Why would my healthcare provider order an MRI instead of a CT scan?

December 26, 2023 – 14 min read

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Radiologist Tech and Patient preparing for an MRI

Your healthcare provider has just ordered an MRI (Magnetic Resonance Imaging) scan for you. Why did they order an MRI scan instead of another imaging procedure, such as a CT scan? This is a legitimate question. To find the answer, let’s start with an understanding of the differences between the two imaging scans. 

The differences between MRI scans and CT scans

An MRI scan is good for some health issues, while CT scans are better for others. While both imaging techniques are used frequently, an MRI scan can produce more detailed images of soft tissues differentiating between the surrounding structures and internal organ structures than a CT scan

What is an MRI scan, and what kinds of conditions does an MRI diagnose?

An MRI scan uses strong magnetic fields to take pictures of the inside of the body. An MRI scan may be used to diagnose issues with soft tissue, joints, organs, the brain, the heart, and many other health conditions.

What is a CT scan, and what sort of conditions are diagnosed using a CT?

CT scans take a fast series of X-ray pictures, called slices, which are put together to create comprehensive images of the area that was scanned. CT scans are a useful screening tool for detecting possible tumors or lesions within the abdomen and other areas. A CT scan of the heart may be ordered when various types of heart disease or abnormalities are suspected. 

How does a CT scan differ from an MRI scan?

CT scans use a series of quick X-ray images that are compiled to create images of the area which is scanned. An MRI scan uses strong magnetic fields to take pictures of the inside of the body. 

Radiation exposure

When you hear the word radiation, the mind may immediately jump to negative images. In the field of diagnostic imaging, however, when radiation is used it is used safely and judiciously as possible to give medical providers accurate glimpses inside the body, greatly aiding in the diagnostic process.

Why is radiation exposure a concern in medical imaging?

Any time radiation is used, exposure is a concern. Excessive radiation can damage living tissue and increase the risk of cancer. Imaging providers minimize radiation doses while obtaining diagnostic images, ensuring that the benefits of the imaging procedure outweigh the risks to the patient.

How much radiation does a CT scan typically emit?

The amount of radiation emitted during a CT scan varies, depending on the type of scan, the specific machine used, and the body part being scanned. Typically, a single CT scan can deliver a radiation dose in the range of 1-10 millisieverts (mSv). For reference, the average radiation exposure a person receives in a year from natural sources is around 2-3 mSv. It’s important to discuss the risks and benefits of a CT scan with your healthcare provider, as they can provide guidance on when it’s necessary and how to minimize radiation exposure when possible.

How does an MRI work without using ionizing radiation?

An MRI scan works without using ionizing radiation. Instead, it relies on magnetism and radio waves. Here’s how it works: the patient is placed inside a strong magnetic field created by the MRI machine. This magnetic field aligns the hydrogen in the body’s water molecules. Radio frequency pulses are then applied to the body. 

Specialized detectors in the MRI machine capture the energy emitted by the hydrogen. The data collected is processed by a computer to create detailed images of the body’s internal structures, based on the varying relaxation times of different tissues. Since MRI scans don’t use ionizing radiation, it’s considered a safer option for imaging than techniques like X-rays or CT scans.

Woman with should pain needs a CT

Diagnostic precision and image quality

Whatever imaging scan your medical provider advises for you, it is very important that the equipment used is state-of-the-art and can produce the highest image quality possible. This will greatly assist your provider in diagnosing the issue and developing treatment plans.

What makes MRI a good choice for visualizing soft tissues?

MRI scans are a good choice for visualizing soft tissues for several reasons. They provide excellent contrast between different types of soft tissues, such as muscles, organs, and the brain, making it well-suited for diagnosing conditions in these areas. MRI scans allow for imaging in multiple planes, providing comprehensive views of soft tissues from different angles. 

MRI machines offer high-resolution images, allowing for the detection of subtle abnormalities and small lesions within soft tissues. What’s known as Functional MRI (fMRI) can be used to study brain activity, making it a valuable tool for understanding neural function. Unlike X-rays, which can be obstructed by bones, MRI scans are not significantly affected by bone, which allows for clear imaging of soft tissues near bones. 

An MRI scan can help differentiate between various soft tissue pathologies, such as tumors, cysts, and inflammatory conditions, based on their characteristics. Contrast agents can be used in MRI scans to enhance the visualization of specific soft tissues or abnormalities. Overall, an MRI scan’s ability to provide high-quality images with excellent soft tissue contrast and without radiation exposure makes it a preferred choice for evaluating many medical conditions involving soft tissues.

