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Keywords:
Radiation physics, Radioprotection / Radiation dose, Interventional vascular, Experimental, Dosimetry, Technical aspects, Radioembolisation, Dosimetric comparison, Occupational / Environmental hazards
Authors:
M. W. M. Law, K. K. Wong, W. K. Tso, H. F. V. Lee, M. Y. Luk; Hong Kong/HK
DOI:
10.1594/ecr2015/B-1248
Results
Table 1 shows the dose rates,
normalised by the patient administered 90Y microsphere radioactivity,
measured at the position of the interventional radiologist and at 10 cm above the patient abdomen with and without being covered by the lead lined blanket.
There has been a dose reduction of a factor of > 2 with the use of the blanket.
At the radiologist position during pressing the puncture site after radioembolisation,
the average dose rate has been measured as 1.32 μSv/(hr GBq).
The average infused Y90 radioactivity for our patients is 2.1 GBq.
The radiologist thus received 0.92 μSv during pressing the puncture site on his hands and arms that are not radiation shielded by lead apron.
Since the radiologist wears a lead apron of the same lead equivalence of the lead lined a blanket,
he actually would receive a body dose of 0.4 μSv under his lead apron due to the Bremsstrahlung radiation from the patient after radioembolisation,
comparable to the hourly background radiation rate of about 0.3 μSv in our institution area.
The same radiation dose measurements have been calculated for nurses and porters nursing and transporting the patient respectively after 90Y radioembolisation treatment with the use of the blanket (Table 2),
showing occupational dose is indeed very minimal.
While radiation safety considerations in 90Y radioembolisation have been described in detail for patient dosimetry accuracy,
interventional radiology room radiation contamination prevention and scenarios for radioemolised patients in contact with their family [5],
there is not much available in literature for dose reduction for medical professionals involved in the procedure.
Using a blanket type lead apron of 0.5 mm lead equivalence with size and weight tolerable to patient comfort,
it has been shown that the Bremsstrahlung radiation emitted from patient can be reduced by more than a factor of 2 in order to comply with the ALARA principle in radiation protection.
This dose reduction is useful for the concern to administer higher 90Y radioactivity for better patient treatment efficacy.
Generally,
there are local recommendations and regulations regarding the safety use of unsealed radioactive substance in hospitalization and on patient release.
Our institutional radiation safety regulation requires 90Y treated patients of greater than 1.5 GBq should be accommodated in a single room ideally with private toilet facility.
Sometimes this cannot be achieved due to insufficient isolation ward or there is no such facility in some hospitals but 90Y radioemboliation has to be performed.
We attempt to solve this resource problem by allocating the 90Y treated patient at a corner bed in a common ward. To justify that other patients at the vicinity of the 90Y radioemboised patient would be exposed unnecessarily,
the lead lined blanket is used to cover the radiolembolised patient abdomen.
The exposure rate at 1m is calculated to be 1 μSv/hr (assumed 2.1 GBq infusion).
If the distance between the 90Y patient and the patient adjacent to him is maintained at 2 m,
the exposure rate would then be 0.25 μSv/hr which is about the same background radiation level in our institution area.
In other words,
the 90Y patient would not expose unnecessarily radiation exposure to the next patient if a lead lined blanket and distance as far as 2 m are followed.
Indeed,
90Y microspheres treated patients represent an even lower radiation safety risk for nearby individuals because there is no biologic elimination of 90Y as the microspheres remain fixed in liver,
tumor and lung [4-5].
There are two types of 90Y microspheres commercially available,
namely glass microspheres and resin microspheres [6-7].
The glass spheres are not known to be present in any body fluid,
whereas trace amounts of 90Y radioactivity may be excreted in the urine of resin microsphere treated patients for the first 24 hours.
Therefore for glass microsphere treated patients,
they can use the toilet facility in the common ward as usual because their urine would not contain any radioactive content.
For resin microsphere treated patients,
they are advised to flush the toilet twice after use.
In other words,
radioembolised patients can use common toilet facility as other non-radiation patients do.