B.Sc. Medical Imaging Technology — II Year Question Paper Scope (Radiation Physics, Imaging Physics & Dark Room Techniqu: quick revision, 50 bites

The Grid: Your Primary Scatter Killer

Grids trade dose for contrast.

A grid sits between the patient and the image receptor and absorbs **scattered radiation** that would otherwise fog the image — improving contrast at the cost of increased patient dose.

Takeaway. Grids improve contrast but demand correct alignment and focal distance — otherwise cut-off ruins the film.

Dose Metrics You Must Distinguish

Three doses, three meanings.

Takeaway. Equivalent dose is organ-level; effective dose is whole-body risk; RBE compares radiation types.

Latent Image Formation: The Gurney-Mott Mechanism

Silver atoms hide the image first.

Takeaway. Latent image = clusters of silver atoms at sensitivity specks; development makes them visible.

Manual Processing: Five Sequential Steps

Five tanks, one image.

Takeaway. Order matters: develop → stop → fix → wash → dry; skipping any step causes artifacts or fading.

Manual vs Automatic Processing

Same chemistry, different speed.

Takeaway. Automatic processing wins on speed and consistency; manual depends on operator discipline.

Anode Heel Effect

The anode side is dimmer.

X-rays emitted toward the **anode** side of the tube are attenuated by the anode itself, so intensity is **lower on the anode side** and higher on the cathode side.

Takeaway. Anode heel effect: cathode side brighter — orient thicker anatomy toward cathode.

ALARP Principle

As low as reasonably achievable.

Takeaway. ALARP is the operational rule for every X-ray exposure — justify, optimise, limit.

Radioactive Decay Law & Half-Life

Exponential decay in one line.

Activity halves every half-life — after n half-lives, activity is $A_0 / 2^n$.

Takeaway. Decay is exponential; half-life and decay constant are inversely linked by ln 2.

Photoelectric Effect & Its Diagnostic Role

Bone lights up because of this.

An incident X-ray photon ejects an inner-shell electron; the vacancy is filled with emission of a characteristic photon. Probability rises sharply with atomic number (∝ Z³) and falls with photon energy (∝ 1/E³).

Takeaway. Photoelectric absorption gives contrast — exploit it with low kVp and high-Z contrast agents.

Diode vs Triode Vacuum Tubes

Two electrodes or three?

Takeaway. Adding a grid turns a diode into a triode — enabling control of electron flow.

Scintillation Detector: Light From X-Rays

X-rays in, light out.

Takeaway. Scintillation detectors convert X-rays → light → electrical signal for measurement.

Thermoluminescence Dosimeter (TLD)

Heat releases trapped dose.

TLD material (commonly LiF) traps electrons in metastable states during exposure; **heating** releases them as light proportional to dose.

Takeaway. TLD stores dose as trapped electrons; heat releases light proportional to dose.

Quality vs Intensity of X-Rays

kVp sets quality, mAs sets quantity.

Takeaway. kVp = quality (penetration); mAs = quantity (number of photons).

Geometric vs Motion Unsharpness

Blur has two different causes.

Takeaway. Two blur sources, two fixes — don't confuse geometric with motion unsharpness.

Characteristic Curve & Sensitometry

The film's fingerprint.

The characteristic (H&D) curve plots **optical density vs log relative exposure** and defines film speed, contrast, and latitude.

Takeaway. The H&D curve tells you a film's speed, contrast (gamma), and latitude at a glance.

Magnification & Distortion

Size lies when geometry is wrong.

Takeaway. Magnification grows with OID; distortion grows with angulation — control both geometrically.

Radiation Protection in Mammography

Low dose, high stakes.

Takeaway. Mammography protection = low dose + compression + optimised beam quality + strict QC.

Delta vs Wye Connections

Two ways to wire three phases.

Takeaway. Delta has no neutral; Wye provides a neutral and √3 voltage relationship.

Transformer Laws in X-Ray Generators

Turns ratio rules voltage.

