300 / 536
ordertomakeiteasiertomergefunctionalandmorphological
images, hybrid appliances have beendeveloped: Positron-
EmittingTomography(PET)scannersarenowsystematically
coupledwith aCT scanner (PET-CT) and gamma-cameras
are equipped with a CT scanner (SPECT-CT).
2.1.2
In vitro
diagnosis
This is a medical biology technique for assaying certain
compounds contained in biological fluid samples taken
fromthepatient, suchas hormones, drugs, tumourmarkers,
etc., and it does not involve administering radionuclides
to the patients. The technique uses assay methods
based on immunological reactions (antigen-antibody
reactions labelled with iodine-125), hence the name RIA
(RadioimmunologyAssay). The activities contained in the
analysiskitsdesignedforaseriesofassaysdonotexceedafew
thousandbecquerels (kBq). Radioimmunology is currently
challengedby techniqueswhichmakenouseof radioactivity,
such as immuno-enzymology and chemiluminescence.
A few techniques use other radionuclides such as tritium
or carbon-14. Here again the activity levels involved are
of the order of the kBq.
2.1.3 Targeted internal radiotherapy
Internal radiotherapy aims to administer a
radiopharmaceutical emitting ionising radiation, which
will deliver a high dose to a target organ for curative or
remedial purposes. Two areas of therapeutic application
of nuclear medicine can be identified: oncology and non-
oncological conditions (treatment of hyperthyroidism,
synoviorthesis).
Several types of cancer treatment can be identified:
•
systemic treatments (thyroid cancer by iodine-131,
non-Hodgkin lymphoma by monoclonal antibodies
marked with yttrium-90, prostate cancer with bone
metastases by radium-223, etc.);
•
treatments administered by selective routes (treatment
of liver cancers by administering microspheres marked
with yttrium-90 into a hepatic artery through a
catheter).
Some treatments require patients to be hospitalised for
several days in specially fitted-out rooms in the nuclear
medicine unit to ensure the radiation protection of the
personnel, of people visiting the patients and of the
environment. The radiological protection of these rooms
is adapted to the nature of the radiation emitted by the
radionuclides, and the contaminated urine of the patients
is collected in tanks. This is particularly the case with
the post-surgical treatment of certain thyroid cancers.
The treatments are performed by administering varying
activities of iodine-131 (1.1 GBq, 4 GBq, 5.5 GBq).
Other treatments can be on an out-patient basis.
Examples include administering iodine-131 to treat
hyperthyroidism, strontium-89 or samarium-153 for
painful bone metastases, and radium-223 for prostate
cancer with bone metastases. Joints can also be treated
using colloids labelled with yttrium-90, erbium-169 or
rhenium-186. Finally, radioimmunotherapy can be used
to treat certain lymphomas using yttrium-90 labelled
antibodies.
2.1.4 Biomedical research in nuclearmedicine
Biomedical research in nuclear medicine has been
particularly dynamic in the last few years: protocols are
regularly developed for new radionuclides and vectors.
These innovations mainly concern:
•
Positron Emission Tomography (PET) with fluorine-18,
gallium-68 and rubidium-82;
•
targeted internal radiotherapy with radium-223,
microspheres labelledwith yttrium-90, vectors labelled
with yttrium-90 or lutetium-177.
The use of new radiopharmaceuticals means that the
radiation protection requirements associated with their
handling must be integrated as early as possible in the
process. Indeed, given the activity levels involved, the
characteristics of certain radionuclides and the preparations
to produce, appropriatemeasures must be implemented
with regard to operator exposure and environmental
impact.
TYPE OF EXAMINATION
RADIONUCLEIDES USED
Thyroid metabolism
Iodine-123, Technetium-99m
Myocardial perfusion
Thallium-201, Technetium-99m, Rubidium-82
Lung perfusion
Technetium-99m
Lung ventilation
Technetium-99m, Krypton-81m,
Osteo-articular process
Technetium-99m, Fluorine-18
Oncology - search for metastasis
Technetium-99m, Fluorine-18, Gallium-68
Neurology
Technetium-99m, Fluorine-18
TABLE 1:
Some of the main radionuclides used in the various
in vivo
nuclear medicine examinations
300
CHAPTER 09:
MEDICAL USES OF IONISING RADIATION
ASN report on the state of nuclear safety and radiation protection in France in 2015