Near-Infrared Fluorescence Imaging Contrast Agents for Clinical Research: Limitations and Alternatives

Introduction: Near-infrared fluorescence imaging is a technique that will establish itself in the short term at the international level because it is recognized for its potential to improve the performance of surgical interventions, its moderate investment and operating costs and its portability. Although the technology is now mature, there is currently the problem of the availability of contrast agents to be injected IV. The aim of this methodology article is to propose an alternative solution to the need for contrast agents for clinical research, particularly in oncology. Methodology: They consist of coupling a fluorescent marker in the form of an NHS derivative, such as IR DYE manufactured in compliance with GMP, with therapeutic monoclonal antibodies having marketing authorization for molecular imaging. For a given antibody, the marking procedure must be the subject of a validation file on the final preparation filtered on a sterilizing membrane at 0.22 μm. Once the procedure has been validated, it would be unnecessary to repeat the tests before each clinical research examination. A check of the marking by thin-layer chromatography (TLC) and place it in a sample bank at +4˚C for 1 month of each injected formulation would be sufficient for additional tests if necessary. Conclusion: Molecular near-infrared fluorescence imaging is experiencing development, the process of which could be accelerated by greater availability of clinical contrast agents. Alternative solutions are therefore necessary to promote clinical research in this area. These methods must be shared to make it easier for researchers.

Effect of magnetic resonance imaging in liver metastases

This letter to the editor is a commentary on a study titled"Liver metastases:The role of magnetic resonance imaging."Exploring a noninvasive imaging evaluation system for the biological behavior of hepatocellular carcinoma(HCC)is the key to achieving precise diagnosis and treatment and improving prognosis.This review summarizes the role of magnetic resonance imaging in the detection and evaluation of liver metastases,describes its main imaging features,and focuses on the added value of the latest imaging tools(such as T1 weighted in phase imaging,T1 weighted out of phase imaging;diffusion-weighted imaging,T2 weighted imaging).In this study,I investigated the necessity and benefits of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid for HCC diagnostic testing and prognostic evaluation.

Simplified liver imaging reporting and data system for the diagnosis of hepatocellular carcinoma on gadoxetic acid-enhanced magnetic resonance imaging

BACKGROUND The liver imaging reporting and data system(LI-RADS)diagnostic table has 15 cells and is too complex.The diagnostic performance of LI-RADS for hepatocellular carcinoma(HCC)is not satisfactory on gadoxetic acid-enhanced magnetic resonance imaging(EOB-MRI).AIM To evaluate the ability of the simplified LI-RADS(sLI-RADS)to diagnose HCC on EOB-MRI.METHODS A total of 331 patients with 356 hepatic observations were retrospectively analysed.The diagnostic performance of sLI-RADS A-D using a single threshold was evaluated and compared with LI-RADS v2018 to determine the optimal sLIRADS.The algorithms of sLI-RADS A-D are as follows:The single threshold for sLI-RADS A and B was 10 mm,that is,classified observations≥10mm using an algorithm of 10-19 mm observations(sLI-RADS A)and≥20 mm observations(sLI-RADS B)in the diagnosis table of LI-RADS v2018,respectively,while the classification algorithm remained unchanged for observations<10 mm;the single threshold for sLI-RADS C and D was 20 mm,that is,for<20 mm observations,the algorithms for<10 mm observations(sLI-RADS C)and 10-19 mm observations(sLI-RADS D)were used,respectively,while the algorithm remained unchanged for observations≥20 mm.With hepatobiliary phase(HBP)hypointensity as a major feature(MF),the final sLI-RADS(F-sLI-RADS)was formed according to the optimal sLI-RADS,and its diagnostic performance was evaluated.The times needed to classify the observations according to F-sLIRADS and LI-RADS v2018 were compared.RESULTS The optimal sLI-RADS was sLI-RADS D(with a single threshold of 20 mm),because its sensitivity was greater than that of LI-RADS v2018(89.8%vs 87.0%,P=0.031),and its specificity was not lower(89.4%vs 90.1%,P>0.999).With HBP hypointensity as an MF,the sensitivity of F-sLI-RADS was greater than that of LI-RADS v2018(93.0%vs 87.0%,P<0.001)and sLI-RADS D(93.0%vs 89.8%,P=0.016),without a lower specificity(86.5%vs 90.1%,P=0.062;86.5%vs 89.4%,P=0.125).Compared with that of LI-RADS v2018,the time to classify lesions according to FsLI-RADS was shorter(51±21 s vs 73±24 s,P<0.001).CONCLUSION The use of sLI-RADS with HBP hypointensity as an MF may improve the sensitivity of HCC diagnosis and reduce lesion classification time.

