Biomedical Engineering Reference
In-Depth Information
first started to work as a medical physicist, due to lack of space, I was
assigned as my “office” a counter top in one corner of the control
room of one of the treatment machines. This turned out to be an
invaluable experience, giving me the chance to observe the routine
practice of radiotherapy on a daily basis. I recall seeing on two
occasions the radiation therapist realizing that she had just treated a
patient with another patient's treatment parameters. This was the
time in which computer programs to perform the so-called record and
verify function (having the computer monitor the machine settings
and not allow treatment to proceed unless they matched the prescribed
parameters within a defined tolerance) were just being introduced. I
recall the amazed and concerned reaction to the study by Chung-Bin
and his colleagues (Kartha
et al
., 1975) who, using the computer as a
silent monitor of treatments, found that the mis-setting of treatment
parameters occurred at an approximately 3% rate and that more than
two-thirds of the patients monitored had at least one error at some
stage during the full course of their treatment. This ushered in the use
use of record and verify systems. However, many “old hands” (and
probably many new ones) have reservations about these systems, too
(Klein
et al
., 2005). They assure that what is done is what the
computer data base says should be done. But, this also provides an
opportunity to do the wrong thing consistently, every time.
The more we become mechanized, the greater is the need for human
oversight and the exercise of “common sense” - a quality that has not
yet become one of the computer's skills. In my view, it is essential
that both the clinician and the physicist who planned the treatment
attend the first treatment and periodically thereafter, to help ensure
that what was planned is what is being delivered. The importance of
quality assurance is underlined in Chapter 12. To an extent, quality is
supported by instrumentation of various sorts. However, nothing can
replace the eyes and brains of the experts
radiation therapists,
dosimetrists, physicists, and radiation oncologists
−
−
continually
monitoring what is done in practice.
Ongoing patient evaluation
As is mentioned in Chapter 7, an important source of uncertainty is
the possibility of unappreciated changes in the patient's condition
and geometry during the generally several weeks of therapy. Thus
periodic checks are generally necessary, the nature of which depend
on the clinical situation. These could extend to periodic rescanning of
