Allied Health & Imaging · Independent exam preparation
診療放射線技師国家試験: Mechanisms, Imaging Decisions, and Safety Study Guide
Study imaging mechanisms, radiation calculations, anatomy, equipment operation, and clinical safety across Japan’s radiological technologist national examination subjects.
By CertMedbry · Updated 31 October 2026
Connect anatomy and disease mechanisms to image formation, equipment choices, dose calculations, and safe examination decisions. This guide develops 60 selected concepts across all 11 examination subjects, supported by original practice questions and flashcards. The official MHLW outline defines the full examination scope. Its intermediate headings extend beyond this selective guide, and its smaller examples do not exhaust the examinable content.
Try 20 free practice questionsWhat is the exam format?
Check the question types, timing and outline before planning your revision.
Which examination and professional level does this guide address?
It addresses 診療放射線技師国家試験, Japan’s National Examination for Radiological Technologists, administered by the Ministry of Health, Labour and Welfare. The official report describes knowledge and skills expected at completion of qualifying education. The association-based catalog label does not identify a separate association examination or an advanced modality credential.
Which blueprint applies, and how should its scope be interpreted?
This guide follows the Reiwa 7 / 2025 outline, applicable beginning with the 2025 examination, the 77th examination. Intermediate headings define the examinable range. Smaller items illustrate those headings and do not limit questions to the listed examples. The official outline supplies the full examination scope; these 60 concepts cover selected material within it.
令和７年版診療放射線国家試験出題基準について · 診療放射線技師国家試験出題基準 令和7年版 · 診療放射線技師国家試験出題基準の利用法
What are the official subject weights?
The approximate allocations are Basic Medical Knowledge 15%; Engineering and Radiation Science 18%; X-ray Equipment 10%; X-ray Imaging Technology 10%; Diagnostic Imaging Examination 10%; Nuclear Medicine Clinical Technology 10%; Radiation Therapy Technology 10%; Image Engineering 3%; Medical Image Informatics 5%; Radiation Safety Management 5%; and Medical Safety Management 4%. This guide contains respectively 9, 11, 6, 6, 6, 6, 6, 1, 4, 3, and 2 concepts. The shorter question and flashcard sets cover every subject without reproducing those proportions exactly.
Which subject boundaries are especially important?
Radiochemistry belongs to Nuclear Medicine Clinical Technology. Radiation biology, radiation physics, medical engineering, and radiation measurement belong to Engineering and Radiation Science. CT equipment belongs to X-ray Equipment, while MRI, ultrasound, and fundus-camera equipment and examinations belong to Diagnostic Imaging Examination. Information-processing foundations, image formation, and image processing belong to Image Engineering; image evaluation, including ROC analysis, belongs to Medical Image Informatics. Use the official correspondence table when older educational chapter names differ from examination-subject names.
How many questions were administered at the latest completed sitting?
As of 31 October 2026, the latest completed sitting was the 78th examination, held on 19 February 2026. Its official answer table lists AM1–AM100 and PM1–PM100, totaling 200 administered questions for the full examination. Scoring exclusions do not change the number administered. The supplied official documents do not establish a separate pretest-item allocation. This learning set contains 20 original questions.
What examination duration and answer arrangements are documented?
The 78th-sitting candidate instructions list two 155-minute sessions for full-subject candidates: 09:30–12:05 and 13:25–16:00, totaling 310 minutes. Subject-exempt candidates had two 75-minute sessions. The instructions refer to paper answer sheets and HB pencils; the official answer table includes both single-answer and multiple-answer entries. Follow each official item’s response instruction. The exercises here use four options and one best answer. Check the applicable sitting’s candidate instructions for its own arrangements.
Where should candidates check dates, fees, eligibility, and licensing requirements?
Use the applicable MHLW examination announcement and official eligibility and results guidance. The published 79th examination notice schedules the examination for 18 February 2027, with applications from 14 December 2026 through 4 January 2027 and an examination fee of 11,400 yen. Foreign qualifications require the specified eligibility recognition. Passing the examination must be followed by the required licensing application and registration before practice as a licensed technologist.
診療放射線技師国家試験の施行｜厚生労働省 · 001640439.pdf · ・診療放射線技師法(◆昭和26年06月11日法律第226号)
Independent preparation for Japan’s national entry-to-practice examination administered by MHLW. The catalog label Japanese Association of Radiological Technologists refers here to that national examination. These educational exercises are independently authored and are not official examination questions.
Outline used: 令和7年版 (Reiwa 7 / 2025) national examination blueprint; the Ministry states it applies from the 2025 examination (the 77th examination). The assigned workbook label is mapped to this Japanese national examination, not to a separate examination named for the Japanese Association of Radiological Technologists.
60 key concepts: understand, apply and avoid the traps
Work through the questions by exam domain. Explain the answer in your own words, try the example, then check the common pitfall.
Basic Medical Knowledge (基礎医学大要)15%
1.How do anatomical planes prevent localization errors?
An axial plane separates superior from inferior regions, a coronal plane separates anterior from posterior regions, and a sagittal plane separates right from left regions. Anatomical directions refer to the patient even when the patient is supine or the display is rotated. Establish the plane, patient orientation, and side markers before identifying a structure. Screen position alone cannot establish anatomical laterality.
Apply it
A reconstruction shows both kidneys and the vertebral body in cross-section. Identify the axial plane, then use orientation markers and anatomical landmarks to describe a lesion relative to the vertebra and the patient’s sides.
Common pitfall: Assuming screen left always means patient right can reverse laterality after rotation or export. Confirm orientation information and anatomical relationships together.
2.Which circulation carries an injected venous tracer to the lungs?
A peripheral venous injection normally travels through systemic veins, the right atrium, the right ventricle, and pulmonary arteries before reaching pulmonary capillaries. Blood returns through pulmonary veins to the left atrium and ventricle, then enters systemic arteries. Arteries are defined by flow away from the heart rather than oxygen content. This sequence explains first-pass tracer distribution and the changing vascular location of an intravenous contrast bolus.
Apply it
After an antecubital injection, predict right-heart activity before pulmonary activity and left-heart activity afterward, assuming normal circulation without a significant shunt or injection problem.
Common pitfall: Classifying vessels by oxygen content misidentifies pulmonary arteries and veins. Follow the direction of blood flow relative to the heart.
3.Why can ventilation and perfusion fail separately?
Ventilation delivers gas to alveoli, whereas perfusion delivers blood through pulmonary capillaries. Effective gas exchange requires both processes and a functioning alveolar-capillary interface. Pulmonary arterial obstruction can reduce perfusion while ventilation remains relatively preserved. Airway obstruction can reduce ventilation despite continuing blood flow. Distinguish the disrupted pathway before interpreting a functional lung pattern or explaining impaired oxygenation.
Apply it
A study shows preserved ventilation in a segment with markedly reduced perfusion. Describe reduced blood delivery relative to air delivery, then assess the distribution and clinical context.
