Role of Multidetector Computed Tomography

Introduction:

The development of a new multidetector computed tomography (MDCT) greatly impacted the imaging of various systems, especially the cardiovascular system. It generates thin sections of computed tomography images with excellent resolution. The main advantages of MDCT over conventional CT are high imaging acquisition speed, more area coverage of the patient, and high spatial resolution.

What Is Computed Tomography?

A computed tomography (CT) scan is a medical imaging test used to obtain detailed internal images of the body. It is a non-invasive test that uses X-rays to take pictures of the internal organs of the body. Modern CT scanners, such as MDCT take images faster and is more detailed. By this, images of soft and hard tissues can be clearly viewed and analyzed, such as images of a beating heart or detection of any anomalies like a blockage in the arteries of the heart.

What Is the History of Computed Tomography?

The computed tomography technology was first invented by Sir Godfrey N. Hounsfield in 1971. In the year 1975, CT technology went through a great evolution process from a time-consuming first-generation configuration to fourth-generation scanners, which provided a much faster speed of taking and processing images as compared to the older scanners. Later on, various modifications of computed scanners came such as helical CT scanners based on

innovative slip ring technology, and dual-slice helical CT scanners were introduced in 1992 with multi-detector rows. In 1998, four-slice multidetector-row computed tomography (MDCT) scanners were introduced, and in the years 2000 to 2002, the 8- and 16-slice MDCT scanners were introduced, which have a much faster rate of scanning and coverage area.

What Is the Difference Between Computed Tomography and Multidetector Computed Tomography?

Generally, there are two main differences between conventional spiral CT and multidetector computed tomography (MDCT).

• First, the multidetector computed tomography has a high acquisition speed of 0.37 second rotation speed as compared to computed tomography with a speed of one second.

• Secondly, MDCT collects volume data instead of individual slice data.

These two factors help in providing isotropic data that can be arranged in different planes without compromising the quality or resolution of the images. Therefore, MDCT generates thin-section CT images with superior resolution, using around 260 to 320 detector rows, and the entire chest can be scanned within two to three seconds.

What Are the Principles of Multidetector Computed Tomography?

The principles of multidetector computed tomography include -

1. Achieving good quality with enhanced contrast images of the arteries.

2. Providing sufficient coverage of the arterial system.

3. Getting the image of the arterial tree by using a contrast medium.

4. Handling and storage of a huge amount of acquired data using various post-processing techniques.

What Is the Need for MDCT?

A person may need to go for multidetector computed tomography when other tests like chest X-rays, electrocardiograms (ECG), echocardiograms (echo), or stress tests do not give the required information regarding heart health. Therefore, the healthcare professional may advise MDCT to collect more data on the following -

• The structure and functioning of the heart, how well it is pumping blood.

• To detect the scarring of heart muscle caused by a heart attack.

• To direct the fluid in the pericardial sac covering the surface of the heart.

• To check for narrowing of coronary arteries or the building up of plaque in them.

• Detecting any abnormalities in the large vessels leaving the heart.

• The risk of heart attack.

What Are the Clinical Applications of MDCT?

The clinical application of MDCT includes imaging of the aorta (largest artery carrying blood from the heart) and iliac system (blood vessels that provide blood to the legs, pelvis, reproductive organs, and other organs in the pelvic area), which include the following blood vessels -

1. Thoracoabdominal Aorta -

• Diagnosis of congenital and degenerative aortic diseases.

• Evaluation of visceral arteries such as celiac, superior mesenteric, and renal arteries.

• Tumor staging and surgical planning.

2. Renal Arteries -

• Diagnosis of renal artery stenosis (narrowing of one or more arteries that carry blood to the kidneys) in hypertensive patients.

• Assessment of anatomy in case of kidney transplants.

• Assessment of renal arteries for renal artery stenting (a procedure to open the narrow renal arteries).

3. Peripheral Arterial System -

• Assessment of peripheral vascular diseases.

• Assessment of bypass grafts.

4. Carotid or Intracranial Circulation -

• Assessment of aortic arch vessels.

• Checking internal carotid artery stenosis.

• Characterization of atherosclerosis (a condition in which there is fat buildup, cholesterol, and other substances in and on the artery walls).

• Preoperative planning for various surgical treatments for intracranial aneurysms and vascular malformations.

5. Cardiac Imaging -

• Atypical chest pain.

• Young patients with high risk for coronary disease.

• Patients with intermediate risk.

• Coronary artery anomalies.

• Assessment of myocardial scars, aneurysms, and tumors.

• Assessment of coronary artery bypass grafts.

How Is MDCT Performed?

The test is usually done in hospitals or special outpatient clinics and the procedure is as follows:

• The scan is usually done in a supine position with the arm raised above the shoulders.

• The electrodes are then attached to the chest for monitoring.

• Multi-detector chest CT scans are performed to create clear images of the heart.

• The radiation exposure settings are based on the weight of the patient and in the case of children, the exposure is set to be very minimal.

• When the patient is ready, the table on which the patient is lying is moved inside the machine and the scanner moves around in a circular motion without touching the patient.

• In case contrast dye is used it is injected through an intravenous line (IV) in an arm vein and the patient is instructed to not eat for four to six hours before the test.

• The images collected are used to generate a three-dimensional structure of the computer screen which helps in detecting complex anatomy of aortic diseases and tracheobronchial pathology.

• The scan usually takes around five to ten minutes.

What Are the Risks Related to Multidetector Computed Tomography?

• The exposure to radiation in multidetector computed tomography is higher as compared to conventional tomography. Therefore the patient should consult with the doctor before going for the scan.

• In case of pregnancy, the doctor should be informed and the scan can be delayed.

• In case of kidney problems, contrast dye should not be used as it may worsen kidney functions.

• Some people may be allergic to the contrast medium which should be checked before performing the procedure.

Conclusion:

In conclusion, MDCT scanners offer great advantages as compared to their predecessors. It helps in getting results much faster with wide area coverage and high-quality images. This is a non-invasive diagnostic tool that can be used for a wide range of cardiovascular pathologies. However, the risk of radiation with this tool is higher than with conventional computed tomography. Therefore the patients should always consult with the doctor before going for this test.