Re: Dose estimates when dosimetry is lost/damaged

[Kent Lambert <lambert@allegheny.edu>]

Sandy Perle wrote:
> 
> The practice of dose estimates was
> to conduct a dose investigation based on survey data, secondary
> dosimetry, dosimetry results from others who worked with the
> individual in question and most importantly, an interview with the
> individual. 

So a interventional fluoroscopist loses his/her film badge.  You look up 
each case that the individual was involved in (50 or so), find the 
cumulative fluoro on time, and sum the times for the month.  Based on survey 
data from the annual medical physics QA on the unit determine the dose to an 
individual at 1 meter from the patient.  A time and motion study is 
performed for each of the various procedures done during the month to 
determine the times and distances, apply inverse square correction and 
determine an estimated dose. There is no secondary dosimetry.  You then find 
another fluoroscopist, look up all of the cases s/he performed, sum the 
cumulative fluoro on time and apply the ratio of exposure times to the known 
dosimetry results to confirm the estimated dose.  

Explain to me how this estimate is going to be any more accurate than 
determining if the individual's workload was similar to previous months and 
then using the previous exposure to estimate dose.  Note that the dose to 
the fluoroscopist is more than an order of magnitude different than the 
nurse that is also in the fluoro room, i.e., any error in the time and 
motion study causes big errors in the dose estimate.  

And you do a similar evaluation for each nuclear medicine technician, nurse 
handling a brachytherapy or radiopharmaceutical therapy patient, 
anesthesiologist in OR rooms where C-arms are used (e.g., hip replacement), 
researcher using 1-10 mCi of P-32 are used, etc.  And as I recall from some 
of your previous posts, you believe that EVERY worker at a 
university/hospital should be monitored (Justified because of the potential 
for litigation from individuals who received a few millirem lifetime dose). 
So when the loading dock worker who handles the radioactive material package 
loses his/her badge the same investigation is conducted.  

I'm not saying that an investigation is not warranted, but if the 
investigation asks, (a) Was your exposure significantly different than 
previous months; (b) Did any unusual events or incidents occur which might 
affect your radiation dose; (c) Would it be fair to estimate your radiation 
dose based on the average of your radiation exposure over the last x months; 
and the answers are No, No, Yes; then what is the problem?

On a positive note, you have come up with a way to fill the help wanted 
section of the HPS Newsletter.

> 1. Isn't it the responsibility of the individual who is monitored to
> be cognizant of their radiation exposure?

Not really, the cardiologist is responsible for diagnosing heart disease, 
the nuclear medicine technician is responsible for obtaining a diagnostic 
quality image, a researcher is responsible for discovering a cure/cause for 
a disease, etc.
 
> 2. Isn't the RSO or whoever is accountable for the dosimetry program
> accountable as the caretaker of the individual's doses, to ensure
> that they are as accurate as possible, and if there is a question
> regarding an individual's dose, that they become an integral part of
> the investigation which results in a dose estimate to be assigned?

Sure, but this is not mutually exclusive with automatic assignment of dose 
estimates.  The individual's previous dose history should be a MAJOR factor 
in the exposure investigation and the dose estimation.  The automatic 
assignment of a dose estimate does not preclude an investigation.

> 3. IF a processor automatically assigns an estimate, automatically
> without any intervention from the customer, isn't this a liability
> issue, and could within all probablility, end up in litigation some
> time later?

Not really, since the formula for dose estimate is clearly stated, and the 
vendor allows the RSO to accept, reject, or alter the estimate.  And anyway, 
what does the client care about the processor's liability?

> 4. How is the individual notified that their dosimetry was damaged
> during processing, and that an estimate has been assigned? How are
> they informed of the methodology used to arrive at the dose estimate?

What difference does this make to the vendor?  The vendor is responsible for 
providing the contracted service, period.  Are you suggesting that the 
commercial dosimetry provider should conduct these investigations for the 
customer?  
 
> 5. How do the regulators look at a dose assigned without any
> intervention from the customer, especially without any documented
> investigation?

Again, the vendor is only providing an averaging service, the customer is 
responsible for accepting, rejecting or modifying the results.

> 6. The processor takes on a serious liability without a detailed
> audit trail which shows the chain of command of the dose assignment
> process ... if, there is this automatic dose estimation without any
> intervention from the customer, who I believe should be legally bound
> to defend the dose assigned, with the assistance of the processor.

See above argument.
 
> The policy I have implemented is as follows. ...

With all due respect, this is marketing and does not belong on RADSAFE.

-- 
Kent Lambert, CHP
lambert@allegheny.edu

Then again, I could be wrong.