Sequential Magnetic Resonance Research Articles

Spontaneous Reperfusion after In Situ Thromboembolic Stroke in Mice

Injection of thrombin into the middle cerebral artery (MCA) of mice has been proposed as a new model of thromboembolic stroke. The present study used sequential multiparametric Magnetic Resonance Imaging (MRI), including Magnetic Resonance Angiography (MRA), Diffusion-Weighted Imaging (DWI) and Perfusion-Weighted Imaging (PWI), to document MCA occlusion, PWI-DWI mismatch, and lesion development. In the first experiment, complete MCA occlusion and reproducible hypoperfusion were obtained in 85% of animals during the first hour after stroke onset. In the second experiment, 80% of animals showed partial to complete reperfusion during a three-hour follow-up. Spontaneous reperfusion thus contributed to the variability in ischemic volume in this model. The study confirmed the value of the model for evaluating new thrombolytic treatments, but calls for extended MRI follow-up at the acute stage in therapeutic studies.

Ultrasmall Superparamagnetic Particles of Iron Oxide in Patients With Acute Myocardial Infarction

Background— Inflammation following acute myocardial infarction (MI) has detrimental effects on reperfusion, myocardial remodelling, and ventricular function. Magnetic resonance imaging using ultrasmall superparamagnetic particles of iron oxide can detect cellular inflammation in tissues, and we therefore explored their role in acute MI in humans. Methods and Results— Sixteen patients with acute ST-segment elevation MI were recruited to undergo 3 sequential magnetic resonance scans within 5 days of admission at baseline, 24 and 48 hours following no infusion (controls; n=6) or intravenous infusion of ultrasmall superparamagnetic particles of iron oxide (n=10; 4 mg/kg). T2*-weighted multigradient-echo sequences were acquired and R2* values were calculated for specific regions of interest. In the control group, R2* values remained constant in all tissues across all scans with excellent repeatability (bias of −0.208 s −1 , coefficient of repeatability of 26.96 s −1 ; intraclass coefficient 0.989). Consistent with uptake by the reticuloendothelial system, R2* value increased in the liver (84±49.5 to 319±70.0 s −1 ; P <0.001) but was unchanged in skeletal muscle (54±8.4 to 67.0±9.5 s −1 ; P >0.05) 24 hours after administration of ultrasmall superparamagnetic particles of iron oxide. In the myocardial infarct, R2* value increased from 41.0±12.0 s −1 (baseline) to 155±45.0 s −1 ( P <0.001) and 124±35.0 s −1 ( P <0.05) at 24 and 48 hours, respectively. A similar but lower magnitude response was seen in the remote myocardium, where it increased from 39±3.2 s −1 (baseline) to 80±14.9 s −1 ( P <0.001) and 67.0±15.7 s −1 ( P <0.05) at 24 and 48 hours, respectively. Conclusions— Following acute MI, uptake of ultrasmall superparamagnetic particles of iron oxide occurs with the infarcted and remote myocardium. This technique holds major promise as a potential method for assessing cellular myocardial inflammation and left ventricular remodelling, which may have a range of applications in patients with MI and other inflammatory cardiac conditions. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT01323296.

Quantitative characterization of growth rate of an incidental deep dermoid cyst in a child using sequential magnetic resonance imaging

When orbital lesions are discovered incidentally, some have advocated observation given the slow-growing nature of deep dermoids; however, little has been published regarding the true growth potential of these tumors. We describe a case of an incidental deep orbital dermoid cyst in a 7.5-month-old girl with retinoblastoma. The cyst was monitored with five sequential magnetic resonance imaging studies of the orbit over 23 months with careful documentation of growth. The cyst was surgically removed without complication, and histopathology confirmed the diagnosis of dermoid cyst. This case represents the first published quantitative measurement of dermoid growth potential and highlights the need for close early monitoring in incidentally discovered cases.

