A method for tumor dosimetry based on hybrid planar‐SPECT/CT images and semiautomatic segmentation

Roth, Daniel; Gustafsson, Johan; Sundlöv, Anna; Gleisner, Katarina Sjögreen

doi:10.1002/mp.13178

Cited by 21 publications

(31 citation statements)

References 43 publications

(93 reference statements)

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“…The investigated sampling schedules depended on the simulated dosimetric approach. For the hybrid planar/SPECT method, sampling schedules comprising 2-4 planar images and one SPECT/CT measurement were investigated [14,20,[25][26][27][28]. Considering working hours [24], following 24 TPs for planar images were used: 1, 2, 3, 4, 20, 22, 24, 26, 28, 44, 48, 52, 68, 72, 76, 92, 96, 100, 116, 120, 124, 144, 168 and 192 h p.i.…”

Section: Sampling Schedulesmentioning

confidence: 99%

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

et al. 2020

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Background: Individualized dosimetry is recommended for [ 177 Lu]Lu-PSMA radioligand therapy (RLT) which is resource-intensive and protocols are often not optimized. Therefore, a simulation study was performed focusing on the determination of efficient optimal sampling schedules (OSS) for renal and tumour dosimetry by investigating different numbers of time points (TPs). Methods: Sampling schedules with 1-4 TPs were investigated. Time-activity curves of the kidneys and two tumour lesions were generated based on a physiologically based pharmacokinetic (PBPK) model and biokinetic data of 13 patients who have undergone [ 177 Lu]Lu-PSMA I&T therapy. Systematic and stochastic noise of different ratios was considered when modelling time-activity data sets. Time-integrated activity coefficients (TIACs) were estimated by simulating the hybrid planar/SPECT method for schedules comprising at least two TPs. TIACs based on one single SPECT/ CT measurement were estimated using an approximation for reducing the number of fitted parameters. For each sampling schedule, the root-mean-squared error (RMSE) of the deviations of the simulated TIACs from the ground truths for 1000 replications was used as a measure for accuracy and precision. Results: All determined OSS included a late measurement at 192 h p.i., which was necessary for accurate and precise tumour TIACs. OSS with three TPs were identified to be 3-4, 96-100 and 192 h with an additional SPECT/CT measurement at the penultimate TP. Kidney and tumour RMSE of 6.4 to 7.7% and 6.3 to 7.8% were obtained, respectively. Shortening the total time for dosimetry to e.g. 96 h resulted in kidney and tumour RMSE of 6.8 to 8.3% and 9.1 to 11%, respectively. OSS with four TPs showed similar results as with three TPs. Planar images at 4 and 68 h and a SPECT/CT shortly after the 68 h measurement led to kidney and tumour RMSE of 8.4 to 12% and 12 to 16%, respectively. One single SPECT/CT measurement at 52 h yielded good approximations for the kidney TIACs (RMSE of 7.0%), but led to biased tumour TIACs. Conclusion: OSS allow improvements in accuracy and precision of renal and tumour dosimetry for [ 177 Lu]Lu-PSMA therapy with potentially less effort. A late TP is important regarding accurate tumour TIACs.

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Section: Sampling Schedulesmentioning

confidence: 99%

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

et al. 2020

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“…The simulated time‐activity data for planar imaging were fitted with a mono‐exponential function. The TIAC was then determined with the area under the TAC scaled with the simulated activity value of the quantitative SPECT/CT measurement according to

T I A C = \frac{A_{SPECT} (t_{SPECT})}{A_{planar} (t_{SPECT})} \cdot \frac{1}{A_{0}} \cdot \int_{0}^{\infty} A_{planar} (t) d t,

where A SPECT is the activity value of the simulated SPECT/CT measurement, A planar is the mono‐exponential biokinetic determined by fitting the simulated planar activity data, and A 0 is the injected activity . Furthermore, the TIACs estimated without a SPECT/CT measurement, that is, only with planar imaging, were also calculated.…”

Section: Methodsmentioning

confidence: 99%

“…where A SPECT is the activity value of the simulated SPECT/ CT measurement, A planar is the mono-exponential biokinetic determined by fitting the simulated planar activity data, and A 0 is the injected activity. 6,10,11,13,25 Furthermore, the TIACs estimated without a SPECT/CT measurement, that is, only with planar imaging, were also calculated. As noise was implemented in the simulation routine, 1000 replications were performed for each sampling schedule and virtual patient, that is, 13 9 1000 TIACs were simulated for each sampling schedule.…”

Section: C Simulation Of Renal Tiacsmentioning

confidence: 99%

“…This study focuses on the determination of OSS for renal dosimetry for 177 Lu‐PSMA I&T patients using the hybrid planar/SPECT method . This approach is recommended for dosimetry if quantitative SPECT scans cannot be acquired at multiple time points .…”

Section: Introductionmentioning

confidence: 99%

“…This study focuses on the determination of OSS for renal dosimetry for 177 Lu-PSMA I&T patients using the hybrid planar/SPECT method. 6,[10][11][12][13][14][15] This approach is recommended for dosimetry if quantitative SPECT scans cannot be acquired at multiple time points. 12,14 As the SPECT/CT measurement basically corrects the planar activity data for systematic errors, an enhanced noise model incorporating systematic and stochastic errors was used.…”

