Test: General Radiology - 3 - NEET PG MCQ

The CT scanner room is coated with:

• Lead: This material is used to shield against radiation, ensuring safety for both patients and staff.
• Glass: Often used in windows for visibility, but does not provide radiation protection.
• Tungsten: Not typically used for room coatings; it’s more common in certain types of equipment.
• Iron: This material also does not serve as effective radiation shielding.

Therefore, the primary coating used in CT scanner rooms is lead, as it effectively protects against radiation exposure.

The “Time of Flight” technique is a method used in medical imaging to enhance the visualisation of blood vessels. This technique is most commonly associated with:

• MR angiography: It uses magnetic fields and radio waves to create detailed images of blood vessels.
• Spiral CT and CT angiography are primarily used for different imaging processes, focusing on the structure of tissues and organs.
• Digital radiography does not typically use the Time of Flight method.

In summary, the Time of Flight technique is primarily employed in MR angiography.

Ionizing radiation refers to types of radiation that can remove tightly bound electrons from atoms, thus creating ions. Here’s a brief overview of the types mentioned:

• Beta radiation consists of high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei. This type of radiation is ionizing.
• Alpha radiation consists of helium nuclei (two protons and two neutrons). This is also a form of ionizing radiation, as it can cause significant damage to materials it interacts with.
• Gamma radiation consists of high-energy photons. It is highly penetrating and can also cause ionization.
• UV radiation, or ultraviolet radiation, is not typically classified as ionizing radiation. While it can cause chemical reactions and damage to living cells, it does not have enough energy to ionize atoms directly.

Therefore, UV radiation is the type that is not considered ionizing.

The speed of ultrasound (USG) waves travelling through the human body is approximately 1500 m/s. This speed can vary slightly depending on the type of tissue the waves are passing through.

• In soft tissues, such as muscles and organs, the speed is around 1540 m/s.
• In denser tissues, like bones, the speed can increase to about 4000 m/s.
• Understanding these speeds is important for accurate imaging and diagnosis in medical practices.

Therefore, the correct option is the one stating a speed close to 1500 m/s.

Rad is burned to produce energy measured in ergs. The standard energy output when rad is combusted is:

• 100 ergs/g for each gram of rad.
• This means that for every gram burned, it generates a significant amount of energy.

In comparison, other options such as 10 ergs/g, 0.1 erg/g, and 1000 ergs/kg do not accurately reflect the typical energy yield from burning rad.

Thus, the correct value is clearly identified as 100 ergs/g.

In obstetrics, the frequency of ultrasound used for diagnostic purposes typically ranges from 1-20 MHz. This range is ideal for providing clear images of the developing fetus and monitoring the pregnancy.

• Lower frequencies (1-5 MHz) penetrate deeper but provide less detail.
• Higher frequencies (5-20 MHz) offer better resolution but do not penetrate as deeply.
• For most routine checks, frequencies around 2-10 MHz are commonly used.

Using the correct frequency is crucial for accurate imaging and assessment during pregnancy.

The only imaging technique that uses ionising radiation is radiography.

Here's a brief overview of the mentioned techniques:

• Ultrasonography: Uses sound waves, making it safe and non-ionising.
• Thermography: Measures heat emitted from the body, also non-ionising.
• MRI: Uses magnetic fields and radio waves, thus non-ionising.
• Radiography: Involves X-rays, which are ionising radiation.

Therefore, the correct option is radiography as it is the only method that does not use non-ionising radiation.

X-rays are generated when an electron beam strikes the anode in an X-ray tube. Here’s how it works:

• The electron beam is directed towards the anode.
• When the electrons hit the anode, they lose energy.
• This energy loss results in the production of X-rays.

Therefore, the correct process for producing X-rays involves the interaction between the electron beam and the anode.

X-rays are a type of electromagnetic radiation. They are produced when electrons are accelerated and then suddenly decelerated, typically when they collide with a metal target. This process causes the electrons to release energy in the form of X-rays.

• X-rays have very short wavelengths, which allows them to penetrate various materials.
• They are commonly used in medical imaging to view inside the body.
• Because of their ability to penetrate tissues, X-rays help in diagnosing fractures and other conditions.

Contrast in X-rays mainly relies on several key factors:

• KV (kilovolt peak): This affects the energy and penetration ability of the X-rays.
• MA (milliamperes): This determines the quantity of X-rays produced.
• Duration of exposure: Longer exposure times can increase the amount of X-ray contrast.
• Distance between the source and the object: This impacts the intensity of the X-rays reaching the object.

Each of these factors plays a vital role in achieving optimal contrast in X-ray imaging.

Negative contrast medium is a type of material used in medical imaging. It has the following characteristics:

• Easily penetrated by X-rays, allowing for clearer images.
• Not dense, which means it does not block X-rays effectively.
• Typically low in atomic number, making it less visible on X-ray films.

This property makes it useful in various imaging procedures to enhance the visibility of certain areas in the body.

The contract used for MRI involves several important components:

• Perfluorocarbons - These are compounds used in various medical imaging techniques.
• Ferric ammonium citrate - This is often used as a contrast agent to enhance imaging.
• Gadolinium diethylmethylamine - A key substance in MRI for improving the clarity of the images.

All of these components play a crucial role in ensuring high-quality MRI scans.

Nuclear Magnetic Resonance (NMR) is based on the principle of a magnetic field. This technique primarily focuses on the behaviour of atomic nuclei when placed in a magnetic field. Here’s a simplified breakdown:

• NMR involves nuclei, especially protons, which are abundant in hydrogen atoms.
• When placed in a magnetic field, these nuclei absorb and re-emit electromagnetic radiation.
• This interaction provides detailed information about the structure of molecules.
• NMR is widely used in chemistry and medicine, particularly in MRI scanning.

