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PubMed2004

Motexafin gadolinium: gadolinium (III) texaphyrin, gadolinium texaphyrin, Gd-Tex, GdT2B2, PCI 0120.

Motexafin gadolinium [gadolinium (III) texaphyrin, gadolinium texaphyrin, Gd-Tex, GdT2B2, PCI 0120] is a radiosensitising agent developed for use in cancer therapy. It is cytotoxic in haematological malignancies by selectively localising in cancer cells that have high rates of metabolism. Motexafin gadolinium inhibits cellular respiration resulting in the production of reactive oxygen species and inducing apoptosis. It is being developed by Pharmacyclics in the US. Bulk motexafin gadolinium is supplied to Pharmacyclics by the US company, Celanese, through a manufacturing and supply agreement between the two companies. In June 2003, at the 39th Annual Meeting of the American Society of Clinical Oncology (ASCO-2003), the importance of having an agent for the treatment of brain metastases from lung cancer was highlighted. Results of a phase III study were presented that showed that motexafin gadolinium treatment was associated with a delay in time to neurological and neurocognitive progression in lung cancer patients. This was an important finding, as 46.6% of lung cancer patients already have brain metastases at the time of initial diagnosis, compared with only 2.7% of breast cancer patients. Brain metastases are also often the only site of metastatic disease in patients with lung cancer. In December 2002, Pharmacyclics began a phase III trial of motexafin gadolinium in patients with brain metastases (brain cancer in phase table) from lung cancer in the US, Europe, Canada and Australia. The trial is known as the Study of neurologic progression with Motexafin gadolinium And Radiation Therapy (SMART) and will compare whole-brain irradiation with whole-brain irradiation plus motexafin gadolinium in 550 patients. The primary efficacy endpoint is time to neurological progression and the secondary endpoints are survival and neurocognitive function. In January 2003, the US FDA completed its Special Protocol Assessment (SPA) of the SMART trial with a positive result and by June 2003, enrollment had begun. In addition, phase I trials are underway in children with intrinsic pontine glioma and adults with head and neck, lung and pancreatic cancers. A phase II trial is also being conducted in the US in patients with glioblastoma multiforme. Enrollment in this trial has been completed and preliminary results have been reported. Pharmacyclics has completed enrollment and follow-up of adults in its pivotal phase III trial of motexafin gadolinium as a radiation sensitiser for the treatment of brain metastases. The trial was conducted at 35 centres in Europe, Canada and the US. Full results from this initial phase III trial were presented at the annual meeting of the American Society of Clinical Oncology (ASCO) in Orlando, Florida, USA, held in May 2002. Pharmacyclics also announced in October 2002, at the 44th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), that motexafin gadolinium significantly prolonged time to neurological progression when added to whole brain radiation therapy and reduced the number of deaths in patients with brain tumour. Pharmacyclics announced in September 2000 that it has initiated two NCI-sponsored phase I trials conducted under a Cooperative Research and Development Agreement (CRADA) between Pharmacyclics and the NCI. The first trial, conducted in patients with stage IIIA non-small cell lung cancer, was designed to determine the safety of two different dosing regimens of motexafin gadolinium during preoperative radiotherapy after induction chemotherapy. The second study was designed to examine the use of motexafin gadolinium in combination with stereotactic Gamma Knife radiosurgery in patients with primary glioblastoma mutiforme. Two phase I clinical trials have also been conducted for the treatment of newly diagnosed glioblastoma multiforme at the UCLA Jonsson Comprehensive Cancer Center, USA. These phase I studies were sponsored by the NCI and were conducted under a CRADA with the NCI. Pharmacyclics has also completed multicentre US phase II clinical trials of motexafin gadolinium fin gadolinium in patients with metastatic tumours of the brain who require whole brain radiotherapy. Motexafin gadolinium is in a phase II trial in patients with lymphomas and multiple myeloma in the US.

Animals↗
PubMed1999

Magnetic resonance imaging of the abdominal aorta and iliac vessels using combined 3-D gadolinium-enhanced MRA and gadolinium-enhanced fat-suppressed spoiled gradient echo sequences.

