Dosimetry of bone metastases in targeted radionuclide therapy with alpha-emitting Ra-dichloride.
Purpose: Ra-dichloride is an alpha-emitting radiopharmaceutical used in the treatment of bone metastases from castration-resistant prostate cancer. Image-based dosimetric studies remain challenging because the emitted photons are few. The aim of this study was to implement a methodology for in-vivo...
| Published in: | European Journal of Nuclear Medicine & Molecular Imaging Vol. 43; no. 1; pp. 21 - 34 |
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| Main Authors: | , , , , , , , , , , , , |
| Format: | Journal Article |
| Published: |
Springer Nature
Jan2016
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| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=ccm&AN=111657746&site=ehost-live header: @attributes: shortDbName: ccm uiTerm: 111657746 longDbName: CINAHL Complete uiTag: AN controlInfo: bkinfo: dissinfo: jinfo: jid: 16197070 NPC jtl: European Journal of Nuclear Medicine & Molecular Imaging issn: 16197070 maglogo: N pubinfo: dt: Jan2016 vid: 43 iid: 1 pid: 237 pub: Springer Nature place: New York, New York artinfo: ui: 111657746 10.1007/s00259-015-3150-2 111657746 ppf: 21 ppct: 13 formats: fmt: @attributes: type: P tig: atl: Dosimetry of bone metastases in targeted radionuclide therapy with alpha-emitting Ra-dichloride. aug: au: Pacilio, Massimiliano Ventroni, Guido De Vincentis, Giuseppe Cassano, Bartolomeo Pellegrini, Rosanna Di Castro, Elisabetta Frantellizzi, Viviana Follacchio, Giulia Garkavaya, Tatiana Lorenzon, Leda Ialongo, Pasquale Pani, Roberto Mango, Lucio affil: Department of Medical Physics, Azienda Ospedaliera San Camillo Forlanini, Circonvallazione Gianicolense no. 87 00152 Rome Italy sug: ab: Purpose: Ra-dichloride is an alpha-emitting radiopharmaceutical used in the treatment of bone metastases from castration-resistant prostate cancer. Image-based dosimetric studies remain challenging because the emitted photons are few. The aim of this study was to implement a methodology for in-vivo quantitative planar imaging, and to assess the absorbed dose to lesions using the MIRD approach. Methods: The study included nine Caucasian patients with 24 lesions (6 humeral head lesions, 4 iliac wing lesions, 2 scapular lesions, 5 trochanter lesions, 3 vertebral lesions, 3 glenoid lesions, 1 coxofemoral lesion). The treatment consisted of six injections (one every 4 weeks) of 50 kBq per kg body weight. Gamma-camera calibrations for Ra included measurements of sensitivity and transmission curves. Patients were statically imaged for 30 min, using an MEGP collimator, double-peak acquisition, and filtering to improve the image quality. Lesions were delineated on Tc-MDP whole-body images, and the ROIs superimposed on the Ra images after image coregistration. The activity was quantified with background, attenuation, and scatter correction. Absorbed doses were assessed deriving the S values from the S factors for soft-tissue spheres of OLINDA/EXM, evaluating the lesion volumes by delineation on the CT images. Results: In 12 lesions with a wash-in phase the biokinetics were assumed to be biexponential, and to be monoexponential in the remainder. The optimal timing for serial acquisitions was between 1 and 5 h, between 18 and 24 h, between 48 and 60 h, and between 7 and 15 days. The error in cumulated activity neglecting the wash-in phase was between 2 % and 12 %. The mean effective half-life ( T) of Ra was 8.2 days (range 5.5-11.4 days). The absorbed dose ( D) after the first injection was 0.7 Gy (range 0.2-1.9 Gy. Considering the relative biological effectiveness (RBE) of alpha particles (RBE = 5), D = 899 mGy/MBq (range 340-2,450 mGy/MBq). The percent uptake of Tc and Ra (activity extrapolated to t = 0) were significantly correlated. Conclusion: The feasibility of in vivo quantitative imaging in Ra therapy was confirmed. The lesion uptake of Ra-dichloride was significantly correlated with that of Tc-MDP. The D to lesions per unit administered activity was much higher than that of other bone-seeking radiopharmaceuticals, but considering a standard administration of 21 MBq (six injections of 50 kBq/kg to a 70-kg patient), the mean cumulative value of D was about 19 Gy, and was therefore in the range of those of other radiopharmaceuticals. The macrodosimetry of bone metastases in treatments with Ra-dichloride is feasible, but more work is needed to demonstrate its helpfulness in predicting clinical outcomes. pubtype: Academic Journal doctype: Journal Article ougenre: Article language: English refInfo: holdings: @attributes: islocal: N |
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