Hard beta and gamma emissions of ¹²⁴I

Summary

Aim: The hard beta and gamma radiation of ¹²⁴I can cause high doses to PET/CT workers. In this study we tried to quantify this occupational exposure and to optimize radioprotection. Methods: Thin MCP-Ns thermoluminescent dosimeters suitable for measuring beta and gamma radiation were used for extremity dosimetry, active personal dosimeters for whole-body dosimetry. Extremity doses were determined during dispensing of ¹²⁴I and oral administration of the activity to the patient, the body dose during all phases of the PET/CT procedure. In addition, dose rates of vials and syringes as used in clinical practice were measured. The procedure for dispensing ¹²⁴I was optimized using newly developed shielding. Results: Skin dose rates up to 100 mSv/ min were measured when in contact with the manufacturer's vial containing 370 MBq of ¹²⁴I. For an unshielded 5 ml syringe the positron skin dose was about seven times the gamma dose. Before optimization of the preparation of ¹²⁴I, using an already reasonably safe technique, the highest mean skin dose caused by handling 370 MBq was 1.9 mSv (max. 4.4 mSv). After optimization the skin dose was below 0.2 mSv. Conclusion: The highly energetic positrons emitted by ¹²⁴I can cause high skin doses if radioprotection is poor. Under optimized conditions occupational doses are acceptable. Education of workers is of paramount importance.

Zusammenfassung

Ziel: Die hochenergetische Beta⁺- und Gammastrahlung von124I kann hohe Dosen für das PET/ CT-Personal bedeuten. In dieser Studie wurde die beruflich bedingte Exposition quantifiziert und die Strahlenprotektion optimiert. Methoden: Dünne MCP-Ns-Thermolumineszenzdosimeter wurden zur Messung von Beta⁺- und Gammastrahlung für die Extremitätendosimetrie, aktive Personendosimeter für die Ganzkörperdosimetrie eingesetzt. Extremitätendosimetrie wurde während des Abfüllens von 124I und oraler Applikation an den Patienten und die Ganzkörperdosis während der gesamten PET/CT-Untersuchung bestimmt. Zusätzlich wurden Dosisraten der genutzten Fläschchen und Spritzen gemessen. Das ¹²⁴I-Abfüllverfahren wurde mit Hilfe von speziell entwickelter Abschirmung optimiert. Ergebnisse: Hautdosisraten bis 100 mSv/min wurden bei Kontakt mit dem 370 MBq ¹²⁴I enthaltenden kommerziell verfügbaren Fläschchen gemessen. Eine nicht abgeschirmte 5-ml-Spritze resultierte in einer etwa siebenfachen Positronen-Hautdosis im Vergleich zur Gammadosis. Mit der als ausreichend vermuteten Prozedur vor Optimierung der ¹²⁴I-Abfüllung betrug die höchste mittlere Hautdosis beim Umgang mit 370 MBq ¹²⁴I 1,9 mSv (max. 4,4 mSv). Nach der Optimierung lag die Hautdosis unter 0,2 mSv. Schlussfolgerung: Die von ¹²⁴I emittierten, hochenergetischen Positronen können bei unzureichender Strahlenprotektion zu hohen Hautdosen führen. Unter optimierten Bedingungen sind die arbeitsbedingten Dosen akzeptabel. Entsprechende Ausbildung des Personals ist unentbehrlich.

Keywords

Occupational dosimetry - extremity dosimetry - ¹²⁴I - PET/CT - high-energy positrons

Schlüsselwörter

Berufliche Dosimetrie - Fingerdosimetrie - ¹²⁴I - PET/CT - hochenergetische Positronen

