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This paper presents the proof-of-concept study of an adaptor allowing the combination of a gamma probe with ultrasound (US) imaging, intending to improve the detectability of sentinel lymph nodes (SLNs). The performance of the adaptor in US imaging, in terms of depth of penetration and distance accuracy, and gamma scanning, in terms of sensitivity and spatial resolution, was investigated. We observed that the quality of the US imaging through the adaptor was promising and close to that of normal US imaging. However, the performance of the gamma probe through the adaptor was fairly poor, necessitating the improvement in the design of the adaptor for better gamma scanning. This study shall provide a basis for the development of a handheld gamma-US scanner for interventional procedures and small field-of-view (FOV) imaging in the future.

Background: Historically, [131I]I has been a common isotope in radionuclide therapy, with [177Lu]Lu‐labelled radiopharmaceuticals now seeing a surge in use. These can include no‐carrier‐added or carrier‐added [177Lu]Lu with slight impurities of [177mLu]Lu with a significantly longer half‐life than [131I]I. Wastewater from therapy wards can contain a mixture of these radioisotopes. In some countries, national regulations require wastewater to be stored in dedicated systems before it is discharged into the public sewage system. To fulfill legal requirements, the nuclide specific activity concentration must be verified. Purpose: We evaluate a method for determining the activity concentration of [177mLu]Lu /[177Lu]Lu at equilibrium and [131I]I in pure and mixed samples in order to prove that the determined values are reliably below the limits for release. Methods: We analysed the emitted energy spectrum of 1 L samples with a wastewater counter using an energy window‐based approach by evaluating measurements from two different time points. Based on the law of decay and the time and energy‐dependent measured values, equation systems were set up to calculate the count rates for [131I]I and [177mLu]Lu, which were converted into activity concentration using calibration factors. Results: There is strong linear correlation between the nominal and determined activity concentrations (correlation coefficients R = 0.99; coefficient of determinations R2 = 0.99). We underestimate the actual activity concentration by a median of −1.4% for [177mLu]Lu and overestimate the activity concentration for [131I]I by a median of 7.1%. Conclusion: We show that an undercut of the clearance levels for material release is measurable. We analyse and determine activity concentrations of mixed samples consisting of [131I]I and [177mLu]Lu/[177Lu]Lu in equilibrium. The method is simple to implement using a conventional wastewater counter, however with a slightly increased effort, as two samples and measurements are required. The methodology can be adapted for the analysis of other nuclide mixtures. [ABSTRACT FROM AUTHOR]

Dose optimization in computed tomography (CT) is crucial, especially in CT fluoroscopy (fluoro-CT) used for real-time navigation, affecting both patient and operator safety. This study evaluated the impact of spectral X-ray filtering using a tin filter (Sn filter), and a method called partial-angle computed tomography (PACT), which involves segmentally switching off the X-ray tube current at the ambient dose rate H ˙ * (10) at the interventional radiologist's (IR) position. Measurements were taken at two body regions (upper body: head/neck; lower body: lower legs/feet) using a 120 kV X-ray tube voltage, 3 × 5.0 mm CT collimation, 0.5 s rotation speed, and X-ray tube currents of 43 Eff.mAs (without Sn filter) and 165 Eff.mAs (with Sn filter). The study found significant dose reductions in both body regions when using the Sn filter and PACT together. For instance, in the upper body region, the combination protocol reduced H ˙ * (10) from 11.8 µSv/s to 6.1 µSv/s (p < 0.0001) compared to the protocol without using these features. Around 8% of the reduction (about 0.5 µSv/s) is attributed to the Sn filter (p = 0.0005). This approach demonstrates that using the Sn filter along with PACT effectively minimizes radiation exposure for the IR, particularly protecting areas like the head/neck, which can only be insufficiently covered by (standard) radiation protection material. [ABSTRACT FROM AUTHOR]

