Calvarial and skull base metastases: comparison of nonenhanced and Gd-DTPA-enhanced MR images

Fourteen patients with calvarial metastases were studied with magnetic resonance (MR) imaging before and after intravenous administration of gadolinium diethylenetriamine-pentaacetic acid (DTPA) to evaluate the utility of contrast material enhancement for the detection of calvarial metastatic tumor. MR imaging was also performed before and after enhancement in 60 patients for reasons other than evaluation of metastases or calvarial tumor, to determine the apperance of the normal calvaria with enhancement. The normal pattern of fat distribution in the diploic space was typically symmetric. Except for enhancement of diploic veins and meninges near pacchionian granulations, the normal diploic space did not enhance. Calvarial metastases typically enhanced with Gd-DTPA. Enhanced MR images were superior to nonenhanced studies for detecting subtle intradiploic metastases but were inferior to nonenhanced studies for detecting tumor extension into fat-containing areas. Careful comparison of nonenhanced and enhanced MR images is required for complete evaluation of lesions affecting the calvaria and skull base.     

Comparison of two superparamagnetic viral-sized iron oxide particles ferumoxides and ferumoxtran-10 with a gadolinium chelate in imaging intracranial tumors

BACKGROUND AND PURPOSE: Ultrasmall superparamagnetic iron oxide particles result in shortening of T1 and T2 relaxation time constants and can be used as MR contrast agents. We tested four hypotheses by evaluating MR images of intracranial tumors after infusion of two iron oxide agents in comparison with a gadolinium chelate: 1) Ferumoxtran in contrast to ferumoxides can be used as an intravenous MR contrast agent in intracranial tumors; 2) ferumoxtran enhancement, albeit delayed, is similar to gadolinium enhancement; 3) ferumoxtran-enhanced MR images in contrast to gadolinium-enhanced MR images may be compared with histologic specimens showing the cellular location of iron oxide particles; 4) ferumoxtran can serve as a model for viral vector delivery. METHODS: In 20 patients, ferumoxides and ferumoxtran were intravenously administered at recommended clinical doses. MR imaging was performed 30 minutes and 4 hours after ferumoxides infusion (n = 3), whereas ferumoxtran-enhanced MR imaging (n = 17) was performed 6 and 24 hours after infusion in the first five patients and 24 hours after infusion in the remaining 12. MR sequences were spin-echo (SE) T1-weighted, fast SE T2- and proton density-weighted, gradient-recalled-echo T2*-weighted, and, in four cases, echo-planar T2-weighted sequences. Representative regions of interest were chosen on pre- and postcontrast images to compare each sequence and signal intensity. RESULTS: Despite some degree of gadolinium enhancement in all tumors, no significant T1 or T2 signal intensity changes were seen after ferumoxides administration at either examination time. Fifteen of 17 patients given ferumoxtrans had T1 and/or T2 shortening consistent with iron penetration into tumor. Histologic examination revealed minimal iron staining of the tumor with strong staining at the periphery of the tumors. CONCLUSION: 1) Ferumoxtran can be used as an intravenous MR contrast agent in intracranial tumors, mostly malignant tumors. 2) Enhancement with ferumoxtran is comparable to but more variable than that with the gadolinium chelate. 3) Histologic examination showed a distribution of ferumoxtran particles similar to that on MR images, but at histology the cellular uptake was primarily by parenchymal cells at the tumor margin. 4) Ferumoxtran may be used as a model for viral vector delivery in malignant brain tumors.     

Multiple cerebral metastases: detectability with Gd-DTPA-enhanced MR imaging

Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.     

Glucose-receptor MR imaging of tumors: study in mice with PEGylated paramagnetic niosomes

