To assess the clinical value of single-time-point dosimetry for [¹⁷⁷Lu]Lu-PSMA-617 radioligand therapy in patients with metastatic castration-resistant prostate cancer (mCRPC). Fifty-nine patients with progressive mCRPC expressing PSMA and previously treated with androgen receptor pathway inhibitors and taxane-based chemotherapy were retrospectively analysed. SPECT/CT imaging was performed after the first (C1) and fourth (C4) [¹⁷⁷Lu]Lu-PSMA-617 infusions on 360°-CZT camera. Automated segmentation and dosimetry protocols were applied to quantify absorbed doses in bone marrow and lesions. Dose-effect relationships were assessed using blood counts, PSA responses (PSA50 criteria), and PET imaging. Statistical analyses included Spearman correlation, Wilcoxon signed-rank test, and logistic regression. Bone marrow absorbed dose (BMAD) at C1 was significantly correlated with red blood cells (RBC, ρ = -0.3) and haemoglobin (ρ = -0.26) decline. A higher BMAD was associated with greater declines in RBC count (median [IQR] 0.31 [0.33] Gy vs. 0.076 [0.19], p < 0.05) and haemoglobin (0.29 [0.41] vs. 0.092 [0.20], p = 0.056). A moderate negative correlation was found between PSA variation and total metastatic tumour absorbed (TMTAD) dose at C1 (ρ = -0.35) and from C1 to C4 (ρ = -0.35). Response modelling (based on PSA50) estimated 50

Prostate cancer (PCa) has been identified as the most prevalent form of cancer among males and the third leading cause of death from cancer in the European male population. Early-stage PCa can be treated with prostatectomy and radiotherapy, whereas metastatic cases require androgen deprivation therapy and may benefit from targeted radionuclide therapy (TRT). The objective of our research is to develop and validate an automated production of [177Lu]Lu-PSMA I T for clinical use. [177Lu]Lu-PSMA I T is a radioligand therapy (RLT) that targets prostate-specific membrane antigen (PSMA), which is overexpressed in metastatic and castration-resistant prostate cancer. This work delineates the development and validation of analytical methodologies for the automated production of [177Lu]Lu-PSMA I T with a GAIA-LUNA device from Elysia, in addition to the quality control measures implemented to ensure compliance with Good Manufacturing Practices and the European Pharmacopoeia. Three validation batches were produced, and the investigational medicinal product dossier was submitted to the French National Agency of Medicine and Health Products Safety (ANSM) for authorization. PSMA-I T was radiolabeled with 177Lu using an automated radiosynthesis device, the GAIA-LUNA, from Elysia. Furthermore, we demonstrated the 72-h stability of the [177Lu]Lu-PSMA I T preparations at room temperature, a development that facilitates the potential subcontracting of [177Lu]Lu-PSMA I T production to other medical facilities. The findings of this study underscore the potential of [177Lu]Lu-PSMA I T as a therapeutic option for patients with metastatic castration-resistant prostate cancer (mCRPC) who have contraindications to chemotherapy or hormonotherapy, and highlight the importance of implementing rigorous quality control measures in the development of radiopharmaceuticals.