Common pitfall: A ventilation-perfusion mismatch describes physiology rather than establishing a unique diagnosis. Technical quality and underlying lung disease can alter the interpretation.
4.How does portal circulation explain liver enhancement?
The liver receives blood from the hepatic artery and portal vein. Portal blood has already passed through capillary beds in abdominal organs, while hepatic arterial blood arrives through systemic arterial circulation. Contrast enhancement therefore changes as a bolus traverses these pathways. Hepatic veins drain the liver into the inferior vena cava. Distinguishing inflow from outflow explains vascular anatomy and the different appearances of arterial and portal venous acquisitions.
Apply it
Arteries enhance before portal venous structures become conspicuous. Trace contrast through systemic arteries and abdominal capillaries to explain the later portal contribution to liver enhancement.
Common pitfall: The portal vein supplies the liver, while hepatic veins drain it. Confusing these pathways produces incorrect explanations of timing and vascular obstruction.
5.How do filtration and tubular handling determine renal clearance?
Glomerular filtration transfers water and suitable dissolved substances from plasma into the nephron. Tubular reabsorption returns selected substances to blood, while secretion transfers others into tubular fluid. Urinary elimination therefore depends on more than renal blood delivery. A freely filtered substance that is neither reabsorbed nor secreted behaves differently from one substantially secreted by tubules. Renal tracer curves combine delivery, parenchymal handling, and collecting-system drainage.
Apply it
A renal curve rises slowly and clears slowly. Consider reduced delivery or renal function before attributing the delayed curve solely to urinary obstruction.
Common pitfall: Delayed clearance is not specific for obstruction. Tracer properties, hydration, renal function, acquisition quality, and drainage can each influence the measured curve.
診療放射線技師国家試験出題基準 令和7年版 · Dosimetry for Radiopharmaceutical Therapy
6.Which compartments distinguish brain tissue from cerebrospinal fluid spaces?
Brain parenchyma, ventricles, and extra-axial spaces are distinct anatomical compartments. Cerebrospinal fluid occupies the ventricles and subarachnoid space. The dura, arachnoid, and pia define important meningeal relationships. A collection inside brain tissue differs from one between meningeal layers. Identify whether a finding is intra-axial, intraventricular, or extra-axial before considering its cause. Compartment localization also helps explain displacement and obstruction of cerebrospinal-fluid pathways.
Apply it
Ventricles enlarge upstream from a narrowed fluid pathway. Explain the pattern through impaired cerebrospinal-fluid passage and distinguish ventricular expansion from a primary lesion in surrounding brain tissue.
Common pitfall: A fluid-like appearance alone does not establish a normal space. Boundaries, location, mass effect, and sequence characteristics must support that interpretation.
7.What distinguishes invasion from metastatic spread?
Invasion is direct extension of malignant cells into adjacent tissues. Metastasis establishes tumor at a discontinuous site through routes such as lymphatic spread, hematogenous spread, or dissemination across a body cavity. Anatomical continuity helps distinguish these processes. A distant lesion may represent metastasis, another primary tumor, or a benign process. Imaging describes location, extent, and suspicious patterns; the complete diagnostic assessment establishes tumor identity.
Apply it
A pelvic tumor crosses directly into an adjacent organ, while a separate distant lesion is present. Describe local invasion and assess the distant lesion separately for possible metastatic disease.
Common pitfall: Distance alone does not prove metastasis. Inflammation, benign lesions, and another primary malignancy can resemble metastatic disease on an individual examination.
8.Why does inflammatory swelling not prove infection?
Inflammation is a tissue response to injury that can include vascular dilation, increased permeability, and recruitment of inflammatory cells. Increased permeability allows fluid and proteins to leave vessels, contributing to edema. Infection can trigger inflammation, but trauma, ischemia, and immune disease can also do so. Swelling or enhancement identifies a tissue response without independently establishing its cause.
Apply it
Soft-tissue swelling follows an injury without other evidence of infection. Explain edema through the inflammatory vascular response and evaluate distribution, symptoms, and associated findings before assigning a microbial cause.
Common pitfall: Enhancement, edema, or increased tracer uptake alone cannot identify an organism. Inflammation and infection overlap, but they are not equivalent diagnoses.
9.Which prevention level does screening represent?
Primary prevention reduces disease occurrence before disease develops. Secondary prevention seeks earlier detection and intervention, commonly through screening of an appropriate asymptomatic population. Tertiary prevention reduces disability or complications after disease is established. Purpose and population determine the category rather than imaging modality. A screening examination differs from diagnostic imaging prompted by a symptom. Screening assessment also considers false positives, false negatives, and meaningful health outcomes.
Apply it
An asymptomatic person attends an organized program intended to detect disease early. Classify its purpose as secondary prevention and distinguish it from investigation of a new symptom.
Common pitfall: Detecting more abnormalities does not alone demonstrate benefit. Earlier detection must be evaluated alongside downstream consequences and improvements in relevant health outcomes.
Engineering and Radiation Science (理工学・放射線科学)18%
10.How does exponential attenuation describe transmitted photons?
For a monoenergetic narrow beam in uniform material, transmitted intensity follows I = I₀e^(−μx), where μ is the linear attenuation coefficient and x is thickness. Attenuation includes photons removed by absorption and scattering; it is not identical to local energy absorption. The mass attenuation coefficient is μ divided by density. Broad-beam scatter and polychromatic beam hardening complicate direct application of this simple model.
Apply it
For μ = 0.20 cm⁻¹ and x = 5 cm, transmission is e⁻¹, approximately 0.37. The removed fraction is approximately 0.63.
Common pitfall: A removed photon may scatter rather than deposit all its energy locally. Choose attenuation or energy-absorption coefficients according to the quantity being evaluated.
11.Which cues distinguish photoelectric absorption from Compton scattering?
Photoelectric absorption removes the incident photon and ejects a bound electron. Its probability depends strongly on photon energy and atomic composition, with absorption edges at shell-binding energies. Compton interaction transfers part of a photon’s energy to an electron and leaves a scattered photon. These mechanisms influence subject contrast and scatter contamination. Identify whether the scenario involves complete photon removal, a changed photon direction, or strong material dependence.
Apply it
A photon leaves the patient with reduced energy and a changed direction. Identify Compton scattering and explain why accepting it can misrepresent its original path.
Common pitfall: Scattering does more than reduce intensity. A detected scattered photon can degrade spatial information because its recorded direction no longer identifies its original trajectory.
12.How does half-value layer describe beam penetration?
Half-value layer is the thickness of a specified material that reduces a beam quantity to half under defined conditions. For a monoenergetic narrow beam, HVL = ln(2)/μ. Equal successive half-value layers then produce repeated halving. A diagnostic spectrum is polychromatic: preferential removal of lower-energy photons hardens the beam, so successive half-value layers need not be equal. Compare values only with attention to attenuator and measurement geometry.
Apply it
A monoenergetic beam with a 2-mm half-value layer crosses 6 mm of the same material. Three equal half-value layers leave one-eighth of the original intensity.
