| 1. Domain | 1.1 Scope of the Domain | Boundaries | The range of phenomena the science includes and excludes. | Includes the application of physical principles to medical imaging, radiation therapy, radiation safety, treatment planning, diagnostic measurements, dosimetry, and device calibration. Covers interactions of ionizing and non ionizing radiation with biological tissues, image formation physics, therapeutic dose delivery, and technological optimization of diagnostic and therapeutic systems. Excludes purely biological interpretation of disease, clinical decision making, and non physical medical sciences. |
| | Scale | The spatial, temporal, or organizational level at which the science operates (e.g., quantum, cellular, social, cosmic). | Operates from atomic scale radiation interactions, to cellular and tissue scale dose deposition, to organ level imaging fields, and whole body treatment planning. Timescales range from femtosecond radiation interactions to multi minute imaging or therapy cycles. |
| 1.2 Ontological Commitments | Entities | The kinds of things assumed to exist within the domain (particles, organisms, agents, fields, etc.). | Photons, electrons, protons, neutrons, radionuclides, electromagnetic fields, radiation beams, detectors, tissue-equivalent materials, imaging contrast agents, dose distributions, and therapeutic devices. |
| | Properties | The fundamental attributes these entities possess (mass, charge, genotype, preference, etc.). | Energy, attenuation coefficient, stopping power, scattering cross section, decay rate, dose, field strength, spatial resolution, contrast, signal to noise ratio, and biological effectiveness. |
| | Categories | The basic ontological types used to classify domain elements (substances, processes, relations, structures). | Imaging modalities, radiation types, detection methods, dose delivery mechanisms, calibration standards, tissue response models, and safety classifications. |
| 1.3 State-Variables | Variables | The measurable or definable properties that describe system conditions. | Beam energy, dose rate, fluence, detector counts, voxel intensities, attenuation coefficients, field uniformity, decay activity, contrast concentration, and patient positioning parameters. |
| | Parameterization | How variables encode and represent the system’s state. | States encoded by beam profiles, radiation spectra, voxel maps, dose volume histograms, calibration curves, decay equations, transfer functions, and image reconstruction parameters. |
| 1.4 Admissible Idealizations | Simplifications | Conceptual reductions used to make the domain tractable (point masses, rational agents, perfect gases). | Homogeneous tissue approximations, simplified scattering models, ignoring patient motion, ideal detector response, monoenergetic beam assumptions, linear attenuation models, or neglecting biological repair processes in preliminary dose estimations. |
| | Validity Conditions | The limits and contexts in which idealizations hold or break down. | Valid when tissues are approximately uniform, when motion artifacts are minimal, when radiation interactions are dominated by known processes, when dose gradients are smooth, and when simplified patient geometry remains acceptable. Breaks down in highly heterogeneous tissue, rapid motion, extreme dose gradients, or unusual radiobiological conditions. |
| 1.5 Domain Assumptions | Structural Assumptions | Background ontological stances such as determinism, continuity, randomness, discreteness. | Assumes radiation interactions follow physical cross section laws, detectors operate within calibration limits, dose deposition can be modeled using transport physics, and biological response correlates with physical dose metrics. |
| | Implicit Commitments | Unstated but necessary assumptions that shape the field’s conceptual structure. | Assumes calibration standards accurately map to real dose, tissue equivalence models represent patient anatomy, imaging artifacts remain manageable, and reconstructed images correspond consistently to physical structures. |
| 1.6 Internal Coherence Requirements | Consistency | The demand that domain concepts do not contradict one another. | Requires consistency among imaging models, radiation transport models, dose calculations, detector response, calibration procedures, and biological effect models. |
| | Compatibility | The requirement that entities, variables, and assumptions fit together into a unified descriptive framework. | Entities, variables, and assumptions must jointly support a unified framework linking radiation physics, imaging, dosimetry, device operation, calibration, and clinical treatment requirements. |
| 2. Evidence Layer | 2.1 Observable Phenomena | Observables | The aspects of the domain that can produce detectable signals accessible to measurement. | Observable signals include X ray attenuation, gamma ray counts, CT voxel intensities, MRI relaxation signals, ultrasound echoes, charged particle depth dose profiles, positron emission distributions, radiation scatter patterns, detector current, portal imaging signals, and ionization chamber readings. |
| | Detection Limits | The boundaries of what can be resolved or sensed by current instruments or methods. | Limited by detector sensitivity, electronic noise, spatial resolution of imaging systems, beam energy limits, patient motion, scatter contamination, partial volume effects, saturation in high dose regions, and depth penetration constraints. |
| 2.2 Measurement Systems | Units | Standardized quantifications (meters, seconds, volts, decibels, dollars, etc.) necessary for consistent comparison. | Uses gray (dose), sievert (effective dose), becquerel (activity), electron volt (energy), hertz, meters, seconds, amperes, volts, counts per second, attenuation coefficients, and HU units in CT. |
