Background: Long-lived radioactive impurities in radiopharmaceuticals administered at time of calibration usually have minor impact on image quality and the uncertainty of the activity measurement. How- ever, such impurities may result to non-negligible additional radiation burden to patients, personnel, relatives, caregivers and the public, and may trigger innocent alarms in radiation portal monitors. In addition, the presence of certain levels of impurities may impose modifications in waste management policies. The aim of the present study was to identify the most important long-lived impurities, quan- tify their amount in the patients’ body and address radiation protection issues. Methods and materials: Initial analysis of the radiopharmaceuticals used at the Ioannina University Hospital indicated substantial amounts of long- lived (T 1/2 > 14 d) photon emitting impurities only in 123 I-ioflupene (DaTSCAN, GE) and 153 Sm-EDMTP (Quadramet, IBA). Spectroscopic anal- ysis of the residuals of at least ten administrations per agent was carried out at least five times per sample. A prototype shadow-shield whole body counter equipped with 16 NaI(Tl) detectors was used to measure the ac- tivity present in at least 7 seven patients per agent, 2 to 5 five weeks post- administration. The in vivo activity measurements were coupled with external dose rate measurements using a portable system with spectro- scopic capabilities. Results: 121 Te, 123 Te and 125 I were the main photon emitting impurities in 123 I-ioflupene, resulting in a median 30 nSv/h external Hp(10) rate and a 3 kBq 121 Te body burden. 152 Eu, 152 Eu and 156 Eu were the main impurities in 153 Sm-EDMTP, resulting in a median 300 nSv/h external rate, mainly due to the 152 Eu (T 1/2 :13.5 y) and 154 Eu (T 1/2 :8.6 y) presence in the body, 25 and 33 kBq, respectively. Thus patient and waste management protocols were modified accordingly. Conclusions: Both patient and waste management have to take into ac- count the long-lived impurities present in some of the agents used in daily clinical practice. MEDICAL WORKERS OPERATING IN NUCLEAR MEDICINE VS PET/CT: RADIATION EXPOSURE COMPARISON K. Dalianis a , J. Malamitsi b , K. Gogos a , R. Efthimiadou a , J. Andreou a , V. Prassopoulos a . a PET/CT Department Hygeia SA, Athens, Greece; b Medical Physics Laboratory School of Medicine, University of Athens, Greece Purpose: Personnel monitoring results provide information on routine radiation exposure, assist in work planning and allow control of the workplace. The aim of this study was to compare the gamma dose received by dedicated medical workers operating in the first PET/CT department in Greece and also by dedicated medical workers operating in conventional Nuclear Medicine procedures in the same center. PET/CT studies are restricted to the use of 18 F fluorodeoxyglucose (FDG). In addition Tc-99m, Tl-201, Ga-67 and I-131 are the radiotracers mostly used in our Nuclear Medicine department. Method: To estimate the effective dose from external exposure, all 9 members of the staff (2 nurses, 2 medical physicists, 5 technologists) had TLD badges worn at the upper pocket of their overall and digital dosime- ters worn at the side pocket. Nurses and Medical Physicists also had TLD rings. The nurses and technologists 1,2 are working only in the PET/CT department, while technologists 3,4,5 are operating only in the Nuclear Medicine department covering the most common procedures. Medical Physicists 1,2 are operating in both departments. Results: In the period of January 2013 to December 2013 a total of 982 PET/ CT studies and 2157 conventional Nuclear Medicine procedures were performed. The collective effective and finger doses received by all 4 members of the PET/CT staff were the following: Nurse 1 received 2,94 mSv as a whole body dose and 6,84 mSv as a hand dose and Nurse 2 received 2,87 mSv whole body dose and 5,91 mSv hand dose respectively. Technologists 1 and 2 received 1,95 mSv and 1,56 mSv as the whole body dose respectively. Medical Physicist 1 received 1,75 mSv whole body dose and 7,77 mSv hand dose and Medical Physicist received 2 2,17 mSv and 4,68 mSv respectively. Technologists 3,4 