Delayed Magnetic Resonance Imaging Research Articles

The performance of gadolinium diethylene triamine pentaacetate-pullulan hepatocyte-specific T1 contrast agent for MRI

The magnetic resonance (MR) functionalities of pullulan-conjugated gadolinium diethylene triamine pentaacetate (Gd-DTPA-Pullulan) as a new hepatocyte-specific contrast agent were evaluated. Pullulan, which specifically accumulates on hepatocytes via asialoglycoprotein receptors, was chemically linked with Gd-DTPA. Gd-DTPA-Pullulan displayed three times greater contrast enhancement than Gd-DTPA-BMA (Omniscan ®) in delayed MR imaging (MRI) on orthotopic rat hepatocarcinoma (HCC). This contrast effect lasted up to 24 h. In particular, Gd-DTPA-Pullulan displayed a discriminative MR contrast on the regenerative and malignant hepatic nodules sequentially observed during the progress of cirrhotic HCC. Approximately 50% of injected Gd-DTPA-Pullulan was eliminated via the hepato-biliary system. IC 50 of Gd-DTPA-Pullulan on Chang liver cells was much higher than Gd-DTPA and Gd-DTPA-BMA (309.1 ± 11.2, 173.5 ± 15.5 and 49.4 ± 8.9 μM, respectively). Any significant toxicities of Gd-DTPA-Pullulan at the conventional dose on the rats weren’t detected on histology studies. Gd-DTPA-Pullulan worked as a hepatocyte-specific MR contrast agent with increased MR functionalities and an acceptable safety profile setting the scene for future clinical trials.

Detection and Characterization of Focal Liver Lesions

To prospectively evaluate the safety and efficacy of combined unenhanced and gadoxetic acid disodium (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging compared with unenhanced MR imaging and triphasic contrast-enhanced spiral computed tomography (CT) for the detection and characterization of focal liver lesions. The study was reviewed and approved by the institutional review board at each of the 15 centers involved in the study, and informed written consent was given by all patients. In total, 178 patients with suspected focal hepatic lesions (based, in most patients, on CT, tumor marker and ultrasound examinations) underwent combined MR imaging with a single, rapid injection of Gd-EOB-DTPA 0.025 mmol/kg, including T1-weighted dynamic and delayed MR images 20 to 40 minutes postinjection. Triphasic contrast-enhanced CT, the comparator examination, was performed within 4 weeks of MR imaging. Standard of references (SOR) were resection histopathology and intraoperative ultrasonography, or combined CT during arterial portography and CT hepatic arteriography; in cases where, although the major lesions were treated, some lesion(s) were not treated, follow-up superparamagnetic iron oxide-enhanced MR imaging was additionally performed. All images were assessed for differences in lesion detection and characterization (specific lesion type) by on-site readers and 3, blinded (off-site) reviewers. All adverse events (AEs) occurring within 72 hours after Gd-EOB-DTPA administration were reported. Overall, 9.6% of patients who received Gd-EOB-DTPA reported 21 drug-related AEs. A total of 151 patients were included in the efficacy analysis. Combined MR imaging showed statistically higher sensitivity in lesion detection (67.5%-79.5%) than unenhanced MR imaging (46.5%-59.1%; P < 0.05 for all). Combined MR imaging also showed higher sensitivity in lesion detection than CT (61.1%-73.0%), with the results being statistically significant (P < 0.05) for on-site readers and 2 of 3 blinded readers. Higher sensitivity in lesion detection with combined MR imaging compared with CT was also clearly demonstrated in the following subgroups: lesions with a diameter <or=20 mm (lesions <or=10 mm: 38.0%-55.4% vs. 26.1%-47.3%, respectively; lesions 10-20 mm: 71.1%-87.3% vs. 65.7%-78.4%, respectively); in cirrhotic patients (64.5%-75.4% vs. 54.5%-70.3%, respectively); and in patients with hepatocellular carcinoma (66.6%-78.6% vs. 59.1%-71.6%, respectively). Combined MR imaging demonstrated a higher proportion of correctly characterized lesions (50.5%-72.1%) than unenhanced MR imaging (30.2%-50.0%; P < 0.05 for all), whereas there were no significant differences compared with CT (49.0%-68.1%), except for one blinded reader (P < 0.05). In this study, hepatocyte-specific Gd-EOB-DTPA was shown to be safe and to improve the detection and characterization of focal hepatic lesions compared with unenhanced MR imaging. When compared with spiral CT, Gd-EOB-DTPA enhanced MRI seems to be beneficial especially for the detection for smaller lesions or hepatocellular carcinoma underlying cirrhotic liver.

