99mTc‐tazobactam,a novel infection imaging agent: Radiosynthesis,quality control,biodistribution, and infection imaging studies

The radiolabeled drug ^99mTc‐tazobactam (^99mTc‐TZB) was developed and assessed as an infection imaging agent in Pseudomonas  aeruginosa and Salmonella  enterica infection–induced animal models by comparing with inflammation induced animal models. Radiosynthesis of ^99mTc‐TZB was assessed while changing ligand concentration, reducing agent concentration, pH, and reaction time while keeping radioactivity constant (~370 MBq). Percent labeling of the resulting complex was measured using paper chromatography and instant thin layer chromatography. The analysis of the ^99mTc‐TZB complex indicated >95% labeling yield and electrophoresis revealed complex is neutral in nature. The biodistribution study also showed predominantly renal excretion; however liver, stomach, and intestine also showed slight tracer agent uptake. The agent significantly accumulated in Pseudomonas aeruginosa and Salmonella enterica infection induced tissues 3.58 ± 0.26% and 2.43 ± 0.42% respectively at 1 hour postinjection. The inflamed tissue failed to uptake noticeable activity at 1 hour time point. The scintigraphic study results were found in accordance with biodistribution pattern. On the basis of our preliminary results, the newly developed ^99mTc‐TZB can be used to diagnose bacterial infection and to discriminate between infected and inflamed tissues.     

Synthesis and pharmacological evaluation of 99mTc‐labeled imidazolyl‐containing diphosphonic acid as a novel bone imaging agent

In order to develop a superior bone imaging agent, a new radiotracer ^99mTc‐1‐hydroxy‐5‐(2‐butyl‐1H‐imidazol‐1‐yl)pentane‐1,1‐diyldiphosphonic acid (BIPeDP) was designed and prepared with good radiochemical yield and stability. The biodistribution in mice shows that ^99mTc‐BIPeDP has high specificity in the skeleton with the maximum uptake of 17.30 ± 0.14 injected dose per gram at 60 min. Kinetics of blood clearance shows that the distribution half‐life (T_1/2α) and elimination half‐life (T_1/2β) of ^99mTc‐BIPeDP are 3.7 and 49.7 min, respectively. An excellent image can be obtained at 1‐h post‐injection with the single photon emission computed tomography bone scanning, which is clearer and quicker than ^99mTc‐zoledronic acid, ^99mTc‐1‐hydroxy‐5‐(1H‐imidazol‐1‐yl)pentane‐1,1‐diyldiphosphonic acid, and ^99mTc‐methylenediphosphonic acid All results indicate that ^99mTc‐BIPeDP holds great potential as a novel promising bone imaging agent. Copyright © 2013 John Wiley & Sons, Ltd.     

99mTc‐HYNIC‐(Ser)3‐J18 peptide: A radiotracer for non‐small‐cell lung cancer targeting

Radiolabeled peptide could be a useful tool for the diagnosis of non‐small‐cell lung cancer (NSCLC). In this study, HYNIC‐(Ser)₃‐J18 peptide was labeled with ^99mTc using EDDA/tricine as coligands. The in vitro and in vivo studies of this radiolabeled peptide were performed for cellular‐specific binding and tumor targeting in A‐549 cells and tumor‐bearing mice, respectively. The high radiochemical purity was obtained and this radiolabeled peptide exhibited high stability in buffer and serum. The radiolabeled peptide showed high affinity for the A‐549 cells with a dissociation constant value (K_D) of 4.4 ± 0.8 nm . The tumor–muscles ratios were 2.7 and 4.4 at 1 and 2 hr after injection of ^99mTc‐(EDDA/tricine)‐HYNIC‐(Ser)₃‐J18 in tumor‐bearing mice. The tumor uptake was decreased after preinjection with non‐labeled peptide for this radiolabeled peptide in blocking experiment. The results of this study showed the ^99mTc‐(EDDA/tricine)‐(Ser)₃‐HYNIC‐J18 peptide might be a promising radiolabeled peptide for NSCLC targeting.     

99mTc‐aprotinin – optimisation and validation of radiolabelling kits for routine preparation for diagnostic imaging of amyloidosis

Technetium‐99m aprotinin was prepared from an optimised radiolabelling kit formulation containing aprotinin, alkaline buffer and stannous chloride (reducing agent) and radiolabelled using ^99mTc‐pertechnetate. The labelling was achieved within 25 min, with radiochemical purities of >98%.     

