Learning Radiology Chapter 1 - Recognizing Anything: Past, Present, Future

These flashcards cover the discovery of x-rays, key imaging modalities (CR, CT, US, MRI, Fluoroscopy, Nuclear Medicine), fundamental concepts such as Hounsfield units and radiographic densities, safety considerations, and the emerging role of artificial intelligence in radiology.

Who discovered x-rays and in what year?

Wilhelm Röntgen in 1895.

Why are conventional radiographs often called “plain films”?

Because they are produced with x-rays but without added contrast material such as barium or iodine.

What storage and viewing system has replaced physical film libraries in most radiology departments?

PACS – Picture Archiving, Communications and Storage system.

List the five basic radiographic densities from whitest to blackest.

Metal, calcium (bone), fluid/soft tissue, fat, air.

What are two major advantages of conventional radiography?

Images are quick to acquire and relatively inexpensive; equipment can be portable.

What is the main disadvantage shared by conventional radiography, CT, and fluoroscopy?

They all use ionizing radiation, which carries potential health risks.

What do the initials CT and CAT stand for?

Computed Tomography and Computerized Axial Tomography.

What numeric scale is used to quantify tissue density on CT images?

Hounsfield units (HU), ranging roughly from –1000 to +1000.

On CT, substances with high attenuation appear and have CT numbers.

Whiter; higher (positive).

Define the term “window” in CT imaging.

The selected range of Hounsfield numbers displayed over the available gray scale to optimize visualization of specific tissues.

Name the three standard imaging planes used in cross-sectional imaging.

Axial (transverse), sagittal, and coronal planes.

Give two new applications made possible by fast multislice CT scanners.

Virtual colonoscopy, CT coronary angiography (also acceptable: virtual bronchoscopy, cardiac calcium scoring).

What physical energy does ultrasound use to form images?

High-frequency sound (acoustical) waves above the range of human hearing.

Why is ultrasound particularly useful in pregnant patients and children?

It uses no ionizing radiation and is therefore safer for sensitive populations.

State two limitations of ultrasound imaging.

Cannot penetrate bone; large volumes of gas or obesity can degrade image quality; operator-dependent.

What atomic property is primarily exploited by MRI to generate images?

The magnetic properties of hydrogen nuclei (protons) in water molecules.

Name the common intravenous contrast agent used in MRI and its main purpose.

Gadolinium chelate; enhances detection of lesions and allows MR angiography.

Give two advantages of MRI over CT.

Superior soft-tissue contrast; no ionizing radiation; ability to image in any plane without moving the patient.

List two safety concerns unique to MRI.

Strong magnetic fields can move ferromagnetic objects or affect devices like pacemakers; certain gadolinium agents may have adverse effects.

What does real-time x-ray imaging refer to and which modality provides it?

Fluoroscopy provides real-time visualization using continuous x-ray exposure.

What are “spot films” in fluoroscopy?

Instantaneous static images captured during a fluoroscopic examination.

In nuclear medicine, what term describes a radioactive isotope attached to a carrier molecule?

Radiopharmaceutical.

Which radioisotope is most commonly used in routine nuclear medicine scans?

Technetium-99m (Tc-99m).

Explain the basic principle of PET imaging.

A positron-emitting radioisotope (e.g., FDG) is taken up by tissues; annihilation photons are detected to create 3-D images of metabolic activity.

What clinical area accounts for ~90 % of PET scan usage?

Oncologic imaging – diagnosis, staging, and follow-up of cancers.

How do SPECT scans differ from conventional planar nuclear images?

SPECT acquires multiple 2-D images around the patient and reconstructs them into a 3-D data set.

Why can the patient become a temporary radiation source after a nuclear medicine study?

Because the radiopharmaceutical emits radiation from within the patient’s body until it decays or is excreted.

Define Artificial Intelligence (AI) in the radiology context.

Computer algorithms that interpret or assist in interpreting medical images, often using machine or deep learning techniques.

What is the difference between supervised machine learning and deep learning in AI?

Supervised learning uses human-labeled examples to teach the system; deep learning allows the software to teach itself via neural-network architectures.

Give two current applications of AI in radiology.

Workflow optimization (triaging studies), quantifying disease burden (e.g., lung involvement in COVID-19), assisting in specific diagnoses.

What is the rationale for avoiding x-ray studies during pregnancy when possible?

Ionizing radiation has teratogenic potential and may increase the risk of fetal anomalies.

Which modality is considered the cornerstone of neuroimaging?

Magnetic Resonance Imaging (MRI).

What is meant by “post-processing” in digital imaging?

Manipulating raw image data after acquisition (e.g., windowing CT images) without re-scanning the patient.

Why can’t we see blood inside the heart on a normal chest x-ray?

Because blood (fluid) and the heart’s muscle (soft tissue) share the same radiographic density, making them indistinguishable on conventional radiographs.