Sequential MR Imaging of Denervated and Reinnervated Skeletal Muscle as Correlated to Functional Outcome

To prospectively assess the short inversion time inversion-recovery (STIR) magnetic resonance (MR) signal intensity changes of denervated and reinnervated skeletal muscle over time in clinical patients. This study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-three patients with complete traumatic transection of the median or ulnar nerve in the forearm were prospectively followed for 12 months after surgical nerve repair. STIR MR images of selected intrinsic hand muscles were obtained 1, 3, 6, 9, and 12 months after nerve repair, and signal intensities of denervated and reinnervated muscles were measured semiquantitatively. After 12 months, hand function was assessed. Signal intensity ratios were correlated to functional outcome with analysis of variance. Of the 23 patients, 10 had good function recovery, while 13 had poor recovery. For the group with good function recovery, mean signal intensity ratios of 1.267 ± 0.060 (standard deviation), 1.357 ± 0.116, 1.297 ± 0.111, 1.205 ± 0.096, and 1.086 ± 0.104 were found at 1-, 3-, 6-, 9-, and 12-month follow-up, respectively. In the group with poor recovery, mean signal intensity ratios of 1.299 ± 0.056, 1.377 ± 0.094, 1.419 ± 0.117, 1.398 ± 0.111, and 1.342 ± 0.095 were found at 1-, 3-, 6-, 9-, and 12-month follow-up, respectively. Comparison of the group with poor function recovery and the group with good function recovery showed significant differences at 6-, 9-, and 12-month follow-up (P = .035, P = .001, and P < .001, respectively), with normalizing signal intensities in the group with good function recovery and sustained high signal intensity in the group with poor function recovery. STIR MR imaging can be used to differentiate between denervated and reinnervated muscles for at least 12 months after nerve transection.

Three-dimensional expansion of a dynamic programming method for boundary detection and its application to sequential magnetic resonance imaging (MRI).

This study proposes a fast 3D dynamic programming expansion to find a shortest surface in a 3D matrix. This algorithm can detect boundaries in an image sequence. Using phantom image studies with added uniform distributed noise from different SNRs, the unsigned error of this proposed method is investigated. Comparing the automated results to the gold standard, the best averaged relative unsigned error of the proposed method is 0.77% (SNR = 20 dB), and its corresponding parameter values are reported. We further apply this method to detect the boundary of the real superficial femoral artery (SFA) in MRI sequences without a contrast injection. The manual tracings on the SFA boundaries are performed by well-trained experts to be the gold standard. The comparisons between the manual tracings and automated results are made on 16 MRI sequences (800 total images). The average unsigned error rate is 2.4% (SD = 2.0%). The results demonstrate that the proposed method can perform qualitatively better than the 2D dynamic programming for vessel boundary detection on MRI sequences.

Retraction Note: The sequential magnetic resonance images of tri-methyl tin leukoencephalopathy.

Organotin compounds are commonly used in industrial and agriculture. It causes toxic effects on skin, eyes, respiratory system, gastrointestinal system, and nervous system. After cleaning a di-methyl tin tank, 43-year-old man showed a dizziness, disorientation, visual hallucination, and agitation. Through a measurement by liquid chromatography and inductively coupled plasma-mass spectrometry, di-methyl tin and tri-methyl tin was detected. Although magnetic resonance (MR) image 3 days after exposure showed no abnormal signal intensity, follow-up MR images 15 days after exposure revealed abnormal extensive signal intensities in the white matter that was not ever coincident with previous reports. It was hardly explainable that previous abnormal signal intensities of MR image nearly disappeared 4 months later. We present a case of a patient who developed acute toxic leukoencephalopathy from an acute inhalational exposure to methyl tin with sequential MR images showing an involvement of white matter that was not ever reported.

