CAT Scans Unveiled. The Key Differences Between Helical and Spiral CT Explained


CAT scans, also known as CT (computed tomography) scans, are medical imaging procedures that use X-rays and computers to create detailed pictures of the inside of the body. There are two main types of CAT scans – CT scans and MRI (magnetic resonance imaging) scans. Both provide important diagnostic information to doctors, but use different technologies. CT scans combine multiple X-ray images taken from different angles to produce cross-sectional images of internal structures. MRI scans use strong magnetic fields and radio waves to generate 3D images based on the body’s natural magnetic properties. This article will provide an overview of these two key types of CAT scans, their similarities and differences.

CT Scans

CT stands for computed tomography. CT scans, sometimes called CAT scans, use a series of X-rays and a computer to create detailed images of the inside of the body (source). During a CT scan, the X-ray machine rotates around the body and sends beams through the body from different angles. Detectors in the machine measure the amount of radiation being absorbed by different tissues. The computer takes this information and converts it into cross-sectional images or “slices” of the part of the body being scanned.

CT scans provide much greater clarity and reveal more details than regular X-ray exams. They show internal organs, bones, soft tissues, blood vessels and blood flow in great detail. This allows doctors to assess organs for abnormalities and diagnose medical conditions. CT scans are often used to help plan procedures such as biopsies, surgeries or radiation therapy. They can also be used to guide needles during biopsies or other interventional procedures. In emergencies, CT scans can help diagnose life-threatening conditions quickly and minimize permanent damage (source).

MRI Scans

MRI stands for magnetic resonance imaging. MRI scans use strong magnetic fields and radio waves to generate detailed images of the inside of the body (Mayo Clinic, 2023).

During an MRI scan, the patient lies inside a large tube-shaped scanner. The scanner contains powerful magnets which produce a strong magnetic field that aligns atomic nuclei in the body. Radio waves are then pulsed to disturb this alignment, and this produces signals that are detected by the scanner. The signals are processed to build up a detailed image of the scanned area of the body (NHS, n.d.).

MRI scans can show soft tissues and organs in the body more clearly than other imaging tests like X-rays or CT scans. MRI is often used to diagnose and monitor conditions affecting the brain and spinal cord, joints, soft tissues, organs, and more. It can help identify tumors, bleeding, infections, diseases, structure abnormalities, and other issues.

MRI scans are often used to guide minimally invasive procedures like biopsies. The detailed images produced can help doctors safely insert needles or probes. MRIs may also be used to monitor the use of certain treatments, such as chemotherapy in cancer patients (Mayo Clinic, 2023).


CT scans and MRI scans both produce detailed images of the body, but they use different technology to do so. Here are some of the key differences:

Radiation: CT scans use X-rays, which are a form of ionizing radiation. MRI scans use strong magnetic fields and radio waves, which are considered safer and do not involve radiation exposure (Source:

Image types: CT scans provide excellent pictures of dense structures like bones, tumors, and blood vessels. MRI scans better visualize soft tissues, organs, ligaments, and cartilage (Source:–what-is-the-difference.h00-159616278.html).

Speed: CT scans are very fast, usually taking just a few minutes from start to finish. MRI scans take significantly longer, often 30 minutes or more (Source:–what-is-the-difference.h00-159616278.html).

Patient experience: CT scanners are open ring-like machines, while MRI scanners are tunnel-like and can make some patients feel claustrophobic. CT scans require the patient to lie still but no noise protection is needed. MRI scans require ear protection due to their loud noises (Source:

Uses of CT Scans

CT scans are preferred over MRI scans when imaging the lungs and bones. They are able to provide more detailed views of both hard and soft tissues. According to, CT scans are commonly used to diagnose disease or injury as well as plan medical, surgical, or radiation treatment.

Some common uses and areas where CT scans excel include:

  • Imaging lung tissue – CT scans provide excellent visualization of the lungs and are routinely used to diagnose conditions like pneumonia, lung cancer, and pulmonary embolism.
  • Evaluating bones, joints and trauma – CT scans can detect even small fractures and provide detailed views of complex joint structures.
  • Guiding biopsies and needle aspirations – Doctors can use CT scans to guide the placement of needles during biopsies and needle aspirations.
  • Radiation therapy – The detailed images from CT scans are used to pinpoint and target tumors during radiation therapy for cancer.
  • Detecting tumors and masses – CT scans are often one of the first tests ordered to evaluate suspicious masses or tumors found on X-rays or during physical exams.

