Breath-hold gadolinium-enhanced MR angiography of the major vessels at 1.0 T: dose-response findings and angiographic correlation

PURPOSE: To find the appropriate contrast agent dose for gadolinium-enhanced magnetic resonance (MR) angiography by using individual measurement of contrast agent transit times in a randomized study. MATERIALS AND METHODS: A total of 34 patients with disease of the aorta or its major branches or both were randomly assigned to receive a dose of 0.1, 0.2, or 0.3 mmol of gadopentetate dimeglumine per kilogram of body weight. Initially, contrast agent transit times were measured with use of a turbo fast-low-angle-shot sequence. Subsequently, a three-dimensional fast imaging with steady-state precession sequence (7.3-msec repetition time, 2.8-msec echo time) was used for breath-hold MR angiography. Gadopentetate dimeglumine was injected with an MR-compatible power injector. Efficacy was evaluated by measurement of vessel enhancement and by clinical correlation of MR angiograms with x-ray angiograms. RESULTS: Evaluation of contrast agent transit time was possible in all patients with the test doses, which provided contrast-enhanced MR angiograms of constant quality. Neither vessel enhancement nor diagnostic information was significantly different across the these study groups. CONCLUSION: The clinical gadolinium dose of 0.1 mmol/kg is sufficient for diagnostic assessment of the aorta and its major branches at contrast-enhanced MR angiography. High-dose studies appear not to be required for these large vessels.     

Measurement of cerebral blood volume via the relaxing effect of low-dose gadopentetate dimeglumine during bolus transit

PURPOSE: To quantify regional cerebral blood volume (rCBV) on the basis of the enhancement of blood proton relaxation rates after intravenous administration of gadopentetate dimeglumine. METHODS: A series of sequential MR images on one section was recorded during bolus transit with a standard fast low-angle shot sequence. The signal-intensity curves were converted into corresponding concentration-time curves from which rCBV images were calculated. RESULTS: The functional parameter images of rCBV were calculated pixel-by-pixel for two patients who had received a 1-second bolus injection of 1 mmol of gadopentetate dimeglumine. In a larger series of 62 patients, a mean blood volume of 4.6 +/- 1.6 vol% was determined for normal brain tissue. CONCLUSIONS: The relaxing effect of a contrast agent can be used to determine blood volume quantitatively. The results are in agreement with those obtained by nuclear medicine techniques. The proposed method requires no special hardware, and can thus be implemented on clinical MR scanners.     

Enhancement of joint fluid with intravenously administered gadopentetate dimeglumine: technique, rationale, and implications

This study reports findings on joint fluid enhancement after intravenous administration of gadopentetate dimeglumine. Ten subjects were studied: two asymptomatic volunteers and eight patients with suspected meniscal tears. The subjects underwent imaging at 1.5 T before, immediately after, and 42-60 minutes after intravenous administration of gadopentetate dimeglumine. The rate of fluid enhancement was assessed in three subjects, and the effects of exercise were studied. All subjects exhibited enhancement of joint fluid. Mean fluid enhancement for patients was 137% on initial and 262% on delayed images obtained after exercise. Exercise increased the rate and degree of fluid enhancement and distributed contrast material uniformly throughout the joint. The arthrographic effect of the fluid enhancement increased the number of perceived cartilage defects. This study documents enhancement of joint fluid in healthy subjects and in those with effusions. The arthrographic effect may provide a more convenient alternative to intraarticular injection of gadopentetate dimeglumine for MR arthrography.     

