It is known that medical applications using ionising radiation are wide spread and still increasing. Physicians, technicians, nurses and others constitute the largest group of workers occupationally exposed to man-made sources of radiation. Many hospital workers are consequently subjected to routine monitoring of professional radiation exposures. in the university hospital, UZ Brussel, 600 out of 4000 staff members are daily monitored for external radiation exposures. The most obvious applications of ionising radiation are diagnostic radiology, diagnostic or therapeutic use of radionuclides in nuclear medicine and external radiation therapy or brachytherapy in radiotherapy departments. Other important applications also include various procedures in interventional radiology (IR), in vitro biomedical research and radiopharmaceutical production around cyclotrons. Besides the fact that many of the staff members, involved in these applications, are not measurably exposed, detailed studies were carried out at workplaces where routine dose monitoring encounters difficulties and for some applications where relatively high occupational exposures can be found. most of the studies are concentrated around nuclear medicine applications and IR. They contain assessments of both effective dose and doses at different parts of the body. The results contribute to better characterisation of the different workplaces in a way that critical applications can be identified. Moreover, conclusions point out future needs for practical routine dose monitoring and optimisation of radiation protection.

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Targeted alpha-particle therapy (TAT) might be a relevant therapeutic strategy to circumvent resistance to conventional therapies in the case of HER2-positive metastatic cancer. Single-domain antibody fragments (sdAb) are promising vehicles for TAT because of their excellent in vivo properties, high target affinity, and fast clearance kinetics. This study combines the cytotoxic α-particle emitter bismuth-213 ( 213 Bi) and HER2targeting sdAbs. The in vitro specificity, affinity, and cytotoxic potency of the radiolabeled complex were analyzed on HER2 pos cells. Its in vivo biodistribution through serial dissections and via Cherenkov and micro-single-photon emission computed tomography (CT)/CT imaging was evaluated. Finally, the therapeutic efficacy and potential associated toxicity of [ 213 Bi]Bi-DTPA-2Rs15d were evaluated in a HER2 pos tumor model that manifests peritoneal metastasis. In vitro, [ 213 Bi]Bi-DTPA-2Rs15d bound HER2 pos cells in a HER2-specific way. In mice, high tumor uptake was reached already 15 min after injection, and extremely low uptake values were observed in normal tissues. Co-infusion of gelofusine resulted in a 2-fold reduction in kidney uptake. Administration of [ 213 Bi]Bi-DTPA-2Rs15d alone and in combination with trastuzumab resulted in a significant increase in median survival. We describe for the very first time the successful labeling of an HER2-sdAb with the α-emitter 213 Bi, and after intravenous administration, revealing high in vivo stability and specific accumulation in target tissue and resulting in an increased median survival of these mice especially in combination with trastuzumab. These results indicate the potential of [ 213 Bi]Bi-DTPA-sdAb as a new radioconjugate for TAT, alone and as an add-on to trastuzumab for the treatment of HER2 pos metastatic cancer.

Significant staff exposure is generally expected during PET-and PET/CT applications. Whole-body doses as well as extremity doses are usually higher per procedure compared with SPECT applications. Dispensing individual patient doses and manual injection involves high extremity doses even when heavy weighted syringe shields are used. In some cases the external radiation causes an exposure to the fingertips of more than 500 mSv y(-1), which is the yearly limit. Whole-body doses per procedure are relatively lower compared with extremity doses and are generally spread over the entire procedure (Guillet, B., Quentin, P., Waultier, S., Bourrelly, M., Pisano, P. and Mundler, O. Technologist radiation exposure in routine clinical practice with 18F-FDG PET. J. Nucl. Med. Technol. 33, 175-179 (2005). Optimisation of the individual workload is often used to restrict staff doses, but many PET centres face the need for further optimisation to reduce the staff doses to an acceptable level. During this study the effect of the use of an automated dispensing and injection system for (18)FDG on whole-body doses and extremity doses was evaluated. Detailed dosimetric studies using thermoluminescent and direct ion storage dosimetry were carried out before and after the introduction of this system. The results show that the extremity doses can be reduced by more than 95 % up to a mean level of 10 muSv per handled GBq. At the same time, whole-body doses can be halved during injection of the tracer. This results in a dose reduction of 20 % during the entire procedure of injection, escorting and positioning. In this way, the study shows that with the use of automated dispensing and injection a considerable staff dose reduction can be obtained.

A general overview is given on the use of extremity dosemeters, their calibration, the units and phantoms to be used. One of the major applications of extremity dosemeters is to monitor the personnel in a hospital environment. In nuclear medicine, brachytherapy and interventional radiology (IR) skin doses to hands and legs can be substantial. Here, we report on two studies that are presently being undertaken in Belgium. The first one tries to map the dose distribution on the hands, in function of the manipulation in nuclear medicine. Some preliminary results are also given from a nationwide survey study for patient and personnel doses during IR and cardiology. The radiologists' hands, legs and forehead are monitored during a whole range of procedures in different hospitals.