| | Instruments | Devices and tools (microscopes, spectrometers, sensors, surveys, detectors) used to produce measurements. | Instruments include ionization chambers, scintillation detectors, dosimeters, CT scanners, MRI systems, ultrasound probes, PET scanners, SPECT cameras, linear accelerators, beam profilers, laser alignment tools, and radiation survey meters. |
| 2.3 Operational Definitions | Definitions | Terms defined by specific measurement procedures, ensuring empirical clarity. | Terms such as absorbed dose, effective dose, attenuation coefficient, beam quality index, signal to noise ratio, modulation transfer function, relaxation time, and activity concentration are defined by standardized physics-based measurement protocols. |
| | Procedures | The explicit steps required to perform a measurement in a reproducible way. | Procedures include detector calibration runs, CT or MRI phantom scans, beam profile mapping, isocenter verification, signal averaging, decay curve fitting, imaging sequence optimization, and repeated measurements to improve signal reliability. |
| 2.4 Data Acquisition | Protocols | Formal processes for gathering data under controlled or standardized conditions. | Data gathered through gated imaging, synchronized detector timing, fixed acquisition windows, multislice or volumetric scans, multiangle projections, repeated dose measurements, dynamic imaging sequences, and controlled positioning protocols. |
| | Sampling | Rules determining which subset of the domain is measured and how representative it is. | Sampling rules include voxel grid sampling in imaging, time sampling for dynamic scans, spatial sampling in dose mapping, repeated acquisitions for noise suppression, angular sampling in tomographic systems, and energy bin sampling in spectral detectors. |
| 2.5 Data Character & Format | Data Types | The form raw evidence takes (time series, spectra, images, counts, qualitative records). | Data appears as radiographic images, CT voxel volumes, MRI signal maps, radionuclide distribution images, ultrasound echo patterns, dosimetry curves, beam profiles, calibration tables, and detector count time series. |
| | Resolution | The granularity or precision with which data is captured. | Determined by detector pixel size, reconstruction algorithm quality, sampling frequency, gradient strength in MRI, ultrasound wavelength, beam spot size, noise filtering, and system bandwidth. |
| 2.6 Reliability & Calibration | Calibration | Adjustment procedures ensuring instruments produce accurate results. | Calibration uses phantom scans, ion chamber calibration factors, radionuclide standards, reference dose measurements, detector dark noise subtraction, flat field correction, geometric calibration, and periodic system QA procedures. |
| | Error Characterization | Identification and quantification of noise, uncertainty, bias, and measurement error. | Errors arise from patient motion, detector drift, beam instability, scatter contamination, partial volume effects, reconstruction artifacts, dead time losses in counting systems, calibration inaccuracies, and environmental conditions impacting detectors. |
| 3. Structural Layer | 3.1 Patterns & Regularities | Laws / Relations | Stable, repeatable patterns governing how observables behave across conditions. | Stable patterns include exponential attenuation of photons, dose falloff with depth for charged particles, relaxation time relationships in MRI, acoustic impedance matching in ultrasound, radioactive decay laws, scatter behavior, and predictable correlations between beam quality and tissue contrast. |
| | Invariants | Quantities or properties that remain constant under transformations (symmetries, conservation laws). | Invariants include conservation of energy in radiation interactions, fixed decay constants for radionuclides, symmetry of dose deposition around isocenter in well calibrated systems, linearity of detector response within valid ranges, and constant physical cross sections under given energies. |
| 3.2 Causal Architecture | Mechanisms | Underlying processes or structures that produce the observed regularities. | Mechanisms arise from photon absorption and scattering, charged particle stopping power, nuclear decay, proton Bragg peak formation, electromagnetic induction in MRI, acoustic pulse propagation in tissues, and ionization energy transfer in detectors and tissues. |
| | Pathways | Organized sequences of interactions forming a causal chain or network. | Pathways include radiation entering tissue, interacting via photoelectric, Compton, or pair production processes; charged particle slowing and energy deposition; ultrasound pulses reflecting at interfaces; radionuclide decay emitting detectable radiation; and MRI spins relaxing back to equilibrium. |
| 3.3 Theoretical Vocabulary | Concepts | Core terms that encode the domain’s structure (force, gene, equilibrium, field). | Core terms include attenuation coefficient, stopping power, Bragg peak, half life, relaxation time, acoustic impedance, signal to noise ratio, contrast mechanism, scatter kernel, and dose deposition profile. |
| | Classifications | Taxonomies, categories, or typologies that organize entities and relations. | Classifies imaging modalities (CT, MRI, PET, SPECT, ultrasound, radiography), radiation types (photons, electrons, protons, neutrons), interaction processes (absorption, scatter, decay), treatment systems (linear accelerators, proton therapy), and tissue response models. |
| 3.4 Formal Representations | Equations | Mathematical constructs expressing laws, relations, or mechanisms. | Includes Beer–Lambert law, radioactive decay equations, Bethe stopping power equation, Larmor precession relation, Bloch equations, acoustic wave equations, dose calculation algorithms, and transport equations for radiation and particles. |