This study evaluates a combined protocol consisting of breath hold immediate post gadolinium 3-D gradient echo MR angiography and blood pool phase gadolinium-enhanced breath hold 2-D fat-suppressed spoiled gradient echo (SGE) sequences in the examination of diseases of the abdominal aorta and iliac vessels. Thirty-two patients with suspected disease of the abdominal aorta, major aortic branches, or iliac vessels underwent MR angiographic study from January 1996 to January 1997. Examinations were performed on a 1.5 T MR imager using 2-D axial SGE, coronal 3-D fast imaging in steady state precession (3-D FISP) following bolus administration of 40 mL of gadolinium, and axial and coronal blood pool phase gadolinium-enhanced fat-suppressed SGE. Post-processed data, including 3-D reconstructions using maximum intensity projection (MIP), targeted MIP, and multiplanar reconstruction (MPR) were evaluated. MR findings in all patients were correlated as follows: surgery (13 patients), angiography (11 patients), contrast enhanced CT (3 patients), non-contrast enhanced CT (1 patient), color doppler US (2 patients), and previous MR study (2 patients). MR findings correlated closely with findings at surgery or other imaging studies in 31 of 32 patients. One patient had renal artery occlusion that was misinterpreted as mild stenosis. The following vascular diseases were present: aneurysm disease [10 patients: aortic aneurysm (8 patients), inflammatory aneurysm (2 patients)], thoracoabdominal aortic dissection (2 patients), arteriovenous fistula (1 patient), stenoses and/or occlusion of the abdominal aorta, major aortic branches and iliac vessels [12 patients: stenoses and/or occlusion of the abdominal aorta with stenoses of the iliac vessels (9 patients), renal artery stenosis (2 patients), occlusion of the abdominal aorta (1 patient)], and occluded artery to pancreatic transplant artery (1 patient). Five patients had normal studies. The 3-D FISP technique accurately defined the luminal contours of vessels, allowing precise depiction of vessel stenosis (i.e., renal artery stenosis or common iliac artery stenosis) and clear demonstration of relationship of aortic branch vessels (i.e., renal arteries) to underlying aortic pathology (i.e., aortic aneurysm or dissection). Blood pool phase gadolinium-enhanced fat-suppressed SGE images were useful in the evaluation of the external surface of vessel walls, and providing accurate measurement of aneurysm diameter and other associated vascular entities (i.e., inflammatory aneurysm, left-sided IVC). Targeted MIP or MPR reconstruction were important for assessing stenoses of medium sized vessels such as renal arteries and branches of the iliac arteries, and for identifying accessory arteries. The combination of immediate post gadolinium 3-D FISP and blood pool phase gadolinium-enhanced fat-suppressed SGE is useful in the evaluation of the abdominal aorta, major aortic branches and iliac vessels. Immediate post gadolinium 3-D FISP images provides diagnostically useful information regarding vessel luminal contour, while blood pool phase gadolinium-enhanced fat-suppressed SGE provides ancillary information on the vessel wall and surrounding tissue.

Adolescent↗
PubMed1997

Single-dose gadolinium with magnetization transfer versus triple-dose gadolinium in the MR detection of multiple sclerosis lesions.

PURPOSE: To compare the efficacy of single-dose gadolinium with magnetization transfer contrast (MTC) with that of triple-dose gadolinium in detecting enhancing multiple sclerosis lesions. METHODS: Twenty-one patients with multiple sclerosis were examined with MR imaging first with 0.1 mmol/kg gadolinium (single dose) and then, after 24 to 72 hours, with 0.3 mmol/kg gadolinium (triple dose). T2-weighted fast spin-echo and T1-weighted spin-echo MR images with and without MTC were obtained before contrast administration followed by either T1-weighted spin-echo images with MTC (single dose) or conventional T1-weighted spin-echo images (triple dose), starting 5, 17, and 29 minutes after contrast administration. All images were evaluated in a blinded fashion and scored in random order by two readers. Outcome parameters included number of enhancing lesions, number of active MR examinations (those containing at least one enhancing lesion), contrast ratio (signal intensity of enhancing lesion divided by signal intensity of normal-appearing white matter), and size of enhancing lesions. RESULTS: Eighty-one percent more enhancing lesions and 49% more active MR examinations were detected when a triple dose of gadolinium was used as compared with a single dose. The level of agreement between readers as to the number of enhancing lesions was significantly higher for triple-dose than for single-dose gadolinium. With triple-dose gadolinium, contrast ratios and areas of enhancement increased by 10% and 33%, respectively. Delayed imaging increased the size of the lesion by 11% on single-dose MTC images and by 18% on triple-dose images. CONCLUSION: Triple-dose gadolinium is more effective (higher sensitivity and interobserver agreement) than single-dose gadolinium in combination with MTC in detecting enhancing multiple sclerosis lesions.