Liver metastases:The role of magnetic resonance imaging

The liver is one of the organs most commonly involved in metastatic disease,especially due to its unique vascularization.It’s well known that liver metastases represent the most common hepatic malignant tumors.From a practical point of view,it’s of utmost importance to evaluate the presence of liver metastases when staging oncologic patients,to select the best treatment possible,and finally to predict the overall prognosis.In the past few years,imaging techniques have gained a central role in identifying liver metastases,thanks to ultrasonography,contrast-enhanced computed tomography(CT),and magnetic resonance imaging(MRI).All these techniques,especially CT and MRI,can be considered the noninvasive reference standard techniques for the assessment of liver involvement by metastases.On the other hand,the liver can be affected by different focal lesions,sometimes benign,and sometimes malignant.On these bases,radiologists should face the differential diagnosis between benign and secondary lesions to correctly allocate patients to the best management.Considering the above-mentioned principles,it’s extremely important to underline and refresh the broad spectrum of liver metastases features that can occur in everyday clinical practice.This review aims to summarize the most common imaging features of liver metastases,with a special focus on typical and atypical appearance,by using MRI.

Optimized energy thresholds in a spectral computed tomography scan for contrast agent imaging

Spectral computed tomography(CT) based on photon counting detectors(PCDs) is a well-researched topic in the field of X-ray imaging. When PCD is applied in a spectral CT system, the PCD energy thresholds must be carefully selected, especially for K-edge imaging, which is an important spectral CT application. This paper presents a threshold selection method that yields better-quality images in K-edge imaging. The main idea is to optimize the energy thresholds ray-by-ray according to the targeted component coefficients, followed by obtaining an overall optimal energy threshold by frequency voting. A low-dose pre-scan is used in practical implementations to estimate the line integrals of the component coefficients for the basis functions. The variance of the decomposed component coefficients is then minimized using the Cramer–Rao lower bound method with respect to the energy thresholds. The optimal energy thresholds are then used to take a full scan and gain better image reconstruction with less noise than would be given by a full scan using the non-optimal energy thresholds. Simulations and practical experiments on imaging iodine and gadolinium solutions, which are commonly used as contrast agents in medical applications, were used to validate the method. The noise was significantly reduced with the same dose relative to the non-optimal energy thresholds in both simulations and in practical experiments.

FEASIBILITY STUDY OF AN ULTRASOUND CONTRAST AGENT(LEVOVIST) IN COLOR DOPPLER IMAGING OF LIVER NEOPLASMS

ＩＮＴＲＯＤＵＣＴＩＯＮＣｏｌｏｒＤｏｐｐｌｅｒｉｍａｇｉｎｇ（ＣＤＩ）ｆｏｒｔｈｅｎｏｎｉｎｖａｓｉｖｅａｓｓｅｓｍｅｎｔｏｆｂｏｔｈｎｏｒｍａｌａｎｄａｂｎｏｒｍａｌｌｉｖｅｒｖａｓｃｕｌａｒｉｔｙｈａｖｅｏｆｅｒｅｄａｓｉｇｎｉｆｉｃａｎｔ...

Preparation and biodistribution of ^(99)Tc^m-PIDP as bone imaging agent

A novel zoledronic acid derivative,1-hydroxy-2-(2-propyl-1H-imidazol-1-yl)ethane-1,1-diyldiphosphonic acid (PIDP), was synthesized by three-step reactions from 2-propyl-1H-imidazole. It was labeled with 99Tcm in conditions of 0.1 mg SnCl2.2H2O at pH 6.0 and 99TcmO4? in aqueous solution for 20 min at room temperature. The labeling yield and radiochemical purity of 99Tcm-PIDP are both higher than 95%. The biodistribution results show that the bone uptake is up to 8.47% ID/g which is the maximum of bone uptake at 30 min after injection of 99Tcm-PIDP in mice. The pharmacokinetic parameters can be estimated from the exponential equation of C=59.565e-11.307t+2.069e-1.211t. The clear bone image of rabbit was obtained at 120 min after injection of 99Tcm-PIDP. The results indicate that 99Tcm-PIDP has highly selective uptake in the skeletal and low uptake, rapid clearance in soft tissues, so it would be a potential novel bone imaging agent.

