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Introduction: Transthyretin (ATTR) amyloidosis is responsible for the majority of cardiac amyloidosis (CA) cases and can be reliably diagnosed with bone scintigraphy and the visual Perugini score. We aimed to implement a quantification method of cardiac amyloid deposits in patients with suspected cardiac amyloidosis and to compare performance to visual scoring. Methods and materials: 136 patients received ⁹⁹mTc-DPD-bone scintigraphy including SPECT/CT of the thorax in case of suspicion of cardiac amyloidosis. Imaging phantom studies were performed to determine the scaling factor for standardized uptake value (SUV) quantification from SPECT/CT. Myocardial tracer uptake was quantified in a whole heart volume of interest. Results: Forty-five patients were diagnosed with CA. A strong relationship between cardiac SUVmax and Perugini score was found (Spearman r 0.75, p

Poster-Abstract

Introduction: Patient eligibility for [¹⁷⁷Lu]Lu-PSMA therapy remains a challenge, with only 40–60% response rate when patient selection is done based on the lesion uptake (SUV) on [⁶⁸Ga]Ga-PSMA-PET/CT. Prediction of absorbed dose based on this pre-treatment scan could improve patient selection and help to individualize treatment by maximizing the absorbed dose to target lesions while adhering to the threshold doses for the organs at risk (kidneys, salivary glands, and liver). Methods: Ten patients with low-volume hormone-sensitive prostate cancer received a pre-therapeutic [⁶⁸Ga]Ga-PSMA-11 PET/CT, followed by 3 GBq [¹⁷⁷Lu]Lu-PSMA-617 therapy. Intra-therapeutically, SPECT/CT was acquired at 1, 24, 48, 72, and 168 h. Absorbed dose in organs and lesions (n = 22) was determined according to the MIRD scheme. Absorbed dose prediction based on [⁶⁸Ga]Ga-PSMA-PET/CT was performed using tracer uptake at 1 h post-injection and the mean tissue effective half-life on SPECT. Predicted PET/actual SPECT absorbed dose ratios were determined for each target volume. Results: PET/SPECT absorbed dose ratio was 1.01 ± 0.21, 1.10 ± 0.15, 1.20 ± 0.34, and 1.11 ± 0.29 for kidneys (using a 2.2 scaling factor), liver, submandibular, and parotid glands, respectively. While a large inter-patient variation in lesion kinetics was observed, PET/SPECT absorbed dose ratio was 1.3 ± 0.7 (range: 0.4–2.7, correlation coefficient r = 0.69, p < 0.01). Conclusion: A single time point [⁶⁸Ga]Ga-PSMA-PET scan can be used to predict the absorbed dose of [¹⁷⁷Lu]Lu-PSMA therapy to organs, and (to a limited extent) to lesions. This strategy facilitates in treatment management and could increase the personalization of [¹⁷⁷Lu]Lu-PSMA therapy.

Additional file 1: Supplemental Figure S1. Peak activity concentration ratio for the small-tumour phantom as a function of the acquisition time by reference to the 10-min acquisition time PET images separately for the different investigated combinations of voxel sizes, Gaussian filters, and OSEM-TOF (A-D) or OSEM-TOF+PSF (E-H) image reconstructions. Data for all investigated spheres are presented. Dashed horizontal lines indicate the ±20% deviation (acceptance criterion). Supplemental Figure S2. Peak activity concentration ratio for the bone-lung phantom as a function of the acquisition time by reference to the 10-min acquisition time PET images separately for the different investigated combinations of voxel sizes, Gaussian filters, and OSEM-TOF (A-D) or OSEM-TOF+PSF (E-H) image reconstructions. Data for all investigated spheres/density regions are presented. Dashed horizontal lines indicate the ±20% deviation (acceptance criterion). Supplemental Figure S3. Analysis of correlation and agreement of patient data. Scatter plot (A) and Bland-Altman analysis (B) for SUVpeak of reduced acquisition time versus SUVpeak of full acquisition time PET images for OSEM-TOF reconstructions. Scatter plot (C) and Bland-Altman analysis (D) for SUVpeak of reduced acquisition time versus SUVpeak of full acquisition time PET images for OSEM-TOF+PSF image reconstructions.

