Difference Between CT scan and Ultrasound

CT scan vs Ultrasound

There are numerous diagnostic tools used by radiology departments to diagnose illnesses. Each tool has specific purposes; such as X-rays for broken bones or MRIs for soft tissue diagnoses. Radiologists can effectively use them for a more accurate diagnosis, or a better look at the specific area of concern. This article focuses specifically on the differences between CT/CAT (Computed Axial Tomography) scans and Ultrasound scans.

Purpose

CT scans are diagnostic tools that are used for many purposes. Basically, CT’s send X-rays through the body in tiny slices, which are saved as images on the computer. There is a special type of CT scan, called a Fluoroscopy, which can capture live motion for certain diagnostic studies, or help the interventional radiologist, who is performing a biopsy, by showing him where to guide the needle into an internal organ.

Ultrasound images have multiple purposes that allow the radiologist to make a more precise diagnoses. Ultrasound uses high-frequency sound waves to produce a greyscale picture of various organs, such as abdominal organs or the heart, and is frequently used for fetal examinations. Everyone has seen a fetal ultrasound with a baby clearly shown in the image. Doppler ultrasound allows the technology to capture blood flow rates, such as carotid and renal arteries.

Functionality

The CT is a doughnut-shaped modality that sends an X-ray through the body, each time the scanner rotates, and an x-ray image is taken. Sometimes, the patient is injected with a dye in a contrasting color, which makes the internal organs, tumors, blood flow, or other regions of interest clearly stand out, allowing the radiologist to make a more accurate diagnosis. The images are displayed on a monitor for the Radiologist’s viewing.

The ultrasound’s transducer emits sound waves into the patient’s body. These waves bounce off the organs and tissues inside the body, and return to the transducer. The transducer interprets these sounds, and produces an image that is displayed on the monitor. Measurements can be made for size and depth, blood flow, or constriction of flow, and saved by the Technologist for the Radiologist’s viewing.

History

The CT modality was invented by an engineer and a physicist in 1972; Godfrey Hounsfield and Allan Cormack. Originally, it had a small opening, and was initially used for images of the head. As technology improved, and the ‘hole’ grew larger, it allowed the entire body of a patient to be scanned. Originally, it took several hours to acquire the data and reconstruct it into an image; today it only takes a few moments.

Ultrasound is familiar because it is used in movies and television programs, however, few people know when ultrasound was invented. There are many controversies, but the earliest was first reported at the Naval Medical Research Institute in the late 1940’s, when Dr. George Ludwig proved that gallstones could be detected, and later in 1957 when Dr. Ian Donald first used it for fetal images.

Summary:

1. CT’s send X-rays through the body in tiny slices, which are saved as images on the computer, whereas, ultrasound images have multiple purposes that allow the radiologist to make a more precise diagnoses.

2. The ultrasound’s transducer emits sound waves into the patient’s body, but in a CT scan, sometimes the patient is injected with a dye in a contrasting color, so that it can easily be traced.

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