Maharashtra HSC Radiology Technician (Vocational) cheat sheet

X-ray photons are produced when fast electrons from a heated tungsten filament are decelerated in the anode target; the tube is a highly evacuated diode with a thermionic cathode and a rotating anode.

Bremsstrahlung produces a continuous spectrum; characteristic radiation produces discrete lines when a K-shell vacancy is filled, with K-alpha lines of tungsten near 58-59 keV.

The maximum photon energy in keV equals the applied tube potential in kVp; total beam intensity is approximately proportional to kVp squared and directly to mAs.

Thermionic emission from the filament follows the Edison effect; filament current (measured in amperes, typically 3-6 A) controls the number of electrons available, whereas mA selected controls tube current.

The rotating anode spreads heat over a focal track; the effective focal spot is smaller than the actual focal spot because of the anode bevel angle (line-focus principle).

Total filtration is the sum of inherent filtration (glass envelope, oil, port) and added filtration; it removes low-energy photons and hardens the beam.

The inverse square law states intensity is inversely proportional to the square of distance; doubling the focus-to-film distance reduces dose rate to one quarter.

Rectification determines the high-voltage waveform: single-phase full-wave gives about 100% ripple, three-phase 6-pulse about 13%, three-phase 12-pulse about 4%, and constant potential near 0%.

The high-tension transformer steps up mains voltage to the kV range, the step-down filament transformer supplies low-voltage high-current heating, and the autotransformer selects kVp.

Standard projections are named by the path of the central ray: AP (anterior to posterior), PA (posterior to anterior), lateral, oblique, and axial; the part closest to the image receptor is stated in the projection name.

The PA chest projection is preferred over AP because it reduces cardiac magnification and scapular overlap; it is taken at 180 cm (6 ft) focus-to-receptor distance with a 12-degree caudal tube angle in some protocols.

For a PA hand, the palm is flat on the cassette with fingers slightly separated and the central ray perpendicular to the third metacarpophalangeal joint; a PA oblique hand uses 45 degrees of rotation.

The AP knee is taken with the knee flexed slightly and the central ray 1-2 cm below the patellar apex; the lateral knee requires 20-30 degrees of flexion to demonstrate the joint space.

Cervical spine lateral is taken at 150-180 cm with the patient's shoulders depressed; the open-mouth odontoid view demonstrates C1-C2 with the central ray through the open mouth.

The 15-degree cephalad angle for the AP axial cervical spine and the 15-20-degree cephalad angle for the AP axial sacrum are standard angulation rules to remember.

The lateral skull uses a 15-degree cephalad tube angle to avoid the orbits; the PA skull uses a 15-degree caudal angle to project the petrous ridges into the lower orbits.

The AP pelvis requires the feet internally rotated 15 degrees to bring the femoral necks into profile; the frog-leg lateral hip uses 45 degrees of abduction.

A minimum of two orthogonal projections at 90 degrees is the standard rule for any suspected fracture, so a single view is not acceptable.

Latent image formation in silver halide film depends on the Gurney-Mott mechanism: photon exposure liberates electrons trapped at sensitivity specks, which attract interstitial silver ions to form a latent image.

The characteristic curve (Hurter-Driffield curve) plots optical density against log relative exposure; the straight-line portion defines contrast, and the toe and shoulder define underexposure and overexposure.

Optical density equals log10 of the ratio of incident to transmitted light; a density of 1.0 transmits 10% of light, and 2.0 transmits 1%.

In computed radiography, the photostimulable phosphor plate stores energy in metastable electron traps; a scanning laser releases blue light detected by a photomultiplier tube.

The histogram in digital radiography represents the frequency of pixel values; the look-up table maps raw values to display values and controls window width (contrast) and window level (brightness).

Spatial resolution is measured in line pairs per millimetre; film-screen systems achieve about 5-8 lp/mm, whereas most digital systems are limited by pixel pitch.

Noise in digital imaging arises from quantum mottle, electronic noise, and fixed pattern noise; the detective quantum efficiency (DQE) describes how efficiently the system converts radiation to image.

The modulation transfer function (MTF) describes the system's ability to preserve contrast at each spatial frequency, with values from 0 to 1.

Digital post-processing includes edge enhancement, gradation processing, and noise reduction; over-processing produces halo artifacts and loss of fine detail.

Safelight testing uses a coin placed on a pre-exposed film for a defined time; a visible shadow indicates unsafe safelight or excessive fog.

Developer temperature is maintained at 20-22 degrees Celsius for manual processing; each 1 degree rise typically requires about a 10% reduction in development time.

Processing chemicals require replenishment according to workload; developer is replenished at about 1 litre per square metre of film processed, and fixer at roughly half that rate.