Synthesis,characterization and pre‐clinical evaluation of 99mTc‐tricarbonyl complexes as potential myocardial perfusion imaging agents

Myocardial perfusion imaging is an established Nuclear Medicine investigation. Current myocardial perfusion imaging agents sestamibi and tetrofosmin have number of drawbacks; low heart uptake coupled with uptake into the surrounding tissues leads to a poorer image quality. There is a need for continued research into designing and evaluating potentially superior myocardial imaging agents. Tri‐carbonyl‐technetium and rhenium complexes were prepared by combination with mono‐dentate and bi‐dentate ligands. Complexes were characterized by HPLC, MAS, nuclear magnetic resonance, infrared, single‐crystal X‐ray diffraction and partition coefficient determinations. ^99mTc(CO)₃ complexes were administered intravenously to Sprague Dawley rats, and tissue distribution studies were carried out at 15 min and 1 h p.i. Radiochemical purity was assessed as >90%. 1‐10‐phenanthroline, 2,2′‐bipyridine and imidazole complexes gave the highest heart uptake. The percentage injected dose per gram (n = 3) at 1 h for 1‐10‐phenanthroline/imidazole was blood 0.21 ± 0.01, heart 1.12 ± 0.11, kidney 3.61 ± 1.13, liver 0.62 ± 0.06, lung 0.28 ± 0.12, spleen 0.24 ± 0.05, small intestine contents 1.87 ± 0.92; and for 2,2′‐bipyridine /imidazole was blood 0.23 ± 0.02, heart 1.07 ± 0.18, kidney 3.31 ± 1.28, liver 0.56 ± 0.09, lung 0.14 ± 0.02, spleen 0.2 ± 0.1, small intestine content 1.05 ± 0.48. Further investigation to evaluate more complexes based on 1,10‐phenanthroline, 2,2′‐bipyridine and imidazole derivatives could potentially lead to agents with an increased heart uptake and faster clearance from the liver and gastrointestinal tract.     

Synthesis of 99mTc‐labeled organo‐germanium nanoparticles and their in vivo study as a spleen imaging agent

^99mTc‐Labeled organo‐germanium nanoparticles ranging in size from 60 to 80 nm were newly developed for a spleen imaging agent. The radiolabeled nanoparticles were prepared with a high labeling efficiency (over 99%) and they also showed an excellent stability at room temperature for 6 h. The biodistribution data of the nanoparticles injected into rats via intravenous routes showed a notably higher accumulation in the spleen when compared to other reticuloendothelial system organs. Gamma image of the rabbits obtained after an intravenous injection of the nanoparticles revealed a localization of the radioactivity mainly in the spleen and the liver. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and evaluation of a 99mTc‐labeled tubulin‐binding agent for tumor imaging

Cholchicine and its derivatives are very potent tubulin‐binding compounds and can be used as a potential tumor targeting agents. In this study, colchicine was labeled with ^99mTc via hydrazinonicotinic acid (HYNIC) and was investigated further. HYNIC/cholchicine was synthesized and labeling with ^99mTc was performed at 95 °C for 15 min and radiochemical analysis included HPLC method. The stability of radiconjugate was checked in the presence of human serum at 37 °C up to 24 h. Biodistribution was studied in breast tumor‐bearing mice. Labeling yield of 95.8 ± 0.54% was obtained corresponding to a specific activity of 54 MBq/µmol. Radioconjugate showed good stability in the presence of human serum. Biodistribution studies in tumor‐bearing mice showed that ^99mTc/HYNIC/colchicine conjugate accumulated in tumor with good uptake (3.17 ± 0.14% g/g at 1 h post‐injection). The radioconjugate was cleared fast from normal organs and showed clearance through urinary and hepatobiliary systems with accumulation of activity in kidneys and intestine. This radioconjugate may be useful to assess the presence of tumor by imaging.     

