Category Archives: MEDICAL IMAGING

Digital Subtraction Angiography Technique


DSA is a way of taking images of arteries, veins and organs of the body  using complex computerised x-ray equipment. This usually requires an injection of a special ‘dye’ to highlight the blood supply to the legs, heart or other organ.  The ‘dye’ is a clear liquid which shows on x-rays due to its high density.  This ‘dye’ is harmless and will pass out of your body in your urine over the hours following your test.


In traditional angiography, we acquire images of blood vessels on films by exposing the area of interst with time-controlled x-ray energy while injecting contrast medium into the blood vessels.


1. X-ray imaging (Running time: 9min 55s.)

  • Introduction and explanation of x-ray imaging using the analogy of the shadow cast by a net curtain in sunlight. Includes a series of x-ray pictures of: dislocated finger; fractured tibia and fibula; tibia repaired using a metal rod; lungs; lumbar spine; hairline fracture to the skull; skull complete with hearing aid (which the patient forgot to take off!!)
  • Demonstration of a standard x-ray set including x-ray tube, aperture, film cassette and intensifying screens. Description includes two series of graphics: the first showing the detailed construction of an x-ray tube in its housing; the second, explaining how intensifying screens work.
  • A barium meal examination being performed.
  • Mammography being performed. Includes x-ray pictures of a breast with a tumour and one without (for comparison).
  • Demonstration of a CT scanner. Includes a brief interview with a radiographer who interprets a set of brain scans which reveal a brain tumour.

2. Radiotherapy (Running time: 5min 9s.)

  • Interview with a medical physicist who explains how radiotherapy treatments were planned for two case studies: cancer of the prostate and cancer of the breast.
  • Demonstration of a cobalt 60 machine showing the aperture and wedges (used to shape the gamma ray field). Also shows the layout of the treatment suite (concrete walls a metre thick etc).
  • Demonstration of a linear accelerator.

3. Ultrasound (Running time 9min 52s.)

  • Introduction to ultrasound imaging by way of sonar aboard trawlers.
  • Ultrasound examination of a pregnant woman. The doctor locates and talks about the baby’s heart, head, foot (it obligingly waggles its toes at the camera!), and spine.
  • Ultrasound examination of the abdomen of a man. The doctor locates and talks about his gall bladder, liver and kidney. He shows how the machine is used to measure structures e.g. the length of the kidney.
  • Close-up of the ultrasound probe, with a series of graphics to explain how it works.
  • Introduction to Doppler ultrasound using the analogy of the change of pitch of the noise from a train as it passes. Includes simple graphic.
  • Demonstration of Doppler ultrasound being used to “listen” to the blood flow in the presenter’s arm.
  • Doppler ultrasound examination of the leg of a man with severe vascular disease. You can hear how blocked up his arteries are!
  • Demonstration by a clinician of how ultrasound imaging and Doppler ultrasound are used together to measure and create images of blood flow.

4. Nuclear medicine (Running time 7min 32s.)

  • Introduction, including delivery to the hospital radiopharmacy of molybdenum 99 from Canada.
  • Demonstration by a radiopharmacist of how drugs are labelled with technetium 99m (derived from molybdenum 99). In particular, he shows how fluid is drawn from a technetium generator.
  • Demonstration of how a gamma camera is used to image the head. Presenter shows and describes the lead collimator, sodium iodide crystal and photomultiplier tubes. Includes a graphic.
  • Interpretation of several gamma camera images: a brain scan (normal); kidney scan (shows that one ureter is blocked); bone scans (one showing a kidney tumour which has spread to the spine; the other, confirming no secondary tumours in a young man part of whose femur had been removed due to bone cancer).

5. Magnetic Resonance Imaging (Running time 4min 31s.)

  • Introduction, including the shattering of a tulip embrittled by immersion in liquid nitrogen and brief description of superconductivity.
  • Demonstration of Magnetic Resonance Imaging scanner.
  • Demonstration of how the MRI coil is made in the factory.
  • Demonstration of how strong the magnetic field is by showing how a set of keys suspended on a wire are drawn towards the coil.
  • Sequence of MRI images of a set of slices through a head, revealing detailed structure of brain, eyes etc.
  • Demonstration of advanced techniques to show: firstly, a heart beating and; secondly, rotation of a 3D image of the blood supply to the head.
  • Description of the latest compact MRI machine which enables heads, arms and legs to be examined more cheaply.



Lecture 1: Principles of X-ray imaging (940 kB)

Lecture 2 : Technology and applications for planar X-ray imaging (1.2 MB)

Lecture 3 : Principles of X-ray Computed Tomography (660 kB)

Lecture 4 : X-ray CT applications (1 MB)

Lecture 5 : Nuclear Medicine (356 kB)

Lecture 6 : Emission Tomographies (1.5 MB)

Lecture 7 : Principles of Ultrasound imaging (576 kB)

Lecture 8 : Applications of Ultrasound imaging (884 kB)

Lecture 9 : Nuclear Magnetic Resonance (776 kB)

Lecture 10 : Magnetic Resonance Imaging (1.8 MB)

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