Background: To compare Gd-ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and 99mTc-labelled mebrofenin hepatobiliary scintigraphy (HBS) as imaging-based liver function tests after unilateral radioembolisation (RE) in patients with primary or secondary liver malignancies. Methods: Twenty-three patients with primary or secondary liver malignancies who underwent Gd-EOB-DTPA-enhanced MRI within a prospective study (REVoluTion) were evaluated. REVoluTion was a prospective open-label, non-randomised, therapy-optimising study of patients undergoing right-sided or sequential RE for contralateral liver hypertrophy at a single centre in Germany. MRI and hepatobiliary scintigraphy were performed before RE (baseline) and 6 weeks after (follow-up). This exploratory subanalysis compared liver enhancement on hepatobiliary phase MRI normalised to the spleen (liver-to-spleen ratio (LSR)) and the muscle (liver-to-muscle ratio (LMR)) with mebrofenin uptake on HBS for the total liver (TL) and separately for the right (RLL) and left liver lobe (LLL). Results: Mebrofenin uptake at baseline and follow-up each correlated significantly with LSR and LMR on MRI for TL (≤ 0.013) and RLL (≤ 0.049). Regarding the LLL, mebrofenin uptake correlated significantly with LMR (baseline, p = 0.013; follow-up, p = 0.004), whereas with LSR, a borderline significant correlation was only seen at follow-up (p = 0.051; p = 0.046). Conclusion: LSRs and LMR correlate with mebrofenin uptake in HBS. This study indicates that Gd-EOB-DTPA-enhanced MRI and 99mTc-labelled mebrofenin HBS may equally be used to assess an increase in contralateral liver lobe function after right-sided RE. Relevance statement: MRI may be a convenient and reliable method for assessing the future liver remnant facilitating treatment planning and monitoring of patients after RE-induced hypertrophy induction. Key points: • Both MRI and HBS can assess liver function after RE. • Liver enhancement on MRI correlates with mebrofenin uptake on HBS. • MRI might be a convenient alternative for estimating future liver remnants after hypertrophy induction. [ABSTRACT FROM AUTHOR]

Background: Nuclear medicine therapies using [177Lu]Lu‐labeled radiopharmaceuticals have increased significantly in recent years. Some of these radiopharmaceuticals contain long‐lived impurities of [177mLu]Lu. Identification of this specific contamination and its quantification is important in different scenarios. Purpose: In this study, standard measurement hardware used for handling radioisotopes was evaluated for the measurement of [177mLu]Lu and [177Lu]Lu at equilibrium. Device‐specific detection limits (LODs) for [177mLu]Lu were determined according to international standards and then validated. Methods: The LODs were determined according to the international standard ISO 11929‐1 for [177mLu]Lu for five identical portable contamination monitors (PCMs), a wastewater counter (WWC), and a release counter system (RCS) at different measuring times. Subsequent activity measurements of the defined samples were used to validate the linearity of the measurement instruments down to the LOD for each system. Results: The average LOD across all PCMs was 0.249 ± 0.009 and 0.129 ± 0.005 Bq/cm2 for 10 and 30 s measurements, respectively. The LODs of WWC varied between 3.3 and 4.7 Bq/L for measurement times of 300 s and 0.8–1.3 Bq/L for 3600 s depending on the energy window studied. The LOD of the RCS depended on the container volume and was 0.08 Bq/g for the 50 L container at 60 s measurement. The measurements for all examined devices were linear down to the LOD (correlation coefficient R ≥ 0.96; coefficient of determination R2 ≥ 0.92). Conclusions: All investigated measuring instruments (PCM, WWC, RCS) were suitable for the determination of [177mLu]Lu at equilibrium, and their specific LODs were determined. Based on the measurements performed, activity is overestimated; however, this is tolerable because assumptions and measurements in the context of radiation protection should be conservative. [ABSTRACT FROM AUTHOR]

