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MRI vs. CT Scan: What is the Difference?

MRI Head Scan

Medical imaging is a crucial component of modern orthopedic healthcare, providing invaluable insights that can help in the diagnosis, treatment, and monitoring of various medical conditions. Among the most commonly used imaging techniques are Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans, which are also called CAT scans for Computed Axial Tomography. 

While both are essential diagnostic tools, they serve different purposes and have unique advantages as well as limitations. This blog post explores the differences between MRI and CT scans, their working principles, benefits, applications, and patient experiences.

The importance of medical imaging

Medical imaging plays a pivotal role in contemporary medicine. It allows healthcare professionals to visualize the internal structures of the body non-invasively, facilitating early diagnosis, accurate assessment of diseases and injuries, and monitoring treatment progress. 

Imaging techniques like MRI and CT scans are indispensable in detecting conditions such as tumors, fractures, joint deterioration, infections, and vascular diseases, ultimately improving patient outcomes and reducing the need for exploratory surgeries.

Although diagnostic imaging has been around for decades, it remains one of the cornerstones of advanced orthopedics when determining the root cause of an issue.

What is an MRI?

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technique that uses powerful magnets, radio waves, and a computer to produce detailed images of the body’s internal structures, particularly soft tissues. 

Patient going into MRI

How MRI works

MIR operates on the principle of nuclear magnetic resonance. The human body is primarily composed of water molecules, which consist of hydrogen and oxygen atoms. The hydrogen atoms have protons that align with the magnetic field when a person is placed inside the MRI machine. 

The MRI machine generates a strong magnetic field and sends radio waves into the body. These waves disrupt the alignment of the hydrogen protons. When the radio waves are turned off, the protons realign with the magnetic field, emitting signals in the process. These signals are detected by the MRI machine and converted into detailed images by a computer.

Advantages of MRI

Detailed soft tissue imaging

MRI excels at providing high-resolution images of soft tissues, including the brain, spinal cord, muscles, ligaments, and internal organs. This makes it an invaluable tool for diagnosing conditions like brain tumors, spinal cord injuries, and joint abnormalities and decay. 

No radiation exposure

Unlike CT scans and X-rays, MRI does not use ionizing radiation, making it a safer option, especially for repeated imaging or for more vulnerable patients such as children and pregnant women. 

Multiplanar imaging

MRI can produce images in multiple planes. The different planes that radiologists use are axial (divides the body into top and bottom halves), coronal (perpendicular), and sagittal (midline of the body), offering comprehensive views of the areas being examined. 

Common applications of MRI in medicine 

  • Orthopedics: Assessing joint injuries and degradation, cartilage damage, and spinal disorders.
  • Neurology: Diagnosing brain tumors, stroke, multiple sclerosis, and other neurological conditions. 
  • Cardiology: Evaluating heart structures, detecting congenital heart defects, and assessing the viability of the heart muscle.
  • Oncology: Identifying and staging tumors, particularly in the brain, breast, and prostate.
  • Gastroenterology: Imaging the liver, pancreas, and bile ducts for conditions like cirrhosis, tumors, and bile duct obstructions.

What is a CT scan?

Computed Tomography (CT) or Computed Axial Tomography (CAT) is an imaging technique that combines X-ray measurements from different angles and uses computer processing to create cross-sectional images (slices ) of bones, blood vessels, and soft tissues inside the body. 

How CT scans work

During a CT scan, the patient lies on a motorized table that slides into a circular opening of the CT scanner. Shaped much like a donut, the scanner houses an X-ray tube that rotates around the patient, emitting X-rays. These X-rays pass through the body and are detected by sensors on the opposite side of the scanner. The data collected by the sensors is processed by a computer to create cross-sectional images. These images can be combined to form a detailed 3D representation of the body’s internal structures. 

CT Scan With Tech

Advantages of CT scans

Faster image acquisition

CT scans are quick, typically taking just a few minutes, making them ideal for emergency situations where fast diagnosis is critical. 