18F-2-Deoxy-2-Fluoro-D-Glucose Positron Emission Tomography, Computed Tomography, and Magnetic Resonance Imaging for the Detection of Experimental Colorectal Liver Metastases

During the treatment of colorectal liver metastases, evaluation of treatment efficacy is of the utmost importance for decision making. The aim of the present study was to explore the ability of preclinical imaging modalities to detect experimental liver metastases. Nine male Wag/Rij rats underwent a laparotomy with intraportal injection of CC531 tumor cells. On days 7, 10, and 14 after tumor induction, sequential positron emission tomography (PET), computed tomography (CT), and magnetic resonance imaging (MRI) scans were acquired of each rat. At each time point, three rats were euthanized and the metastases in the liver were documented histologically. Topographically, the liver was divided into eight segments and the image findings were compared on a segment-by-segment basis with the histopathologic findings. Sixty-four liver segments were analyzed, 20 of which contained tumor deposits. The overall sensitivity of PET, CT, and MRI was 30%, 25%, and 20%, respectively. For the detection of tumors with a histologic diameter exceeding 1 mm (n = 8), the sensitivity of PET, CT, and MRI was 63%, 38%, and 38%, respectively. The overall specificity of PET, CT, and MRI was 98%, 100%, and 93%, respectively. This study showed encouraging detectability and sensitivity for preclinical imaging of small liver tumors and provides valuable information on the imaging techniques for designing future protocols.

Sequential Cardiac Magnetic Resonance Imaging of Acute Eosinophilic Myocarditis

Sequential Cardiac Magnetic Resonance Imaging of Acute Eosinophilic Myocarditis

Sequential magnetic resonance spectroscopic changes in a patient with nonketotic hyperglycinemia

Nonketotic hyperglycinemia (NKH) is a rare inborn error of amino acid metabolism. A defect in the glycine cleavage enzyme system results in highly elevated concentrations of glycine in the plasma, urine, cerebrospinal fluid, and brain, resulting in glycine-induced encephalopathy and neuropathy. The prevalence of NKH in Korea is very low, and no reports of surviving patients are available, given the scarcity and poor prognosis of this disease. In the current study, we present a patient with NKH diagnosed on the basis of clinical features, biochemical profiles, and genetic analysis. Magnetic resonance spectroscopy (MRS) allowed the measurement of absolute glycine concentrations in different parts of the brain that showed a significantly increased glycine peak, consolidating the diagnosis of NKH. In additional, serial MRS follow-up showed changes in the glycine/creatinine ratios in different parts of the brain. In conclusion, MRS is an effective, noninvasive diagnostic tool for NKH that can be used to distinguish this disease from other glycine metabolism disorders. It may also be useful for monitoring NKH treatment.

Sequential Magnetic Resonance Imaging Changes in Osteoporotic Compression Fractures

Sequential Magnetic Resonance Imaging Changes in Osteoporotic Compression Fractures

Gadofluorine M-enhanced Magnetic Resonance Imaging of Inflammatory Bowel Disease

: To determine the colonic mural enhancement in a rat model of inflammatory bowel disease (IBD) using gadofluorine M- and diethylenetriamine pentaacetic acid (Gd-DTPA)-enhanced magnetic resonance (MR) imaging, and to correlate the degree of enhancement with the histopathologic severity of the disease. : This study was approved by our hospital's institutional animal care and use committee. A total of 44 rats with 2 grades (mild, n = 17; and severe, n = 27) of dinitrobenzene sulfonic acid (DNBS)-induced IBD and 13 rats without IBD, were examined using a 2.4-T, small animal MR scanner. T2- and T1-weighted MR images were acquired, and sequential T1-weighted MR imaging was then performed immediately and again 15, 45, 60, and 90 minutes, and 24 hours after intravenous -injection of either gadofluorine M- or Gd-DTPA (0.1 mmol Gd/kg body weight). The signal-to-noise ratios and enhancement ratios (ER) of the colon wall were measured. For paired and group comparisons of the histopathology and MR imaging data, the Wilcoxon- and the Mann-Whitney U tests were used, and the multifactorial analysis of variance test was used to compare the time courses of the ERs. : Gadofluorine M injection resulted in significant differences in the ER of noninflamed, mildly inflamed, and severely inflamed colon wall at any time up to 24 hours after contrast injection (ER at 24 hours 2.0 ± 1.2; 10.1 ± 4.3; and 49.7 ± 10.8, respectively; P < 0.01). After Gd-DTPA injection, significant differences were observed in the ER of inflamed and noninflamed bowel at 15, 45, and 60 minutes (P < 0.01); however, no significant differences in mildly and severely inflamed bowel were observed at any time. In contrast to Gadofluorine M, there was no prolonged contrast enhancement in the inflamed colon wall after intravenous injection of Gd-DTPA (ER at 24 hours 1.6 ± 1.3; 3.4 ± 2.7; and 3.3 ± 1.6, respectively; n.s.). : Gadofluorine M-enhanced MR imaging shows a higher correlation of the wall enhancement and histopathology grading in an IBD rat model than does Gd-DTPA-enhanced imaging.

