MRCOG Part 1: Biophysics - Essential Study Guide

This is your essential guide to the Biophysics section of the MRCOG Part 1 exam. We built it from our own experience of sitting the exam, the RCOG syllabus and the official reading list. It lists the biophysics concepts most often tested, section by section.

Why Biophysics matters in MRCOG Part 1

Biophysics is crucial in obstetrics and gynaecology as it underpins many diagnostic and therapeutic techniques. Understanding biophysical principles is essential for interpreting results, ensuring patient safety, and applying these technologies effectively in clinical practice. For the MRCOG Part 1, a solid grasp of biophysics, particularly in areas like electrocardiography, ultrasound, X-rays, and electrosurgery, is necessary.

Biophysics syllabus, section by section

IElectrocardiography (ECG)

Principles and Interpretation of ECG

Cardiac Cycle and ECG Waveform
  • Relationship between electrical stimulation (depolarization, repolarization) and mechanical events
  • P wave: atrial depolarization
  • QRS complex: ventricular depolarization
  • T wave: ventricular repolarization
  • Significance of PR interval, QRS duration, QT interval
ECG Lead Placement and Recording
  • Limb leads (I, II, III) and augmented voltage leads (aVR, aVL, aVF)
  • Chest leads (V1-V6) and their views of the heart
  • Electrode placement and skin preparation
  • Standard ECG paper speed and interpretation of squares
Normal ECG Features
  • Heart rate calculation from ECG tracing
  • Normal sinus rhythm characteristics
  • Common normal variations (e.g., sinus arrhythmia)

IIUltrasound

Principles of Ultrasound

Sound Wave Generation and Properties
  • Definition of ultrasound (frequency > 20kHz)
  • Piezoelectric effect and transducer function
  • Types of ultrasound: continuous-wave and pulsed-wave
  • Typical frequency ranges used in medical ultrasound
Interaction of Ultrasound with Tissue
  • Reflection, scatter, and absorption
  • Acoustic impedance and its role in reflection
  • Rayleigh scattering and its significance
  • Relationship between frequency, penetration, and resolution
Real-time B-mode Scanning
  • Image acquisition and formation
  • Role of transducer, receiver, amplifier, time-gain compensation, scan converter

Doppler Ultrasound

Doppler Effect and Equation
  • Principle of Doppler shift
  • Relationship between velocity, angle of insonation, and frequency shift
Color Flow Doppler
  • Direction and velocity information
  • Color coding conventions (red and blue)
  • Interpretation of color hues

Safety of Diagnostic Ultrasound

Bioeffects
  • Potential harmful effects: heating and cavitation
  • Importance of minimizing exposure, especially in early pregnancy

IIIX-rays, Computed Tomography (CT), and Magnetic Resonance Imaging (MRI)

X-rays

X-ray Production and Detection
  • Mechanism of X-ray generation (electron deceleration, collision with metal target)
  • Image receptors (plates, films, computed and digital radiography)
  • Units of radiation exposure (sievert, rem)
Use of X-rays in Clinical Practice
  • Attenuation of X-rays by different tissues (bone, soft tissue)
  • Radiopaque contrast agents and their applications
  • Hysterosalpingography: procedure, indications, risks
  • Dual energy X-ray absorptiometry (DEXA): principles, T score, Z score

Computed Tomography (CT)

Principles of CT Scanning
  • Use of X-rays to create cross-sectional images
  • Advantages over plain radiography

Magnetic Resonance Imaging (MRI)

Principles of MRI
  • Use of magnetic fields and radiofrequency pulses
  • Alignment of hydrogen protons (H+ ions) in a magnetic field
  • Signal detection and image formation
  • Contrast agents (e.g., gadolinium-based) and their use
MRI in Pregnancy
  • Safety considerations
  • Use of contrast agents during pregnancy
Interventional MRI
  • MRI-guided procedures
  • Safety considerations

IVElectrosurgery

Principles of Electrosurgery

Interaction of Electric Current with Tissue
  • Effects of low-frequency vs. high-frequency currents
  • Mechanism of heating
  • Grounded vs. isolated electrosurgery systems
  • Role of the return electrode in grounded systems
  • Importance of surface area of the return electrode
Monopolar vs. Bipolar Electrosurgery
  • Current pathway in monopolar and bipolar diathermy
  • Types of electrodes used in monopolar diathermy
  • Relationship between electrode tip size and heating effect
  • Autocoagulation in bipolar diathermy
Tissue Effects of Various Waveforms
  • Blended waveform and its effect
  • Argon-enhanced electrosurgery

Safety of Electrosurgery

Hazards and Precautions
  • Direct coupling, insulation failure, capacitive coupling
  • Safe use of electrical surgical instruments
  • Considerations for bipolar vs. monopolar instruments
  • Importance of using the lowest effective power setting

VLasers in Endoscopic Surgery

Principles of Laser Operation

Light Amplification by Stimulated Emission of Radiation (LASER)
  • Mechanism of laser action
  • Tissue effects: vaporization, dissection, coagulation, sterilization
  • Types of lasers used in endoscopic surgery (gas, solid-state)

Types of Lasers

Carbon Dioxide (CO2) Lasers
  • Wavelength and absorption characteristics
  • Applications in endoscopic surgery
  • Limitations for laparoscopic surgery
Solid-State Lasers (Nd:YAG, KTP)
  • Wavelength and transmission characteristics
  • Tissue penetration and effects
  • Safety considerations (eye protection)

VIRadiotherapy

Principles of Radiotherapy

Mechanism of Action
  • Use of ionizing radiation to damage cellular DNA
  • Direct and indirect effects
  • Factors affecting cell survival (dose, oxygen tension, cell cycle phase)
  • Strategies to increase tissue oxygenation
Types of Radiotherapy
  • Primary therapy, adjuvant therapy, neoadjuvant therapy
  • Curative vs. palliative radiotherapy
  • Use of protons in radiotherapy

Delivery of Radiotherapy

Applications in gynaecological cancers
  • Linear accelerator (linac) machines
  • External beam radiotherapy
Internal-beam Radiotherapy
  • Sealed-source radiotherapy (brachytherapy)
  • Unsealed-source radiotherapy (radioisotope therapy)
  • Applications in gynaecological cancers
  • Examples of radioisotopes used (137Cs, 192Ir, 125I, 131I)
Radioimmunotherapy
  • Use of radiolabeled monoclonal antibodies

Safety of Radiotherapy

Adverse Effects
  • Acute effects (damage to epithelial surfaces, oedema)
  • Medium-term and long-term effects (fibrosis, hair loss, dryness, secondary cancers)
  • Effects of reirradiation

How to master Biophysics

  • Review: work through each section systematically and understand the core concepts before moving on.
  • Active learning: draw diagrams, build mind maps and explain concepts to someone else.
  • Test yourself: try our free practice questions, then work through the biophysics questions in the Uterio question bank.

Additional resources