Radiation dose estimation using preclinical imaging with 124I-metaiodobenzylguanidine (MIBG) PET.

Department of Radiology and Biomedical Imaging, UCSF Physics Research Laboratory, University of California, San Francisco, San Francisco, California 94143, USA.
Medical Physics (Impact Factor: 3.01). 09/2010; 37(9):4861-7.
Source: PubMed

ABSTRACT A pretherapy 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)/computed tomography (CT) provides a potential method to estimate radiation dose to normal organs, as well as tumors prior to 131I-MIBG treatment of neuroblastoma or pheochromocytoma. The aim of this work was to estimate human-equivalent internal radiation dose of 124I-MIBG using PET/CT data in a murine xenograft model.
Athymic mice subcutaneously implanted with NB1691 cells that express high levels of human norepinephrine transporter (n = 4) were imaged using small animal microPET/CT over 96 h (approximate imaging time points: 0.5, 2, 24, 52, and 96 h) after intravenous administration of 3.07-4.84 MBq of 124I-MIBG via tail vein. The tumors did not accumulate 124I-MIBG to a detectable level. All four animals were considered as control and organ radiation dosimetry was performed. Volumes of interest were drawn on the coregistered CT images for thyroid, heart, lung, liver, kidney, and bladder, and transferred to PET images to obtain pharmacokinetic data. Based on tabulated organ mass distributions for both mice and adult male human, preclinical pharmacokinetic data were extrapolated to their human-equivalent values. Radiation dose estimations for different age groups were performed using the OLINDA/EXM software with modified tissue weighting factors in the recent International Commission on Radiological Protection (ICRP) Publication 103.
The mean effective dose from 124I-MIBG using weighting factors from ICRP 103 to the adult male was estimated at 0.25 mSv/MBq. In different age groups, effective doses using values from ICRP 103 were estimated as follows: Adult female: 0.34, 15-yr-old: 0.39 mSv/MBq, 10-yr-old: 0.58 mSv/MBq, 5-yr-old: 1.03 mSv/MBq, 1-yr-old: 1.92 mSv/MBq, and newborn: 3.75 mSv/ MBq. For comparison, the reported effective dose equivalent of 124I-NaI for adult male (25% thyroid uptake, MIRD Dose Estimate Report No. 5) was 6.5 mSv/MBq.
The authors estimated human-equivalent internal radiation dose of 124I-MIBG using preclinical imaging data. As a reference, the effective dose estimation showed that 124I-MIBG would deliver less radiation dose than 124I-NaI, a radiotracer already being used in patients with thyroid cancer.


Available from: Youngho Seo, Jun 09, 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: Iodine-131-m-iodobenzylguanidine ([(131)I]mIBG)-targeted radionuclide therapy (TRT) is a standard treatment for recurrent or refractory neuroblastoma with response rates of 30-40 %. The aim of this study is to demonstrate patient-specific dosimetry using quantitative [(124)I]mIBG positron emission tomography/X-ray computed tomography (PET/CT) imaging with a GEometry ANd Tracking 4 (Geant4)-based Monte Carlo method for better treatment planning.
    Molecular imaging and biology: MIB: the official publication of the Academy of Molecular Imaging 08/2014; 17(2). DOI:10.1007/s11307-014-0783-7 · 2.87 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: (124)Iodine ((124)I) with its 4.2 d half-life is particularly attractive for in vivo detection and quantification of longer-term biological and physiological processes; the long half-life of (124)I is especially suited for prolonged time in vivo studies of high molecular weight compounds uptake. Numerous small molecules and larger compounds like proteins and antibodies have been successfully labeled with (124)I. Advances in radionuclide production allow the effective availability of sufficient quantities of (124)I on small biomedical cyclotrons for molecular imaging purposes. Radioiodination chemistry with (124)I relies on well-established radioiodine labeling methods, which consists mainly in nucleophilic and electrophilic substitution reactions. The physical characteristics of (124)I permit taking advantages of the higher PET image quality. The availability of new molecules that may be targeted with (124)I represents one of the more interesting reasons for the attention in nuclear medicine. We aim to discuss all iodine radioisotopes application focusing on (124)I, which seems to be the most promising for its half-life, radiation emissions, and stability, allowing several applications in oncological and nononcological fields.
    BioMed Research International 05/2014; 2014:672094. DOI:10.1155/2014/672094 · 2.71 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Until recently, iodine-124 was not considered to be an attractive isotope for medical applications owing to its complex radioactive decay scheme, which includes several high-energy gamma rays. However, its unique chemical properties, and convenient half-life of 4.2 days indicated it would be only a matter of time for its frequent application to become a reality. The development of new medical imaging techniques, especially improvements in the technology of positron emission tomography (PET), such as the development of new detectors and signal processing electronics, has opened up new prospects for its application. With the increasing use of PET in medical oncology, pharmacokinetics, and drug metabolism, (124)I-labeled radiopharmaceuticals are now becoming one of the most useful tools for PET imaging, and owing to the convenient half-life of I-124, they can be used in PET scanners far away from the radionuclide production site. Thus far, the limited availability of this radionuclide has been an impediment to its wider application in clinical use. For example, sodium [(124)I]-iodide is potentially useful for diagnosis and dosimetry in thyroid disease and [(124)I]-M-iodobenzylguanidine ([(124)I]-MIBG) has enormous potential for use in cardiovascular imaging, diagnosis, and dosimetry of malignant diseases such as neuroblastoma, paraganglioma, pheochromocytoma, and carcinoids. However, despite that potential, both are still not widely used. This is a typical scenario of a rising new star among the new PET tracers.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 04/2014; 90C:138-148. DOI:10.1016/j.apradiso.2014.03.026 · 1.06 Impact Factor