Production of iodine-124 and its applications in nuclear medicine

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, ¹²⁴I-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 [¹²⁴I]-iodide is potentially useful for diagnosis and dosimetry in thyroid disease and [¹²⁴I]-M-iodobenzylguanidine ([¹²⁴I]-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.     

Radiolabeling approaches of nanoparticles with 99mTc

Nanomedicine applications have recently gathered great attention in terms of their revolutionary properties and multivalency. Nanoparticles (NPs) have proven useful owing to their size, surface and kinetics advantages, as well as their ability to be functionalized with targeting, imaging and therapeutic moieties. Nuclear medicine is actively involved in nano‐research innovative breakthrough efforts in multiple applications, through the radiolabeling of NP structures. There are several ways that NP‐radiolabeling can be approached depending on the radionuclide that is used and the NP type. The radiolabeling of NPs with the most widely and easily available radiometal, which is ^99mTc, is the focus of this review. Copyright © 2013 John Wiley & Sons, Ltd.     

Radiolabeling of Intact Dosage Forms by Neutron Activation: Effects on In Vitro Performance

Compressed tablets containing various quantities of stable isotopes of Ba, Er, and Sm for use in neutron activation studies were evaluated for the effect of stable isotope incorporation on tablet hardness and disintegration times. At concentrations likely to be used in scintigraphic studies employing neutron activation as a radiolabeling method, no significant effect on in vitro parameters were observed. While the incorporation of stable isotopes influenced tablet hardness to a greater degree than disintegration time, irradiation of tablets in a neutron flux of 4.4× 10¹³ n/cm² sec had a direct effect on tablet disintegration time. Thus, future neutron activation studies should focus on minimizing the amount of stable isotope to be incorporated with the formulation while using the shortest feasable irradiation time.     

Preclinical evaluation of holmium‐166 labeled anti‐VEGF‐A(Bevacizumab)

Radiolabeled antiangiogenic monoclonal antibodies are potential agents for targeted therapy in specific types of malignancies. In this study, ¹⁶⁶Ho‐DOTA‐Bevacizumab was used in biodistribution studies using single‐photon emission computed tomography (SPECT) to acquire dosimetric aspects of the radiolabeled antibody in mice. The liver toxicity of the radiolabeled antibody was also determined using serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase and alkaline phosphatase assay 2–7 days post‐injection. The SPECT biodistribution demonstrated a similar pattern as the other radiolabeled anti‐ vascular endothelial growth factor A (VEGF‐A) immunoconjugates.¹⁶⁶Ho‐DOTA‐Bevacizumab was revealed as a potential compound for therapy/imaging of VEGF‐A expression in oncology. Copyright © 2013 John Wiley & Sons, Ltd.     

Establishment of a fast and high yield method for routine production of [131I]MIBG and investigation of its radiochemical stability for diagnosis and treatment uses

In this work, exchange radioiodination of metaiodobenzylguanidine (MIBG) was carried out at optimum conditions that facilitates the production of [¹³¹I]MIBG both quickly and efficiently. The radiochemical purity and yield of the labeled product are typically as high as 99% and 90% for diagnostic dose and 95% and 80% for therapeutic dose, respectively. Stability studies show that labeled material at the room temperature met the demand of the clinical application. This labeling procedure will be used in the routine production process of [¹³¹I]MIBG for diagnosis and treatment uses.     

肿瘤受体显像

肿瘤受体显像研究包括放射性标记配体的制备、配体与受体的体外分析及体内受体显像,肿瘤受体配体可用18F、123I(或131I)、111In与99Tcm标记,通过放射性受体结合分析、放射性自显影与受体特性分析,对其体外性能进行研究。神经多肽受体显像、类固醇受体显像与σ受体显像等已应用于多种肿瘤的诊断、分期、治疗方案选择与预后评价,其中神经多肽受体显像得到了较广泛的研究与应用。     

Peptide-based radiopharmaceuticals: future tools for diagnostic imaging of cancers and other diseases

Small synthetic receptor-binding peptides are the agents of choice for diagnostic imaging and radiotherapy of cancers due to their favorable pharmacokinetics. Molecular modification techniques permit the synthesis of a variety of bioactive peptides with chelating groups, without compromising biological properties. Various techniques have been developed that allow efficient and site-specific labeling of peptides with clinically useful radionuclides such as (99m)Tc, (123)I, (111)In, and (18)F. Among them, (99m)Tc is the radionuclide of choice because of its excellent chemical and imaging characteristics. Recently, many (99m)Tc-labeled peptides have proven to be useful imaging agents. Beside (99m)Tc-labeled peptides, several peptides radiolabeled with (111)In and (123)I have been prepared and characterized. In addition, (18)F-labeled peptides hold clinical potential due to their ability to quantitatively detect and characterize a variety of human diseases using positron-emission tomography. The availability of this wide range of peptides labeled with different radionuclides offers multiple diagnostic and therapeutic applications. Various receptors are over-expressed in particular tumor types and peptides binding to these receptors can be used to visualize tumor lesions scintigraphically. Thus, radiolabeled peptides have potential use as carriers for the delivery of radionuclides to tumors, infarcts, and infected tissues for diagnostic imaging and radiotherapy. Many radiolabeled peptides are currently under investigation to determine their potential as imaging agents. These peptides are designed mainly for thrombus, tumor, and infection/inflammation imaging. This article presents recent developments in small synthetic peptides for imaging of thrombosis, tumors, and infection/inflammation.     

单链尿激酶型纤溶酶原激活剂在兔及猕猴中的生物转化和药代动力学

目的:研究重组单链尿激酶型纤溶酶原激活剂(rhscuPA)单链和代谢物双链(tcuPA)的药代动力学和转化。方法:125I标记结合生化反应及RPHPLC测定血浆125IscuPA和125ItcuPA浓度;平板溶圈法测定血浆溶纤组分浓度。结果:兔iv125IscuPA后单链呈双指数消除,T1/2α和T1/2β分别为7和43min,双链呈单指数消除T1/2=9min,约有38%单链转化为双链。猕猴静脉推注不同剂量rhscuPA后血浆纤溶组分浓度呈单指数下降,T1/2分别为(63±18)min,(115±21)min和(123±29)min,CLS随剂量变慢。推注ntcuPAT1/2=(137±27)min。结论:兔iv125IscuPA后可检测到125IrhscuPA与125ItcuPA。猕猴ivrhscuPA后血浆溶纤组分浓度呈非线性变化。