Step-up transformers raise kVp for the tube; step-down transformers supply filament current.

Takeaway. Turns ratio sets voltage ratio; power is conserved across the transformer.

Preferred Views in Intestinal Obstruction

Erect and supine tell different stories.

Takeaway. Erect + supine abdomen is the standard pair for suspected obstruction.

Scoliosis Series: Views That Matter

Curve needs full-length views.

Takeaway. Full-spine PA + lateral + bending views form the scoliosis workup.

Chest: Basic and Special Views

PA and lateral first, then specials.

Takeaway. PA + lateral is the baseline; add lordotic/oblique/decubitus for specific clinical questions.

Ankle Mortise Projection

15° in, 15° medial.

Ankle mortise view uses **15° internal rotation** of the foot with the beam angled to open the mortise joint — essential for assessing the lateral malleolus and joint space.

Takeaway. Mortise view = internal rotation to clear the mortise joint.

Skyline (Sunrise) View

Look up under the patella.

Skyline view images the **patellofemoral joint** with the knee flexed and the beam directed tangentially — used for patellar tracking and chondromalacia.

Takeaway. Skyline view = tangential patellofemoral joint assessment.

Jug Handle Projection (Zygomatic Arch)

One angle, whole arch.

The jug handle view uses a **15° cephalad angulation** with the head rotated to project the zygomatic arch clear of the skull — used for arch fractures.

Takeaway. Jug handle = zygomatic arch view with 15° cephalad tilt.

Babygram

Whole baby, one film.

A babygram is a **single full-body radiograph of a neonate/infant** used to screen for congenital anomalies, line/tube positions, and skeletal survey — minimising handling and dose.

Takeaway. Babygram = whole-body infant film for lines, tubes, and skeletal survey.

Unilateral Frog-Leg Projection

Hip in abduction, one side.

Frog-leg lateral of one hip uses **abduction and external rotation** of the femur — used for hip joint assessment when bilateral positioning is contraindicated.

Takeaway. Frog-leg = abducted, externally rotated femur for hip joint detail.

Infant vs Adult Chest Anatomy

Babies breathe differently.

Takeaway. Infant chest: rounder, thymus visible, higher diaphragm — don't mistake for pathology.

Coccyx View

Angle down to see the tail.

Coccyx is best shown on a **lateral view with the beam angled caudally (~10°)** or on an AP with the tube angled cephalad — because the coccyx curves anteriorly.

Takeaway. Coccyx needs an angled view to clear the symphysis and sacrum.

Skeletal Survey

Every bone, one protocol.

A skeletal survey is a **standardised series of radiographs covering the whole skeleton** — used in suspected non-accidental injury, myeloma, and metastatic disease.

Takeaway. Skeletal survey = protocolised whole-skeleton imaging for systemic bone disease.

Dental Formula & Tooth Anatomy

32 teeth, 4 quadrants.

Adult dental formula: **2-1-2-3 per quadrant (32 teeth)**; deciduous: **2-1-0-2 per quadrant (20 teeth)**. Each tooth has crown, neck, and root with enamel, dentine, pulp, and cementum.

Takeaway. Adult 32 / deciduous 20 — memorise the quadrant formula.

Skull Occipito-Frontal (OF) View

Forehead to film.

The OF (Water's-type frontal) view places the **occiput on the receptor with the beam angled cephalad** — used for facial bones and sinuses.

Takeaway. OF view = occiput down, beam angled — facial bones and sinuses.

Radiation Protection in Pelvic Radiography

Shield the gonads, always.

Takeaway. Pelvis = high gonadal dose — shield, collimate, justify.

Carpal Canal Formation

A tunnel of bones and ligament.

The carpal canal is formed by the **carpal bones (concave arch) and the flexor retinaculum** — it transmits the median nerve and flexor tendons; narrowing causes carpal tunnel syndrome.

Takeaway. Carpal canal = carpal arch + flexor retinaculum; median nerve runs through it.

Cranial vs Facial Bones

8 cranial, 14 facial.