and 5 received 1,85 mSv, 1,76 mSv and 1,82 mSv as whole body doses respectively Conclusion: The personnel dose results are significantly lower than the recommended annual dose by International Commission for Radiological Protection. The higher value of gamma dose for PET/CT workers by comparison with the staff operating conventional Nuclear Medicine procedures is attributable to the higher specific gamma constant of 18 F, as well as the longer exposure time required for ac- curate positioning. THREE-DIMENSIONAL METRICS FOR QUANTITATIVE MONITORING OF TREATMENT EFFECTS WITH PET/CT N. Politis a , A. Georgakopoulos b , M. Metaxas b , S. Chatziioannou b, c , M. Kallergi a, b . a Department of Biomedical Engineering, Technological Educational Institute of Athens, Greece; b Nuclear Medicine Division, Biomedical Research Foundation of the Academy of Athens, Greece; c Nuclear Medicine Section, 2 nd Department of Radiology, “Attikon” University General Hospital, National and Kapodistrian University of Athens, Greece Background: Quantitative monitoring of tumor response to treatment with PET has been introduced in the last decade and volume-based criteria have been proposed for this purpose (PERCIST 1.0 in 2009). The purpose of this study was to evaluate the expansion of the standardized uptake value corrected for lean body mass (SUL) metric to tumor volume size mea- surements pre- and post-treatment for more standardized and accurate treatment monitoring. Materials & methods: A database was developed of 24 serial PET/CT scans of patients with non Hodgkin’s lymphoma; each patient had one scan before and one after at least one cycle of chemotherapy. An expert nuclear medicine physician manually outlined all tumors, before and after treatment, on all PET and CT slices they are observed in. The expert’s outlines were used as “ground truth” to image processing and tumor segmentation that was done in MATLAB. A semi-supervised algorithm was implemented for the generation of 2D and 3D outlines of the tumors on PET and CT slices. The tumors’ maximum diameter and volume were measured in addition to SUL estimates. Binary logistic regression was used to evaluate the association between the three metrics (diameter, volume, and SUL) and treatment outcome, expressed as progression free survival (PFS) rate. Results: The data analysis is ongoing. However, preliminary results suggest that volume is a more standard and reproducible metric than the diameter in assessing response to treatment; even a 10% in volume shrinkage can be a strong predictor of long term outcome. In addition, the combination of volume changes with SUL changes yields a significantly better predictor of treatment outcome and correlates more to PFS rates than the tumor diameter or SUL. Discussion: Changes in tumor volume corresponding to anatomic changes combined with SUL changes indicating metabolic tumor response are stronger predictors of treatment outcome than changes in tumor diameter or SUL changes alone as proposed by the RECIST or PERCIST criteria. POSITRON EMISSION TOMOGRAPHY'S NEWEST TECHNOLOGIES TO ADDRESS PRESENT AND FUTURE APPLICATIONS: A FOCUS ON TIME- OF FLIGHT L. Theodorakis a, b , G. Loudos b , V. Prassopoulos c , C. Kappas d , I. Tsougos d , P. Georgoulias a . a Department of Nuclear Medicine, University Hospital of Larissa, Biopolis, Larissa 41110, Greece; b Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Str., Egaleo 122 10, Athens, Greece; c PET/CT Department, Hygeia Hospital, Erythrou Stavrou Str. & Kifisias Av., Marousi 151 23, Athens, Greece; d Medical Physics Department, Medical School, University of Thessaly, Biopolis, Larissa, Greece Introduction: Positron Emission Tomography (PET) is constantly mov- ing towards newer applications, extending its scope far beyond of just providing with the answer for the presence of cancer or not. Novel ra- diopharmaceuticals for the functional characterization in the brain or stem cells tracking after their transplantation are among these appli- cations [1]. Taking also into consideration that treatment planning and response-to-therapy assessment usually involves a PET/CT scan, the Abstracts / Physica Medica 30 (2014) e16ee44 e31