DHA Radiology / Radiographer cheat sheet

Occupational effective dose limit is 20 mSv per year averaged over five years, with no single year above 50 mSv; public effective dose limit is 1 mSv per year.

Equivalent dose limits are 20 mSv per year for the lens and 500 mSv per year for skin and extremities in occupational exposure.

A declared pregnant worker's fetus should receive no more than 1 mSv additional dose during the declared pregnancy.

ALARA is the decision rule that dose is kept as low as reasonably achievable while diagnostic information remains sufficient.

For a point source, intensity follows the inverse square law: I1/I2 equals the square of d2/d1.

Half-value layer is the material thickness that reduces beam intensity by half; the linear attenuation coefficient equals 0.693 divided by the half-value layer.

Diagnostic lead aprons are at least 0.35 mm Pb equivalent; 0.5 mm Pb equivalent is used for higher-kVp or interventional workloads.

Collimation reduces irradiated volume and scatter; gonadal shielding is indicated when it does not obscure the diagnostic region.

Absorbed dose is measured in gray, where one gray equals one joule per kilogram.

Equivalent dose in sieverts equals absorbed dose in gray multiplied by the radiation weighting factor.

Effective dose in sieverts equals the sum of tissue equivalent doses multiplied by tissue weighting factors.

Radiation weighting factors are 1 for x-rays and gamma rays, 2 for protons, and 20 for alpha particles.

ICRP 103 tissue weighting factors include 0.12 each for red marrow, colon, lung, stomach, and breast, and 0.08 for gonads.

Stochastic effects have no threshold; probability rises with dose while severity is independent of dose, as in cancer induction.

Deterministic effects have a threshold; severity increases with dose, as in skin erythema and cataract.

The human whole-body LD50/60 without medical support is approximately 4 Gy.

Thermionic emission from the cathode supplies electrons; tube current in milliamperes controls photon quantity.

Tube voltage in kVp controls electron acceleration and therefore beam quality and penetration.

Bremsstrahlung produces a continuous spectrum; characteristic radiation produces discrete peaks determined by target atomic number.

Exposure is proportional to mAs when mA and exposure time change inversely; mAs equals mA multiplied by seconds.

Attenuation follows I equals I0 times e raised to minus mu x, where mu is the linear attenuation coefficient and x is thickness.

Photoelectric absorption varies strongly with atomic number and photon energy; Compton scatter depends on electron density.

Added filtration uses aluminum equivalent to remove low-energy photons and increase half-value layer.

Magnification equals source-to-image distance divided by source-to-object distance.

Computed radiography uses a photostimulable phosphor plate read by a laser; direct digital radiography uses a thin-film transistor array.

DICOM defines image file format, metadata, and network services; PACS stores and displays images; RIS manages scheduling and reports.

HL7 is used for clinical and administrative messaging such as order and worklist exchange.

Exposure index is a vendor-specific measure of detector signal; deviation index compares actual exposure index with target.

DICOM grayscale standard display function is used to calibrate diagnostic monitors for perceptual linearity.

Automatic exposure control uses ionization chambers or detector feedback and a backup timer to terminate exposure.

Lossless image compression preserves diagnostic data; lossy compression discards data and is restricted by clinical policy.

Detector flat-field calibration corrects gain and offset variations and reduces fixed-pattern noise.

AP means the beam enters anteriorly; PA means it enters posteriorly; lateral and oblique projections are named by beam entry and patient position.

A PA chest radiograph is upright at 180 cm source-to-image distance, taken at full inspiration, with scapulae rotated clear of lung fields.

A supine AP abdomen radiograph is typically taken at 100 cm source-to-image distance and includes diaphragm to symphysis pubis for a KUB.

An upright abdominal radiograph is used to demonstrate air-fluid levels when bowel obstruction is suspected.

Cervical spine lateral and open-mouth odontoid views assess alignment and the atlantoaxial joint.

Trauma imaging uses cross-table lateral or modified projections when the patient cannot be turned.

Two orthogonal views of an extremity are standard because a single view may miss or misrepresent a fracture.

Pediatric immobilization and collimation reduce motion and dose; shielding is placed only when it does not obscure anatomy.

Subject contrast depends on tissue attenuation differences; receptor contrast depends on detector response and display.

Spatial resolution is expressed in line pairs per millimeter and is limited by focal spot size, detector element size, and motion.

Modulation transfer function describes how well a system transfers spatial frequencies; higher values indicate better resolution.

Quantum mottle is noise from insufficient photons; increasing mAs increases photons and reduces mottle.

Signal-to-noise ratio compares signal amplitude with noise; contrast-to-noise ratio compares lesion-to-background difference with noise.

Window level controls displayed brightness; window width controls displayed contrast in computed tomography and digital images.

Geometric unsharpness increases with larger focal spot, shorter source-to-object distance, and longer object-to-image distance.

Size distortion is magnification; shape distortion includes elongation and foreshortening from oblique object orientation.

Repeat analysis classifies rejected images by cause such as positioning, exposure, artifact, or equipment fault.

Daily quality control for digital radiography includes uniformity, collimation, and artifact checks with a test phantom.

Monitor quality control uses test patterns and luminance measurements to verify display consistency.

Acceptance testing establishes baseline performance before clinical use; periodic testing compares performance with that baseline.

CR artifacts include plate scratches, dust, ghosting, and light leaks; DR artifacts include dead pixels, lag, and calibration errors.