Manual segmentation of prostate cancer metastases on PSMA PET/CT and SPECT/CT is time-consuming and poorly scalable, particularly in highly metastatic patients. This study evaluated nnU-Net–based automatic segmentation models trained on PET and SPECT either separately or jointly and assessed whether PET-derived information can improve SPECT lesion segmentation. Seventy-three patients with metastatic castration-resistant prostate cancer treated with ¹⁷⁷Lu-PSMA were retrospectively included: 48 from the Henri Becquerel Cancer Center (HBCC) and 25 from Nantes University Hospital (NUH). For each patient, ⁶⁸Ga-PSMA PET/CT and ¹⁷⁷Lu-PSMA SPECT/CT were acquired before and during the first treatment cycle respectively. All images were manually segmented by four nuclear medicine physicians in consensus. Four nnU-Net models were trained: M1 (PET/CT only), M2 (SPECT/CT only), M3 (joint PET/CT+SPECT/CT, unimodal input at inference), and M4 (SPECT/CT with PET/CT segmentation as a priori input). Models were first trained and internally validated on HBCC data, then retrained on the full HBCC cohort and externally validated on NUH data. For PET/CT segmentation, M1 and M3 achieved comparable performance. M1 reached DSCs of 0.83 ± 0.19 (internal) and 0.76 ± 0.22 (external), while M3 achieved 0.83 ± 0.16 (internal) and 0.77 ± 0.21 (external). For SPECT/CT, the PET-guided model M4 (DSC: 0.63 ± 0.24 internal; 0.78 ± 0.14 external; PPV: 0.65 ± 0.26 internal; 0.75 ± 0.23 external) provided the best results. Compared with the SPECT-only model M2 (DSC: 0.61 ± 0.26 internal; 0.70 ± 0.25 external; PPV: 0.63 ± 0.25 internal; 0.71 ± 0.24 external), M4 showed no statistically significant difference in internal validation (DSC p = 0.35), while being statistically significant in external validation (DSC p = 0.014). The nnU-Net framework enables accurate lesion segmentation on both ⁶⁸Ga-PSMA PET/CT and ¹⁷⁷Lu-PSMA SPECT/CT. While PET-only and joint PET+SPECT models perform similarly on PET images, incorporating PET-derived segmentations as prior information tends to improve SPECT/CT lesion segmentation. This PET-guided SPECT segmentation strategy leverages the higher spatial resolution of PET and represents a key step towards fully automated extraction of volumetric and dosimetric biomarkers for personalized prostate cancer treatment.

BACKGROUND:Patient-specific dosimetry in radiopharmaceutical therapy (RPT) offers a promising approach to optimize the balance between treatment efficacy and toxicity. The introduction of 360° CZT gamma cameras enables the development of personalized dosimetry studies using whole-body single photon emission computed tomography and computed tomography (SPECT/CT) data. PURPOSE:This study proposes to validate the collapsed-cone superposition (CCS) approach against Monte Carlo (MC) simulations for whole-body dosimetry of [177Lu]Lu-PSMA-617 therapy in patients with metastatic castration resistant prostate cancer (mCRPC). MATERIALS AND METHODS:Thirty patients with mCRPC were retrospectively included in this study. SPECT/CT images were acquired after the infusion of [177Lu]Lu-PSMA-617 therapy. SimpleDose was used to generate dose-rate maps (mGy/h) from a single SPECT/CT scan. The dosimetry relies on the CCS approach, which adjusts dose-point kernels according to tissue densities. Organ and lesion delineation were automated using the nnU-Net V2 neural network. MC simulations were performed with GATE 10 for 108 events. To assess the impact of density-scaled DPK on the accuracy of the dosimetry, we implement a simplified version of CCS, denoted as C C S S T $CC{S}_{ST}$ , which assumes a homogeneous soft tissue medium without incorporating the patient-specific density information derived from the CT image. The comparison between CCS, C C S S T $CC{S}_{ST}$ and MC was conducted at the organ, lesion, and voxel levels. RESULTS:Absolute percentage errors (APE) between CCS and MC were < 5% for all organs and lesions. Compared to CCS, C C S S T $CC{S}_{ST}$ exhibited higher APE with respect to MC in the liver, lungs, salivary glands, and lesions, while lower errors were observed in the bone marrow, kidneys, and pancreas, with comparable performance in the spleen. Voxel-level errors were mostly < 2% for both methods CCS and C C S S T $CC{S}_{ST}$ . Median computation time was, respectively, 24.5 s, 46.45 s, and 6.8 h for CCS, C C S S T $CC{S}_{ST}$ , and MC. CONCLUSION:CCS showed high agreement with MC with greater computational efficiency, demonstrating its clinical potential for whole-body dosimetry.

