Background: Current diagnosis of Transthyretin-related Amyloidosis (ATTR) using bone scintigraphy is primarily based on visual scoring and semi-quantitative indices. With the introduction of new potential life-prolonging drugs for ATTR, a more precise quantification of myocardial amyloid burden is desirable for improved response prediction and therapy monitoring. Methods: At first, quantification experiments using an anthropomorphic thorax phantom were performed. Second, 32 patients underwent both planar whole body [^99mTc]- 3,3-Diphosphono-1,2-Propanodicarboxylic Acid (DPD)-scintigraphy and quantitative Single-Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) of the thorax. SPECT/CT standardized myocardial uptake values SUVpeak and SUVpeak normalized to bone uptake (nSUVpeak) were determined. Results: Phantom measurements showed a strong linear relationship between the activity in the myocardial insert and the measured activity (r = 0.9998, p = 0.01), but the measured activity was systematically underestimated by approximately 30%. Receiver operating characteristics (ROC) analysis revealed a 100% sensitivity and specificity at a cut-off of 3.1 for SUVpeak for the differentiation of both patient groups. Conclusion: SUV quantification of ATTR amyloid burden is feasible using novel SPECT/CT technology. With a SUVpeak cut-off of 3.1, patients with Perugini grade 2 and 3 could be clearly separated from those with Perugini grade 0 and 1. Besides ATTR diagnostics, quantification of amyloid deposits could potentially be used for therapy monitoring and prognostication in patients with cardiac ATTR.

Background: [¹⁷⁷Lu]Lu-PSMA-617 radioligand therapy (PSMA-RLT) could affect kidney and salivary gland functions in metastatic castration-resistant prostate cancer (mCRPC) patients. Methods: We retrospectively analyzed clinical, renal, and salivary scintigraphy data and salivary [⁶⁸Ga]Ga-PSMA-11 ligand PET scan measures such as metabolic volume and SUVmax values of 27 mCRPC men (mean age 71 ± 7 years) before and 4 weeks after receiving three cycles of PSMA-RLT every 4 weeks. Twenty-two patients additionally obtained renal and salivary scintigraphy prior to each cycle. A one-way ANOVA, post-hoc Scheffé test and Cochran’s Q test were applied to assess organ toxicity. Results: In total, 54 PSMA PET scans, 98 kidney, and 98 salivary scintigraphy results were evaluated. There were no significant differences for the ejection fraction, peak time, and residual activity after 5 min for both parotid and submandibular glands prior to each cycle and 4 weeks after the last cycle. Similarly, no significant differences in serum creatinine and renal scintigraphy parameters were observed prior to each cycle and 4 weeks after the last treatment. Despite there being no changes in the metabolic volume of both submandibular glands, SUVmax values dropped significantly (p < 0.05). Conclusion: Results evidenced no alterations in renal function and only minimal impairment of salivary function of mCRPC patients who acquired an intense PSMA-RLT regimen every 4 weeks.

Background With the introduction of several drugs for the therapy of transthyretin-related amyloidosis (ATTR) which slow down the disease, early detection of polyneuropathy (PNP) is becoming increasingly of interest. [99mTc]-3,3-Diphosphono-1,2-Propanodicarboxylic Acid (DPD) bone scintigraphy, which is used for the diagnosis of cardiac (c)ATTR, can possibly make an important contribution in the identification of patients at risk for PNP. Methods Fifty patients with cATTR, who underwent both planar whole-body DPD scintigraphy and nerve conduction studies (NCS) were retrospectively evaluated. A subgroup of 22 patients also underwent quantitative SPECT/CT of the thorax from which Standardized Uptake Values (SUVpeak) in the subcutaneous fat tissue of the left axillar region were evaluated. Results The Perugini score was significantly increased in patients with cATTR and additional diagnosis of PNP compared to patients without (2.51 ± 0.51 vs 2.13 ± 0.52; P = 0.03). Quantitative SPECT/CT revealed that DPD uptake in the subcutaneous fat of the left axillar region was significantly increased in cATTR patients with compared to patients without (1.36 ± 0.60 vs 0.74 ± 0.52; P = 0.04). Conclusion This study suggests that DPD bone scintigraphy is a useful tool for identification of patients with cATTR and a risk for PNP due to increased DPD soft tissue uptake.

Background: We investigated the response rate and degree of toxicity of a second course of three cycles of [¹⁷⁷Lu]Lu-PSMA radioligand therapy (PSMA-RLT) every 4 weeks in mCRPC patients. Methods: Forty-three men (71.5 ± 6.6 years, median PSA 40.8 (0.87–1358 µg/L)) were studied. The response was based on the PSA level 4 weeks after the third cycle. The laboratory parameters before and one month after the last cycle were compared. Kaplan–Meier methods were used to estimate the progression-free survival (PFS) and overall survival (OS), and the Cox regression model was performed to find predictors of survival. Results: Twenty-six patients (60.5%) exhibited a PSA reduction (median PSA declined from 40.8 to 20.2, range 0.6–1926 µg/L, p = 0.002); 18 (42%) and 8 (19%) patients showed a PSA decline of ≥50% and ≥80%, respectively. The median OS and PFS were 136 and 31 weeks, respectively. The patients with only lymph node metastases survived longer (p = 0.02), whereas the patients with bone metastases had a shorter survival (p = 0.03). In the multivariate analysis, only the levels of PSA prior to the therapy remained significant for OS (p < 0.05, hazard ratio 2.43, 95% CI 1.01–5.87). The levels of hemoglobin (11.5 ± 1.7 g/dL vs. 11 ± 1.6 g/dL, p = 0.006) and platelets (208 ± 63 g/L vs. 185 ± 63 g/L, p = 0.002) significantly decreased one month after cycle three, though only two grade 3 anemia and one grade 3 thrombocytopenia were recorded. Conclusion: A further intensive PSMA-RLT course is well tolerated in mCRPC patients and associated with promising response rates and OS.

The tracer [¹¹C]meta-Hydroxyephedrine ([¹¹C]mHED) is one of the most applied PET tracers for cardiac imaging, whose radiosynthesis was already reported in 1990. While not stated in the literature, separation difficulties and an adequate formulation of the product are well known challenges in its production. Furthermore, the precursor (metaraminol) is also a substrate for the norepinephrine transporter, and can therefore affect the image quality. This study aims at optimizing the synthetic process of [¹¹C]mHED and investigating the effect of the apparent molar activity (sum of mHED and metaraminol) in patients and animals. The main optimization was the improved separation through reverse phase-HPLC by a step gradient and subsequent retention of the product on a weakly-cationic ion exchange cartridge. The µPET/µCT was conducted in ten rats (ischemic model) and the apparent molar activity was correlated to the VOI- and SUV-ratio of the myocardium/intra-ventricular blood pool. Moreover, nine long-term heart transplanted and five Morbus Fabry patients underwent PET and MRI imaging for detection of changes in the sympathetic innervation. In summary, the fully-automated synthesis and optimized purification method of [¹¹C]mHED is easily applicable and reproducible. Moreover, it was shown that the administered apparent molar activities had a negligible effect on the imaging quality.