In summary, the core principle of NMR revolves around the effects of a magnetic field on atomic nuclei.

MRI is less effective than CT for identifying calcified lesions. This is because CT scans are specifically designed to provide clearer images of bones and calcifications. Here are some key points to consider:

• CT scans excel at detecting calcifications within tissues.
• MRI is better suited for visualising soft tissues, such as ligaments and tumours.
• In cases of meningeal pathology, MRI is often preferred.
• For ligament injuries, MRI provides more detailed images compared to CT.

Thus, when it comes to calcified lesions, CT is the superior imaging technique.

MRI is a medical imaging technique used to create detailed images of the organs and tissues inside the body. Here are some key points about MRI:

• Contraindications: MRI is not safe for patients with pacemakers as the strong magnetic fields can interfere with their function.
• Bone Marrow Evaluation: MRI is effective for assessing conditions related to the bone marrow, helping to identify diseases such as leukaemia or other cancers.
• Calcified Lesions: MRI is not the best choice for detecting calcified lesions; other imaging techniques like CT scans are generally more effective in these cases.
• Small Brain Lesions: MRI excels at localising small lesions in the brain, making it a valuable tool for neurologists.

The investigation for a patient with a metallic foreign body is not performed using:

• MRI - This imaging technique uses strong magnets and is unsafe with metallic objects.
• USG - Ultrasound is safe and can be used to locate foreign bodies, but it may not be the first choice for metal.
• X-ray - This method is often used to identify metallic foreign bodies as they appear clearly on the images.
• CT - Computed tomography can provide detailed images and is effective for detecting metal foreign bodies.

The EEG cabins need to be completely shielded with a continuous sheet of copper wire mesh. This shielding is essential to prevent interference from external electromagnetic disturbances. This type of shield is known as a Faraday cage.

Ionizing radiation refers to radiation that can remove tightly bound electrons from atoms, creating ions. This type of radiation can be harmful to living organisms.

In contrast, non-ionizing radiation does not carry enough energy to ionize atoms. It is generally considered safer for biological tissues. The following are some key points regarding the modalities mentioned:

• Conventional X-rays are a form of ionizing radiation.
• Computerized tomography (CT scans) also uses ionizing radiation.
• Magnetic resonance imaging (MRI) uses strong magnetic fields and radio waves, making it a non-ionizing modality.
• Isotopic scanning typically involves radioactive materials and is thus ionizing.

Therefore, among the options provided, MRI is the non-ionizing modality.

In an emergency room, if a patient shows signs of a focal neurologic deficit, the best first step is to conduct a CT scan. This imaging technique is quick and effective for identifying serious issues such as strokes or bleeding in the brain.

• CT scans provide fast results, which is critical in emergencies.
• They are widely available and can be performed quickly.
• CT scans can help doctors make immediate decisions about treatment.

Other options like MRI or lumbar puncture are useful but take longer and are not the first choice in acute situations.

When assessing a fracture of the nose, the appropriate X-ray view to take is the lateral view. This view provides a clear side profile of the nasal structure, helping to identify any fractures or misalignments.

• The Waters view is mainly used for examining the maxillary sinus and does not focus on nasal fractures.
• Caldwell's view is useful for viewing the frontal sinuses but is not ideal for nasal fractures.
• The occlusive anterior view is less commonly used for this purpose.

In summary, the lateral view is the best choice for evaluating nasal fractures.

• Ionic monomers contain three iodine atoms for every two particles in solution. This is important for understanding their structure.
• High osmolar contrast agents can be either ionic or nonionic. This means they can have different properties and effects on the body.
• Gadolinium is a contrast agent that has the ability to cross the blood-brain barrier, which is significant in certain medical imaging procedures.
• Iohexol is classified as a high osmolar contrast medium, which means it has a higher concentration of particles compared to other agents.

The Doppler effect occurs due to a change in the frequency of sound. This change is typically perceived when the source of sound moves relative to an observer. Here’s a simplified explanation:

• When a sound source moves towards an observer, the sound waves are compressed, causing a higher frequency.
• If the sound source moves away from the observer, the waves are stretched, resulting in a lower frequency.
• This effect is commonly heard in situations like a passing ambulance siren.

In summary, the Doppler effect is primarily related to changes in frequency rather than amplitude or direction.

The best method to investigate a subdural hemorrhage is through a Non-Contrast Computed Tomography (NCCT) scan. This imaging technique is effective because it can quickly detect any bleeding in the brain.

Key reasons for using NCCT include:

• Speed: It provides fast results, which is crucial in emergency situations.
• Accessibility: NCCT machines are widely available in hospitals.
• Effectiveness: It clearly shows areas of bleeding, allowing for prompt diagnosis.

Other methods like angiography, CECT, and MRI may be used but are not the first choice due to their limitations in speed or availability.

In patients with reduced kidney function, it is essential to choose the right contrast agent to minimise the risk of contrast nephropathy. The preferred choice is:

• Low osmolar contrast agents. These are less likely to cause kidney damage compared to other types of contrast media.

Using low osmolar contrast helps to protect kidney function, especially in those at risk. Other options like acetylcysteine, fenoldopam, or mannitol are not as effective in preventing this specific condition.

High resolution computed tomography (HRCT) of the chest is particularly effective for assessing:

• Interstitial lung disease: This condition involves inflammation and scarring of the lung tissue, making HRCT essential for detailed imaging.
• Other conditions, such as pleural effusion, lung mass, and mediastinal adenopathy, can also be evaluated, but HRCT is most valuable for interstitial lung disease.

The detailed images produced by HRCT help doctors identify changes in lung structure, leading to better diagnosis and treatment planning.