Transcript VIII.2_1_Justification in NM

Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources
VIII.2. Medical Exposures in
Nuclear Medicine.
1. Justification
System of radiological protection
for medical exposure
VIII.2.1. Justification
2
System of radiological protection
for medical exposure

The system of radiological protection for
medical exposure has basically to do with the
general ethical principles of the health care
system
Ethics is the science of morality; the principles of proper
professional conduct concerning the rights and duties of the health
care professional, his patients, and his colleagues.*
*Webster’s New World, Medical Dictionary
VIII.2.1. Justification
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Principles Commonly Addressed
in any Ethical Theory
AUTONOMY
BENEFICIENCE
CONFIDENTIALITY
JUSTICE
TRUTH TELLING
INFORMED CONSENT
VIII.2.1. Justification
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Principles Commonly Addressed
in any Ethical Theory
AUTONOMY:



The right of the individual patient to make
decisions regarding personal medical care
The patient is to be given adequate
information about the alternatives so an
intelligent decision can be made
The health care worker is to respect the
decision of the patient.
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Principles Commonly Addressed
in any Ethical Theory
BENEFICIENCE
The duty of the health care worker to
perform those acts or administer care
that will be of benefit to the patient
 ALARA
 Responsibility of the staff to monitor the
patient.

VIII.2.1. Justification
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Principles Commonly Addressed
in any Ethical Theory
CONFIDENTIALITY
 The
legal right of privacy
 All
patient records are confidential
material
 The
“need to know”
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Principles Commonly Addressed
in any Ethical Theory
JUSTICE

All people are created equal and,
therefore, should be treated as equals

The right to receive medical care

Treat patients with the same level of
courtesy and respect
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Principles Commonly Addressed
in any Ethical Theory
TRUTH TELLING
The patient’s right to a truthful diagnosis
and prognosis
 It is the responsibility of the physician, not
the health care worker, to discuss the
patient's diagnosis and prognosis with the
patient

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Principles Commonly Addressed
in any Ethical Theory
INFORMED CONSENT

The patient must have adequate
information about the procedure in order to
be able to make an informed decision

Truth telling must be practiced in the
discussion of procedures with the patient

The patient must be allowed autonomy
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Justification of Medical Exposures
BSS, appendix II: “Medical exposures
should be justified by weighing the
diagnostic or therapeutic benefits they
produce against the radiation detriment
they might cause, taking into account the
benefits and risks of available alternative
techniques that do not involve medical
exposure.”
VIII.2.1. Justification
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JUSTIFICATION OF
MEDICAL EXPOSURE
Objective of
treatment/examination
Medical exposure
Radiation risks
VIII.2.1. Justification
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RADIATION RISKS IN
NUCLEAR MEDICINE
EXAMINATIONS
Examination
Radiopharmaceutical
Myocardium
Tl-201 chloride
Bone
Tc-99m MDP
Thyroid
Tc-99m pertechnetate
Lungs
Tc-99m MAA
Kidney clearance Cr-51 EDTA
VIII.2.1. Justification
Effective dose
(mSv)
23
3.6
1.1
0.9
0.01
Risk
(%)
0.12
0.018
0.006
0.005
0.00005
13
Risk of stochastic effects(%/ Sv)
20
Male
15
Embryo and fetus
Female
10
5
0
0
10
20
30
40
50
60
70
80
(age at exposure)
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Absorbed dose to the fetus
Examination
Bone (Tc99m)
Brain (CBF)
Lung (Tc99m-MAA)
Kidneys (MAG3)
Tumour or abscess (Ga-67 citrate)
Heart (Tc99m-MIBI)
Heart (Tl-201)
Thyroid (Tc99m)
Thyroid (I-131)
Kidney clearance (Cr-51-EDTA)
Activity
(MBq)
Dose to fetus
(mSv)
600
500
160
100
300
300
100
100
100
4
4
0.4
2
28
5
10
1
7
4
0.02
(Data from Russell, Stabin et al Radiation dose to the embryo/fetus from
radiopharmaceuticals Draft, 1997
VIII.2.1. Justification
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Absorbed dose to the fetus
0,3
I-131 iodide
Tc-99m-MAG3
mGy/MBq
0,2
0,1
0,0
Early
3 months
6 months
9 months
Pregnancy month
(Data from Russell, Stabin et al Radiation dose to the embryo/fetus from
radiopharmaceuticals Draft, 1997
VIII.2.1. Justification
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Risk of stochastic effects(%/ Sv)
20
The higher
Male risk for young people
as well as for the fetus must be
Female
considered
in the justification of
an examination. Special concern
should be given to:
•Children
•Pregnant women
15
10
5
0
0
10
20
30
40
50
60
70
80
(age at exposure)
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The justification of a practice

The decision to adopt or continue any human activity
involves a review of the benefits and disadvantages
of the possible options

E.g.: choosing between the use of nuclear medicine
or ultrasound or MR

Often, the radiation detriment will be only a small part
of the total detriment

Most of the assessments needed for the justification
of a practice are made on the basis of experience,
professional judgement, and common sense
VIII.2.1. Justification
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Three levels of justification
General level: The use of radiation in
medicine is accepted as doing more
good than harm
 Generic justification (specific procedure
with a specific objective: bone scan for
patients with ca prostate showing
relevant symptoms)
 Third level: the application of the
procedure to an individual patient

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Generic justification (I)

