CT Scan - What You Need to Know About Computed Tomography

A computerized tomography scan (often abbreviated as CT or CAT) is a painless imaging technique used to detect medical conditions that usually require invasive surgery or post-mortem examination for diagnosis.

This imaging process, known as a CT scan or sometimes called CAT scan (axial computerized tomography), captures detailed internal views of the body.[1]

Understanding CT Scan (CAT scan, Computed Tomography) and its Function

A tomograph is a medical device that combines multiple X-ray images, which are then processed by specialized software to create three dimensional representations of organs, bones, or blood vessels. This enables healthcare providers to examine internal structures with great accuracy.[2]

The term “tomography” comes from Greek roots: “tomos,” which means “slice” or “layer,” and “graphos,” which translates to “drawing” or “recording.” This technology was developed independently by two scientists - Godfrey Hounsfield from EMI Laboratories in the UK [3] and Allan Cormack from Tufts University in the USA. [4]. Their work, which transformed diagnostic medicine, earned them the Nobel Prize in 1979.[5]

Curious about viewing CT scans with Scriptoware?

With Scriptoware’s integrated DICOM Viewer, you can effortlessly review your CT images online at any time, whether through a web browser or mobile device. Your scans are safely stored within your Scriptoware account on the secure cloud PACS system.

How does a CT scan compare to an MRI?

While both CT scans and MRIs are advanced imaging tools used in healthcare, they rely on very different methods. MRI, or magnetic resonance imaging, creates detailed views of organs and tissues using magnetic fields combined with radio waves. On the other hand, a CT scan (computed tomography) relies on X-ray technology to capture detailed internal images. [6]

Sometimes, doctors use a special dye known as contrast material to improve the clarity of the images. This can help highlight blood vessels, tumors, or specific tissues.

Contrast agents can be delivered in several ways: through a vein (usually in the arm), inserted into the rectum, injected into a joint space, or taken by mouth. When swallowed, the contrast allows doctors to better distinguish the loops of the intestines from surrounding areas, making it easier to study the digestive tract.

How does a CT scanner function?

X-ray machines work by passing radiation through the body, which is absorbed differently by various tissues based on their density, creating shadow-like images in shades of gray.

A CT scanner takes this a step further. The patient lies on a platform that moves slowly through a circular machine. As the table moves, an X-ray source spins around the body, capturing many thin image slices from multiple angles. These are processed by a computer, which reconstructs detailed cross-sectional pictures or even 3D models. Advanced software can even remove bone layers digitally to better reveal soft tissues underneath.

For the scan to be precise, the patient needs to lie perfectly still, but the process itself is quick and completely painless. Normally, no special preparation is needed unless contrast material is being used. In such cases, the patient may be asked to arrive 60–90 minutes early so the contrast has time to spread to the target area, like the intestines.

Depending on what’s being examined, patients might also be instructed to avoid eating or drinking for several hours beforehand.

What areas can a CT scan examine in children?

CT technology can image almost any part of the body, offering full-body scans or focused views. This includes regions like the brain, chest, abdomen, neck, pelvis, arms, and legs. It’s also highly effective for studying organs such as the heart, lungs, liver, pancreas, kidneys, stomach, intestines, bladder, adrenal glands, spinal cord, blood vessels, and bones.

Types of CT Imaging Procedures

• Brain and Head Scans
  These scans evaluate various brain regions, typically used when there are signs of tumors, strokes, abnormal blood vessels, bleeding inside the skull, or enlarged lymph nodes and glands near the head and neck. This category includes imaging like cerebral vessel angiography CT, scans of the frontal bones, skull, inner ear structures, mastoid area, sinuses, and temporal bones.
• Abdominal and Pelvic Imaging
  This group focuses on producing detailed images of organs located in the abdomen and pelvis, including the liver, pancreas, kidneys, spleen, adrenal glands, stomach, and intestines. Examples include abdominal blood vessel angiography, combined abdomen-pelvis scans, and virtual colonoscopy (Colo-CT).
• Spinal Imaging
  Spine CT exams help pinpoint the reasons behind pain in the back, neck, or limbs by detecting issues such as slipped discs, spinal canal narrowing (stenosis), fractures, or bone cracks. This set covers scans of the neck (cervical), mid-back (thoracic), lower back (lumbar), and specific spinal sections.
• Limb Scans
  These scans provide detailed views of the bones and joints in the arms and legs, assisting in diagnosing problems in the shoulders, elbows, wrists, hands, hips, knees, ankles, and feet. This category involves limb blood vessel angiography, scans focused on particular bones or joints, and 3D image reconstruction.
• Chest Imaging
  Chest CT scans concentrate on the thorax, capturing detailed views of the heart, lungs, airways, and other chest organs. This includes chest angiography, routine chest scans, and high resolution imaging for lung evaluation.

What are the possible risks linked to CT scans?

As with any medical procedure, undergoing a CT scan carries some inherent risks, some common to many diagnostic tests and others specific to CT imaging. These risks often depend on the individual’s health status and medical background.