PURPOSE: To evaluate a magnetic resonance (MR) imaging contrast agent for tumor detection based on paramagnetic nonionic vesicles (niosomes) bearing polyethylene glycol (PEG) and glucose conjugates for the targeting of overexpressed glucose receptors. MATERIALS AND METHODS: Four gadobenate dimeglumine-loaded niosome preparations including nonconjugated niosomes, niosomes bearing glucose conjugates (N-palmitoyl glucosamine [NPG]), niosomes bearing PEG 4400, and niosomes bearing both PEG and NPG were tested. In vitro cellular uptake was measured at electron paramagnetic resonance (EPR) after incubation with human prostate carcinoma, PC3, cells. In vivo distribution was studied at MR imaging 6, 12, and 24 hours after injection, with assessment of tumor, brain, liver, and muscle signal intensity (SI) in 49 mice bearing PC3 cells. Efficiency of targeted contrast agents was assessed with tumor-to-muscle contrast-to-noise ratio (CNR). Testing for differences was performed with analysis of variance followed by a posteriori Fisher test. RESULTS: In vitro, gadolinium could be detected at EPR only in cell pellets incubated with niosomes bearing glucose conjugates or niosomes bearing both glucose conjugates and PEG (4.9. 10(-15) and 4.5. 10(-15) mol gadolinium per PC3 cell). In vivo, marked predominant tumor enhancement was demonstrated 24 hours after injection of glycosylated PEG niosomes (P <.01); no significant differences were observed following injection of nonconjugated niosomes, glycosylated niosomes, or PEG 4400 niosomes. Twenty-four hours after injection, sole presence of NPG or PEG 4400 on the surface of the niosome led to higher tumor-to-muscle CNR than that observed after injection of nonconjugated niosomes (CNR of 3.3 +/- 0.7 [SD], 3.4 +/- 2.2, and 0 +/- 1.9). Combination of NPG and PEG led to even higher tumor-to-muscle CNR (6.3 +/- 2.2). CONCLUSION: Combination of PEG and glucose conjugates on the surface of niosomes significantly improved tumor targeting of an encapsulated paramagnetic agent assessed with MR imaging in a human carcinoma xenograft model.     

Clinical safety and efficacy of gadoteridol: a study in 411 patients with suspected intracranial and spinal disease

In this phase III study, 411 adult patients with suspected intracranial or spinal disease underwent magnetic resonance (MR) imaging before and after intravenous injection of 0.1 mmol/kg gadoteridol (gadolinium 1,4,7-tris [carboxymethyl]-10-[2'-hydroxypropyl]-1,4,7,10-tetraazacyclododecane+ ++). MR images were evaluated by a single unblinded reader at each of 27 sites; the diagnosis was confirmed with one of nine imaging or surgical procedures within 8 weeks before or after MR imaging. After injection, no clinically significant changes were noted in laboratory values, physical examination, or vital signs. Adverse clinical events possibly or probably associated with injection of gadoteridol were seen in 18 of 411 patients (4.4%); the most common were dysgeusia and mild nausea, and all abated without residual effects. MR images enhanced with gadoteridol in patients with confirmed disease provided more diagnostic information than unenhanced images in 128 of 175 brain examinations (73.1%) and 93 of 137 spinal examinations (67.9%). A change in diagnosis because of additional information from contrast-enhanced images was considered likely in 63 of 214 cranial and 54 of 161 spinal studies.     

Gd-DTPA-enhanced MR imaging in pediatric patients after brain tumor resection

A prospective study was conducted in 15 pediatric patients who had undergone resection of intracranial tumors. The object of the study was to determine the safety and efficacy of magnetic resonance (MR) imaging performed after the administration of gadolinium diethylenetriamine-pentaacetic acid (Gd-DTPA) in evaluating residual or recurrent tumor. Precontrast T1-weighted, intermediate, and T2-weighted images were obtained at a field strength of 1.5 T. Gd-DTPA was then injected intravenously in a dose of 0.1 mmol per kilogram of body weight. T1-weighted images were obtained within 5 minutes after the injection, intermediate and T2-weighted images were obtained 10 minutes after the injection, and T1-weighted images were obtained approximately 20 minutes after the injection. None of the patients experienced allergic reactions or other side effects. Physical examination findings and laboratory values were unchanged after the Gd-DTPA-enhanced examination. In six patients, contrast-enhanced images depicted tumor not suspected on nonenhanced images. In four other patients, enhanced images provided better definition of the tumor core. The images of one patient with a brain stem tumor showed no evidence of enhancement. Pre- and postcontrast images of three previously treated patients showed no evidence of tumor. Gd-DTPA appears to be a safe and effective contrast agent for MR imaging and provides a more accurate method of imaging in the follow-up of brain tumors in pediatric patients.     

