CT Scanners: Scans Types, Techniques & More

The act of developing an image of an object section-by-section with the use of penetrative waves is called tomography.

By stitching together thousands of small 2D image “slices”, scientists are able to reconstruct a 3D rendering of an image. The image's final assembly is usually done using very complex mathematical procedures like tomographic reconstruction and other reconstruction algorithms. These algorithms can be organized into two categories; filtered back projection and iterative reconstruction.

There are many different types of tomographic devices and most vary based upon what they are imaging, how it is imaged, and what type of penetrative waves they are using. Computed axial tomography scans, more commonly known as CAT or CT scans, are devices that allow for cross-sectional imaging of materials without the need to cut them open.

CT scans are most often used in the medical field, to generate a 3D rendering of a person’s internal anatomy. These images can then be used to help better diagnose patients or inform doctors about what types of therapeutic measures they need to take.

It is able to achieve this by having the patient take a contrast agent before using a series of narrow X-ray beams which are rotated around them, creating the cross-sectional image slices.

Though similar to conventional X-ray machines, CT scans are able to create more detailed images by differentiating between tissue, bone, and soft tissue while detecting many abnormalities and medical conditions. A CT exam can even be used by a radiologist to perform guided biopsies, significantly decreasing the time it takes and improving its accuracy.

In addition, industrial CT scanners are available and although they generate similar results to medical CT scanners, they are fundamentally different. For this reason, they are not as prevalent to the needs of medical laboratories and environments.

Instead, they are widely used in industry settings for internal inspection of components, including flaw detection, failure analysis, assembly analysis, reverse engineering applications, and metrology in general.

CAT Scan Types & Techniques

The main components that make up a medical CT scanner are a bench that the patient can lay down on, a gantry, a data acquisition system, and an operating console.

The gantry refers to the cylinder that the patient is placed into and houses all the equipment to produce and detect the X-rays.

Beyond these components, CT scanners use a variety of techniques and slice counts to produce images.

Multislice CT (MSCT)

Also known as multi-detector computerized tomography, is a type of CT scanner has multiple detectors. This allows for higher numbers of sections or multiple tomographic slices, which results in higher-resolution diagnostic imaging than conventional CT scans.

Combining multiple detectors at different angles with the use of helical scanning technology has also resulted in significant improvements in imaging range and time of examination.

Electron Beam Tomography (EBT)

Getting detailed images of the heart at specific points in its movement cycle can tell us a lot about the health of that heart. Traditional CT images have difficulty producing precise photos of a heart due to its constant motion.

EBT was originally developed to overcome these issues and produce detailed images of a live heart. It still uses X-ray tubes; however, they are stationary, and instead, an electron-beam focal point traces a large circular arc around the patient. EBT allows radiologists to assist cardiologists in the diagnosis and treatment of heart disease.

CT Myelography

Myelography is a radiographic technique that uses fluoroscopy and contrast material to observe patients’ spinal cords, nerve roots, and spinal linings. When paired with CT scans, CT myelograms can provide very detailed information about nerve and back anatomy.

A radiographic IV contrast dye is administered to the patient in a sac around a nerve root and a CT scan is then performed. These contrast media allow CT technologists and radiologists to more effectively distinguish normal from abnormal conditions.

These contrast materials can be taken orally, be administered through the rectum via an enema, or injected via a blood vessel. All forms of contrast media are safe, and rarely cause any adverse side effects or allergic reactions in patients.

CT Angiography (CTA)

Also known as arteriography, angiography is a medical imaging technique used to observe the inside of blood vessels, arteries, veins, and heart chambers. CT angiograms inject contrasting materials into the area of interest and CT imaging is used in conjunction with an angiogram to produce even more detailed images.

The use of X-ray images and contrast agents, such as barium sulfate, produces high contrast images while being much less invasive than conventional angiograms.

Development of the CT Scan

Though the first computed tomography scanner would not be invented until the late 1960s, the mathematical principle dates back to 1917.

Austrian mathematician Johann Radon, born in the late 1880s, would introduce his function, the Radon transform, in 1917. In conjunction with his Radon transform formula, he would also pen an inverse formula that is still used today for medical CT scans.

Forty years later UCLA neurologist William Oldendorf theorized that one could use a medical sensor to scan the heads of patients using X-rays.

In 1961, he created the prototype which employed an X-ray source and X-ray detectors that rotated around the object that he wanted to be imaged. The resulting paper in which Oldendorf would detail both his theory and his prototype would later be pivotal in Allan Cormack’s development of the math behind modern computed tomography.

It would be Sir Godfrey Hounsfield of the United Kingdom who would develop the first commercial CT scanner. He would conceive of the idea in 1967 at EMI Center Research Laboratories but it wouldn’t be until 1971 that the first patient would be scanned.

From 3D Reconstruction to Advanced Imaging Insights

Tomography is a powerful technique that allows us to develop detailed images of objects section-by-section using penetrative waves.

By combining multiple 2D image slices, scientists can reconstruct a comprehensive 3D representation of the object, employing intricate mathematical procedures like tomographic reconstruction and various reconstruction algorithms.

There are diverse types of tomographic devices, each tailored to specific imaging requirements and utilizing different penetrative wave technologies. One prominent example is computed axial tomography (CAT or CT scans), extensively used in the medical field for non-invasive cross-sectional imaging of internal anatomy.

CT scans play a crucial role in diagnosis, aiding healthcare professionals in making accurate assessments and determining appropriate therapeutic interventions. By employing contrast agents and rotating narrow X-ray beams around the patient, CT scans produce highly detailed images that differentiate between tissues, bones, and soft tissues, enabling the detection of abnormalities and medical conditions.

Furthermore, CT exams have facilitated guided biopsies, enhancing precision and reducing procedure time.

With its ability to reconstruct 3D images from sequential sections, tomography has revolutionized imaging techniques in medical and industrial domains. As technology advances, we can anticipate further refinements in tomographic devices, enhancing image quality, resolution, and diagnostic capabilities.

The impact of tomography on our understanding of the world, whether in healthcare or industry settings, is undeniable, opening new avenues for research, development, and improved decision-making.

In conclusion, tomography serves as a cornerstone in visualizing the internal structures of objects, providing valuable information for medical diagnoses and industrial inspections. The journey of tomographic imaging continues to unfold, moving us toward a future where we can gain even deeper insights into the intricate details of our health.