MRAD 271 Mid-Term Review Vocabulary

General Pathology & Cellular Repair

Neoplasia
- Defined as an abnormal, uncoordinated, and uncontrolled proliferation of cells that persists even after the initial stimulus that triggered the growth has ceased.
- Neoplastic tissue functions autonomously and competes with normal tissues for nutrients and metabolic resources.
Neoplasms and Swelling
- Neoplasms are commonly referred to as tumors.
- Historically, the term tumor referred to any abnormal swelling or localized mass caused by inflammation, fluid retention, or trauma, before becoming synonymous with neoplastic masses.
Granuloma
- A localized, nodular aggregate of chronic inflammatory cells, composed predominantly of transformed macrophages (epithelioid cells) often coalescing into multinucleated giant cells, surrounded by lymphocytes and plasma cells.
- Formed as a protective immune response to isolate persistent, non-digestible antigens, foreign bodies, or specific pathogens such as Mycobacterium tuberculosis.
Bacteremia
- The presence of viable bacteria within the circulating bloodstream.
- Enters systemic circulation through direct trauma, mucosal surface disruption, surgical site contamination, intravascular line placement, or secondary spillover from localized infections (e.g., urinary tract infections, severe pneumonia, or abscesses).
Fibrous Adhesions and Connective Tissue Repair
- Fibrous connective tissue (collagen and granulation tissue) replaces damaged parenchyma, necrotic cellular debris, or persistent inflammatory exudate during the process of repair by fibrosis or scarring.
Exudate
- An extravascular inflammatory fluid characterized by high protein concentration, cellular debris, and a high specific gravity ( $> 1.020$ ).
- Results from increased microvascular permeability induced by inflammatory chemical mediators during active infection or tissue injury.
Infarction vs. Ischemia
- Ischemia: An inadequate supply of arterial blood flow and oxygen to a specific tissue or organ, resulting from functional or mechanical vascular obstruction, which is potentially reversible if blood flow is promptly restored.
- Infarction: An area of ischemic necrosis caused by complete occlusion of either the arterial supply or venous drainage supplying the affected tissue.
Hematoma
- A localized extravascular collection of blood, usually clotted, trapped within tissue spaces, organs, or body cavities following vessel rupture.
Cardinal Signs of Acute Inflammation
- Tumor: Localized swelling caused by the leakage of fluid and exudate into extravascular interstitial spaces.
- Dolor: Pain resulting from increased local tissue pressure and stimulation of nerve endings by chemical mediators (e.g., bradykinin, prostaglandins).
- Calor: Increased local skin temperature caused by hyperemia and elevated microvascular blood flow.
- Swelling: Physical enlargement of tissue synonymous with tumor, secondary to inflammatory edema.
- Rubor: Redness of the skin or mucous membranes caused by localized arteriolar vasodilation and increased blood flow.
Systemic and Fluid Alterations
- Anasarca: Severe, generalized, body-wide subcutaneous edema accompanied by fluid accumulation in visceral body cavities.
- Elephantiasis: Massive, severe, non-pitting subcutaneous tissue edema and dermal thickening, typically affecting the lower extremities or genitalia, caused by chronic lymphatic obstruction.
- Filariasis: A tropical parasitic infection caused by filarial nematodes (such as Wuchereria bancrofti or Brugia malayi) transmitted by mosquitoes, leading to lymphatic damage and subsequent elephantiasis.
- Pericardial Effusion: Excessive accumulation of fluid within the pericardial cavity surrounding the heart.
- Peritoneal Ascites: Abnormal accumulation of serous fluid within the peritoneal cavity of the abdomen.
- Petechiae: Minute, pinpoint ( $1$ – $2\,mm$ ) superficial hemorrhages into skin, mucosal surfaces, or serosal membranes caused by capillary rupture or platelet dysfunction.
- Purpura: Intermediate-sized ( $3$ – $10\,mm$ ) cutaneous or mucosal hemorrhages resulting from vasculitis, trauma, or bleeding disorders.
- Hemorrhage: The escape of blood from the circulatory system into tissues, body cavities, or externally due to vessel rupture.