Effect of contrast dose and field strength in the magnetic resonance detection of brain metastases

PURPOSE: To compare the diagnostic efficacy of a standard and cumulative triple dose of magnetic resonance (MR) imaging contrast agent in the evaluation of brain metastases using a high-field 3.0 T MR unit versus a standard field 1.5 T MR unit. METHODS: Twenty-two patients with suspected brain metastases were examined at both field strengths using identical postcontrast coronal 3D gradient echo with magnetization preparation, which was adjusted separately for each field strength. In both groups initially, iv injection of 0.1 mmol/kg body weight gadolinium chelate (gadodiamide) and thereafter, 0.2 mmol/kg body weight gadodiamide were administered. Subjective assessment of the images was performed independently by 3 neuroradiologists. Objective measurement of signal-to-noise and contrast-to-noise ratios was obtained. RESULTS: The subjective assessment of cumulative triple-dose 3.0 T images obtained the best results compared with other sequences, detecting 84 metastases, followed by 1.5 T cumulative triple-dose enhanced images with 81 brain metastases. The objective assessment confirmed those results, showing significantly higher signal-to-noise and contrast-to-noise ratios with 3.0 T than with 1.5 T. CONCLUSIONS: Cumulative triple-dose images of both field strengths were superior to standard field strengths. However, administration of gadodiamide contrast agent produces higher contrast between tumor and normal brain on 3.0 T than on 1.5 T, resulting in better detection of brain metastases and leptomeningeal involvement.     

Improved radioimmunolocalization of human tumor xenografts following subcutaneous delivery of monoclonal antibodies

The localization of a radiolabeled murine monoclonal antibody reactive with choriocarcinomas to human choriocarcinoma xenografts following intravenous and subcutaneous injection was evaluated by gamma scanning and tissue sampling. Tumor xenografts were established in the popliteal node region of athymic nude mice after repeated innoculations of the hind foot pads with BEWO choriocarcinoma cells. In dual label specific antibody studies, tumor/non tumor uptake ratios following subcutaneous (resulting in considerable intralymphatic uptake) injection of 131I-5F9.3 were significantly higher than those achieved post simultaneous intravenous injection of 125I-5F9.3. Double label experiments with 131I-5F9.3 and a nonspecific antibody, 125I-UPC-10, following subcutaneous injection, demonstrated that the high localization to popliteal region tumors was largely due to antibody specificity. Gamma scans following subcutaneous antibody administration of specific antibody to tumor bearing animals showed tumors soon after subcutaneous injection, at times earlier than those typically seen following intravenous delivery. Similar subcutaneous injections showed little normal nodal uptake in BALB/c control animals on gamma scans. No correlation was seen between tumor localization by specific antibody between the intravenous and intralymphatic routes, implying a difference in the mechanisms of tumor uptake of antibody by these two routes. The subcutaneous approach to antibody delivery offers advantages over intravenous delivery in tumors of human origin, including higher tumor/non tumor ratios and earlier imaging times. This was true even though these tumors were many times larger than normal lymph nodes. This subcutaneous delivery advantage should be exploitable in imaging nodal metastases of human tumors.     

Gadolinium-DTPA-dextran: a macromolecular MR blood pool contrast agent

RATIONALE AND OBJECTIVES: Magnetic resonance (MR) imaging blood pool agents offer numerous advantages for vascular and tumor imaging. The purpose of this study was to test gadolinium-diethylenetriaminepentaacetate-dextran ([Gd]DTPA-dextran) as a new water soluble macromolecular blood pool agent for MR imaging. MATERIALS AND METHODS: [Gd]DTPA-dextran (187 gadolinium atoms per dextran, molecular weight 165 kD, diameter 17.6 nm) was synthesized. Fifteen anesthetized New Zealand White rabbits with thigh VX2 tumors were scanned in a knee coil at 1.5T. Coronal 3D MR angiographic sequences were obtained before and at several time points up to 72 hours after the intravenous bolus injection of [Gd]DTPA-dextran providing gadolinium at either 0.05 (n = 4) or 0.1 mmol/kg (n = 8) or [Gd]DTPA-bismethylamide (BMA) providing gadolinium at 0.1 mmol/kg (n = 3). Time enhancement curves for aorta, cava, and tumor rim were compared by univariate General Linear Model. RESULTS: Contrast enhancement of cava and aorta relative to a water phantom were significantly greater at all time points after either dose of [Gd]DTPA-dextran than after [Gd]DTPA-BMA (P < 0.01). Tumor rim enhancement was less intense for either dose of [Gd]DTPA-dextran at peak than for [Gd]DTPA-BMA (P < 0.05). Tumor rim enhancement with both doses of [Gd]DTPA-dextran became equivalent to that of [Gd]DTPA-BMA at one hour and was greater at 24 hours (P < 0.05). CONCLUSION: [Gd]DTPA-dextran is a new macromolecular MR contrast agent that can be synthesized to carry a high density of gadolinium atoms without intra-molecular cross-linking. It provides significantly greater vascular residence time than a conventional gadolinium chelate and shows promise for MR blood pool imaging.     