The craniocervical junction following successful haematopoietic stem cell transplantation for mucopolysaccharidosis type I H (Hurler syndrome)

Mucopolysaccharidosis I Hurler (MPS IH) is a progressive multisystemic disorder caused by alpha-L-iduronidase deficiency. First choice of treatment in MPS IH children is haematopoietic stem cell transplantation (HSCT). The effect of HSCT has been shown to have limited influence on skeletal manifestations by poor penetration of musculoskeletal tissues by the enzyme derived from donor leucocytes. Aim of this study was to investigate the effect of HSCT on the craniocervical junction (CCJ) in Hurler patients. We analysed retrospectively sequential magnetic resonance imaging (MRI) scans of 30 patients with Hurler disease treated by HSCT since 1982 at the Royal Manchester Children's Hospital, UK, in order to determine whether the patients suffer from dens hypoplasia. Results were compared with biochemical and clinical characteristics: Enzyme activity (EA), chimerism, urinary glycosaminoglycan (GAG) excretion and neurological status. Investigations were part of standard clinical procedures. Results are descriptive in presentation. In 26/30 patients a determination of odontoid hypoplasia was feasible. The majority showed a normal dens length and an increase with age. Only 3/26 revealed a dens hypoplasia. One of them had only partial donor engraftment (DE) with reduced EA, one of them suffered from chronic graft versus host disease (GVHD). One patient with only partial DE and reduced EA presented with initial dens hypoplasia until preadolescence but normalized later on. There may be a trend towards lower EA and the occurrence of DH in transplanted MPS patients - perhaps the dosage of enzyme plays a role in the correction of skeletal complications in this patient group. HSCT patients with incomplete DE and therefore lower EAs may require special attention and care.

De novo Generation of an Axially Vascularized Processed Bovine Cancellous-Bone Substitute in the Sheep Arteriovenous-Loop Model

Background/Aims: The aim of this study was to generate an axially vascularized bone substitute. The arteriovenous (AV)-loop approach in a large-animal model was applied in order to induce axial vascularization in a clinically approved processed bovine cancellous bone (PBCB) matrix of significant volume with primary mechanical stability and to assess the course of increasing axial vascularization. Methods: PBCB constructs were implanted into 13 merino sheep together with a microsurgically created AV loop in an isolation chamber. The vascularization process was monitored by sequential magnetic resonance imaging (MRI) scans. Explants were subjected to micro-computed tomography (micro-CT) analysis, histomorphometry and immunohistochemistry for CD31 and CD45. Results: Increasing axial vascularization in PBCB constructs was quantified by histomorphometry and visualized by micro-CT scans. Intravital sequential MRI scans demonstrated a significant progressive increase in perfused volume within the matrices. Immunohistochemistry confirmed endothelial lining of newly formed vessels. Conclusion: This study demonstrates successful axial vascularization of a clinically approved, mechanically stable bone substitute with a significant volume by a microsurgical AV loop in a large-animal model. Thus microsurgical transplantation of a tissue-engineered, axially vascularized and mechanically stable bone substitute with clinically relevant dimensions may become clinically feasible in the future.

