Post on 03-Jul-2020
Medical
Applications of
Nuclear Sciences
Ilham Al-Qaradawi Professor of Physics, Qatar University
Doha, Qatar
WNU-SI 2012 Oxford - UK
Outline
• Areas of nuclear medical uses
• Medical imaging
• X-ray and CT
• Magnetic Resonance Imaging (MRI)
• SPECT
• PET and PET/CT
• Accelerators applied to medicine
• Treatment therapies
• Summary
WNU-SI 2012 Oxford - UK
Medical applications
• Diagnostic; Medical imaging (Radiology): creating images
of internal human body or its functions
– X-rays and CT
– Magnetic Resonance Imaging (MRI)
– PET and PET/CT, PEM
• Treatment;
– Conventional radiation therapy
– Brachytherapy
– Hadron therapy
– Antiproton therapy
• Irradiation and sterilization.
WNU-SI 2012 Oxford - UK
Anatomical Imaging
• X-ray (Radiography and Fluoroscopy)
• Computerized Tomography, CT
• Magnetic Resonance Imaging, MRI
WNU-SI 2012 Oxford - UK
X-ray Radiography
• Radiography involves the use of an X-ray tube and a photographic plate.
• The patient is placed between the two and an image is produced on the film of the area exposed.
• A common “chest X-ray” is an example of a radiographic X-ray.
WNU-SI 2012 Oxford - UK
Fluoroscopic x-ray imaging
• In a fluoroscopic X-ray machine the film is substituted with an imaging device (image intensifier) which enables the radiologist to observe the part of the body exposed live on a video monitor.
• A blocking agent, such as barium, is often swallowed by the patient to allow the medical staff to observe internal processes in action.
• A fluoroscopic examination can be used to locate ulcers.
WNU-SI 2012 Oxford - UK
X-ray image versus CT scan
• A conventional X-ray image gives a shadow of the body
• organs and tissues of different densities show up differently on the radiographic film.
• Depending on where the lamp is, you see the outline of the pineapple or the banana.
C - RECONSTRUCTION
A – LINEAR SAMPLING
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B – ANGULAR SAMPLING
X RAYS
COMPUTERIZED TOMOGRAPHY
This is the basic idea of computer aided tomography. In a CAT scan machine, the X-ray beam moves all around the patient, scanning from hundreds of different angles. The computer takes all this information and puts together a 3-D image of the body.
X-ray computerized tomography (CT)
MAGNETIC FIELD: 1.5 – 3 Tesla
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RELAXATION
MRI
SIGNA
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EXCITATION
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Magnetic Resonance Imaging (MRI)
Magnetic field applied
WNU-SI 2012 Oxford - UK
MRI of upper torso (courtesy NASA)
MRI of knee
MRI of shoulder
Magnetic Resonance Imaging: morphology
WNU-SI 2012 Oxford - UK
Functional Imaging
• Reveal structure
through function
• Image produced
depends on biological
distribution of
compound in vivo
WNU-SI 2012 Oxford - UK
Scintigraphy by Gamma Camera
• Used to record emitted internal radiation from
injected isotopes to create two dimensional images.
WNU-SI 2012 Oxford - UK
SPECT (Single photon emission computed tomography)
• Uses gamma cameras, of multi-
heads slowly rotated around the
patient.
• Able to provide true 3D
information.
• Information presented as cross-
sectional slices.
• 85% of all nuclear medicine
examinations use Mo/Tc
Generators for diagnostics of
liver, lungs, bones.
WNU-SI 2012 Oxford - UK
Medical radionuclides
• Radionuclides are used in medicine
by two general classifications:
– Nuclear Medicine for diagnostic
procedures
– Radiation Oncology for radiation
therapy.
• Nuclides used for
radiopharmaceuticals:
– should decay by emitting only photons
– Should have a short effective half-life.
– Technetium-99m and Indium-113m are
commonly used radiopharmaceuticals.
WNU-SI 2012 Oxford - UK
Nuclear Medicine
• Radionuclides are used to determine the extent of a medical problem in a patient.
• The radionuclide is “attached” to a pharmaceutical, which has the properties to deposit the radioisotope in the organ of concern for a patient.
• External radiation detectors are used to determine abnormalities in the organ.
• Thyroid scan and lung function tests are examples.
WNU-SI 2012 Oxford - UK
Tracer techniques
• Different parts of the human body absorb different elements but do not discriminate between different isotopes.
• In tracer techniques a radioactive isotope, such as iodine, is injected.
• The signals coming from the resulting radiation then give an image of the area where the isotope was absorbed.
• Usually isotopes of a relatively short half-life, of the order of minutes or days, are used to minimize long-term radiation damage.