• References

• 1 Aubert B, Guilabert N, Lamon A, Richard M. Which protection against radiation for new protocols of internal radiotherapy by yttrium 90? Proceedings of the 6^th European ALARA Network Workshop. Occupational Exposure Optimisation in the Medical Field and Radiopharmaceutical Industry. Madrid: 23.-25. October 2002: 47-49.
• 2 Brasik N, Stadtmann H, Kindl P. The right choice: extremity dosemeter for different radiation fields. Radiat Prot Dosimetry 2007; 125: 331-334.
• 3 Capoccetti F, Criscuoli B, Rossi G. et al. The effectiveness of ¹²⁴I PET/CT in patients with differentiated thyroid cancer. Q J Nucl Med Mol Imaging 2009; 53: 536-545.
• 4 Carnicer A, Baechler S, Barth I. et al. Extremity exposure in diagnostic NM with ¹⁸F and ^99mTc labelled radiopharmaceuticals. Workshop on optimization of radiation protection of medical staff. Barcelona: 20–22 January 2011. www.oramed-fp7.eu/en/~/media/Files/ORAMED/Presentations/16ACARNICER.ashx (accessed 25 July 2011).
• 5 Chéa M, Donadille L, Trompier F. Etude des performances des protège-seringues utilisés dans un service de médecine nucléaire pour procéder à des injections de radiopharmaceutiques marqués à l'yttrium 90. IRSN Report DRPH/SDE n°2005–28. 2005
• 6 Coulot J, Ricard M. Radiation protection against yttrium 90: comparison between measurements and Monte-Carlo calculations. 50^th Annual Meeting of the Society of Nuclear Medicine. USA, New Orleans, USA: June 21–25 2003
• 7 Covens P, Berus D, Vanhavere F, Caveliers V. The introduction of automated dispensing and injection during PET procedures: a step in the optimisation of extremity doses and whole-body doses of nuclear medicine staff. Radiat Prot Dosimetry 2010; 140: 250-258.
• 8 Delacroix D, Guerre JP, Leblanc P, Hickman C. Radionuclide and radiation protection data handbook. Radiat Prot Dosimetry 2002; 98: 9-168.
• 9 Evaluated Nuclear Structure Data File (ENSDF), National Nuclear Data Center (NNDC). Brookhaven, USA: www.nndc.bnl.gov/chart/decaysearchdirect.jsp?nuc=124I&unc=nds (accessed December 18, 2010).
• 10 Freudenberg LS, Antoch G, Jentzen W. et al. Value of 124I-PET/CT in staging of patients with differentiated thyroid cancer. Eur Radiol 2004; 14: 2092-2098.
• 11 Herzog H, Tellman L, Qaim SM. et al. PET quantitation and imaging of the non-pure positron-emitting iodine isotope ¹²⁴I. Appl Radiat Isot 2002; 56: 673-679.
• 12 Jentzen W, Weise R, Kupferschläger J. et al. Iodine-124 PET dosimetry in differentiated thyroid cancer: recovery coefficient in 2D and 3D modes for PET(/CT) systems. Eur J Nucl Med Mol Imaging 2008; 35: 611-623.
• 13 Linemann H, Will E, Beuthien-Baumann B. Investigation concerning the radiation exposure of the medical personnel during ¹⁸F-FD G-PET studies. Nuklearmedizin 2000; 39: 77-81.
• 14 Pentlow KS, Graham MC, Lambrecht RM. et al. Quantitative imaging of iodine-124 with PET. J Nucl Med 1996; 37: 1557-1562.
• 15 Phan HT, Jager PL, Paans AM. et al. The diagnostic value of ¹²⁴I-PET in patients with differentiated thyroid cancer. Eur J Nucl Med Mol Imaging 2008; 35: 958-965.
• 16 Rimpler A, Barth I, Baum RB. et al. Beta radiation exposure of staff during and after therapies with 90Y-labelled substances. Radiat Prot Dosimetry 2008; 131: 73-79.
• 17 Rimpler A, Barth I. Beta radiation exposure of medical staff and implications for extremity dose monitoring. Radiat Prot Dosimetry 2007; 125: 335-339.
• 18 Robinson S, Julyan PJ, Hastings DL, Zweit J. Performance of a block detector PET scanner in imaging non-pure positron emitters - modelling and experimental validation with ¹²⁴I. Phys Med Biol 2004; 49: 5505-5528.
• 19 Tschurlovits M, Leitner A, Daverda G. Dose rate constants for new dose quantities. Radiat Prot Dosimetry 1992; 42: 77-82.
• 20 Vandenberghe S. Three-dimensional positron emission tomography imaging with ¹²⁴I and ⁸⁶Y. Nucl Med Commun 2006; 27: 237-245.
• 21 Vanhavere F, Berus D, Buls N, Covens P. The use of extremity dosimeters in a hospital environment. Radiat Prot Dosimetry 2006; 118: 190-195.