MR Contrast in Mouse Lymph Nodes with Subcutaneous Administration of Iron Oxide Particles: Size Dependency

We investigated the spatiotemporal changes in signal in draining lymph nodes of mice to ascertain the size-dependent effects of variously sized particles of iron oxide used to enhance magnetic resonance (MR) lymphography. We injected iron oxide particles of 50-, 100-, 200-, or 1,000-nm diameter into the footpads of individual mice and obtained sequential MR images of the popliteal and inguinal lymph nodes with 11.7 tesla up to 6 weeks after particle administration. Up to 30 min after administration of particles smaller than 100 nm, we observed a marked reduction in signal in the popliteal node that spread from the periphery at first observation toward the center of the node in subsequent measurements and persisted up to 6 weeks. In contrast, 1,000-nm particles caused dot-like areas of hypointensity in the popliteal lymph node, primarily in the inner portion, that appeared after 2 days. In the inguinal lymph nodes, signal changes occurred after 2 days for 50- and 100-nm particles and after one week for 1,000-nm particles. For 1,000-nm particles, areas of hypointensity were visible in the inner portion and not the periphery of the inguinal lymph node up to 6 weeks. In this study, we demonstrate the strong dependence of MR imaging contrast in draining lymph nodes on the size of the particle-shaped contrast agents injected subcutaneously. Particle size represented passive and active targeting effects, so micron-sized particles produced delayed enhancement. Choosing the size of iron oxide particles for MR imaging contrast depends on the objective of observation, such as identifying the morphology or migration of immune cells in the lymph node.

Sequential Magnetic Resonance Imaging Finding of Intramedullary Spinal Cord Abscess including Diffusion Weighted Image: a Case Report

Intramedullary spinal cord abscess (ISCA) is a rare infection of the central nervous system. We describe the magnetic resonance imaging (MRI) findings, including the diffusion-weighted imaging (DWI) findings, of ISCA in a 78-year-old man. The initial conventional MRI of the thoracic spine demonstrated a subtle enhancing nodule accompanied by significant edema. On the follow-up MRI after seven days, the nodule appeared as a ring-enhancing nodule. The non-enhancing central portion of the nodule appeared hyperintense on DWI with a decreased apparent diffusion coefficient (ADC) value on the ADC map. We performed myelotomy and surgical drainage, and thick, yellowish pus was drained.

Stem Cell Dynamics in an Experimental Model of Stroke

We investigated the migration of endogenous neural stem cells (NSCs) toward an infarct lesion in a photo-thrombotic stroke model. The lesions produced by using rose bengal dye (20 mg/kg) with cold light in the motor cortex of Sprague-Dawley rats were also evaluated with sequential magnetic resonance imaging (MRI) from 30 minutes through 8 weeks. Migration of NSCs was identified by immunohistochemistry for nestin monoclonal antibody in the lesion cortex, subventricular zone (SVZ), and corpus callosum (CC). The contrast to noncontrast ratio (CNR) on MRI was greatest at 12 hours in DWI and decreased over time. By contrast, T1-weighted and T2-weighted images showed a constant CNR from the beginning through 8 weeks. MRI of the lesional cortex correlated with histopathologic findings, which could be divided into three stages: acute (edema and necrosis) within 24 hours, subacute (acute and chronic inflammatory cell infiltration) at 2 to 7 days, and chronic (gliofibrosis) at 2 to 4 weeks. The volume of the infarct was significantly reduced by reparative gliofibrosis. The number of nestin+ NSCs in the contralateral SVZ was similar to that of the ipsilateral SVZ in each group. However, the number of nestin+ NSCs in the ipsilateral cortex and CC increased at 12 hours to 3 days compared with the contralateral side (p<0.01) and was reduced significantly by 7 days (p<0.01). Active emigration of internal NSCs from the SVZ toward the infarct lesion may also contribute to decreased volume of the infarct lesion, but the self-repair mechanism by endogenous NSCs is insufficient to treat stroke causing extensive neuronal death. Further studies should be focused on amplification technologies of NSCs to enhance the collection of endogenous or transplanted NSCs for the treatment of stroke.

