Contrast-enhanced T1-weighted Magnetic Resonance Research Articles

Permeability Imaging as a Biomarker of Leptomeningeal Collateral Flow in Patients with Intracranial Arterial Stenosis.

Different methods of angiography are of great clinical utility; however, it still remains unstandardized as which method would be suitable to determine cerebral collateral circulation. Here we compared digital subtraction angiography (DSA), computer tomography angiography (CTA) and dynamic contrast-enhanced T1-weighted imaging magnetic resonance imaging (MRI) findings in seven patients with severe intracranial arterial stenosis, and determine whether volume transfer constant (K(trans)) maps of permeability imaging could be used as the biomarkers of cerebral collateral circulation. We retrospectively reviewed seven adult patients with severe intracranial arterial stenosis or occlusion with a complete parenchymal and vascular imaging work-up. DSA, CTA source imaging (CTA-SI), arterial spin labeling (ASL), and K(trans) maps were used to assess their collateral flow. Cohen's Kappa coefficient was calculated to test the consistency of their collateral scores. A reasonable agreement was found between DSA and K(trans) maps (Kappa = 0.502, P < 0.001) when all 15 regional vascular sites were included, and a better agreement found after exclusion of perforating artery territories (N = 10 sites, Kappa = 0.766, P < 0.001). The agreement between CTA-SI and DSA was moderate on all 15 sites (Kappa = 0.413, P < 0.001) and 10 sites (Kappa = 0.329, P < 0.001). The agreement between ASL and DSA was least favorable, no matter for all 15 sites (Kappa = 0.270, P < 0.001) or 10 sites (Kappa = 0.205, P = 0.002). K(trans) maps are useful and promising for leptomeningeal collateral assessment, when compared to CTA-SI or ASL. Further studies are requited for verify its validity in a large registry of patients.

Combined use of 18 F-FDG PET and corticosteroid for diagnosis of deep-seated primary central nervous system lymphoma without histopathological confirmation.

Although histological diagnosis is indispensable in treating primary central nervous system lymphoma (PCNSL), we sometimes face an intractable situation in which tissue can be obtained only from a deep-seated brain lesion. In place of a histological diagnosis, the diagnostic adequacy of the combined use of 18 F-FDG PET and corticosteroid administration for PCNSL located in a deep-seated brain structure is reported. Patients with a deep-seated tumor were treated as having PCNSL without histological confirmation, based on the following criteria: (1) there was no evidence of systemic malignancy; (2) the tumor showed an extremely high FDG uptake relative to normal gray matter on pretreatment 18 F-FDG PET; (3) the tumor decreased in size 1 week after diagnostic therapy by corticosteroid administration on contrast-enhanced T1-weighted magnetic resonance imaging (MRI). FDG uptake of the lesion was evaluated by the maximum of standardized uptake values (SUVmax) and tumor-to-normal ratio of the SUV (T/N ratio). The extent of the tumor reduction was calculated by volumetric analysis for the treatment response to corticosteroid administration. Ten patients (4 males and 6 females) matched these criteria. On pretreatment 18 F-FDG PET, mean SUVmax in the tumor was 24.8 (8.75-60.75), and mean T/N ratio was 3.24 (2.17-5.12). The extent of tumor volume reduction was shown to be 21 to 68 % 1 week after diagnostic therapy by corticosteroids. Mean total dose and duration of corticosteroids were 719 mg as prednisolone and 6.5 days, respectively. Nine patients achieved complete response and one patient achieved partial response on MRI after standard treatment for PCNSL with high-dose methotrexate and/or whole-brain irradiation. Although the value of biopsy is universal, combining 18 F-FDG PET and corticosteroid administration is an important alternative method that may lead to the diagnosis of deep-seated PCNSLs in cases with intractable histopathological confirmations.