Common pitfall: Repeated identical halving is not automatically valid for a polychromatic diagnostic beam. Beam hardening changes the spectrum as attenuation proceeds.
NIST: X-Ray Mass Attenuation Coefficients—Section 2 · 診療放射線技師国家試験出題基準 令和7年版
13.Which radiation quantity matches the reported unit?
Activity describes nuclear transformations per second and is expressed in becquerels. Absorbed dose describes energy imparted per unit mass and is expressed in grays, equivalent to joules per kilogram. Protection quantities expressed in sieverts incorporate radiation or tissue weighting according to their definitions. These quantities describe source strength, deposited energy, and protection-related assessment respectively. Interpret a number only after identifying its quantity, unit, target, and relevant conditions.
Apply it
Depositing 0.006 J in 0.003 kg gives an absorbed dose of 2 Gy. The information does not independently establish activity or effective dose.
Common pitfall: Equal numerical values in grays and sieverts do not make their meanings interchangeable. The definition, weighting, and tissue distribution determine the appropriate quantity.
14.How does water radiolysis cause indirect DNA injury?
Radiation can damage DNA directly through energy deposition in the molecule or indirectly through reactive products formed when surrounding water is irradiated. Free radicals can react with DNA and contribute to lesions, including strand breaks. Outcome depends on damage complexity, repair, and cellular context. The distinction identifies where the initiating interaction occurs; indirect injury can still be biologically serious and can contribute to loss of reproductive capacity.
Apply it
Reducing available reactive radicals decreases injury in an irradiation experiment. Relate the change to an indirect pathway while recognizing that direct DNA interactions can still occur.
Common pitfall: Visible cellular integrity does not prove continued reproductive survival. Conversely, some DNA lesions can be repaired without causing immediate or eventual cell death.
Radiation Biology: A Handbook for Teachers and Students—Section 3 · Pub1196_web.pdf
15.How do tissue reactions differ from stochastic effects?
Tissue reactions occur when injury to enough cells compromises tissue function. They generally show threshold-like behavior, with severity increasing as dose rises above the relevant range. For stochastic effects, protection models emphasize increasing probability with dose rather than increasing severity of an established cancer. Tissue, dose distribution, and exposure timing affect the response. Distinguish functional tissue injury from a later probabilistic risk before interpreting a dose scenario.
Apply it
Compare a localized skin reaction with modeled future cancer probability. The skin endpoint concerns tissue damage and severity, while the cancer model concerns the likelihood of occurrence.
Common pitfall: A low probability of a stochastic effect does not mean a mild resulting disease. Probability and severity describe different endpoints.
16.Why can reoxygenation increase sensitivity between fractions?
Oxygen can increase the biological effectiveness of low-LET radiation by helping fix radiation-induced chemical damage. Hypoxic tumor cells may therefore be relatively resistant. Between fractions, changes in perfusion, oxygen consumption, and tumor structure can improve oxygenation of surviving cells. Reoxygenation differs from repair of sublethal injury, redistribution through the cell cycle, and repopulation. Each process changes treatment response through a different biological mechanism.
Apply it
A previously hypoxic region becomes better oxygenated before another fraction. Predict increased sensitivity to later low-LET irradiation and identify reoxygenation as the relevant change.
Common pitfall: Repair concerns recovery from existing injury; reoxygenation changes sensitivity to subsequent irradiation. Their shared timing between fractions does not make them interchangeable.
Radiation Biology: A Handbook for Teachers and Students—Section 3
17.How do counting statistics determine measurement precision?
For independent counts described by a Poisson model, the standard deviation of a count total N is approximately √N and relative statistical uncertainty is approximately 1/√N. Collecting four times as many counts halves relative uncertainty. Longer acquisition improves counting precision when rate and conditions remain stable. It does not remove calibration bias, motion, contamination, or an incorrect background model. Distinguish random variation from systematic error before selecting a remedy.
Apply it
A measurement containing 2,500 counts has approximately 2% relative counting uncertainty. Reaching approximately 1% requires 10,000 counts and about four times the time at unchanged rate.
Common pitfall: More counts can make a biased result more precise. Improved repeatability does not establish that the measurement is accurate.
診療放射線技師国家試験出題基準 令和7年版 · Dosimetry for Radiopharmaceutical Therapy
18.Why does a dosimeter require calibration and corrections?
A detector signal is related to radiation interaction but is not automatically the desired physical quantity. Calibration connects response to a reference quantity under specified conditions. Corrections address relevant differences between calibration and use. For a vented ionization chamber, temperature and pressure affect the gas density and therefore the reading. Identify the detector, calibration quantity, beam conditions, and applicable corrections before reporting dose.
Apply it
A chamber gives different readings on two days despite apparently stable irradiation. Compare temperature-pressure-corrected readings before concluding that output changed.
Common pitfall: A stable display does not establish correct dosimetry. An inappropriate calibration coefficient or omitted correction can create systematic error even when repeated measurements agree closely.
19.How do voltage, resistance, and power describe a circuit?
For an ohmic resistor, current follows I = V/R and dissipated power follows P = VI = V²/R. At fixed resistance, doubling voltage doubles current and quadruples power. These relations apply to the defined element and assumptions; a complete medical device need not behave as an ideal resistor. Identify what remains constant and preserve units before calculating. Electrical power and patient radiation dose describe different quantities.
Apply it
A 20-ohm resistor supplied with 10 V carries 0.5 A and dissipates 5 W. Doubling voltage produces 1 A and 20 W if resistance remains unchanged.
Common pitfall: Do not assume both voltage and current remain fixed after changing the circuit. Determine the circuit’s actual constraints before applying a power formula.
20.How do sampling and quantization affect an electronic signal?
Sampling measures a signal at discrete times; quantization assigns measured amplitude to a finite digital level. A higher sampling rate can represent faster changes, while greater bit depth provides more amplitude levels across a selected range. These address different limitations. If input exceeds the converter’s range, peaks clip. Additional bit depth cannot recover the clipped information. Match temporal bandwidth, amplitude range, and precision to the signal.
Apply it
Flat-topped detector-waveform peaks persist after bit depth increases. Check input range and gain because saturation, rather than coarse quantization, may be responsible.
Common pitfall: Temporal aliasing, quantization error, and clipping are separate failures. Improving one specification does not automatically correct limitations elsewhere in the acquisition chain.
X-ray Equipment (エックス線撮影機器学)10%
21.How do tube voltage and mAs change X-ray production?
Tube voltage sets the maximum kinetic energy of electrons accelerated toward the target and therefore the maximum bremsstrahlung photon energy. Tube current multiplied by exposure time gives mAs, which primarily controls photon quantity at otherwise fixed conditions. Voltage also affects spectrum and output, so it cannot be treated only as a penetration setting. Separate photon quantity from energy distribution when predicting exposure, contrast, and equipment loading.
Apply it
At unchanged voltage, filtration, and geometry, doubling mAs approximately doubles photon output within the linear operating range. Maximum photon energy remains unchanged.