Use of MR Venography for Characterization of the Extracranial Venous System in Patients with Multiple Sclerosis and Healthy Control Subjects

To investigate the differences in the extracranial venous system in patients with multiple sclerosis (MS) and healthy control (HC) subjects by using magnetic resonance (MR) venography. This HIPAA-compliant, prospective study was approved by the local institutional review board, and all participants gave informed consent. Fifty-seven patients, 41 (72%) with relapsing-remitting MS and 16 (28%) with secondary-progressive MS, and 21 HC subjects were imaged with a 3-T MR unit by using two-dimensional (2D) time-of-flight (TOF) and three-dimensional (3D) time-resolved imaging of contrast kinetics (TRICKS) sequences. In addition, six MS patients and six HC subjects underwent two sequential MR venographic examinations during 1 week to test image-reimage reproducibility. The morphologic features of internal jugular vein flow were classified as absent, pinpoint, flattened, crescentic, or ellipsoidal flow. Only absent and pinpoint flow were considered abnormal. The flow of the vertebral veins was classified as absent or present. The prominence of collateral neck veins and venous asymmetries between the left and right sides were assessed. Differences among groups were tested with a two-tailed Mann-Whitney two-sample rank-sum test. No significant differences in morphologic features of flow in the internal jugular veins and vertebral veins were found between MS patients and HC subjects in any of the examined MR venographic parameters. No differences in asymmetry or prominence were found between MS patients and HC subjects. There was modest agreement (κ = 0.67) between 2D TOF and 3D TRICKS sequences. Image-reimage reproducibility showed modest agreement (κ = 0.66) for 2D TOF and low agreement for 3D TRICKS (κ = 0.33). No significant differences in the extracranial venous systems between MS patients and HC subjects were detected by using MR venography. Standardized guidelines are needed to define parameters for the presence of venous anomalies.

Focal Hepatic Steatosis That Appears as a Liver Mass in Imaging

f i f A man with heavy alcohol history (daily alcohol ingestion of 160 g for 25 years) presented for evaluation of cteric sclera and epigastric pain. Initial laboratory data were as ollows: white blood cell count, 10,500; hemoglobin, 14.3; plateet count, 121,000; aspartate aminotransferase/alanine aminoransferase, 325/66 IU/L; bilirubin level (total/direct), 26.4/12.8 g/dL; alkaline phosphatase, 177 IU/L; -guanosine triphosphate, 670 IU/L. Tumor markers (alpha-fetoprotein, carcinoembryonic antigen, protein induced by vitamin K absence or antagonist II) were within normal limits except carcinoembryonic antigen 199, 418.3 IU/mL. The computed tomography scan (Figure A) revealed hepatosplenomegaly and surface undulation of the liver, which represent alcoholic liver cirrhosis, and large bulging mass-like lesions (arrowheads) at segments I, IV, and V of the liver. Ascites was also noted. Sequential magnetic resonance imaging revealed mass-like enlargement of hepatic segments I, IV, and V, which were hyperintense on the in-phase (Figure B) and hypointense on opposed-phase (Figure C) chemical shift gradient echo images. These mass-like lesions showed no enhancement on contrast-enhanced dynamic studies. Ultrasonography-guided liver biopsy was performed with an 18-gauge gun needle. Obtained hepatic specimen included the area of hyperechoic mass-like lesion and adjacent hepatic parenchyma in segment V. Following pathologic examinations proved scattered neutrophils, severe fatty liver with hepatocyte swelling, and massive bilirubin pigment, which are consistent with alcoholic steatohepatitis (Figure D). Hepatic steatosis is frequently manifested in alcoholic liver disease with or without alcoholic hepatitis or cirrhosis. Even though the biopsy is considered the reference standard for assessment of hepatic steatosis, most patients do not undergo liver biopsy but are usually diagnosed as hepatic steatosis with ultrasonography.1 Ultrasonography is known as a routine noninvasive technique for the initial study of the liver in various clinical circumstances, but it still has severe diagnostic limitations, both in diffuse liver disease and in focal hepatic steatosis, that might lead to a misdiagnosis of hepatic mass.2 Especially in alcoholic liver disease, focal well-marginated fat deposit can be frequently diagnosed as hepatocellular carcinoma or its premalignant lesions such as regenerative or dysplastic nodules.1 Focal fatty deposition of the liver is usually a benign lesion that is developed by aberrant venous supply or focal metabolic change caused by perfusion decrease. It is usually represented as illdefined low attenuating lesions on computed tomography scan. For assessment of fatty accumulation of the liver, magnetic resonance imaging is widely used including chemical shift gradient echo imaging with in-phase and opposed-phase acquisitions.1,2 Hepatic steatosis might be present if there is a signal intensity loss on opposed-phase images in comparison with in-phase images, and the amount of hepatic fat present can also be quantified by assessing the degree of signal intensity loss.1 We can usually find the normal vascular structure that passes through the focal fatty deposition without distortion in contrast to true tumorous lesion (arrows in Figure A). Unlike at-containing lesions in other organs, the application of chemcal fat saturation sequences can be neither sensitive nor specific or the detection of fatty liver.1,2