Quantitative analysis of tumor volume reduction after three-dimensional conformal radiation therapy for intracranial meningiomas

To provide radiobiological information on the inherent response of intracranial meningiomas after three-dimensional conformal radiation therapy. Quantitative tumor volume measurements were generated from 120 magnetic resonance images of a total of 24 patients. Gross tumor volumes were delineated on a series of contrast-enhanced T1-weighted magnetic resonance images by using commercial software. The percentage of tumor volume reduction at each follow-up was determined and compared to the baseline tumor volume. The median follow-up time was 103.5 months (range 30-137 months). The mean pre-radiation therapy tumor volume was 30.0 cm(3) (range 1.3-167.4 cm(3)). Tumor volume reduction was observed in 96 % of the study population. The mean absolute and relative tumor volume reduction were 14.0 cm(3) (range -0.6-84.5 cm(3)) and 40.8 % (range -6.8-82.9 %), respectively. The mean relative tumor volume reduction was 15.9, 28.9, 40.5, 50.3, and 52.6 % at 2, 4, 6, 8, and 10 years after irradiation. The quantitative volumetric analysis of the pattern of tumor volume reduction in response to irradiation gives an insight into the radiobiological nature of intracranial meningiomas after conventionally fractionated radiation therapy.

Toxicity evaluation of Gd2O3@SiO2 nanoparticles prepared by laser ablation in liquid as MRI contrast agents in vivo.

Poor toxicity characterization is one obstacle to the clinical deployment of Gd2O3@ SiO2 core-shell nanoparticles (Gd-NPs) for use as magnetic resonance (MR) imaging contrast agents. To date, there is no systematic toxicity data available for Gd-NPs prepared by laser ablation in liquid. In this article, we systematically studied the Gd-NPs’ cytotoxicity, apoptosis in vitro, immunotoxicity, blood circulation half-life, biodistribution and excretion in vivo, as well as pharmacodynamics. The results show the toxicity, and in vivo MR data show that these NPs are a good contrast agent for preclinical applications. No significant differences were found in cell viability, apoptosis, and immunotoxicity between our Gd-NPs and Gd in a DTPA (diethylenetriaminepentaacetic acid) chelator. Biodistribution data reveal a greater accumulation of the Gd-NPs in the liver, spleen, lung, and tumor than in the kidney, heart, and brain. Approximately 50% of the Gd is excreted via the hepatobiliary system within 4 weeks. Furthermore, dynamic contrast-enhanced T1-weighted MR images of xenografted murine tumors were obtained after intravenous administration of the Gd-NPs. Collectively, the single step preparation of Gd-NPs by laser ablation in liquid produces particles with satisfactory cytotoxicity, minimal immunotoxicity, and efficient MR contrast. This may lead to their utility as molecular imaging contrast agents in MR imaging for cancer diagnosis.

Permeability imaging in pediatric brain tumors.

While traditional computed tomography (CT) and magnetic resonance (MR) imaging illustrate the structural morphology of brain pathology, newer, dynamic imaging techniques are able to show the movement of contrast throughout the brain parenchyma and across the blood-brain barrier (BBB). These data, in combination with pharmacokinetic models, can be used to investigate BBB permeability, which has wide-ranging applications in the diagnosis and management of central nervous system (CNS) tumors in children. In the first part of this paper, we review the technical principles underlying four imaging modalities used to evaluate BBB permeability: PET, dynamic CT, dynamic T1-weighted contrast-enhanced MR imaging, and dynamic T2-weighted susceptibility contrast MR. We describe the data that can be derived from each method, provide some caveats to data interpretation, and compare the advantages and disadvantages of the different techniques. In the second part of this paper, we review the clinical applications that have been reported with permeability imaging data, including diagnosing the nature of a lesion found on imaging (neoplastic versus non-neoplastic, tumor type, tumor grade, recurrence versus pseudoprogression), predicting the natural history of a tumor, monitoring angiogenesis and tracking response to anti-angiogenic agents, optimizing chemotherapy agent selection, and aiding in the development of new antineoplastic drugs and methods to increase local delivery of chemotherapeutics.