Evaluation of Reperfused Myocardial Infarction by Low-Dose Multidetector Computed Tomography Using Prospective Electrocardiography (ECG)-Triggering: Comparison with Magnetic Resonance Imaging

PurposeTo evaluate the potential of prospective electrocardiography (ECG)-gated 64-slice multidetector computed tomography (MDCT) for evaluation of myocardial enhancement, infarct size, and stent patency after percutaneous coronary intervention (PCI) with stenting in patients with myocardial infarction.Materials and MethodsSeventeen patients who were admitted with acute myocardial infarction were examined with prospective ECG-gated 64-slice cardiac MDCT and magnetic resonance (MR) imaging after reperfusion using PCI with stenting. Cardiac MDCT was performed with two different phases: arterial and delayed phases. We evaluated the stent patency on the arterial phase, and nonviable myocardium on the delayed phase of computed tomography (CT) image, and they were compared with the results from the delayed MR images.ResultsTotal mean radiation dose was 7.7 ± 0.5 mSv on the two phases of CT images. All patients except one showed good patency of the stent at the culprit lesion on the arterial phase CT images. All patients had hyperenhanced area on the delayed phase CT images, which correlated well with those on the delayed phase MR images, with a mean difference of 1.6% (20 ± 10% vs. 22 ± 10%, r = 0.935, p = 0.10). Delayed MR images had a better contrast-to-noise ratio (CNR) than delayed CT images (27.1 ± 17.8% vs. 4.3 ± 2.1%, p < 0.001).ConclusionProspective ECG-gated 64-slice MDCT provides the potential to evaluate myocardial viability on delayed phase as well as for stent patency on arterial phase with an acceptable radiation dose after PCI with stenting in patients with myocardial infarction.

Adenoma of the Nipple

Adenoma of the nipple (nipple adenoma) is a rare breast tumor that can show various histologic features. We present magnetic resonance (MR) and other imaging findings of a case of nipple adenoma and correlate them with detailed histologic features of the tumor. The lesion showed early strong enhancement with rim enhancement on dynamic contrast-enhanced MR images, and internal portions of the lesion showed washout on delayed MR images. Histologically, the tumor showed expansive growth with surrounding dense collagenous tissue and large vessels. Internal portions of the lesion showed a relatively low degree of fibrosis compared with that of the surrounding area, and tiny vessels were observed. These features were clearly reflected in the MR findings.

Efficacy and Safety of MR Imaging with Liver-specific Contrast Agent: U.S. Multicenter Phase III Study

To assess prospectively the efficacy and safety of postcontrast magnetic resonance (MR) imaging with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) compared with that of precontrast MR imaging in patients who are known to have or are suspected of having liver lesions and who are scheduled for hepatic surgery. Investigational review board approval and written informed consent were obtained. HIPAA went into effect after data collection. A total of 172 patients were enrolled. After precontrast MR imaging, 169 patients (94 men, 75 women; mean age, 61 years; age range, 19-84 years) received an intravenous bolus of 25 micromol/kg Gd-EOB-DTPA and underwent dynamic gradient-recalled-echo and delayed MR imaging 20 minutes after injection. Arterial and portal phase computed tomography (CT) were performed within 6 weeks of MR imaging. The standard of reference was surgery with intraoperative ultrasonography (US) and biopsy and/or pathologic evaluation of resected liver segments and/or 3-month follow-up of nonresected segments if intraoperative US was not available. Three blinded reviewers and unblinded site investigators identified liver lesions on segment maps. The Wilcoxon signed rank test was used to compare differences in per-patient sensitivity of precontrast and postcontrast MR images. Adverse events were recorded, and patient monitoring and laboratory assay were performed at time of injection and up to 24 hours after contrast material administration. At MR imaging, 316 lesions were identified in 131 patients. In 77% (P = .012), 72% (P = .15), and 71% (P = .027) of patients for readers 1, 2, and 3, respectively, more lesions were seen at precontrast and postcontrast MR imaging combined than at precontrast MR imaging alone. Sensitivity values for blinded readings were significantly greater at postcontrast MR imaging than at precontrast MR imaging for two of three blinded readers. For all blinded readers, combined precontrast and postcontrast MR images showed no difference in sensitivity compared with helical CT scans. The use of MR imaging, however, yielded fewer patients with at least one false-positive lesion (37%, 31%, and 34% of patients for readers 1, 2, and 3, respectively) than did helical CT (45%, 36%, and 43% of patients for readers 1, 2, and 3, respectively). Compared with precontrast MR imaging, postcontrast MR imaging with Gd-EOB-DTPA demonstrated improved sensitivity for lesion detection in the majority of blinded readers, with no substantial adverse events.