Adult↗
PubMed1988

Comparative pharmacokinetics of gadolinium DTPA and gadolinium chloride.

An intravenous injection of 153Gd-labeled gadolinium-DTPA or gadolinium chloride was given to 60 rats, which were killed either 15, 40, 120, 300, 900, or 3600 seconds later. Tissue concentrations of gadolinium in the blood, liver, spleen, stomach, pancreas, renal cortex, renal medulla, lungs, heart, adrenals, gluteal muscle, fat, skin, thymus, brain, thyroid, and parathyroids were measured. Five animals were killed at each time interval with gadolinium-DTPA, and at each of the latter four time intervals (15 and 40 seconds excluded) with gadolinium chloride. The pharmacokinetics of gadolinium-DTPA and chloride differ markedly in terms of tissue concentration, distribution volumes, and the time course of these parameters. Gadolinium, when injected as a chloride, evidently forms insoluble carbonate and phosphate precipitates in the blood, which are taken up by the reticuloendothelial system. The distribution of gadolinium-DTPA on dynamic MRI should closely parallel the distribution of iodinated contrast media on dynamic computed tomography.

Animals↗
PubMed1999

Predictive value of gadolinium-enhanced magnetic resonance imaging for relapse rate and changes in disability or impairment in multiple sclerosis: a meta-analysis. Gadolinium MRI Meta-analysis Group.

BACKGROUND: Reliable prognostic factors are lacking for multiple sclerosis (MS). Gadolinium enhancement in magnetic resonance imaging (MRI) of the brain detects with high sensitivity disturbance of the blood-brain barrier, an early event in the development of inflammatory lesions in MS. To investigate the prognostic value of gadolinium-enhanced MRI, we did a meta-analysis of longitudinal MRI studies. METHODS: From the members of MAGNIMS (European Magnetic Resonance Network in Multiple Sclerosis) and additional centres in the USA, we collected data from five natural-course studies and four placebo groups of clinical trials completed between 1992 and 1995. We included a total of 307 patients, 237 with relapsing disease course and 70 with secondary progressive disease course. We investigated by regression analysis the relation between initial count of gadolinium-enhancing lesions and subsequent worsening of disability or impairment as measured by the expanded disability status scale (EDSS) and relapse rate. FINDINGS: The relapse rate in the first year was predicted with moderate ability by the mean number of gadolinium-enhancing lesions in monthly scans during the first 6 months (relative risk per five lesions 1.13, p=0.023). The predictive value of the number of gadolinium-enhancing lesions in one baseline scan was less strong. The best predictor for relapse rate was the variation (SD) of lesion counts in the first six monthly scans which allowed an estimate of relapse in the first year (relative risk 1.2, p=0.020) and in the second year (risk ratio=1.59, p=0.010). Neither the initial scan nor monthly scans over six months were predictive of change in the EDSS in the subsequent 12 months or 24 months. The mean of gadolinium-enhancing-lesion counts in the first six monthly scans was weakly predictive of EDSS change after 1 year (odds ratio=1.34, p=0.082) and 2 years (odds ratio=1.65, p=0.049). INTERPRETATION: Although disturbance of the blood-brain barrier as shown by gadolinium enhancement in MRI is a predictor of the occurrence of relapses, it is not a strong predictor of the development of cumulative impairment or disability. This discrepancy supports the idea that variant pathogenetic mechanisms are operative in the occurrence of relapses and in the development of long-term disability in MS.

Adolescent↗
PubMed1994

Renal tolerance of gadolinium-DOTA and gadolinium-DTPA in rats.