Imaging and Target Volume Delineation in Glioma

Here we review current practices in target volume delineation for radical radiotherapy planning for gliomas. Current radiotherapy planning margins for glioma are informed by historic data of recurrence patterns using radiological imaging or post-mortem studies. Radiotherapy planning for World Health Organization grade II–IV gliomas currently relies predominantly on T1-weighted contrast-enhanced magnetic resonance imaging (MRI) and T2/fluid-attenuated inversion recovery sequences to identify the gross tumour volume (GTV). Isotropic margins are added empirically for each tumour type, usually without any patient-specific individualisation. We discuss novel imaging techniques that have the potential to influence radiotherapy planning, by improving definition of the tumour extent and its routes of invasion, thus modifying the GTV and allowing anisotropic expansion to a clinical target volume better reflecting areas at risk of recurrence. Identifying the relationships of tumour boundaries to important white matter pathways and eloquent areas of cerebral cortex could lead to reduced normal tissue complications. Novel magnetic resonance approaches to identify tumour extent and invasion include: (i) diffusion-weighted magnetic resonance metrics; (ii) diffusion tensor imaging; and (iii) positron emission tomography, using radiolabelled amino acids methyl-11C-L-methionine and 18F-fluoroethyltyrosine. Novel imaging techniques may also have a role together with clinical characteristics and molecular genetic markers in predicting response to therapy. Most significant among these techniques is dynamic contrast-enhanced MRI, which uses dynamic acquisition of images after injection of intravenous contrast. A number of studies have identified changes in diffusion and microvascular characteristics occurring during the early stages of radiotherapy as powerful predictive biomarkers of outcome.

Aneurysmal Bone Cyst Presenting as a Pathologic Fracture in a 12-Year-Old Football Player

ObjectiveThe purpose of this report is to describe a case of an aneurysmal bone cyst presenting as a pathologic fracture in a young athlete. Case reportA 12-year-old patient presented to a chiropractic teaching clinic with a 1-week history of posterior neck pain and stiffness following a helmet-to-helmet collision in football practice. Cervical spine radiographs were taken. Lateral view radiograph demonstrated a pathologic fracture through a lytic, expansive lesion in the posterior arch of C7 with mild subluxation of the C7/T1 apophyseal joints and angulation of the C7/T1 disk space. Based upon these findings, additional diagnostic imaging was ordered. Findings on advanced imaging studies included the following: On computed tomography, the C7 lesion showed medullary destruction, cortical thinning and expansion, and a horizontally oriented fracture through the spinous and lamina. Magnetic resonance imaging studies for sagittal T2 and contrast-enhanced T1-weighted magnetic resonance images revealed fluid/fluid levels in the C7 spinous and peripheral enhancement with contrast. OutcomeThe patient was referred to a local hospital for treatment. The lesion was treated with resection of the posterior arch, and an aneurysmal bone cyst was confirmed histologically. The patient developed a kyphotic deformity at the site of resection and cervical instability. A subsequent fusion was performed. ConclusionAneurysmal bone cysts are rare lesions. In this case, the initial traumatic history masked the underlying pathology. Although rare, pathologic fracture should be considered in cases of vertebral fracture in young patients.

Postoperative biliary adverse events following orthotopic liver transplantation: assessment with magnetic resonance cholangiography.

Biliary adverse events following orthotopic liver transplantation (OLT) are relatively common and continue to be serious causes of morbidity, mortality, and transplant dysfunction or failure. The development of these adverse events is heavily influenced by the type of anastomosis during surgery. The low specificity of clinical and biologic findings makes the diagnosis challenging. Moreover, direct cholangiographic procedures such as endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography present an inadmissible rate of adverse events to be utilized in clinically low suspected patients. Magnetic resonance (MR) maging with MR cholangiopancreatography is crucial in assessing abnormalities in the biliary system after liver surgery, including liver transplant. MR cholangiopancreatography is a safe, rapid, non-invasive, and effective diagnostic procedure for the evaluation of biliary adverse events after liver transplantation, since it plays an increasingly important role in the diagnosis and management of these events. On the basis of a recent systematic review of the literature the summary estimates of sensitivity and specificity of MR cholangiopancreatography for diagnosis of biliary adverse events following OLT were 0.95 and 0.92, respectively. It can provide a non-invasive method of imaging surgical reconstruction of the biliary anastomoses as well as adverse events including anastomotic and non-anastomotic strictures, biliary lithiasis and sphincter of Oddi dysfunction in liver transplant recipients. Nevertheless, conventional T2-weighted MR cholangiography can be implemented with T1-weighted contrast-enhanced MR cholangiography using hepatobiliary contrast agents (in particular using Gd-EOB-DTPA) in order to improve the diagnostic accuracy in the adverse events' detection such as bile leakage and strictures, especially in selected patients with biliary-enteric anastomosis.