Predictive value of antepartum ultrasound examination for anomalies in twin gestations

RATIONALE AND OBJECTIVES: We investigated the potential of manganese (III) mesoporphyrin (Mn-mesoporphyrin) as a hepatobiliary contrast agent for magnetic resonance (MR) imaging in rabbits given VX-2 carcinoma liver implants. METHODS: Rabbits given VX-2 carcinoma liver implants (n = 8) were imaged before and after the intravenous (i.v.) administration of 0.04 mmol/kg Mn-mesoporphyrin. MR images were correlated with gross-specimen cross-sections. The distribution of Mn in various tissues following i.v. administration of 0.04 mmol/kg Mn-mesoporphyrin was determined using atomic absorption analysis. A standard panel of serum chemistries was followed over 7 days in six rabbits following this same dose of Mn-mesoporphyrin and compared with chemistries from two control rabbits. RESULTS: I.v. administration of 0.04 mmol/kg (25 mg/kg) Mn-mesoporphyrin resulted in improvement of tumor-to-liver contrast, with enhancement of normal liver (99.7 +/- 14.7%) and the gallbladder (442 +/- 116%), but not VX-2 tumor tissue (14.8 +/- 13.9%), (n = 8, p = .05). Analysis of tissue Mn levels 100 min after i.v. Mn-mesoporphyrin injection demonstrated preferential distribution of Mn to normal liver tissue (57.8 +/- 15.3 micrograms Mn/g) compared with VX-2 tumor (4.28 +/- 1.48 micrograms Mn/g). No significant change was found in the serum chemistries of six normal rabbits over a 7-day period after the i.v. administration of 0.04 mmol/kg Mn-mesoporphyrin. CONCLUSION: I.v. Mn-mesoporphyrin improved lesion-to-liver contrast because of preferential distribution of Mn-mesoporphyrin to normal liver parenchyma and bile.     

Magnetic resonance urography by breath-hold contrast-enhanced three-dimensional FISP

The purpose of this study was to present our initial experience with contrast-enhanced MR urography with a breath-hold three-dimensional imaging technique. We performed MR urographic studies in two pigs (four studies) and five human subjects using gadopentetate dimeglumine. The FISP sequence we used was the same as the one used for contrast-enhanced three-dimensional breath-hold angiography. MR three-dimensional urograms were obtained 7-24 minutes after the contrast injection with a dose as low as .03 mmol/kg. The calyces, renal pelves, and ureters were very well visualized. Three-dimensional MR urography can be acquired within a single breath-hold after administration of gadolinium chelates. This technique could become part of a protocol that could potentially lead to a single comprehensive diagnostic workup for suspected ureteral obstruction and gross hematuria.     

MRT of experimental liver abscesses: a comparison of a new blood pool contrast medium with gadolinium-DTPA in animal experiments

PURPOSE: In an experimental pyogenic liver abscess model, the signal intensities were compared intraindividually and interindividually after the application of a new blood pool contrast agent, 24-gadolinium-DTPA (diethylenetriamine-pentaacetic acid) cascade polymer, and after the application of gadopentetate dimeglumine. METHODS: In 20 rabbits with experimentally induced liver abscesses, the relative signal intensities of the liver, abscess centre, abscess wall and portal vein were assessed before and between 30 seconds and 60 minutes after injection of a 25 mumol/kg dose of gadolinium polymer and of 100 mumol/kg of gadolinium-DTPA, respectively. Measurements were performed at 1.5 Tesla, using a head coil and a Flash-2-D sequence. RESULTS: The interindividual comparison (unpaired T-test, p < 0.05) yielded significant differences of the relative signal intensities of the abscess centre (at any time point after contrast-media application), abscess wall (between 15 and 60 minutes after contrast media application), and portal vein (between 30 seconds and 7.5 minutes after contrast media application). The interindividual comparison showed a significantly higher abscess centre-liver contrast (between 30 seconds and 12.5 minutes after contrast media application) and a significantly higher abscess wall-centre contrast (between two and 7.5 minutes after contrast media application) after the application of gadolinium polymer compared with gadopentetate dimeglumine. CONCLUSION: In this animal model, the higher abscess centre-liver contrast after the application of gadolinium polymer was the basis for a better and prolonged visibility of the abscesses, as compared with images acquired after injection of gadopentetate dimeglumine.     

Gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral arteries: evaluation of a multistation examination using two gadopentetate dimeglumine infusions

OBJECTIVE: Three-dimensional gadolinium-enhanced MR angiography is a rapid and accurate method that can at times image only a limited amount of anatomy during an examination. We evaluated a technique that doubled the anatomy imaged by obtaining two separate gadolinium-enhanced MR angiograms during a single examination. MATERIALS AND METHODS: Twenty-three patients referred for MR evaluation of aortic or peripheral vascular disease underwent two successive gadolinium-enhanced three-dimensional MR angiographic examinations during a single MR examination. An injection of 15 ml of gadopentetate dimeglumine was used for the first MR angiogram, and 25 ml was used for the second MR angiogram. The angiograms were quantitatively and qualitatively evaluated to determine the effect of residual gadolinium from the initial MR angiogram on the second angiogram. RESULTS: The two studies depicted either the entire aorta to the femoral arteries (n = 10) or the distal aorta to the popliteal arteries (n = 13). The total mean gadolinium dose was 0.245 mmol/kg per patient. An average of 15 min elapsed between injections. The value of arterial signal-to-noise ratio (mean, 48.8 versus 56.4) and artery-to-vein contrast-to-noise ratio (mean, 45.5 versus 49.0) increased between the first and second angiograms, respectively. Residual gadolinium elevated the values for venous signal-to-noise ratio (mean, 2.3 versus 7.2) and background-to-muscle signal-to-noise ratio (mean, 5.5 versus 10.1) on the second MR angiogram. Qualitative evaluation by three observers showed no significant differences in diagnostic usefulness or overall image quality between the first and second MR angiograms. CONCLUSION: The use of two low-dose gadolinium-enhanced three-dimensional MR angiograms during a single examination is a feasible approach to increase anatomic coverage when performing gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral vessels. Although background enhancement is slightly elevated on the second angiogram, such enhancement does not significantly change diagnostic usefulness or overall image quality.     

CO2 and gadopentetate dimeglumine as alternative contrast agents for malfunctioning dialysis grafts and fistulas

BACKGROUND: Hemodialysis grafts and native fistulas are frequently evaluated angiographically utilizing iodinated contrast material to determine the cause of malfunction. Occasionally, patients are not able to receive iodinated contrast material due to a history of previous severe allergic reaction or concern that iodinated contrast material could worsen renal function requiring premature initiation of permanent dialysis. We set out to test the feasibility of gadopentetate dimeglumine as an alternative contrast agent in conjunction with carbon dioxide (CO2) angiography in the evaluation and treatment of hemodialysis grafts and native fistulas in patients who have a contraindication to iodinated contrast material. METHODS: Six patients with a malfunctioning hemodialysis graft and native fistula were evaluated. Four patients were successfully evaluated using carbon dioxide and gadopentetate dimeglumine. Two additional patients underwent balloon angioplasty using gadopentetate dimeglumine alone as the alternative contrast agent. RESULTS: All six patients successfully were evaluated and treated using gadopentetate dimeglumine either alone or as a supplement to CO2 angiography. Five of these patients had lesions successfully treated using gadopentetate dimeglumine alone or in combination with CO2 as the angiographic contrast agents. One patient underwent a successful diagnostic angiogram using gadopentetate dimeglumine and CO2 as alternative contrast agents and was subsequently treated with surgical revision. The gadopentetate dimeglumine angiograms identified the arterial anastomosis and more clearly identified stenotic lesions and venous outflow anatomy compared to carbon dioxide angiograms. CONCLUSION: Gadopentetate dimeglumine is useful as an alternative contrast agent in conjunction with CO2 in patients with malfunctioning hemodialysis grafts and fistulas, who have a contraindication to the administration of iodinated contrast material.     

