The Complete Guide To CT Scans
I am confident this is the most complete and comprehensive consumer guide you will find on the internet regarding CT scans.
In this guide, we will share with you our knowledge, life-changing stories, and experiences around medical imaging.
My name is Dr. Cristin Dickerson, founding partner of Green Imaging --- which is one of the leading full-service virtual medical imaging networks in the United States.
So if you're searching to learn as much as you can about CT scans, you will find value in our comprehensive guide.
DR. CRISTIN A. DICKERSON, MD
What Is A CT Scan?
Computerized Tomography (CT) Scan Overview
The computerized tomography (CT) scan procedure is now essentially a 3D version of the traditional x-ray examination. In essence, a CT scan is an x-ray volumetric acquisition of data from a part of the body. The images are reformatted by computers (hence computerized) to create standard cross-sectional and 3D images.
Brief Medical History of the CT Scan
Computerized tomography (CT) scan technology has been well established for over half a century. The first commercially available CT scan equipment was conceived in 1967 and installed in 1971, although the basis for the technology was demonstrated on several occasions well before that time. The roots of CT scan technology go all the way back to 1917 with the development of radon transform mathematics.
The first CT scan machines were primitive by modern standards. The first machines could only take cross-sections of a patient’s brain. Patients had to stick their heads into a water-filled tank which was necessary to lower the dynamic range of the x-ray radiation for detection purposes. Images produced by this early CT scanning machine could only produce images with a resolution of about 80 by 80 pixels. For comparison, the average resolution of a computer screen today is 1366×768. Modern CT scanning machines can resolve images 2048 by 2048 pixels.
Not long after the introduction of the first CT machines, researchers discovered how to make working scanners without the need for a tank of water. Over time, CT machines have rapidly advanced in terms of operating speed, slice count, image quality, and patient comfort. However, the fundamental idea behind CT scans has remained the same.
Types of CT Scans
CT scans can be employed for nearly any part of the human body. Depending on which part of a patient’s body is targeted for imaging, the exact procedures and techniques may differ somewhat. However, the overall concept remains the same.
Creating three-dimensional and cross-sectional images of the body part in question can help doctors better visualize hidden conditions within a patient's body, leading to more accurate diagnoses and better outcomes as a result.
The most common types of CT scans include CT scanning of the head, CT scans of the neck, CT scans for coronary calcium, CT angiographies (CTAs), CT scans of the chest, CT scans of the abdomen and pelvis, and CT scans of the spine.
CT Scan of Head
CT scans are well suited for imaging the head and brain. The very first commercial CT scanning machine could only image a patient’s head. Modern head scans can provide doctors a bevy of high resolution and accurate information on a patients head, including the soft tissues of the brain, the hard tissues of the skull, as well as the many intricate blood vessels in and around the head. The reliability of a CT head scan has made the procedure one of the standard diagnostic tools in hospitals worldwide.
A CT scan of the head can help doctors locate fractures in the skull bone, contextualize brain injuries, and detect bleeding or blood clots in the head. Head scans can also be used to visualize the extent and scope of traumatic damage to the face and head and help guide maxillofacial surgeons during reconstructive surgery. CT scans are also used to detect brain tumors, assess brain ventricles, assess disease in the paranasal sinuses, evaluate skull malformations, and even assess aneurysms through a CT angiography.
CT Scan of Neck
CT scans of the neck evaluate the nasal and oral cavities for disease, evaluate the size and lesions of the salivary and thyroid glands, evaluate the airway, and evaluate the lymph nodes in the neck.
CT Scan for Coronary Calcium
These scans are simple non-contrast scans of the heart, acquired to assess for the presence of atherosclerotic calcification in the coronary arteries. Computer software is used to quantify that volume of calcium. The software then compares that volume to a database that allows determination of a patient's risk of future adverse cardiovascular events like heart attack and stroke. It is in fact, the best noninvasive test we have to predict that risk and usually only costs a few hundred dollars.
CT Angiography (CTA)
CT angiographies (CTAs) are designed to visualize blood flow in regions of the body. This is extremely useful for a litany of important medical reasons. CTAs can be used to visualize and examine pulmonary embolisms, assess brain aneurysms and arteriovenous malformations, display highly accurate information on the renal arteries, and detect atherosclerotic disease. The application of CT technology for angiographical purposes has revolutionized how modern doctors visualize, detect, and treat all sorts of diseases from heart disease to stroke.
CT Scan of Chest
CT chest scans are often recommended after a traditional chest x-ray has detected something that may require further investigation. The detailed cross-section produced by a CT chest scan can either confirm previous findings and provide additional detailed information, or, determine that the earlier results were false-positive (artifactual).
CT chest scans are also particularly useful for the monitoring of individuals who are at a higher risk of developing lung cancer. Low radiation dose techniques have been developed for these scans to minimize the radiation risk of having annual CT scans.
CT Scan of Abdomen and Pelvis
Abdominal and pelvic scans using CT technology is an excellent diagnostic imaging technique for identifying a variety of issues including identifying abscesses in the abdomen or pelvis, inflamed bowel, diverticulitis, appendicitis, and assessing the presence and extent of cancers. CT scans of the abdomen are particularly good at imaging and visualizing liver, spleen, pancreas, adrenal glands, kidneys, and gastrointestinal (GI) tract.