The advent of 360° CZT gamma-cameras allows to conceive personalised dosimetry studies from whole-body SPECT/CT data. We aimed to demonstrate the proof-of-concept of an automated personalized dosimetry pipeline for [177Lu]Lu-PSMA organ dosimetry, called SimpleDose, and to compare to other dosimetry approaches. The organ segmentation is based on a nnU-Net framework that was trained to allow for the segmentation of 23 organs and structures over all the body. The method implemented to model the energy deposition is the collapsed-cone-superposition (CCS) taking into account non-uniform activity and density distributions. Ten patients with metastatic castration resistant prostate cancer treated [177Lu]Lu-PSMA-617 were included. All SPECT/CT acquisitions were performed on a VERITON-CT 200 (Spectrum Dynamics®, Caesarea, Israel) from head to mid-thigh with 5 min per bed. The absorbed-dose-rates were computed with SimpleDose and compared with organ-level MIRD approach and local-deposition-method (LDM) for bone marrow, kidneys, liver, lungs, pancreas, salivary glands and spleen. Finally, an example of multi-time-point and single-time-point dosimetry is given. The median (IQR) calculation time with SimpleDose (SD), for segmentation, computation of dose-rates and descriptive statistics was 161 (23) seconds at a resolution of 2.46 × 2.46 × 2.46 mm3 (Intel Xeon 20 × 3.70 GHz CPU computer). The median (IQR) differences between SD and MIRD and LDM, were respectively 1.8 (61) https://oncometer3d.com .

The organization of nuclear medicine facilities, particularly those dedicated to PET, must balance quality of care and radiation protection in accordance with the ALARA principle. The evolution of PET technologies and the integration of AI improve sensitivity and allow large reductions in injected activities. In this context, the traditional practice of individual isolation room after radiopharmaceutical (RPM) injection is being questioned, since exposure levels in shared waiting rooms remain very low. This multicenter study evaluated the dosimetric consequences of using shared waiting rooms. Measurements carried out in three French departments show that the additional dose to patients is negligible (<1%) and that the increase in daily dose to technologists remains low (≈ 2.3 µSv/day), well below regulatory thresholds. No degradation in the diagnostic quality of images was observed. The use of shared waiting rooms therefore appears to comply with French regulations (ASN Guide No. 32) and provides a significant organizational benefit, enabling better patient flow management without compromising radiation protection or quality of care. The results of this study could be taken into account by the ICRP in the context of the planned revision of the radiation protection system by 2030.

Single photon emission computed tomography (SPECT/CT) using meta-iodobenzylguanidine (mIBG) is currently recommended in pediatric clinical guidelines for assessing neuroblastoma. However, [¹²³I]-mIBG scintigraphy may sometimes be less sensitive than positron emission tomography/computed tomography (PET/CT) using [¹⁸F]-FDOPA. In order to enhance diagnostic reliability and minimize the risk of missing lesions, both nuclear medicine imaging modalities were used here. We present a case study of a newborn girl who was diagnosed with neuroblastoma in utero. [18F]-FDOPA PET/CT scans showed faint uptake related to the lesion, whereas [123I]-mIBG scintigraphy was more sensitive and correlated with an MRI-suspicious mass. The metabolic pathways explored by the two tracers are different and sometimes complementary. [123I]-mIBG has an affinity for the norepinephrine transporter, whereas [18F]-FDOPA has an affinity for the large neutral amino acid transporter-1. The role of [¹⁸F]-FDOPA PET/CT in neuroblastoma is evolving and has been demonstrated to have high sensitivity, but surprisingly, in this particular case, it has limited specificity for neuroblastoma, which was taken into account when interpreting the [18F]-FDOPA PET/CT scan.

Abstract Patients with metastatic castration-resistant prostate cancer usually have lymph nodes and bone metastasis. We present a rare case of a 51-year-old patient with metastatic castration-resistant prostate cancer who complained of left truncated sciatica and diffuse bone pain and who was referred for 177Lu-prostate-specific membrane antigen (PSMA) screening. Pretreatment 68Ga-PSMA showed left sciatic nerve and multiple bone uptake. Patient underwent stereotactic radiotherapy on the sciatic nerve metastasis (30 Gy in 6 fractions of 5 Gy) before 7.4 GBq of 177Lu-PSMA infusions. Left truncated sciatica disappeared after stereotactic radiotherapy. No additional toxicity was added to the sciatic nerve from 177Lu-PSMA after stereotactic radiotherapy.