Common pitfall: Doubling mAs does not double photon energy. Changing voltage also changes output, so comparisons involving voltage require more than a simple quantity adjustment.
22.Why does focal-spot selection involve a heat tradeoff?
A smaller effective focal spot reduces geometric unsharpness, especially when object-to-detector distance is substantial. Concentrating electron energy on a smaller target area also restricts permissible loading. A larger focal spot supports greater loading but produces more geometric blur under otherwise identical conditions. A rotating anode distributes heat over a focal track without eliminating thermal limits. Select focus together with current, exposure time, geometry, and motion risk.
Apply it
A magnification examination requires fine detail, but the proposed current exceeds small-focus limits. Reconsider the permitted technique and achievable exposure time before selecting the focal spot.
Common pitfall: Small focus cannot correct patient movement. Rotating-anode construction also does not permit unlimited instantaneous or cumulative heat input.
23.Why does filtration change the X-ray spectrum?
Filtration preferentially removes lower-energy photons because attenuation depends on photon energy. At unchanged tube settings, transmitted fluence decreases while average energy generally rises. This spectral change is beam hardening. Lower-energy photons can contribute superficial absorption without useful transmitted signal. Evaluate filtration together with receptor exposure and any technique compensation. A filter changes the proportions of photon energies rather than increasing the energy of individual transmitted photons.
Apply it
Added filtration lowers measured output while increasing half-value layer. Explain both through preferential removal of lower-energy photons rather than increased maximum photon energy.
Common pitfall: Greater penetration does not mean the filter accelerated photons. The tube voltage still determines the maximum energy available in the emitted spectrum.
NIST: X-Ray Mass Attenuation Coefficients—Section 2 · 診療放射線技師国家試験出題基準 令和7年版
24.When does a grid improve contrast at an exposure cost?
An antiscatter grid preferentially absorbs obliquely traveling radiation before it reaches the receptor. This can improve contrast when scatter is substantial. Some primary photons are also absorbed, so maintaining receptor exposure can require increased output. Centering, orientation, focal distance, and alignment affect transmission. Select grid use according to the anticipated scatter benefit and exposure cost. The grid cannot correct movement or remove scatter already recorded by the detector.
Apply it
Peripheral exposure loss appears after a focused grid is introduced. Check source distance and alignment before compensating with increased mAs.
Common pitfall: Increasing exposure may alter brightness without correcting grid cutoff. An unresolved alignment error can therefore persist while patient exposure unnecessarily increases.
25.How can automatic exposure control be misled?
Automatic exposure control terminates exposure when the selected sensing region reaches a target signal. Correct chamber selection, positioning, collimation, and calibration are essential. Dense material covering the active region can delay termination, while an uncovered region receiving direct radiation can terminate exposure too early. The controller responds to a signal rather than independently judging diagnostic adequacy. Determine what covers the selected region before predicting the error.
Apply it
An implant overlies the active chamber. Predict reduced transmission, delayed termination, and potentially excessive exposure to surrounding anatomy; review chamber selection and positioning.
Common pitfall: Automatic operation does not guarantee an optimal image. A correctly functioning generator can still deliver an inappropriate exposure when chamber coverage is wrong.
26.How does CT reconstruct a cross-section from projections?
CT records transmitted X-rays from many angular directions and reconstructs cross-sectional information from those measurements. Source, detectors, geometry control, and reconstruction processing work together to estimate spatial attenuation. The scanner does not directly photograph an isolated physical slice. Inconsistent projections caused by movement, metal, or inadequate sampling can produce structured artifacts. Distinguish measurement acquisition from image reconstruction when deciding whether different processing can address a problem.
Apply it
Two reconstructions from the same projection data show different noise and edges. Attribute the difference to reconstruction choices before assuming two acquisitions occurred.
Common pitfall: A new series does not necessarily represent additional radiation exposure. Establish whether new projection data were collected before evaluating repeat exposure or acquisition necessity.
X-ray Imaging Technology (エックス線撮影技術学)10%
27.How does projection geometry control magnification and blur?
Magnification is M = SID/SOD, where SID is source-to-image distance and SOD is source-to-object distance. At fixed SID, increasing object-to-detector separation increases magnification. Geometric unsharpness also increases with focal-spot size and object-to-detector distance and decreases with source-to-object distance. Keeping anatomy close to the detector generally reduces enlargement and geometric blur. Motion, detector sampling, and processing impose additional limitations.
Apply it
With SOD = 90 cm and SID = 120 cm, magnification is 1.33. A 30-mm object projects to approximately 40 mm.
Common pitfall: A projected measurement is not automatically anatomical size. A calibration marker at a different depth experiences different magnification and can produce misleading measurements.
28.When does shortening exposure time reduce motion blur?
Motion blur reflects displacement while information is collected. Shortening exposure time reduces displacement when movement speed is unchanged. Preserving mAs while shortening time requires increased tube current, within generator and focal-spot limits. Immobilization, breathing instructions, and suitable positioning can also reduce movement. Distinguish motion blur from geometric or detector limitations because sharpening cannot reliably restore information lost during exposure.
Apply it
A permitted technique halves exposure time and doubles current at unchanged voltage. It preserves mAs while reducing the opportunity for respiratory movement.
Common pitfall: Higher current may exceed loading limits or require a larger focal spot. Reduced movement does not guarantee improved total resolution when another source of blur increases.
29.Which chest-image cues reveal projection and rotation?
Chest radiographs combine anatomical appearance with projection geometry. An anteroposterior acquisition can magnify the heart more than a standard posteroanterior acquisition because of heart-to-detector separation and source geometry. Unequal distances from the medial clavicular ends to spinous processes suggest rotation, with anatomical variation considered. Assess projection, rotation, inspiration, and coverage before interpreting apparent cardiomediastinal enlargement or comparing silhouette measurements.
Apply it
A portable anteroposterior image shows a larger heart silhouette than an earlier upright posteroanterior image. Compare geometry and inspiration before inferring definite interval enlargement.
Common pitfall: Technical limitations can mimic disease but do not exclude disease. Describe the limitations while evaluating remaining findings and clinical context.
30.Why does mammographic compression improve image formation?
Compression reduces breast thickness, spreads overlapping tissue, limits movement, and brings structures closer to the receptor. Reduced thickness can decrease scatter and the exposure needed for a suitable image. Compression changes tissue geometry, so positioning and inclusion remain separate requirements. Evaluate coverage, folds, contact, and motion rather than using compression force alone as an adequacy criterion. The objective is reproducible visualization of the required tissue.
Apply it
Improved compression reduces movement, but posterior tissue remains excluded. Recognize the quality improvement while identifying the remaining positioning problem.
Common pitfall: A sharp, well-exposed image can still be inadequate if required anatomy is missing. Compression cannot substitute for complete tissue inclusion and appropriate positioning.
31.How should contrast timing follow the diagnostic target?