Why do healthcare providers choose MRI scans for diagnosing brain, spinal, or joint conditions?

Healthcare providers often choose MRI scans for diagnosing brain, spinal, or joint conditions because it offers several advantages. MRI scans provide highly detailed images of soft tissues, making it ideal for detecting abnormalities in the brain, spinal cord, and joints, such as tumors, inflammation, or injuries. 

MRI scans using contrast agents can be used to enhance specific areas, making it easier to identify abnormalities and blood flow. They can distinguish between different types of soft tissues, like gray and white matter in the brain or ligaments and tendons in joints. Patients typically experience minimal discomfort during an MRI scan, making it well-tolerated by most individuals. MRI scans are generally safe for a wide range of patients, including those with allergies or sensitivities to contrast agents.

However, it’s worth noting that MRI scans may not be suitable for all situations, such as when a patient has certain metallic implants or is unable to remain still for an extended period. In such cases, healthcare providers may consider alternative imaging methods.

How does the quality of an MRI image compare to that of a CT scan?

As noted before, an MRI scan can produce more detailed images of tissues and organs than a CT scan. The quality of an MRI image and a CT scan image can vary depending on the specific clinical application and the patient’s condition. However, in general, MRI scans typically provide better soft tissue contrast compared to CT scans. It’s excellent for imaging organs, muscles, and the brain because it can differentiate between different types of soft tissues. 

CT scans use X-rays and involve ionizing radiation, which can be harmful in large doses. An MRI scan does not use ionizing radiation, making it safer in that regard. CT scans are better at visualizing bones and detecting conditions like fractures. They are also less affected by metal implants in the body, which can cause artifacts in MRI images. CT scans are generally faster than MRI scans, which can be important in emergency situations.

The choice between an MRI scan and a CT scan depends on what information the healthcare provider is looking for. The two types of scans are often used together to provide a more comprehensive view of a patient’s condition.

What kinds of medical conditions are better diagnosed with a CT scan?

CT scans are excellent at quickly assessing injuries, such as fractures, internal bleeding, or organ damage after accidents or trauma. CT scans can provide detailed images of the brain and are often used to diagnose conditions like tumors, hemorrhages, strokes, or structural abnormalities. CT scans are also helpful in detecting lung cancer, pulmonary embolism, and various lung disorders, as they can create detailed cross-sectional images of the chest. They can identify conditions like appendicitis, kidney stones, tumors, and various gastrointestinal problems. 

CT scans offer detailed views of bones and joints, making them valuable for diagnosing fractures, arthritis, and other musculoskeletal issues. They can visualize blood vessels and are used to detect aneurysms, blockages, and other vascular problems. In dentistry, CT scans are employed to assess teeth, jaws, and oral structures, aiding in the diagnosis of dental issues and the planning of oral surgeries. CT scans provide detailed images of the spine, helping to diagnose herniated discs, spinal fractures, and other spinal conditions. 

CTs are also crucial in cancer staging and monitoring, particularly for abdominal and pelvic tumors.

Conditions typically diagnosed using an MRI

MRI scans can diagnose a host of health issues. They can detect brain tumors, multiple sclerosis, stroke, and other conditions affecting the brain and spinal cord. MRI scans are also commonly used to visualize injuries or diseases in the bones, joints, and soft tissues, such as ligament tears, herniated discs, and arthritis. They can help in evaluating cardiac conditions, and detecting heart diseases and defects and identify issues in the liver, gallbladder, pancreas, and reproductive organs, including tumors, cysts, or abnormalities. Breast MRI scans are used to assess breast tissue and detect breast cancer in certain situations. MRI angiography is employed to examine blood vessels and identify issues like aneurysms, stenosis, or vascular malformations and MRI scans can assist in diagnosing lung problems, such as pulmonary embolism or lung cancer. 

They can also detect issues in the digestive tract, including Crohn’s disease, diverticulitis, or colorectal cancer. MRI scans are also used to identify kidney tumors, cysts, and to assess renal function. They can help in evaluating muscle or tendon tears, and various joint problems. MRI scans can also diagnose spinal cord compression, herniated discs, and spinal tumors. These are just a few examples, as MRI scans are a valuable tool for diagnosing a wide range of medical conditions by providing detailed images of the body’s internal structures.

Why is an MRI scan typically recommended for diagnosing neurological conditions?