Photo taken from Alan
Walter presentation
WNU-SI 2012 Oxford - UK
Radiochemistry
• Medical isotopes
separated under sterile
conditions
• Radiation dose to
operator must be
minimized
• Must be completed
quickly (less than one
half-life)
WNU-SI 2012 Oxford - UK
Sources of radioisotopes
Cyclotron Research Reactor
Use charged particles Use neutral particles
Produce short lived isotopes Produce longer lived isotopes
neutron deficient nuclei neutron rich nuclei
Cyclotrons vs. Reactors
WNU-SI 2012 Oxford - UK
Mo-99 from reactors
• Mo-99 is the most “in demand” medical isotope
• Mo-99 is shipped around (66 hrs half life)
• Its “decay product” Technetium-99m is used as
tracer
• Comes “easily” from a handful of existing,
publicly funded nuclear research reactors
• Reactors are getting old
WNU-SI 2012 Oxford - UK
Crisis of 99Mo
• 30 million examinations/year rely on 99Tc
• Worldwide production of 100 kilo curies per
year produced at aging nuclear reactors – BR2 Belgium
– National Research Universal (NRU) Reactor Canada
(50%)
– OSIRIS France
– HFR Netherlands (40%)
– SAFARI-1 South Africa
• Canadian NRU was off for repairs middle of
2009 to August 2010, Netherlands down for
repairs
• Almost 90% of world Mo supplied by the 2
closed reactors
WNU-SI 2012 Oxford - UK
Effect of 99Mo Crisis
• The price of Molybdenum-99 rose considerably
during the crisis, causing some anxiety among
buyers.
• The two major reactors are now back in operation.
• IAEA helps to close radioisotope production gap.
• Canadian Light Source (CLS) started a project to
explore the technical and economic feasibility of
using electron linear accelerator to produce Mo-99,
the “parent isotope” of Tc-99m.
WNU-SI 2012 Oxford - UK
Positron Emission Tomography (PET)
• PET (positron emission tomography)
scans involve the injection into the
body of an isotope which decays by
positron emission.
• When this positron encounters an
electron they annihilate each other,
emitting two photons.
• The energy and path of these photons
leaving the body can then be used to
give an accurate picture of the area
where the isotope was absorbed.
Positron Emission Tomography (PET)
J. Long, “The Science Creative Quarterly”,scq.ubc.ca
Cyclotron
Radiochemistry
WNU-SI 2012 Oxford - UK
PET
• When a pair of detectors detects
simultaneously one 511keV photon
each, a positron must have annihilated
on a straight line connecting those two
detectors – the so called line of response.
• The multitude of all these lines of
response is used to calculate a slice
image in a certain plane.
• produces a three-dimensional image or
picture of functional processes in the
body
WNU-SI 2012 Oxford - UK
PET Applications
• Oncology:
– Thyroid
– Sarcoma
– Lung
– Melanoma
– Lymphoma
– Head & neck
– Breast
• Neurological Applications:
– Parkinson’s, Alzheimer’s, Addiction
[11C] FE-CIT
Normal Subject
Parkinson’s disease
Courtesy HSR MILANO
PET functional receptor imaging
WNU-SI 2010 Oxford - UK
PET Isotopes
Nuclide Half-life Tracer Application
O-15 2 mins Water Cerebral blood flow
C-11 20 mins Methionine Tumour protein synthesis
N-13 10 mins Ammonia Myocardial blood flow
F-18 110 mins FDG Glucose metabolism
Ga-68 68 min DOTANOC Neuroendocrine imaging
Rb-82 72 secs Rb-82 Myocardial perfusion
WNU-SI 2010 Oxford - UK
• Most widely used PET tracer
• Glucose utilization allows assessment of glucose
metabolism in the heart, lungs, and the brain
• Taken up readily by most tumours
• Must be completed quickly (less
than one half-life)
FDG (Fludeoxyglucose 18F)
Mammography PET (PEM)
• Clear Crystal Collaboration (CCC) at CERN working on a dedicated PET for mammography; the Clear PEM.
• The aim is to be able to detect small tumours with a diameter of 1mm to 2mm in the breast and axilla region.
• Many advantages of PEM over x-ray mammography and whole body PETs
• PEM currently employed in hospitals (such as CHU Hopital Nord Marseille, France).
• Since tumour specific pharmaceuticals are used, the probability of false diagnosis due to the presence of inflammation, is reduced considerably.
WNU-SI 2012 Oxford - UK
PET/CT
• Combines the functional information with the
anatomical detail
• Images from both devices are superimposed (co
registered).
• Higher diagnostic accuracy than PET or CT
alone
• An emerging imaging
technology, not yet available is
PET/MRI.
WNU-SI 2012 Oxford - UK
Accelerators for all stages
• Isotope production
• Treatment therapy
Types of Accelerators
• Cyclotrons
• Syncrotrons
• Linacs
WNU-SI 2012 Oxford - UK
Low-energy cyclotrons for production of radionuclides for medical diagnostics
Medium-energy cyclotrons and synchrotrons for hadron therapy with protons (250 MeV) or light ion beams (400 MeV/u 12C-ions)
Electron Linacs for conventional radiation therapy, including advanced modalities:
•Cyberknife •IntraOperative RT (IORT) •Intensity Modulated RT
Three classes of medical accelerators
WNU-SI 2012 Oxford - UK
Cyclotrons used in medicine
• Baby Cyclotrons (< 18 MeV) in-house facility
• Mainly used for production of short-lived positron emitters
like 18F, 11C, 13N, 15O.
