Introduction to Medical Imaging: 'Seeing the inside'

Vocabulary practice flashcards covering fundamental concepts, imaging modalities, contrast agents, radiation safety, and clinical indications from the Introduction to Medical Imaging lecture.

Radiology

The medical specialty that visualizes inside the patient to diagnose and treat diseases and injuries; divided into diagnostic and interventional branches.

Interventional Radiology (IR)

A subspecialty that uses real-time image guidance (such as fluoroscopy with a robotic C-arm, CT, or ultrasound) to direct catheters, wires, and needles for minimally invasive diagnostic and therapeutic procedures.

Plain Radiography

A 2D imaging modality that transmits high-energy photons through the body onto a digital cassette or detector to create an image based on tissue attenuation.

Fluoroscopy

A dynamic 'live X-ray video' imaging technique that tracks anatomical motion and guides interventional procedures in real time.

Modified Barium Swallow (MBS)

A specialized dynamic fluoroscopic examination using barium contrast to evaluate swallowing function, motility, structural gut integrity, and to rule out aspiration.

Hysterosalpingography (HSG)

A fluoroscopic procedure utilizing iodinated contrast to assess uterine anatomy and Fallopian tube patency (openness) during workups for female infertility.

Mammography

A specialized radiographic modality utilizing dedicated low-energy X-ray tubes and physical breast compression to maximize soft-tissue contrast; considered the gold standard for early breast cancer screening.

Computed Tomography (CT)

A cross-sectional imaging modality using a rotating X-ray tube and digital detectors coupled with computer reconstruction to generate high-resolution 3D images of bone, soft tissue, and vessels.

Hounsfield Unit (HU)

The quantitative measurement scale of radiodensity used in CT imaging, where air is approximately $-1000\,\text{HU}$, water is $0\,\text{HU}$, fat is around $-100\,\text{HU}$, and dense bone measures $+300\,\text{HU}$ to over $+1000\,\text{HU}$.

Ultrasound

A non-ionizing, cross-sectional imaging technique using high-frequency sound waves reflected off tissue interfaces to generate real-time gray-scale images.

Doppler Ultrasound

A specialized ultrasound technique evaluating real-time hemodynamics, direction, and velocity of blood flow to assess vascular patency and detect conditions like deep vein thrombosis (DVT) and carotid stenosis.

Extended Focused Assessment with Sonography in Trauma (eFAST)

A rapid, bedside point-of-care ultrasound protocol used in trauma patients to identify peritoneal free fluid, hemopericardium, hemothorax, and pneumothorax.

Magnetic Resonance Imaging (MRI)

A cross-sectional imaging modality that utilizes powerful magnetic fields and radiofrequency pulses to excite hydrogen protons in body water and fat, measuring relaxation signals to yield high soft-tissue contrast.

Magnetic Resonance Cholangiopancreatography (MRCP)

A specialized, non-invasive MRI technique that utilizes fluid-sensitive sequences to visualize the intrahepatic and extrahepatic biliary and pancreatic ductal systems without ionizing radiation or contrast injection.

Gamma Camera

A nuclear medicine detector designed to image the distribution of an internally administered radionuclide by capturing emitted gamma rays.

Technetium-99m ($^{99\text{m}}\text{Tc}$)

The most widely utilized nuclear medicine radionuclide, employed in diagnostic studies including bone scintigraphy, MAG3/DMSA renal scans, thyroid imaging, HIDA scans, and myocardial perfusion imaging.

Positron Emission Tomography / Computed Tomography (PET/CT)

A hybrid molecular imaging modality combining a radiotracer highlighting glucose metabolism (PET) with anatomic CT localization in a single examination.

Fluorodeoxyglucose (FDG)

A glucose analogue radiotracer used in PET/CT imaging that accumulates in hypermetabolic tissues such as malignant tumors, active infections, and sites of inflammation.

Stochastic Effect

A radiation risk category characterized by DNA alterations and a probabilistic increase in long-term cancer risk, occurring without a definite dose threshold.

Deterministic Effect

A predictable, dose-dependent radiation injury (such as skin burns or cataract formation) that occurs only after exceeding a specific radiation threshold.

Linear Cumulative Effect

A radiation injury model where biological risk (e.g., osteonecrosis or radiation-induced sarcoma) accumulates in direct proportion to the total absorbed dose over time.

ALARA Principle

The foundational radiation safety guideline standing for 'As Low As Reasonably Achievable', designed to minimize patient and occupational radiation exposure.

Chest X-ray (PA view) Effective Dose

A standard baseline radiation dose reference measuring approximately $0.02\,\text{mSv}$, which is equivalent to roughly $2.5\,\text{days}$ of natural background radiation.

Contrast-Induced Nephropathy (CIN)

Acute kidney injury caused by the administration of iodinated intravascular contrast, occurring in approximately $4\%$ of at-risk patients (especially those with an $\text{eGFR} < 30\,\text{mL/min}$).

Nephrogenic Systemic Fibrosis (NSF)

A rare, debilitating systemic fibrosing disorder linked to older-generation gadolinium-based MRI contrast agents in patients with severe renal failure ($\text{eGFR} < 30\,\text{mL/min}$).

Barium Sulfate

An insoluble, highly radiopaque oral or rectal gastrointestinal contrast medium; strictly contraindicated in patients with suspected bowel perforation, leak, or high-grade bowel obstruction.

Gastrografin

A hyperosmolar, water-soluble iodinated gastrointestinal contrast agent used as an alternative to barium when enteric perforation or anastomotic leakage is suspected; not sterile and contraindicated for intravenous use.

Microbubble Contrast Agents

Intravenous ultrasound contrast agents used for contrast-enhanced ultrasound (CEUS) to evaluate liver lesions and vascular perfusion; safe in renal failure as they are confined strictly to the vascular compartment.

ACR Appropriateness Criteria

Evidence-based guidelines developed by the American College of Radiology to help referring clinicians select the most appropriate imaging study for specific clinical scenarios.

Drilling

The systematic method of viewing cross-sectional imaging data by scrolling sequentially through anatomical slices organ-by-organ and system-by-system.

Radiodensity Terminology (X-ray vs. CT vs. MRI)

Standard radiological descriptors: X-ray uses 'opacity' (white) and 'lucency' (black); CT uses 'hyperdense' (white), 'isodense', and 'hypodense' (black); MRI uses 'hyperintense' (white), 'isointense', and 'hypointense' (black).

CT Pulmonary Angiography (CTPA)

The rapid, contrast-enhanced diagnostic imaging study of choice and gold standard for evaluating suspected acute pulmonary embolism.

Non-Contrast CT (NCCT) Abdomen and Pelvis

The gold-standard, first-line imaging modality for the acute diagnosis and evaluation of suspected urolithiasis (renal and ureteral stones).