Design and implementation of electron diverters for lobster eye space-based X-ray optics

Micropore optics have recently been implemented in a lobster eye geometry as a compact X-ray telescope. Fields generated by rare-earth magnets are used to reduce the flux of energetic electrons incident upon the focal plane detector in such a setup. We present the design and implementation of the electron diverters for X-ray telescopes of two upcoming missions: the microchannel X-ray telescope onboard the space-based multiband astronomical variable objects monitor and the soft X-ray instrument onboard the solar wind magnetosphere ionosphere link explorer. Electron diverters must be configured to conform to stringent limits on their total magnetic dipole moment and be compensated for any net moment arising from manufacturing errors. The two missions have differing designs, which are presented and evaluated in terms of the fractions of electrons reaching the detector, as determined by relativistic calculations of electron trajectories. The differential flux of electrons to the detector is calculated, and the integrated electron background is determined for both designs.

Synthesis and evaluation of 99mTc-analogues of [123/131I]mIBG prepared via [99mTc][Tc(CO)3(H2O)3]+ synthon for targeting norepinephrine transporter

INTRODUCTION

meta-[^123/131I]Iodobenzylguanidine (mIBG) is a clinical agent used for imaging neuroendocrine tumors, where uptake in tumor is via active transport mechanism through norepinephrine transporters (NET). Our group in past have evaluated a ^99mTc-analogue of the above tracer, based on ^99mTc-4 + 1 labeling approach, which exhibited significant affinity for NET but suffered from reduced specific uptake in comparison to reference standard no-carrier-added (n.c.a.) [¹²⁵I]mIBG. The present work attempts to synthesize two new ^99mTc-analogues of the radio-iodinated derivative following [^99mTc]Tc(CO)₃¹⁺ approach with an aim to improve the above specific uptake content.

METHODS

Two different precursors, xylylenediamine and 1,3-bis(chloromethyl)benzene, were synthetically modified to yield meta-functionalized benzylguanidine derivatives bearing iminodiacetate (IDA) and aminoethylglycine (AEG) tridentate chelating moieties, respectively. These ligands were labeled with technetium-99m via [^99mTc][Tc(CO)₃(H₂O)₃]⁺ synthon to form desired radioactive complexes 9 and 10. The radiolabeling yields of the complexes obtained were >90% as confirmed by radio-HPLC. The HPLC purified complexes were used for in vitro and in vivo evaluation to understand the true biological efficacy. Structural characterization of the radiolabeled complexes was carried after synthesizing and characterizing their Re-analogues.

RESULTS

Cell uptake studies with the radiolabeled complexes in SK-N-SH neuroblastoma cell lines revealed reduced uptake in the cells (<1% of incubated radioactivity/10⁶ cells) in comparison to n.c.a. [¹²⁵I]mIBG (~12%). However, limited specificity (~60%) was observed for the complexes as ascertained through desmethylimipramine (DMI) inhibition. Biodistribution studies in normal Wistar rats exhibited desired non-target clearance pharmacokinetics for the complexes but in vivo NET efficacy in myocardium for the neutral complex 10 could not be established.

CONCLUSIONS

Tridentate [^99mTc]Tc(CO)₃¹⁺ chelation approach severely affects biological behavior of the present small bioactive molecule under study to a significant extent in comparison to monodentate ligation in ^99mTc-4 + 1 strategy.

Synthesis and characterization of a novel 99mTc analogue of *I-mIBG showing affinity for nor-epinephrine transport positive tumors

¹²³I/¹³¹I labeled meta-iodobenzylguanidine (mIBG) is a radiopharmaceutical used for diagnosis of neuroendocrine tumors (NET) related to neural crest origin. Present work evaluates a newly synthesized ^99mTc analogue of this radioiodinated derivative.

Syntheses and biological evaluation of99mTc-HYNIC-fatty acid complexes for myocardial imaging

The aim of the present study is to identify a^99mTc-labeled fatty acid tracer which could be a possible substitute of the widely used¹²³I-labeled fatty acids in studying myocardial metabolism and in detection of myocardial abnormalities.

Multiple intracranial space-occupying lesions in a renal transplant recipient from an area endemic for tuberculosis (TB): TB vs. toxoplasmosis

Renal transplant recipients may present with intracranial space-occupying lesions (SOLs) due to infections as well as a post-transplant lymphoproliferative disorder (PTLD). Here, we discuss a renal transplant recipient who presented with neurologic symptoms and magnetic resonance imaging (MRI) of the brain showed multiple focal SOLs. Tuberculosis (TB), toxoplasmosis, nocardiosis, fungal infections, and PTLD were considered in the differential diagnosis. MRI spectroscopy was suggestive of an infectious cause, such as toxoplasmosis or TB. Serologic tests using Toxoplasma were negative. A brain biopsy followed by immunohistochemical staining using Toxoplasma antibody demonstrated multiple intravascular cysts of toxoplasma. This case highlights the diagnostic dilemma in an immunocompromised patient with multiple focal brain lesions, especially in areas where TB is endemic.

Visualization of suppressed thyroid tissue by technetium-99m-tertiary butyl isonitrile: an alternative to post-TSH stimulation scanning

The autonomously functioning thyroid nodule (AFTN) is a discrete, nodular structure which operates independently of pituitary control and without relation to the remaining thyroid tissue. Presently, for the visualization of a suppressed thyroid lobe, a patient has to undergo the thyrotropin (TSH) stimulation test, which has several disadvantages. In this study we have used tertiary butyl isonitrile (99mTc-TBI), well known as a myocardial imaging agent, for visualization of the suppressed lobe. Thirteen of fourteen patients studied demonstrated a contralateral lobe on a 99mTc-TBI scan which was not visualized with a 99mTc0(4) or 131I scan. Although it is not possible to demonstrate the autonomous nature of the hyperfunctioning thyroid nodule using 99mTc-TBI, we conclude that it is feasible to use this agent to visualize the lobe without the TSH test.

Preparation and evaluation of 99mTc-t-butylisonitrile (99mTc-TBI) for myocardial imaging: a kit for hospital radiopharmacy

A previous method was modified to obtain [99mTc(TBI)6]+ by reacting Zn(TBI)2Br2 directly with 99mTcO4- in the presence of Sn2+ ions. [Cu(TBI)4]Cl was next used as a source of TBI. On reaction with 99mTcO4- and Sn2+ ions for 3 min at 100 degrees C, [99mTc(TBI)6]+ product of radiochemical purity greater than 90% and yield greater than 70% was obtained. Data of biodistribution in rats (2-2.5% in heart) and biokinetics in rabbits were satisfactory. The kit formulation was found to be stable and also safe for administration.