarchnoid space (which lies between pia mater & the arachnoid mater) usually following a lumbar puncture.# Either a negative contrast agent like air or oxygen is used or more usually a positive non reactive water-soluble preferably non-ionic, organic iodine compound (Iohexol).# Nonionic iodinated compounds have replaced myodil (iophendylate) due to its advantages like freely miscible with CSF, flows along subarachnoid spaces around the nerve roots & is absorbed from subarachnoid space within 48 hours.# They are isotonic with CSF in concentration usually used for lumbar myelography, made upto a volume of 10 cc.# They also have low viscosity and thus a narrow bone needle can be used.# Reactions like headache, nausea seldom last for more than 24 hours.# Arachnoiditis is severe most complication, however with newer contrast, it is extremely uncommon.- Iohexol (omnipaque) is nonionic contrast commonly used today. Iohexol has more evenly distributed OH groups hence has less subarachnoid toxicity.# MRI has replaced myelography and CT myelography.