Diffusion-Weighted MRI as a Biomarker of Tumor Radiation Treatment Response Heterogeneity: A Comparative Study of Whole-Volume Histogram Analysis versus Voxel-Based Functional Diffusion Map Analysis

RATIONALE: Treatment of glioblastoma (GBM) remains challenging due in part to its histologic intratumoral heterogeneity that contributes to its overall poor treatment response. Our goal was to evaluate a voxel-based biomarker, the functional diffusion map (fDM), as an imaging biomarker to detect heterogeneity of tumor response in a radiation dose escalation protocol using a genetically engineered murine GBM model. EXPERIMENTAL DESIGN: Twenty-four genetically engineered murine GBM models [Ink4a-Arf-/-/Ptenloxp/loxp/Ntv-a RCAS/PDGF(+)/Cre(+)] were randomized in four treatment groups (n = 6 per group) consisting of daily doses of 0, 1, 2, and 4 Gy delivered for 5 days. Contrast-enhanced T1-weighted and diffusion-weighted magnetic resonance imaging (MRI) scans were acquired for tumor delineation and quantification of apparent diffusion coefficient (ADC) maps, respectively. MRI experiments were performed daily for a week and every 2 days thereafter. For each animal, the area under the curve (AUC) of the percentage change of the ADC (AUCADC) and that of the increase in fDM values (AUCfDM+) were determined within the first 5 days following therapy initiation. RESULTS: Animal survival increased with increasing radiation dose. Treatment induced a dose-dependent increase in tumor ADC values. The strongest correlation between survival and ADC measurements was observed using the AUCfDM+ metric (R2 = 0.88). CONCLUSION: This study showed that the efficacy of a voxel-based imaging biomarker (fDM) was able to detect spatially varying changes in tumors, which were determined to be a more sensitive predictor of overall response versus whole-volume tumor measurements (AUCADC). Finally, fDM provided for visualization of treatment-associated spatial heterogeneity within the tumor.

Contrast-enhanced MR enterography as a stand-alone tool to evaluate Crohn's disease in a paediatric population

To assess the performance of contrast-enhanced T1-weighted magnetic resonance imaging (MRI) alone in the evaluation of Crohn's disease in comparison to all magnetic resonance enterography (MRE) imaging sequences together in an attempt to suggest limitation of the number of overall unenhanced sequences need for the follow-up evaluation. Twenty-five paediatric patients (mean age 14.1 ± 3.7 years, male = 12, female = 13) underwent MRE at 1.5 T for evaluation of Crohn's disease. Two radiologists reviewed only contrast-enhanced T1-weighted images in consensus on the first session. Whole images including unenhanced (steady-state free precession, single-shot fast spin-echo (HASTE), fat-suppressed T2-weighted) and contrast-enhanced T1-weighted sequences were reviewed in consensus during the second session with a 1 month interval, which was used as a reference standard. The readers evaluated the presence or absence of disease in 10 bowel segments in each patient. For the abnormal bowel segments, the readers then evaluated for active versus inactive disease and for the presence or absence of abscess. Sensitivity, specificity, and overall accuracy were calculated for detecting active inflammation. There were 53/250 bowel segments with active inflammation using the reference standard imaging method. The sensitivity, specificity, and accuracy for diagnosing active inflammation using contrast-enhanced images alone were 83.3%, 86.9%, and 84.9%. In five of the false-positive cases of detecting abscess from contrast-enhanced imaging alone, absence of abscesses was confirmed on the non-fat-suppressed HASTE images. The number of MRE sequences in paediatric Crohn's patients can be decreased while maintaining diagnostic accuracy using contrast-enhanced T1 and non-fat-suppressed HASTE images.

Modifications in Dynamic Contrast-Enhanced Magnetic Resonance Imaging Parameters After α-Particle-Emitting 227Th-trastuzumab Therapy of HER2-Expressing Ovarian Cancer Xenografts