Background: The introduction of hybrid SPECT/CT devices enables quantitative imaging in SPECT, providing a methodological setup for quantitation using SPECT tracers comparable to PET/CT. We evaluated a specific quantitative reconstruction algorithm for SPECT data using a 99mTc-filled NEMA phantom. Quantitative and qualitative image parameters were evaluated for different parametrizations of the acquisition and reconstruction protocol to identify an optimized quantitative protocol. Results: The reconstructed activity concentration (ACrec) and the signal-to-noise ratio (SNR) of all examined protocols (n = 16) were significantly affected by the parametrization of the weighting factor k used in scatter correction, the total number of iterations and the sphere volume (all, p < 0.0001). The two examined SPECT acquisition protocols (with 60 or 120 projections) had a minor impact on the ACrec and no significant impact on the SNR. In comparison to the known AC, the use of default scatter correction (k = 0.47) or object-specific scatter correction (k = 0.18) resulted in an underestimation of ACrec in the largest sphere volume (26.5 ml) by − 13.9 kBq/ml (− 16.3%) and − 7.1 kBq/ml (− 8.4%), respectively. An increase in total iterations leads to an increase in estimated AC and a decrease in SNR. The mean difference between ACrec and known AC decreased with an increasing number of total iterations (e.g., for 20 iterations (2 iterations/10 subsets) = − 14.6 kBq/ml (− 17.1%), 240 iterations (24i/10s) = − 8.0 kBq/ml (− 9.4%), p < 0.0001). In parallel, the mean SNR decreased significantly from 2i/10s to 24i/10s by 76% (p < 0.0001). Conclusion: Quantitative SPECT imaging is feasible with the used reconstruction algorithm and hybrid SPECT/CT, and its consistent implementation in diagnostics may provide perspectives for quantification in routine clinical practice (e.g., assessment of bone metabolism). When combining quantitative analysis and diagnostic imaging, we recommend using two different reconstruction protocols with task-specific optimized setups (quantitative vs. qualitative reconstruction). Furthermore, individual scatter correction significantly improves both quantitative and qualitative results. [ABSTRACT FROM AUTHOR]

Background: Iterative computed tomography (CT) image reconstruction shows high potential for the preservation of image quality in diagnostic CT while reducing patients' exposure; it has become available for low-dose CT (LD-CT) in high-end hybrid imaging systems (e.g. single-photon emission computed tomography [SPECT]-CT). Purpose: To examine the effect of an iterative CTreconstruction algorithm on image quality, image noise, detectability, and the reader's confidence for LD-CT data by a subjective assessment. Material and Methods: The LD-CT data were validated for 40 patients examined by an abdominal hybrid SPECT-CT (U=120 kV, I=40 mA, pitch=1.375). LD-CT was reconstructed using either filtered back projection (FBP) or an iterative image reconstruction algorithm (Adaptive Statistical Iterative Reconstruction [ASIR]VR) with different parameters (ASIR levels 50% and 100%). The data were validated by two independent blinded readers using a scoring system for image quality, image noise, detectability, and reader confidence, for a predefined set of 16 anatomic substructures. Results: The image quality was significantly improved by iterative reconstruction of the LD-CT data compared with FBP (P≥0.0001). While detectability increased in only 2/16 structures (P≥0.03), the reader's confidence increased significantly due to iterative reconstruction (P≥0.002). Meanwhile, at the ASIR level of 100%, the detectability in bone structure was highly reduced (P=0.003). Conclusion: An ASIR level of 50% represents a good compromise in abdominal LD-CT image reconstruction. The specific ASIR level improved image quality (reduced image noise) and reader confidence, while preserving detectability of bone structure. [ABSTRACT FROM AUTHOR]

In peptide receptor radionuclide therapy (PRRT) of patients with neuroendocrine neoplasias (NENs), intratherapeutic dosimetry is mandatory for organs at risk (e.g. kidneys) and tumours. We evaluated commercial dosimetry software (Dosimetry Toolkit) using varying imaging scenarios, based on planar and/or tomographic data, regarding the differences in calculated organ/tumour doses and the use for clinical routines. A total of 16 consecutive patients with NENs treated by PRRT with 177Lu-DOTATATE were retrospectively analysed. Single-photon emission computed tomography (SPECT)/low-dose computed tomography (CT) of the thorax and abdomen and whole body (WB) scintigraphy were acquired up to 7 days p.i. (at a maximum of five imaging time points). Different dosimetric scenarios were evaluated: (1) a multi-SPECT-CT scenario using SPECT/CT only; (2) a planar scenario using WB scintigraphy only; and (3) a hybrid scenario using WB scintigraphy in combination with a single SPECT/low-dose CT. Absorbed doses for the kidneys, liver, spleen, lungs, bladder wall and tumours were calculated and compared for the three different scenarios. The mean absorbed dose for the kidneys estimated by the multi-SPECT-CT, the planar and the hybrid scenario was 0.5 ± 0.2 Sv GBq-1, 0.8 ± 0.4 Sv GBq-1 and 0.6 ± 0.3 Sv GBq-1, respectively. The absorbed dose for the residual organs was estimated higher by the planar scenario compared to the multi-SPECT-CT or hybrid scenario. The mean absorbed tumour doses were 2.6 ± 1.5 Gy GBq-1 for the multi-SPECT-CT, 3.1 ± 2.2 Gy GBq-1 for the hybrid scenario and 5.3 ± 6.3 Gy GBq-1 for the planar scenario. SPECT-based dosimetry methods determined significantly lower kidney doses than the WB scintigraphy-based method. Dosimetry based completely on SPECT data is time-consuming and tedious. Approaches combining SPECT/CT and WB scintigraphy have the potential to ensure compromise between accuracy and user-friendliness. [ABSTRACT FROM AUTHOR]

