MRI vs CT Scan: What’s The Difference?

In this article, we compare MRI vs CT scan. The two imaging systems look virtually identical and both diagnostic imaging systems show clear images of the anatomy. So, what’s the difference between and MRI and CT scan? More importantly, which is the best imaging option for your diagnostic procedure?

This article showcases the key differences between MRI and CT scans Applying a few known imaging principles will simplify the process of identifying which procedure is best for your diagnostic needs.

What’s The Difference Between MRI and CT Scans?

MRI and CT scans both provide a non-invasive procedure to acquire high resolution images of the anatomy. These advanced diagnostic imaging systems provide a pain-free procedure to aid in the diagnosis of medical conditions. So what’s the difference?

First, MRI is often considered a “safer” imaging alternative when compared to CT scans. This is because MRI uses non-ionizing radiation in the form of radio frequency pulses to produce images. This is a non-invasive process and does not cause any known health risks.

CT scanners and MRI scanners are often mistaken for one another. The two imaging modalities look similar at first glance. Both imaging system produce images of the body and have a large aperture in the center of the machine. The similarities between MRI and CT systems just about end there. Let’s discuss some of the differences below.

What is an MRI scan?

An MRI scan is a medical diagnostic procedure that uses a powerful magnet and radio waves to generate a high definition images of the soft tissue and bones.

It is a pain-free, non-invasive procedure and utilizes non-ionizing radiation.

MRI stands for magnetic resonance imaging. An MRI scan involves the use of a powerful superconductive magnet to align molecules within the patient’s body (Magnetic). The RF subsystem employs tailored radio frequency sequences to flip these molecules in the anatomy (Resonance). Receivers in the MRI then detect the resulting molecular movement, and the acquired data is sent to high-speed reconstruction computers for processing, ultimately producing detailed images (Imaging).

Scan data is then reconstructed and sent to a radiologist for viewing. MRI comes with many advantages but also carries many safety limitations. Below we review some of those key limitations and how they can affect the patient experience.

What is a CT scan?

A CT scan produces images by utilizing a revolving x-ray tube to produce sequential axial images.

CT scans provide high definition images of the anatomy through a quick, pain-free, non-invasive procedure by utilizing ionizing radiation.

CT stands for computed tomography. The term “computed” refers to the method of using computer processing to generate images. “Tomography” refers to the technique of creating images of cross-sectional slices of the body. Hence, CT scans are named computed tomography because they utilize computer algorithms to generate detailed images of internal body structures from multiple angles.

High speed image reconstruction computers receive scan data via fiber optic connections. Concurrently, the CT reconstruction computer uses advanced algorithms to reformat the individual slices into 2D images and 3D models for easy viewing.

Are MRI and CT Scans the Same?

In short, an MRI scan is not the same as a CT scan, although they share many similarities. This can often lead to confusion when differentiating between the two systems. However, there are a few key differences that distinguish MRI scan from CT scans.

First, MRI uses magnetic fields and radio waves to create images, while CT scans use x-rays. Second, MRI is typically used when imaging soft tissue, while CT scans can be used to image both soft tissue and bones. Finally, MRI is typically more expensive than CT scans.

An MRI scan machine utilizes a large superconductive magnet and RF wave pulses to produce a reconstructed image of the anatomy.

CT scan machines work by utilizing an X-ray beam revolving about the axial plane to produce image slices. Reconstruction computers then splice the axial images to create a 3D rendering.

MRI and CT systems operate using entirely separate systems, but that is not to say that they don’t share some notable characteristics. Before identifying some of the key differences of an MRI vs CT scan, let’s identify some of the key characteristics of each imaging system.

MRI and CT Scan Radiation Exposure

One of the most important topics to address when listing the differences between an MRI scanner and a CT scanner is radiation exposure.

CT scanners utilize x-ray, a form of ionizing radiation, to produce diagnostic images. A small radiation risk is associated with CT scans. Radiologists adhere to the ALARA principle (as low reasonably allowable), as regulated by the U.S Nuclear Regulatory Commission, when considering patients for radiology exams.

Does MRI Use Radiation?

MRI does indeed use radiation but MRI utilizes a non-ionizing radiation in the form of radio frequency pulses. Non-ionizing radiation does not pose the same health risks as ionizing radiation, such as in x-ray. Non-ionizing radiation, the type of radiation utilized in an MRI scan poses no known health risks to the human body.

Does CT Scan Use Radiation?

CT scans use radiation in the form of x-ray, classified as ionizing radiation by the FDA, to produce images of the anatomy. Exposure to ionizing radiation should be limited, learn more below. Computed tomography scans are a valuable tool for diagnosing various medical conditions. The benefits of a CT scan often outweigh the minimal risk associated with radiation exposure. Always minimize exposure to ionizing radiation and follow all safety guidelines when in the CT scan room.

MRI vs CT Scan Design Differences

MRI magnets tip the scales at over 12,000 lbs. The cylindrical shape has a considerably larger footprint than a CT scanner. Meanwhile, the gantry of a CT system weighs in at just over 3,500 lbs and carries a slimmer profile design that resembles a donut.

The image below illustrates some key differences between a CT scanner and MRI scanner.

Scan times vary greatly between MRI and CT systems, this category is where CT scans shine.

Specifically, MRI scan times average 25 to 30 minutes.

Additional scan time may be required if contrast agent is required. CT scan times average less than 10 minutes, including contrast injection (if required.)

Computed tomography utilizes ionizing radiation (x-ray), while MRI scans use a powerful superconductive magnet and radio waves.