Recurrent glomus tumors of fingertips: MR imaging evaluation

PURPOSE: To determine the magnetic resonance (MR) imaging findings in recurrent glomus tumors of the fingertips. MATERIALS AND METHODS: Twenty-four consecutive patients with recurrent pain after previous excision of a glomus tumor of the fingertip underwent MR imaging studies and surgery. T1-weighted spin-echo MR images were obtained in each patient before and after intravenous injection of contrast material; T2-weighted spin-echo and three-dimensional gradient-recalled echo images were also obtained. MR angiography was performed in four patients. Postsurgical histopathologic analysis revealed recurrent glomus tumors in 22 patients. Signal intensity, enhancement, and margins of the scar tissue and the recurrent tumors at MR were assessed. RESULTS: The postsurgical scars were depicted in 21 (88%) of 24 patients with all sequences but were best demonstrated on gradient-recalled echo MR images. Seven patients had undergone multiple surgical procedures and had extensive scar tissue and, in one case, a neuroma. In all patients, MR imaging revealed a nodule compatible with the diagnosis of a recurrent glomus tumor. In 13 (54%) of 24 patients, the nodule had typical features of a glomus tumor. In eight (33%) of 24 patients, the tumors had low signal intensity or isointensity compared with the nail bed on T2-weighted images. In six (25%) of 24 patients, the tumors had faint enhancement after intravenous gadolinium chelate administration. The margins of the tumors were blurred by scar tissue in nine of 24 cases. CONCLUSION: MR imaging can aid in the evaluation of recurrent glomus tumors.     

Neuroimaging in pediatric brain tumors: Gd-DTPA-enhanced, hemodynamic, and diffusion MR imaging compared with MR spectroscopic imaging

BACKGROUND AND PURPOSE: Gadolinium-enhanced MR images assist in defining tumor borders; however, the relation between tumor cell extent and contrast-enhanced regions is unclear. Our aim was to improve conventional neuroimaging of pediatric brain tumors with hemodynamic, diffusion, and spectroscopic MR imaging. METHODS: We performed conventional MR and MR spectroscopic imaging in 31 children with neuroglial brain tumors. Hemodynamic MR imaging was performed in 16 patients with a first-pass intravenous bolus of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA); apparent diffusion coefficients (ADCs) were measured in 12 patients. To account for multiple measurements in a patient, we used a nested analysis of variance. RESULTS: At MR spectroscopy, choline (Cho)-containing compounds (indicating tumor) and lipid levels (indicating necrosis) did not correlate with percent Gd-DTPA enhancement on MR images. Percent enhancement was positively correlated with relative cerebral blood volumes (rCBVs) (P =.05) and negatively correlated with ADCs (P <.001). Stepwise multiple linear regression revealed that rCBV (P =.008), ADC (P =.022), and lipid (P <.001) levels were significant independent predictors of percent enhancement. Tumor spectral patterns were detected in tumor regions and outside enhancing tumor beds in patients with clinical progression; these were confirmed at neuropathologic analysis. CONCLUSION: MR spectroscopic imaging improves the assessment of pediatric brain tumors by adding biochemical information regarding tumor involvement and by depicting residual or recurrent tumor outside the Gd-DTPA-enhanced tumor bed. rCBV and ADC mapping complemented MR spectroscopic imaging. We recommend the use of MR spectroscopic imaging in addition to conventional MR imaging in assessing pediatric brain tumors.     