RATIONALE AND OBJECTIVES: Although gadolinium chelates are mainly eliminated by the kidney, there is limited information about their effects. The renal tolerance of these compounds on renal function in an in vivo rat model are evaluated. METHODS: A combination of renal ischemia and intrarenal iodinated contrast agent infusion (diatrizoate) led to a reproducible and reversible model of acute renal failure (n = 5). Using this model, the renal tolerance of gadolinium DOTA (Gd-DOTA) (n = 10) and gadolinium DTPA (Gd-DTPA) (n = 10) were evaluated. The effects of the association of Gd-DOTA with diatrizoate (n = 5) on renal function also were assessed. RESULTS: Gadolinium DOTA induced no change in serum creatinine and creatinine clearance. Gadolinium DTPA induced a significant increase in serum creatinine (50 to 83 +/- 5 and 70 +/- 6 mumol/L) before and at 24 and 48 hours, respectively (P < .05), and a decrease in creatinine clearance from 1.6 +/- 0.1 to 0.8 +/- 0.1; 1.2 +/- 0.1 mL/mL before and at 24 and 48 hours, respectively (P < .05). In this model, Gd-DOTA did not modify the renal tolerance of diatrizoate as assessed with serum creatinine and creatinine clearance. CONCLUSIONS: Gadolinium DOTA is not nephrotoxic and can be infused in association with iodinated contrast media. In this model, Gd-DTPA induced reversible renal failure.

Acute Kidney Injury↗
PubMed2006

Gadolinium diethylenetriaminopentaacetic acid-loaded chitosan microspheres for gadolinium neutron-capture therapy.

In order to provide a suitable device that would contain water-soluble drugs, highly water-soluble gadolinium diethylenetriaminopentaacetic acid-loaded chitosan microspheres (CMS-Gd-DTPA) were prepared by the emulsion method using glutaraldehyde as a cross-linker and Span 80 as a surfactant for gadolinium neutron-capture therapy of cancer. The gadolinium content and the mass median diameter of CMS-Gd-DTPA were estimated. The size and morphology of the CMS-Gd-DTPA were strongly influenced by the initial applied weight ratio of Gd-DTPA:chitosan. FTIR spectra showed that the electrostatic interaction between chitosan and Gd-DTPA accelerated the formation of gadolinium-enriched chitosan microspheres. Sufficient amounts of glutaraldehyde and Span 80 were necessary for producing discrete CMS-Gd-DTPA. The CMS-Gd-DTPA having a mass median diameter 11.7microm and 11.6% of gadolinium could be used in Gd-NCT following intratumoral injection.

Antineoplastic Agents↗
PubMed1994

Dynamic contrast-enhanced MR imaging of the upper abdomen: enhancement properties of gadobutrol, gadolinium-DTPA-polylysine, and gadolinium-DTPA-cascade-polymer.

The enhancement properties of gadobutrol (40 and 80 mumol/kg body weight, 550 daltons), gadolinium-DTPA-polylysine (20 mumol/kg body weight, 53,000 daltons) and gadolinium-DTPA-cascade-polymer (20 mumol/kg body weight, < 30,000 Daltons) were investigated in abdominal MR imaging using a pig model (n = 24). Signal intensities before and after contrast media application were assessed using a fast single slice FLASH sequence. Measurements were made every 4 s within the first 116 s, every minute between 4 and 10 min and after 15, 20, 30, 40, 50, 60, 90, and 120 min after contrast media injection. Injection of gadobutrol resulted in typical signal intensity curves characterizing it as an extracellular agent similar to gadopentetate dimeglumine. Significant enhancement was found in all tissues except the trunk muscles when the lower dose was administered. Gadolinium-DTPA-polylysine injection resulted also in significant enhancement of the liver, the pancreas, and the renal cortex, but not of the trunk muscle, reflecting its blood pool properties known also from other macromolecular contrast agents. The signal intensity curves obtained after gadolinium-DTPA-cascade-polymer injection were similar to those obtained after polylysine injection, stressing the blood pool character of this new type of blood pool agent.

Abdomen↗
PubMed1995

Biodistribution and metabolism of targeted and nontargeted protein-chelate-gadolinium complexes: evidence for gadolinium dissociation in vitro and in vivo.