Patellar articular cartilage lesions: in vitro MR imaging evaluation after placement in gadopentetate dimeglumine solution.

To evaluate T1-weighted magnetic resonance (MR) imaging after diffusion of gadopentetate dimeglumine for visualization of articular cartilage lesions. MR imaging was performed in eight human cadaveric patella specimens immediately and 4 hours after placement into a vessel filled with gadopentetate dimeglumine solution (2.5 mmol/L). T1-weighted spin-echo and inversion-recovery turbo spin-echo MR sequences with nulled cartilage signal (inversion time of 300 msec) were used. In a total of 128 articular cartilage areas, MR imaging findings were compared with macroscopic and histopathologic findings. Pathologic evaluation was performed by one musculoskeletal pathologist. With knowledge of pathologic observations, MR images were analyzed by one musculoskeletal radiologist with regard to intrinsic signal intensity characteristics and surface abnormalities of articular cartilage. Histopathologic findings demonstrated 67 areas of normal articular cartilage and 66 cartilage lesions (grade 1, n = 19; grade 2, n = 15; grade 3, n = 26; grade 4, n = 6). All grade 3 and 4 lesions could be identified on MR images obtained immediately after submersion and after 4 hours. Ninety-four percent of grade 1 and 2 lesions were identified as areas of predominantly decreased contrast enhancement on delayed MR images obtained with both sequences. MR images obtained immediately after submersion demonstrated abnormal signal intensity in only 9% and 12% of grade 1 and 2 lesions, respectively. T1-weighted MR images obtained in vitro after gadopentetate dimeglumine diffusion allow demonstration of articular cartilage surface lesions and early stages of cartilage degradation.

MR Imaging with Gd-DTPA Enhancement in the Testicular Ischemia in Rat Model: Evaluation of Testicular Viability

Purpose: To find the magnetic resonance (MR) imaging patterns and to determine the viability in normal, infracted and reversible ischemic testis of the rat. Materials and Methods: Fifteen Sprague-Dawley rats were examined and they were divided into four groups. Group 1 was the control group, group 2 had a complete testicular artery ligation, group 3 had a complete ligation with reperfusion after 1 hour and group 4 had a complete ligation with reperfusion after 12 hours. All four groups were imaged every 5 minutes for 30 minutes. Delayed MR imaging was obtained every 30 minutes for 90 minutes. Two follow-up MR images were performed in all groups at a one-week interval. The signal intensity was measured in the normal testis, ischemic testis, and in muscle, water and fat in every rat at each time, with the phantom attached near the scrotum during the scanning. The signal intensities were analyzed statistically. Results: On initial and 2-week follow-up examinations, the pattern of change differed among four groups (p

Edema fluid accumulation within necrotic brain tissue as a cause of the mass effect of cerebral contusion in head trauma patients.

The early massive edema caused by severe cerebral contusion results in progressive intracranial pressure (ICP) elevation and clinical deterioration within 24-72 hours post-trauma. Surgical excision of the necrotic brain tissue represents the only therapy, which can provide satisfactory control of the elevated ICP and clinical deterioration. In order to elucidate the mechanisms underlying the early massive edema, we have carried out a series of detailed clinical studies. Diffusion magnetic resonance (MR) imaging and apparent diffusion co-efficient (ADC) mapping suggest that cells in the central area of contusion undergo shrinkage, disintegration and homogenization, whereas cellular swelling is predominant in the peripheral area during the period of 24-72 hours post-trauma. The ADC values in the central and peripheral areas are maximally dissociated during this period. A large amount of edema fluid accumulates within the necrotic brain tissue of the central area beginning at approximately 24 hours post-trauma. We have found that fluid-blood interface formation within the central area does not represent an uncommon finding in various neuroimaging examinations of cerebral contusions, indicating layering of red blood cells within the necrotic brain tissue accumulating voluminous edema fluid. Intravenous slow infusion of gadolinium-DTPA and delayed MR imaging revealed that the central area of contusion can be enhanced at 24-48 hours post-trauma. implying that water supply from the blood vessels is not completely interrupted. Necrotic brain tissue sampled from the central area of contusion during surgery demonstrates a very high osmolality. It appears that the capacitance for edema fluid accumulation increases in the central area, whereas cellular swelling in the peripheral area elevates the resistance for edema fluid propagation. Combination of these circumstances may facilitate edema fluid accumulation in the central area. We also suggest that the dissociation of ADC values and high osmolality within the necrotic brain tissue may generate an osmotic potential across the central and peripheral areas and contribute to the early massive edema caused by cerebral contusion.