Interactions of pairs of scroll wavesin three-dimensional excitable media were studied experimentally inthe Belousov–Zhabotinsky reaction by optical tomography. Thebehavior of two scroll waves depended on the distance dbetween their filaments. When the interfilament distance was shorterthan the wavelength λ of the scroll waves (but larger than thediameter of the spiral core), the filaments repelled each other. Once d≈ λ, the two scroll waves synchronized, rotatingaround their filaments with both a common rotation frequency and acommon pitch. The interfilament distance of synchronized scroll wavesdid not change. When fluctuations broke the symmetry of the rotationperiods, the scroll with higher rotation frequency displaced the slowerrotating one, until the latter was ousted or even annihilated. Thesebehaviors were independent of the sense of rotation (co- or counter-rotating),the filament dynamics (rigidly rotating or meandering tip motion intwo-dimensional media), and the presence or absence of a gradientof excitability parallel to the filaments. [ABSTRACT FROM AUTHOR]

Background: Historically, [ 131 I]I has been a common isotope in radionuclide therapy, with [ 177 Lu]Lu-labelled radiopharmaceuticals now seeing a surge in use. These can include no-carrier-added or carrier-added [ 177 Lu]Lu with slight impurities of [ 177m Lu]Lu with a significantly longer half-life than [ 131 I]I. Wastewater from therapy wards can contain a mixture of these radioisotopes. In some countries, national regulations require wastewater to be stored in dedicated systems before it is discharged into the public sewage system. To fulfill legal requirements, the nuclide specific activity concentration must be verified., Purpose: We evaluate a method for determining the activity concentration of [ 177m Lu]Lu /[ 177 Lu]Lu at equilibrium and [ 131 I]I in pure and mixed samples in order to prove that the determined values are reliably below the limits for release., Methods: We analysed the emitted energy spectrum of 1 L samples with a wastewater counter using an energy window-based approach by evaluating measurements from two different time points. Based on the law of decay and the time and energy-dependent measured values, equation systems were set up to calculate the count rates for [ 131 I]I and [ 177m Lu]Lu, which were converted into activity concentration using calibration factors., Results: There is strong linear correlation between the nominal and determined activity concentrations (correlation coefficients R = 0.99; coefficient of determinations R 2  = 0.99). We underestimate the actual activity concentration by a median of -1.4% for [ 177m Lu]Lu and overestimate the activity concentration for [ 131 I]I by a median of 7.1%., Conclusion: We show that an undercut of the clearance levels for material release is measurable. We analyse and determine activity concentrations of mixed samples consisting of [ 131 I]I and [ 177m Lu]Lu/[ 177 Lu]Lu in equilibrium. The method is simple to implement using a conventional wastewater counter, however with a slightly increased effort, as two samples and measurements are required. The methodology can be adapted for the analysis of other nuclide mixtures., (© 2024 The Author(s). Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

Background: To compare Gd-ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and 99m Tc-labelled mebrofenin hepatobiliary scintigraphy (HBS) as imaging-based liver function tests after unilateral radioembolisation (RE) in patients with primary or secondary liver malignancies., Methods: Twenty-three patients with primary or secondary liver malignancies who underwent Gd-EOB-DTPA-enhanced MRI within a prospective study (REVoluTion) were evaluated. REVoluTion was a prospective open-label, non-randomised, therapy-optimising study of patients undergoing right-sided or sequential RE for contralateral liver hypertrophy at a single centre in Germany. MRI and hepatobiliary scintigraphy were performed before RE (baseline) and 6 weeks after (follow-up). This exploratory subanalysis compared liver enhancement on hepatobiliary phase MRI normalised to the spleen (liver-to-spleen ratio (LSR)) and the muscle (liver-to-muscle ratio (LMR)) with mebrofenin uptake on HBS for the total liver (TL) and separately for the right (RLL) and left liver lobe (LLL)., Results: Mebrofenin uptake at baseline and follow-up each correlated significantly with LSR and LMR on MRI for TL (≤ 0.013) and RLL (≤ 0.049). Regarding the LLL, mebrofenin uptake correlated significantly with LMR (baseline, p = 0.013; follow-up, p = 0.004), whereas with LSR, a borderline significant correlation was only seen at follow-up (p = 0.051; p = 0.046)., Conclusion: LSRs and LMR correlate with mebrofenin uptake in HBS. This study indicates that Gd-EOB-DTPA-enhanced MRI and 99m Tc-labelled mebrofenin HBS may equally be used to assess an increase in contralateral liver lobe function after right-sided RE., Relevance Statement: MRI may be a convenient and reliable method for assessing the future liver remnant facilitating treatment planning and monitoring of patients after RE-induced hypertrophy induction., Key Points: • Both MRI and HBS can assess liver function after RE. • Liver enhancement on MRI correlates with mebrofenin uptake on HBS. • MRI might be a convenient alternative for estimating future liver remnants after hypertrophy induction., (© 2024. The Author(s).)