The intracellular metabolism of receptor-targeted 153Gd-DTPA-glycoproteins was studied in vitro and in vivo. These agents bound to cell surface receptors, underwent receptor mediated endocytosis, and were rapidly degraded to a metabolite which co-migrated with a 153Gd-DTPA-lysine standard on thin layer chromatography. The rates of dissociation of 153Gd and 111In from a glycoprotein-chelate conjugate were determined in vitro. Gadolinium readily dissociated, in a pH-sensitive manner, from glycoprotein-DTPA, and to a lesser degree glycoprotein-MX-DTPA. The biodistribution of targeted and blood pool 153Gd/111In labeled proteins also suggested that gadolinium dissociates from protein-DTPA and protein-MX-DTPA and their metabolites leading to an accumulation of gadolinium in bone. Metal-DTPA-glycoprotein agents targeted to cell surface receptors can still produce very high concentrations of radioactive or paramagnetic metals within the lysosome due to the high rate of accumulation afforded by receptor mediated endocytosis and the low release rate of metabolites such as metal-DTPA-lysine. However, the continued development of gadolinium based macromolecular agents will require improvements in bifunctional chelates.

Animals↗
PubMed2001

Moving-table reduced-dose gadolinium-enhanced three-dimensional magnetic resonance angiography: velocity-dependent method with three-phase gadolinium infusion.

The purpose of this study was to develop a method for reducing gadolinium dose and suppressing venous overlap in moving-table three-dimensional (3D) magnetic resonance (MR) angiography from the abdomen to the feet. Thirty-one patients underwent three-phase infusion of 16-18 mL of gadolinium: infusion rates and imaging times were determined after taking into account mean blood flow velocity, so that image acquisition was synchronized with peak arterial enhancement at both the first and third stations (velocity-dependent method). Twenty-three other patients underwent slow infusion of 38 mL of gadolinium with fixed acquisition time (high-dose method). The image quality for the two methods was compared. The velocity-dependent method produced good image quality with significantly less venous overlap than the high-dose method, especially in the below-the-knee region (P <.001). The velocity-dependent method provides satisfactory MR angiograms using 16-18 mL of gadolinium in patients having various blood flow velocities.

Adult↗
PubMed2001

Gadolinium-enhanced MR angiography (Gd-MRA) of thoracic vasculature in an animal model using double-dose gadolinium and quiet breathing.

OBJECTIVE: To evaluate a gadolinium-enhanced MR angiography (Gd-MRA) imaging protocol for the assessment of thoracic vessels using double-dose gadolinium and quiet breathing. An animal model was used to simulate imaging in infants and young children. MATERIAL AND METHODS: Six baboons (Papio anubis), mean weight 5.7 kg, were sedated and intubated. After the injection of double-dose Gd-DTPA (0.2 mmol/kg) through a peripheral vein, a coronal spoiled 3D gradient-echo volume acquisition was obtained during quiet breathing. Two radiologists reviewed the images for visualization of aortic arch, brachiocephalic vessel origins, pulmonary arteries (central, upper lobe and descending branches), and pulmonary veins (upper and lower). RESULTS: Visualization was excellent for the aortic arch, brachiocephalic vessel origins, and pulmonary arteries, including the hilar branches. Visualization was excellent for the lower and right upper pulmonary veins and fair for the left upper pulmonary vein. There was excellent agreement between radiologists. CONCLUSION: Imaging of thoracic vessels with Gd-MRA using double gadolinium during quiet breathing was effective in our animal model. The advantages of this technique include a short imaging time and depiction of vascular segments--branches of pulmonary arteries and intraparenchymal segments of pulmonary veins--not optimally visualized with other non-invasive imaging techniques.

Animals↗
PubMed2003

Small particulate gadolinium oxide and gadolinium oxide albumin microspheres as multimodal contrast and therapeutic agents.

RATIONALE AND OBJECTIVE: To prepare and characterize new particulate contrast media, small particulate gadolinium oxide (SPGO) and gadolinium oxide albumin microspheres (GOAM), as prototype multimodal imaging and therapeutic agents. METHODS: SPGO was purchased from Alfa Aesar Inc. (Ward Hill, MA). GOAM were synthesized via ultrasonic irradiation using SPGO and 5% bovine serum albumin in aqueous solution. SPGO and GOAM were characterized by size, concentration, structure, and gadolinium content. Their relaxivity at high magnetic field strength and x-ray attenuating abilities were evaluated in 0.4% agar gel at room temperature. RESULTS: SPGO were confirmed to be 20-40 nm in diameter. GOAM have an average size of 2 to 5 microm and show a relatively homogeneous distribution of SPGO within the albumin microspheres. T1 and T2 relaxivity of GOAM was 6.7 seconds(-1) mmol/L(-1) and 38.5 seconds(-1) mmol/L(-1), respectively, while that of SPGO was 0.2 seconds(-1) mmol/L(-1) and 6.8 seconds(-1) mmol/L(-1), respectively. At 0, 0.004, 0.16, 4.0, and 16.0 mmol/L SPGO, x-ray attenuation values were measured at 2.11, 3.48, 7.06, 39.83, and 187.33 Hounsfield units, respectively. CONCLUSIONS: Use of SPGO and SPGO encapsulated in non-heat-hardened albumin microspheres (GOAM) represents a new approach. SPGO and GOAM have suitable physicochemical properties to warrant further biophysical and animal studies and reevaluation of toxicity limitations.

