PhysicsUK
ULTRASOUND / PULSE–ECHO

Find the hidden boundary.

Send a pulse. Read the echo. Discover what lies beneath.

THE IMAGING BENCHReady to send
↔ Drag the probe along the surface.
MEDICAL IMAGING LAB

Choose an investigation.

Saved experiments contain the authored structure and notebook. Use CSV for pupil measurements without hidden target dimensions.
OBJECTS ON THE BENCH

Build the phantom.

Reveal the structure to edit its tissue objects. Measurements remain in your notebook.
PRECISE SETTINGS

Probe & receiver.

The probe position changes the next acquired line. A recorded pulse retains the position and tissue properties used when it was sent.

Materials and instrument model

The reference medium has c = 1500 m/s and ρ = 1000 kg/m³. Other material presets are illustrative teaching values. Boundaries are perpendicular to the beam. Multiple reflections, refraction, tissue speckle and clinical calibration are omitted.

Echo voltage envelope is proportional to the square root of returned intensity. Transmission and attenuation apply on both the outward and return paths. The display gain does not change raw measurements.

Time cursors resolve 0.1 µs. Display brightness can clip at high gain. A-scans show a finite pulse; nearby echoes can overlap.
CAPTURE · COMPARE · EXPLAIN

Your evidence.

Depth from cursors uses the scanner's assumed sound speed. Compare it with your own calculation. Captures retain the settings used for that acquisition.
A LITTLE HELP GETTING STARTED

Follow the echo.

Bench and evidence. The bench takes most of the screen. Use the Image, Graph and Readings tabs (Scan and Readings for ultrasound). Compare opens the image and graph together. Drag the bench divider, or the image/graph divider inside Compare; arrow keys resize, Shift makes larger steps, and Escape cancels a drag. Enter or double-click resets a divider; Reset layout restores the bench-first layout. Switching panels and resizing keep the current acquisition. Open the patient card to load a clinical example, or What am I seeing? for the current investigation.

  1. Send. Press the pulse button on the probe or Send pulse below the bench. Watch the outward pulse meet a boundary and return.
  2. Measure. Drag A to the centre of the transmitted pulse and B to an echo peak. Numeric inputs provide the same control.
  3. Calculate. Use the round-trip delay: d = cΔt / 2. Enter your depth, check it and capture the evidence.
  4. Investigate. Move the probe, change the pulse, remove the gel or reveal and edit a tissue object. Send a new pulse after an edit.
  5. Scan. B displays only acquired lines. Sweep scan acquires a sequence of lines across the phantom. Blank columns have not been scanned.
Physics, timing and scope

Each acquisition snapshots the independent probe and tissue objects. Echo timings follow their path lengths and sound speeds. Slowed playback illustrates that recorded event; replay does not add another scan or measurement. No echo is drawn before its returning pulse reaches the receiver.

Gain and brightness process the received signal. Reveal displays the authored object, separately from the measured B-scan. The model uses normal-incidence, single-boundary echoes and an ideal linear receiver.

Impedance Z = ρc. Intensity reflection R = [(Z₂ − Z₁)/(Z₂ + Z₁)]². With an air gap, the low transmission acts on both journeys. Doppler uses Δf = 2f₀v cos θ / c, with positive shift for motion towards the probe. At 90°, speed cannot be inferred from this shift.

OCR A: 6.5.3. AQA Medical Physics option: 3.10.4.1; Doppler is an extension to that subsection. These are synthetic teaching phantoms.

AQA specification ↗ · NIH: ultrasound ↗