Preparation and preliminary biological evaluation of ^(99)Tc^m-TADP as bone imaging agent

TADP, 2-(1H-1,2,4-triazol-1-yl)-1-hydroxyethane-1,1-diphosphonic acid, was synthesized by three step reactions from the raw material 1H-1,2,4-triazole. Tcm-TADP was prepared with 5 mg TADP at pH 7.0 by joining 99 99TcmO4 with SnCl2·2H2O in aqueous solution for 10 min at room temperature. Both labeling yield and radiochemical - purity of Tcm-TADP were more than 95%. The biodistribution in rats and bone scan in rabbits were also studied. The 99 uptake of organ was expressed as %ID/g. The results showed that the bone uptake is up to 17.17%ID/g which is the maximum of bone uptake at 30 min after injection of Tcm-TADP in rats, bone-to-muscle and bone-to-blood uptake 99 ratios were 61.32 and 13.21, respectively. The clear bone image of rabbit was obtained at 120 min after injection of 99Tcm-TADP and clearance in soft tissue was visible. The preparation of 99Tcm-TADP was convenient and 99Tcm-TADP exhibited high uptake in bone, and it would be a potential new bone imaging agent.

The Applicability of Gd-DTPA Magnetic Resonance Imaging Contrast Agent for the Evaluation of Blood Compartment Flow Distribution in Hollow Fiber Hemodialyzers

Observation of flow distribution pattern in the hemodialyzers is significant as it is a valuable in-dication of the performance of these modules. Therefore, in this study, a feasible non-destructive Magnetic Resonance Imaging (MRI) technique is proposed to characterize the flow distribution in the blood compartment of hemodialyzers using Gd-DTPA MRI contrast agent. The distribution of flow is qualitatively observed in two commercial clinical dialyzers through an in-vitro experiment. The contrast enhanced T1 weighted images are acquired along the dialyzer length using Spin Echo (SE) pulse sequence after an injection of 0.5 mmol/L Gd-DTPA solution into the blood compartment. Although relatively uniform flow distribution pattern over the spatial volume of transverse images, close the dialyzer inlet is observed, the heterogeneity of flow distribution can be identified towards the blood outlet port. Furthermore, the signal intensity profiles formed by the injected Gd-DTPA are gradually decreased towards the outlet port. These results of the study suggest that although no advanced techniques and protocols available, MRI and Gd-DTPA contrast agent can be utilized to characterize the flow distribution within a dialyzer qualitatively.

Determination of Fragmentation Schemes and Metabolites of Fluorinated Histone Deacetylase Inhibitors for Use as Positron Emission Tomography Imaging Agents Using HPLC-MS/MS

High performance liquid chromatography coupled with tandem mass spectrometry was developed and validated as a method for the analysis of fluorinated histone deacetylase inhibitors (F-HDACi), and then employed to study their metabolism in biosystems. Four HDACi analogs labeled with the positron emission nuclide 18F constitute a group of potential positron emission tomography imaging agents, which were developed by the Institute of Nuclear Energy Research (INER) and coded as INER-1577 #1, #2, #3, and #4 during animal studies for the diagnosis of dementia. The performance of the method was found to be suitable for the determination of analog #3, and it was employed to determine the structures and fragmentation mechanisms of all four analogs and to study the biotransformations of analogs #3 and #4. The results indicated that the method used for the determination of analog #3 was suitable for determining the abundance of the analogs in chemical and biochemical tests with high precision, accuracy, reproducibility, and recovery. Weaknesses in the chemical bonding of the analogs were found to involve the fluoro, dimethylamino, and benzamide groups in a fragmentation mechanism deduced via tandem mass spectrometry. The metabolites of analogs #3 and #4 in rat liver microsomes and rat plasma were also identified to clarify their characteristic behaviors in biosystems. The major product of analogs #3 in liver microsomes was produced by hydroxylation of the benzylic carbon atom, but in rat plasma the metabolites of analog #3 were produced by hydrolysis of the benzamide group to give a diaminobiphenyl compound with the simultaneous replacement of a fluorine atom by a hydroxyl group. The metabolites of analog #4 in liver microsomes were produced by hydroxylation of the benzylic carbon atom and hydrolysis of the benzamide bond. The results of the studies characterized the chemical and biochemical behaviors of the series F-HADCi analogs.

