1. Buxton & District Science Discussion Medical Scanners Marge Rose 16 th November 2012

2. Buxton & District Science Discussion Confusion – they all look the same CT, MR, SPECT, PET, Ultrasound A plethora of names Why a scan? Introduction

3. Buxton & District Science Discussion CT – computed tomography (was CAT) SPECT – nuclear medicine (was radioisotopes) MR(I) is based on NMR PET stands for positron emission tomography Names

4. Buxton & District Science Discussion An aid to diagnosis Localisation Screening Assessment of function Treatment planning and monitoring Research Reassurance Why a scan?

5. Buxton & District Science Discussion We’ll look at History Importance Probe Signal – few natural ones Detector – match to signal What is it detecting? For each modality

6. Buxton & District Science Discussion EM spectrum

7. Buxton & District Science Discussion Ionisation Certain types of radiation can ionise atoms

8. Buxton & District Science Discussion Ultrasound Sound is experienced by our ears Caused by longitudinal pressure waves We can hear from 20 Hz to 20 kHz Above 20 kHz - ultrasound

9. Buxton & District Science Discussion Ultrasound scan 1980

10. Buxton & District Science Discussion CT scan – uses x-rays Here is the very first x-ray – it shows his wife’s hand and was taken in 1895. The first medical use was just a few months later in 1896. X-rays are the most important and widespread of the modalities we will look at in this talk. The method of production is essentially unchanged. They were discovered in 1895 by Röntgen.

11. Buxton & District Science Discussion X-ray tube and image But x-ray tubes and images have improved a great deal in over 100 years

12. Buxton & District Science Discussion The naked CT X-Ray tube 120-140kV Detector Array Detector Amplifiers & A/D Converters Cooling oil pump Cooling heat exchanger High Voltage Generator Collimator

13. Buxton & District Science Discussion Tomography “Atom” derived from Greek atomos meaning “uncut, indivisible” “Tomography” is from the Greek tomē meaning “cut” or tomos meaning “section” and graphein meaning “to write” Reconstruction of the data by Back projection X-ray tube Patient Grid

14. Buxton & District Science Discussion CT slice through abdomen Probe 120kV X-ray Interaction Photoelectric, Compton Property X-ray attenuation Image 3D reconstruction from multiple projections

15. Buxton & District Science Discussion SPECT – uses γ rays Becquerel discovered radioactivity in 1896 The Curies researched into it and Marie opened the first Radium Institute in 1914 Radioisotopes were first used in diagnosis after World War II when radioiodine became readily available Rectilinear scanner appeared in 1951 Anger camera was invented in 1957

16. Buxton & District Science Discussion Gamma camera detector First Anger camera I ever saw in use was in 1975 The most common radionuclide used is still Technetium 99m despite supply difficulties Gamma ray energy 140keV Half life of 6 hours ‘No’ beta emission Flexible chemistry

17. Buxton & District Science Discussion Nuclear Medicine X-ray images show anatomy whereas Nuclear Medicine images show function Uses unsealed radioactive sources introduced into the patient. Patients can still be radioactive when they leave the hospital Gamma cameras are much less common than x-ray machines Very few Nuclear Medicine tests are diagnostic – generally they are highly sensitive but are of low specificity ‘Scans’ can comprise of static or dynamic images, whole body, gated images or SPECT (single photon emission computed tomography)

18. Buxton & District Science Discussion Whole body imaging A type of static imaging – A whole body bone scan is a very common example

19. R-R interval 24 1234 Frame or bin Gated images – the MUGA

20. Buxton & District Science Discussion SPECT studies – Myocardial perfusion scan Probe Gamma emitting isotope Interaction Uptake of radiopharmaceutical Property Concentration of pharmaceutical in organ Image  Spatial distribution of counts  SPECT – 3D

21. PET – Positron Emission Tomography

22. Buxton & District Science Discussion Antimatter Each fundamental particle has an antimatter equivalent Same mass but opposite charge Positrons are positive electrons Collide with the first electron they come across to produce annihilation radiation

23. Buxton & District Science Discussion Positron annihilation e.g. 18 F 511 keV ++ e-e- Coincidence Unit

24. Buxton & District Science Discussion PET images NormalPre-therapyPost-therapy

25. Buxton & District Science Discussion MR scanner An MR(I) Scanner

26. Buxton & District Science Discussion MR – souped up NMR If placed in a magnetic field, the nucleus precesses around in the direction of that field Direct in an RF (radiofrequency) pulse and the nucleus can flip to the higher energy state, opposing the field When it relaxes back, it gives off an RF signal which is dependent on the chemical environment A hydrogen nucleus has spin

27. Buxton & District Science Discussion Gradient coils

28. Buxton & District Science Discussion MR Probe – EM pulses Interaction – Resonant energy exchange changes nucleus spin state Property – proton density, proton microenvironment Image – Map EM signal – 3D reconstruction

29. Buxton & District Science Discussion Artifacts, Hybrid scans The End