Modalities of Medical Imaging

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Questions and Answers

What is the term used to describe an imaging finding that does not directly correspond to the reality of the patient?

Radiodensity

Radiolucent

Interface

Artifact (correct)

What is the initial imaging study of choice for a 65-year-old male presenting with shortness of breath and chest pain?

CT of chest

Chest Radiograph (correct)

MRI of chest

Nuclear medicine V/Q scan

What type of imaging modality uses ionizing radiation to produce an image?

Radiography (correct)

MRI

Ultrasonography

PET

What is the term used to describe the border between two different radiodensities?

Interface Signup and view all the answers

What is the modality of choice for a patient with blunt trauma to the chest after a high-speed MVA?

Chest Radiograph Signup and view all the answers

What is the term used to describe structures that block x-rays and appear white on a radiograph?

Radiopaque Signup and view all the answers

What is the main purpose of Radiography?

To visualize bony structures Signup and view all the answers

Who discovered x-rays in 1895?

Roentgen Signup and view all the answers

What is image contrast in Radiography?

The difference in brightness between an area of interest and its surroundings Signup and view all the answers

What is the term used to describe medical images that are the “shadows” projected onto a flat plane when x-rays pass through a patient?

Radiograph Signup and view all the answers

What is the primary indication for ordering a CT scan of the chest?

All of the above Signup and view all the answers

What is the preferred clinical indication for selecting MRI of the chest?

Soft tissue injury Signup and view all the answers

What is the term used to describe structures that allow x-rays to pass through and appear gray to black on a radiograph?

Radiolucent Signup and view all the answers

What is the term used to describe the categories of imaging modalities?

Radiating and Non-radiating Signup and view all the answers

What is the primary advantage of Ultrasound over other imaging modalities?

Real-time imaging Signup and view all the answers

Which of the following imaging modalities is typically used to evaluate metabolic activity?

Nuclear Medicine/PET Signup and view all the answers

What is the characteristic of the flow in a carotid artery with a build-up of fatty deposits?

Turbulent, like rapids in a river Signup and view all the answers

Which of the following is NOT a clinical indication for Doppler sonography?

Measuring bone density Signup and view all the answers

What is the primary advantage of using ultrasound in gynecologic exams?

Lack of radiation Signup and view all the answers

What is the purpose of using Doppler effects in ultrasound?

To assess volume, speed, and direction of flow Signup and view all the answers

What is the term for the ultrasound examination used to evaluate the torso for free fluid in cases of trauma?

Focused assessment with sonography for trauma (FAST) Signup and view all the answers

What is the name of the type of ultrasound used to detect wall motion abnormalities in the heart?

Echocardiography Signup and view all the answers

What is a limitation of ultrasound in obese patients?

Penetration is difficult due to increased soft tissue Signup and view all the answers

What is the primary route of excretion for intravascular iodinated contrast material in patients with normal renal function?

Renal system Signup and view all the answers

What is the typical duration of contrast agent elimination in dialysis patients?

2 to 4 hours Signup and view all the answers

What type of reaction can occur in response to contrast agent administration?

Both anaphylactoid and chemotoxic reactions Signup and view all the answers

What is the primary purpose of administering contrast agents in imaging?

To create a temporary, artificial density difference Signup and view all the answers

What type of MRI contrast agents can delineate vessels as well as parenchymal tissues?

Diffusion agents Signup and view all the answers

What is a benefit of using ultrasound in medical imaging?

Portability Signup and view all the answers

What is a common precaution taken in patients with a history of contrast allergy?

Pretreatment with antihistamines and corticosteroids Signup and view all the answers

What type of signal is produced by cartilage and muscle?

Hypoechoic signal Signup and view all the answers

What is the typical feature of cysts and homogeneous solid masses, such as lymphomas?

Anechoic signal Signup and view all the answers

What does color Doppler display?

Velocity and direction of blood flow Signup and view all the answers

What is plotted on the vertical scale (y-axis) in Doppler spectral display?

Velocity Signup and view all the answers

What is the significance of brighter colors in color Doppler?

Higher mean velocities Signup and view all the answers

What is the direction of flow represented by the color above the black bar in color Doppler?

Flow towards the Doppler beam Signup and view all the answers

What is the purpose of Doppler sonography?

To provide functional information about blood flow Signup and view all the answers

What is the typical feature of acoustic enhancement?

Structures appear brighter Signup and view all the answers

Study Notes

Radiography

Radiography is a type of medical imaging that uses x-rays to produce images.
It is also known as x-ray, plain film, radiograph, and conventional radiograph.
Radiography was discovered by Roentgen in 1895.
Radiography refers to the medical images that are the "shadows" projected onto a flat plane (planar) when x-rays pass through a patient.

Image Contrast

Image contrast is the difference in brightness between an area of interest and its surroundings.
The larger the difference in brightness between different tissue types, the easier it is to differentiate them from each other.

Artifacts and Interfaces

An artifact is an imaging finding that does not directly correspond to the reality of the patient.
Artifacts may mimic a clinical feature, degrade image quality, or obscure anatomy.
Radiological interfaces are between different radiodensities, such as the border of the heart against the lung.

Planar vs Cross-Sectional Imaging

Planar images are shadows of complex three-dimensional objects, e.g. radiography.
Cross-sectional images show the three-dimensional reality of anatomy, e.g. CT, ultrasound, and MRI.

Categories of Medical Imaging

Radiating imaging modalities: use ionizing radiation to produce an image, e.g. radiography, CT, nuclear medicine.
Non-radiating imaging modalities: do not use ionizing radiation to produce an image, e.g. MRI, ultrasound.

Five Basic Densities Seen on Conventional Radiography

Radiopaque: denser structures block x-rays better, appear white on radiograph.
Radiolucent: less dense structures allow x-rays to pass through, appear gray to black on radiograph.
Cartilage and muscle: produce a hypoechoic signal, appear dark as most waves pass through the tissue.
Fluid and fluid-filled structures: produce an anechoic signal, appear black as there is no reflection of ultrasound waves.

Ultrasound

Ultrasound uses high-frequency sound waves to produce images.
It is also known as sonography.
Doppler sonography provides valuable information regarding the presence, direction, and velocity of blood flow.
Clinical indications for ultrasound include gynecologic exams, echocardiography, abdominal exams, and procedures.

Strengths and Weaknesses of Ultrasound

Strengths: lack of ionizing radiation, low cost, portability, lack of use of contrast.
Weaknesses: cannot penetrate gas or bone, obese patients may be difficult to penetrate, dependent on the skills of the operator scanning.

Contrast Agents

Contrast agents are used to distinguish adjacent tissues in imaging by creating a temporary, artificial density difference between objects.
Contrast agents can be used in radiography and CT.
Iodinated contrast material is excreted through the renal system.
Contrast reactions can be anaphylactoid or chemotoxic reactions.

Magnetic Resonance Contrast Agents

The two classes of MRI contrast agents are diffusion and non-diffusion agents.
Diffusion agents can delineate vessels as well as parenchymal tissues.
Non-diffusion agents remain in the bloodstream and are primarily useful for MRA.

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Description

This quiz covers the principles of Radiography, CT, Molecular Imaging, MRI, and Ultrasound, including image generation processes, terminology, and clinical indications.