Motile properties of vimentin intermediate filament networks in living cells

PURPOSE: To evaluate the clinical utility and morphologic accuracy of gadolinium-enhanced excretory magnetic resonance (MR) urography after low-dose diuretic injection and to correlate the results with those of conventional urography. MATERIALS AND METHODS: In 71 patients with urologic symptoms, excretory MR urography was performed after intravenous injection of 5-10 mg furosemide and, 30-60 seconds later, 0.1 mmol of gadopentetate dimeglumine per kilogram of body weight. The MR urograms were interpreted by three radiologists, who were blinded to the clinical outcome, and subsequently compared with conventional urograms. RESULTS: Injection of furosemide before contrast material led to rapid, uniform gadolinium distribution inside a sufficiently distended collecting system such that there was no excessive concentration of gadolinium in the urine. In patients with normal or moderately reduced excretory function, this effect allowed complete visualization of the urinary tract within 5-20 minutes of contrast material injection while minimizing gadolinium-related endoluminal T2* effects. The clinical course helped verify almost all MR urographic results. The MR urographic technique was significantly superior to conventional urography in the assessment of the ureters and bladder (P < .0001). Delineation of small caliceal abnormalities is still problematic. The best depiction of the pelvicaliceal system was obtained with fat-suppressed MR imaging, although it was still slightly inferior to conventional urography (P < .05). CONCLUSION: Gadolinium-enhanced excretory MR urography performed after low-dose diuretic injection is a promising and accurate alternative to conventional excretory urography for imaging the morphology of the urinary tract.     

Evaluation of the prostate and prostatic carcinoma with gadolinium-enhanced endorectal coil MR imaging

Thirteen patients who underwent subsequent radical prostatectomy for prostate cancer were studied with spin-density-T2-weighted and gadolinium-enhanced and unenhanced T1-weighted magnetic resonance (MR) imaging performed with an endorectal surface coil. With gadopentetate dimeglumine, the central gland showed inhomogeneous enhancement due to benign hyperplasia, whereas the peripheral zone demonstrated more uniform and less intense enhancement. With the T1-weighted sequence, depiction of the zonal anatomy, prostate capsule, surgical capsule, fibromuscular stroma, and periprostatic venous plexus was better with contrast enhancement, but these were best demonstrated on T2-weighted images. The trend was similar for prostatic tumor extent and capsular integrity. The seminal vesicles had a septal enhancement pattern and in several patients were best evaluated with enhanced T1-weighted images. These findings suggest that gadopentetate dimeglumine is not warranted for routine use in endorectal MR imaging of the prostate but may be useful for evaluation of the seminal vesicles in selected patients.     

Neurotoxic potential of gadodiamide after injection into the lateral cerebral ventricle of rats

PURPOSE: Results of a previous report showed that, if administered by intraventricular injection to access tissue normally protected by the blood-brain barrier, gadopentetate dimeglumine produced acute excitation, persistent ataxia, and widespread brain lesions in rats at 5-micromol/g brain but not at 3.8-micromol/g brain. The present study using gadodiamide was undertaken to see whether the effects were agent-specific. METHODS: Rats, surgically prepared with a lateral ventricular cannula, were administered a slow injection at 2 microL/min of gadodiamide into the lateral ventricle, and behavioral and neuropathologic changes were noted. RESULTS: Both gadodiamide and gadopentetate dimeglumine produced focal and generalized myoclonus over several hours. Gadodiamide did not produce the medium-term tremor or persistent ataxia seen after treatment with gadopentetate dimeglumine. Neuropathologic changes developed over 1 to 3 days and took three distinct forms: vacuolated thalamic lesions closely resembling those produced by gadopentetate dimeglumine; small but similar vacuolated symmetrical caudate lesions not produced by gadopentetate dimeglumine; and severe swelling and astrocytic hypertrophy and hyperplasia in the cerebellar vermis, again not produced by gadopentetate dimeglumine. Unlike gadopentetate dimeglumine, gadodiamide produced no spinal cord lesions. The cerebellar changes were seen at 1.25-micromol/g brain and above, behavioral changes at 2.5-micromol/g brain and above, and thalamic and caudate lesions at 10-micromol/g brain, the maximal dose used. Markedly reducing the rate of injecting the same volume over 28 hours prevented the acute excitation but did not reduce the severity of the morphologic effects. CONCLUSION: The acute excitatory effects of high intraventricular doses of gadopentetate dimeglumine and gadodiamide are similar and appear to be attributable to local action at the infusion site, but differences exist between the two agents in the character and topography of the distant morphologic changes. The cerebellum was the brain area most sensitive to gadodiamide in this experimental model. It is unlikely that gadodiamide would gain access to the brain at these tissue doses when used intravenously for conventional clinical imaging, but our experimental model suggested that it had some unexpectedly specific neuropathologic potential.     