The developer acts on exposed silver halide to form black metallic silver; the fixer removes unexposed halide and hardens the emulsion, and incomplete fixing causes later yellow-brown staining.

Darkroom illumination is filtered to the film's sensitivity: red safelight for blue-sensitive film and amber or red for orthochromatic film; orthochromatic film is sensitive to blue and green.

A densitometer measures optical density, and a sensitometer exposes a step wedge for processor control charts; the processor is monitored with reference strips and plotted on a control chart.

Film storage requires temperatures below 21 degrees Celsius with relative humidity of 40-60%; elevated temperature or humidity causes fog and increased contrast.

The processor's transport time, developer temperature, and circulation are the key variables; a dropped roller or low replenishment causes artifacts such as guide marks or density variation.

Artifacts to identify: static marks (spark-like), pressure marks (black crescents), scratches (clear lines), and pi-lines (black lines from cracked screens) each indicate a specific darkroom or cassette fault.

The three fundamental protection principles are time, distance, and shielding; the inverse square law and short exposure times are the most practical controls.

Occupational dose limits: effective dose of 20 mSv per year averaged over 5 years, with no single year exceeding 50 mSv; the lens of the eye limit is 20 mSv per year averaged over 5 years.

Public dose limit is 1 mSv per year; the dose limit for apprentices aged 16-18 is 6 mSv per year, and the limit for a fetus is 1 mSv over the declared pregnancy.

The ALARA principle (As Low As Reasonably Achievable) and ALARA/ALARP require optimization of protection and use of dose constraints.

Personal dosimeters include the thermoluminescent dosimeter (TLD), optically stimulated luminescence (OSL) dosimeter, and film badge; the TLD uses lithium fluoride and measures dose by thermoluminescence.

A lead apron of 0.25 mm lead equivalent attenuates about 90% of diagnostic X-rays at 70 kVp, and 0.35 mm provides greater protection; aprons must be checked annually for cracks.

The gonadal shield should be placed after positioning and collimation, and the shield should be visible on the image to confirm correct placement.

Collimation to the area of interest reduces patient dose and improves image contrast by reducing scatter; the collimator light field must match the radiation field within 2% of the focus-to-receptor distance.

The annual dose limit for a radiation worker's hands and feet is 500 mSv, and the skin limit is 500 mSv per year averaged over 5 years.

The skeleton has 206 bones in the adult: axial skeleton (80 bones) and appendicular skeleton (126 bones), with the vertebral column comprising 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal segments.

The femur is the longest bone and articulates with the acetabulum; the femoral head has a fovea capitis for the ligamentum teres, and the neck-shaft angle in adults is about 125 degrees.

The heart lies in the middle mediastinum, with the apex at the fifth intercostal space in the midclavicular line; the right atrium forms the right border and the left ventricle the left border on a PA chest radiograph.

The lungs have 3 lobes on the right and 2 on the left, with the left lung having a cardiac notch and lingula; the carina is at the level of T4-T5.

The kidneys lie retroperitoneally at T12-L3, with the right kidney lower than the left because of the liver; the ureters descend to the bladder at the pelvic brim.

The liver occupies the right upper quadrant and is divided into 8 segments; the gallbladder fossa lies between the right and left lobes, and the common bile duct joins the pancreatic duct at the ampulla of Vater.

Densities on a radiograph: air (black), fat (dark grey), soft tissue and fluid (grey), bone and calcification (light grey), and metal (white); this is the radiographic density scale.

The growth plate (physis) appears as a radiolucent line in children; the epiphysis, metaphysis, and diaphysis are the three regions of a long bone.

Common pathologies to recognize: pneumonia (consolidation), pneumothorax (absent lung markings), pleural effusion (blunting of costophrenic angle), and osteoarthritis (joint space narrowing, osteophytes).

Barium sulphate is the standard positive contrast agent for the gastrointestinal tract; it is insoluble and inert, but is contraindicated if perforation is suspected because it causes peritonitis.

Water-soluble iodinated contrast such as gastrografin (sodium diatrizoate) is used when perforation is suspected; it is hypertonic and can cause fluid shifts in infants.

Iodinated contrast media for intravenous use are classified by osmolality: high-osmolar, low-osmolar (non-ionic), and iso-osmolar; non-ionic low-osmolar agents are preferred for patient comfort and safety.

The intravenous urogram (IVU) uses a bolus of contrast with films at 1, 5, 15, and 25 minutes; the nephrogram phase shows the parenchyma, and the pyelogram phase shows the collecting system.

The barium swallow examines the oesophagus, the barium meal the stomach and duodenum, and the barium enema the colon; a double-contrast study uses barium plus air.

