CT Scan vs MRI

A CT Scan and an MRI are different in the way they work, levels of harmful radiation, the equipment used, their cost and in the situations they are best suited for.

Comparison chart

Improve this chart CT Scan MRI
Principle: X-ray attenuation was detected by detector & DAS system, follow by math. model (back projection model) to calculate the value of pixelsm then become a imag. 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.
Details of soft tissues: Less tissue contrast compared to MRI Much higher detail in the soft tissues
Details of bony structures: Provides good details about bony structures Less detailed compared to CT scan
Ability to change the imaging plane without moving the patient: with capability of MDCT, after helical scan with Mlti-plane Reformation function. operator can constructe any plane. MRI machines can produce images in any plane
Principal used for imaging: Uses X-rays for imaging Uses large external field,RF pulse and 3 different gradient fields
Effects on the body: Despite being small, CT can pose the risk of irradiation. No biological hazards have been reported with the use of the MRI.
Acronym for: Computed tomography Magnetic Resonance Imaging
Scope of application: CT can outline bone inside the body very accurately. MRI is more versatile than the X-Ray and is used to examine a large variety of medical conditions.
Cost: CT Scan costs range from $1,200 to $3,200; they usually cost less than MRIs. MRI costs range from $1200 to $4000 (with contrast); which is usually more than CT scans and X-rays, and most examining methods.
Radiation exposure: Moderate to high radiation None
Time taken for complete scan: Usually completed within 5 minutes Scanning typically run for about 30 minutes.
Disadvantages: 1.Uses ionizing radiation 1.More scanning time 2.Patient with metallic implants are not recommended 3.Patient with phobia required to give anesthesia during scan
Application: Suited for bone injuries,Lung and Chest imaging,cancer detection Suited for ligament and tendon injury,spinal cord injury,brain tumors
History: The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield in Hayes, United Kingdom; the first patient brain-scan was done on 1 October 1971.
Image specifics: Demonstrates subtle differences between the different kinds of soft tissues.

Contents

edit How the scans work

edit MRI

Using a very powerful magnet and pulsing radio waves the detection coils in the MRI scanner read the energy produced by water molecules as they mis-align themselves after each RF alignment pulse. The collected data is reconstructed into a two dimentional illustration through any axis of the body. Bones are virtually void of water and therefore do not generate any image data. This leaves a black area in the images. MRI scanners are best suited for imaging soft tissue.

edit CT Scan

CT, Computerized Axial Tomography, uses xrays to generate images of the body, including bone. In the CT scanner the x-ray tube, (source) rotates around the patient laying on the table. On the opposite side of the patient from the tube is the x-ray detector. This detector recieves the beam that makes it through the patient. The beam is sampled via some 764 channels, (approximate number of channels). The signal received by each channel is digitized to a 16 bit value and sent to the reconstruction processor. Measurements are taken about 1000 times per second. Scan rotations are usually 1 to 2 seconds long. Each view/channel chunk of scan data is compared to calibration scan data of air, water and polyethelyne, (soft plastic) previously acquired in the exact same relative location. The comparisons allow the image pixels to have a known value for a particular substance in the body regardless of differences in patient size and exposure factors. The more samples, or views, the better the picture.

edit Pros and Cons

edit 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.

edit 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.

edit Video Explaining the Difference

This video explains all the different types of scans: Ultrasound, CT scan, MRI and PET scan. It's queued up to begin at the point where it explains CT scans and MRIs.

edit Related Articles

edit Examples (pictures) of MRI and CT Scan

An MRI of the left knee.
An MRI of the left knee.
The CT scan of a person's torso.
The CT scan of a person's torso.

edit References

Comments: CT Scan vs MRI

Comment anonymously

Anonymous comments

1 in 400 patents that recive a CT test get cancer from the raditation

71.238.1.196 on 2012-03-20 21:27:23

Government pays nothing. It all comes out of your pleated european pockets. "They" are completely controling your future and will cut your payments off when you decide to live a life style that does not fit "their" vision.

76.117.170.238 on 2012-01-18 01:47:55

People from countries where the government provides "free" (or very inexpensive) healthcare for their citizens often act as if nobody paid for the treatments. "I only paid 20 Euros!" or what ever. Do these people ever take a look at what the government takes out of their paycheck for taxes EVERY month? Nothing is free - especially when governments are involved. Good article - thank you!

184.8.231.70 on 2011-02-27 18:12:07

I had a CT scan in French hospital yesterday, and it cost me 44 euros. People were paying for MRI scans at the same desk and I think they were paying 73 euros. I had also to pay for the contrast solution - 50 euros. (Well, actually I shall get 70% of those costs back from the public health scheme and the rest on my private health insurance.)

77.197.235.192 on 2010-11-10 15:46:31

The costs that are listed as associated with either scan are the costs of performing the scan itself and vary with the part of the body that is being scanned, not the cost to the patient directly. That has to do with insurance plans. Something to consider heavily is what kind of insurance plan you have (if any) as this will affect both how much you pay and how much the hospital will have to eat due to provider network discounts, etc. A doctor/hospital/clinic that is less than ethical in their practices may push you towards a less expensive test/treatment to cut costs on their end or if they feel you won't be able to pay it off. Do your own research and ask LOTS of questions before YOU make the decision on what kind of test/treatment YOU think is appropriate. I'm not saying that you should discount what doctors are telling you. In my opinion, most doctors are honest and have devoted themselves to keeping people healthy and free of pain. But second opinions never hurt anyone.

165.206.209.230 on 2010-07-06 16:04:49

i had an MRI scan of my right knee at Apollo Ahmedabad, India for Rs 5130($125 approx). So saying that it costs 1000+ $ is not correct, atleast in India.

122.161.127.108 on 2010-03-01 20:32:59

they cost up to thousand dollars. _-''

62.49.8.114 on 2010-01-18 09:22:17

both are widely available in India : Ok???

121.242.137.215 on 2009-10-08 12:26:31

mine was free with my insurance....

99.6.174.175 on 2009-08-04 03:44:35

In India...

59.183.37.248 on 2009-05-06 16:03:32

not possible, even with full major medical insurance.

64.186.50.3 on 2009-03-10 13:36:10

only in your dreams

139.127.225.39 on 2009-01-27 00:34:45

I want to know where you can get a CT for $50 or a MRI for $200.

66.165.40.10 on 2008-12-04 18:43:45

Just seen an eye specialist at my local UK NHS hospital. He wants me to have a non urgent MRI to check for muscle damage. No cost, no drama. Should be scheduled within 2 weeks of seeing him and only 4 weeks after first going to my GP. Long live the National Health Service.

81.132.95.80 on 2011-01-10 17:15:03

Related Categories

  1. Health
  2. Diagnostics
Search for a comparison

Stay connected with Diffen:

Email
Print