Nuclear medicine has long been a mainstay in the management of thyroid cancers. In patients with differentiated thyroid cancer (DTC), the most common histotype, radioiodine (RAI, 131I) has been for years a cornerstone for the treatment of RAI-avid metastases. Post-therapeutic 131I scintigraphy helps guide these treatments and contributes to the definition of refractory cancers. In these refractory patients, who represent fewer than 5% of CTDs, 18FDG PET plays a central diagnostic and prognostic role. From a therapeutic perspective, RAI uptake can be re-induced in some of these patients with the BRAF mutation by using redifferentiation protocols. In anaplastic thyroid cancer (ATC) that is rare, aggressive and undifferentiated, 18FDG PET remains the metabolic imaging of choice. In medullary thyroid cancer (MTC), PET imaging is mainly based on the use of 18F-DOPA, even if 18FDG also provides prognostic data and 68Ga-DOTATOC could allow a theranostic approach. Other radiopharmaceuticals offering new theranostic avenues in thyroid cancers are also discussed, such as prostate-specific membrane antigen (PSMA) and fibroblast activation protein (FAP). After decades of a "one-size fits all" approach in thyroid cancer management, molecular imaging is paving the way towards personalized medicine.

La médecine nucléaire occupe depuis longtemps une place importante dans la prise en charge des cancers thyroïdiens. Dans les cancers thyroïdiens différenciés (CTD), les plus fréquents, l’iode radioactif (131I) garde un rôle fondamental dans le traitement des métastases iodofixantes. La scintigraphie post-thérapeutique à l’131I permet de guider ces traitements et contribue à la définition des cancers réfractaires. Chez ces patients réfractaires, qui représentent moins de 5 % des CTD, la TEP/TDM 18FDG joue un rôle diagnostique et pronostique central. Sur le plan thérapeutique, la redifférenciation, c’est-à-dire la restauration de la fixation de l’131I, est possible chez des CTD mutés BRAF. Dans les cancers anaplasiques de la thyroïde (CAT), rares et agressifs, et par définition indifférenciés, la TEP au 18FDG reste l’imagerie métabolique de choix. Dans les cancers médullaires (CMT), l’imagerie TEP repose principalement sur la 18F-DOPA mais le 18FDG et le 68Ga-DOTATOC peuvent être utiles, en raison des données pronostiques et théranostiques qu’ils peuvent fournir. D’autres radiopharmaceutiques TEP qui sont encore du domaine de la recherche et dont certains offrent des perspectives théranostiques, tels l’antigène membranaire spécifique de la prostate (PSMA) et la protéine d’activation des fibroblastes (FAP), seront également discutés. Après des décennies où seul l’131I était disponible et administré systématiquement dans les CTD, quel que soit le risque de maladie résiduelle, l’arrivée de nouveaux traceurs TEP vient enrichir les outils d’imagerie et l’arsenal thérapeutique. Les développements rapides et récents de l’imagerie moléculaire permettent une évolution vers une prise en charge encore plus personnalisée des cancers thyroïdiens.

BACKGROUND: PET-CT with F-18-EDG or other radiophannaceuticals is a recommended tool to help the delineation of lung cancers candidate to radiotherapy. The motion artifacts caused by respiratory movements are reduced by 4D acquisitions. We introduced an extended reconstruction algorithm (multiple reconstruct register and average [multi-RRA]) which requires much shorter acquisition times than standard 4D PET-CT. Our aim was to evaluate the interest on multi-RRA images as an alternative of 3D and 4D PET-CT for the delineation of lung lesion. METHODS: PET acquisitions synchronized to the respiratory signal were obtained in 18 patients with mobile lung tumors. We compared the tumor volumes delineated on Multi-RRA images to 3D and 4D PET-CT, considering the 4D CT as a reference. The tumor volumes were delineated and compared with topologic similarity indexes (Dice, Jaccard and overlap). RESULTS: Twenty tumors were delineated. The volumes delineated with multi-RRA and 4D PET were not significantly different (mean difference of 0.2 +/- 0.7 mL). Comparison by pairs (Tukey-Kramer test) showed that 3D-PET volumes were significantly smaller than 4D-PET and multi-RRA volumes (P<0.001). Topologic similarity indexes with 4D-PET were slightly statistically higher with multi-RRA than with 3D-PET (Dice and Jaccard) or 4D-CT (Dice, Jaccard and Overlap). CONCLUSIONS: The tumor volumes delineated on multi-RRA are similar to the volumes obtained with 4D PET, with shorter acquisition time.