Neoplastic Diseases & Oncology

Benign vs. Malignant Neoplasms
- Benign Neoplasms:
- Well-differentiated cells that closely resemble their normal tissue of origin.
- Slow growth rate with low mitotic activity.
- Well-demarcated, localized, and frequently encapsulated.
- Non-invasive and incapable of distant metastasis.
- Malignant Neoplasms:
- Poorly differentiated to anaplastic cells displaying nuclear atypia and pleomorphism.
- Rapid growth rate with frequent and atypical mitotic figures.
- Infiltrative, poorly circumscribed, and non-encapsulated.
- Invade surrounding normal tissues and metastasize to distant anatomical sites.
Neoplasm Classification & Terminology
- Adenocarcinoma: A malignant epithelial neoplasm originating from glandular tissue or displaying glandular cellular structures.
- Adenoma: A benign epithelial neoplasm originating from glandular tissue.
- Carcinoma: A malignant neoplasm originating from epithelial cells covering internal or external body surfaces.
- Chondroma: A benign neoplasm composed of mature cartilage tissue.
- Cystadenoma: A benign adenoma characterized by large, multilocular cystic fluid-filled spaces.
- Fibroma: A benign neoplasm composed predominantly of fibrous or connective tissue.
- Lipoma: A benign neoplasm composed of mature adipose tissue.
- Sarcoma: A malignant neoplasm originating from mesenchymal or connective tissues (such as bone, cartilage, muscle, fat, or blood vessels).
Polyp
- A visible mass or lesion that projects outward above a mucosal surface into the lumen of a hollow organ (e.g., gastrointestinal tract, nasal cavity).
Gastrointestinal Cancer Presentation
- Esophageal & Stomach Cancer Symptoms: Progressive dysphagia (difficulty swallowing), odynophagia (painful swallowing), unexplained weight loss, chronic epigastric pain, early satiety, persistent vomiting, hematemesis (vomiting blood), melena (dark tarry stools), and iron-deficiency anemia.
Routes of Carcinoma Metastasis
- Carcinomas spread primarily through the lymphatic system to regional lymph nodes before entering the bloodstream.
- Secondary hematogenous (bloodborne) dissemination occurs in advanced disease stages.
Disease Staging
- Staging determines the physical size, local extent, regional lymph node involvement, and presence of distant metastasis of a malignant tumor.
- Commonly utilizes the $TNM$ system:
- $T$ : Primary tumor size and local depth of invasion.
- $N$ : Extent of regional lymph node involvement.
- $M$ : Presence or absence of distant systemic metastasis.
- Guides treatment selection, therapeutic options, and overall prognosis.
Male vs. Female Breast Cancer
- Female Breast Cancer: Highly prevalent, affecting approximately $1\text{ in }8$ women (a lifetime risk of roughly $12\%$ ).
- Male Breast Cancer: Rare, accounting for less than $1\%$ of all diagnosed breast cancers (lifetime risk of approximately $1\text{ in }1,000$ ).
Histological Types of Breast Cancer
- Ductal Carcinoma in Situ (DCIS): Non-invasive malignant cells confined within the epithelial lining of the milk ducts without invasion through the basement membrane.
- Invasive Ductal Carcinoma (IDC): The most common invasive breast malignancy ( $80\%$ of cases), breaking through the duct wall into surrounding stroma.
- Invasive Lobular Carcinoma (ILC): Represents roughly $10\%$ of invasive cases, originating in the milk-producing lobules and characterized by single-file linear cell infiltration.
- Inflammatory Breast Cancer (IBC): An aggressive, rare form blocking dermal lymphatics, causing skin erythema, warmth, edema, and a characteristic "peau d'orange" skin appearance.
- Triple-Negative Breast Cancer: Tumors lacking expression of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2).

Genetics & Immunology

Hereditary Abnormalities
- Common hereditary and genetic abnormalities include Down Syndrome (Trisomy 21), Cystic Fibrosis, Sickle Cell Anemia, Hemophilia, Marfan Syndrome, Huntington's Disease, and Neurofibromatosis.
- Down Syndrome is the most common live-birth chromosomal abnormality.
- Cystic Fibrosis is the most common fatal autosomal recessive genetic disorder among Caucasian populations.
Zygosity and Gene Dominance
- Homozygous: Having two identical alleles at a specific genetic locus on homologous chromosomes ( $AA$ or $aa$ ).
- Heterozygous: Having two different alleles at a specific genetic locus ( $Aa$ ).
- Dominant Genes: Alleles that express their phenotypic trait in both the homozygous dominant state ( $AA$ ) and the heterozygous state ( $Aa$ ), fully masking the phenotypic expression of a recessive allele ( $a$ ).
Immune Concepts and Molecules
- Antibodies & Immunoglobulins: Specialized Y-shaped serum proteins secreted by activated plasma cells (B lymphocytes) that bind specifically to target antigens to neutralize toxins, opsonize pathogens, and activate the complement system.
- Antigen: Any foreign substance, agent, or molecule capable of triggering a specific immune response and binding to immune receptors or antibodies.
- Immunoglobulin Classes: Specialized immunoglobulins classified into five distinct functional isotypes: $IgA$ , $IgD$ , $IgE$ , $IgG$ , and $IgM$ .
- Toxoid: An inactivated or attenuated bacterial toxin that has lost its toxic disease-causing properties while retaining immunogenicity, used in vaccines to induce protective antibodies.
- Vaccine: A biological preparation containing weakened, killed, or synthetic components of a pathogen (or mRNA instructions) administered to induce active acquired immunity against specific infectious diseases.
- Human Immunodeficiency Virus (HIV): Retro-viral infection targeting $CD4^+$ T-helper lymphocytes, leading to severe immunocompromise and progressing to Acquired Immunodeficiency Syndrome (AIDS).