An MRI scan is often recommended for diagnosing neurological conditions because it provides detailed images of the brain and spinal cord. It is a non-invasive scan that offers several advantages. MRI scans are excellent at differentiating between different types of brain tissue, helping identify abnormalities like tumors, lesions, or vascular issues. 

An MRI scan does not involve ionizing radiation, making it safer for repeated use compared to techniques like CT scans. MRI scans can produce images in various planes, allowing for comprehensive assessment of the brain and its structures, and can reveal even small structural and functional abnormalities, making it a valuable tool for early diagnosis and monitoring of neurological disorders. 

However, the choice of diagnostic imaging method depends on the specific condition and the clinical indications, and in some cases, other imaging modalities like CT scans or PET scans may also be used alongside MRI scans.

How does an MRI provide better images for orthopedic conditions?

MRI scans provide better images for orthopedic conditions compared to other imaging techniques like X-rays or CT scans because it offers several advantages. MRI scans are excellent at visualizing soft tissues like muscles, tendons, ligaments, and cartilage. This is crucial for diagnosing orthopedic conditions such as ligament tears, tendon injuries, and cartilage damage, which may not be clearly seen on X-rays or CT scans. MRI scans can produce images in multiple planes, allowing for a comprehensive view of the affected area from various angles, thus helping orthopedic specialists to better understand the anatomy and pathology of the region. 

An MRI scan can tell the difference between various types of soft tissues based on their water content and other properties. This ability helps in distinguishing between healthy and damaged tissues, aiding in accurate diagnosis. An MRI scan can detect orthopedic conditions at an earlier stage, allowing for prompt treatment and potentially better outcomes, especially in conditions like stress fractures or avascular necrosis. Functional MRI (fMRI) can be used to assess joint movement and muscle function, providing valuable information for surgical planning and rehabilitation.

However, it’s important to note that an MRI scan may not be suitable for all orthopedic cases, and the choice of imaging scans depends on the specific clinical situation and the information required by the orthopedic surgeon.

In what cases are MRIs used for detecting tumors or lesions?

MRI scans are a versatile imaging technique that provides detailed images of the body’s internal structures, making it a valuable tool for detecting tumors and lesions. MRI scans are often used to visualize and locate brain tumors, both benign and malignant. Breast MRI scans can be used to detect breast tumors and assess their extent, especially in women with a high risk of breast cancer. MRI scans can identify lesions, herniated discs, or spinal cord tumors, and they are useful for detecting tumors in the liver, pancreas, and other abdominal organs. Prostate MRI scans help in the evaluation of prostate cancer and the guidance of biopsies, and they can detect tumors in muscles, tendons, and other soft tissues. MRI scans can also identify abnormalities in joints, such as in the knee or shoulder and they can detect tumors in the pelvis, including ovarian and uterine tumors. MRI scans are valuable for identifying tumors in the spine and spinal cord, and they can detect lesions in the neck and head, including the thyroid gland and salivary glands.

How to schedule your MRI or CT appointment with us

Touchstone Medical Imaging offers CT scans in Arkansas, Colorado, Florida, Montana, Oklahoma, and Texas. 

Reach out to us at Touchstone, and we’ll help you schedule a mammogram appointment at an imaging center near you, today.

We’re here to help you get the answers you need.

An MRI scan uses magnetic fields and radio waves to create detailed images of the body’s internal structures, often diagnosing conditions related to the brain, spine, joints, and soft tissues.

A CT scan uses X-rays to create cross-sectional images of the body, often providing detailed views of bones, blood vessels, and tissues, while an MRI uses magnetic fields and is more suited for soft tissue imaging.

Radiation exposure is a concern because excessive or repeated doses can potentially lead to harmful effects on the body’s cells and tissues.

An MRI uses strong magnetic fields and radio waves to generate images, avoiding the need for ionizing radiation like X-rays used in CT scans.

 Healthcare providers may avoid recommending CT scans for certain patients due to concerns about radiation exposure, especially for populations more sensitive to its effects.

MRI is preferred for visualizing soft tissues due to its high contrast and detailed imaging capabilities, which are crucial for diagnosing conditions in areas like the brain or joints.

An MRI is often recommended for neurological conditions as it provides detailed images of the brain and nervous system, aiding in accurate diagnosis and treatment planning.

MRIs are used for detecting tumors or lesions as they can produce highly detailed images, allowing for early detection and precise localization of abnormalities in the body.