Computed tomography, also known as Computerized Tomography or CT, uses special x-ray equipment to produce image data of the body from different angles. It uses a computer to process the information and show a cross-section of body organs and tissues.
CT imaging is useful because it shows different types of tissues, including soft tissue, lung, bone, and blood vessels. CT scans can produce clear and high-quality images of the internal structures of the body.
Using specialized equipment to create CT scans of the body, health professionals can easily diagnose various health conditions like heart disease, cancer, infectious disorders, trauma, and musculoskeletal problems.
The CT scanner is a square-shaped machine with a large hole in the centre. The procedure requires the patient to lie still on the exam table. Usually, the table can move up and down as well as slide into and out from the hole. In some cases, a contrast agent also referred to as contrast dye or contrast medium, can be administered before the procedure to emphasize on the CT scan image specific areas of the body under examination.
The machine has an x-ray tube on the gantry that moves around the body of the patient to produce each cross sectional image. Most often, the machine makes whirring and clicking noises as the table moves. Although health professionals can see and speak to the patient, he or she is alone in the room during the diagnostic process.
Health professionals instruct patients to wear loose-fitting and comfortable clothing for CT exams. Metal objects can severely affect the image. That’s why patients must not wear clothes with zippers and snaps.
A doctor may also ask the patient to remove eyeglasses, jewellery, hairpins, hearing aids, and removable dental work. However, it usually depends on the body part that will undergo the scanning procedure.
Similarly, a patient must no drink or eat anything one of two hours before the diagnostic test. Women, in particular, should inform the doctor about their pregnancy. CT scans are not suitable for pregnant women because ionizing radiation can significantly affect the developing fetus.
How does it work?
In many ways, CT scans work much like other conventional x ray exams. The procedure involves passing a small and controlled x ray beam through the body and different organs absorb it at different rates.
An image of the internal structure of the body is captured with the use of a special film that absorbs x-rays. With CT scans, the film is replaced by a wide array of detectors, which can accurately measure the x-ray profiles.
There is a rotating gantry inside the CT scanner, which has an x-ray tube on one side and a detector on the other side. The detector and x-ray tube make a 360 degrees rotation to pass the x-ray through the body of the patient.
The detector records about one thousand profiles or images with each rotation. Each image is reconstructed by a computer into a 2D image of the section scanned by the machine.
Typically, the imaging procedure involves the use of multiple computers to control the entire CT system. When the image pieces are reassembled by the computer, the result is a high-quality detailed, and multidimensional view of the internal structure of the body.
Spiral or Helical CT is a new method that has improved the accuracy of computer tomography for various health conditions. Spiral CT angiography is a new vascular technique. It is a non-invasive and affordable method than traditional angiography that allows health professionals to view blood vessels without needing invasive procedures.
When it comes to Spiral CT, the exam table advances through the scanner at a constant rate and the x-ray tube rotates around the patient. The purpose is to trace a spiral path through the patient and collect continuous data with no complications between images.
Spiral CT has refinements in detector technology that support high-quality and faster image acquisition with reduced exposure to radiation. Currently, the spiral CT cans are often called the Multi-detector CT.
The machine provides faster scanning and high-resolution images. Using a 16-slice CT scanner, a health professional can produce 32 image slices in one second. In simple words, a doctor can obtain a single spiral scan during a single breath-hold.
Thus, it allows the doctor to scan the abdomen or chest in less than 10 seconds. The high speed is beneficial for accurate diagnoses, especially in critically ill, pediatric, and elderly patients.
The multi-detector CT can successfully facilitate different applications like CT angiography. A radiologist cannot detect small lesions with conventional CT because the patient breathes differently on scans and the machine can miss detecting lesions due to unequal spacing between scans. In contrast, the rate of lesion detection is increased by the speed of spiral CT scanning.
Also known as CAT scanning, CT scans have an incredible history. In 1972, Godfrey Hounsfield, a British engineer at EMI laboratories, England Allan Cormack of Tuff University invented CT.
They made substantial efforts to develop a high-quality CT scanning machine. Both Cormack and Hounsfield received the Nobel Peace Prize for their efforts to advance the medical field.
