APPENDIX 4
Memorandum from the British Chapter of
the International Society of Magnetic Resonance in Medicine
I am writing on behalf of the British Chapter
of the International Society of Magnetic Resonance in Medicine
to endorse the Joint Submission forwarded to you by Dr Stephen
Keevil, on behalf of a number of Scientific and Professional bodies.
This details many aspects of the development of policy regarding
occupational exposure to Magnetic Resonance devices.
I would like to note that much of the basic
research and early development underlying this major medical diagnostic
resource occurred in Britain. In the early stages of introducing
this new instrumentation into clinical use, the NRPB developed,
in close consultation with the magnetic resonance (MR) community,
some very useful guidance that stood the field in good stead for
many years. This particularly concerned exposure of patients and
volunteers, but also helped define issues that might be of concern
to staff. Quite rightly at that time it was conservative, and
limits were set at precautionary levels. In that and subsequent
revisions it included guidance that balanced benefit against risk,
and dealt with substantial health effects that might be damaging
to a patient's health, rather than with the emphasis of the current
European Physical Agents Directive on effects that give rise to
perceived sensations, with no evidence that these lead to health
effects.
Unfortunately, as you will see from the Joint
Submission, there has been very little active consultation with
the MR community in the UK in the preparation of these new occupational
standards and legislation. This has resulted in a Directive with
limits based on considerations of phosphene induction providing
a model for adverse effects on the nervous system. Such a perceived
effect does not, however, equate with any short or long term harm
to the individuals. At higher exposure levels a better characterised
effect, peripheral nerve stimulation (PNS), has been observed
in many patients and volunteers. Even though the threshold for
PNS occurs at current densities some 100 times greater than the
limits in the Directive, the sensations can be acceptable to both
volunteers and patients, and, again, are not known to result in
any long term effects. Staff performing interventional procedures
have been able to perform delicate motor tasks in the presence
of the switched fields, for the benefit of patients, and prohibiting
such tasks will have a range of detrimental effects for both patients
and staff.
With this Directive being enforced, interventional
procedures now being employed increasingly under MRI control would
need to be substituted by the older techniques using X-ray monitoring,
which deliver a radiation dose to both patients and staff. For
staff, who perform repeated procedures, these doses are cumulative.
While in the regulations governing the use of radiation, there
is an appreciation of benefit to society that can be balanced
against potential harm to the worker, similar considerations do
not appear to apply to non-ionising radiations, where the potential
hazards are much lower, albeit less well documented. Thus in order
to reduce a non-documented potential risk from non-ionising radiation,
both staff and patients will suffer an increased radiation dose,
contrary to the general obligation to reduce individual and population
radiation doses wherever possible. It is a matter of concern that
none of the bodies involved in preparing either safety recommendations
or legislation appear to have any obligation to consider the balance
of personal risk against benefit to society.
The Directive will prohibit staff supporting
patients (often anxious individuals or children), and anaesthetists
supervising patients (often children) who need to be sedated during
scanning from performing these operations close to the scanner,
which could compromise the scanning procedure, or observation
and monitoring of the sedated patient.
The Directive implements a concept of health
for the worker that is absolute (based on World Health Organisation
definitions), and deals only with short term perceived effects
without consideration of the worker's ability to balance these
effects against the value of the task undertaken. It also takes
no account of the social benefit of the task, and a balance of
the individual's exposure and society's benefit. In health employment
it is common to accept certain hazards, whilst controlling these
very carefully, for the benefit of the individuals treated.
Interventional use of MR is a growing area that
has potential benefit in a range of diseases, where the detailed
local anatomy, the potential to obtain information on the functional
status of tissues, and the lack of ionising radiation exposure
offer obvious benefits. While much emphasis is currently on vascular
techniques, the rapid development of new scanner technology aiding
access is likely to lead to a wider range of operative procedures,
biopsies, and minimally invasive therapies, all under the interactive
control of a skilled operator. It is unlikely that automated approaches
to these interventions will replace direct manipulation close
to the magnet for some considerable period. Prohibiting these
developments will adversely affect health research and practice
in the UK.
It is important to record that the magnetic
resonance community has a major commitment to the safety of all
involved in the use of magnetic resonance. This is effected through
scientific meetings and publications, identifying good practice,
and participating in the development of guidance, standards and
regulations. Based upon our experience of staff and patient exposure,
we feel that the Directive will limit the benefits of this technology,
with no evident staff benefit.
January 2006
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