Lecture Notes Flashcards: X-Ray Production, Density, Contrast, Detail; Radiation Safety; Ultrasound, Nuclear Medicine, CT, MRI

VOCABULARY-style flashcards covering key concepts from Lecture 1–3 notes.

Radiology

Branch of medicine that uses medical imaging to diagnose diseases, including radiography, ultrasound, nuclear medicine, CT, and MRI.

Radiography

Use of X-rays to view internal structures of an object or body.

Ultrasound

Imaging technique that uses high-frequency sound waves to visualize organs and structures.

Nuclear Medicine

Imaging that uses radiopharmaceuticals and gamma rays to visualize physiological processes.

Computed Tomography (CT)

Imaging modality that reconstructs cross-sectional images from X-ray data taken around the patient.

Magnetic Resonance Imaging (MRI)

Imaging modality that uses strong magnetic fields and radio waves to produce detailed images without ionizing radiation.

Ionizing Radiation

Radiation with enough energy to remove tightly bound electrons, potentially causing DNA damage and cancer.

X-ray Production

Process in an X-ray tube where electrons are emitted at the cathode and accelerated toward the anode to produce X-rays.

Cathode

Electrode at the negative side of an X-ray tube that emits electrons.

Anode

Positive electrode in an X-ray tube where electrons collide to produce X-rays.

Tube Voltage

Electric potential that accelerates electrons; higher voltage increases X-ray energy and efficiency.

Tube Current

Electrical current that controls the number of electrons produced; affects X-ray quantity.

Absorption

X-rays absorbed by materials; bones appear light on images due to higher absorption.

Transmission

X-rays that pass through materials; air in lungs appears dark on the image.

Scattering

Deflection of X-ray photons which can degrade image quality.

Gas Appearance on X-ray

Gas appears black because it highly transmits X-rays.

Fat Appearance on X-ray

Fat appears darker than soft tissue due to lower absorption.

Soft Tissue / Water Appearance

Soft tissues appear gray due to moderate X-ray absorption.

Mineral / Bone Appearance

Bone appears light because of high X-ray absorption.

Metal Appearance

Metal appears very light due to near-maximal X-ray absorption.

Tissue Radiosensitivity – High

Rapidly dividing tissues (e.g., lymphoid organs, bone marrow, skin) are highly sensitive to radiation.

Tissue Radiosensitivity – Intermediate

Tissues like growing cartilage, bones, and blood vessels have intermediate sensitivity.

Tissue Radiosensitivity – Low

Mature tissues (e.g., bone, muscle, nervous system) have low sensitivity.

Stochastic Effects

Random radiation effects with no safe threshold; cancer risk increases with dose.

Deterministic Effects

Effects that require a minimum dose and increase in severity with dose (e.g., cataracts, skin damage).

ALARA

As Low As Reasonably Achievable — principle to minimize radiation exposure.

Time (ALARA)

Reduce exposure time and avoid unnecessary retakes.

Distance (ALARA)

Increase distance from the radiation source; exposure decreases with the inverse square law.

Shielding

Use protective barriers (e.g., lead aprons) to reduce exposure to scatter radiation.

Dosimeter

Device used to monitor an individual’s radiation exposure, with monthly readings.

Dose Limit for Under 18

Individuals under 18 should have no exposure."

Pregnant Women Exposure

Pregnant workers should avoid exposure to radiation where possible.

Non-occupational Dose Limit

Public exposure limit: up to 1 mSv per year.

Occupational Dose Limit

Worker exposure limit: up to 50 mSv per year.

Ultrasonography

Imaging modality that uses sound waves beyond the normal hearing range to create images.

Transducer

Device that sends and receives reflected ultrasound waves.

Hyperechoic

Tissue that is brighter on ultrasound, reflecting more sound waves.

Hypoechoic

Tissue that is darker on ultrasound, reflecting fewer sound waves.

Isoechoic

Tissue with the same echogenicity as surrounding tissue.

Anechoic

Region that reflects no sound waves; appears black on ultrasound.

Nuclear Medicine

Imaging that uses gamma rays after administering a radiopharmaceutical to visualize function.

Radiopharmaceutical

Radioactive compound used to visualize or treat tissues in Nuclear Medicine.

Functional Imaging

Imaging that reflects physiology (uptake, metabolism) rather than anatomy.

Bone Scan

Nuclear medicine study assessing bone metabolism to detect abnormalities.

Thyroid Imaging

Nuclear medicine imaging to evaluate thyroid function and detect nodules.

Renal Scan

Nuclear medicine study assessing kidney function and blood flow.

Intravenous (IV) Contrast

Contrast agent injected into veins to enhance imaging in CT or certain MR studies.

CT Gantry Rotation

X-ray generator and detectors rotate around the patient to acquire data.

Multiplanar Reformats (MPR)

Reformatting CT data into different planes for detailed evaluation.

No Superimposition (CT)

CT images provide cross‑sectional views without overlapping structures.

CT Advantages

Fast examination time with excellent bone detail and clarity, often enhanced with IV contrast.

Gold Standard for CNS and MSK (MRI)

MRI is the preferred modality for imaging the brain, spinal cord, and musculoskeletal system.