Computerized Tomography (CT) Scan
CT or CAT Scan Overview
A computerized tomography (CT) or computerized axial tomography (CAT) scan combines data from several X-rays to produce a detailed image of structures inside the body.
A CT scan can be compared to looking at one slice of bread within a whole loaf. CT scans are used in hospitals worldwide for diagnosis purposes.
Computerized tomography (CT) scan combines a series of X-ray images taken from different angles around the body and uses computer processing to create cross-sectional images (slices) of the bones, blood vessels and soft tissues inside your body.
CT scan images provide more-detailed information than plain X-rays do.
How does a CT scan work?
A CT scanner emits a series of narrow beams through the human body as it moves through an arc.
This is different from an X-ray machine, which sends just one radiation beam. The CT scan produces a more detailed final picture than an X-ray image.
The CT scanner’s X-ray detector can see hundreds of different levels of density. It can see tissues within a solid organ.
This data is transmitted to a computer, which builds up a 3-D cross-sectional picture of the part of the body and displays it on the screen.
Sometimes, a contrast dye is used because it can help show certain structures more clearly.
For instance, if a 3-D image of the abdomen is required, the patient may have to drink a barium meal. The barium appears white on the scan as it travels through the digestive system.
If images lower down the body are required, such as the rectum, the patient may be given a barium enema. If blood vessel images are the target, a contrast agent will be injected into the veins.
The accuracy and speed of CT scans may be improved with the application of spiral CT, a relatively new technology. The beam takes a spiral path during the scanning, so it gathers continuous data with no gaps between images.
CT is a useful tool for assisting diagnosis in medicine, but it is a source of ionizing radiation, and it can potentially cause cancer.
Uses of CT scan
A CT scan has many uses, but it’s particularly well-suited to quickly examine people who may have internal injuries from car accidents or other types of traumas. A CT scan can be used to visualize nearly all parts of the body and is used to diagnose disease or injury as well as to plan medical, surgical or radiation treatment.
Computerized tomography (CT) scan It is useful for obtaining images of:
- Abdomen
- Blood vessels
- Bones
- Brain
- soft tissues
- Lungs
- The pelvis
CT is often the preferred way of diagnosing many cancers, such as liver, lung, and pancreatic cancers.
A scan of the head can provide important information about the brain, for instance, if there is any bleeding, swelling of the arteries, or a tumor.
It can help a doctor assess bone diseases, bone density, and the state of the patient’s spine.
It can also provide vital data about injuries to a patient’s hands, feet, and other skeletal structures. Even small bones are clearly visible, as well as their surrounding tissue.
Preparation for a CT scan
Depending on which part of your body is being scanned, the patient may be asked to do the following:
- Take off some or all of your clothing and wear a hospital gown
- Remove metal objects, such as a belt, jewelry, dentures and eyeglasses, which might interfere with image results
- Refrain from eating or drinking for a few hours before your scan
Contrast Material
Contrast material might be given to you:
- By mouth. If your esophagus or stomach is being scanned, you may need to swallow a liquid that contains contrast material. This drink may taste unpleasant.
- By injection. Contrast agents can be injected through a vein in your arm to help your gallbladder, urinary tract, liver or blood vessels stand out on the images. You may experience a feeling of warmth during the injection or a metallic taste in your mouth.
- By enema. A contrast material may be inserted in your rectum to help visualize your intestines. This procedure can make you feel bloated and uncomfortable.
Procedure of CT scan
The patient may need to abstain from food, and possibly drink, for a specific period before the scan.
How long the CT scan test take?
Typically, you should plan for an hour for a CT scan. Most of that time is for preparation. The scan itself takes between 10 and 30 minutes or less. Generally, you can resume your activities after a healthcare provider says it is safe to do so. Usually after they complete the scan and verify clear images.
On the day of the CT scan procedure
In most places, the patient will need to undress, usually down to their underwear, and put on a gown that the health center will provide. Avoid wearing jewelry.
If the hospital does not provide a gown, the patient should wear loose-fitting clothes free of metal buttons and zippers.
Some patients may have to drink a contrast dye, or the dye may be given as an enema, or injected. This improves the picture of some blood vessels or tissues.
Any patient who has an allergy to contrast material should tell the doctor beforehand. Some medications can reduce allergic reactions to contrast materials.