Contrast-enhanced CT changes as a bolus traverses arteries, tissue microcirculation, veins, and excretory pathways. The desired phase depends on the clinical target. Injection characteristics and patient circulation affect timing, so an identical delay does not guarantee identical enhancement in every patient. Evaluate the observed vascular and organ pattern before interpreting poorly enhanced anatomy. A phase mismatch can prevent the acquisition from answering the intended diagnostic question.
Apply it
An arterial examination shows strong venous enhancement and poor arterial opacification. Investigate timing and injection performance before declaring an artery occluded.
Common pitfall: Poor opacification is not proof of vascular obstruction. Circulation, delivery, timing, and acquisition factors must be distinguished from genuine absent flow.
32.How do CT artifacts guide acquisition and reconstruction decisions?
CT artifacts occur when measurements or reconstruction assumptions do not consistently represent the object. Motion causes projection inconsistencies; highly attenuating material can cause photon starvation and beam hardening; finite voxel size produces partial-volume averaging. Identify the mechanism before selecting a remedy. Existing data may support improved reconstruction, while missing or inconsistent acquisition information may remain limiting. A repeat acquisition needs a defined diagnostic benefit.
Apply it
A small dense structure becomes clearer on thinner sections reconstructed from the same acquisition. Explain reduced partial-volume averaging without assuming another exposure occurred.
Common pitfall: Thinner sections can improve structural separation while increasing noise. Better appearance in one respect does not establish superior overall diagnostic performance or justify repetition.
Diagnostic Imaging Examination (診療画像検査学)10%
33.How do T1 and T2 relaxation create MR contrast?
T1 describes recovery of longitudinal magnetization, while T2 describes loss of transverse coherence. Sequence timing determines how strongly each process influences signal. Conventional spin-echo reasoning associates relatively short TR and TE with T1 weighting and long TR and TE with T2 weighting. Proton density and other sequence properties also affect brightness. Identify acquisition conditions before using signal as a tissue clue.
Apply it
Fluid appears bright on one sequence and dark on another. Compare weighting and timing before interpreting this as a change in the tissue itself.
Common pitfall: Brightness has no fixed meaning across all sequences. Fat suppression, inversion recovery, contrast administration, and specialized acquisition methods can alter expected signal patterns.
34.Why should diffusion-weighted signal be checked against ADC?
Diffusion-sensitizing gradients cause moving water spins to lose coherence and signal. In a simplified model, S(b) = S(0)e^(−b·ADC), with baseline signal retaining T2 influence. High diffusion-weighted signal accompanied by reduced ADC supports restricted diffusion. High signal without reduced ADC can reflect T2 shine-through. Compare the paired information before identifying restriction, then use anatomy, timing, and other sequences to interpret its cause.
Apply it
A lesion is bright on diffusion-weighted images without corresponding ADC reduction. Explain why brightness alone does not establish true restricted diffusion.
Common pitfall: Reduced ADC supports restriction but is not a unique diagnosis. Several pathological processes can overlap and require anatomical and clinical discrimination.
35.When can an MR Conditional implant be scanned?
MR Conditional means an item has demonstrated safety under specified conditions. These may include field strength, spatial gradient, radiofrequency exposure, coils, device configuration, and scan duration. Identify the exact implant and compare every applicable condition with the actual examination. Prior uneventful scanning does not establish safety in another configuration. Unidentified devices or unmet conditions require resolution through the responsible MR safety process before scanning.
Apply it
An implant’s labeling permits specified scanner and radiofrequency conditions. Verify protocol compliance for the actual device configuration before proceeding.
Common pitfall: MR Conditional is not unrestricted permission. A familiar product family or a previous successful scan does not replace exact identification and condition checking.
36.How does echo travel time determine ultrasound depth?
Pulse-echo ultrasound estimates depth from the interval between transmission and reception. Because sound travels to a reflector and returns, depth is d = ct/2 using assumed propagation speed c. The transducer converts electrical energy to sound and returning echoes to electrical signals. Tissue boundaries with differing acoustic properties generate reflections. Incorrect speed assumptions or unusual paths can misplace structures, so displayed depth depends on a physical model.
Apply it
At 1,540 m/s, an echo returning after 100 microseconds represents a depth of 0.077 m, or 7.7 cm.
Common pitfall: Using d = ct doubles depth by treating round-trip time as one-way time. Convert microseconds correctly before substituting values into the equation.
Ultrasound | National Institute of Biomedical Imaging and Bioengineering · 診療放射線技師国家試験出題基準 令和7年版
37.Which ultrasound tradeoff links frequency and penetration?
Higher-frequency ultrasound generally supports finer detail but attenuates more rapidly in tissue, limiting penetration. Lower frequencies are useful for deeper targets, while higher frequencies often suit superficial anatomy. Acoustic behavior also produces clues: strong attenuation can cause posterior shadowing, and relatively low attenuation through fluid can cause posterior enhancement. Select frequency according to target depth and interpret artifacts through the actual sound pathway.
Apply it
A superficial thyroid target is poorly resolved with a deep-abdominal probe. Consider a higher-frequency probe while recognizing its limitations for deeper structures.
Common pitfall: Gain amplifies received signals and noise rather than restoring sound lost through attenuation. Higher gain cannot reliably recover information that never reached the receiver.
Ultrasound | National Institute of Biomedical Imaging and Bioengineering · 診療放射線技師国家試験出題基準 令和7年版
38.Which landmarks establish fundus-image orientation and coverage?
The optic disc lies nasal to the macula: nasal means toward the nose and temporal means toward the temple. Retinal vessels emerge from the disc, while the macular region lies temporally. Establish the eye’s laterality and any rotation or mirroring before translating these relationships into screen directions. Focus, illumination, fixation, and coverage must support assessment of the requested field; a recognizable landmark does not guarantee adequate examination coverage.
Apply it
A finding lies beyond the macula in the direction away from the nasally located disc. Describe it as temporal after confirming image orientation and eye identity.
Common pitfall: Screen position alone cannot establish laterality. A sharply imaged disc does not make a photograph adequate when the requested macular region is excluded.
Nuclear Medicine Clinical Technology (核医学診療技術学)10%
39.How do physical and biological half-lives combine?
Physical half-life describes radioactive decay, while biological half-life describes removal from a specified biological compartment. For independent monoexponential processes, rates add: 1/Tₑ = 1/Tₚ + 1/Tᵦ. Effective half-life is shorter than either finite component. Real biodistribution can involve uptake and several clearance phases, so a single effective half-life describes a particular model and compartment. Distinguish retained tissue activity from decay in a sealed vial.
Apply it
A physical half-life of 6 hours and biological half-life of 12 hours give an effective half-life of 4 hours.
Common pitfall: Add removal rates rather than half-life durations. A simple exponential may be inappropriate when continuing uptake or multiple compartments dominate the observed activity curve.
Dosimetry for Radiopharmaceutical Therapy · 診療放射線技師国家試験出題基準 令和7年版
40.Which purity test identifies an incorrectly labeled chemical form?