Lactoferrin-Conjugated Polylactic Acid Nanobubbles Encapsulated Perfluoropentane as a Contrast Agent for Ultrasound/Magnetic Resonance Dual-Modality Imaging

The development of contrast agents that can be activated by multiple modes is of great significance for tumor diagnosis.In this study,the lactoferrin(Lf)-conjugated polylactic acid(PLLA)nanobubbles(Lf-PLLA NBs)were used to encapsulate liquid perfluoropentane(PFP)with the double emulsion method,creating PFP loaded(PFP/Lf-PLLA)NBs for the ultrasound/magnetic resonance dual-modality imaging of subcutaneous tumor.The parti-cle diameter and stability of nanobubbles were investigated by photon correlation spectroscopy.The biocompat-ibility of nanobubbles was preliminarily evaluated by cell proliferation and migration assay,hemolysis rate,and blood biochemistry analysis.A B-mode clinical ultrasound real-time imaging system was used to perform ultra-sonic imaging in vivo.Magnetic resonance imaging in vivo was applied with a clinical 3.0 T magnetic resonance imaging(MRI)scanner system.The mean particle diameter of PFP/Lf-PLLA NBs was 320.2±4.1 nm with a low polydispersity index(PDI,0.145±0.025),and the NBs were negatively charged(−11.4±0.4 mV).The transmis-sion electron microscopy(TEM)results showed that PFP/Lf-PLLA NBs exhibited highly monodispersed and pos-sessed an obvious spherical structure of nanocapsules.Nanobubbles had good stability at 4°C.Different concentrations of the PFP/Lf-PLLA NBs solution had no effect on the cell in cytotoxicity and cell migration,and the results of hemolysis rate and blood biochemistry assay also indicated the good biocompatibility of NBs.On the ultrasound/magnetic resonance imaging of tumor-bearing mice,PFP/Lf-PLLA NBs showed signifi-cantly enhanced contrast ability of tumor tissue.Therefore,PFP/Lf-PLLA NBs had great potential to be a contrast agent for tumor dual-modality imaging in vivo.

Imaging tumor hypoxia:Blood-borne delivery of imaging agents is fundamentally different in hypoxia subtypes

Dedicated to the memory of Professor Briton Chance on the ccasion of his 100th birthday(July24 th,2013),and remembering mary erciting discussions on the orygenation of breast cancer,ontumor hyporia in general and imaging of the orygenation status of malignant tumors.Hypoxic tissue subvolumes are a hallmark feat ure of solid malignant tumors,relevant for cancertherapy and patient outcome because they increase both the intrinsic aggressiveness of tumor cells and their resist ance to several commonly used anticancer strategies.Pathogenetic mech-anisms leading to hypoxia are diverse,may coexist within the same tumor and are commonlygrouped according to the duration of their ffects.Chronic hypoxia is mainly caused by difusionlimitations resulting from enlarged intercapilary distances and adverse difusion geometriesand--to a lsser extent--by hypoxemia,compromised perfusion or long-lasting microregionalfow stops.Conversely,acute hypoxia preferentilly results from transient disruptions in per.fusion.While each of these features of the tumor microenvironment can contribute to a criticalreduction of oxy gen availability,the delivery of imaging agents(as well as nutrients and anti-cancer agents)may be compromised or remain unaffected,Thus,a critial appraisal of the ffectsof the various mechanisms leading to hypoxia with regard to the blood-bome delivery of imagingagents is necessary to judge their ability to correctly represent the hypoxic phenotype of solidmalignancies.

