The BPL algorithm improves the image quality and lesion contrast and appears to be particularly appropriate for patients with a high BMI as it improves the SNR. However, it will be important for patient follow-up or multicenter studies to use the same algorithm and preferably BPL.

Background Differentiated thyroid cancer has been treated with radioiodine for almost 80 years, although controversial questions regarding radiation-related risks and the optimisation of treatment regimens remain unresolved. Multi-centre clinical studies are required to ensure recruitment of sufficient patients to achieve the statistical significance required to address these issues. Optimisation and standardisation of data acquisition and processing are necessary to ensure quantitative imaging and patient-specific dosimetry. Material and methods A European network of centres able to perform standardised quantitative imaging of radioiodine therapy of thyroid cancer patients was set-up within the EU consortium MEDIRAD. This network will support a concurrent series of clinical studies to determine accurately absorbed doses for thyroid cancer patients treated with radioiodine. Five SPECT(/CT) systems at four European centres were characterised with respect to their system volume sensitivity, recovery coefficients and dead time. Results System volume sensitivities of the Siemens Intevo systems (crystal thickness 3/8″) ranged from 62.1 to 73.5 cps/MBq. For a GE Discovery 670 (crystal thickness 5/8″) a system volume sensitivity of 92.2 cps/MBq was measured. Recovery coefficients measured on three Siemens Intevo systems show good agreement. For volumes larger than 10 ml, the maximum observed difference between recovery coefficients was found to be ± 0.02. Furthermore, dead-time coefficients measured on two Siemens Intevo systems agreed well with previously published dead-time values. Conclusions Results presented here provide additional support for the proposal to use global calibration parameters for cameras of the same make and model. This could potentially facilitate the extension of the imaging network for further dosimetry-based studies.

PurposeThis study aims to predict hematological toxicity induced by 223Ra therapy. We investigated the value of metabolically active bone tumor volume (MBTV) and total bone lesion activity (TLA) calculated on pretreatment fluorine-18-fluorocholine (18F-FCH) PET/CT in castrate-resistant prostate cancer (CRPC) patients with bone metastases treated with 223Ra radionuclide therapy.Patients and methods18F-FCH PET/CT imaging was performed in 15 patients with CRPC before treatment with 223Ra. Bone metastatic disease was quantified on the basis of the maximum standardized uptake value (SUV), total lesion activity (TLA=MBTV×SUVmean), or MBTV/height (MBTV/H) and TLA/H. 18F-FCH PET/CT bone tumor burden and activity were analyzed to identify which parameters could predict hematological toxicity [on hemoglobin (Hb), platelets (PLTs), and lymphocytes] while on 223Ra therapy. Pearson’s correlation was used to identify the correlations between age, prostate-specific antigen, and 18F-FCH PET parameters.ResultsMBTV ranged from 75 to 1259 cm3 (median: 392 cm3). TLA ranged from 342 to 7198 cm3 (median: 1853 cm3). Patients benefited from two to six cycles of 223Ra (n=56 cycles in total). At the end of 223Ra therapy, five of the 15 (33%) patients presented grade 2/3 toxicity on Hb and lymphocytes, whereas three of the 15 (20%) patients presented grade 2/3 PLT toxicity.Age was correlated negatively with both MBTV (r=−0.612, P=0.015) and TLA (r=−0.596, P=0.018). TLA, TLA/H, and MBTV/H predicted hematological toxicity on Hb, whereas TLA/H and MBTV/H predicted toxicity on PLTs at the end of 223Ra cycles. Receiver operating characteristic curve analysis allowed to define the cutoffs for MBTV (915 cm3) and TLA (4198 cm3) predictive for PLT toxicity, with an accuracy of 0.92 and 0.99.ConclusionTumor bone burden calculation is feasible with 18F-FCH PET/CT with freely available open-source software. In this pilot study, baseline 18F-FCH PET/CT markers (TLA, MBTV) have shown abilities to predict Hb and PLT toxicity after 223Ra therapy and could be explored for patient selection and treatment optimization.