imaging methods in monitoring and diagnosis
DESCRIPTION
Imaging Methods in Monitoring and Diagnosis. Dr Lizzie Peachey. Imaging Modalities. X Rays Ultrasound Magnetic Resonance Imaging Nuclear Medicine. X-Rays. X-Rays. Discovered by Roentgen in 1895 Ionising radiation Higher frequency / short wavelength. X-Rays. - PowerPoint PPT PresentationTRANSCRIPT
Imaging Methods in Monitoring and Diagnosis
Dr Lizzie Peachey
Imaging Modalities
X Rays Ultrasound Magnetic Resonance Imaging Nuclear Medicine
X-Rays
Discovered by Roentgen in 1895
Ionising radiation Higher frequency /
short wavelength
X-Rays
X-rays produced by the x-ray tube pass through the body leaving a ‘shadow’ on the film
X-Rays
X-Ray Production
Contrast
Plain Digital Radiography
Computerised Tomography (CT)
CT X-Ray Beam
Computerised Tomography
Computerised Tomography
X-RaysPros Cons
◦ Non-invasive◦ Well established
technology◦ Still evolving◦ Flexible◦ Readily available and
therefore relatively cheap
◦ Ionising radiation◦ Not good at imaging soft
tissue on its own
Utilises sound waves at ultrasonic frequency Above 20KHz is ultrasound but usually 3–10
MHz for medical imaging purposes Transducer sends and receives ultrasonic
waves Echoes from tissue can be detected and
data interpreted digitally to produce image Position and depth of the echoes builds up a
complete picture Gel is used to improve imaging
Medical Ultrasound (MU)
MU Imaging
MU Imaging
Image Manipulation
MU Imaging
Doppler Imaging
Medical UltrasoundPros Cons
◦ Non-invasive◦ No ionising radiation◦ Dynamic technique◦ Portable◦ Can image soft tissue
effectively◦ Flexible equipment◦ Relatively cheap
◦ Limited in what can be imaged
◦ VERY user dependent
Greatest detail of all the imaging modalities Uses a powerful magnetic field to align the
magnetization of atoms in the body Data detected can be digitally converted
into an image Utilises tomographic techniques of CT but
no radiation
Magnetic Resonance Imaging
Human body = 70% water – H2O MRI uses the spin of hydrogen atoms
◦ Single positively charged proton Spin causes tiny magnetic field All in different directions – PRECESSION Spin frequency depends on the type of
atom or molecule – LARMOR FREQUENCY Hydrogen atoms in different tissues have
different Larmor Frequencies
MR Imaging Principle
Alignment of Atoms
MR Imaging
MR Imaging
Image Manipulation
MR ImagingPros Cons
◦ Non-invasive◦ Does not use ionising
radiation◦ Excellent for imaging
soft tissues◦ Can image function◦ Good spatial resolution◦ Good at cancer diagnosis
◦ Very expensive◦ Has health and safety
issues◦ Has ‘acceptability’ issues
with some patients
Use of radioisotopes Attached to pharmaceuticals Drugs absorbed preferentially by target
organ(s) Gamma emitter so can be detected Images produced digitally from data
gathered
Nuclear Medicine
Nuclear Medicine Images
Nuclear Medicine Images
PET-CT
Nuclear MedicinePros Cons
◦ Can image wide variety of tissue types
◦ Easy to target specific tissue
◦ Can image function◦ Utilises by-products of
other processes so cost effective
◦ Uses ionising radiation◦ Could be described as
invasive◦ Has many radiation
protection issues associated with it
◦ Better applications are expensive
What information is required? Does structure or function need to be seen? What can the patient tolerate? What would the clinician prefer? What is available for use? Is there a safer/cheaper alternative? Can potential risks be justified?
Which should be used?