Medical imaging summary 1

•Overview of various medical imaging/treatment techniques•Quiz•Electricity

Why use medical imaging

Medical Imaging/treatment Radiation

Diagnostic X-ray, CT (Computed Tomography), PET (Positron Emission Tomography), LINEAC (Linear Accelerator)

Non-ionisingMRI (Magnetic Resonance Imaging),

Ultrasound/Sonography (Sound wave), Endoscope (light)

X-ray Machines

X-ray machines – X-ray Photon Energy

X-ray machines – Anode

Tungsten Hi Atomic number

High melting point High-conducting

ability


•A target for high-voltage electrons from the filament; thereby becoming the source of the x-ray photons.•Conducts the high voltage from the Cathode back into the circuit.

•The purpose of the cathode is to conduct a high voltage to gap between cathode and anode.

•Flow of electrons from cathode to anode.


•The purpose of the cathode is to conduct a high voltage to gap between cathode and anode.

•Flow of electrons from cathode to anode.


Tungsten – is the target surface is where the high speed electrons are attracted from the filament are suddenly stopped.

Braking radiation" or "deceleration radiation"

X-ray machines – X-ray production X rays are produced by 2 forms of

electron interaction with the tungsten target.

Bremsstrahlung Characteristic Photons

X-ray machine - Filtration The bremsstrahlung photons generated within

the target material are attenuated as they pass through typically 50 microns of target material. The beam is further attenuated by the aluminum or beryllium vacuum window.

The results are an elimination of the low energy photons, 1 keV through l5 keV, and a significant reduction in the portion of the spectrum from 15 keV through 50 keV. The spectrum from an x-ray tube is further modified by the filtration caused by the selection of filters used in the setup.

X-ray machines – Image

CT (Computed Tomography)Computed axial tomography (CAT)

Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation

CT (Computed Tomography)Tomography Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation

Tomography Reconstruction

PET (Positron Emission Tomography)

The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide


When a positron is emitted by a nucleus, it almost instantly finds an electron and the pair annihilates, converting all the mass energy of the two particles into two gamma rays each at 511kev. The two gamma ray photons possess momentum, and the conservation of momentum requires that they travel if opposite directions. A simultaneous detection of gamma ray photons in two detectors places the source on a line between those detectors.


Radionuclide, placed on a chemical - glucose.

Patient fasts for 12 hours so body is starved from energy.

When injected glucose will concentrate to more active cells, as patient lying still glucose will to cancer cell. Cancer cells are more active than normal cells as they are rapidly dividing.


Fuse PET scan with CT scan.

Some PET scanners have CT scanners also

Ultrasound/ SonographyDiagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions

Uses sound waves to produce an image

Doppler effectThe received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.

Is the change in frequency of a wave for an observer moving relative to the source of the wave.

Doppler effect

MRI (Magnetic Resonance Imaging)Medical imaging to visualize detailed internal structures. MRI makes use of the property of nuclear magnetic resonance (NMR) to image nuclei of atoms inside the body.

Uses the varying magnetic properties of atoms to produce an image

MRI (Magnetic Resonance Imaging)

Endoscopy

Means looking inside

Typically refers to looking inside the body for medical reasons using an endoscope

Endoscopy

Rigid Endoscope is solid metal tube with a series of lens inserted in the tube

Flexible Endoscope, the principle optical component is either a plastic or glass fibre bundle for delivery of the image, plus additional fibres for the light.

X-ray Quiz

1. Name 2 types of imaging techniques that use radiation and 2 that don't.

2. When a patient is due to undergo a PET scan they are injected with a radionuclide. What is emitted from the radionuclide? What reaction takes place after?

3. How does a CT scan obtain an image that is a slice?

X-ray Quiz

3. Name the device used to obtain the images.

A B

C D

X-ray Quiz4. Ultrasound work below human hearing

frequency T/F?5. PET scan are a relatively quick procedure

T/F?6. Ultrasound cannot travel through 2

mediums in the body what are they?7. There are white area black areas on an X-

ray image are showing variation in what?8. What is the main principal behind an MRI

machine and the subject being investigated?

X-ray Quiz

Organise these in terms of flow from electron source to X-ray. Start to finish.

Key terminology

Characteristic Photon, Patient, Anode, Tungsten Target, Film, Filament, Cathode, Bremsstrahlung, Scatter Filter, Casset.

X-ray Quiz

1. Cathode,1. Filament,2. Tungsten Target,2. Anode,3. Bremsstrahlung, Characteristic Photons, 4. Patient, 5. Scatter Filter, 6. Cassette, 7. Film.

Thank You

Medical imaging summary 1

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