Delayed magnetic resonance imaging with G d-DTPA differentiates subdural hygroma and subdural effusion

BACKGROUND Posttraumatic subdural fluid collection is not a single clinical entity but can be divided into subdural hygroma and subdural effusion. Appropriate treatment requires preoperative differentiation. Delayed magnetic resonance (MR) imaging with intravenous administration of gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) was used to differentiate subdural hygroma and subdural effusion. METHODS Timed arterial blood specimens were taken after intravenous Gd administration in patients with posttraumatic subdural fluid collections (five subdural hygromas and 13 subdural effusions). Delayed MR imaging was performed 1 hour after administration of Gd-DTPA. Gd-DTPA concentrations in the subdural fluid and blood specimens were measured by ion coupled plasma emission spectrometry. Dynamic biologic modeling was used to calculate the transfer rate constant for Gd-DTPA influx into these subdural fluid collections. RESULTS The Gd concentrations in subdural hygromas and subdural effusions were 16 ± 6 and 79 ± 12 nmol/mL, respectively. The transfer rate constants for subdural hygromas and subdural effusions were 4.8 ± 2.1 and 20.6 ± 2.1 (×10 −4)min −1, respectively. These values were significantly higher in subdural effusions than in subdural hygromas ( p < 0.01). Delayed MR imaging with Gd showed significantly higher mean enhancement of 77.1 ± 14.2% for subdural effusions compared to 4.6 ± 3.1% for subdural hygromas ( p < 0.01). CONCLUSIONS Delayed MR imaging with Gd can differentiate subdural hygroma and subdural effusion.

110 O - Magnetic resonance imaging guided minimally invasive treatment of breast cancer

Interstitial laser photocoagulation (ILP) is a recently developed, minimally invasive technique of local tumour destruction within solid organs. It current limitation is the lack of an optimal imaging technique to demonstrate treatment effects. This study was designed to assess the role of breast MR (magnetic resonance) imaging in the guidance of ILP for the minimally invasive treatment of primary breast cancer. Thirty patients with symptomatic breast cancer diagnosed by cytology underwent ILP using a single fibre (n = 20) and four fibres (n = 10) prior to surgical excision. MR imaging was performed using a contrast enhanced T1W 3D FLASH sequence before and after laser treatment. Real time MR imaging of laser treatment was performed in 7 patients. Following resection the extent of disease, size of laser burn and the extent of residual tumour were correlated with the MR images. Per-procedural and delayed MR images accurately showed the extent of laser induced necrosis and residual viable tumour. The correlation coefficent (MR v Histopathological analysis) for the laser burn diameter and residual tumour was 0.90 and 0.89 respectively. In conclusion, post-contrast MR images can accurately define the extent of both laser induced necrosis and residual viable tumour following ILP treatment of breast cancer.

Lumbosacral spine: early and delayed MR imaging after administration of an expanded dose of gadopentetate dimeglumine in healthy, asymptomatic subjects.

To determine normal magnetic resonance (MR) imaging enhancement characteristics of the lumbosacral spine after intravenous administration of an expanded dose of gadopentetate dimeglumine. T1-weighted MR images of the lumbosacral spine were acquired before and after injection of 0.3 mmol/kg gadopentetate dimeglumine in 12 healthy subjects (eight men, four women; age range, 22-57 years). In 10 (91%) of the 11 subjects who completed the investigation, multifocal linear enhancement within the thecal sac that generally extended from the conus to the nerve-root sheaths was demonstrated. In all cases, enhancement was seen in the facet joints and the intervertebral disks parallel to the vertebral end-plates. After an expanded dose of intravenous gadopentetate dimeglumine, multiple intrathecal and extrathecal structures were enhanced. Recognition of normal enhancement patterns after an expanded gadopentetate dimeglumine dose is important because such enhancement after routine injection of 0.1 mmol/kg gadopentetate dimeglumine is often thought to indicate disease.