Before proceeding, the physician will carefully consider each case by weighing the diagnostic benefits of the CT scan against any potential hazards. This evaluation is done jointly with the patient to reach the best-informed decision.

Patients must also disclose any relevant health information such as pregnancy, as this may affect the choice to perform the scan.

• Radiation Exposure Concerns
  A common concern about CT scans is the exposure to radiation. People naturally encounter various sources of radiation daily including sunlight which is a significant contributor.

  CT scans use X-ray beams to generate images which means patients receive an extra amount of radiation during the exam. While the dose is relatively low, it is advisable to avoid multiple scans unless absolutely necessary.

  The radiation dose is carefully calibrated to provide clear diagnostic images while keeping exposure as low as reasonably achievable.

  Long term or excessive radiation exposure may increase the risk of cancer. For this reason, healthcare providers balance the advantages of performing the scan against the potential risks involved.

  Pregnant patients require extra caution since the developing fetus is more vulnerable to radiation than adults. A CT scan during pregnancy is only done if the expected benefits clearly outweigh the risks.

• Contrast Agents and Their Risks
  Contrast media often Iodine based improve the visibility of specific tissues like blood vessels and abdominal organs. They are usually administered either by mouth or injected intravenously. These substances are not radioactive and are typically cleared from the body through urine within hours.

  Although generally safe, contrast agents can cause side effects in a small number of cases. About 1% of patients might experience mild reactions such as nausea, vomiting, skin rash, or headaches which usually subside quickly. Serious allergic responses including anaphylaxis are extremely rare occurring in roughly 1 out of every 10,000 cases and require urgent medical treatment. Such severe reactions are unpredictable.

  For this reason, it is crucial that patients respond honestly and thoroughly to all questions when contrast agents are recommended, helping doctors reduce the chance of complications.

Common Questions

What conditions can a CT scan identify?

A CT scan, also referred to as a CAT scan (Computed Axial Tomography), is a widely used imaging technique in healthcare settings that helps detect a broad variety of health issues. This method utilizes a CT scanner, which combines X-rays with computer algorithms to generate detailed cross-sectional images of the body’s internal parts. There are different kinds of CT scans, including spiral CT, which continuously rotates around the patient to create quicker and more refined images.

Specialized doctors called radiologists interpret these images to help diagnose numerous ailments. CT scans can reveal fractures, tumors, infections, blood clots, heart-related conditions, and internal injuries. This imaging is especially useful for examining the brain, chest, abdominal organs, and pelvic region.

During the procedure, patients lie down on a motorized table that slides them into the scanner. The device then rotates around the patient, capturing multiple images from various angles. These individual images are combined to form a complete and detailed view of the area under examination.

Radiation exposure is a key consideration during CT scans. While the radiation levels used are generally within safe limits, they are higher compared to standard X-rays. Medical professionals carefully weigh the diagnostic benefits against the risks before proceeding.

In summary, CT scans are a critical diagnostic resource that offers precise visualization of the body’s internal structures, aiding in the detection and diagnosis of a wide range of medical conditions.

How long does a CT scan take?

The time needed for a CT scan varies based on the exam type, the body part being examined, and whether any special preparations are required. Below is an overview:

• Average Duration: Most CT scans last from 10 to 30 minutes, which includes preparation, positioning, and the scan itself.
• Type of Scan: Scan time varies by procedure:
  • Standard scans for the head, chest, or abdomen typically take about 10 to 15 minutes.
  • More detailed scans, such as those focusing on soft tissues, blood vessels, or vascular issues, may require extra time.
• Preparation Requirements: Some exams involve drinking contrast agents or receiving contrast injections intravenously, which can add an additional 15 to 30 minutes.
• Technology Speed: Modern CT scanners, particularly spiral or helical types, quickly collect detailed images by rotating continuously around the patient.
• Image Analysis: After scanning, radiologists need additional time to review the images and produce a diagnostic report. This process can take anywhere from a few minutes to an hour, depending on the case complexity.
• Special Considerations: For individuals undergoing cancer treatment planning or evaluation of artery disease, the CT session may be longer due to supplementary imaging and preparation.

To conclude, although the scanning portion may be brief, the entire process including setup and image interpretation usually lasts between 10 and 30 minutes. The scan produces a series of standardized images that can be stored on local servers or cloud PACS systems, allowing future comparison via a DICOM viewer.

References:

• https://www.webmd.com/cancer/what-is-a-ct-scan#1
• https://www.healthline.com/health/ct-scan
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5144463/
• https://www.britannica.com/biography/Allan-MacLeod-Cormack
• https://www.nobelprize.org/prizes/medicine/1979/summary/
• https://www.medicinenet.com/ct_scan_vs_mri/article.htm
• https://patient.info/treatment-medication/ct-scan#nav-1
• https://www.mayoclinic.org/tests-procedures/ct-scan/expert-answers/ct-scans/faq-20057860
• https://www.radiologyinfo.org/en/info.cfm?pg=safety-contrast#safety-benefits-risks