Preclinical pharmacology study of neutral myocardial imaging agent ^(99m)TcN(NOEt)_2

To explore the biological properties of a new neutral myocardial imaging agent 99mTcN（NOEt）2,preparation and characterization of 99mTeN（NOEt）2, kinetics of blood-drug clearance in rabbits, biodistribution in rats, test of undue toxicity in mice and myocardial imaging in dogs were performed and volunteer imaging. Radiochemical purity of 99mTeN（NOEt）2 was over than 90% and stable for 6 hours at room temperature. Blood disappearance was analyzed with biexponential model, T1/2（α）=2.53 min, T1/2 （β）=330 min and Cl=378 mL/h were obtained. Biodistribution studies demonstrated that 99mTcN（NOEt）2 localized selectively in myocardium of rats. Cardiac uptake were 2.79, 2.25, 2.00 and 1.88%ID/organ at 5, 30, 60 and 90min of postinjection, respectively. The heart-to-lung activity ratio was 1.16 at 60 min. Images showed that pulmonary uptake decreased faster than cardiac uptake in a dog. The mean heart-to-lung activity ratios in a dog were 1.69, 2.40 and 2.55 at 10, 30 and 60min of postinjection, respectively. The heart was distinguishable on scans at 30min. Whole body imaging showed that cardiac uptake was 2.82%ID at 90min, but hepatic uptake was 30%ID and remained constant. The test of undue toxicity showed that the dose received by mice was 614 times as by human. Volunteer imaging suggests 99mTcN（NOEt）2 redistribution with time. 99mTcN（NOEt）2 exhibited favorable stabilities, biological properties and safety. It is worth for further studying in human.

Clinical application of several tumor imaging agents

Neoplasms is one of the main diseases for harming health. It is difficult to prevent the neoplasms because the factors of bringing out them are complex. To raise survival rate the early diagnosis of tumors is very important. Radionuclide imaging is useful to detect recurrent or residual disease and to identify benign or malignant tumor. Several tumor imaging agents as following have clinical significance in diagnosing tumors.

Microbubble ultrasound contrast agent with three esters and carboxylic methyl cellulose as main shell materials: Its preparation and imaging evaluation

Objective: To study on the preparation process of a new surfactant-based microbubble ultrasound contrast agent and to evaluate its contrast effects in vivo. Methods: Microbubble ultrasound contrast agent with three ester surfactants and other additives as its shell materials was prepared by sonication. Sulfur hexafluoride was adopted as the inner gas of the microbubbles. New methods through the combination of optical microscope and some softwares were used to measure the size distribution and the concentration of the microbubbles. Some parameters such as the pH value of the phosphate buffer, quantity of the carboxylic methyl cellulose in the shell materials, selection of the ultrasound power and process time, were studied. Six hybirded dogs were used to verify the in vivo contrast imaging of the contrast agent using second harmonic power Doppler modality. Safety and persistent time of the agent inner animal body were also investigated. Results: Ultrasound contrast agent prepared in the experiment had an average microbubble diameter of 3.95 microns with concentration of 3.6×109 microbubbles per millilitre. Carboxylic methyl cellulose was found as an important shell material which had obviously effect on the microbubble stability and production even with a little quantity. The buffer pH value also had a key role on the microbubble formation and the final production. When the buffer pH value reached 7.4, there was no microbubble produced. Under the approximate microbubble production, process time could be shorten with the increasing ultrasound power. The obvious ultrasound contrast imaging effects were detected in the dog's heart chamber and liver as well as kidney using only one millilitre agent when diluted. The agent was found safe to the dogs. At the same time, persistent time of the agent was found over 20 min in the dog's body. Conclusion: The new ultrasound contrast agent prepared in the experiment has high microbubble production and concentration, narrow microbubble size distribution ranging in several microns, well stability, little dosage needed in the contrast, well safety to the dogs and long persistent time, obvious contrast imaging effect in the dog's heart chamber, kidney and liver. These experiment data indicate that the new ultrasound contrast agent with three ester surfactants and carboxylic methyl cellulose as its main shell materials can be further developed for clinical purposes.