Imaging Modalities & Technical Principles

Imaging Modality Capabilities
- Radiography (X-ray): Best known for high-spatial-resolution evaluation of skeletal osseous structures, acute fractures, joint alignment, and basic chest pathology.
- Fluoroscopy: Best known for real-time dynamic functional visualization of internal structures, contrast-filled gastrointestinal studies, and vascular interventional guidance.
- Computed Tomography (CT): Best known for cross-sectional spatial resolution, precise anatomical detail, rapid acquisition, acute intracranial trauma evaluation, and lung parenchymal imaging.
- Magnetic Resonance Imaging (MRI): Best known for superior soft-tissue contrast resolution, multiplanar imaging capabilities without ionizing radiation, and evaluation of the central nervous system, spinal cord, and musculoskeletal joints.
- Ultrasound (Sonography): Best known for non-ionizing, real-time dynamic acoustic imaging, differentiating cystic versus solid lesions, obstetric and pelvic imaging, and Doppler vascular flow dynamics.
- Nuclear Medicine: Best known for assessing physiological and functional processes at the tissue level using radiopharmaceuticals.
- Positron Emission Tomography (PET): Best known for metabolic and molecular imaging, particularly glucose metabolism using radio-labeled tracers.
Computed Tomography Principles
- CT Number (Hounsfield Unit - HU):
- A quantitative linear attenuation measurement of tissue radiodensity relative to distilled water.
- Defined by the formula: $\text{CT Number} = 1000 \times \frac{\mu_{\text{tissue}} - \mu_{\text{water}}}{\mu_{\text{water}}}$
- Standard reference values: Air = $-1000\,HU$ , Water = $0\,HU$ , Dense Bone = $+1000\,HU$ to $+3000\,HU$ .
- High $HU$ values map to brighter white shades, while low $HU$ values map to darker shades on the grayscale display.
- Window Width vs. Window Level:
- Window Width (WW): Controls image contrast by determining the total range of Hounsfield Units displayed across the grayscale.
- Window Level (WL): Controls image brightness by establishing the center $HU$ value of the displayed window width.
- Helical (Spiral) Scanning: Continuous X-ray tube rotation synchronized with continuous patient table movement through the gantry, creating a uninterrupted volumetric spiral dataset.
- Multidetection Scanning (MDCT / Multislice CT): CT architecture utilizing multiple parallel detector arrays along the z-axis, allowing simultaneous acquisition of multiple image slices per single X-ray tube rotation.
- Advantages of Multislice CT: Dramatically reduced scan acquisition times, high temporal resolution, reduced motion artifacts, thinner slice collimation yielding isotropic voxels, and superior 3D multiplanar reformations.
- Postprocessing Techniques in CT: Multiplanar Reformation (MPR), Maximum Intensity Projection (MIP), Minimum Intensity Projection (MinIP), Volume Rendering (VR), Surface Rendering (Shaded Surface Display - SSD), and Virtual Endoscopy.
- Spinal CT Slice Thickness: Typically acquired using fine collimation ranging from $0.625\,mm$ to $1.25\,mm$ .
- Iodinated Contrast Allergy Protocol in CT: Verify allergy details, contact ordering physician and radiologist, implement oral corticosteroid and antihistamine premedication protocols ( $12$ – $24\text{ hours}$ prior), or utilize alternative modalities (unenhanced CT, MRI, or Ultrasound).
- Relative Linear Attenuation: The linear attenuation coefficient ( $\mu$ ) of a material relative to that of water, expressing how effectively a substance attenuates the X-ray beam.
Magnetic Resonance Imaging Principles
- Increasing Exam Specificity in MRI: Optimize pulse sequences (T1-weighted, T2-weighted, STIR, FLAIR, Diffusion-Weighted Imaging), select dedicated surface coils, utilize multiplanar protocols, apply fat saturation techniques, and administer intravenous gadolinium-based contrast agents.