Background: Nuclear medicine therapies using [ 177 Lu]Lu-labeled radiopharmaceuticals have increased significantly in recent years. Some of these radiopharmaceuticals contain long-lived impurities of [ 177m Lu]Lu. Identification of this specific contamination and its quantification is important in different scenarios., Purpose: In this study, standard measurement hardware used for handling radioisotopes was evaluated for the measurement of [ 177m Lu]Lu and [ 177 Lu]Lu at equilibrium. Device-specific detection limits (LODs) for [ 177m Lu]Lu were determined according to international standards and then validated., Methods: The LODs were determined according to the international standard ISO 11929-1 for [ 177m Lu]Lu for five identical portable contamination monitors (PCMs), a wastewater counter (WWC), and a release counter system (RCS) at different measuring times. Subsequent activity measurements of the defined samples were used to validate the linearity of the measurement instruments down to the LOD for each system., Results: The average LOD across all PCMs was 0.249 ± 0.009 and 0.129 ± 0.005 Bq/cm 2 for 10 and 30 s measurements, respectively. The LODs of WWC varied between 3.3 and 4.7 Bq/L for measurement times of 300 s and 0.8-1.3 Bq/L for 3600 s depending on the energy window studied. The LOD of the RCS depended on the container volume and was 0.08 Bq/g for the 50 L container at 60 s measurement. The measurements for all examined devices were linear down to the LOD (correlation coefficient R ≥ 0.96; coefficient of determination R 2  ≥ 0.92)., Conclusions: All investigated measuring instruments (PCM, WWC, RCS) were suitable for the determination of [ 177m Lu]Lu at equilibrium, and their specific LODs were determined. Based on the measurements performed, activity is overestimated; however, this is tolerable because assumptions and measurements in the context of radiation protection should be conservative., (© 2022 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

