Automatic bone marrow segmentation for precise [177Lu]Lu‐PSMA‐617 dosimetry

• Published in: Medical physics (Lancaster) Vol. 52; no. 6; pp. 3970 - 3980
• Main Authors: Lu, Zhonglin, Hu, Jiaxi, Chen, Gefei, Jiang, Han, Shih, Cheng‐Ting, Afshar‐Oromieh, Ali, Rominger, Axel, Shi, Kuangyu, Mok, Greta S. P.
• Format: Journal Article
• Language: English
• Published: United States 01.06.2025
• Subjects: [177Lu]Lu‐PSMA‐617; Automation; bone marrow; Bone Marrow - diagnostic imaging; Bone Marrow - radiation effects; Dipeptides - therapeutic use; dosimetry; Heterocyclic Compounds, 1-Ring - therapeutic use; Humans; Image Processing, Computer-Assisted - methods; Lutetium - therapeutic use; Male; Radioisotopes; Radiometry; segmentation; Single Photon Emission Computed Tomography Computed Tomography; SPECT/CT; segmentation; dosimetry; [177Lu]Lu‐PSMA‐617; SPECT/CT; bone marrow
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1002/mp.17684

Background Bone marrow (BM) is the dominant dose‐limiting organ in [177Lu]Lu‐PSMA‐617 therapy for patients with metastasized castration resistant prostate cancer, where BM dosimetry is challenging due to segmentation. Purpose We aim to develop an automatic image‐based segmentation method on peri‐therapeutic sequential [177Lu]Lu‐PSMA‐617 images for personalized BM dosimetry. Methods Quantitative SPECT/CT imaging at 2, 20, 40 and 60 (n = 14)/200 (n = 16) h post [177Lu]Lu‐PSMA‐617 injection were analyzed for 10 patients with 30 treatment cycles. X‐means clustering was applied on the deep learning‐based segmented lumbar spines CT images to classify the BM region. A single threshold method, two empirical segmentation methods (one sphere and five spheres), and gold standard manual segmentation were also implemented. The Dice similarity coefficient between BM masks of the X‐means clustering and single threshold method was calculated as compared to the gold standard. BM mean absorbed dose (Dmean) was obtained for different segmentation methods. Absolute errors and Bland–Altman analysis were also evaluated for BM Dmean derived from evaluated segmentation methods compared with the gold standard. Wilcoxon signed‐rank test was performed for statistical evaluation. BM Dmean was correlated with the change of platelets and white blood cells (WBC) pre‐ and post‐treatment using Pearson correlation analysis. Results In 30 cycles of 10 patients, the average Dice is 0.76 ± 0.18 for the X‐means clustering method, as compared to 0.61 ± 0.19 for the single threshold method. The gold standard yields mean BM Dmean of 0.46 ± 0.69 Gy. The X‐means clustering method exhibits significantly (p < 0.01) lower mean absolute BM Dmean (25.34 ± 64.48%) errors, followed by the single threshold (32.46 ± 69.49%), one sphere (50.53 ± 35.40%), and five spheres (72.73 ± 115.97%) methods. Bland–Altman analysis reveals that the X‐means clustering method has a smaller Dmean difference (0.0330 Gy) compared to the single threshold (0.0512 Gy), one sphere (−0.1903 Gy), and five spheres (0.2108 Gy) methods. Stronger correlations (r ≤ −0.65) are found between platelets/WBC changes and BM Dmean from both the gold standard and X‐means clustering methods than other methods. Conclusions X‐means clustering is feasible to segment the BM based on the CT images of peri‐therapy SPECT/CT and shows advantages compared with the single threshold and empirical sphere segmentation methods.