Which protection against radiation from new protocols of internal dosimetry by yttrium-90 AUBERT Bernard*, GUILABERT Nadine°, LAMON Annick* and RICARD Marcel* *Physics Department and °Nuclear Medicine Department Institut Gustave-Roussy, Villejuif, France 6th European ALARA Network Workshop - Madrid, 23-25/10/2002

Introduction Within the field of the therapeutic applications in Nuclear Medicine, new protocols have been proposed these last years based on the use of therapeutic agents labelled with yttrium-90 : Octreother° (somatostatine analogue) on patients with neuro-endocrines tumors. Zevalin* for treatment by radio immunotherapy of non Hodgkiniens lymphoma. ° Mallinckrodt * Schering

Yttrium 90 - ( 100 %) T1/2 = 64.1 hours Rmax (air ) : 9 m Rmax (water) : 11 mm R90 (water) : 5.3 mm

Introduction iode 131 : beta emitter (Emax  0.6 MeV) used since more than 50 years for treatment of thyroid diseases and gamma emitter (Eprincipal = 0.365 MeV): Radiation protection procedures are well known even for high activities ( 8 GBq). Other used beta emitters: erbium 169 (Emax  0.35 MeV) rhenium 186 (Emax  1 MeV) Applications not very wide spread and using low activity ( 0.1 GBq).

Aim of the study Recommandations for radiation protection for beta emitters are very general: 10 mm of PMMA are enough to stop any beta emission, PMMA is preferable to lead (or tungsten) because the bremsstrahlung emission is less important. Systematic analysis of exposure situations at the beginning, or before starting, clinical protocols with yttrium-90 by: procedure analysis, choice of radiation protection material, and, additional dosimetric survey.

71.1 µSv.h-1.GBq-1 43.5 Sv.h-1.GBq-1 Radiation Protection Dosimetry, Vol. 98, No 1, 2002

Additional personal dosimeter TLD chips Electronic dosimeter

OCTREOTHER protocol Solution of 5.4 GBq (145 mCi) of 90Y in 86 mL Activity measured with a dose calibartor Radioactive vial placed inside the injection container

OCTREOTHER protocol Installation of the line Connection of the line to the patient Installation of the line in the electrical pump Injection of 4.44 GBq (120 mCi) by perfusion during 12 to 15 minutes

OCTREOTHER protocol Surveillance of injection Collection of vial and line and management of radioactive wastes Surveillance and patient care during 2 days

OCTREOTHER protocol Exposure measurements with portable ionisation chamber Close to the delivery container and injection container (at  5 cm):  300 µSv/h. at 1 m from containers:  2 à 3 µSv/h Before injection : After injection at 1 m from patient:  30 à 40 µSv/h near the second pump (for amino acides) managed by the nurse:  120 µSv/h

Finger exposure in mSv/injection TLD measurement - mean value (SD) OCTREOTHER protocol Finger exposure in mSv/injection TLD measurement - mean value (SD) Localization Technologist 1st injection right thumb 18.0 right forefinger 23.5 left foerfinger 14.5 left thumb 14.0 After new procedure Technologist (15 inject.) Nurse 2.81 (2.13) 0.40 (0.56) 2.36 (2.58) 0.28 (0.50) 2.12 (0.74) 0.42 (0.58) 1.6 0.20 (0.32)

(dose rate at 1 m: 1.5 to 2 µSv/h). OCTREOTHER protocol NaI(Tl) probe Bremsstrahlung spectrum from patient one day after injection of 4.44 GBq of 90Y (dose rate at 1 m: 1.5 to 2 µSv/h).

OCTREOTHER protocol Due to the importance of low energy components in the bremsstrahlung spectrum (max at  80 keV and very few photons above 300 keV), a protective apron (0.5 mm Pb equivalent ) is efficient. Measurement with portable ionization chamber (RAM DA 2000) Patient 1 (at 50 cm) Patient 2 (at 65 cm) without apron 360 59.1 with apron 4.8 1.0 (µSv/h)

ZEVALIN protocol Radionuclide preparation. Injection of 1.11 GBq (30 mCi) with an automatic syringe pump during 10 minutes. Surveillance of injection. Collection of vial and line, and management of radioactive wastes. Surveillance and patient care during 2 days.

ZEVALIN protocol Radiopharmaceutical preparation Solution of 1.85 GBq (50 mCi) of 90Y in 2 mL. Measurement of activity with a dose calibrator. Removal of 90Y from delivery vial and transfer into preparation vial. Filling of infusion syringe.

ZEVALIN protocol Efficiency of vial shield Wall in lead glass and size adaptator in PMMA Close to the shielding:  70 µSv.h-1.GBq-1

ZEVALIN protocol Syringe shield Tungsten  5 mm PMMA 5 and 10 mm

ZEVALIN protocol Efficiency of syringe shield - TLD measurements This study 5.5 ZIMMER* study 11.2 Contact syringe (mSv.h-1.MBq-1) Contact with syringe shield (µSv.h-1.MBq-1) PMMA-5 mm PMMA-10 mm tungsten-5 mm 16 2.7 1.4 PMMA PMMA/Pb tungsten 2.8 1.7 2.4 * Zimmer et al., abstract n° 164, J.N.M. abstract book, may 2002

Conclusions This radiation protection study concerning new therapeutic protocols with 90Y confirmed: the need for studies related to working conditions before the starting of new clinical protocols, the interest of additional dosimetry at the most exposed regions (fingers), the interest of operational dosimetry for the direct information of the operator,

Conclusions the need for electronic dosemeters suited to the situation, i.e. sensitive to the beta radiation, the need to collaborate with the manufacturer to increase its awareness of this problem in order to inform users before starting the clinical protocol, the contribution of a radiation protection culture in a hospital where the human and material means are available.