Takeaway. 8 cranial + 14 facial = 22 skull bones.

Knee AP Projection

Straight on, slight rotation.

Knee AP: patient supine, knee extended, **1–2 cm inferior to patellar apex as centre**, slight internal rotation of the leg to bring the patella central and open the joint space.

Takeaway. Knee AP = supine, extended, slight internal rotation, centre just below patella.

Leg Lateral View

Side-on, knee flexed.

Lateral leg: patient lateral, **affected leg closest to receptor**, knee flexed ~30° for stability, beam centred to mid-leg — used for tibia/fibula and knee assessment.

Takeaway. Lateral leg = affected side down, knee flexed, mid-leg centring.

Pelvic Outlet Projection

Angle up to see the ring.

Pelvic outlet view uses a **cephalad tube angulation (~40°)** to project the pelvic ring and sacrum clear of the symphysis — used for sacral and pelvic ring fractures.

Takeaway. Outlet view = cephalad angle to open the pelvic ring.

Cervico-Thoracic Junction View

The hardest junction to see.

The C7–T1 junction is best shown on a **swimmer's view** (one arm up, one down) or a **lateral with shoulder depression** — because shoulders obscure it on standard views.

Takeaway. Swimmer's view clears the shoulders to show C7–T1.

Nasal Bone Views

Two angles for a tiny bone.

Nasal bone is shown on **lateral (with dental occlusal or soft-tissue technique)** and **superoinferior (axial) views** — both needed to assess fracture displacement.

Takeaway. Nasal bone = lateral + axial views together.

Cephalographic Techniques

Head in a frame, measured.

Cephalography uses a **cephalostat** to fix the head at a standard distance and orientation — lateral and PA views are used in orthodontics for growth and treatment planning.

Takeaway. Cephalography = reproducible head positioning for orthodontic measurement.

Basic Femur Views

AP and lateral, whole bone.

Femur is imaged with **AP and lateral views including both joints** (hip and knee) — because fractures can be missed if only the mid-shaft is included.

Takeaway. Femur films must include both joints — always AP + lateral.

Basic Elbow Projections

AP and lateral — always both.

Elbow standard series: **AP (extended) and lateral (flexed 90°)**; add oblique views for radial head and capitellum assessment.

Takeaway. Elbow = AP + lateral + oblique for full joint assessment.

Plain Radiography of Sternum

Angle to clear the spine.

Sternum is imaged with **lateral and oblique (RAO) views** — the oblique projects the sternum clear of the spine and heart.

Takeaway. Sternum = lateral + RAO oblique to clear the spine.

Grid Cassette

Grid built into the cassette.

A grid cassette has the **grid permanently mounted inside the cassette** — convenient for portable work but adds weight and requires correct SID to avoid cut-off.

Takeaway. Grid cassette = built-in grid; convenient but SID-sensitive.

pH in Film Processing

pH decides the chemistry.

Developer is **alkaline (pH ~10)** to activate reducing agents; fixer is **acidic (pH ~4–5)** to stop development and harden the emulsion. Wrong pH → poor density or incomplete fixation.

Takeaway. Developer alkaline, fixer acidic — pH drift ruins the film.

Wet Bench vs Dry Bench

Two zones, one darkroom.

Takeaway. Wet bench = chemistry; dry bench = film handling — keep them separate.

Crossover Effect

Light leaks around the screen.

Crossover effect occurs when light from one intensifying screen exposes the **opposite emulsion** of a double-emulsion film — causing **unsharpness**. Anti-crossover (light-absorbing) layers reduce it.

Takeaway. Crossover = light from one screen fogging the far emulsion; anti-crossover layers fix it.

Luminescence vs Phosphorescence

Glow now or glow later.

Takeaway. Luminescence = glow during excitation; phosphorescence = glow after.

SNR, Image Contrast & FFD

Three numbers that define image quality.

Takeaway. SNR, contrast, and FFD are the three levers of image quality you must know.