The first CT scanners were installed by hospitals and clinics between 1974 and 1976. It is important to know that the original system was designed to produce images of the head. However, within a few years, scientists developed CT scanners that could scan the entire body. By 1980, CT scanners became available all over the world.
Today, there are more than 6,000 CT scanners in the United States and 30,000 machines installed in different countries of the world. Anyway, Hounsfield developed the first CT scanner in his laboratory at EMI.
The machine would take a few hours to acquire data for a single slice or image. It would take several days to reconstruct an image from the acquired data. Currently, we have advanced and fast-speed CT scanning machines that can collect 4 slices of data in less than 350ms and reconstruct images from the acquired data within a second.
For instance, modern machines can scan the entire chest or abdomen in less than 5 seconds. For the last couple of decades, scientists have made significant efforts to improve the speed, efficiency, and reliability of the system. Today’s advanced systems can produce high-resolution images within a few seconds.
The fast-speed CT scanning machines allow for producing more anatomical images in less time. Faster scanning helps doctors to facilitate patients and eliminate artifacts from patient motion.
Today, doctors can perform fast CT exams in a more patient-friendly manner. Scientists are working to further advance the CT scanning systems to produce high-resolution images. The purpose is to reduce the amount of x-ray radiation and streamline the process of diagnosis.
Main Use Cases
Because a CT scanner provides detailed and high-resolution cross-sectional views of different tissues, it is the best tool for health professionals to study the chest and abdomen. Research studies have highlighted that CT is an effective diagnostic imaging tool for liver, pancreatic, and lung cancer.
The image produced by the machine allows a doctor to confirm the presence of lesions and tumours. The machine produces high-quality images that enable a professional to measure the size, identify the location, and determine the interaction of the tumour with nearby tissues.
Doctors use CT examination to plan and administer radiation therapy for tumours. It is also useful for guiding biopsies and minimally invasive surgical procedures. Research shows that CT scans are useful in planning surgery and predicting surgical respectability.
Moreover, it can clearly show very small bones and tissues, including muscles and blood vessels. Thus, it makes the device invaluable for health professionals to diagnose and treat spinal problems, injuries to the arm, hands, and feet. Also, it can produce images of skeletal structures.
Health professionals use CT images to measure the mineral density of bones to detect osteoporosis. When it comes to cases of trauma, CT scans can identify injuries to internal organs, such as kidneys, liver, and spleen.
Many shock-trauma centres and clinics have installed CT scanners in the emergency room. CT also plays a key role in the detection, diagnosis, analysis, and treatment of vascular diseases. Thus, it helps a doctor to make a treatment plan for stroke and kidney failure.
Differences compared to X-Ray
Health professionals use standard X ray to detect abnormalities in hard tissues, such as fractures and dislocations of bones. X-rays are also helpful in detecting other diseases like pneumonia and cancer.
In contrast, CT is an advanced machine or technology used to diagnose problems in soft tissues. CT uses both x-ray images of the internal structures of the body and a computer to produce high-resolution pictures.
Besides, x-ray machines cannot diagnose soft tissues, muscle damage, and other internal organs of the body. X-ray machines produce 3D images of the body whereas CT scanning machines produce 3D images of the internal structures of the body.
Generally, doctors use CT scans to produce clearer and high-quality images of body structures. The purpose is to diagnose abnormalities, such as fractures, illness, inflammation, pain, and other diseases.
There are different types of machines used to diagnose health conditions. However, the most common ones are x-ray and CT scanning machines. Radiologists and doctors usually supervise the process of diagnosis.
Keep in mind that Wilhelm Rontgen developed the first X-ray machine in 1895, whereas Allan Cormack and Godfrey Hounsfield invented the CT scan machine in 1972. X-ray machines use radio waves to generate images of the body.
