INTRODUCTION TO FLUOROSCOPY, ULTRASOUND (US) AND RADIONUCLIDE IMAGING (RNI) Flashcards
WHAT IS ULTRASOUND ?
- Medical US works using
the principle of
echolocation which means
using sound to locate
objects (i.e. kidneys,
bladder etc.) - It utilises sound waves
with frequencies greater
than 20,000Hz
WHAT IS ULTRASOUND ?
Ultrasound waves are created using crystals (quartz)
which vibrate at a very high frequency when you pass
electricity through them which is called piezoelectricity.
As they vibrate, they push and pull the air around
them producing ultrasound waves.
Devices that produce ultrasound waves using
piezoelectricity are known as
piezoelectric transducers.
WHAT IS ULTRASOUND ?
The US probe has 2 main
functions:
1. To emit a sound wave
2. To receive the echoes
from the original wave
WHEN DO WE UTILISE US IN THERAPY
RADIOGRAPHY ?
Therapy radiographers have started US imaging
during the image guided radiotherapy workflow of
prostate cancer patients.
It provides good soft-tissue contrast and therefore it is a modality that allows contouring of structures such as the prostate and is also a real-time imaging modality.
Some of the currently available US systems
potentially even allow real-time volumetric imaging
and soft-tissue tracking, using a matrix probe.
WHEN DO WE UTILISE US IN THERAPY
RADIOGRAPHY ?
- Transperineal ultrasound (TPUS) provides
therapeutic radiographers with a non-ionising
means of localising, verifying and monitoring
the prostate in 3D during radiotherapy. This
means treatments can be more accurately
targeted and intrafractional motion of the
prostate can be corrected for, minimising the
dose to healthy tissue. - During the initial planning CT scan, a
transperineal ultrasound transducer is
positioned by therapeutic radiographers, the
prostate is identified, and an ultrasound
image is taken at the isocentre. This US
image, in conjunction with the CT scan, is
used by the oncologist to inform the
WHEN DO WE UTILISE US
IN DIAGNOSTIC
RADIOGRAPHY ?
US has a wide variety of uses and clinical
applications:
* General US (to visualise main abdominal organs)
* Obstetric US (during pregnancy)
* Musculoskeletal US (to visualise muscles,
tendons, ligaments and joints)
* Doppler US (to measure the blood flow through
veins and arteries)
* Cardiac US/Echocardiography (to visualise the
heart and its structures i.e. valves etc.
* Interventional US (US guided interventions,
biopsies)
WHAT IS FLUOROSCOPY ?
Involves the use
of real time x-
ray imaging to
produce a
continuous loop
of images and
visualise motion
X-ray video
(compared to
still images in
standard
projection
radiography)
Wide range of
application in
interventional
radiology
Higher dose
exposures to
both patients
and staff. Why ?
WHAT IS FLUOROSCOPY ?
WHAT IS FLUOROSCOPY ?
* Originating from Fluoroscopes which were
simplified devices made of cardboard screens
that had been coated with a layer of fluorescent
metal salt
* The images produced were quite faint and not
recorded in any way
* The development of the Image Intensifier and
TV cameras allowed for brighter images and
better radiation protection
* Video tape recording also meant images could
be recorded and played when required
FLUOROSCOPY USES
- Barium Swallows
- Barium Enemas (now replaced with CT Colons)
- Defecating Proctograms
- Biopsies
- Hysterosalpingogram (HSG)
- Angiography / Cardiac Catheterisation
- Orthopaedic / Urinary / Abdominal Surgery
- Arthrography
- Lumbar Facet Joint Injections / Pain Relief
- PTC
- Embolisations (bleeding or cancer)
DIGITAL SUBTRACTION ANGIOGRAPHY
(DSA)
Digital subtraction angiography
(DSA) is a fluoroscopic technique
used extensively in interventional
radiology for visualising blood
vessels. Radiopaque structures
such as bones are eliminated
(“subtracted”) digitally from the
image, thus allowing for an accurate
depiction of the blood vessels.
RADIONUCLIDE IMAGING
(RNI)
WHAT IS RNI ?
- RNI is grouped under Nuclear
medicine which is the practice of
using a radioactive tracer to
determine the physiological activity
of the patient - It involves the introduction of a
radioactive source into the patient - Achieved using
radiopharmaceuticals which consist
of a radionuclide that emits gamma
WHAT IS RNI ?
RNI is known as functional imaging
It visualises a physiological function (how well a specific organ is working) but does not provide any useful anatomical information due to poor spatial resolution
It has high sensitivity meaning its very good at identifying areas where there is activity
It also has low specificity meaning there is a lack of precision in differentiating benign disease from metastatic cancer in bone scans
Radionuclide Imaging (RNI)
Radiopharmaceutical:
Radioactive isotope which creates the image
Pharmaceutical which determines the physiological behaviour of the compound and where the signal accumulates to form the image
Ideal Radioisotope
Short half-life (but long enough to allow for a good signal during imaging)
A good gamma emitter with energy photons that are able to leave the body and reach the gamma camera
Easy to bind to other chemicals without altering their properties
Technetium-99m (99mTc) is most commonly used and has a half-life of 6hrs
Ideal Pharmaceutical:
High target : non-target uptake ratio
Does not alter the patient’s physiology and not toxic
Easily/cheaply produced
Positron Emission Tomography (PET)
Another Nuclear Medicine imaging technique that involves the use of a radiopharmaceutical injected in the body
Tomographic nuclear imaging so cross-sectional images produced
Functional imaging technique that is used to observe metabolic processes in the body as an aid to the diagnosis of disease
Positron Emission Tomography (PET)
During a PET scan, a patient is injected with a tracer which is a chemical normally found in the body such as glucose, fluorine etc) which has been tagged with a radioactive isotope
Most common radionuclide used is Fluorine-18 and is injected as FDG (fluorodeoxyglucose) which is similar to sugar (glucose) and travels to areas of the body using a lot of energy
The F-18 in FDG decays via Beta + decay (too many protons) releasing a positron
