difference bt CT scan and MRI
Advantages of MRI over CAT Scan
# A CAT scan uses X rays to build up a picture. MRI uses a magnetic field to do the same and has no known side effects related to radiation exposure. # MRI has much higher detail in the soft tissues. # One of the greatest advantages of MRI is the ability to change the contrast of the images. Small changes in the radio waves and the magnetic fields can completely change the contrast of the image. Different contrast settings will highlight different types of tissue # Another advantage of MRI is the ability to change the imaging plane without moving the patient. Most MRI machines can produce images in any plane. # Contrast agents are also used in MRI but they are not made of iodine. There are fewer documented cases of reactions to MRI contrast and it is considered to be safer than X-ray dye. # For purposes of tumor detection and identification, MRI is generally superior. However, CT usually is more widely available, faster, much less expensive, and may be less likely to require the person to be sedated or anesthetized. # CT may be enhanced by use of contrast agents containing elements of a higher atomic number than the surrounding flesh (iodine, barium). Contrast agents for MRI are those which have paramagnetic properties. One example is gadolinium. Iodine use may be associated with allergic reactions.
Advantages of CT Scan over MRI
# CT is very good for imaging bone structures. # Some patients who have received certain types of surgical clips, metallic fragments, cardiac monitors or pacemakers cannot receive an MRI. # The time taken for total testing is shorter than taken by MRI # MRI cannot be done in patients who are claustrophobic as the patient has to remain inside the noisy machine for about 20-45 minutes # It is cheaper than an MRI. A CT scan costs $1,200 to $3,200 while an MRI can cost up to $4,000.
CT scan: Used :
# For bone injuries, # Lung and Chest imaging, # cancer detection ( tumor detection)
MRI scan: Used :
# Suited for ligament and tendon injury, # Spinal cord injury, # Brain tumors
difference between T1 and T2 weighted images:
A tissue with a long relaxation time (T1 and T2 (like water)) is DARK in the T1-weighted image and BRIGHT in the T2-weighted image. A tissue with a short T1 and a long T2 Relaxation time (like fat) is BRIGHT in the T1-weighted image and GREY in the T2-weighted image.
CT scan: Definition :
CAT Or CT scans are a specialized type of x-ray. X-ray attenuation will be detected by detector & DAS system, follow by math. model (back projection model) to calculate the value of pixels and then become a image. Usually completed within 5 minutes
MRI scan: Definition :
Makes use of the fact that body tissue contains lots of water (and hence protons) which gets aligned to large magnetic field to produce net MDM vector.The decay of MDM is detected as MR signal.
MRI scan: Application:
Patient lies in cylinder that is a large magnet. The computer than sends radio waves through patient's body and collect the signal that is emitted from the hydrogen atoms in cells.This information is collected by an antenna and fed into a sophisticated computer that produces the images. These images look similar to a CAT scan but they have much higher detail in the soft tissues. Unfortunately, MRI does not do a very good job with bones.Scanning typically run for about 30 minutes.
Basic MRI scans types
T1 weighted :T1 is the longitudinal relaxation time.It indicates the time required for a substance to become magnetized. T2 weighted: T2 is the "transverse" relaxation time. It is a measure of how long transverse magnetization would last in a perfectly uniform external magnetic field
CT scan: Application:
The patient lies down on a couch which slides into a large circular opening.The x-ray tube rotates around the patient and a computer collects the results. These results are translated into images that look like a "slice" of the person.