Hysterosalpingography uses water-soluble contrast injected through the cervix to assess the uterine cavity and tubal patency; it is performed in the follicular phase.

Myelography uses water-soluble non-ionic contrast injected into the subarachnoid space; the patient is positioned to direct the contrast, and a post-procedure headache may indicate a dural leak.

Digital subtraction angiography (DSA) subtracts a pre-contrast mask image from the contrast image to show vessels; patient movement causes misregistration artifact.

The sialogram uses contrast injected into the parotid or submandibular duct; the parotid duct (Stensen's duct) opens opposite the upper second molar.

Patient identification uses two identifiers (name and date of birth or hospital number) before every examination; the request form must be checked against the patient's identity.

Informed consent requires capacity, disclosure of risks and benefits, and voluntariness; consent may be verbal or written, and a competent adult may refuse any examination.

Vital sign ranges in adults: respiratory rate 12-20 per minute, pulse 60-100 per minute, blood pressure about 120/80 mmHg, temperature 36.5-37.5 degrees Celsius, and oxygen saturation above 95%.

Basic life support sequence for an adult: check responsiveness and breathing, call for help, start chest compressions at 100-120 per minute with a depth of 5-6 cm, and give 30 compressions to 2 breaths.

Anaphylaxis to contrast presents with urticaria, bronchospasm, hypotension, and angioedema; adrenaline 0.5 mg intramuscularly (1:1000) into the anterolateral thigh is the first-line drug.

For a vasovagal reaction, lay the patient supine with legs elevated, loosen tight clothing, and monitor vital signs; for hypoglycaemia, give oral glucose if conscious and never give oral fluids if unconscious.

The radiotherapy and radiography department must have oxygen, suction, a resuscitation trolley, and an emergency call system; a patient with a contrast reaction should never be left alone.

Moving and handling uses a hoist or slide sheet, and the patient should be moved with feet in the direction of travel; manual lifting of a patient is a last resort.

Universal precautions require gloves for contact with body fluids, and hand hygiene is performed before and after every patient contact; sharps are disposed of in puncture-resistant containers.

The four principles of biomedical ethics are autonomy, beneficence, non-maleficence, and justice; confidentiality is a professional duty with exceptions for legally notifiable diseases and court orders.

Informed consent for a minor requires a parent or legal guardian, except in emergencies where treatment may proceed in the child's best interest.

The radiographer's scope of practice includes justification of the exposure, optimization of technique, and limitation of dose; a request may be declined if it is not clinically justified.

Professional regulation in India is through the Maharashtra State Council for Paramedical Sciences and the Maharashtra Medical Council; the Radiological Technologists' association is a professional body.

Communication with a patient should use simple language, avoid medical jargon, and be delivered in the patient's own language; a translator is used when language barriers exist.

The patient has the right to privacy during examination, to a chaperone, and to ask questions; a female patient should be offered a female attendant during intimate examinations.

Medical records must be accurate, legible, signed, dated, and retained as per hospital policy; alterations must be dated and signed, never erased.

Hospital procedures include the use of the HIS/RIS (hospital and radiology information systems) for ordering and reporting, and the PACS for image storage and retrieval.

A radiographer must report equipment faults, incidents, and near misses through the hospital's incident reporting system and must not modify equipment without authorization.

The clinical placement assessment covers positioning accuracy, image quality, radiation protection practice, patient communication, and professional behaviour; the logbook is signed by the supervising radiographer.

The 10-day rule states that abdominal and pelvic radiography in women of reproductive age should be performed within 10 days of the onset of menstruation to reduce the risk of irradiating an early pregnancy.

The 28-day rule for non-abdominal examinations allows the examination at any time if the patient is not pregnant; if pregnancy is possible, the examination should be deferred or the patient asked about the last menstrual period.

A rejected image must be recorded with the reason (positioning, exposure, artifact, or patient motion) and the reject rate should be monitored as part of quality assurance.

The exposure index (EI) or deviation index (DI) in digital radiography indicates whether the receptor received appropriate exposure; the DI is calculated relative to the target EI.

A standard film-screen cassette uses rare-earth intensifying screens; the intensifying screen converts X-rays to light, and the film must be matched to the screen's emission spectrum.

The cassette must be loaded and unloaded in the darkroom or with a daylight loader; a light leak causes fog, and a dirty screen causes white spots on the image.

Patient preparation varies: fasting for abdominal and contrast studies, bowel preparation for barium enema, and removal of metallic objects before all examinations.

The radiographer must check the image before the patient leaves the department, and repeat only if the image is diagnostically unacceptable.