The purpose of this study was to investigate the effect of α-particle-emitting (227)Th-trastuzumab radioimmunotherapy on tumor vasculature to increase the knowledge about the mechanisms of action of (227)Th-trastuzumab. Human HER2-expressing SKOV-3 ovarian cancer xenografts were grown bilaterally in athymic nude mice. Mice with tumor volumes 253 ± 36 mm(3) (mean ± SEM) were treated with a single injection of either (227)Th-trastuzumab at a dose of 1000 kBq/kg body weight (treated group, n=14 tumors) or 0.9% NaCl (control group, n=10 tumors). Dynamic T1-weighted contrast-enhanced magnetic resonance imaging (DCEMRI) was used to study the effect of (227)Th-trastuzumab on tumor vasculature. DCEMRI was performed before treatment and 1, 2, and 3 weeks after therapy. Tumor contrast-enhancement curves were extracted voxel by voxel and fitted to the Brix pharmacokinetic model. Pharmacokinetic parameters for the tumors that underwent radioimmunotherapy were compared with the corresponding parameters of control tumors. Significant increases of kep, the rate constant of diffusion from the extravascular extracellular space to the plasma (P<.05), and kel, the rate of clearance of contrast agent from the plasma (P<.01), were seen in the radioimmunotherapy group 2 and 3 weeks after injection, compared with the control group. The product of kep and the amplitude parameter A, associated with increased vessel permeability and perfusion, was also significantly increased in the radioimmunotherapy group 2 and 3 weeks after injection (P<.01). Pharmacokinetic modeling of MRI contrast-enhancement curves evidenced significant alterations in parameters associated with increased tumor vessel permeability and tumor perfusion after (227)Th-trastuzumab treatment of HER2-expressing ovarian cancer xenografts.

A Bayesian Diagnostic System to Differentiate Glioblastomas from Solitary Brain Metastases

This paper aimed to construct a Bayesian network-based decision support system to differentiate glioblastomas from solitary metastases, based on multimodality MR examination. We enrolled 51 patients with solitary brain tumors (26 with glioblastomas and 25 with solitary brain metastases). These patients underwent contrast-enhanced T1-weighted magnetic resonance (MR) examination, diffusion tensor imaging (DTI), dynamic susceptibility contrast (DSC) MRI, and fluid-attenuated inversion recovery (FLAIR). We generated a set of MR biomarkers, including relative cerebral blood volume in the enhancing region, and fractional anisotropy measured in the immediate peritumoral area. We then generated a Bayesian network model to represent associations among these imaging-derived predictors, and the group membership variable, (glioblastoma or solitary metastasis). This Bayesian network can be used to classify new patients' tumors based on their MR appearance. The Bayesian network model accurately differentiated glioblastomas from solitary metastases. Prediction accuracy was 0.94 (sensitivity = 0.96, specificity = 0.92) based on leave-one-out cross-validation. The area under the receiver operating characteristic curve was 0.90. A Bayesian network-based decision support system accurately differentiates glioblastomas from solitary metastases, based on MR-derived biomarkers.

Magnetic Resonance Imaging–guided Focused Ultrasound Treatment of Pedunculated Subserosal Uterine Fibroids: A Preliminary Report

PurposeTo evaluate magnetic resonance (MR) imaging–guided focused ultrasound (US) as a treatment for pedunculated subserosal fibroids. Materials and MethodsOver a 2-year period (March 2007 to March 2009), 135 women with symptomatic uterine fibroids were treated in the authors’ institution using MR imaging–guided focused US. Of these women, nine (mean age, 39 years; range, 25–47 y) had a single pedunculated subserosal fibroid. During treatment, these pedunculated fibroids were targeted, while sparing the stalk connection between the fibroid and the uterus. Contrast-enhanced T1-weighted MR images were obtained immediately after the treatment to measure the nonperfused volume (NPV) ratio and to check stalk viability. Changes in tumor volume, diameter of the stalk, patient symptoms and adverse events were evaluated 6 months after treatment. ResultsThe volume of the treated fibroids (n=9) ranged from 79–380cm3 (mean, 198cm3), and NPV ratio ranged from 45%–80% (mean, 67%). MR imaging follow-up at 6 months showed a 14%–48% (mean, 30%) reduction in the volume of the treated fibroids (P =.008). In all cases, the pedunculated subserosal fibroids remained connected to the uterus with a 13% average decrease in the mean diameter of the stalks (from 3.5 to 3.0cm; P=.008). Eight of nine patients (89%) reported improvement in bulk-related fibroid symptoms after treatment. ConclusionsThe results of this preliminary study suggest that MR imaging–guided focused US may be a safe and effective treatment for pedunculated subserosal fibroids. Larger prospective studies with longer follow-up are needed to confirm the suitability of MR imaging–guided focused US to treat this type of fibroid.