Poster-Abstract

Introduction: While [¹⁷⁷Lu]Lu-PSMA radioligand therapy is currently only applied in end-stage metastatic castrate-resistant prostate cancer (mCRPC) patients, also low-volume hormone-sensitive metastatic prostate cancer (mHSPC) patients can benefit from it. However, there are toxicity concerns related to the sink effect in low-volume disease. This prospective study aims to determine the kinetics of [¹⁷⁷Lu]Lu-PSMA in mHSPC patients, analyzing the doses to organs at risk (salivary glands, kidneys, liver, and bone marrow) and tumor lesions < 1 cm diameter. Methods: Ten mHSPC patients underwent two cycles of [¹⁷⁷Lu]Lu-PSMA therapy. Three-bed position SPECT/CT was performed at 5 time points after each therapy. Organ dosimetry and lesion dosimetry were performed using commercial software and a manual approach, respectively. Correlation between absorbed index lesion dose and treatment response (PSA drop of > 50% at the end of the study) was calculated and given as Spearman’s r and p-values. Results: Kinetics of [¹⁷⁷Lu]Lu-PSMA in mHSPC patients are comparable to those in mCRPC patients. Lesion absorbed dose was high (3.25 ± 3.19 Gy/GBq) compared to organ absorbed dose (salivary glands: 0.39 ± 0.17 Gy/GBq, kidneys: 0.49 ± 0.11 Gy/GBq, liver: 0.09 ± 0.01 Gy/GBq, bone marrow: 0.017 ± 0.008 Gy/GBq). A statistically significant correlation was found between treatment response and absorbed index lesion dose (p = 0.047). Conclusions: We successfully performed small lesion dosimetry and showed that the tumor sink effect in mHSPC patients is of less concern than was expected. Tumor-to-organ ratio of absorbed dose was high and tumor uptake correlates with PSA response. Additional treatment cycles are legitimate in terms of organ toxicity and could lead to better tumor response.

Additional file 1. Employed phantoms: a) NEMA IQ - Image quality phantom; b) Small tumor phantom and c) Bone-lung phantom. d-f) VOI delineations for the image analysis.

Purpose: The determination of the glomerular filtration rate (GFR) is decisive for a variety of clinical issues, for example, to monitor the renal function in radionuclide therapy patients. Renal scintigraphy using glomerularly filtered tracers allows combined acquisition of renograms and GFR estimation but requires repeated blood sampling for several hours. In contrast, dynamic PET imaging using the glomerularly filtered tracer [⁶⁸Ga]Ga-DOTA bears the potential to non-invasively estimate the GFR by compartmental kinetic modelling. Here, we report the, to our knowledge, first comparison of human renal dynamic [⁶⁸Ga]Ga-DOTA PET imaging in comparison to renal scintigraphy and compare PET-derived to serum creatinine-derived GFR measurements. Methods: Dynamic [⁶⁸Ga]Ga-DOTA PET data were acquired for 30 min immediately after tracer injection in 12 patients. PET and renal scintigraphy images were visually interpreted in a consensus read by three nuclear medicine physicians. The functional renal cortex was segmented to obtain time-activity curves. The arterial input function was estimated from the PET signal in the abdominal aorta. Single-compartmental tracer kinetic modelling was performed to calculate the GFR using complete 30-min (GFRPET₋₃₀) and reduced 15-min PET data sets (GFRPET₋₁₅) to evaluate whether a shorter acquisition time is sufficient for an accurate GFR estimation. A modified approach excluding minutes 2 to 10 was applied to reduce urinary spill-over effects. Serum creatinine-derived GFRCKD (CKD-EPI-formula) was used as reference standard. Results: PET image interpretation revealed the same findings as conventional scintigraphy (2/12 patients with both- and 1/12 patients with right-sided urinary obstruction). Model fit functions were substantially improved for the modified approach to exclude spill-over. Depending on the modelling approach, GFRCKD and both GFRPET₋₃₀ and GFRPET₋₁₅ were well correlated with interclass correlation coefficients (ICCs) from 0.74 to 0.80 and Pearson’s correlation coefficients (PCCs) from 0.74 to 0.81. For a subgroup of patients with undisturbed urinary efflux (n = 9), correlations were good to excellent (ICCs from 0.82 to 0.95 and PCCs from 0.83 to 0.95). Overall, GFRPET₋₃₀ and GFRPET₋₁₅ were excellently correlated (ICCs from 0.96 to 0.99 and PCCs from 0.96 to 0.99). Conclusion: Renal [⁶⁸Ga]Ga-DOTA PET can be a suitable alternative to conventional scintigraphy. Visual assessment of PET images and conventional renograms revealed comparable results. GFR values derived by non-invasive single-compartmental-modelling of PET data show a good correlation to serum creatinine-derived GFR values. In patients with undisturbed urinary efflux, the correlation was excellent. Dynamic PET data acquisition for 15 min is sufficient for visual evaluation and GFR derivation.

Poster-Abstract