MRSC1010: Medical Radiation Science 1A Comprehensive Review

Comprehensive practice flashcards covering medical radiation science principles, clinical pathways, patient care ethics, radiation protection standards, imaging modalities, oncology concepts, and technical terminology.

Medical Radiation Science (MRS)

A healthcare discipline in Australia comprising three distinct professions: Diagnostic Radiography (DR), Nuclear Medicine (NM), and Radiation Therapy (RT), all utilizing ionizing radiation for imaging and/or therapy.

Medical Radiation Practice Board of Australia (MRPBA)

The profession-specific National Board that regulates Diagnostic Radiographers, Nuclear Medicine Technologists, and Radiation Therapists; sets registration standards, guidelines, and professional capabilities; and protects the public.

Continuing Professional Development (CPD) Requirements (MRS)

The requirement for qualified practitioners to complete $60\,\text{hours}$ of professional development over a three-year triennium, with at least $10\,\text{hours}$ in any single year and at least $35\,\text{hours}$ of substantive CPD.

Diagnostic Radiographer

A healthcare professional who operates X-ray and other medical imaging equipment to acquire images of the body to demonstrate anatomy and some function, reported by a medical doctor known as a Radiologist.

Nuclear Medicine Technologist (NMT)

A practitioner who prepares and administers radiopharmaceuticals to patients and operates imaging equipment (such as gamma cameras, SPECT/CT, and PET/CT) to record functional and physiological tracer distribution, reported by a Nuclear Medicine Physician.

Radiation Therapist

A practitioner who plans and delivers high-energy ionizing radiation treatments to patients with cancer to shrink tumors or kill cancer cells, working under the oversight of a Radiation Oncologist.

Patient Advocacy (in MRS)

Noticing patient needs, comfort, dignity, or safety concerns early and speaking up to ensure care remains safe, respectful, clinically appropriate, and properly balanced between radiation risk and clinical benefit.

Confidentiality

The legal and ethical professional duty to keep patient information, records, and results secure, accessing and sharing them only when authorized or strictly required for patient care.

Approved Patient Identifiers

A safety requirement (ACSQHC NSQHS Actions 6.05–6.06) to verify patient identity using at least three approved identifiers (such as full name, date of birth, and Medical Record Number [MRN]) before proceeding with clinical care.

Informed Consent

An active voluntary decision-making process where a patient understands the purpose, relevant risks, benefits, alternatives, and next steps of a procedure, retaining the right to ask questions, refuse, or withdraw consent at any time.

Cultural Safety

An environment and clinical interaction experienced as safe, respectful, and free from discrimination by the patient, family, or community, rather than merely intended as respectful by the health practitioner.

Beneficence

The ethical principle of 'doing good' in medical practice by ensuring radiation is used only when it is expected to provide a meaningful diagnostic or therapeutic benefit to the patient.

Non-maleficence

The ethical principle of 'avoiding harm' by eliminating preventable radiation exposure, preventing mismatches, avoiding unnecessary repeated views, and rejecting unsafe shortcuts.

Autonomy

The bioethical principle of 'respecting choice', which requires clinicians to give understandable information, obtain valid consent, and respect the patient's right to accept, refuse, or withdraw from care.

Justification

The fundamental radiation protection principle establishing that radiation exposure is only acceptable when the expected individual or societal clinical benefit clearly outweighs the potential radiation harm.

Optimisation (ALARA)

The principle of keeping radiation exposure 'As Low As Reasonably Achievable', applying sufficient dose to obtain required clinical information or treatment without delivering more than necessary.

Occupational Effective Dose Limit

The statutory boundary for radiation workers set at $20\,\text{mSv/year}$ averaged over 5 consecutive years, with no more than $50\,\text{mSv}$ allowed in any single year.

Public Dose Limit

The statutory radiation limit for members of the general public set at $1\,\text{mSv/year}$, excluding natural background radiation and individual medical exposures.

Declared Pregnant Worker Exposure Limit

The occupational management requirement that once pregnancy is declared, working conditions must be reviewed to ensure the additional dose to the embryo/fetus does not exceed $1\,\text{mSv}$ for the remainder of the pregnancy.

Thermoluminescent Dosimeter (TLD)

A passive personal monitoring device containing a radiation-sensitive crystal (commonly lithium fluoride) that stores radiation energy and releases it as light when heated to estimate absorbed dose.