Synthesis and biodistribution of novel 99mTc‐nitrido methylpiperidine dithioformate derivatives as potential brain imaging agents

Three dithioformate ligands with methyl substituted on the piperidine rings, potassium 1‐(2‐methylpiperidine‐1‐yl)‐dithioformate (2‐mp), potassium 1‐(3‐methylpiperidine‐1‐yl)‐dithioformate (3‐mp) and potassium 1‐(4‐methylpiperidine‐1‐yl)‐dithioformate (4‐mp) were synthesized. The corresponding ^99mTc‐nitrido complexes were prepared in high yield (>95%) through the [^99mTcN] intermediate and characterized by thin layer chromatography and high‐performance liquid chromatography. All the neutral ^99mTc‐nitrido complexes were stable under physiological conditions and lipophilic with log P values between 1.40 and 1.58. In vivo biodistribution results showed that all the ^99mTc‐nitrido complexes displayed high brain uptakes and long retention times. Among them, ^99mTcN‐4mp, demonstrated the best properties for brain imaging with the brain uptake 3.40±0.24, 3.22±0.31, 2.72±0.28 and 2.22±0.18% ID/g at 5, 30, 60 and 120 min p.i., respectively. Moreover, the influence of stereochemistry of the ^99mTcN complexes with methyl substitution on ortho, meta and para positions on piperidine ring on the biodistribution properties were investigated with B3LYP/6‐31G*(LANL2DZ for Tc) method using the Gaussian 03 program package. Copyright © 2009 John Wiley & Sons, Ltd.     

Labeling and evaluation of 99mTc‐tricarbonyl‐meloxicam as a preferential COX‐2 inhibitor for inflammation imaging

Imaging of inflammation has an important role in dissolving problems in diagnosis and therapy of patients with inflammatory disorders. In this study meloxican as a nonsteroidal anti‐inflammatory drug (NSAID) has been labeled with thechnetium‐99m‐tricarbonyl core ([^99mTc (CO)₃ (H₂O)₃]⁺) in order to evaluate its feasibility as an inflammation imaging agent for in vivo use. ^99mTc‐tricabonyl labeling of meloxicam was performed by its incubation with prepared precursor ^99mTc‐tricabonyl and heating in a boiling water bath for 30 min while various range of pH (1–9) was adjusted. The stability of ^99mTc‐tricarbonyl‐Meloxicam was checked in human serum at 37 °C, and biodistribution was studied in mice. Labeling yield of 98.1 ± 0.4% was obtained corresponding to a specific activity of 0.14 GBq/µmol. The radioconjugate showed good stability in human serum. Our main achievement was high accumulation of ^99mTc‐tricarbonyl‐Meloxicam in the inflammated muscle in mice (T/NT = 3.90 at 4 h post injection) which may diagnostically be beneficial for distinguish sites of inflammation.     

Evaluation of a 99mTc‐labelled meso‐bisphenylporphyrin as a tumour image agent

Porphyrins are excellent agents for photodynamic treatment of various types of cancer and also good metal chelators that form highly stable metallo‐complexes with different radionuclides. Therefore, radiolabelled porphyrins could also be potentially used as tumour imaging agents. In this context, the aim of this work was the radiolabelling of meso‐bis[3,4‐bis(carboxymethyleneoxy)phenyl]porphyrin, 2CPP, with Technetium‐99 m (^99mTc) and the evaluation of its radiochemical and biological properties in vitro and in vivo. The labelling procedure was optimized resulting in an efficiency of 92.52 ± 0.48%. The complex ^99mTC‐2CPP remained stable for more than 4 h. The biodistribution showed that ^99mTc‐2CPP is eliminated by gastrointestinal and urinary pathways. The tumour/muscle ratio increases over time, being 3.33 ± 1.22 and 3.55 ± 1.29 in WiDr‐bearing tumours mice and in H1299‐bearing tumours mice, respectively, 6 h post‐injection, showing the tumour specificity of the ^99mTc‐2CPP complex. The favourable tumour/muscle ratio of ^99mTc‐2CPP shows that this complex could potentially be used as tumour imaging agent. Moreover, it could be used to follow the progression or regression of tumours before, during and after the radiotherapy, chemotherapy and photodynamic therapy. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of 99mTc‐labelled biologically active molecules using borohydride exchange resin as a reducing agent for the preparation of radiopharmaceuticals