Objectives: To investigate how metabolic function of the contralateral liver lobe is affected by unilateral radioembolization (RE), and to compare the changes in volume and metabolic function., Background: Unilateral RE induces contralateral liver hypertrophy, but it is unknown if metabolic liver function improves in line with volume increases., Methods: This prospective open-label, nonrandomized, therapy-optimizing study included all consecutive patients undergoing right-sided or sequential 90 Y-RE for liver malignancies without underlying liver disease or biliary obstruction at a single center in Germany. Magnetic resonance imaging volumetry and hepatobiliary scintigraphy were performed immediately before RE and approximately 6 weeks after RE., Results: Twenty-three patients were evaluated (11 metastatic colorectal cancer, 4 cholangiocellular carcinoma, 3 metastatic breast cancer, 1 each of metastatic neuroendocrine tumor, hepatocellular carcinoma, renal cell carcinoma, oesophageal cancer, pancreatic ductal adenocarcinoma). In the untreated contralateral left liver lobe, mean (SD) metabolic function significantly increased from 1.34 (0.76) %/min/m 2 at baseline to 1.56 (0.75) %/min/m 2 6 weeks after RE ( P  = 0.024). The mean (SD) functional volume (liver volume minus tumor volume) of the left liver lobe significantly increased from baseline (407.3 [170.3] mL) to follow-up (499.1 [209.8] mL; P  <   0.01), with an equivalent magnitude to the metabolic function increase. There were no reports of grade ≥3 adverse events., Conclusion: This study indicates that unilobar RE produces a significant increase in the metabolic function, and equivalent volume increase, of the contralateral lobe. RE may be a useful option to induce hypertrophy of the future liver remnant before surgical resection of primary or secondary liver malignancies., Competing Interests: B.G. has received research grants from Sirtex Medical as well as lecture honoraria and travel grants from Sirtex Medical, Amgen, Merck, Roche, Novartis and B. Braun Travacare, and receives honoraria for participation on advisory boards from Terumo, Sirtex Medical and Amgen. H.A. receives lecture fees from Norgine, Pfizer, Novartis, GE, Sirtex Medical as well as research grants from Pfizer. R.D. receives lecture honoraria from Sirtex Medical. M.P. receives research grants from Bayer and Sirtex Medical as well as lecture honoraria from Sirtex Medical. M.S. receives research grants from Bayer and Sirtex Medical as well as lecture honoraria from Siemens, Cook, Boston Scientific, Sirtex Medical, Falk Foundation, Bayer and receives honoraria for participation on advisory boards from Sirtex Medical, Bayer and Siemens. The remaining authors declare that they have nothing to disclose., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Objectives: Low-dose-computed tomography (LD-CT) is used in nuclear medicine hybrid imaging (e.g., SPECT/CT) for attenuation correction of emission data and anatomical correlation of findings. However, there are currently no standards for image quality (e. g., detectability) comparable to those for diagnostic CT. Therefore, the aim of this explorative study was to evaluate retrospective LDCT data in terms of CT image quality and detectability of anatomical structures., Methods: Two readers blindly scored abdominal LD-CT images (n = 40 patients) in terms of detectability (n = 20 structures/patient), image quality, and readers' confidence in scoring the image quality for a clinically hybrid imaging protocol. Results were analysed by ANOVA to identify factors (e. g., anatomical structures) that influenced performance scores. The inter-rater agreement was evaluated by determining the chance-corrected Cohen's Kappa coefficient., Results: Image noise was acceptable for anatomical correlation in 96.1 % of the readings with an almost perfect inter-rater agreement (K BP = 0.85). A detectability of at least 80 % was observed in 13/20 (K BP ≥ 0.7) and 90 % in 9/20 (K BP ≥ 0.85) of the structures analysed by both readers. The confidence of both readers in scoring image quality was at least sufficient in 98.8 % of the examined patients (K BP = 0.95)., Conclusion: Although LD-CT protocols commonly used in hybrid imaging have a poor image quality not suitable for primary CT diagnostics, they enable detection of a variety of anatomical structures. LDCT can therefore also be referenced in the associated reports for anatomical correlation of findings from SPECT imaging., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (Georg Thieme Verlag.)

Aim: 223 Radium-dichloride ( 223 Ra) administration is an upcoming therapeutic option in patients with castration-resistant metastatic prostate cancer (mCRPC), whose renal and faecal excretion of 223 Ra has been primarily estimated from data of a phase-I clinical trial in patients with normal renal function. In the rare case of concomitant renal insufficiency requiring haemodialysis (HD), an estimation of the contamination of dialysate would be beneficial., Methods: The excretion of 223 Ra and its concentration in the dialysate in a patient with mCRPC and end-stage renal disease was examined for six consecutive treatment cycles. Dialysate samples were measured using a commercial system with NaI-scintillation detector., Results: HD showed a residual activity level in the remaining dialysate. The excreted activity was a median of 46.1 kBq (range = 42.0- 83.4 kBq) and 11.2 kBq (range = 8.4- 19.9 kBq) for the first (24 h post injection p.i.) and second HD (96 h p.i.), respectively. The activity concentration decreased significantly from a median of 4.18 kBq/l (range = 2.98-5.14 kBq/l) to 0.85 kBq/l (range = 0.69- 1.31 kBq/l, p < 0.0001). For all consecutive time points, the activity concentration further decreased significantly (p < 0.0001). The activity concentration of dialysate from HD performed 125.4 h p.i. [95 % confidence interval = 120.5-130.4 h p.i.] reached the threshold for unrestricted waste disposal., Conclusion: The observed extraction of 223 Ra by HD exceeded the data determined from the phase-I study. The activity concentration in the dialysate observed for the first HD's p.i. was above the threshold for unrestricted disposal of radioactive waste in Germany. Therefore, the specific requirement for waste handling has to be followed to fulfil the radiation protection regulations.