Monitoring of irradiated brain metastases using MR perfusion imaging and 1H MR spectroscopy

PURPOSE. In follow-up examinations of irradiated brain metastases conventional contrast-enhanced morphological MR imaging is often unable to distinguish between transient radiation effects, radionecrosis,and tumor recurrence. To evaluate changes of relative cerebral blood flow (rCBF) in irradiated brain metastases arterial spin-labeling techniques (ASL) were applied and compared to the outcome of (1)H MR spectroscopy and spectroscopic imaging ((1)H MRS, SI). PATIENTS AND METHODS. In 2 patients follow-up examinations of irradiated brain metastases were performed on a 1.5-T tomograph (average single dose: 20 Gy/80% isodose). Relative CBF values of gray matter (GM), white matter (WM),and metastases (Met) were measured by means of the ASL techniques ITS-FAIR and Q2TIPS. (1)H MRS was performed with PRESS 1500/135. RESULTS. In both patients with initially hyperperfused metastases (Met/GM >1) the reduction of rCBF after stereotactic radiosurgery indicated response to treatment--even if the contrast-enhancing region increased--while increasing rCBF values indicated tumor progression. The findings were confirmed by (1)H MRS, SI and subsequent follow-up. CONCLUSION. The ASL techniques ITS-FAIR and Q2TIPS are able to monitor changes of rCBF in irradiated brain metastases. The two cases imply a possible role for ASL-MR perfusion imaging and (1)H MR spectroscopy in differentiating radiation effects from tumor progression.     

Intradural spinal metastases in pediatric patients with primary intracranial neoplasms: Gd-DTPA enhanced MR vs CT myelography

Recently, the application of intravenous gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) has been shown to improve the detection of intradural extramedullary spinal disease in adults. The ability of Gd-DTPA enhanced magnetic resonance (MR) to detect intradural extramedullary spinal metastases was studied in pediatric brain tumor patients. Spinal MR images before and after intravenous injection of Gd-DTPA were analyzed retrospectively in eight pediatric patients with known intracranial neoplasms and clinically suspected subarachnoid tumor seedings. Contrast enhanced spinal MR was compared with CT myelography in four of these patients. In our pediatric population Gd-DTPA enhanced images revealed tumor seeding not appreciable on noncontrast images. Although CT myelography has been the accepted standard investigation in the evaluation of suspected spinal metastases in children, we found that contrast enhanced MR is equal or superior in sensitivity to CT myelography. Spinal MR also provided information not obtainable via CT myelography. In the future, Gd-DTPA enhanced spinal MR should be considered in the initial evaluation of suspected subarachnoid spinal metastases in pediatric patients with known primary brain tumors.     

The effect of contrast dose,imaging time,and lesion size in the MR detection of intracerebral metastasis.

PURPOSETo evaluate the effect of MR contrast dose versus delayed imaging time on the detection of metastatic brain lesions based on lesion size.METHODSContrast MR examinations with gadoteridol were obtained in 45 patients with brain metastases. The patients were divided into two groups: 16 received cumulative standard dose (0.1 mmol/kg) and 29 received cumulative triple dose (0.3 mmol/kg). Both groups were evaluated at two dose levels (lower dose and higher dose) with two separate injections. Each patient received an initial bolus injection of either 0.05 (cumulative standard dose) or 0.1 (cumulative triple dose) mmol/kg of gadoteridol to reach the lower-dose level and underwent imaging immediately and 10 and 20 minutes later. Thirty minutes after injection, an additional bolus injection of 0.05 (cumulative standard dose) or 0.2 (cumulative triple dose) mmol/kg was administered to reach the cumulative higher-dose level (cumulative standard dose, 0.1 mmol/kg; cumulative triple dose, 0.3 mmol). Images were acquired immediately.RESULTSThere was no difference in the detection rate for lesions larger than 10 mm among T2-weighted, lower-dose immediate and delayed, or immediate higher-dose images in both study groups. Lesions smaller than 10 mm had improved detection with delayed imaging in both study groups; however, the immediate higher-dose studies still had the highest detection rate.CONCLUSIONIn the evaluation of small central nervous system metastases, either delayed imaging after the injection of standard contrast dose or higher contrast dose may improve their detection, and therefore affect clinical management. Higher contrast dose (cumulative triple dose) studies appear to be more effective than delayed imaging with standard dose.     