Endometrial carcinoma with peritoneal keratin granulomas mimicking peritoneal carcinomatosis: a case report and imaging diagnosis

We report the case of a 71-year-old woman diagnosed as having endometrioid adenocarcinoma with squamous differentiation (adenoacanthoma, grade 1) and peritoneal keratin granuloma. Preoperative diagnostic imaging showed a uterine cavity filled with a large mass, many peritoneal nodules, and free fluid in the Douglas pouch, indicating a peritoneal carcinomatosis. Endometrial biopsy revealed grade 1 endometrioid adenocarcinoma. Eventually, postoperative histopathological examination led to the diagnosis. Although peritoneal keratin granulomas mimicking peritoneal carcinomatosis are due to endometrial carcinomas containing squamous elements, gynecological oncologists should keep in mind such situations. The combination of contrast-enhanced T1-weighted and diffusion-weighted magnetic resonance imaging is helpful for preoperative differential diagnosis.

Impact of MRI-based postimplant dosimetric assessment in prostate brachytherapy using contrast-enhanced T1-weighted images

PurposeTo compare contrast-enhanced T1-weighted (CE-T1WI) magnetic resonance imaging (MRI) with computed tomography (CT) for postimplant dosimetry and seed recognition in prostate brachytherapy. Methods and MaterialsA total of 245 patients who received 125I prostate brachytherapy with or without external beam radiotherapy were enrolled. For postimplant analysis, CT and MRI scans were obtained at 1 month after seed implantation. For MRI-based dosimetry, T2-weighted images were fused with the CE-T1WI; the prostate was delineated on the T2-weighted images, and the seed detection was performed manually on the CE-T1WI. In CT-based dosimetry, the seed detection was essentially performed automatically. The dosimetric results obtained by MRI-based and CT-based dosimetry were compared. ResultsThe mean prostate D90 (the minimum dose received by 90% of the prostate volume) estimated by MRI-based and CT-based dosimetry were 113% and 115%, respectively, with no significant difference. The mean prostate V100 (the percent volume of the postimplant prostate receiving 100% of the prescribed dose) estimated by MRI-based and CT-based dosimetry were 95.2% and 95.8%, respectively, again with no significant difference. The mean prostate V150 (the percent volume of the postimplant prostate receiving 150% of the prescribed dose) estimated by MRI-based and CT-based dosimetry were 52.8% and 57.0%, respectively (p<0.01). In all of the 35 patients (14%) in whom the MRI-based V150 were at least 10% lower than the CT-based results, the seed detection by CT-based dosimetry was overestimated in highly seed-clustered areas or in the areas close to calcifications because of reconstruction artifacts in CT images. ConclusionsMRI-based dosimetry using CE-T1WI appears to be acceptable. Our results suggest that MRI-based dosimetry is a practical method for estimation of the higher dose distribution, especially if seeds are clustered together or when they are close to calcifications.

Pilot study on evaluation of any correlation between MR perfusion (Ktrans) and diffusion (apparent diffusion coefficient) parameters in brain tumors at 3 Tesla

Purpose: To assess any correlation of volume transfer constant (Ktrans) with apparent diffusion coefficient (ADC) in different brain tumor types at 3 T magnetic resonance (MR) imaging. Materials and methods: Thirteen patients with brain tumors (8 men, 5 women; mean age 54.6 ± 17.7 years) were enrolled in this retrospective study. All patients underwent dynamic contrast-enhanced T1-weighted MR perfusion and diffusion-weighted imaging using a 3 T scanner. Ktrans was estimated by specially designed software. For each tumor, regions of interest (ROIs) were manually selected on corresponding Ktrans and ADC maps. Pearson correlation coefficients were obtained for maximum, mean and minimum values of Ktrans and ADC of all ROIs. Based on clinicopathologic results, the final diagnoses of patients were glioblastoma multiforme (3), low-grade to anaplastic gliomas (4), meningiomas (3) and metastatic tumors (3). Results: Ktrans(max) values were significantly inversely correlated with ADC(min) values (r = –0.536, P < 0.001) and ADC(mean) values (r = –0.465, P < 0.001). Ktrans(mean) and Ktrans(min) values were significantly inversely correlated with ADC(mean) (r = –0.228, P = 0.038) and ADC(max) values (r = –0.355, P = 0.001), respectively. Conclusion: We found that irrespective of brain tumor type, there is an inverse correlation between ADC and Ktrans. Our findings highlight an intricate relationship between vascular permeability and the tumor microenvironment, probably modulating and/or interacting with changes such as increased cellularity, ischemic insult and varying extracellular matrix composition.