Optically Stimulated Luminescence (OSL)

A passive personal radiation monitor read using light stimulation after the wearing period; currently utilized by ARPANSA for standard whole-body occupational monitoring.

Electronic Personal Dosimeter (EPD)

An active personal radiation monitor that displays real-time cumulative dose during work and provides audible or visual alarms when preset radiation dose rates or thresholds are reached.

Radiology Information System (RIS)

The administrative and clinical imaging workflow computer system used to manage patient imaging requests, scheduling, exam status, and diagnostic report tracking.

Picture Archiving and Communication System (PACS)

The secure digital medical network system used for capturing, archiving, viewing, retrieving, and distributing medical images across healthcare facilities.

DICOM (Digital Imaging and Communications in Medicine)

The international communication and file-format standard that encodes image pixel data together with crucial study metadata (patient identity, modality parameters, and acquisition details).

Radiation Oncology Information System (ROIS)

A specialized software platform that supports radiation therapy workflow, including simulation, treatment planning, prescription records, verification, and linear accelerator delivery tracking.

Radiopharmaceutical

A radioactive medicinal compound consisting of a radionuclide coupled to a targeting pharmaceutical molecule, administered internally to evaluate organ function or deliver targeted therapy.

Activity (MBq)

The quantitative rate of radioactive decay, commonly expressed in megabecquerels ($\text{MBq}$), where $1\,\text{MBq} = 10^6\,\text{disintegrations per second}$.

Elution

The process of passing sterile saline through a radionuclide generator (such as a Mo-99/Tc-99m column) to extract the daughter isotope (Technetium-99m) as sodium pertechnetate.

Gamma Camera Collimator

A perforated lead plate mounted in front of the scintillation crystal that permits only gamma photons travelling along specific angles to pass, defining the directional origin of detected radiation.

Positron-Electron Annihilation

The physical process in PET imaging where an emitted positron collides with a tissue electron, transforming their combined mass into two $511\,\text{keV}$ gamma photons emitted approximately $180^\circ$ apart.

Three-Phase Bone Scintigraphy

A sequential nuclear medicine protocol consisting of: (1) dynamic blood flow during injection, (2) immediate blood pool imaging of soft-tissue vascularity, and (3) delayed skeletal uptake ($2\text{--}4\,\text{hours}$ later) demonstrating osteoblastic activity.

V/Q Mismatch

A nuclear medicine diagnostic pattern indicative of pulmonary embolism, characterized by preserved ventilation (normal airflow via Technegas) with a wedge-shaped absence or reduction of perfusion (via Tc-99m MAA).

Theranostics

A clinical strategy that directly pairs a diagnostic radiopharmaceutical to image and verify target receptor expression (e.g., Ga-68 DOTATATE or PSMA) with a matching therapeutic radiopharmaceutical (e.g., Lu-177) directed against the exact same target.

Selective Internal Radiation Therapy (SIRT)

An interventional radionuclide procedure using intra-arterially delivered Yttrium-90 ($^{90}\text{Y}$) microspheres to deposit short-range therapeutic beta radiation directly into liver tumors.

Posteroanterior (PA) Projection

A radiographic projection where the central X-ray beam enters the posterior surface of the patient's body and exits through the anterior surface toward the image receptor.

Anteroposterior (AP) Projection

A radiographic projection where the X-ray beam enters the anterior aspect of the patient's body and exits through the posterior aspect before striking the detector.

Radiolucent vs. Radio-opaque

Radiolucent describes tissues of lower attenuation that allow more X-ray photons to reach the detector (appearing darker, like air); radio-opaque describes high-attenuation structures that absorb/scatter photons (appearing lighter/white, like bone or metal).

Hounsfield Unit (HU)

A standardized numerical scale of X-ray attenuation in computed tomography, ranging from $-1000$ (air) to $0$ (water) up to positive values ($>+1000$) for dense bone and metal.

Window Width (WW) and Window Level (WL)

CT display adjustments where Window Width controls the displayed range of Hounsfield Units (governing contrast) and Window Level defines the midpoint value of that range (governing overall brightness).

Anechoic

An ultrasound term describing structures that produce little to no acoustic reflection/echoes, appearing completely black on the monitor (e.g., simple fluid, urine, cysts).

Hyperechoic

An ultrasound term describing tissues that produce intense, strong acoustic reflections, appearing bright white or light grey relative to surrounding tissue (e.g., bone surfaces, calcifications, fibrous tissue interfaces).