| | Models | Structured representations—mathematical, computational, or conceptual—used to predict and explain phenomena. | Uses Monte Carlo transport models, dose calculation models, MRI signal models, ultrasound propagation models, reconstruction algorithms for CT or PET, scatter correction models, and biological response models such as linear quadratic dose response. |
| 3.5 Idealized Structures | Simplified Models | Purposeful abstractions that capture essential dynamics while omitting irrelevant detail. | Idealizations include homogeneous tissue assumptions, monoenergetic beams, simplified scatter models, ignoring motion, assuming perfect detector response, using 1D depth dose models, and employing uniform magnetic or acoustic fields. |
| | Limit Conditions | Regimes where specific models or approximations hold (classical vs. quantum, linear vs. nonlinear). | Valid when anatomy is uniform, detector behavior is stable, patient motion is controlled, beam energy is narrow, scatter is moderate, and biological effects remain within calibration; breaks down in highly heterogeneous anatomy, strong motion, low signal regimes, or extreme dose gradients. |
| 3.6 Integrative Frameworks | Unifying Theories | Higher-order structures that connect disparate laws or mechanisms under a coherent whole. | Integrates radiation transport, electromagnetism, acoustics, nuclear physics, detector physics, image reconstruction, and radiobiology into unified diagnostic and therapeutic models. |
| | Interdisciplinary Links | Points where the theory connects to adjacent sciences or larger explanatory systems. | Links to nuclear medicine, radiology, oncology, biomedical engineering, computational physics, electrophysiology, and medical instrumentation design. |
| 4. Method Layer | 4.1 Inquiry Design | Experimental Design | Structured plans for manipulating variables to test causal claims. | Experiments vary beam energy, dose rate, detector configuration, imaging parameters, patient phantom geometry, contrast concentration, acquisition sequence, or field strength to determine causal effects on image quality, dose deposition, detector behavior, or therapeutic outcome. |
| | Observational Design | Systematic approaches for gathering non-manipulated data (surveys, field studies, natural experiments). | Observational designs collect non manipulated diagnostic or therapeutic data, such as passive dose tracking, scatter behavior in vivo, real time MRI changes, patient motion effects, or natural radionuclide decay patterns without external parameter changes. |
| 4.2 Testing & Validation | Hypothesis Testing | Procedures for evaluating whether evidence supports or contradicts specific claims. | Hypotheses tested by comparing measured dose distributions, count rates, voxel intensities, relaxation curves, scatter profiles, and reconstruction outputs with predictions from physics based imaging or dose models. |
| | Replication | The requirement that results be independently reproducible under similar conditions. | Replication occurs via repeated phantom scans, repeated dose measurements, multi session QA testing, verification across independent systems, independent reader analysis for imaging, and cross checking with alternate modalities or detectors. |
| 4.3 Inference & Evaluation | Statistical Inference | Rules for drawing conclusions from noisy or incomplete data. | Methods include noise modeling, regression of calibration curves, uncertainty quantification in dose maps, signal to noise analysis, receiver operating characteristic evaluation, Bayesian reconstruction, and error propagation in dose calculation or imaging reconstruction. |
| | Model Comparison | Criteria (fit, simplicity, predictive accuracy, robustness) used to evaluate competing models. | Models compared on accuracy of dose prediction, imaging fidelity, scatter correction performance, relaxation curve fit quality, transport physics accuracy, and robustness across varied anatomy or device configurations. |
| 4.4 Error Management | Error Analysis | Identification and quantification of random and systematic errors. | Errors arise from detector drift, beam energy instabilities, patient motion, reconstruction artifacts, calibration inaccuracies, electronic noise, scattered radiation, partial volume effects, and misalignment of imaging or treatment systems. |
| | Bias Control | Methods for minimizing subjective, instrumental, or procedural biases. | Bias minimized through blind image review, standardized calibration routines, cross comparison of detectors, randomized phantom orientations, independent dosimetry checks, correction for machine output drift, and automated QA systems. |
| 4.5 Adjudication & Revision | Peer Scrutiny | Collective evaluation of claims through critique, review, and debate. | Findings adjudicated through multi center QA programs, peer review, accreditation audits, cross modality validation, participation in national and international calibration standards, and comparison to consensus physics models. |
| | Theory Revision | Procedures for modifying, replacing, or discarding models based on new evidence. | Theories revised when measured dose, attenuation, relaxation, or scatter behavior deviates from established models, requiring improved tissue models, updated cross section data, new reconstruction algorithms, or revised biological effect models. |
| 4.6 Integrity Conditions | Transparency | Requirements to disclose methods, data, assumptions, and limitations. | Requires full disclosure of calibration procedures, reconstruction assumptions, hardware limitations, beam parameters, phantom geometries, processing pipelines, and uncertainties for all reported measurements. |
| | Ethical Standards | Norms ensuring responsible conduct in experimentation, data handling, and publication. | Requires safe handling of radiation sources, accurate reporting of dose, avoidance of selective data removal, protection of patient data, adherence to regulatory standards, and rigorous compliance with clinical safety protocols. |