A novel and efficient method for preparing ^99mTc‐complexes of radiopharmaceuticals has been developed by reacting [^99mTc]pertechnetate with a ligand in the presence of borohydride exchange resin (BER) as a reducing agent. The latter is stable over a wide range of pH (2–11) and thus can be used with biologically active compounds without the formation of insoluble ^99mTcO₂ or SnO₂ colloids. Since the radiolabelled complexes are produced with high radiochemical purity and labelling efficiency under milder conditions than those required for the conventional reducing agents, the latter can be replaced. The method is expected to be applicable to the preparation of ^99mTc‐radiopharmaceuticals. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis of 99mTc(CO)3‐mebrofenin via [99mTc(OH2)3(CO)3]+ precursor and comparative pharmacokinetics studies with 99mTc‐mebrofenin

The organometallic precursor fac‐[^99mTc(OH₂)₃(CO)₃]⁺ was reacted with trimethyl‐bromoacetanilido‐iminodiacetic acid (mebrofenin) in phosphate buffered saline (pH 7) at 70°C for 1 h to produce the complex, ^99mTc(CO)₃‐mebrofenin, in >95% yields. High performance liquid chromatography analysis indicated the formation of a single species. In vitro studies of ^99mTc(CO)₃‐mebrofenin showed that the complex is stable for 24 h. No decomposition or alteration of the complex was observed in the presence of excess amount of cysteine and histidine. ^99mTc‐mebrofenin was also prepared for comparative evaluation by the conventional method using a ready to use kit HPLC analysis of this complex showed presence of two species. Biodistribution studies in normal Swiss mice with ^99mTc(CO)₃‐mebrofenin showed hepatobiliary clearance. However, the retention in liver was higher (13% at 1 h p.i.) as compared to that of ^99mTc‐mebrofenin (3.4% at 1 h p.i.). Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and preliminary biological evaluation of a 99mTc‐labeled hypericin derivative as a necrosis avid imaging agent

Mono‐[¹²³I]iodohypericin and mono‐[¹²³I]iodohypericin monocarboxylic acid are iodine‐123‐labeled hypericin derivatives which have shown great promise in preclinical studies as necrosis avid imaging agents in animal models of infarction. In view of the more attractive properties of a ^99mTc‐labeled hypericin derivative, we have synthesized a conjugate of protohypericin monocarboxylic acid with S‐benzoylmercaptoacetyldiglycyl‐diaminopentane in an overall yield of 15%. The conjugate was labeled with technetium‐99m by exchange labeling at pH 10 in a labeling yield of 95% followed by photocyclization to yield ^99mTc‐mercaptoacetyldiglycyl‐1,5‐diaminopentylene hypericincarboxamide (^99mTc‐13). The negatively charged ^99mTc‐13 complex was purified by reversed phase high‐pressure liquid chromatography and the log P_7.4 was determined to be 2.36. In normal NMRI mice, the complex showed slow hepatobiliary clearance while plasma clearance was rapid. The tracer was evaluated in rats with reperfused hepatic infarction by ex vivo autoradiography, gamma counting and histochemical techniques. Unlike the radioiodinated hypericin derivatives, the new tracer agent did not show preferential uptake in necrotic tissue on autoradiography and gamma counting techniques. Conjugation of hypericin with a ^99mTc‐chelate, resulting in a change in size, charge and lipophilicity, had a profound effect on the necrosis avidity of the tracer agent. The results show that ^99mTc‐13 is not suitable for imaging necrosis. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and radiobiological evaluation of a new 99mTc‐labeled small peptide: 99mTc‐YGGSLAK as imaging agent