- Functional MRI (fMRI): Measures microvascular hemodynamic changes in local blood oxygenation levels using Blood-Oxygen-Level Dependent (BOLD) signal contrast, mapping neural brain activity during cognitive or physical tasks.
- MRI Safety Zones:
- Zone I: Unrestricted public areas outside the MRI facility (e.g., general hallways and lobbies).
- Zone II: Interface region between unrestricted and restricted zones; initial patient screening, intake, and history taking occur under supervision.
- Zone III: Strictly controlled area restricted to screened MR personnel and patients; poses potential physical hazard from the fringe field (control room, access corridors).
- Zone IV: The magnet room containing the scanner; static magnetic field ( $B_0$ ) is constantly active and poses severe projectile and safety risks.
- Avascular Necrosis (AVN): Death of bone tissue resulting from compromised vascular supply leading to ischemia; best diagnosed with MRI, which offers the highest sensitivity and specificity.
Nuclear Medicine & Molecular Imaging
- Radiopharmaceuticals: Formulations consisting of a radioactive isotope (radionuclide) bound to a biologically active carrier molecule designed to target specific physiological structures or metabolic pathways.
- Scintigraphic Image: A functional 2D planar or dynamic image produced by detecting external gamma ray emissions emitted from radiopharmaceuticals inside the body using a gamma camera.
- SPECT Exam: Single-Photon Emission Computed Tomography; acquisitions using rotating gamma camera heads to capture 3D cross-sectional tomographic slices of single-photon gamma-emitting isotopes (e.g., Technetium-99m / $^{99\text{m}}\text{Tc}$ ).
- PET vs. SPECT Scans:
- PET: Uses positron-emitting radiopharmaceuticals (e.g., Fluorine-18 Fluorodeoxyglucose / $^{18}\text{F-FDG}$ ). Positrons undergo annihilation events producing two simultaneous $511\,keV$ photons emitted $180^\circ$ apart, detected via coincidence counting to produce high-resolution quantitative metabolic images.
- SPECT: Uses single-photon gamma emitters (e.g., $^{99\text{m}}\text{Tc}$ ) detected by physical collimators on rotating gamma cameras, providing functional data at lower spatial resolution and lower cost.
- Fusion Imaging: Co-registration and hardware fusion of functional/metabolic data with detailed anatomical data (e.g., PET/CT, SPECT/CT, or PET/MRI) within a single acquisition session, allowing precise anatomical localization of metabolic lesions.
Ultrasound (Sonography)
- Ultrasound Differentiation: Differentiates solid, cystic (fluid-filled), and complex tissue masses, as well as blood flow parameters via Doppler ultrasound.
- Generations of Ultrasound:
- A-mode (Amplitude mode): 1D spikes representing acoustic echo reflection strength versus depth.
- B-mode (Brightness mode): 2D structural grayscale real-time display using dots of varying brightness.
- M-mode (Motion mode): Displays temporal movement of structures along a single acoustic line (commonly used in echocardiography).
- Real-Time 2D / 3D / 4D Ultrasound: Dynamic multi-dimensional volumetric imaging.
- Doppler & Color Flow Imaging: Visualizes vascular flow dynamics, velocity, and direction.
- Quantitative Data Fusion Requirements: Ultrasound hardware must fuse high-frequency sound reflection timing, acoustic velocity calculations, spatial transducer positioning tracking, and Doppler shift parameters to compute quantitative dimensions and flow velocities.
Demands on Radiographers
- The increasing complexity of modern imaging technology requires radiographers to possess advanced mastery of cross-sectional anatomy, physics, radiation safety protocols, complex computer processing, protocol optimization, image artifact recognition, and patient care.