Overall, CT scans are preferred when a high level of detail in bone, lung and soft tissue imaging is required. The quick scan times and ability to image blood vessels also make CT a go-to modality in emergency medicine and trauma.

Uses of MRI Scans

MRI scans are preferred for examining soft tissues in the body. They provide excellent contrast between the different soft tissues of the body, making them especially useful for detecting abnormalities in organs and other structures.

Some common uses of MRI scans include:

  • Imaging the brain and spinal cord to look for tumors, bleeding, injury, or other abnormalities.
  • Examining joints and muscles for injuries or diseases like arthritis.
  • Detecting cancers and evaluating their extent, especially in the breast, prostate, liver, and other organs.
  • Imaging the heart and major blood vessels to screen for cardiovascular disease.
  • Evaluating pelvic pain and abnormalities in women.
  • Assessing fetal development during pregnancy.

MRIs produce very detailed images and can find even small abnormalities, which makes them invaluable for closely examining soft tissues throughout the body without radiation.

Risks of CT Scans

CT scans expose patients to ionizing radiation, which can damage DNA and potentially cause cancer later in life. According to the Mayo Clinic, the amount of radiation in a CT scan is 100 to 500 times that of a standard x-ray. However, the risk of developing cancer from a single CT scan is quite small. The chances increase with multiple CT scans, especially for children and younger patients.

Some patients can have allergic reactions to the contrast dye used in CT scans. This dye contains iodine and can cause itching, nausea, vomiting, headache, and hives in those with allergies. Kidney damage is also a potential risk from the contrast dye, as it is filtered out through the kidneys. Those with kidney disease or diabetes are at higher risk of kidney problems from the contrast dye. However, screening tests can help identify those at risk prior to the CT scan.

Risks of MRI Scans

While MRI scans are considered very safe overall, there are some risks to be aware of. One of the most common risks associated with MRI scans is claustrophobia or feelings of anxiety from being in the enclosed MRI machine. According to research, up to 30% of patients experience some feelings of claustrophobia during an MRI scan.

Those with any medical implants, including pacemakers, surgical clips, or prosthetic devices, may not be able to have an MRI scan as the strong magnetic field can interfere with or dislodge the implants. In some cases, certain implants may be deemed “MRI-safe” if properly tested and approved.

There is also a small risk of an allergic reaction or side effects from the contrast dye used in some MRI scans. Some patients experience mild headaches, nausea or hives after receiving the contrast. More severe reactions like difficulty breathing are rare but can occur. Those with kidney problems may want to avoid the contrast dye due to potential kidney damage.

Overall, MRI scans are considered very low risk when proper safety guidelines are followed. However, those who experience claustrophobia, have medical implants, or concerns about contrast dye should discuss the risks and alternatives with their doctor.

Cost Comparison

CT scans tend to be significantly less expensive than MRI scans. According to CT Scan vs MRI: Differences Between Safety, Cost and Use, a CT scan in the United States without insurance costs around $300 to $6,750 and averages $3,275. In comparison, an MRI scan averages around $2,000.

There are a few reasons for the cost difference between CT and MRI scans. CT scanners are more widely available and the scans are quicker to perform, making them more efficient. The technology behind MRI scanners is more complex and requires specialized facilities, driving up the costs. MRIs also often require the use of contrast dye, adding to the price.

While CT scans are less expensive on average, both types of scans are often covered by insurance. With insurance, patients will likely pay a copay or coinsurance charge, which does not vary dramatically between CT and MRI scans. However, MRIs do require pre-authorization more frequently, which can delay scheduling. When determining which scan is appropriate, doctors factor in the clinical need first, before considering the costs.


In summary, the two main types of CAT scans are CT scans and MRI scans. While both provide detailed internal images, there are some key differences between the two.

CT scans use X-rays and are better for examining bone injuries, lung and chest imaging, and detecting cancers. MRI scans use radio waves and strong magnets and are preferable for examining soft tissues like organs, muscles, and ligaments.

CT scans are the modality of choice when speed is important, such as emergency cases, while MRI provides more detailed images but takes longer. CT scans have more radiation exposure risks compared to MRI scans. MRIs also tend to be more expensive and are not recommended for those with metal implants or severe claustrophobia.

Understanding the strengths and weaknesses of each type of scan can help doctors select the most appropriate imaging technique for a patient’s needs. With their combined capabilities, CT and MRI scans have greatly improved medical diagnosis and treatment.

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