CT Scan of Spine
CT scans are often recommended for diagnostic imaging of the spinal column due to the complexity of the human spinal column, including the presence of a wide variety of tissue types that include bone tissue, nerve tissue, muscles, blood vessels, and soft tissues, in a relatively condensed region of the body.
The intricate shapes and details of internal structures, such as delicate vertebrae bones, can be visualized in high resolution with CT technology. As a result, CT spine scans are commonly used to detect spinal injuries, tumors in the spinal column, metastases of other cancers, vertebral fractures, infections, and the presence of degenerative diseases such as arthritis.
CT Scan: Uses, Side Effects, Process, & Results
A CT scan is generally used as a clarifying diagnostic tool after a patient’s doctor has reason to suspect the presence of disease and a standard x-ray diagnostic has proven inconclusive and occasionally as a screening exam for lung cancer and coronary artery plaque.
In some cases, such as a head or neck injury, a CT scan may be the first diagnostic ordered to identify and diagnose bleeding or swelling in the brain quickly.
Examples of when a CT scan may be in order include:
Small or fine fractures
Imaging of complex structures
Imaging of organs and other soft tissues
Imaging for surgical planning purposes
CT Scan Side Effects
CT scan technology is built on x-ray technology. To produce detailed three-dimensional cross-sectional data for imaging and diagnostic purposes, a CT scan is like x-rays obtained at many different angles. As we know, x-rays produce strong gamma radiation that can damage cellular DNA and at high doses may cause cancer.
CT scans pose the same small but not insignificant radiation danger for patients. The risks of developing cancer as a result of a CT scan are about 1 in every 2,000 CT scan patients. While this number is small, repeated scans can increase a person’s risk of developing cancer.
The effects of radiation exposure can build up gradually over a long period. That’s why doctors only prescribe a CT scan only when necessary. To reduce a patient’s radiation exposure, CT scans are typically reserved as a clarifying diagnostic after a standard x-ray has detected something out of the ordinary.
As a result of the potential dangers of ionizing radiation, children and pregnant women are usually prohibited from receiving CT scans unless the potential benefits outweigh the long term danger posed by radiation exposure.
While radiation is a real concern, it is essential to understand that the risks are still minimal. Proper protection and operation are essential. Patients concerned about the potential side effects of CT scans should consult with their doctor.
3 Steps of a CT Scan Process
Preparation for a CT Scan is very straightforward with a few exceptions. In general, the only preparation needed for a CT scanning procedure is to change into a medical or hospital gown. Medical gowns promote general cleanliness and hygiene and ensure that no unintended items, such as keys or tiny fibers of clothing, make it to the CT scanning table.
Some CT scan procedures, such as an angiogram, may require the injection of scan-specific contrast agents and imaging dyes. In the case of an angiogram, patients must receive an injection of iodine which helps the CT scan visualize essential parts of the heart and blood vessels. Some CT scan procedures may also require patients to refrain from eating or drinking during a specific period leading up to a CT scan procedure. These important preparatory steps ensure the accuracy and efficacy of the CT scan.
Other scans require a patient to drink an oral contrast agent over a period of time prior to the exam to opacify the bowel loops for their better evaluation.
During a CT scan procedure, patients will be asked to lie down on the scanning table in a position most conducive for the particular CT scan required. Sometimes patients will lie on their back while other times they may be necessary to lie on their side.
Once in place, the technologist or radiologist will leave the room and enter an adjacent control room. The table slides beneath or into the CT scanning equipment.
Once in place, the CT machine begins taking cross-sectional images of the patient’s body. The table on which the patient lies may move slightly to take different images.
It is vital that a patient remains still during the CT scanning machine's operation.
After the procedure patients change back into their street clothes and can go about their day, the images from the CT scan are typically presented to a radiologist who then interprets the data. Based on the data provided, the radiologist will then provide a patient's physician with a report describing the findings along with professional recommendations and diagnoses.
CT Scan Results
Radiology reports, as well as the actual computed tomography images themselves, can be difficult for a non-professional to read or understand. Typically, the report, images, and professional recommendations or diagnoses are not sent to a patient, but rather to the patient’s primary care physician or another specialist who will then provide the information to the patient and correlate it with lab and clinical findings.
Reports are often chock full of medical terminology and healthcare jargon and are primarily intended for other medical professionals.
Generally, radiology reports are broken down into six sections:
1. Type of Exam
Here you will find the type of examination that was provided, such as a CT scan, MRI, or another diagnostic examination.
2. Clinical Information
This is where a patient’s clinical symptoms are communicated to the radiologist. Having a concise but thorough patient history here also helps the radiologist to interpret the data more accurately.
This section denotes other examinations and previously obtained data that may inform the radiologist’s interpretation.
This is where a radiologist describes the exact methodology used for the examination and other technical details.
This is by far the lengthiest part of any radiology report. Here, the radiologist will go into detail about his or her observations including whether or not specific parts of the body that were analyzed are normal or abnormal.
In this final section is where all the data and proceeding information is synthesized to generate a coherent diagnosis or diagnoses. Many important interpretations and answers to the clinical question(s) will be found in this section of a radiology report.