Radio-iodine refractory (RAI-R) differentiated thyroid cancer (DTC) is a rare disease with a poor prognosis and limited therapeutic resources. Therefore, identifying prognostic factors is essential in order to select patients who could benefit from an early start of treatment. The aim of this study is to identify positron emission tomography with 18F-fluorodeoxyglucose with integrated computed tomography (18F-FDG-PET/CT) parameters to predict overall survival (OS) in patients with RAI-R DTC. In this single-center retrospective study, we analyze the 18F-FDG-PET/CT parameters of 34 patients with RAI-R DTC between April 2007 and December 2019. The parameters collected are MTV, SUVmax and progression for each site of metastasis (neck, mediastinum, lungs, liver, bone) and total sites. ROC curves, Kaplan–Meier survival analysis curves, univariate and multivariate Cox analyses determine prognostic factors for 1-year and 5-year OS. The parameters for mediastinum, liver and total sites are significantly associated with worse 1-year and 5-year OS by both ROC curve analysis and Kaplan–Meier survival analysis. Univariate Cox analysis confirms significance of mediastinum SUVmax (HR 1.08; 95% CI [1.02–1.15]; p = 0.014) and total SUVmax (HR 1.06; 95% CI [1–1.12]; p = 0.042) for worse 1-year OS; of mediastinum SUVmax (HR 1.06; 95% CI [1.02–1.10]; p = 0.003), liver SUVmax (HR 1.04; 95% CI [1.01–1.08]; p = 0.02), liver MTV (HR 2.56; 95% CI [1.13–5.82]; p = 0.025), overall SUVmax (HR 1.05; 95% CI [1.02–1.08]; p = 0.001) and total MTV (HR 1.41; 95% CI [1.07–1.86]; p = 0.016) for worse 5-year OS. Multivariate Cox analysis confirms a significant association between liver MTV (HR 1.02; 95% CI [1–1.04]; p = 0.042) and decrease 1-year OS. In this study, we demonstrate that in RAI-R DTC, 18F-FDG-PET/CT parameters of the mediastinum, liver and overall tumor burden were prognostic factors of poor 1-year and 5-year OS. Identifying these criteria could allow early therapeutic intervention in order to improve patients’ survival.

Le cancer est une maladie aux conséquences multidimensionnelles s’accompagnant de nombreux défis afin de garantir une prise en charge optimale intégrant les conséquences physiques, psychologiques et sociales de la maladie et de ses traitements. L’objectif de l'étude est d’identifier les principales problématiques rencontrées par différents acteurs autour du cancer, dont les patients. Cette étude qualitative a été menée auprès d’acteurs en cancérologie à Bruxelles. Les entretiens semi-directifs et les groupes focaux ont été transcrits directement et analysés manuellement. Dans le contexte actuel de la prise en charge en oncologie, les professionnels de santé et les patients doivent faire face à de nombreux défis. Les difficultés communicationnelles peuvent altérer la relation thérapeutique et le partage d’informations complexes. La complexification des traitements complique les collaborations interprofessionnelles et la coordination des soins. Dans un contexte de retour au domicile et d'hospitalisation à domicile, la continuité des soins et les collaborations entre différentes lignes de soins sont déterminantes. Les patients doivent gérer les effets secondaires à long terme et l’après-cancer dont la redéfinition de ses identités sociales et professionnelles. Enfin, le cancer s’accompagne d’une toxicité financière marquant particulièrement les inégalités sociales en santé. La prise en charge du cancer fait intervenir un nombre croissant d’intervenants et est fréquemment synonyme de rupture dans le parcours de vie des patients. Les thématiques émergentes de cette étude sont étroitement interconnectées et la communication semble occuper une place centrale. Une approche holistique de la personne et des échanges interprofessionnels pourraient guider les perspectives futures de prise en charge globale de ce domaine en constante mutation.Cancer is a disease with multidimensional consequences accompanied by new challenges in order to guarantee optimal care involving physical, psychological and social consequences of the disease and his treatments. The objective of this study is to identify the main challenges encountered by different stakeholders around cancer, including patients, in Brussels. This qualitative study was carried out with various stakeholders in the field of oncology. The semi-structured interviews and focus groups were transcribed directly and the data collected was analysed manually. Healthcare professionals and patients face many challenges in the current context of oncology care. Communication difficulties can affect the therapeutic relationship and the sharing of complex information. The increasing complexity of therapeutic strategies complicates interprofessional collaborations and care coordination. In a context of early return home and home hospitalization in particular, continuity in care and collaboration between the different lines of care are crucial. Patients face a variety of challenges, such as managing long-term side effects and post-cancer difficulties, including redefining their social and professional identities. Finally, cancer involves financial toxicity and social inequalities in health are particularly marked. Cancer is a complex disease which management involves a growing number of caretakers. It is also frequently synonymous with disruption in the personal, social and professional life of patients. The emerging themes of this study are closely interconnected and communication seems to occupy a central place. A holistic approach to the individual and inter-professional interactions could guide future prospects for the overall management of this constantly changing field.