Radionuclidic purity concerns activity attributable to the intended radionuclide. Radiochemical purity concerns activity present in the intended chemical form. Chemical purity addresses nonradioactive contaminants. A preparation can contain the correct radionuclide in an unwanted chemical species with different biodistribution. Chromatography separates species through migration or retention differences. Match the defect to the correct attribute rather than treating expected photon energy as proof of a correctly labeled product.
Apply it
Energy analysis identifies the expected radionuclide, but chromatography shows substantial unwanted activity fractions. Identify a radiochemical-purity failure.
Common pitfall: Activity measurement establishes neither labeling quality nor sterility. Separate quality attributes require their own appropriate tests and preparation-specific acceptance criteria.
診療放射線技師国家試験出題基準 令和7年版 · Dosimetry for Radiopharmaceutical Therapy
41.Why does gamma-camera collimation trade sensitivity for resolution?
A conventional gamma-camera collimator admits photons traveling in allowed directions, linking detected events to their approximate origins. Most emitted photons are rejected, limiting sensitivity. Hole geometry and septal design affect resolution, sensitivity, and suitability for photon energy. With parallel-hole collimation, increasing source-to-collimator distance generally worsens spatial resolution. Keeping the detector close can improve detail while preserving safe clearance and movement.
Apply it
Two otherwise comparable planar acquisitions differ in detector distance. Predict poorer detail in the more distant image even if display magnification is increased afterward.
Common pitfall: Display sharpening cannot restore information lost through collimator geometry. A visually sharper presentation does not establish better physical resolution or more accurate localization.
42.How do attenuation and scatter corrections affect SPECT interpretation?
SPECT reconstructs tracer distribution from projections acquired around the patient. Attenuation removes emitted photons before detection, while scatter changes direction and contaminates accepted events. Corrections model these effects rather than generating new measured photons. Accuracy depends on calibration, assumptions, and registration of any attenuation map. Unexpected patterns should be assessed alongside uncorrected information, especially when movement could misalign emission and anatomical data.
Apply it
A defect appears after attenuation correction, and the attenuation map is misregistered. Investigate alignment before interpreting the defect as reduced tracer uptake.
Common pitfall: Correction does not guarantee improved accuracy everywhere. Misregistration and incorrect models can introduce artifacts that resemble real physiological or pathological differences.
Dosimetry for Radiopharmaceutical Therapy · 診療放射線技師国家試験出題基準 令和7年版
43.How does PET coincidence detection define a line of response?
A positron loses kinetic energy and annihilates with an electron, commonly producing two approximately opposing 511-keV photons. Paired detection within a coincidence window defines a line of response between detectors. Recorded events include true, scattered, and random coincidences. Positron travel and imperfect photon opposition limit correspondence between the original decay location and reconstructed event. Coincidence acceptance therefore supports statistical localization without proving an exact decay position.
Apply it
Unrelated photons arrive within the timing window and are accepted as a pair. Identify a random coincidence rather than a scattered true pair.
Common pitfall: Timing agreement alone does not prove common origin. Random and scattered coincidences can satisfy acceptance conditions while assigning activity to an incorrect response line.
Dosimetry for Radiopharmaceutical Therapy · 診療放射線技師国家試験出題基準 令和7年版
44.Why does radiopharmaceutical therapy require time-integrated activity?
Absorbed dose depends on energy deposited in a target. Estimation requires activity present over time, not simply the amount administered. Integrating a source region’s activity estimates its number of nuclear transformations. Dose calculation then accounts for emissions and energy transfer to target regions, including relevant geometry and mass. Uptake, retention, clearance, and anatomy differ between patients, so equal administered activities need not produce equal organ doses.
Apply it
Two patients receive equal activity, but one retains it longer in an organ. With other factors comparable, predict greater time-integrated activity and potentially greater organ dose.
Common pitfall: One uptake image cannot independently define a complete time-activity curve. Temporal sampling, quantification, target mass, and modeling uncertainty remain important.
Radiation Therapy Technology (放射線治療技術学)10%
45.How do linac photon and electron beams differ in depth dose?
A medical linear accelerator accelerates electrons. These can be used for treatment or directed onto a target to produce bremsstrahlung photons. Megavoltage photon beams exhibit buildup before dose decreases with depth. Electron beams have a more limited useful range and a relatively rapid distal falloff. Selection depends on target depth, shape, surrounding anatomy, prescription, and commissioned beam measurements rather than surface appearance alone.
Apply it
For a superficial target with deeper tissue requiring sparing, explain why electron depth-dose behavior may be useful while considering the complete planned distribution.
Common pitfall: Limited electron range does not mean zero distal dose. Scattering and bremsstrahlung contamination remain relevant when evaluating target coverage and deeper tissue exposure.
46.Why are gross, clinical, and planning target volumes different?
Gross tumor volume represents demonstrable tumor. Clinical target volume includes demonstrable disease and/or tissue considered at risk of microscopic disease requiring treatment. Planning target volume incorporates geometrical considerations needed to support treatment of the clinical target despite relevant uncertainties. These volumes address visible disease, biological extent, and delivery uncertainty. Better image guidance can reduce some geometrical uncertainty without removing the biological rationale for microscopic coverage.
Apply it
Improved daily setup verification supports discussion of a smaller planning margin. Explain why changing clinical target coverage requires a separate judgment about disease extent.
Common pitfall: Microscopic-disease and setup margins address different problems. Reducing one because another process improved may leave the original biological uncertainty unaddressed.
47.How does reference dosimetry convert a chamber reading into dose?
An absorbed-dose-to-water formalism relates corrected reading M_Q to dose using D_w,Q = M_Q × N_D,w,Q0 × k_Q,Q0. The calibration coefficient applies at reference quality Q0, while the quality correction accounts for the clinical beam. Applicable reading corrections include temperature-pressure effects for vented chambers, recombination, polarity, and electrometer calibration. Phantom, field, depth, distance, and detector position must satisfy the adopted reference conditions.
Apply it
A stable reading is obtained at the wrong reference depth. Correct the measurement geometry before accepting the calculated dose.
Common pitfall: Reproducibility is not traceable accuracy. Measurements can agree closely while an incorrect depth, calibration quantity, or correction produces a systematic dose error.
48.What does a cumulative dose-volume histogram reveal?
A cumulative dose-volume histogram reports the volume or fraction receiving at least each dose. It summarizes target coverage and organ exposure while discarding spatial location. Similar histograms can therefore accompany different hotspot positions. Interpret histograms with contours, spatial dose maps, and relevant tissue responses. A limited high-dose segment can be important in a serial structure, while parallel-organ function often depends strongly on affected volume.
Apply it
Two target histograms look similar, but one plan places a hotspot near a critical structure. Examine anatomical dose overlays before judging the plans equivalent.
Common pitfall: A favorable summary value can conceal geographic miss or an important local hotspot. Correct contours and anatomical review remain essential to meaningful histogram interpretation.
49.How does image guidance differ from respiratory motion management?
