MCQ Tomography Equipment

The third generation of CT scanners introduced a significant reduction in the time required for the scanning process, as well as a substantial decrease in the amount of scattered radiation generated during the scan. This was achieved through advancements in technology and design.

In Computed Tomography (CT), the process of filtered back projection is a crucial step in reconstructing the image from the collected x-ray data. It involves mathematically manipulating the acquired projections to create a cross-sectional image of the scanned area.

A single transverse slice in helical CT refers to a reconstructed image representing a plane that cuts through the body perpendicular to the direction of the scan. This 'slice' provides a cross-sectional view of the area being scanned.

The pitch in helical CT is defined as the ratio of the table movement during one 360-degree rotation of the x-ray tube to the thickness of the reconstructed slices. It essentially determines how much of the body is scanned per rotation.

A low-pitch technique in helical CT might be beneficial for detecting subtle lesions or evaluating intricate anatomical structures. This is because a lower pitch leads to increased overlap of data, resulting in higher image quality and clarity.

The Dose-Length Product (DLP) is a parameter that best reflects the total radiation dose delivered to a patient during a CT scan. It takes into account the dose received in each slice and the total length of the scanned area.

Effective dose is a measure designed to quantify the stochastic (cancer) risk from ionizing radiation. It takes into account the type and energy of the radiation, as well as the sensitivity of different organs and tissues to radiation.

The size-specific dose estimate (SSDE) is a dose parameter that factors in the patient's size when calculating the radiation dose during a CT scan. It adjusts the dose based on the individual's body characteristics.

Positioning a patient off-center within the CT gantry can potentially result in reconstruction artifacts. These artifacts can interfere with the accuracy of the reconstructed image, making it difficult to interpret.

The major determinant of temporal resolution in CT is the gantry rotation speed. A faster rotation speed allows for a shorter scan time, leading to improved temporal resolution and the ability to capture rapidly moving structures, such as the beating heart.

A prospectively gated cardiac CT technique aims to minimize the motion artifacts caused by the beating heart. This involves syncing the scan with the patient's heartbeat, allowing for a more precise and accurate reconstruction of the cardiac structures.

High radiation doses in retrospectively gated cardiac CT compared to prospectively gated CT arise from the need for multiple scans over a longer period. This is necessary to collect data from different phases of the cardiac cycle, potentially exposing the patient to a higher cumulative dose.

The most important physical process responsible for tissue contrast in CT imaging is photoelectric absorption. This occurs when an x-ray photon is absorbed by an atom, causing the ejection of an electron and resulting in a difference in x-ray attenuation, which creates variations in the imaging signal.

The CT number (Hounsfield unit) of fat is not constant but slightly varies depending on factors such as the x-ray beam energy (kV) and the composition of the fat itself. However, these variations are generally small and can be considered negligible for practical purposes.

Beam hardening in x-ray imaging refers to the phenomenon where the average energy of an x-ray beam increases as it passes through a dense material. This occurs because lower energy photons are preferentially absorbed, leaving behind a higher energy spectrum.

A hardened beam in CT can affect the appearance of soft tissues in the image, making them appear darker with poorer contrast. This is because higher energy photons are less likely to be absorbed by soft tissues, resulting in less contrast.

Dual-energy CT offers numerous advantages, including the ability to create virtual non-contrast images, separate various materials, and generate perfusion maps. However, it doesn't guarantee a decrease in radiation dose compared to conventional CT.

Computed Tomography (CT) provides diagnostic images with improved spatial resolution compared to conventional x-ray imaging. This means that CT can resolve minute details and smaller structures, resulting in a more accurate representation of the scanned area.

In 1917, the Austrian mathematician Johann Radon proved that it was possible to reconstruct a three-dimensional object from infinite projections taken from different angles. This fundamental concept laid the foundation for the development of Computed Tomography (CT).

Cadmium tungstate is commonly used as a scintillation detector in CT. This material is highly efficient at converting x-ray photons into visible light, which is then detected by a photomultiplier tube.

Computed Tomography (CT) is the only modality among the options that can accurately measure the density of body tissues. This is due to its ability to generate cross-sectional images with high spatial resolution, allowing for precise assessment of tissue densities.

For diagnosing intracranial hemorrhage, CT with contrast is often the preferred imaging modality. This is because CT can quickly visualize blood vessels and identify the presence of bleeding within the brain.

A person exposed to around 1000 rem (roentgens equivalent man) of radiation can experience CNS (central nervous system) symptoms and potentially die within one to two days. This highlights the significant dangers of high radiation doses.

A thermoluminescent dosimeter (TLD) is a device used by radiologists to monitor their exposure to radiation. It absorbs energy from radiation and emits light when heated, allowing the amount of radiation received to be measured.

In negative contrast, an organ appears radiolucent because it has a lower atomic weight than the contrast medium used. The contrast medium absorbs more x-rays, making the organ appear darker against a brighter background.

CT scan involves using x-rays to create detailed cross-sectional images of the body. It can visualize not only bones but also soft tissues, making it a powerful tool for diagnosing a wide range of conditions.

Contrast agents are used in CT scans to enhance specific tissues or structures, making them more visible and easier to differentiate from surrounding tissues. This helps radiologists to identify abnormalities and diagnose various conditions.

Current generation CT scanners utilize fan beams and rotating detectors for scanning. The fan beam is a wide beam of x-rays that covers a significant portion of the patient's body, and the rotating detectors allow for rapid acquisition of data from multiple angles.

CT angiography is a specialized CT procedure that uses a contrast agent to visualize the flow of blood in arteries. This technique is particularly helpful for diagnosing conditions affecting blood vessels, such as aneurysms and blockages.

X-rays are a form of electromagnetic radiation. They are produced when high-energy electrons impact a target material, usually tungsten, inside an x-ray tube. The interaction of electrons with the target material results in the emission of x-ray photons.

CT scan is often the best imaging modality for diagnosing liver masses. It can clearly visualize the liver and surrounding structures, allowing for the detection of tumors, cysts, and other abnormalities.

The total workload that an x-ray tube can operate at safely is primarily limited by the heat generated at the target and anode. The intense interaction of electrons with the target material releases a significant amount of heat, which can damage the tube if not controlled.

In an x-ray tube, the target is made of tungsten and is mounted on the solid copper anode. This design helps to dissipate the heat generated during x-ray production and prevent damage to the tube.

To maximize image sharpness, the plane of the film and the plane of the object should be parallel to each other. This ensures that the x-ray beam travels perpendicular to the film, minimizing distortions and improving image clarity.