Section: Introductionmentioning

confidence: 99%

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Technical Note: Optimal sampling schedules for kidney dosimetry based on the hybrid planar/SPECT method in ¹⁷⁷Lu‐PSMA therapy

et al. 2019

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Purpose Accurate and precise renal dosimetry during 177Lu‐labeled prostate‐specific membrane antigen (PSMA) radioligand therapy is crucial for therapy decisions. Sampling schedules for estimating the necessary time‐integrated activity coefficients (TIACs) are not optimized and standardized for clinical practice. Therefore, a simulation study to determine optimal sampling schedules (OSSs) was performed on 13 virtual 177Lu‐PSMA I&T therapy patients. Method A total of 880 clinically feasible sampling schedules for planar imaging (three time points) were investigated. To simulate the hybrid planar/SPECT method, an additional quantitative SPECT/CT measurement following one planar image was considered. For each sampling schedule and patient, the activity values were generated separately. Measurement noise was modeled by drawing random numbers of log‐normal distributions. The used fractional standard deviations (FSD) differed depending on the imaging modality. For activity values assigned to planar imaging, systematic noise between 25% and 75% of the total noise was simulated. After fitting with a mono‐exponential function, the root‐mean‐squared errors of the deviations of the simulated TIACs from the ground truth for 1000 replications were used to determine the OSS. The uncertainties of the TIACs and renal dose coefficients were estimated. Results For the hybrid planar/SPECT method, OSSs were determined to be (3–4, 72–76, 124–144)  h post injection (p.i.) with the quantitative SPECT/CT scan shortly after the second measurement. The accuracy and precision of the determined TIACs were in the range of (−3.0 ± 6.2)% and (−1.0  ±  6.5)%. This precision was improved by a factor 2–3 compared to dosimetry based on planar images only. Similar results were obtained for the renal dose coefficients. The virtual patients' renal dose coefficients were (0.68  ± 0.24)  Gy/GBq indicating that a population‐based method yields an uncertainty of 35%. Conclusions Dosimetry based on the hybrid planar/SPECT method with OSS outperforms dosimetry based on planar images. The high variability in dose coefficients between the virtual patients demonstrates the need for individualized dosimetry.

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EANM dosimetry committee recommendations for dosimetry of 177Lu-labelled somatostatin-receptor- and PSMA-targeting ligands

Gleisner

Chouin

Gabiña

et al. 2022

Eur J Nucl Med Mol Imaging

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104

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The purpose of the EANM Dosimetry Committee is to provide recommendations and guidance to scientists and clinicians on patient-specific dosimetry. Radiopharmaceuticals labelled with lutetium-177 (177Lu) are increasingly used for therapeutic applications, in particular for the treatment of metastatic neuroendocrine tumours using ligands for somatostatin receptors and prostate adenocarcinoma with small-molecule PSMA-targeting ligands. This paper provides an overview of reported dosimetry data for these therapies and summarises current knowledge about radiation-induced side effects on normal tissues and dose-effect relationships for tumours. Dosimetry methods and data are summarised for kidneys, bone marrow, salivary glands, lacrimal glands, pituitary glands, tumours, and the skin in case of radiopharmaceutical extravasation. Where applicable, taking into account the present status of the field and recent evidence in the literature, guidance is provided. The purpose of these recommendations is to encourage the practice of patient-specific dosimetry in therapy with 177Lu-labelled compounds. The proposed methods should be within the scope of centres offering therapy with 177Lu-labelled ligands for somatostatin receptors or small-molecule PSMA.

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A method for tumor dosimetry based on hybrid planar‐SPECT/CT images and semiautomatic segmentation

Abstract: The hybrid method is found suitable for studies of tumor-absorbed doses in radionuclide therapy, provided that selection criteria regarding the visibility and overlapping activities in the planar images are applied.

Cited by 21 publications

References 43 publications

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

Technical Note: Optimal sampling schedules for kidney dosimetry based on the hybrid planar/SPECT method in ¹⁷⁷Lu‐PSMA therapy

EANM dosimetry committee recommendations for dosimetry of 177Lu-labelled somatostatin-receptor- and PSMA-targeting ligands

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A method for tumor dosimetry based on hybrid planar‐SPECT/CT images and semiautomatic segmentation

Abstract: The hybrid method is found suitable for studies of tumor-absorbed doses in radionuclide therapy, provided that selection criteria regarding the visibility and overlapping activities in the planar images are applied.

Cited by 21 publications

References 43 publications

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

Influence of sampling schedules on [177Lu]Lu-PSMA dosimetry

Technical Note: Optimal sampling schedules for kidney dosimetry based on the hybrid planar/SPECT method in 177Lu‐PSMA therapy

EANM dosimetry committee recommendations for dosimetry of 177Lu-labelled somatostatin-receptor- and PSMA-targeting ligands

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Technical Note: Optimal sampling schedules for kidney dosimetry based on the hybrid planar/SPECT method in ¹⁷⁷Lu‐PSMA therapy