Experimental system for perfusion imaging and time-intensity processing based on ultrasound contrast agent

Objective: To present a self-developed experimental system for basic studies of blood perfusion imaging and time-intensity evaluating based on ultrasound contrast agent. Methods: The experimental system performed the image reconstruction and time-intensity processing with radio frequency signals. The system was comprised of ultra-high speed hardware data acquisition interface and low computational cost algorithms. The self-made contrast agent,blood mimic phantom and capillary phantom model were used to validate the experimental system. Results: The images acquired in blood phantoms with linear-array and curve-array transducers were given. The time-intensity curves corresponding to selected region of interested from image sequence were demonstrated. It was also shown the time-intensity based decay curves and a comparison of decay of ultrasound contrast agent under different ultrasound powers. Conclusion: Several experiments resulted from two in vitro phantom models show that the experimental system can be used to basic studies of blood perfusion and further clinical studies of microvasculature perfusion.

Synthesis, radiolabeling and animal studies of [^(131)I]MPPI: A 5-HTB_(1A) imaging agent

The synthesis and biological evaluation of serotonin (5-HTB1AB) imaging agent [P131PI]- 4-iodo-N-{2-[4-(2-methoxyphenyl)-piperazin-1-yl]-ethyl}-N-pridin-2-yl-benzamide ([P131PI]MPPI ) are reported. The chemical structure of aimed compound and intermediates were confirmed by IR, P1PHNMR, and MS. Radiochemical purity was above 99% determined by TLC. Biodistribution of [P131PI]MPPI in rats displayed high uptake in hippocam-pus and low uptake in cerebellum. The ratio of the uptake of [P131PI]MPPI in hippocampus to that in cerebellum was 2.90 at 30 min post injection. The radioactivity in thyroid was 0.069 and 0.128% ID/g organ at 5 min and 120 min, respectively, and it was increased with time, which suggests that in vivo deiodination may be the major route of me-tabolism. Ex vivo autoradiography of brain section displayed significant decrease of radioactivity in hippocampus when pretreated with 8-OH-DPAT, a selective 5HTB1AB agonist, compared with control. These findings strongly sug-gested that P131PI-MPPI could be used as an in vivo marker for studies of pharmacology of the 5-HTB1AB receptor system in animals.

Labeling and stability study On^（99m）Tc－tissue plasminogen activator as thrombus and tumor imaging agent

ＬａｂｅｌｉｎｇａｎｄｓｔａｂｉｌｉｔｙｓｔｕｄｙＯｎ￣（９９ｍ）Ｔｃ－ｔｉｓｓｕｅｐｌａｓｍｉｎｏｇｅｎａｃｔｉｖａｔｏｒａｓｔｈｒｏｍｂｕｓａｎｄｔｕｍｏｒｉｍａｇｉｎｇａｇｅｎｔＬｉＷｅｉ－Ｙｉ（李卫一），ＣａｏＧｕｏ－Ｘｉａｎ（曹国宪），Ｙｕ...

Preparation and preclinical studies of a hepatic receptor imaging agent

１ＩｎｔｒｏｄｕｃｔｉｏｎＨｅｐａｔｉｃｂｉｎｄｉｎｇｐｒｏｔｅｉｎ（ＨＢＰ）ｉｓａｎａｓｉａｌｏｇｌｙｃｏｐｒｏｔｅｉｎｒｅｃｅｐｔｏｒ，ｗｈｉｃｈｒｅｓｉｄｅｓｏｎｌｙａｔｔｈｅｃｅｌｓｕｒｆａｃｅｏｆｍａｍｍａｌｉａｎｈｅｐａｔｏｃｙｔｅｓ，...

RADIOIODINATION AND PHARMACOKINETICS OF BIVALENT ANALOG OF PRACTOLOL AS MYOCARDIAL IMAGING AGENT

ＲＡＤＩＯＩＯＤＩＮＡＴＩＯＮＡＮＤＰＨＡＲＭＡＣＯＫＩＮＥＴＩＣＳＯＦＢＩＶＡＬＥＮＴＡＮＡＬＯＧＯＦＰＲＡＣＴＯＬＯＬＡＳＭＹＯＣＡＲＤＩＡＬＩＭＡＧＩＮＧＡＧＥＮＴＣａｏＧｕｏｘｉａｎ，ＬｉＷｅｉｙｉ，ＺｈａｎｇＲｏｎｇｊｕｎａｎｄＹｕＨｕｉｘ...