Liver-specific contrast agents

In the patient with cancer, magnetic resonance imaging is increasingly used as a diagnostic tool for disease detection, lesion characterization, as well as the assessment of treatment response. Although non-contrast T1-weighted and T2-weighted imaging, together with low molecular weight extracellular gadolinium contrast-enhanced T1-weighted magnetic resonance imaging remain the cornerstone for liver assessment, there is increasing recognition of the benefits of liver-specific contrast agents for disease evaluation.

Targeted Vessel Ablation for More Efficient Magnetic Resonance-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids

PurposeTo report the first clinical experience with targeted vessel ablation during magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) treatment of symptomatic uterine fibroids.MethodsPretreatment T1-weighted contrast-enhanced magnetic resonance angiography was used to create a detailed map of the uterine arteries and feeding branches to the fibroids. A three-dimensional overlay of the magnetic resonance angiography images was registered on 3D T2-weighted pretreatment imaging data. Treatment was focused primarily on locations where supplying vessels entered the fibroid. Patients were followed 6 months after treatment with a questionnaire to assess symptoms and quality of life (Uterine Fibroid Symptom and Quality of Life) and magnetic resonance imaging to quantify shrinkage of fibroid volumes.ResultsIn two patients, three fibroids were treated with targeted vessel ablation during MR-HIFU. The treatments resulted in almost total fibroid devascularization with nonperfused volume to total fibroid volume ratios of 84, 68, and 86%, respectively, of treated fibroids. The predicted ablated volumes during MR-HIFU in patients 1 and 2 were 45, 40, and 82 ml, respectively, while the nonperfused volumes determined immediately after treatment were 195, 92, and 190 ml respectively, which is 4.3 (patient 1) and 2.3 (patient 2) times higher than expected based on the thermal dose distribution. Fibroid-related symptoms reduced after treatment, and quality of life improved. Fibroid volume reduction ranged 31–59% at 6 months after treatment.ConclusionTargeted vessel ablation during MR-HIFU allowed nearly complete fibroid ablation in both patients. This technique may enhance the use of MR-HIFU for fibroid treatment in clinical practice.

Detection of Intracoronary Thrombus by Magnetic Resonance Imaging in Patients With Acute Myocardial Infarction

Persistent intracoronary thrombus after plaque rupture is associated with an increased risk of subsequent myocardial infarction and mortality. Coronary thrombus is usually visualized invasively by x-ray coronary angiography. Non-contrast-enhanced T1-weighted magnetic resonance (MR) imaging has been useful for direct imaging of carotid thrombus and intraplaque hemorrhage by taking advantage of the short T1 of methemoglobin present in acute thrombus and intraplaque hemorrhage. The aim of this study was to investigate the use of non-contrast-enhanced MR for direct thrombus imaging (MRDTI) in patients with acute myocardial infarction. Eighteen patients (14 men; age, 61±9 years) underwent MRDTI within 24 to 72 hours of presenting with an acute coronary syndrome before invasive x-ray coronary angiography; MRDTI was performed with a T1-weighted, 3-dimensional, inversion-recovery black-blood gradient-echo sequence without contrast administration. Ten patients were found to have intracoronary thrombus on x-ray coronary angiography (left anterior descending, 4; left circumflex, 2; right coronary artery, 4; and right coronary artery-posterior descending artery, 1), and 8 had no visible thrombus. We found that MRDTI correctly identified thrombus in 9 of 10 patients (sensitivity, 91%; posterior descending artery thrombus not detected) and correctly classified the control group in 7 of 8 patients without thrombus formation (specificity, 88%). The contrast-to-noise ratio was significantly greater in coronary segments containing thrombus (n=10) compared with those without visible thrombus (n=131; mean contrast-to-noise ratio, 15.9 versus 2.6; P<0.001). Use of MRDTI allows selective visualization of coronary thrombus in a patient population with a high probability of intracoronary thrombosis.

Case 171: Facial Nerve Hemangioma

The patient’s imaging features, especially the honeycomb pattern of ossific changes in the geniculate fossa, were virtually pathognomonic for ossifying hemangioma of the facial nerve.