It is a matter for national professional bodies,
sometimes in conjunction with national regulatory
authorities

The exposures to staff (occupational) and to
members of the public should be taken into account

The possibility of accidental or unintended exposures
(potential exposure) should also be considered

The decisions should be reviewed from time to time
as new information becomes available
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Generic justification (II)

The resources in a country or region should
be considered (single detectors in renography
instead of gammacamera for economical
reasons)

The justification of diagnostic examinations
for which the benefit to the patient is not the
primary objective needs special consideration
(e.g. examinations for insurance purposes or
medical research)
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Justification for an individual
patient



To check that the required information is not
yet available
Once the procedure is generically justified, no
additional justification is needed for simple
diagnostic examinations e.g. determination of
kidney clearance or other laboratory
methods.
For complex procedures and therapy
individual justification by the nuclear medicine
specialist and the referring physician should
be done
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When radiation is the
therapeutic agent

If the medical practitioner in consultation
with the patient has decided that
radionuclide therapy is indicated, patient
protection is usually a secondary
concern
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JUSTIFICATION (BSS)
”II.6. Any radiological examination for occupational,
legal or health insurance purposes undertaken without
reference to clinical indications is deemed to be not
justified unless it is expected to provide useful
information on the health of the individual examined or
unless the specific type of examination is justified by
those requesting it in consultation with relevant
professional bodies.”
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Children (BSS II.17)
(e) administration of radionuclides to children for
diagnostic procedures be carried out only if
there is a strong clinical indication, and the
amount of activity administered be reduced
according to body weight, body surface area or
other appropriate criteria.
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BREASTFEEDING
Breastfeeding a baby should be
considered in the justification of
a nuclear medicine procedure of
the mother.
Normally, breastfeeding should not
exclude the mother from a justified
examination. The problem should
be solved by restrictions on the
continuing feeding (optimization)
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Nuclear Medicine (BSS II.17)

(c) administration of radionuclides for diagnostic or
radiotherapeutic procedures to women pregnant or
likely to be pregnant be avoided unless there are
strong clinical indications;
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Therapeutic Procedures (BSS II.18)


(c) administration of radionuclides for
therapeutic procedures to women who are
pregnant or likely to be pregnant or who are
nursing be avoided unless there are strong
clinical indications;
(d) any therapeutic procedure for pregnant
women be planned to deliver the minimum
dose to any embryo or foetus; and ….
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JUSTIFICATION & PREGNANCY



In some circumstances, the unborn child
may be at increased risk, which should be
considered in justification.
Prenatal doses from most properly done
diagnostic procedures present no measurably
increased risk of prenatal death,
malformation, mental impairment.
Higher doses such as those from therapeutic
procedures can result in significant fetal
harm.
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Radio-iodine therapy
As a rule, a pregnant woman should not be
treated with a radioactive substance unless
the therapy is required to save her life: in that
extremely rare event, the potential absorbed
dose and risk to the fetus should be estimated
and conveyed to the patient and the referring
physician. Considerations may include
terminating the pregnancy.
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Becoming pregnant after irradiation
• ICRP has recommended that a woman not become
pregnant until the potential fetal dose from
remaining radionuclides is less than 1 mGy.
• This is not usually a consideration except for
radiopharmaceuticals labelled with 59Fe (for
metabolism studies) or 75Se (for adrenal imaging).
• As a result of the long physical half-lives of these
radionuclides and their long residence times in the
body, it is recommended that pregnancy be avoided
for 6 and 12 months respectively.
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PREGNANCY AFTER
THERAPY
Radiopharmaceutical
All activities
up to (MBq)
Au-198 colloid
10000
I-131 iodide (thyroid ca)
5000
I-131 iodide (thyrotoxicosis)
800
I-131 MIBG
5000
P-32 phosphate
200
Sr-89 chloride
150
Y-90 colloid (arthritic joints) 400
Y-90 colloid (malignancy)
4000
VIII.2.1. Justification
Avoid pregnancy
(months)
2
4
4
4
3
24
0
1
32
Research on Pregnant
Patients
 Radiation
research
involving
pregnant
patients should
be discouraged
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Other factors to consider




Will the patient pose a risk to other persons
such as members of the family or general
public?
Is the patient scheduled for surgery or similar
intervention?
Is there a risk that the patient will die within a
short period of time?
Is there an increased risk that the patient
requires emergency treatment?
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Advise from BSS appendix II.28.

“In order to restrict the exposure of any members of
the household of a patient who has undergone a
therapeutic procedure with sealed or unsealed
radionuclides and members of the public, such a
patient shall not be discharged from hospital before
the activity of radioactive substances in the body falls
below the level specified in Schedule III, Table III-VI.
Written instructions to the patient concerning contact
with other persons and relevant precautions for
radiation protection shall be provided as necessary”.
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IAEA BSS (1996) App. II.28



BSS Schedule III, Table III-VI: Guidance level only
given for 131-I: Maximum activity for discharge
1100MBq
Other isotopes not mentioned
Legal limit values are still
applicable
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Also consider:

What happens if the patient requires
emergency treatment?


Surgery?
What happens if the patient dies?
Autopsies?
 Cremation?

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Other factors to consider

The other factors discussed should
generally not impose on the justification
of an examination or treatment of the
patient. The radiation protection
problems should be solved by
optimization of safety and a well trained
staff in case of emergencies.
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