Contrast-enhanced MR "magnetization transfer technique". Improved tumor contrast, delineation and visibility of intracranial malignant gliomas and metastases in radiosurgical treatment planning

AIMS: To improve tumor conspicuity and delineation on contrast-enhanced T1-weighted MR images with and without magnetization transfer (MT) contrast as a strategy to improve the macroscopic boost volume definition in the planning process of radiosurgery in patients with high grade gliomas or metastatic brain lesions. PATIENTS AND METHODS: Thirty-two patients (mean age 47 years) with histologically proven or suspected high grade glioma (n = 12) or metastatic brain lesions (n = 20) were prospectively examined by MR imaging. After the administration of gadolinium dimeglumine (0.1 mmol/kg body weight) the lesions were imaged with a T1-weighted MT-fast low angle shot (FLASH) pulse sequence and with a conventional T1-weighted SE sequence without MT saturation. RESULTS: The mean CNR of enhancing lesions on T1-weighted MT-FLASH was 15 +/- 5 compared to 11 +/- 4 on SE images, representing a significant (p < .01) improvement. The mean tumor diameter of malignant gliomas was significantly (p < .01) larger measured on T1-weighted MT-FLASH images compared to those obtained from T1-weighted SE images and were comparable for metastatic lesions. Lesion conspicuity and delineation were improved in 50% of patients with high grade gliomas and in 35% of patients with brain metastases. Lesion conspicuity was markedly improved in the posterior fossa. Additional contrast enhancing lesions were detected in 10% of patients with metastases on MT-FLASH images. CONCLUSIONS: It is concluded that contrast-enhanced MT-FLASH images may improve lesion detection and delineation in the planning process of radiosurgery in patients with intracranial high grade gliomas or metastases or even alter the treatment approach.     

Primary central nervous system lymphoma in a child with acute B-cell lymphoblastic leukaemia: consecutive Epstein-Barr virus-related malignancies

OBJECTIVE: The aim of the study was to evaluate the optimization of injection rates with an automatic power injector versus manual injection for contrast-enhanced breath-hold three-dimensional (3D) MR angiography of the abdominal aorta and its branches. SUBJECTS AND METHODS: In a prospective study, 50 patients underwent breath-hold 3D MR angiography (5/2 [TR/TE]; flip angle, 30 degrees) of the abdominal vessels on a 1.5-T system. Each patient received 0.15 mmol/kg of gadopentetate dimeglumine. All patients were randomly assigned to one of five equally sized groups. The contrast bolus was injected manually in group 1, always by the same investigator, who tried to perform a steady injection rate of 2 ml/sec. An automatic injector was used in groups 2-5 with injection flow rates of 0.5 ml/sec, 2 ml/sec, 4 ml/sec, and 6 ml/sec. The start of the MR sequence was tailored individually to the applied volume of contrast material after determination of circulation times by a test bolus. We measured the signal-to-noise and contrast-to-noise ratios as well as the relative vascular enhancement. The visualization of different abdominal vessel segments was independently ranked on a scale of 1-5 (1 = not visible; 5 = excellent visualization) by three reviewers who were unaware of the applied contrast material injection rate. RESULTS: The signal-to-noise and contrast-to-noise ratios of groups 3 and 4 (2 ml/sec and 4 ml/sec, respectively) were significantly (p < .05) higher than the ratios of groups 1, 2, and 5. The average relative vascular enhancement of groups 3 and 4 was significantly higher (p < .05) than the enhancement of all other groups. The contrast bolus applied with a faster injection rate (group 5) did not cover large parts of the K-space, resulting in increased blurring of the vessel contours. The subjective evaluation of large and small diameter vessels showed significantly better results in groups 3 and 4 than in groups 1, 2, and 5. CONCLUSION: The use of an automatic MR power injector proved superior to manual injection of contrast material. The optimal injection rate was 2 ml/sec for 3D breath-hold MR angiography of the abdominal vessels.     