Animals↗
PubMed1996

Comparison of gadolinium-DTPA and macromolecular gadolinium-DTPA-polylysine for contrast-enhanced pulmonary time-of-flight magnetic resonance angiography.

RATIONALE AND OBJECTIVES: The authors investigated the enhancing effect of low-dose administration of the macromolecular, paramagnetic contrast medium gadolinium (Gd)-DTPA-polylysine (average molecular weight, 40,000-50,000 dalton [D]) compared with Gd-DTPA (molecular weight, 547 D) in time-of-flight magnetic resonance angiography of unilaterally damaged sheep lungs. MATERIALS AND METHODS: Thirteen heart-lung preparations were examined in the head coil of a 1.5-tesla imager (Magnetom SP, Siemens, Erlangen, Germany). The authors performed time-of-flight angiograms (coronal; repetition time, 35 mseconds; echo time, 6 mseconds; 20 degrees flip angle; pixel size 1.0 x 1.0 x 1.5 mm3) before and after application of the contrast agents. Gadolinium-DTPA-polylysine was used in a dose of 0.027 mmol/kg body weight while Gd-DTPA was injected in variable doses. RESULTS: After Gd-DTPA-polylysine, signal intensity increased by 118% in pulmonary arteries in healthy lungs and by 121% in damaged lungs (P < 0.001). In addition, the contrast-to-noise ratio measured between pulmonary arteries and perivascular parenchyma increased significantly (P < 0.01). On three-dimensional angiograms, two more generations of vascular branches could be detected. A dose of Gd-DTPA 6.1 times higher than the Gd-DTPA-polylysine dose was necessary to obtain the same contrast enhancing effect as Gd-DTPA-polylysine in healthy lungs. In damaged lungs, none of the administered doses of Gd-DTPA reached the average contrast enhancement of Gd-DTPA-polylysine. CONCLUSIONS: The authors' measurements demonstrate significant improvement of time-of-flight angiograms by low-dose administration of Gd-DTPA-polylysine.

Animals↗
PubMed1994

Bladder tumor staging: comparison of contrast-enhanced CT, T1- and T2-weighted MR imaging, dynamic gadolinium-enhanced imaging, and late gadolinium-enhanced imaging.

PURPOSE: To evaluate the accuracy of contrast material-enhanced computed tomography (CT), unenhanced T1- and T2-weighted magnetic resonance (MR) imaging, and dynamic gadolinium-enhanced spoiled gradient-echo MR imaging in the staging of bladder cancer. MATERIALS AND METHODS: Thirty-six patients with histologically proved bladder cancer were prospectively examined with CT and MR imaging before tumor resection. Images were evaluated in a blinded fashion. RESULTS: All methods depicted tumors comparably well. Staging was correct in 16 of 29 patients (55%) with CT and 27 of 36 patients (75%) overall with MR imaging. Overstaging was the most common error, and both CT and MR imaging were more accurate for higher-staged tumors. CONCLUSION: CT and MR imaging perform well in the detection of tumors but are less accurate in staging. Dynamic gadolinium-enhanced MR imaging is better than other techniques, but the difference is not statistically significant.

Carcinoma, Transitional Cell↗
PubMed2006

Reactions of gadolinium atoms and dimers with CO: formation of gadolinium carbonyls and photoconversion to CO activated molecules.