Image guidance checks anatomy relative to the treatment plan and supports setup correction. Respiratory motion management addresses movement through methods such as gating, breath hold, tracking, or motion-inclusive planning. A correct initial position does not ensure that the target remains there during irradiation. Distinguish changes between fractions from movement within a fraction, then identify which uncertainty the chosen method actually reduces.
Apply it
Pretreatment imaging confirms lung-target position, but breathing causes substantial movement. Implement the planned motion strategy because setup verification alone does not control that displacement.
Common pitfall: A precise couch adjustment cannot eliminate internal motion continuing afterward. External alignment and internal target behavior require related but distinct assessments during delivery.
50.Why can equal total doses have different biological effects?
Biological effect depends on fraction size, fraction number, tissue response, and treatment timing. The simplified linear-quadratic expression BED = nd[1 + d/(α/β)] uses n equal fractions of d Gy and an endpoint-specific α/β ratio. It assumes complete repair of sublethal damage between fractions and omits time-dependent repopulation. A lower α/β indicates greater sensitivity to fraction size. If fractions are delivered before sufficient repair occurs, residual damage can interact with damage from the next fraction, increasing biological effect beyond this calculation.
Apply it
At α/β = 3 Gy, 30 fractions of 2 Gy give BED = 60[1 + 2/3] = 100 Gy, while 20 fractions of 3 Gy give BED = 60[1 + 3/3] = 120 Gy despite identical 60-Gy physical totals. These comparisons assume complete repair between fractions and no repopulation correction.
Common pitfall: Short interfraction intervals can invalidate the complete-repair assumption. Conversely, prolonging treatment can permit surviving tumor clonogens to repopulate, reducing tumor effect without changing this simplified BED value. Comparisons involving these timing differences require appropriate repair or repopulation corrections. BED does not independently establish a prescription or replace clinical evidence and organ dose constraints.
Pub1196_web.pdf · Radiation Biology: A Handbook for Teachers and Students—Section 3 · 診療放射線技師国家試験出題基準 令和7年版
Image Engineering (画像工学)3%
51.How does pixel spacing limit spatial sampling?
Spatial sampling records an image on a discrete grid. For interval Δx, the Nyquist frequency is 1/(2Δx), defining the ideal sampling boundary for appropriately band-limited information. Smaller pixels raise that boundary but do not guarantee improved system resolution. Detector response, focal spot, motion, and reconstruction also matter. Interpolation creates additional displayed samples without recovering spatial frequencies that were never adequately recorded.
Apply it
Pixel spacing of 0.20 mm gives a Nyquist frequency of 2.5 cycles/mm. Resampling to 0.10-mm display pixels does not demonstrate acquired resolution of 5 cycles/mm.
Common pitfall: Matrix size alone cannot establish pixel spacing without field of view. Sampling limits and measured resolution describe related but different properties.
Medical Image Informatics (医療画像情報学)5%
52.Why should image quality be judged for a detection task?
Image quality includes contrast, spatial resolution, noise, and the diagnostic task. Sharpening can increase edge conspicuity while amplifying noise; smoothing can reduce noise while obscuring small details. ROC analysis plots sensitivity against false-positive fraction across decision thresholds. It evaluates discrimination rather than visual preference. Compare methods using relevant lesion size, contrast, viewing conditions, and the clinical decision instead of relying on apparent sharpness alone.
Apply it
A sharpened reconstruction looks impressive at bone edges but worsens subtle low-contrast detection. Select processing according to the required detection task.
Common pitfall: Lower noise or stronger edges alone do not demonstrate superior performance. Processing changes can affect sensitivity and false positives in different directions.
53.How do DICOM pixel attributes define an image array?
DICOM attributes describe how pixel samples must be interpreted. Rows and Columns define array dimensions. Samples per Pixel and Photometric Interpretation describe sample organization and meaning. Bits Allocated, Bits Stored, High Bit, and Pixel Representation describe storage and numerical interpretation. A receiving system must decode Pixel Data consistently with these attributes. A plausible display does not prove correct interpretation, especially for signed samples or monochrome polarity.
Apply it
Transferred images have abnormal numerical values despite intact data. Compare Bits Stored and Pixel Representation with decoder assumptions before blaming image acquisition.
Common pitfall: Bits Allocated need not equal Bits Stored. Storage bytes alone cannot establish meaningful precision, numerical range, or whether values require signed interpretation.
54.How do RIS and PACS support different imaging functions?
A radiology information system supports examination workflow and related information, while a picture archiving and communication system manages imaging objects and their availability. Identifiers, orders, and examination status connect these functions. A technically valid image can still be associated with the wrong patient or request. Successful transport therefore differs from correct clinical association. Verify identifiers and examination context throughout the relationship between patient, order, acquisition, and archive.
Apply it
Images reach the archive but appear under an unrelated order. Investigate identifier reconciliation and workflow association before considering repeat imaging.
Common pitfall: An archive receipt confirms a transport event rather than complete patient matching or universal clinical availability. Workflow integrity requires checks beyond successful transfer.
55.Why do confidentiality, integrity, and availability need different controls?
Confidentiality limits access to authorized users. Integrity protects against inappropriate alteration. Availability keeps needed information accessible. Authentication identifies a user, authorization determines permitted actions, and audit records support accountability. Backup supports recoverability but does not independently prevent unauthorized access or incorrect changes. In imaging, accurate identifiers, images, and reports must be preserved alongside privacy and dependable clinical access.
Apply it
A department can restore images after equipment failure but cannot attribute record changes. Recognize backup’s recovery role and the separate need for individual accounts, permissions, and audit records.
Common pitfall: Shared accounts weaken attribution even with strong passwords. Encryption, backups, access controls, and auditing address different failures and cannot substitute completely for one another.
Radiation Safety Management (放射線安全管理学)5%
56.Which legal and protection decisions must precede irradiation?
Article 26 of Japan’s Radiological Technologists Act requires specific physician or dentist instructions before a technologist irradiates a person. Clarify ambiguous requests before irradiation. Article 24-2 also requires specific instructions for the designated related assistance acts. Justification evaluates expected benefit against radiation detriment, while optimization selects exposure appropriate to the purpose. Diagnostic reference levels support review of typical practice rather than acting as individual patient dose limits.
Apply it
A patient requests an additional radiograph outside the existing instructions. Clarify with the responsible physician before exposure, then apply appropriate identification and technique checks.
Common pitfall: Consent and a routine protocol do not replace legally required instructions. Having instructions also does not remove the need for justified, correctly identified, safely optimized care.
・診療放射線技師法(◆昭和26年06月11日法律第226号) · 診療放射線技師国家試験出題基準 令和7年版 · IAEA-TECDOC-1608
57.How do time, distance, and shielding reduce external exposure?
Reduce external exposure by limiting time near a source, increasing distance, and placing appropriate shielding in the radiation path. For an approximately isotropic point source in free space, intensity varies inversely with distance squared. Doubling distance reduces intensity to one-quarter. Extended sources, scattering, and intervening material can change this relationship. Shielding selection depends on radiation type, energy, material, and actual exposure geometry.