Gadolinium-enhancement characteristics of magnetic resonance imaging in distinguishing herniated intervertebral disc versus scar in dogs

STUDY DESIGN: This study is an experimental investigation on the gadolinium contrast magnetic resonance imaging (MRI) in distinguishing sequestered disc fragment versus scar in dogs. The conspicousness of the disc fragment and signal intensities of the disc fragment and laminectomy scar were evaluated using gadolinium-enhanced MRI and histology. OBJECTIVES: This study investigated the effects of timing of gadolinium injections, gadolinium doses, and aging of scar or disc on the enhancement characteristics and conspicuousness of disc fragment in MRI. SUMMARY OF BACKGROUND DATA: Contrast-enhanced MRI has been frequently used as a procedure to evaluate patients with suspected recurrent herniated discs. In contrast-enhanced MRI, the postoperative scar tissue enhances to a greater extent than disc fragments. Previous reports suggest different contrast enhancement characteristics of scar depending on doses, timing of gadolinium, or maturity of scar. There are different compounds of gadolinium agents and different doses are becoming available. There is no previous report on the evaluation of gadolinium enhancement characteristics in dogs with concurrent herniated disc and scar. METHODS: Six conditioned Beagle dogs underwent hemilaminectomies and discectomies at the L3-L4 level. An autogenous disc fragment was obtained from the intervertebral disc of the tail. This disc fragment was placed anterolateral to the thecal sac, simulating a sequestered disc herniation. Three control animals underwent hemilaminectomies and discectomies alone. Each dog underwent MRI on a 1.5 Tesla scanner (3.0 mm slice in sagittal and axial projections with TR 500, TE 30 msec and high dose 0.3 mmol/kg of gadoteridol). Images were obtained at 15 days, 30 days, 60 days, and 90 days after surgery. At each imaging session, contrast enhancement was measured at 2 minutes, 25 minutes, and 45 minutes after gadolinium injection for kinematic analysis. Two animals at a time were killed on 30 days, 60 days, and 90 days postoperatively. Magnetic resonance imaging was done with conventional low dose 0.1 mmol/kg of gadopentetate at 15 days and before death. RESULTS: Results revealed that the difference of enhancement between disc and the scar and therefore conspicuousness of disc fragment was greater on 2-23-minute images as compared with 45- minute images, and the distinction decreased with aging of the scar. The high dose contrast-enhanced MRI increased signal intensities for both disc and scar. Conspicuousness of disc fragment seemed to be better with the high-dose gadolinium compound. CONCLUSIONS: In conclusion, contrast enhancement characteristics in MRI may depend on the timing of MRI after gadolinium injection, doses of gadolinium, and aging of scar or disc.     

Comparative signal intensity measurements in dynamic gadolinium-enhanced MR mammography

Increases in signal intensity enhancement were measured in defined regions of interest (ROIs) to allow distinction between malignant and benign tumors with dynamic gadolinium-enhanced magnetic resonance (MR) mammography. Twenty patients with palpable breast lesions (15 malignant, five benign) underwent MR mammography. The dynamic gradient-echo sequence was performed with intravenous bolus injection of gadopentetate dimeglumine and consisted of 25 images with a time resolution of 30 seconds. Contrast enhancement was calculated by comparing user-defined ROIs on pre- and postcontrast images. An increase in signal intensity of 70% or more on the 1-minute postcontrast image was used as the criterion of malignancy. MR mammographic results correlated with histopathologic findings in all patients when the defined ROI was in the most enhancing part of the tumor. For the ROI in areas of submaximal enhancement or when the ROI surrounded the whole lesion, only five and nine tumors, respectively, fulfilled the malignancy criterion. All malignant tumors showed large variations in signal intensity enhancement that depended on the position of the ROI in the tumor. Dynamic, gadolinium-enhanced MR mammography allows distinction of benign from malignant breast tumors when the selected ROI is in the most enhancing part of the lesion.     