Reactions of gadolinium atoms and dimers with carbon monoxide molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. Mononuclear Gd(CO)x (x = 1-3) and dinuclear Gd2(CO)x (x = 1, 2) gadolinium carbonyls formed spontaneously on annealing. The Gd(CO)x complexes are CO terminal-bonded carbonyls, whereas the Gd2CO and Gd2(CO)2 carbonyl complexes were characterized to have asymmetrically bridging and side-on-bonded CO, which are drastically activated with remarkably low C-O stretching frequencies. The cyclic Gd2(mu-C)(mu-O) and Gd3(mu-C)(mu-O) molecules in which the C-O triple bond is completely cleaved were also formed on annealing. The Gd2(CO)2 complex rearranged to the more stable c-Gd2(mu-O)(mu-CCO) isomer, which also has a four-membered ring structure with one CO being completely activated.

Journal Article↗
PubMed1995

Detection and quantitation of gadolinium chelates in human serum and urine by high-performance liquid chromatography and post-column derivatization of gadolinium with Arsenazo III.

A narrow-bore high-performance liquid chromatography method was developed for simultaneous separation of gadolinium diethylenetriaminepentaacetic acid (GdDTPA), the monomethylamide (GdDTPA-MMA) and the bis-methylamide (GdDTPA-BMA) in human serum and urine. The Gd complexes were detected at 658 nm after post-column derivatization with Arsenazo III. The serum samples were ultrafiltrated, whereas the urine samples were centrifuged and diluted before analysis. With an injection volume of 10 microliters on a 2.1 mm ID reversed-phase column, the limit of detection of GdDTPA-BMA was calculated as 0.3 microM and 1.1 microM in serum and urine, respectively. The method was validated with respect to GdDTPA-BMA with a limit of quantification set to 2 microM and 10 microM in serum and urine, respectively. The best fit of the calibration curve was obtained using non-linear regression according to the equation Y = A+BX+CX2 in the concentration ranges 2-800 microM and 10-2000 microM of GdDTPA-BMA in serum and urine, respectively. The precision of the method was found to range from 1 to 4% RSD. The recoveries of GdDTPA-BMA spiked in serum and urine were higher than 95% with an RSD equal to or less than 4%. The serum samples were stable for at least 5 months when stored at -70 degrees C, and the urine samples were stable for a least 6 months when stored at -20 degrees C.

Amides↗
PubMed1991

An improved method for the preparation of liposomal gadolinium-DTPA. Ionophore-mediated active entrapment of gadolinium.

We have developed an improved method for the production of liposomal gadolinium-DTPA (Gd-DTPA). The ionophore A23187 facilitates the uptake of externally added Gd into the interior aqueous space of a unilamellar lipid vesicle, where it is chelated by passively entrapped DTPA to form the Gd-DTPA chelate in situ. The presence of a pH gradient across the vesicle membrane is not essential for Gd uptake, the extent of which apparently is limited only by the interior concentration of the chelator. Once formed internally, the Gd-DTPA complex is retained within the vesicles for at least several days at room temperature. Biodistribution studies in mice indicate that liposomal Gd-DTPA prepared by this ionophoretic loading procedure exhibits biodistribution and clearance characteristics similar to 153Gd-DTPA-labeled liposomes prepared by means of passive entrapment of the preformed chelate.

Calcimycin↗
PubMed1995

Comparison of gadolinium-DTPA and polylysine-gadolinium-DTPA--enhanced magnetic resonance imaging of hepatocarcinoma in the rat.

RATIONALE AND OBJECTIVES: To compare the magnetic resonance (MR) imaging characteristics of gadolinium-DTPA (Gd-DTPA), a low-molecular-weight contrast agent, and polylysine-Gd-DTPA, a macromolecular contrast agent, in two types of hepatocarcinomas (HCC) in the rat. METHODS: T1-weighted spin-echo images were obtained in 13 rats with chemically induced HCC and 26 rats with Novikoff HCC before and 3 minutes to 60 hours after administration of either Gd-DTPA or polylysine-Gd-DTPA. RESULTS: Three minutes after polylysine-Gd-DTPA administration, the tumor-to-liver contrast of the two types of HCC increased significantly (positive contrast for chemically induced HCC and negative contrast for Novikoff HCC). At 30 minutes and 60 hours, the tumor-to-liver contrast remained above baseline values in chemically induced HCC and returned progressively to baseline values in Novikoff HCC. No significant increase in tumor-to-liver contrast was observed after Gd-DTPA administration. CONCLUSIONS: These results suggest that polylysine-Gd-DTPA provides a higher and more prolonged increase in tumor-to-liver contrast than Gd-DTPA.

Angiography↗