MRI vs CT Scan Images

It can often be difficult to distinguish whether you are viewing a CT vs MRI images. Understanding the basic theory of an MRI scan and a CT scan will help in identifying the differences when viewing MRI vs CT scan images. Below are some great examples of the imaging capabilities

MRI scan image examples

CT Scan image examples

Computed tomography is the preferred modality when imaging bony structure. Advanced reconstruction computers produce 2D and 3D images that are read to provide a diagnosis.

CT Scan vs MRI Scan Procedure

The MRI scan experience differs greatly from the CT scan experience. Both imaging modalities require patients to follow simple safety guidelines that are unique to each modality system. Patients are screened by MRI technologists and briefed about safety precautions At this point it is a good time to ask any questions that may be of concern to you.

After the screening process has been completed, patients are transported into a waiting room while the scan room is prepared for your imaging exam.

How long does an MRI Take?

Magnetic resonance imaging exams average 25 to 45 minutes. Patients can expect to check in with your imaging center up to an hour before your MRI scan.

An MRI scan utilizes a superconducting magnet to produce images, subsequently all patients must remove all metal prior to entering the MRI scan room. Additionally, hearing protection is required for patient to wear during the MRI scan sequences.

How long does a CT scan take?

CT scan times average less than 10 minutes, including time it takes to administer CT contrast agent (if required). Patients can expect to check in with your imaging center 30 minutes prior to your CT scan. A CT scan produces images by utilizing an x-ray beam revolving around the patient to produce high resolution images of the anatomy.

As a result, CT scan patients are outfitted with a lead shield to cover parts of the body that are not intended to be exposed to radiation.

How To Distinguish Between an MRI Scan Machine and CT Scanner?

CT scan rooms and MRI scan rooms have very distinctive sounds associated with each system. Hence, it is easy to identify MRI from CT scanners by the sounds coming from the scan room. Click here to learn more about MRI scan sounds.

MRI Scanner Background Noises

One of the most telltale signs that your are near an MRI scanner is the background chirping sound that is created by the MRI coldhead assembly. A distinctive, rhythmic sound can be heard in the background of every MRI scan room.

Listen to MRI sounds on the MRIPETCTSOURCE YouTube Channel: MRI Scan Sounds Inside Scan Room.

CT Scanner Background Noise

CT scan systems have some very unique sounds associated with the scan experience. High speed CT gantry cooling fans provide ambient background noise in the scan room. Patient monitoring devices also emit audible tones when tracking vitals. Lastly, CT tube rotor assemblies spin up to a high frequency before starting the CT scan.

Listen to CT scan sounds on the MRIPETCTSOURCE YouTube Channel: Brain CT Scan (Live View in Real TIme).

Shape of MRI scanner vs CT scanner

MRI and CT scanners carry different footprints due to their differing hardware requirements. Additionally, identify an MRI vs a CT scanner with the simple tips below.

Shape of MRI scanner

An MRI scanner is made up of a superconducting magnet coil submerged in a helium that contains liquid helium. MRI scanners tend to be cylindrical in shape due to the vessel that the superconducting magnet must accommodate.

Shape of CT scanner

CT scanner carry a slimmer profile as compared to an MRI scanner. Most of the major hardware on a CT scanner revolves around a main access and as a result, CT scanners tend to resemble a doughnut shape.

CT vs MRI: Advantages and Disadvantages

Hospitals and imaging centers often carry an array of imaging modalities to provide optimal care for patients in need of imaging service. Undoubtedly, there are many instances in the dynamic medical imaging environment where one imaging modality would be preferred over another. Below, we will be discussing some of the advantages one modality might have over the other.

What is the advantage of an MRI versus CT?

MRI scans have an advantage over CT scans when imaging soft tissue. Magnetic resonance image provide clear definition of anatomical structure. MRI offers the ability to selectively highlight, saturate, and suppress images that contain fat, liquids, and water. Magnetic Resonance Imaging is classified as a non-invasive imaging procedure because of its use of non-ionizing radiation.

What is the advantage of CT over MRI?

The main advantage that CT scans have over MRI scans is the ability to perform a full diagnostic exam in under 10 minutes. When seconds matter, CT scans are the optimal choice for a fast diagnosis of internal bleeding and trauma. The other advantage that CT scans have over MRI is the image definition when targeting bony structure. Computed tomography is unparalleled in providing high definition orthopedic images.

MRI vs CT: Which is Better?

MRI is better suited at detecting subtle changes in tissue, while CT scans provide more detailed images of skeletal structures. Choosing between MRI and CT for individual patient imaging depends on factors like patient history, urgency, and the specific anatomical region of interest. This decision is best left to radiology professionals that understand the patient’s history and can weigh the benefits with the risks of each modality.

MRI and CT scans aid in the diagnosis of a variety of medical conditions, each offering distinct advantages. A comprehensive care plan includes both modalities, strategically planning long-term care based on the patient’s medical needs.

Conclusion

That said, both MRI and CT scans have their own advantages and disadvantages. So when it comes to MRI vs CT scans, ultimately, the best imaging modality for a given patient depends on the specific clinical question being asked.

Distinguishing MRI vs CT scans is a simple process as long as you recognize the key characteristics of each image. Do you hear a rhythmic chirping in the background? That is one of the telltale signs your are near an MRI scanner. In addition, utilize similar simple tips listed in the article above to quickly distinguish MRI from CT scans. Are you looking for more in-depth resources? Visit our Youtube Channel for detailed breakdowns and replies to user requests.

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