Differential expression of extracellular matrix remodeling genes in a murine model of bleomycin-induced pulmonary fibrosis

PURPOSE: To prospectively analyze the value of fast, dynamic, subtraction magnetic resonance (MR) imaging in the characterization of musculoskeletal tumors. MATERIALS AND METHODS: In 175 consecutive patients with a musculoskeletal mass, dynamic contrast-enhanced subtraction MR imaging was performed after administration of 0.1 mmol per kilogram of body weight gadopentetate dimeglumine or gadoteridol. A turbo gradient-echo technique was used, with a temporal resolution of 1-3 seconds. The interval between arterial and early tumor enhancement, the pattern (peripheral or diffuse) of enhancement, and the progression of tumor enhancement, as visualized on time-signal intensity curves, were assessed. MR enhancement features were related to the histopathologic diagnoses. RESULTS: Differentiation of benign from malignant soft-tissue masses was possible with a sensitivity of 91% and specificity of 72% based on start of enhancement, a sensitivity of 73% and specificity of 97% based on peripheral or diffuse enhancement, and a sensitivity of 86% and specificity of 81% based on progression of enhancement. Benign bone tumors could not be accurately differentiated from malignant bone tumors on the basis of the three defined parameters (sensitivity, 63%-76%; specificity, 50%-76%). CONCLUSION: Dynamic, contract-enhanced, subtraction MR images may be useful to differentiate malignant from benign soft-tissue masses.     

Effect of molecular weight on the diffusion of contrast media into cartilage

STUDY DESIGN: A comparison of contrast enhancement in the intervertebral disc from two magnetic resonance imaging contrast media in experimental animals. OBJECTIVES: To test the effect of molecular weight on the diffusion of ionic contrast media into the intervertebral disc. SUMMARY OF BACKGROUND DATA: Intravenously administered gadopentetate diffuses similarly into the fibrocartilage of intervertebral discs and herniated disc fragments. Differentiation between recurrent disc fragments and scar tissue via magnetic resonance imaging is optimized by using contrast media, which result in different contrast enhancement of these two tissues. Contrast media of higher molecular weight diffuse more slowly into cartilage; hypothetically, therefore, such media will produce better contrast between scar tissue and recurrent disc fragments. METHODS: Gadopentetate (molecular weight 546) or gadolinium-polylysine (molecular weight 40,000) was injected intravenously into rabbits. The signal intensities of intervertebral disc and muscle tissue were recorded by magnetic resonance imaging at baseline and at pre-determined intervals for 2 hours after injection of the contrast medium. Contrast enhancement in these tissues was calculated in each animal for each contrast medium, and differences in enhancement were tested for significance by a growth-curve model. RESULTS: Contrast enhancement in the intervertebral disc was significantly less with gadolinium-polylysine than with gadopentetate. In muscle, no significant difference between the two media was observed. CONCLUSIONS: Molecular weight affects the diffusion of paramagnetic contrast media into the intervertebral disc. Contrast media of a high molecular weight may produce better contrast between recurrent herniated disc fragments and scar tissue than contrast media of lower molecular weight. This possibility should be rested in further studies.     

A comparison of two MR hepatobiliary gadolinium chelates: Gd-BOPTA and Gd-EOB-DTPA