Peptides are known as receptor‐specific molecules that play an important role not only in diagnosis and therapy of neoplastic diseases, but also in the pathogenesis of other diseases. In an effort to develop a peptide‐based radiopharmaceutical for scintigraphic studies, a small peptide Tyr‐Gly‐Gly‐Ser‐Leu‐Ala‐Lys (YGGSLAK) was synthesized by Fmoc solid‐phase peptide synthesis using an automated synthesizer. This peptide was analyzed by TLC, HPLC and mass spectroscopy. Then, we investigated its analytical and pharmacokinetic study after radiolabeling with technetium‐99 m (^99mTc) using SnCl₂. The radiochemical purity of the complex was over 95% and log p value was 1.46. In vivo biodistribution studies in rat showed that most activity of this injected radiolabeled peptide (^99mTc‐YGGSLAK) was accumulated in the liver and followed by gallbladder, intestines and kidney. Scintigraphy studies on rabbits also showed very high uptake and retention in the liver and gallbladder, and after 1 h slowly excreted through the hepatobiliary system and a little amount was also excreted through the renal system. The radiochemical and in vitro and in vivo characterization indicates that ^99mTc‐YGGSLAK has certain favorable properties and it might be used as a new radiopharmaceutical for hepatobiliary scintigraphy. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,characterization and biodistribution of 99mTc(CO)3–ABP and comparison with 99mTc–ABP

The (l‐hydroxy‐4‐amino‐butylidene‐l,l‐bisphosphate) (ABP) is a compound that inhibits bone resorption, and a highly effective drug in the treatment of metastatic bone disease. The fac‐[^99mTc(CO)₃(H₂O)₃]⁺ precursor was reacted with ABP in saline (pH=3–4) at 45°C for 15 min to produce the ^99mTc(CO)₃–ABP complex. The radiochemical purity (RCP) of the product was over 90% as measured by thin layer chromatography and high‐performance liquid chromatography. No decomposition of the complex at room temperature (25°C) was observed over a period of 6 h. Its partition coefficient indicated that it was a weak hydrophilic complex. The biodistribution in normal mice of ^99mTc(CO)₃–ABP complex differed greatly from that of ^99mTc–ABP, and the former had a lower bone uptake as compared with that of the latter. The experiment results showed that the incorporation of the [^99mTc(CO)₃]⁺ core into the ABP ligand may drastically change the characterization and biological features as compared with ^99mTc–ABP. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis,radio‐LC‐MS analysis and biological evaluation of 99mTc‐techmazenil

A ^99mTc‐labelled compound with the biological characteristics of flumazenil would be useful for determination of neuronal viability after the onset of a stroke. Therefore, we have derivatized Ro‐15‐3890 (a flumazenil metabolite bearing a carboxylic acid group instead of an ethyl ester) by coupling it with a bisamino bisthiol tetraligand bearing a 3‐hydroxypropyl side chain (3‐hydroxypropyl‐BAT) to enable labelling with technetium‐99m. After purification by RP‐HPLC, the ligand was deprotected and labelled in a ‘one pot’ reaction, yielding a ^99mTc‐BAT‐propylester of Ro‐15‐3890 (^99mTc‐techmazenil). Radio‐LC‐MS analysis of the isolated main peak showed the molecular ion mass (608.0618) of the expected ^99mTc‐techmazenil. The biodistribution of ^99mTc‐techmazenil was investigated in normal mice and indicated that the tracer is cleared from plasma mainly by the hepatobiliary system and shows a very low uptake in brain. In vitro binding studies on mice brain slices indicated that techmazenil does not bind to benzodiazepine receptors. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and biological evaluation of a novel asymmetrical 99mTc‐nitrido complex of metronidazole derivative

The novel dithiocarbamate derivative of metronidazole, potassium 2‐(2‐methyl‐5‐nitro‐1H‐imidazolyl)‐ethyl‐dithiocarbamate (MNIE‐DTC), was synthesized as the pharmacophore‐containing bifunctional ligand. The corresponding asymmetrical ^99mTc‐nitrido complex, expected as a tumor hypoxia marker, had been successfully obtained by the addition of the biphosphine ligand PNP5 (PNP5 = N‐ethoxethyl‐N,N‐bis[2‐(bis(3‐methoxypropyl)phosphino)ethyl]‐amine) and the dithiocarbamate ligand (MNIE‐DTC) to the ^99mTc‐nitrido precursor solution at 100°C for 15 min. The radiochemical purity of the product was above 95% as measured by thin‐layer chromatography and high‐performance liquid chromatography. In vitro studies showed that the complex possessed good stability under physiological conditions. Its partition coefficient studies indicated that it was a lipophilic complex. The electrophoresis results showed that the complex was cationic. Biological evaluation of the complex [^99mTcN(PNP5)(MNIE‐DTC)]⁺ performed in Kunming mice bearing H22 tumor showed that the complex had a moderate tumor uptake (0.57±0.06%ID/g at 1h), and the ratios of tumor/blood and tumor/muscle were 2.46 and 1.31 at 1h p.i., and reached 4.52 and 2.86 at 4h p.i., respectively. Copyright © 2007 John Wiley & Sons, Ltd.     