Better for bone and dense tissue imaging

CT scans provide excellent images of dense structures like bones, making them highly effective for diagnosing fractures, spinal injuries, joint deterioration, and detecting calcifications. 

Detailed visualization of complex structures

CT scans are particularly useful for imaging complex structures like the chest, abdomen, and pelvis, providing detailed views that aid in diagnosing conditions such as lung diseases, kidney stones, and abdominal tumors. 

Common applications of CT scans in medicine

  • Emergency medicine: Quickly assessing traumatic injuries, internal bleeding, and fractures. 
  • Cardiology: Evaluating coronary artery disease, pulmonary embolism, and aortic aneurysms.
  • Oncology: Detecting and monitoring tumors, guiding biopsies, and planning radiation therapy.
  • Pulmonology: Diagnosing lung conditions such as pneumonia, emphysema, and lung cancer.
  • Gastroenterology: Imaging the liver, spleen, kidneys, and intestines for conditions like appendicitis, diverticulitis, and liver tumors. 

How doctors decide which to order

The choice between MRI vs. a CT scan depends on various factors, including the type of tissue being examined, the patient’s medical history, and the urgency of the situation. 

  • Tissue Type: For soft tissue imaging, such as the brain, spinal cord, or muscles, MRI is usually preferred due to its superior resolution. For bone and dense tissue imaging, such as fractures or lung conditions, CT is more effective.
  • Medical history: Patients with a history of conditions or contradictions (such as pacemaker, insulin pumps, and metal implants) may not be suitable for MRI due to the strong magnetic field.
  • Urgency: In emergency situations where a fast diagnosis is necessary, CT scans are typically chosen due to their speed. 

 

In orthopedic medicine, an MRI can confirm a shoulder labrum tear, while a CT scan is useful when a surgeon is trying to see very fine bone detail.

Patient experience: MRI vs. CT scan

The MRI experience

MRIs take longer, typically ranging from 30 to 60 minutes. Patients lie in a narrow, tube-like machine, which can be claustrophobic for some. If this is the case, practitioners can order an open-bore MRI. Open-bore MRIs have a magnetic top and bottom, with four open sides and a large space in between for the patient to lie. This design can make the machine more comfortable for patients who are claustrophobic, obese, or have broader shoulders, and it can also allow physicians to perform exams with the patient’s head outside of the magnet. 

The procedure may be noisy due to the loud tapping or thumping noises produced by the machine. Patients are often given ear plugs and/or headphones to wear during the procedure, and can often choose a style of music they find soothing to listen to.

Patients may also receive a contrast agent injection to enhance image quality. 

CT Scan

The CT scan experience

CT scans are much quicker than MRIs and often take just a few minutes. Because patients lie on a table that moves through a large, donut-shaped machine, the experience is less confining than a closed-bore MRI, which is a long, narrow tube. 

Depending on the scan, patients might need to drink a contrast material or receive an intravenous injection of contrast dye to improve image clarity.

MRI vs. CT scan? Both are indispensable in modern medical imaging

Generally speaking, CT scans are better at spatial resolution, while MRIs are superior for contrast resolution. That means CT scans are good at showing where the edges of things are and where one structure ends and another begins. MRIs excel at showing the differences between various parts of the body and show where diseased tissue stands out from normal tissue. 

The choice between the two depends on the specific medical scenario, with orthopedic surgeons often considering factors like the type of tissue to be examined, patient history, and urgency. At times, CT scans are ordered first, and can be followed by an MRI if the physician requires a more detailed view of specific parts of the body. 

Some orthopedic practices have on-site MRIs. Here at the office of Dr. Omar D. Hussamy we use an Esoate S-Scan, a powerful MRI machine that can show problems that can’t be detected by X-ray, ultrasound, or CT scan alone. Our machine is open-sided and ideal for patients who are claustrophobic. Our knowledgeable MRI techbiologists make patients feel comfortable throughout the entire process.

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