Apply it
A point-like source gives 80 microSv/h at 1 m. At 2 m, estimate 20 microSv/h; 15 minutes there gives approximately 5 microSv under unchanged conditions.
Common pitfall: Inverse-square estimates are not universally exact near large sources or in scatter-dominated fields. Check geometry before using the point-source approximation.
58.How does contamination differ from external irradiation?
External irradiation means radiation reaches a person from an outside source. Contamination means radioactive material is present where unwanted, including skin, surfaces, or inside the body. Irradiation can occur without contamination. Contamination can spread and produce external or internal exposure. Identify material, location, emissions, and possible intake routes before selecting measurements. An instrument suitable for dose-rate assessment may not adequately detect a particular contamination problem.
Apply it
Activity is detected on a glove after an unsealed-source spill. Isolate the item, limit spread, and assess the affected area using a suitable contamination detector.
Common pitfall: A normal external dose reading does not exclude contamination or intake. Radiation type, detector sensitivity, geometry, and measurement purpose determine what the result establishes.
Medical Safety Management (医療安全管理学)4%
59.How do identity checks and standard precautions support safe assistance?
Before imaging or injection, match at least two reliable identifiers to the request and record. Resolve discrepancies before proceeding; room number is insufficient. Standard precautions apply to every patient and include hand hygiene, aseptic technique, exposure-appropriate protective equipment, and single-patient use of needles and syringes. Changing the needle does not make a used syringe suitable for another patient. Gloves do not replace hand hygiene.
Apply it
A stated birth date conflicts with the open record. Pause and reconcile identity. If a previously used syringe is then proposed, obtain new sterile equipment before preparation.
Common pitfall: A matching surname, fresh gloves, or changed needle cannot compensate for wrong-record association or syringe reuse. Assistance must also satisfy legal scope and instruction requirements.
60.Which injection findings distinguish extravasation from a systemic emergency?
Extravasation is leakage into surrounding tissue: local pain, swelling, or tightness requires stopping injection and clinical assessment. Progressive pain, blistering, altered distal sensation, or impaired perfusion requires urgent evaluation for serious injury. Stridor is a harsh, usually inspiratory sound indicating upper-airway narrowing, potentially from laryngeal edema; wheeze usually reflects lower-airway bronchospasm. Severe allergic-like airway compromise or anaphylaxis requires emergency activation, airway and breathing support, oxygen, vital-sign and oxygen-saturation monitoring, and patent vascular access. Emergency clinicians administer urgent epinephrine; inhaled bronchodilators can supplement treatment of bronchospasm, and IV isotonic fluids support hypotension.
Apply it
Forearm swelling suggests extravasation. Concurrent hoarseness, stridor, and falling oxygen saturation demand immediate airway emergency management. The technologist stops contrast, summons help, reports findings, and assists with oxygen, monitoring, equipment, and resuscitation within training. An extravasated cannula is unsuitable for emergency IV treatment; the team needs reliable alternative access. Medication administration requires appropriate authorization, training, and clinical direction.
Common pitfall: Initial blood return does not guarantee continued intravascular delivery. Extravasation volume alone does not determine severity, and local leakage can coexist with a systemic reaction. Antihistamines cannot replace epinephrine for anaphylaxis. Clinical reference: [ACR Manual on Contrast Media](https://www.acr.org/Clinical-Resources/Clinical-Tools-and-Reference/Contrast-Manual), sections on extravasation and acute reaction treatment.
What to focus on during revision
The following are CertMedbry study suggestions. Use the official outline to check the full scope of your examination.
- Allocate the largest study blocks to Engineering and Radiation Science and Basic Medical Knowledge while maintaining practice across all subjects.
- State quantities, units, assumptions, and expected direction of change before performing calculations.
- Distinguish photon quantity from energy distribution, attenuation from absorption, and administered activity from absorbed dose.
- Connect image appearance to anatomy, acquisition geometry, reconstruction, and physiological behavior.
- Keep radiochemistry in Nuclear Medicine Clinical Technology and image evaluation in Medical Image Informatics.
- Practise specific-instruction requirements, identification, aseptic assistance, injection assessment, and emergency recognition.
- Use the official outline to study remaining clinical, engineering, regulatory, equipment, and safety topics beyond this selective guide.
A practical preparation plan
1. Map the official scope
Use the MHLW correspondence table to assign topics to the 11 examination subjects. Identify intermediate headings that this guide does not develop, including remaining anatomy, clinical medicine, equipment, regulations, and emergency-care content.
2. Explain mechanisms aloud
Answer each concept heading, apply the mechanism to its case, and explain the discriminating cue. Contrast closely related mechanisms such as attenuation and absorption, diffusion restriction and shine-through, or setup verification and motion control.
3. Recalculate under changed conditions
Repeat attenuation, counting-statistics, magnification, half-life, ultrasound-depth, inverse-square, and BED examples with different values. State when their assumptions fail.
4. Locate the cause of failure
For an inadequate image or workflow discrepancy, identify whether the cause lies in positioning, exposure control, acquisition, reconstruction, decoding, biological behavior, or patient-order association before selecting a correction.
5. Review every alternative
Complete the 20 questions and explain why each alternative fits or fails. Use flashcards for spaced recall, then return to the official outline and coursework to address remaining scope.
Use your sample score as a starting point
The free set contains 20 original practice questions. It is a small learning sample, not an official examination or a validated pass prediction. Review each explanation and its source before moving to another topic.
Start the free sampleOfficial sources and updates
- 令和７年版診療放射線国家試験出題基準について
- 診療放射線技師国家試験出題基準 令和7年版
- 診療放射線技師国家試験出題基準と試験科目との対応及び出題割合
- 診療放射線技師国家試験出題基準の利用法
- 資格・試験情報｜厚生労働省
- NIST: X-Ray Mass Attenuation Coefficients—Section 2
- IAEA-TECDOC-1608
- Dosimetry for Radiopharmaceutical Therapy
- Ultrasound | National Institute of Biomedical Imaging and Bioengineering
- Information for Professionals | FDA
- Radiation Biology: A Handbook for Teachers and Students—Section 3
- What are the benefits of CT scans?
- DICOM PS3.3 2026d—C.7.6.3 Image Pixel Module
- 診療放射線技師国家試験の施行｜厚生労働省
- 001640439.pdf
- tp260424-06a_01.pdf
- seitouhyou.pdf
- ・診療放射線技師法(◆昭和26年06月11日法律第226号)
- Pub1196_web.pdf
- Pub1609_web.pdf
- PUB2021_web.pdf
- C.7.6.3.3 Image Pixel Description Macro
- ps-solution2-patient-identification.pdf
- Your Kidneys & How They Work - NIDDK
- Client Challenge
Confirm current eligibility, fees, scheduling and policies directly with the examination provider. CertMedbry is independent and is not endorsed by these organisations. How we handle content and corrections.