99mTc‐tricabonyl labeling of ofloxacin and its biological evaluation in Staphylococcus aureus as an infection imaging agent

Even in recent decades, one of the major causes of death and unhealthiness in the whole world is infection and inflammation. The use of radiopharmaceuticals is a powerful tool in managing the patients with infectious diseases. In this study, ofloxacin as a second‐generation fluoroquinolone has been labeled with [^99mTc(CO)₃(H₂O)₃]⁺ core to formulate a suitable infection imaging agent. Ofloxacin was radiolabeled with ^99mTc using carbonyl core. Radioligand chemical analysis involved HPLC methods. Radioconjugate stability and lipophilicity were determined. Binding with Staphylococcus aureus and biodistribution in infected mice for labeled compound were studied. The radioligand was characterized by HPLC, and its radiochemical purity was more than 90%. In vitro stability studies have shown the complex was stable at least 6 h after labeling at room temperature. The n‐octanol/water partition coefficient experiment exhibited logP = 1.52 ± 0.21 for ^99mTc(CO)₃‐ofloxacin. The complex showed specific binding to S. aureus. Biodistribution results showed that radioligand had high accumulation in the infected muscle in a mice (T/NT = 2.02 ± 0.12 at 4 h postinjection). On the basis of stability and infection site uptake ratio, suitability of this complex as a radiotracer for imaging of infections is recognized.     

Synthesis, 99mTc‐labeling,and preliminary biological evaluation of DTPA‐melphalan conjugates

Melphalan (MFL) is a typical nitrogen mustard for the treatment of many types of cancer. For the purpose to develop novel ^99mTc‐labeled tumor imaging agents with SPECT, MFL was directly labeled by ^99mTc using diethylene triamine pentacetate acid (DTPA) as bifunctional chelating agent. The novel ligands were successfully synthesized by conjugation of DTPA to MFL to get monosubstituted DTPA‐MFL and bis‐substituted DTPA‐2MFL. Radiolabeling was performed in high yield to get ^99mTc‐DTPA‐MFL and ^99mTc‐DTPA‐2MFL, respectively, which were hydrophilic and stable at room temperature. The high initial tumor uptake with retention, good tumor/muscle ratios, and satisfactory scintigraphic images suggested the potential of ^99mTc‐DTPA‐MFL and ^99mTc‐DTPA‐2MFL for tumor imaging. However, the slow normal tissue clearance would be a great obstacle. Further modification on the linker and/or ^99mTc‐chelate to improve the tumor targeting efficacy and in vivo kinetic profiles is currently in progress.     

Synthesis and biological evaluation of a series of 99mTc‐labeled diphosphonates as novel radiotracers with improved bone imaging

Three radiolabeled diphosphonates, ^99mTc‐labeled 1‐hydroxy‐3‐(2‐propyl‐1H‐imidazol‐1‐yl)propane‐1,1‐diyldiphosphonic acid (PIPrDP), 1‐hydroxy‐4‐(2‐propyl‐1H‐imidazol‐1‐yl)butane‐1,1‐diyldiphosphonic acid (PIBDP), and 1‐hydroxy‐5‐(2‐propyl‐1H‐imidazol‐1‐yl)pentane‐1,1‐diyldiphosphonic acid (PIPeDP), have been designed and synthesized with good chemical yields and high radiochemical purity. Their in vitro and in vivo biological properties were investigated and compared. All radiotracers evaluated in mice showed substantial retention in bone (8.42 ± 0.53, 9.08 ± 0.65, and 10.3 ± 0.61 ID%/g, respectively) at 1 h post‐injection and had rapid clearance in blood (1.9484, 1.3666, and 0.7704 ID%/g/min, respectively). ^99mTc‐PIBDP has the highest uptake ratio of bone‐to‐soft tissue at 1 h post‐injection among the three radiotracers. The results indicate that ^99mTc‐PIBDP is the most promising bone imaging agent. Copyright © 2012 John Wiley & Sons, Ltd.