• Medium Energy Cyclotrons (< 40 MeV), centralised
facility
• Majority of the cyclotron produced isotopes are produced
using such machine viz, 123I, 201Tl, 67Ga, 68Ga, 103Pd etc.
• High Energy Cyclotrons (above 40 MeV), centralised
facilities and research institutions: Used for production of
few radioisotopes requiring high energy for production viz, 67Cu, 82Sr, 211At…
WNU-SI 2012 Oxford - UK
Baby Cyclotrons
• Accelerated protons
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Medium energy cyclotrons
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High-energy cyclotrons
• IBA‟s ARRONAX in
Nantes
• 4 Particles: H- / D- / He2+/
HH+
• Variable energy: 15 MeV-
70 MeV
WNU-SI 2012 Oxford - UK
Varian Clinac 1800 installed in the S. Anna Hospital in Como (Italy)
Medical accelerators: electron linac
WNU-SI 2012 Oxford - UK
Radiation and electron therapy
• Radiation is used to destroy
tumors present in an organ.
• Electrons or Cobalt-60 sealed
source are generally used for the
high activity.
• A mechanical device moves the
source to an opening in a
collimator which projects a beam
of photons used for treatment.
CyberKnife system is a method of delivering radiotherapy, with the intention of targeting treatment more accurately than standard radiotherapy.
http://www.accuray.com/Products/Cyberknife/index.aspx
6 MV Linac mounted on a robotic arm
CyberKnife (CK) Robotic Surgery System
It is a highly precise, image guided radiation
therapy delivery system capable of taking care
of the motion during treatment.
Brachytherapy
• Brachytherapy represents an effective
treatment option for many types of
cancer. A source is placed inside or next
to the area requiring treatment.
• Tumours can be treated with very high
doses of localised radiation, whilst
reducing the probability of unnecessary
damage to surrounding healthy tissues.
• In some cases radioactive seeds of < 1
mm are injected into the tumour area.
• can be used alone or in combination
with other therapies.
WNU-SI 2012 Oxford - UK
Protons and ions spare healthy
tissues
• Unlike photons or electrons,
proton beams deposit most of their
energy at the end of their paths in
the so-called Bragg peak.
• Hence, targeting deep-seated
tumours, close to sensitive organs,
with much reduced risk to
surrounding healthy tissue.
• benefit of proton and heavy-ion
therapy is that the beams can be
"tuned" to deliver a high dose of
energy at a precise location
WNU-SI 2012 Oxford - UK
Proton Therapy
• As well as an accelerator, a
gantry is required; this is a
massive structure that allows
directing the beam to the
tumour from any direction.
• It carries the final section of
the beam line and the beam
spreading ‘nozzle’
WNU-SI 2012 Oxford - UK
Therapy with carbon ions
• Carbon allows extremely precise targeting of the
tumour.
• lighter particles such as protons, whilst
depositing their energy in the Bragg peak, cause
far fewer double-strand breaks than heavier
ones like carbon.
• Tumours eligible for carbon ion radiotherapy so
far are: skull base tumours and tumours close to
the spinal chord.
WNU-SI 2012 Oxford - UK
Antiproton Cancer Therapy
• Researchers at CERN found that antiproton, can effectively treat
cancer.
• Antiprotons strip electrons off atoms in cells, causing ionization
and killing the cell they are in.
• A proton beam could also be used for ionization but when
antiproton beam eventually come to a stop at the focus, the
annihilation of both particles will release a huge amount of energy
(in the context of a single cell)....which is much more effective at
killing selected cells than simple ionization.
• Scientists estimate that routine clinical application of matter-
antimatter annihilation to cancer treatment should be a reality in
10-15 years.
WNU-SI 2012 Oxford - UK
Sterilization
• Medical equipment and Blood
• Sterilization by gamma irradiators or accelerators.
WNU-SI 2012 Oxford - UK
Conclusions
• Radiotherapy is a proof that the damaging effect of
radiation has itself been of great use.
• New isotope production and separation techniques are
needed to provide a steady supply of medical isotopes.
• Accelerators may solve the technetium crisis.
• Automation, robotics, and technology are necessary
aspects.
• Molecular imaging is enhancing health care by
providing early detection and better treatment of
tumors with less side effects on healthy tissue.
WNU-SI 2012 Oxford - UK
Takeaway points
• The progress in the field of radiation applications is not only
driven by advancement of nuclear and radiation physics but also
by the development of technology.
• Better planning, research and cooperation worldwide are
required to avoid future radioisotope production crisis such as
Mo-99.
• What seemed to be pure or basic science research in the past have
had large impact on applications of medical imaging such as ion
beam therapy.
• Research is required to find techniques to reduce the damaging
effects on healthy cells and target diseased cells more effectively.
WNU-SI 2012 Oxford - UK
Issues for consideration
• Cyclotrons versus research reactors for isotope
production.
• Cyclotrons versus synchrotrons for hadron
therapy.
• Dose accuracy and dosimetry: Radiation
protection for workers and patients
• Cost of nuclear medicine!
WNU-SI 2012 Oxford - UK
Thank you for your attention
ilham@qu.edu.qa
Questions?