Dose audit uses dose-area product and exposure index to compare practice with diagnostic reference levels.

Corrective action is documented when quality control results exceed tolerance limits.

The axial plane divides superior from inferior; coronal divides anterior from posterior; sagittal divides left from right.

Hounsfield units assign water zero, air about minus 1000, and dense bone about plus 1000.

The mediastinum contains the aorta, superior vena cava, pulmonary arteries, trachea, esophagus, and lymph nodes.

Upper abdominal cross-sections show liver, spleen, kidneys, pancreas, aorta, inferior vena cava, and bowel.

Brain cross-sections show gray matter, white matter, ventricles, falx cerebri, and tentorium cerebelli.

Pelvic cross-sections show bladder, rectum, reproductive organs, iliac vessels, and pelvic bones.

Spinal cross-sections show vertebral body, spinal canal, cord or cauda equina, nerve roots, and intervertebral disc.

Air appears lucent on radiographs; pneumothorax shows absent lung markings and a visible pleural line.

Pleural effusion appears dense and blunts the costophrenic angle on an upright chest radiograph.

Cardiomegaly is present when the cardiothoracic ratio exceeds 0.5 on a frontal adult chest radiograph.

Bowel obstruction may show dilated loops and air-fluid levels on upright abdominal images.

Free intraperitoneal air appears as subdiaphragmatic lucency on an upright chest or abdominal radiograph.

Fractures appear as lucent lines or cortical steps; healing callus may appear as sclerosis or new bone.

Renal obstruction can produce hydronephrosis, seen as dilated calyces and pelvis on ultrasound or contrast imaging.

Many malignant lesions enhance after contrast because of increased vascularity and capillary permeability.

Two patient identifiers, such as full name and date of birth, are confirmed before every examination.

Adult resting vital signs are approximately heart rate 60 to 100 per minute, respiratory rate 12 to 20 per minute, and oxygen saturation 94 to 100 percent on room air.

Informed consent requires capacity, adequate disclosure, understanding, and voluntary agreement.

Immobilization devices and padding improve image quality and reduce patient injury.

Oxygen is stored away from open flame and electrical spark sources.

Venipuncture uses aseptic technique; extravasation requires stopping injection and assessing the site.

Pregnancy screening is documented before examinations that may irradiate the pelvis or abdomen.

Patient education uses plain language, teach-back, and interpreter services when needed.

Iodinated contrast media can cause mild urticaria, moderate bronchospasm, or severe hypotension and airway compromise.

Severe anaphylactoid contrast reaction is treated with stopping contrast, airway support, oxygen, intravenous fluids, and intramuscular epinephrine.

Barium sulfate is avoided when gastrointestinal perforation or leak is suspected; water-soluble iodinated contrast is used instead.

Gadolinium is avoided in severe renal impairment because of nephrogenic systemic fibrosis risk.

Metformin may be withheld around iodinated contrast in significant renal impairment according to local protocol.

Contrast extravasation management includes stopping injection, removing the cannula, elevating the limb, and monitoring neurovascular status.

Adult cardiopulmonary resuscitation uses compressions at 100 to 120 per minute and a depth of 5 to 6 cm.

Syncope is managed by lying the patient flat, elevating the legs, and monitoring airway and circulation.

Standard precautions apply to all patients and include hand hygiene, gloves, gown, mask, eye protection, and safe injection practice.

Hand hygiene is performed before and after patient contact and after contact with body fluids or contaminated equipment.

Contact precautions require gloves and gown; droplet precautions require a mask; airborne precautions require an N95 respirator and negative-pressure room.

Alcohol-based hand rub is preferred for routine hand hygiene except when hands are visibly soiled or when caring for patients with C. difficile.

Needle-stick management includes washing the site, reporting immediately, and following post-exposure prophylaxis protocol.

Sterilization destroys all microorganisms including spores; disinfection reduces pathogens but may not destroy all spores.

Blood and body-fluid spills are contained, cleaned with detergent, and disinfected with an approved agent.

Regulated medical waste is segregated according to local infection-control and environmental rules.

A personal dosimeter is worn at chest or collar level outside the lead apron; a second badge is worn under the apron when required.

Lead apron, thyroid shield, and lead eyewear reduce occupational dose during fluoroscopy and mobile radiography.

Time, distance, and shielding are the three basic controls for occupational radiation exposure.

Lifting uses a wide base, bent knees, straight back, and team assistance for heavy or uncooperative patients.

RACE means rescue, alarm, contain, and evacuate; PASS means pull, aim, squeeze, and sweep for fire extinguishers.

Electrical equipment is inspected, grounded, and kept away from liquids.

Latex allergy requires latex-free gloves, tubing, and supplies.

Workplace violence response includes activating security, maintaining distance, and avoiding confrontation.

Informed consent requires a competent patient, adequate information, understanding, and voluntary agreement.

Confidentiality requires sharing patient information only with authorized persons who need it for care or as permitted by law.

DHA licensure defines the legal scope of practice; radiographers perform only procedures within that scope.

Documentation is contemporaneous, objective, accurate, and includes patient identity, procedure, contrast, and adverse events.

The four ethical principles are autonomy, beneficence, nonmaleficence, and justice.

Negligence requires duty, breach of duty, causation, and damages.

Mandatory reporting includes suspected child abuse, elder abuse, and specified communicable diseases as required by law.

Social media posts must not contain protected health information or identifiable patient images.