Computed Tomography

A CT scan uses X-rays to make detailed pictures of structures inside of the body.  During the test, you will lie on a table that is attached to the CT scanner, and it will send x-rays through the body area being studied.  Each rotation of the scanner provides a picture of a thin slice of the organ or larger area.

In some cases, a dye called contrast material may be used.  The contrast may be administered via an IV or an oral contrast, and makes it easier to see structures or organs more clearly on the CT images.

A CT scan (or computed tomography scan) is a type of imaging method that utilizes X-rays (also known as a radiograph) to pass through the body to create a three-dimensional impression of various cross-sections of the body using two-dimensional radiographic images. A CT scan may also be referred to as a CAT scan (Computerized Axial Tomography), and is the most common form of CT used in medicine or other related contexts since its introduction in the 1970’s.

There are various types of scans available, covering various sections of the body: Abdominal, Cranial, Lumbosacral Spine, Orbit, and Thoracic. These scans focus on body parts (arms, chest, legs, pelvis, and stomach), or internal organs (adrenal glands, bladder, heart, intestines, kidneys, liver, lungs, and pancreas). In addition, it can also be used to study blood vessels (which are harder to detect due to their small size and ease of “blending” in with their immediate surroundings), bones, the spinal cord, and other joints and extremities. The procedure’s main function is used to diagnose and inspect various infirmities in the body such as disease, infection, masses, and tumors (such as colon cancer or heart disease) without having to cut into the patient’s body. It also helps medical professionals during biopsy procedures, and is used as a guide for interventional diagnoses.

During the test, the patient will be asked to lie on a small table that will slide into the CT scanner. Patients have to remain still during the exam (movement causes blurred images or artifacts). As such, the patient may be requested to hold their breath for brief periods of time. Once inside the scanner and the procedure has begun, X-rays will rotate and perform the scan, providing separate images (or “snapshots”) of the body, called “slices”. These scans are recorded on film or digitally, highlighting thin slices of the organ or surrounding the larger area. These images are then reconstructed by stacking these slices one on top of the other, allowing them to be used in a varied selection of diagnostic and therapeutic purposes.

Scans are usually completed in just a seconds to minutes as technologies have continued to advance. The raw data that is obtained from the scan is called a sinogram, though it is not yet ready to interpret the found information. The scan data is then processed via tomographic reconstruction, that creates a series of cross-sectional images. The types of 3D renderings are: surface rendering, volume rendering, and image segmentation, each providing a generally accurate recreation of the scanned area.

During the exams, a special dye is required that is called contrast material. Contrast material is used to help certain organs and structures show up more clearly during X-rays, and helps to obtain functional information relating to tissues. The dye can be administered through several ways: via IV in your hand or forearms, orally, or in drinkable form (which is easily passed later). If contrast is required, patients may be requested to abstain from eating or drinking for the 4-6 hours before test time.

If the patient has iodine related allergies, then they should let their doctor know, as related allergies, can cause, itching, sneezing, nausea, vomiting, and hives. However, antihistamines or steroids can be used to reduce the effects. Also, if there are any medical issues such as kidney disease or diabetes, extra fluids can be used to flush the iodine out of the patient’s system.

The usage of computed technology scans have increased substantially over the last two decades. As recently as 2007, an estimated 72 million scans were utilized on patients just within the United States. On average, six to eleven percent of these computed tomography scans were performed on children, which is an increase of seven to eight percent from 1980. The same level of increase has been noted in European and Asian countries as well. Advances in technology have also been a key factor for faster scan times and more accurate results. Modern CT systems use spiral (also known as helical) scanning, in addition to the more conventional “axial” mode, and newer advances are also capable of creating multiple slices simultaneously.

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