Computed Tomography Flashcards

For an adult, the usual range of respiration is

Answer: 12-20 breaths per minute

A CT scout image, also known as a topogram or pilot scan, is a preliminary low-dose X-ray image taken before the main CT scan. While primarily used to plan the scan range and ensure proper patient positioning, it can also be utilized for specific measurements, including bone density in certain clinical contexts. It helps the technologist define the exact area to be scanned and optimize parameters.

A patient having a history of an allergic reaction to iodinated contrast media may undergo the following procedures in advance of a contrast-enhanced CT scan:

Answer: Premedication with steroids and antihistamines

For an adult, the normal range of respiration is typically 12-20 breaths per minute. This rate can vary slightly based on activity level, age, and individual health status. Monitoring respiration rate is a standard vital sign assessment, providing insight into a patient's respiratory function and overall physiological state.

Which of the following signs may a patient in shock display?

Answer: All of the above

Shock is a critical condition characterized by inadequate tissue perfusion, leading to a systemic response. Tachycardia (rapid heart rate) is a compensatory mechanism to maintain cardiac output, while rapid, shallow breathing attempts to increase oxygen intake. Cyanosis (bluish discoloration of the skin) indicates poor oxygenation due to insufficient blood flow. Therefore, all these signs are commonly displayed by a patient in shock.

Which of the following signs may a patient in shock display? Which infection control measures are necessary at the site of an intravenous injection of iodinated contrast media?

Answer: Surgical asepsis

An intravenous injection involves penetrating the skin barrier and directly accessing the bloodstream. To prevent the introduction of microorganisms and subsequent infection, a sterile technique is absolutely essential. Surgical asepsis, also known as sterile technique, aims to eliminate all microorganisms from an area and is the appropriate measure for any procedure that invades sterile body tissues or the circulatory system.

Iodinated contrast material is frequently injected intravenously at the following sites:

Answer: All of the above

The antecubital, cephalic, and basilic veins are all commonly used and accessible sites for intravenous injections, including the administration of iodinated contrast material. The antecubital vein, located in the bend of the elbow, is often preferred due to its size and superficial location. The cephalic and basilic veins, running along the forearm, also provide suitable and frequently utilized access points for venipuncture.

Which of the following technical aspects directly affects the dose given to patients?

Answer: Milliampere-second {MAS}

Milliampere-second (mAs) directly controls the quantity of X-ray photons produced during a CT scan. A higher mAs setting means more X-rays are generated and delivered to the patient, resulting in a proportionally higher radiation dose. Therefore, adjusting the mAs is a primary method for controlling and optimizing the radiation dose given to patients in CT imaging.

The patient should be questioned about the following matters before receiving an intravenous injection of iodinated contrast material: 1. Renal Function- One kidney dose is cut 2. Allergic History- Premedicated 3. Cardiac History- Heart disease

Answer: 1,2, and 3

Before administering iodinated contrast material, it is crucial to assess the patient's renal function, as the kidneys excrete the contrast, and impairment can lead to contrast-induced nephropathy. An allergic history is vital to identify potential hypersensitivity reactions to iodine, which can range from mild to severe. Cardiac history is also important because contrast media can affect heart function, especially in patients with pre-existing cardiac conditions, increasing the risk of adverse events.

Who is credited with the invention of Computed Tomography (CT)?

Answer: Godfrey Hounsfield

Sir Godfrey Hounsfield, an English electrical engineer, is widely recognized for his groundbreaking work in developing the first commercially viable Computed Tomography (CT) scanner. His invention in the early 1970s revolutionized medical diagnostics by providing detailed cross-sectional images of the body. For this achievement, he was awarded the Nobel Prize in Physiology or Medicine in 1979.

What is the typical unit of measurement used for the density of tissues in CT scans?

Answer: Hounsfield Unit (HU)

The Hounsfield Unit (HU) is the standard quantitative scale used in CT imaging to measure and display the radiodensity of tissues. This scale is normalized, with water assigned a value of 0 HU and air approximately -1000 HU. Different tissues, such as bone, fat, and various organs, have characteristic HU values, allowing for their differentiation and analysis on CT images.

What does the term "slice increment" refer to in CT imaging?

Answer: The interval between slices

Slice increment, also known as slice interval, refers to the distance between the center of one CT slice and the center of the next adjacent slice. It determines the degree of overlap or gap between consecutive images acquired during a scan. Adjusting the slice increment impacts the spatial resolution and the total volume of tissue covered in the scan.

Which part of a CT scanner rotates around the patient during the scan?

Answer: Gantry

The gantry is the large, donut-shaped component of a CT scanner that houses the X-ray tube and the detector array. During a CT scan, the X-ray tube and detectors rotate rapidly within the gantry around the patient. This continuous rotation allows for the acquisition of X-ray projections from multiple angles, which are then used to reconstruct detailed cross-sectional images.

What is the purpose of "windowing" in CT image display?

Answer: To adjust image brightness and contrast

Windowing is a crucial post-processing technique in CT image display that allows for the adjustment of image brightness (window level) and contrast (window width). By manipulating these parameters, specific tissue types or pathologies can be optimally visualized. This enables radiologists to highlight structures with similar densities, improving diagnostic accuracy for various anatomical regions like bone, soft tissue, or lung.

Which type of contrast agent is commonly used in CT scans to enhance blood vessels and soft tissues?

Answer: Iodine-based

Iodine-based contrast agents are the most commonly used type in CT scans to enhance blood vessels and soft tissues. Iodine has a high atomic number, which allows it to effectively absorb X-rays, making structures where it accumulates (like blood vessels or highly vascularized lesions) appear brighter on the CT images. This enhancement is vital for detecting and characterizing various pathologies.

Which type of CT imaging provides real-time assessment of tissue perfusion and blood flow?

Answer: Perfusion CT

Perfusion CT is a specialized imaging technique that provides a real-time assessment of blood flow, blood volume, and mean transit time within tissues. It involves rapid, sequential scanning after a bolus injection of contrast media, allowing for dynamic evaluation of how contrast enters and exits a region. This method is particularly valuable in conditions like stroke to identify areas of ischemic penumbra or to assess tumor vascularity.

Which type of CT scan is specifically designed for imaging the coronary arteries and heart structures?

Answer: Cardiac CT

Cardiac CT, often performed as Coronary CT Angiography (CCTA), is specifically designed for detailed imaging of the coronary arteries and heart structures. This technique uses rapid image acquisition and often involves synchronization with the patient's electrocardiogram (ECG) to minimize motion artifacts from the beating heart. It is crucial for detecting coronary artery disease, assessing stent patency, and evaluating cardiac anatomy.

What is the primary advantage of helical (spiral) CT scans over conventional CT scans?

Answer: Reduced radiation dose

Helical (spiral) CT scans offer several advantages over conventional CT, including faster image acquisition and reduced motion artifacts. A significant benefit is the potential for reduced radiation dose. By continuously rotating the X-ray tube and moving the patient through the gantry, helical CT acquires a volume of data in a single breath-hold, minimizing the need for repeated scans or overlapping exposures, leading to more efficient radiation use.