Improved radioimmunolocalization of human tumor xenografts following subcutaneous delivery of monoclonal antibodies

The localization of a radiolabeled murine monoclonal antibody reactive with choriocarcinomas to human choriocarcinoma xenografts following intravenous and subcutaneous injection was evaluated by gamma scanning and tissue sampling. Tumor xenografts were established in the popliteal node region of athymic nude mice after repeated innoculations of the hind foot pads with BEWO choriocarcinoma cells. In dual label specific antibody studies, tumor/non tumor uptake ratios following subcutaneous (resulting in considerable intralymphatic uptake) injection of ¹³¹I-5F9.3 were significantly higher than those achieved post simultaneous intravenous injection of ¹²⁵I-5F9.3. Double label experiments with ¹³¹I-5F9.3 and a nonspecific antibody, ¹²⁵I-UPC-10, following subcutaneous injection, demonstrated that the high localization to popliteal region tumors was largely due to antibody specificity. Gamma scans following subcutaneous antibody administration of specific antibody to tumor bearing animals showed tumors soon after subcutaneous injection, at times earlier than those typically seen following intravenous delivery. Similar subcutaneous injections showed little normal nodal uptake in BALB/c control animals on gamma scans. No correlation was seen between tumor localization by specific antibody between the intravenous and intralymphatic routes, implying a difference in the mechanisms of tumor uptake of antibody by these two routes. The subcutaneous approach to antibody delivery offers advantages over intravenous delivery in tumors of human origin, including higher tumor/non tumor ratios and earlier imaging times. This was true even though these tumors were many times larger than normal lymph nodes. This subcutaneous delivery advantage should be exploitable in imaging nodal metastases of human tumors.     

In vivo studies of Gd-DTPA-monoclonal antibody and gd-porphyrins: potential magnetic resonance imaging contrast agents for melanoma

New tumor-specific contrast agents for clinical imaging and therapy for cancer are required. To this end Gd-H (Gd-hematoporphyrin), Gd-TCP (Gd-tetra-carboranylmethoxyphenyl-porphyrin), Gd-DTPA-WM53, and Gd-DTPA-9.2.27 were synthesized and administered by systemic injection to nude mice with human melanoma (MM-138) xenografts. The biodistribution T1 relaxation times and magnetic resonance (MR) image signal enhancement of the contrast agents are presented for the first time and compared for each group of five mice. A change (20%) in T1 relaxation times of water in human melanoma tumor xenografts was revealed 24 hours after injection of the labeled immunoconjugate Gd-DTPA-9.2.27. The percent of injected antibody or gadolinium that localized to the tumor was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to be approximately 35%. A higher concentration of gadolinium was achieved compared with nonspecific compounds, indicating selective delivery of Gd-DTPA-9.2.27 to the melanoma xenografts. Porphyrin-based contrast agents (Gd-H and Gd-TCP) also showed significant uptake in melanomas. The uptake of Gd-TCP by the tumor was sufficient to deliver boron atoms into the tumor, making possible dual use for both MR imaging (MRI) and boron neutron capture therapy (BNCT). The linear relationship found between the paramagnetic contribution to the relaxation rates and contrast agent concentration allows quantitative studies of paramagnetic contrast agent uptake.     

Early MR lymphography with gadofluorine M in rabbits

PURPOSE: To investigate the dose and time dependency of gadofluorine M for lymph node imaging and the detection of lymph node metastases in an animal model and to compare gadofluorine M with Gadomer (both, Schering, Berlin, Germany) for lymph node enhancement. MATERIALS AND METHODS: Enhancement of popliteal and iliac lymph nodes was studied in VX2 tumor-bearing rabbits before injection and at 5-120 minutes and 24 hours after intravenous bolus injection of 0.025, 0.05, and 0.1 mmol gadolinium per kilogram of body weight gadofluorine M (six rabbits) or 0.5 mmol/kg Gadomer (eight rabbits). Effects of treatment and time point at enhancement were evaluated with repeated measures analysis of variance. Means were separated with all-pairs comparison with Tukey-Kramer adjustment. After 1.5-T magnetic resonance (MR) imaging, lymph nodes were removed, and prepared sections were stained with hematoxylin-eosin for microscopic examination. RESULTS: MR images in VX2 tumor-bearing rabbits revealed rapid and strong signal intensity increase in the functional lymph node tissue by 15 minutes after intravenous injection of gadofluorine M. Maximum enhancement of 165%-309% was observed 60-90 minutes after injection (enhancement with 0.05 and 0.1 mmol/kg significantly different from that with 0.025 mmol/kg, P < or =.05). Metastatic tissue showed only slight enhancement at early time points, resulting in high-contrast differentiation between functional and metastatic tissue. Intravenous injection of the blood-pool agent Gadomer induced only short and inhomogeneous lymph node enhancement (enhancement significantly lower [P < or =.05] than that with gadofluorine M). CONCLUSION: Findings in the study showed that gadofluorine M produces rapid lymph node accumulation. Diagnosis of lymph node metastases was shown with intravenous injection of gadofluorine M with a minimum effective diagnostic dose of 0.025 mmol/kg.     