To determine the impact of the Bayesian penalized likelihood (BPL) reconstruction algorithm in comparison to OSEM on hypoxia PET/CT images of NSCLC using 18F-MIZO and 18F-FAZA. Images of low-contrasted (SBR = 3) micro-spheres of Jaszczak phantom were acquired. Twenty patients with lung neoplasia were included. Each patient benefitted from 18F-MISO and/or 18F-FAZA PET/CT exams, reconstructed with OSEM and BPL. Lesion was considered as hypoxic if the lesion SUVmax > 1.4. A blind evaluation of lesion detectability and image quality was performed on a set of 78 randomized BPL and OSEM images by 10 nuclear physicians. SUVmax, SUVmean, and hypoxic volumes using 3 thresholding approaches were measured and compared for each reconstruction. The phantom and patient datasets showed a significant increase of quantitative parameters using BPL compared to OSEM but had no impact on detectability. The optimal beta parameter determined by the phantom analysis was β350. Regarding patient data, there was no clear trend of image quality improvement using BPL. There was no correlation between SUVmax increase with BPL and either SUV or hypoxic volume from the initial OSEM reconstruction. Hypoxic volume obtained by a SUV > 1.4 thresholding was not impacted by the BPL reconstruction parameter. BPL allows a significant increase in quantitative parameters and contrast without significantly improving the lesion detectability or image quality. The variation in hypoxic volume by BPL depends on the method used but SUV > 1.4 thresholding seems to be the more robust method, not impacted by the reconstruction method (BPL or OSEM). ClinicalTrials.gov, NCT02490696. Registered 1 June 2015

La principale cause d’hypercalcémie chronique est l’hyperparathyroïdie primaire causée par un adénome parathyroïdien. Dans 10 % des cas, celui-ci peut se situer en position ectopique. Une patiente de 55 ans, sans antécédent médical connu, est adressée pour l’exploration d’une hypercalcémie asymptomatique. L’examen clinique est normal. Le bilan biologique est en faveur d’une hyperparathyroïdie primaire : une calcémie corrigée à 3,2 mmol/L (2,15–2,55), une PTH à 201 pg/mL (5–40), une 25OH-vitamine D à 41 ng/mL (30–50) et une calciurie des 24 h à 9,7 mmol/24 h (< 7,0). L’échographie cervicale ne retrouve pas d’adénome. La scintigraphie au MIBI couplée à une imagerie hybride par TEMP-TDM ne met pas en évidence de fixation évoquant un adénome parathyroïdien. Afin de rechercher une localisation ectopique, on réalise un scanner cervical multiphasique ainsi qu’une IRM qui révèlent la présence d’une masse de 34 mm en arrière de la glande sous-mandibulaire gauche. La patiente est opérée et l’examen anatomopathologique affirme le diagnostic d’adénome parathyroïdien. De manière rétrospective, la relecture des images de la TEMP-TDM en coupe sagittale montre un foyer scintigraphique en arrière de la glande sous-mandibulaire gauche. Du fait de la fixation physiologique du traceur au niveau des glandes salivaires, il était donc impossible de les différencier sur un plan coronal en 2D. Nous rapportons un cas d’adénome ectopique sous-mandibulaire ayant entraîné un faux résultat négatif lors de la scintigraphie parathyroïdienne par superposition des fixations de la lésion et de la glande sous-mandibulaire homolatérale. Dans cette situation, l’imagerie conventionnelle est un bon moyen de localiser l’adénome.

