TER Radioterapia common mistakes
TER Radioterapia · Understand the traps and how to avoid them.
Mixing up the dose-response curve shapes (linear-quadratic vs. exponential) and confusing α/β values when asked about fractionation sensitivity, e.g., applying a low α/β to a tumour and a high one to a late-responding tissue.
Candidates memorise the LQ formula symbolically without anchoring it to tissue types, so under time pressure they invert which tissue has the low α/β and misapply the concept of fractionation sensitivity.
What to do instead
Build a two-column table (early/tumour vs. late tissue) with α/β values and the clinical consequence of changing dose per fraction; practise BED calculations for both tissue types so the direction of the effect becomes intuitive.
Confusing the roles of the flattening filter, the bending magnet, and the multi-leaf collimator when asked to trace the beam path or diagnose a beam-quality problem in a linac.
Component functions are learned as a list rather than as a sequence, so candidates cannot reason about what happens downstream when one component changes.
What to do instead
Draw the beam path from electron gun to isocentre and label the function and effect of each component; then answer 'what changes if X is removed' questions by walking the diagram forward.
Treating the planning CT slice thickness, index, and reconstruction algorithm as interchangeable with the simulation setup, and selecting a thick slice for a small target or for IGRT matching.
Candidates focus on the scanner brand or the immobilisation device and overlook that spatial accuracy in the planning image set depends on slice thickness and index consistency.
What to do instead
Learn the rule that slice thickness should be no greater than the smallest target dimension divided by a practical factor and that index must be continuous; rehearse which acquisition parameters affect volume delineation versus geometric accuracy.
Describing an SBRT or SRS technique using conventional fractionation language, e.g., quoting a standard 2 Gy/fraction schedule or ignoring the need for abdominal compression, 4D-CT, or motion management.
Candidates default to the familiar conventional fractionation template and do not switch mental models when the question names a stereotactic technique.
What to do instead
Prepare a one-page contrast sheet for conventional vs. hypofractionated vs. stereotactic approaches covering dose per fraction, immobilisation, imaging, and motion management, and explicitly state the technique's requirements in every answer.
Confusing the dose specification and reporting conventions in brachytherapy (point A vs. target volume, prescription at a reference isodose vs. a point) and mixing up source strength units.
Brachytherapy terminology is dense and historically layered, so candidates blend older point-based systems with modern volume-based prescribing and misstate air-kerma strength versus activity.
What to do instead
Create a terminology card distinguishing prescription, reporting, and source-strength quantities with their units; practise reading a brachytherapy plan and stating exactly where and how the dose is specified.
Applying patient-protection principles but forgetting occupational and public dose constraints, or citing the wrong order of magnitude for typical shielding or annual limits.
Candidates memorise the ALARA slogan without the numerical framework, so they cannot distinguish dose limits, constraints, and reference levels or apply them to the correct population.
What to do instead
Memorise a compact table of dose limits by category (occupational, public, lens, extremity) with units, then practise classifying a scenario as a limit, a constraint, or a reference level before answering.
Describing a quality-assurance test without stating its tolerance, frequency, and the person responsible, or confusing daily, monthly, and annual test batteries.
QA is studied as a narrative of 'we check the machine' rather than as a structured schedule with measurable tolerances, so answers stay vague and cannot be scored as correct.
What to do instead
Build a matrix of test, frequency, tolerance, and responsible role for the main linac and imaging subsystems, and answer QA questions by naming all four elements explicitly.
Attributing acute and late radiation toxicities to the wrong time course or tissue, e.g., labelling xerostomia or fibrosis as acute, or managing a late effect with an acute-care pathway.
Candidates group side effects by organ rather than by the early/late biology that determines timing and reversibility, so the timeline and management logic break down.
What to do instead
Sort toxicities into a grid by organ system and by acute versus late, with the underlying mechanism and the appropriate supportive intervention, and rehearse the distinction between reversible acute mucosal reactions and progressive late fibrosis.
Describing target volumes and lymph-node stations from memory without a reproducible anatomical landmark system, so the CTV or elective nodal volume is incomplete or over-inclusive.
Anatomy is reviewed as static images rather than as relationships, so candidates cannot reconstruct boundaries or justify why a station is included.
What to do instead
Practise contouring on cross-sectional images using named landmarks and consensus atlas boundaries, and for each tumour site write the rationale for including or excluding each nodal station.
Answering legal or organisational questions by citing general ethical principles instead of the specific regulatory framework, e.g., confusing informed consent requirements, record retention, or the roles of the radiation protection officer and the medical physics expert.
Candidates treat legislation as background reading and rely on intuition about what 'should' happen rather than on the defined duties and documentation requirements.
What to do instead
Summarise the applicable legal framework as a table of obligation, responsible role, and required documentation, and practise mapping each scenario to the specific duty holder before choosing an answer.