Airborne I-131 from therapy patients

[jtowson@nucmed.rpa.cs.nsw.gov.au (Jocelyn Towson)]

Milton McLain wrote
>
>Be aware that thyroid ablation therapy patients may also emit significant
>quantities of I-131 via the  respiratory path.

The respiratory pathway may not be such a problem in hospital rooms.  Some
time ago we looked for airborne I-131 during two consecutive I-131
inpatient treatments, and found nothing of significance for inhalation by
ward staff [especially as nurses spend VERY little time in the room with
these patients].

We sampled the air above the bedhead and the toilet.  We also sampled the
air in a glove box while the I-131 capsule packaging was opened, and above
a urine 'spill' in a glove box.  We found:

Administered dose to patient                    4 GBq           2x4 GBq

Unpacking in glovebox   trapped activity        1300 Bq/4min     7000 Bq/10min

1m above bedhead        air concentration       27 Bq/m3/48h     76 Bq/m3/40h

50cm above toilet       air concentration       1.9 Bq/m3/72h    4.0 Bq/m3/67h

urine spill/glovebox    urine activity          7.4 MBq/30mL     1.85 MBq/25mL
                        air activity            270 Bq/3h        110 Bq/3h

This was all very reassuring for nursing staff, though I must say I was
surprised by the low readings in the bathroom (admittedly very well
ventilated).
Of course, the exhaled I-131 must go somewhere: on a rough calculation, the
patient who received 8 GBq would have exhaled up to 4 kBq over a 2 day
period, and some of this activity would have settled on surfaces within the
room.

Incidentally, we routinely unpack our capsules in a fume hood.

There is a paper on contamination of others in the hyperthyroid patient's
household:
Buchan and Brindle, Radioiodine therapy to outpatients - the contamination
hazard.  Br J Radiol 1970;43:479-482.
For a detailed study of contamination in the hospital room, see:
Ibis E et al.  Iodine-131 contamination from thyroid cancer patients.  J
Nucl Med 1992;33:2110-2115.
This is followed (pp 2116-7) by an Editorial by W Beierwaltes which puts
the whole issue in perspective.

Regards,
Jocelyn Towson





Jocelyn Towson, RSO
Dept of PET & Nuclear Medicine
Royal Prince Alfred Hospital
Camperdown, NSW 2050
Australia

tel [national]  02 9515 8011    [international] 61 2 9515 8011
fax [national]  02 9515 6381    [international] 61 2 9515 6381
email   jtowson@nucmed.rpa.cs.nsw.gov.au