Linear Accelerator (Linac)

A medical device used in external beam radiation therapy that accelerates electrons to produce high-energy X-ray beams (photons) for deep tumors or electron beams for superficial lesions.

Gross Target Volume (GTV)

The gross demonstrable extent and location of malignant growth, identifiable by clinical examination, palpation, or imaging modalities.

Clinical Target Volume (CTV)

The tissue volume encompassing the Gross Target Volume (GTV) plus a margin for suspected subclinical microscopic malignant disease and draining regional lymph nodes at risk.

Planning Target Volume (PTV)

A defined geometrical volume that expands beyond the CTV to account for patient setup uncertainties, mechanical beam variations, and internal organ motion.

Organs at Risk (OAR)

Normal, non-cancerous anatomical tissues or sensitive critical structures whose radiation sensitivity influences treatment planning and dose limits to avoid treatment toxicity.

Multi-Leaf Collimator (MLC)

A radiation beam-shaping assembly within the treatment head of a linear accelerator composed of motorized tungsten leaves that move independently to conform the radiation field to the tumor profile.

Brachytherapy

A form of internal radiation therapy where sealed radioactive sources are surgically implanted into (interstitial), placed inside (intracavitary), or applied onto (episcleral) patient tissues near a tumor.

Adjuvant Therapy

An additional cancer treatment (such as chemotherapy or radiation therapy) administered after the primary treatment (usually surgery) to destroy remaining microscopic cancer cells and lower the recurrence risk.

Neoadjuvant Therapy

A treatment modality (such as chemotherapy or radiation therapy) delivered before the primary definitive treatment (usually surgery) to shrink a tumor and improve surgical resectability.

Gray ($\text{Gy}$)

The SI unit of absorbed radiation dose ($1\,\text{Gy} = 1\,\text{J/kg}$), used to prescribe and measure physical energy deposited into tissue during radiation oncology treatment (distinct from effective dose in $\text{mSv}$).

Spatial Resolution

The capacity of an imaging system to distinguish two separate, closely spaced structures as distinct entities, governing the sharpness of structural edges.

Signal-to-Noise Ratio (SNR)

A measure of image quality that compares the level of desired anatomical/functional image signal to the level of background random statistical noise.

IMAACREAP

A standardized clinical image evaluation acronym in Diagnostic Radiography standing for: Identification, Markers, Anatomy, Artifacts, Collimation, Relative position, Exposure, Additional imaging, and Pathology.

Digitally Reconstructed Radiograph (DRR)

A simulated two-dimensional planar reference radiograph calculated from volumetric CT planning data, used in radiation therapy to verify patient setup against portal or on-board images.

Cone-Beam Computed Tomography (CBCT)

A three-dimensional volumetric imaging modality mounted directly onto a linear accelerator gantry to verify soft-tissue alignment and target positioning immediately prior to delivering a treatment fraction.

Triple Test

The diagnostic assessment pathway for a breast lump comprising: (1) clinical history and physical examination, (2) diagnostic imaging (mammography and/or ultrasound), and (3) pathology via core biopsy or fine needle aspiration.

Percutaneous Coronary Intervention (PCI)

A minimally invasive fluoroscopic cardiac procedure that uses balloon catheter dilation and metallic stent deployment to open narrowed or occluded coronary arteries.

Proto-oncogenes

Normal cellular genes that regulate cell growth and division, which can turn into cancer-promoting oncogenes ('accelerator stuck ON') when mutated or amplified.

Tumour-Suppressor Genes

Protective genes that function as the cell cycle's 'brakes' by slowing division, repairing DNA errors, or triggering apoptosis when severe DNA damage is identified.

Angiogenesis

The biological process by which new blood vessels sprout from existing vasculature to provide oxygen, nutrients, and waste disposal to a growing malignant neoplasm.

Carcinoma

A malignant cancer arising from epithelial cells that line internal organs, glands, and body surfaces, representing the most common classification of human malignancies.

Sarcoma

A cancer arising from transformed mesenchymal cells located in bone or soft connective tissues (such as muscle, fat, cartilage, and vessels).

TNM Staging System

A worldwide cancer staging system describing anatomical disease extent based on primary tumor size/depth (T1–T4), regional lymph node involvement (N0–N3), and distant metastasis (M0–M1).

Tumour Grade

The microscopic assessment of cellular differentiation indicating how abnormal cancer cells appear compared to healthy parent tissue, predicting biological aggressiveness.