PRC RadTech cheat sheet

Photon energy: E = hν = hc/λ, where h = 6.626×10⁻³⁴ J·s and c = 3×10⁸ m/s; energy in keV equals 12.4 divided by wavelength in angstroms.

Bremsstrahlung produces a continuous spectrum; characteristic radiation produces discrete peaks at binding energies of the target.

Maximum x-ray photon energy equals the kVp numerically in keV; the beam contains a range of energies up to that maximum.

Inverse square law: I1/I2 = (d2/d1)²; doubling SID reduces intensity to one-fourth.

Attenuation: I = I0e^(−μx); half-value layer HVL = ln2/μ ≈ 0.693/μ.

Photoelectric absorption predominates at low kVp and high atomic number; Compton scatter predominates at higher energies in soft tissue.

Beam quantity is controlled by mAs (number of photons); beam quality is controlled by kVp and filtration (penetrability).

Increasing kVp increases HVL and reduces photoelectric interactions, lowering patient dose per exposure but reducing subject contrast.

Cathode: filament emits electrons by thermionic emission; focusing cup directs them toward the anode target.

Anode: tungsten-rhenium target; rotating anode spreads heat; stationary anode is used in low-output units.

Anode heel effect: beam intensity is lower on the anode side; position thicker anatomy toward the cathode.

Effective focal spot is smaller than actual focal spot because of the line-focus principle; smaller focal spot improves spatial resolution.

High-frequency generators produce nearly constant potential, higher effective kVp, and lower patient dose than single-phase units.

AEC uses ionization chambers to terminate exposure; backup timer and minimum response time prevent overexposure.

Inherent filtration includes glass envelope and insulating oil; added filtration is aluminum, minimum 2.5 mm Al total for >70 kVp.

QA tolerances: kVp accuracy within ±5%, exposure timer within ±5% for >10 ms, and mA linearity within ±10%.

Collimator light field must align with radiation field; misalignment increases patient dose and reduces image quality.

PA chest: upright, 72 in SID, chin elevated, scapulae rotated away from lungs, exposure at full inspiration.

Lateral chest: 72 in SID, arms elevated, left lateral preferred to reduce heart magnification.

Abdomen KUB: supine AP, 40 in SID, includes symphysis pubis to diaphragm; upright view for air-fluid levels.

AP pelvis: 40 in SID, feet internally rotated 15–20° to bring femoral necks parallel to receptor.

Cervical spine lateral: 72 in SID, shoulders depressed, demonstrate C1–C7 and C7–T1 junction.

Open-mouth odontoid: AP projection demonstrating C1–C2 and dens; patient opens mouth widely.

Vertebral counts: 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, 3–5 coccygeal.

Long bone parts: diaphysis (shaft), metaphysis (flared end), epiphysis (articular end), epiphyseal plate in children.

At least two orthogonal projections per body part; include joints above and below the area of interest.

Receptor exposure is primarily controlled by mAs; kVp affects contrast and penetrability.

15% rule: a 15% increase in kVp with half the mAs maintains receptor exposure while lowering contrast.

Magnification = SID/SOD; increase SID or decrease OID to reduce size distortion.

Grid improves contrast by absorbing scatter; higher grid ratio increases Bucky factor and patient dose.

Spatial resolution improves with smaller focal spot, smaller OID, larger SID, and smaller pixel size.

Quantum mottle is noise from insufficient photons; increase mAs or use a faster receptor to reduce it.

Digital exposure indicator (EI/DI) monitors receptor exposure; deviation indicates under- or overexposure.

Window width controls displayed contrast; window level controls displayed brightness.

DQE quantifies how efficiently a receptor converts incident radiation into image signal; higher DQE means lower dose.

ALARA: keep dose as low as reasonably achievable; use time, distance, and shielding.

Occupational effective dose limit: 50 mSv/year; public limit 1 mSv/year; lens 150 mSv/year; extremities 500 mSv/year.

Declared pregnant worker: fetal limit 0.5 mSv per month and 5 mSv total during gestation.

Inverse square law applies to scatter and primary radiation; doubling distance reduces dose to one-fourth.

Lead apron minimum 0.25 mm Pb equivalent; 0.5 mm Pb for fluoroscopy and high-dose interventional procedures.

Controlled areas require warning signs, restricted access, and personnel dosimetry.

Primary barriers protect from useful beam; secondary barriers protect from scatter and leakage.

Personnel dosimeters (TLD/OSL) are worn at collar level outside the apron; fetal badge under apron at waist.

PRC license renewal requires CPD units every three years; practice without a valid license is prohibited.

Core ethical principles: autonomy, beneficence, nonmaleficence, justice, confidentiality, and fidelity.

Informed consent requires disclosure, comprehension, voluntariness, and documentation.

RadTech scope: perform radiographic procedures and operate equipment under supervision; diagnosis and prescribing are outside scope.

Confidentiality is protected by professional codes and data privacy laws; disclose only on need-to-know or legal requirement.

Maintain professional boundaries; avoid romantic, financial, or social relationships that exploit the patient.

Report impaired or incompetent colleagues through appropriate channels; protect patient safety first.

Document accurately and objectively; never alter or falsify patient records.

Respect patient dignity, culture, and modesty; use appropriate communication and draping.

Ethical decision-making: identify the problem, gather facts, consider principles and laws, consult, act, and evaluate.