The waves go through the body and bounce back to the machine to generate 2D images. CT, on the other hand, is an advanced type of X-ray machine that produces 3D images of the scanned body. It produces multiple x-ray images that can be viewed on a computer.
|Side by Side Comparison of CT scans and X-rays|
|The CT scan machine was invented in 1972.||The X-ray machine was invented in 1895.|
|CT scan is an advanced x-ray machine or process that provides more detailed images of the internal structures of the body. It can produce high-resolution images of soft tissues that can’t be generated with an x-ray machine.||It uses radio or light waves as radiation for scanning the internal structures of the body. The machine detects internal abnormalities, such as fractures, bone dislocations, pneumonia, tumours, and lung infections.|
|The machine generates three-dimensional images using a computer.||The machine produces two-dimensional images.|
|It is an expensive machine because it used 360-degree x-ray beams to produce powerful images.||It is an affordable and easily accessible machine. The machine may not produce accurate images of internal injuries.|
|CT uses a small number of x-ray beams to produce high-resolution images. The intensity of radiation is not high. It is not easily available in small hospitals and clinics.||The procedure requires more precautions because radiations can cause harm. It is widely available in almost all hospitals and clinics.|
How are they stored?
Research shows that CT images are stored on a hard drive, CD, DVD, or any other storage media. The storage of CT images, in general, is known as archiving. CT images are stored and saved on a hard drive so that a doctor can reuse them at a later date.
A health professional can print the images onto the film. A doctor can also save the images onto a CD-ROM and DVD-ROM. Because raw data files are large and occupy a lot of space on the disk, a health professional may store them for a limited time.
CT scan machines use a specialized computer that has a powerful hard disk to store a significant amount of raw data that can be transformed into images. It is essential to know that a doctor can save the images electronically because of their small size. Likewise, images can be stores on external hard drives and magnetic optical disks.
Why is a CT scan black and white?
The primary reason behind this is that CT scan machines use x-ray beams. An image produced by the CT scan machine shows that the bones are white and the air is black. Although the images are similar to x-rays, they are more detailed and high resolution. Besides, a CT exam used for soft tissues produce gray shades on the scan.
Besides, the x-ray machine applies radiation in a circular motion with image detectors on the opposite side of the patient’s body. The machine reconstructs the tissue slices and displays them on a grayscale matrix.
Tissues like water and air have lower attenuation levels, which means the machine will display them as dark, whereas bones have high attenuation levels and the machine display them as bright.
Moreover, CT scans create images of the internal structures of the body in different shades of black and white. The reason is that different tissues absorb different levels of radiation. For instance, bones contain calcium content that absorbs higher levels of radiation. That’s why the bones appear white on the CT.
Radiation in a CT scan
Unlike MRI, CT scans use x-ray radiations known as ionizing radiations that can cause damage to the internal structures of the body. Research shows that ionizing radiation used in CT can even damage cells and DNA. It can also damage the normal cell and turn it cancerous.
CT scans expose patients to more x-ray radiations than other medical imaging tools. For instance, there are 100-200 x-rays in a single CT scan for the chest. Although it seems a small amount of radiation, it can significantly damage the internal structures.
Remember, people are usually exposed to natural ionizing radiation produced by radioactive materials in the atmosphere. Every year, an average person has a radiation exposure from the surrounding environment of 3 mSv .
Likewise, each CT scan exam passes 1-10 mSv of radiation into the patient’s body. The amount of radiation depends on scanning the particular internal structure of the body and the health condition of the patient.
A minimum dose of CT scan performed for the chest is around 1.5 mSv. However, the regular dose for the same exam is 7 mSv. It means when a patient undergoes more CT scans, he or she receives more radiation. High exposure can cause damage to the body and disturb the internal mechanism at intracellular, cellular, and tissue levels.
A low dose of ionizing radiation has lower risks of developing cancer. According to the American College of Radiology, a doctor must not perform a CT scan until it is necessary or if there are any health benefits from it.
Unlike other medical imaging techniques, CT scanning offers high-resolution images of different types of tissues, such as soft tissues, blood vessels, bones, and lungs. CT scanning is a non-invasive and painless procure that produce more accurate images of the internal body structures.
Likewise, the procedure is simple and fast as well as diagnoses made with CT can eliminate the need for surgery and surgical biopsies. A CT scan machine is an effective tool to identify both normal and abnormal internal structures.
It a useful tool or device for health professionals to guide radiotherapy, minimally invasive surgery, and needle biopsies. CT is a cost-effective imaging tool for a variety of clinical problems.
Moreover, CT does involve exposure to x-ray radiation, but if done correctly, the risks are reduced. The effective radiation dose from a CT scan procedure is about 7 to 10 mSv. However, it can still cause problems for the patient.