Gadolinium-DTPA in MR imaging of glioblastomas and intracranial metastases

In 14 patients with the diagnosis of glioblastoma (n = 7) or intracranial metastases (n = 7), magnetic resonance (MR) imaging was performed using a variety of spin-echo (SE) pulse sequences before and after intravenous injection of 0.1 mmol gadolinium-DTPA (Gd-DTPA) per kilogram of body weight. In 10 patients, tumor tissue could not be adequately differentiated from perifocal edema on unenhanced scans with any of the applied pulse sequences. In four cases of intracranial metastases, poor differentiation between tumor and perifocal edema was possible in T2-weighted (SE 1600/70 and SE 1600/105) unenhanced scans. After administration of Gd-DTPA, tumor tissue showed marked contrast enhancement, and tumor delineation was consistently possible on SE 800/35 images. Tumor tissue could be differentiated from perifocal edema on SE 800/70 scans. Gd-DTPA is likely to increase the potential of MR imaging and refine the evaluation of glioblastomas and intracerebral metastases.     

Radiation-induced brachial plexopathy: MR imaging

 Objective. To describe the MR imaging appearance of radiation-induced brachial plexopathy. Design. MR imaging was performed in two patients with the clinical diagnosis of radiation-induced brachial plexopathy and in one with surgically proven radiation fibrosis of the brachial plexus. Patients. Three patients who had had radiation therapy to the axilla and supraclavicular region (two with breast carcinoma and one with Hodgkin’s lymphoma) presented with symptoms in the arm and hand. To exclude metastases or tumor recurrence MR imaging was performed. Results and conclusion. In one patient, fibrosis showing low signal intensity was found, while in two patients high signal intensity fibrosis surrounding the brachial plexus was found on the T2-weighted images. In one case gadolinium enhancement of the fibrosis was seen 21 years after radiation therapy. It is concluded that radiation-induced brachial plexopathy can have different MR imaging appearances. We found that radiation fibrosis can have both low or high signal intensities on T2-weighted images, and that fibrosis can enhance even 21 years after radiation therapy.     

Three subsequent single doses of gadolinium chelate for brain MR imaging in multiple sclerosis

BACKGROUND AND PURPOSE: A triple-dose (TD) of gadolinium chelate is highly sensitive approach for detecting lesion activity in multiple sclerosis (MS). However, individual TD injections do not provide data on the severity of the pathologic process in a population of lesions, and its clinical use is limited by the cost-benefit considerations. Our aim was to determine whether the use of three subsequent single doses (SD) of a gadolinium chelate in brain MR imaging is useful in detecting MS lesions with different patterns of enhancement. METHODS: In 10 patients, T1-weighted spin-echo images were acquired before and after three intravenous administrations of 0.1 mmol/kg of gadodiamide. RESULTS: In all patients, SD images showed six enhancing lesions; double-dose (DD) images, 13; and TD images, 22. Differences between SD and TD and between DD and TD were significant (P <.018). Six lesions (27%) enhanced with all the three doses; seven (32%), with both DD and TD; and nine (41%), with only TD. Proportions of patients with at least one enhancing lesion were, for SD, four of 10; DD, seven of 10; and TD, nine of 10. In defining active disease in these nine patients, we needed only 19 SDs versus the 30 SDs that would have been needed if individual TD injections were used. CONCLUSION: With three subsequent SD injections, the number of enhancing lesions progressively increases. This approach allows the distinction of three levels of enhancement, and it reduces the amount of contrast agent needed to distinguish patients with active MS from those with nonactive MS.