As metal interferes with the workings of the CT scanner, the patient will need to remove all jewelry and metal fastenings.
During the CT scan procedure
The patient will need to lie down on a motorized examination table that slides into a doughnut-shaped CT scanner machine.
In most cases, the patient will lie on their back, facing up. But, sometimes, they may need to lie face down or sideways.
After one x-ray picture, the couch will move slightly, and then the machine will take another image, and so on. The patient needs to lie very still for the best results.
During the scan, everybody except for the patient will leave the room. An intercom will enable two-way communication between the radiographer and the patient.
If the patient is a child, a parent or adult might be allowed to stand or sit nearby, but they will have to wear a lead apron to prevent radiation exposure.
After the CT scan procedure
After the exam the patient can return to their normal routine. If you were given contrast material, you may receive special instructions. In some cases, you may be asked to wait for a short time before leaving to ensure that you feel well after the exam.
After the scan, the patient is likely be told to drink lots of fluids to help their kidneys remove the contrast material from their body.
Results of CT scan
CT images are stored as electronic data files and are usually reviewed on a computer screen. A radiologist interprets these images and sends a report to your doctor.
How long does it take to get CT scan results?
The results of the scan usually take 24 hours. A radiologist, a physician who specializes in reading and interpreting CT scan and other radiologic images, will review your scan and prepare a report that explains them. In an emergency setting, such as a hospital or emergency room, healthcare providers often receive results within an hour.
Once a radiologist and your healthcare provider have reviewed the results, you will either have another appointment or receive a call. Your healthcare provider will discuss the results with you.
Risks of CT scan
A CT scan involves a small, targeted dose of radiation.
The amount of radiation involved is estimated to be around the same as a person would be exposed to in a space of between several months and several years of natural exposure in the environment.
A scan is only given if there is a clear medical reason to do so. The results can lead to treatment for conditions that could otherwise be serious. When the decision is taken to perform a scan, doctors will ensure that the benefits outweigh any risk.
Problems that could possibly arise from radiation exposure include cancer and thyroid issues.
This is extremely unlikely in adults, and also unlikely in children. However, are more susceptible to the effects of radiation. This does not mean that health issues will result, but any CT scans should be noted on the child’s medical record.
CT scan for pregnant individuals
Any woman who suspects she may be pregnant should tell her doctor beforehand, because there is a risk that the x-rays could harm the fetus.
Citing the American College of Radiography, the American Pregnancy Association (APA) point out that “No single diagnostic x-ray has a radiation dose significant enough to cause adverse effects in a developing embryo or fetus.”
However, the APA notes that CT scans are not recommended for pregnant women, “Unless the benefits clearly outweigh the risk.”
CT scans and breastfeeding
CT scan for Individuals who are claustrophobic
CT Scan versus MRI Scan
- A CT scan uses X-rays, but an MRI uses magnets and radio waves.
- Unlike an MRI, a CT scan does not show tendons and ligaments.
- MRI is better for examining the spinal cord.
- A CT scan is better suited to cancer, pneumonia, abnormal chest x-rays, bleeding in the brain, especially after an injury.
- Brain tumor is more clearly visible on MRI.
- A CT scan shows organ tear and organ injury more quickly, so it may be more suitable for trauma cases.
- Broken bones and vertebrae are more clearly visible on a CT scan.
- CT scans provide a better image of the lungs and organs in the chest cavity between the lungs.
Summary
CT scans are an excellent tool for diagnosing problems with soft tissues, blood vessels, and other body parts that can’t be seen with X-ray or ultrasound imaging.
These painless scans don’t require much preparation and can be done quickly in emergency situations. A CT scan takes less than an hour to do, but you may not get results right away depending on who is interpreting the results.
Your healthcare provider will let you know if a contrast dye is necessary for your scan and what action you need to take after the images are evaluated.
- Peripheral whole-blood
- Amniotic fluid
- Bronchoalveolar lavage fluid (BAL)
- Sputum
- Pleural effusion
- Cerebrospinal fluid (CSF)
- Serum (sera)
- Plasma
- Peripheral blood mononuclear cells (PBMC)
- Saliva
- Buffy coat
- Urine
- Stool samples
- Aqueous humor
- Vitreous humor
- Kidney stones (renal calculi)
- Other bodily fluids from most diseases including cancer.
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