A 66-year-old man with prostate cancer underwent F-fluorocholine PET/CT and thereafter Ga-labeled prostate-specific membrane antigen PET/CT to explore a rising prostate-specific antigen level. Both PET/CT studies showed a thyroid incidentaloma of the right lobe. Neck ultrasound confirmed the presence of a 16-mm right thyroid nodule. The serum calcitonin level was moderately increased at 25 ng/mL (<10). Cytology was non-diagnostic (Bethesda I). A right lobectomy was performed and pathology revealed a 15-mm medullary thyroid cancer. Two months after surgery, the calcitonin level returned to normal at 3.3 ng/mL.

193 Objectives: Recently, a third manufacturer proposed a positron emission tomography system based on silicon photomultiplier, commonly called “digital pet”. This technology provides a better sensitivity and a lower and more robust time resolution, leading to a better signal to noise ratio. A better spatial resolution thanks to smaller crystal units or more precise optic detectors was also demonstrated. The purpose of this work was to compare those state of the art digital pet systems thanks to phantom examinations using clinical-like acquisition and reconstruction protocols. Methods: We compared five systems installed in 5 different French nuclear medicine departments. Philips Vereos (TEP1), GE DMI 4rings (TEP2), Siemens Vision 600 (TEP3 and TEP4). We acquired a NEMA IEC phantom (0.7 to 26.5 mL hot spheres) and a Jaszczak phantom equipped with at least 5 sub-centimeter spheres (31, 63, 125, 250 and 500 µL) and cold rods (rod diameters were 4.8, 6.4, 7.9, 9.5, 11.1 and 12.7 mm). For the IEC phantom, the activity at acquisition time was 50 MBq with a 4:1 contrast, and for the Jaszczak phantom, 20 MBq with 3:1 and 6:1 contrast. IEC phantom was acquired with one bed position during 600s. Jaszczak phantom was acquired in list mode during 600s and reconstructed in 10, 5, 3, 2 and 1 min emission time. We considered reconstruction parameters currently used in each center for whole body clinical examinations. IEC phantom was used to measure sensitivity, signal to noise ratio in homogeneous area and contrast recovery from max and mean value. Jaszczak phantom was used to evaluate the visual detectability: for each emission time, 2 readers assigned a score (0= invisible, 1= slightly visible, 2= visible) to the 4 smallest cold rods areas, and to the four smallest visible hot spheres (63, 125, 250 and 500 µL for 3:1 contrast and 31, 63, 125 and 250 µL for 6:1 contrast). The scores were averaged to obtain a detectability score as a function of emission time (max=16). Results: Considering IEC phantom, sensitivity was 3.1, 8.52, 9.38 and 9.66 cps/MBq, Signal to noise ratio was 16.6, 36.3, 35.8 and 28 for TEP1 to 4 respectively. Contrast recovery from max value were [0.56;0.79;0.98;1.07;1.13;1.22], [0.59;0.88;1.08;1.07;1.12;1.1], [0.78;1.09;1.2;1.2;1.21;1.21], [0.81;1.18;1.15;1.2;1.22;1.21] for TEP1 to 4 respectively. Contrast recovery from mean value were [0.42;0.56;0.7;0.73;0.84;0.96], [0.42;0.57;0.69;0.75;0.82;0.84], [0.52;0.64;0.77;0.83;0.89;0.94], [0.51;0.66;0.77;0.85;0.92;0.95] for TEP1 to 4 respectively. Considering the detectability score on Jaszczak phantom, we found with 6:1 contrast from 1 to 10 min emission time [3;4.5;6;7.5;8.5] [4;7;8.5;10.5;11], [9;11;11.5;13;14.5] and [10;12.5;14.5;16;16] for TEP1 to 4 respectively. With 3:1 contrast we found [2;3;3.5;6;7.5], [4.5;6.5;9;9.5;11] and [6;9;10;12;13.5] for TEP1 to 4 respectively. Conclusions: SiPM technology leads a substantial improvement in the quantification and detectability of small lesions. In this work we focused on clinical locally used reconstructions, and we found variability between similar systems due to variation of reconstruction parameters. In a future work, we plan to measure those indices on a larger amount of devices, including non-SiPM systems, to have a more accurate view of their actual performances.