Respiratory Pathology & Chest Imaging

Respiration Physiology & Pleural Anatomy
- External Respiration: Gas exchange ( $O_2$ and $CO_2$ ) taking place across the alveolar-capillary membrane between the alveolar air spaces and pulmonary capillary blood.
- Internal Respiration: Systemic gas exchange ( $O_2$ and $CO_2$ ) taking place at the systemic capillary level between tissue capillary blood and peripheral parenchymal cells.
- Parietal Pleura: The outer serous membrane lining the internal aspect of the thoracic chest wall, superior surface of the diaphragm, and lateral aspect of the mediastinum.
Central Venous Lines
- Central Venous Catheter (Central Line) Complications: Pneumothorax, hemothorax, accidental arterial puncture, catheter air embolism, tip malposition, catheter-related bloodstream infection (sepsis), venous thrombosis, cardiac arrhythmias, and vessel perforation.
- PICC Line Indications: Peripherally Inserted Central Catheters are best used for long-term intermediate-to-extended intravenous access (weeks to months) to administer chemotherapy, extended parenteral antibiotic therapy, total parenteral nutrition (TPN), or frequent blood sampling.
Pathogens & Respiratory Conditions
- Infectious Volatile Microbe: Bacillus anthracis (Anthrax) is a spore-forming, highly volatile pathogen easily transmitted via inhalation, which served as the name inspiration for the 1980s thrash metal band Anthrax.
- Tuberculoma: A well-defined, encapsulated tumor-like nodule or granuloma consisting of central caseous necrosis, resulting from primary or reactivated tuberculosis.
- Respiratory Syncytial Virus (RSV): A highly contagious viral infection causing bronchiolitis, respiratory mucosal necrosis, and interstitial pneumonia in infants and young children.
Emphysema
- Symptoms: Progressive exertional dyspnea, dry chronic cough, barrel chest appearance (increased anteroposterior diameter), tachypnea, weight loss, and pursed-lip breathing.
- Radiographic Hallmarks: Hyperinflation of lung fields, flattening of diaphragmatic domes, enlargement of the retrosternal clear space, bullae formation, hyperlucency of parenchymal tissue, and attenuation/sparing of peripheral pulmonary vasculature.
Pleural Plaques
- Caused by chronic inhalation and occupational exposure to asbestos fibers (Asbestosis).
Pulmonary Metastasis & Embolism
- Major Metastasis Route: Carcinomas of the stomach, thyroid, and pancreas metastasize to the lungs primarily via the hematogenous (bloodborne) route through the systemic venous circulation and pulmonary arterial tree.
- Pulmonary Emboli (PE) Imaging: Best demonstrated using Computed Tomography Pulmonary Angiography (CTPA).
Pneumothorax
- Characterized by the presence of free air or gas within the pleural cavity surrounding the lung, causing underlying lung collapse.
- Radiographically identified by a hyperlucent region devoid of parenchymal lung markings bounded by a visible visceral pleural line.
Aortic Aneurysms & Abscesses
- Descending Thoracic Aorta Aneurysms: Found in the posterior mediastinum, extending along the thoracic spine distal to the origin of the left subclavian artery down to the aortic hiatus.
- Lung Abscess Radiographic Appearance: A spherical, thick-walled cavity surrounded by consolidated pulmonary parenchyma, characteristically containing an air-fluid level.
Pneumonia & Respiratory Distress Syndromes
- Types of Pneumonia:
- Alveolar (Lobar) Pneumonia: Exudative fluid replaces air in alveolar spaces, affecting entire lobes/segments; characterized by visible air bronchograms (typically Streptococcus pneumoniae).
- Bronchopneumonia: Patchy consolidation originating in bronchi and extending into adjacent alveoli throughout multiple lobes (typically Staphylococcus aureus).
- Interstitial Pneumonia: Inflammatory process predominantly involving alveolar walls and septa; presents as diffuse reticular or linear markings (e.g., Mycoplasma pneumoniae, viral infections).
- Aspiration Pneumonia: Caused by entry of foreign material or gastric contents into lower airways; affects dependent lung regions (posterior segments of upper lobes, superior segments of lower lobes).
- Acute Respiratory Distress Syndrome (ARDS): Severe, life-threatening inflammatory lung condition with diffuse alveolar capillary damage, non-cardiogenic pulmonary edema, and widespread bilateral patchy opacities ("ground-glass" or "white-out").
- Infant Respiratory Distress Syndrome (IRDS / Hyaline Membrane Disease): Occurs in premature neonates due to insufficient pulmonary surfactant production, presenting radiographically with fine diffuse granular opacities ("ground-glass") and air bronchograms.
- Severe Acute Respiratory Syndrome (SARS): Severe viral respiratory infection caused by SARS-CoV, characterized by rapidly progressive lower respiratory tract illness with consolidation and interstitial infiltrates.