PURPOSE: Two gadolinium chelates with partial hepatobiliary excretion, Gd-BOPTA and Gd-EOB-DTPA, and one gadolinium chelate with exclusively renal excretion, Gd-HP-DO3A, were compared on MRI at 1.5 T. The time course of enhancement for normal liver, gallbladder, spleen, kidney, and muscle was specifically examined in the rhesus monkey. METHOD: Four animals were evaluated with each agent for a total of 12 MR studies. Breath-hold and non-breath-hold T1 weighted scans were acquired prior to and 1, 2, 3, 4, 5, 15, 30, 45, 60, 75, and 90 min after intravenous contrast medium injection. The same contrast dose, 0.1 mmol/kg, was used for all studies. Images were analyzed by region-of interest measurements. RESULTS: Both hepatobiliary gadolinium chelates achieved sustained enhancement of normal liver parenchyma, superior in magnitude to that following Gd-HP-DO3A injection. On sans 45-90 min following injection, liver enhancement with Gd-BOPTA was superior to that with Gd-EOB-DTPA. This difference was, however, not statistically significant. Liver enhancement decreased more rapidly on delayed scans with Gd-EOB-DTPA than with Gd-Bopta, a result that was statistically significant. Excretion of contrast agent into the gallbladder was noted with both hepatobiliary agents but not with Gd-HP-DO3A. CONCLUSION: Enhancement of normal liver parenchyma peaks at a later time after injection with Gd-BOPTA than with Gd-EOB-DTPA. However, the maximum percent enhancement is comparable when (as in the current evaluation) the two agents are compared at the same dose (0.1 mmol/kg). This finding supports the choice of optimal imaging time post contrast agent administration (for delayed scans) in clinical trials of 20-45 min post injection with Gd-EOB-DTPA and 60-120 min post injection with Gd-BOPTA.     

Ligaments of the ankle: normal anatomy with MR arthrography

PURPOSE: Our purpose was to define the normal MR arthrographic anatomy of ankle ligaments. METHOD: Prior to injection of intraarticular gadolinium in cadaveric ankle joints, proton density and T2-weighted images were obtained to assess the integrity of the ligaments and tendons as well as the amount of preexisting joint effusion. Following injection of 10 ml of contrast agent (gadopentetate dimeglumine 1:250, Omnipaqe 300, Knox gelatin 50%, and methylene blue), T1-weighted images with fat saturation in axial, oblique axial, coronal, and sagittal planes were obtained in neutral, dorsiflexion, and plantar flexion positions. Specimens were sectioned, allowing anatomic and MR correlation. RESULTS: Contrast agent outlining anterior and posterior aspects of the anterior talofibular ligament and posterior talofibular ligament (PTAF) was a normal finding, related to anterior and posterior recesses of the ankle joint that extend out beyond these ligaments in an anteroposterior direction above the level of the ligaments. Intraarticular contrast material allowed resolution of superficial and deep components of the posterior tibiofibular ligament. Both were seen separately from PTAF with dorsiflexion. Posterior intermalleolar ligament was not present in our specimens. Visualization of calcaneofibular ligament was much improved by contrast material outlining the articular aspect of the ligament. Visualization of the syndesmotic ligamentous complex also was improved by contrast material outlining the articular side of the ligaments and separating them from adjacent bone. Superiorly, the distribution of contrast agent was limited by the interosseous ligament. Visualization of the medial collateral ligaments was not improved by the presence of the intraarticular contrast material. CONCLUSION: MR arthrography of the ankle allows improved visualization and evaluation of the lateral and syndesmotic ligamentous complex.     

Normal uterus and FIGO stage I endometrial carcinoma: dynamic gadolinium-enhanced MR imaging

Dynamic magnetic resonance (MR) imaging was performed on a 1.5-T superconducting unit for evaluation of 26 stage I endometrial carcinomas. To establish the appearance of the normal uterus, 27 normal uteri were also evaluated. After rapid injection of gadopentetate dimeglumine, dynamic images were obtained every 30 seconds with the spin-echo technique in the sagittal plane. On dynamic studies of endometrial carcinoma, the tumor-myometrial contrast was marked at 120 seconds after administration of gadopentetate dimeglumine (contrast-to-noise ratio [C/N], 26.0). The tumor-myometrial contrast on the dynamic study was more marked than that on postcontrast T1-weighted images (C/N, 10.0) and on T2-weighted images (C/N, 2.14). Dynamic and postcontrast MR images were superior in enabling differentiation of viable tumors from necrosis or residual secretion in the endometrial cavity. In the evaluation of presence of tumor and myometrial invasion, the accuracy of T2-weighted imaging and dynamic imaging was 67.9% and 84.9%, respectively.