PhysicsChapter 11: Medical Imaging
Exam Grid: Medical Imaging
Expanded revision grid for Unit 25.
Learning objectives
- Explain Exam Grid: Medical Imaging in easy language and identify its main physical principle.
- Apply the key relation or evidence for Exam Grid: Medical Imaging to a Class 12 conceptual or numerical question.
- Present an FBISE-style answer with correct reasoning, symbols, units, and a clear final statement.
What this grid covers
Expanded revision grid for Unit 25. Use full sentences in long answers: define the effect, describe the process in order, state one clinical reason, and mention a safety or limitation line where relevant. Numerical must show λ_min = hc/(eV) with SI constants. Distinguish characteristic lines from Bremsstrahlung continuum. CT answers must mention multiple angles → 2-D slice → stack to 3-D.
Where / symbols
- EXAM GRID: MEDICAL IMAGING
- Expanded revision grid for Unit 25.
- Piezoelectric
- Stress → charge/voltage; detects echoes; remember Confusing with inverse.
- Inverse piezo
- Voltage → vibration → ultrasound out; remember Forgetting f > 20 kHz.
Relationship
- λmin = hc/eV
Overview — Exam Grid: Medical Imaging
Expanded revision grid for Unit 25. Use full sentences in long answers: define the effect, describe the process in order, state one clinical reason, and mention a safety or limitation line where relevant. Numerical must show λ_min = hc/(eV) with SI constants. Distinguish characteristic lines from Bremsstrahlung continuum. CT answers must mention multiple angles → 2-D slice → stack to 3-D.
Medical imaging grid:
Piezoelectric: Stress → charge/voltage; detects echoes. Check: Confusing with inverse. Inverse piezo: Voltage → vibration → ultrasound out. Check: Forgetting f > 20 kHz. Sonography: Pulse–echo depth + brightness; non-ionising. Check: Saying it uses X-rays. Doppler US: Δf from moving blood → flow. Check: Only describing grey image. X-ray tube: Hot cathode, high V, anode target, heat. Check: Ignoring cooling/heat. Characteristic: Kα L→K; Kβ M→K; sharp lines. Check: Calling continuum characteristic. Bremsstrahlung: Braking near nucleus; continuum. Check: Fixed shell energies. λmin: hc/eV; higher V → shorter λmin. Check: Thinking X-ray speed changes.
Worked or exam application
Constants: h=6.63×10^-34 J s, c=3×10^8 m/s, e=1.60×10^-19 C (use book values if given). Target MCQ: high Z and high melting point. Safety line ready: ionising dose for X-ray/CT; ultrasound non-ionising. Worked λ_min at 10^5 V ≈ 1.24×10^-11 m.
Medical imaging grid:
| Topic | Must-say points | Common trap |
|---|---|---|
| 1. Piezoelectric | Stress → charge/voltage; detects echoes | Confusing with inverse |
| 2. Inverse piezo | Voltage → vibration → ultrasound out | Forgetting f > 20 kHz |
| 3. Sonography | Pulse–echo depth + brightness; non-ionising | Saying it uses X-rays |
| 4. Doppler US | Δf from moving blood → flow | Only describing grey image |
| 5. X-ray tube | Hot cathode, high V, anode target, heat | Ignoring cooling/heat |
| 6. Characteristic | K_α L→K; K_β M→K; sharp lines | Calling continuum characteristic |
| 7. Bremsstrahlung | Braking near nucleus; continuum | Fixed shell energies |
| 8. λ_min | hc/eV; higher V → shorter λ_min | Thinking X-ray speed changes |
| 9. Contrast | Light–dark range; absorption differences | Vague ‘clear picture’ only |
| 10. CT | Many angles → slice; many slices → 3-D | Omitting computer/angles |
Worked example
- Constants: h=6.63×10^-34 J s, c=3×10^8 m/s, e=1.60×10^-19 C (use book values if given).
- Target MCQ: high Z and high melting point.
- Safety line ready: ionising dose for X-ray/CT; ultrasound non-ionising.
- Worked λmin at 105 V ≈ 1.24×10-11 m.
In simple words
Long-question habit: write 8–12 lines with sequence words (first, then, finally) and one comparison (ultrasound vs X-ray, or plain film vs CT).
Key points
- piezo pair
- λmin = hc/eV
- CT angles → 3-D
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Exam Grid: Medical Imaging
Sticky Notes · Quick Revision
Core Idea
- Expanded revision grid for Unit 25.
- Use full sentences in long answers: define the effect, describe the process in order, state one clinical reason, and mention a safety or limitation line where relevant.
Key Relation
- Piezoelectric: Stress → charge/voltage; detects echoes
- Inverse piezo: Voltage → vibration → ultrasound out
Second Check
- Sonography: Pulse–echo depth + brightness; non-ionising
- Doppler US: Δf from moving blood → flow
Apply It
- Constants: h=6.63×10^-34 J s, c=3×10^8 m/s, e=1.60×10^-19 C (use book values if given).
- Target MCQ: high Z and high melting point.
- Safety line ready: ionising dose for X-ray/CT; ultrasound non-ionising.
- Worked λmin at 105 V ≈ 1.24×10-11 m.
Common Error
- Long-question habit: write 8–12 lines with sequence words (first, then, finally) and one comparison (ultrasound vs X-ray, or plain film vs CT).
- Do not describe Exam Grid: Medical Imaging with a memorised label only; explain the physical cause and its observable effect.
- Do not read a comparison table as disconnected facts; use the final column to identify the condition or common trap.
FBISE Exam Check
- Define Exam Grid: Medical Imaging before using it.
- Show the physics in logical steps and define every symbol.
- Use correct units, signs, directions, and assumptions.
60-second revision
- Expanded revision grid for Unit 25.
- Piezoelectric: Stress → charge/voltage; detects echoes.
- Inverse piezo: Voltage → vibration → ultrasound out.
- Exam reminder: Long-question habit: write 8–12 lines with sequence words (first, then, finally) and one comparison (ultrasound vs X-ray, or plain film vs CT).
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