Radiation Biology

Course Description

RTE2385C – Radiation Biology is a 3-credit course of roughly 48 contact hours in Florida's Radiography A.S. curriculum, usually taken in the second year. It is frequently titled Radiation Biology and Protection or Radiographic Protection and Biology, and those longer titles describe it better: the course covers what ionizing radiation does to living tissue, and what a radiographer does about it.

The biology half traces the effects of radiation from the physical interaction through to the clinical outcome. Students cover radiation interactions with matter, direct and indirect action, the radiolysis of water and free radical formation, DNA damage and repair, cell survival curves, and the factors affecting radiosensitivity — including the law of Bergonié and Tribondeau and the relative sensitivity of different tissue types.

From there the course covers deterministic effects (which have a threshold and increase in severity with dose: erythema, epilation, cataracts, sterility, acute radiation syndrome) and stochastic effects (which have no threshold and increase in probability rather than severity: carcinogenesis and heritable effects). The distinction is the conceptual core of the course, since it determines how protection is approached.

The protection half covers ALARA, dose limits for occupational workers and the public, the cardinal principles of time, distance, and shielding, personnel monitoring and dosimetry, protective apparel and structural shielding, and the specific practices that reduce patient dose — collimation, filtration, shielding, technique selection, grid selection, and repeat reduction.

Special protection situations receive attention: the pregnant patient and the pregnant worker, pediatric patients, fluoroscopy and its comparatively high dose rates, and mobile radiography.

Offered at approximately 18 Florida institutions with accredited radiography programs, including Broward, College of Central Florida, Daytona State, Florida SouthWestern, Gulf Coast State, Hillsborough, Indian River State, Miami Dade, Northwest Florida State, Palm Beach State, Pensacola State, Pasco-Hernando, Santa Fe, South Florida State, St. Petersburg, Tallahassee State, and Valencia.

Learning Outcomes

Required Outcomes

• Describe the interactions of ionizing radiation with matter and with biological tissue.
• Explain direct and indirect action and the role of free radicals in radiation damage.
• Describe DNA damage, repair mechanisms, and the consequences of unrepaired damage.
• Interpret cell survival curves and describe the factors affecting radiosensitivity.
• Apply the law of Bergonie and Tribondeau to predict relative tissue radiosensitivity.
• Distinguish deterministic from stochastic effects and describe examples of each.
• Describe acute radiation syndrome and its dose-dependent presentations.
• Describe late effects including carcinogenesis, cataractogenesis, and heritable effects.
• Describe radiation units of measurement and dose quantities.
• Apply ALARA principles and the cardinal principles of time, distance, and shielding.
• Describe occupational and public dose limits and the basis for them.
• Describe personnel monitoring devices, their use, and the interpretation of dosimetry reports.
• Apply patient protection practices including collimation, filtration, shielding, and technique selection.
• Describe protection considerations for the pregnant patient, pregnant worker, and pediatric patient.
• Describe protection practices in fluoroscopy and mobile radiography.

Optional Outcomes

• Describe structural shielding design principles.
• Describe regulatory agencies and their roles in radiation protection.
• Describe dose reduction in computed tomography.
• Describe radiation dose tracking and patient dose registries.
• Analyze case studies of radiation overexposure incidents.
• Describe radiation risk communication with patients.

Major Topics

Required Topics

• Radiation interactions — photoelectric and Compton interactions and their biological significance.
• Molecular and cellular radiobiology — direct and indirect action, radiolysis of water, and free radicals.
• DNA damage and repair — damage types, repair mechanisms, and misrepair.
• Cell survival and radiosensitivity — survival curves, the cell cycle, oxygen effect, and dose rate.
• Tissue and organ response — the law of Bergonie and Tribondeau and relative tissue sensitivity.
• Deterministic effects — threshold, severity relationship, erythema, epilation, cataracts, and sterility.
• Acute radiation syndrome — hematopoietic, gastrointestinal, and central nervous system syndromes.
• Stochastic effects — no threshold, probability relationship, carcinogenesis, and heritable effects.
• Radiation units and quantities — absorbed dose, equivalent dose, and effective dose.
• ALARA and cardinal principles — time, distance, and shielding in practice.
• Dose limits — occupational, public, embryo/fetus, and the basis for each.
• Personnel monitoring — dosimeter types, placement, and report interpretation.
• Patient protection — collimation, filtration, shielding, technique, grids, and repeat reduction.
• Special situations — pregnancy, pediatrics, fluoroscopy, and mobile radiography.

Optional Topics

• Structural shielding design.
• Regulatory agencies and standards bodies.
• CT dose optimization.
• Dose tracking and registries.
• Overexposure case studies.
• Communicating radiation risk to patients.

Resources & Tools

• Radiologic Science for Technologists (Bushong), Elsevier — the standard text; its radiobiology and protection sections anchor this course.
• Radiation Protection in Medical Radiography (Sherer, Visconti & Ritenour), Elsevier — widely adopted for this course specifically.
• Essentials of Radiation Biology and Protection (Statkiewicz Sherer), Cengage.
• NCRP reports — the authoritative U.S. source for dose limits and protection recommendations.
• ICRP publications — international protection framework.
• Florida Department of Health, Bureau of Radiation Control — state regulation, equipment inspection, and licensure.
• ARRT content specifications — the Safety domain, which this course substantially covers.
• Image Gently and Image Wisely — national dose reduction campaigns for pediatric and adult imaging.
• Dosimeters and dosimetry reports for practical interpretation exercises.

Career Pathways

• Radiologic Technologist (SOC 29-2034) — radiation protection is a daily professional obligation.
• Radiation Safety Officer — institutional role, typically requiring additional qualification.
• Computed Tomography Technologist — where dose optimization matters most acutely.
• Quality Management and Compliance roles in imaging departments.
• Medical Physicist assistant or Dosimetrist — related pathways requiring further education.
• Program Faculty — teaching radiobiology and protection.

Special Information

Course-code and title variation

The course appears as RTE2385 and RTE2385C, and under the titles Radiation Biology (the SCNS title), Radiation Biology and Protection (Broward, 3 credits and 48 contact hours), and Radiographic Protection and Biology (Northwest Florida State). Under SCNS these are equivalent at the same level; credit value is consistently 3.

Prerequisites

Prerequisites are program-sequence based. Broward requires RTE1523, RTE1523L, and RTE1824 each with a minimum grade of C, with RTE2457, RTE2457L, and RTE2834 as corequisites. Admission to the radiography program precedes all of it. Verify locally.

Position in the curriculum and ARRT weighting

This is a second-year course and its content forms a substantial part of the ARRT examination's Safety domain. It is reviewed again in RTE2061 Radiographic Seminar, but students who treat radiobiology as memorization in this course tend to struggle in review, because the examination asks them to reason from principles.

The deterministic/stochastic distinction is the key concept

If a student takes one thing from this course, it should be this. Deterministic effects have a threshold and get worse with dose — they are avoidable by staying below the threshold, and in diagnostic radiography they essentially do not occur outside prolonged fluoroscopy. Stochastic effects have no threshold: any dose carries some probability of inducing cancer, and that probability rises with dose while the severity does not. This is why ALARA exists, why there is no "safe" dose to justify an unnecessary examination, and why the answer to "is this exposure harmful?" is about probability rather than certainty. Students who conflate the two give wrong answers on both the examination and in practice.

Protecting yourself and protecting the patient are different problems

Occupational protection relies primarily on distance and shielding — the technologist steps behind a barrier. Patient protection relies on technique and beam restriction, because the patient is in the beam by necessity. Students sometimes conflate the two sets of practices; the course keeps them distinct.