Effects of Contrast Agent on Water Suppression and Shimming of Kidney Single-Volume Proton MR Spectroscopy at 3.0T

The aim of this study was to determine whether the administration of gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) significantly affects shimming and water suppression on kidney magnetic resonance spectroscopic prescanning and whether the impact of shimming and water suppression is changed with time after intravenous administration on a 3.0-T system. Forty patients (two patients were excluded from analysis because of motion) were examined before and after the administration of Gd-DTPA (the interval between the right and left kidneys was approximately 40 seconds). Regions of interest were carefully positioned in the region of the corresponding location of both kidneys separately. Line widths (full width at half maximum) and water suppression were obtained. A paired t test for comparison of means was used. In addition, repeat measurements with a shorter time interval (obtained 120-130 seconds after the injection) and a longer time interval (obtained 150-160 seconds after the injection) were performed in five patients in the same regions of interest of the right kidney. Sequential ¹H magnetic resonance spectroscopic prescanning in the same region of interest was performed in one patient. The left kidney had slightly better shimming and water suppression effects than the right kidney after contrast agent administration (all P values < .01). The limiting resolution of both shimming and water suppression effects was decreased on enhanced images in both kidneys (all P values < .01). The longer time interval group had better shimming and water suppression effects than the shorter time interval group (all P values < .01). After the administration of Gd-DTPA in one patient, sequential values of shimming and water suppression in the right and left kidneys, respectively, were 13 Hz and 97% and 12 Hz and 97% prior to the examination, 34 Hz and 86% and 30 Hz and 88% at 5 minutes, 32 Hz and 89% and 27 Hz and 90% at 10 minutes, 28 Hz and 91% and 24 Hz and 91% at 15 minutes, and 24 Hz and 92% and 20 Hz and 92% at 25 minutes. Gd-DTPA exerts adverse effects on water suppression and shimming, both of which show a trend of becoming well gradually with time extension after the injection of Gd-DTPA. This phenomenon limits the diagnostic use of kidney magnetic resonance spectroscopy performed immediately after contrast-enhanced magnetic resonance imaging.

Dynamic Contrast-Enhanced Magnetic Resonance Imaging Evaluation of VX2 Carcinoma in a Rabbit Model

To compare the enhancement characteristics and diagnostic performance of 1.0-M gadobutrol with those of 0.5-M gadopentetate dimeglumine in rabbit VX2 tumor models. Our study was approved by the Animal Care Committee of our hospital. VX2 carcinomas were implanted in both thighs of 14 rabbits 4 days before magnetic resonance (MR) imaging. The animals underwent 2 identical MR examinations with 2 different contrast media separated by 8 hours with the use of a 3.0 T magnet. T2-, T1- weighted fast spin echo images were obtained. Sequential MR imaging with the 3-dimensional-SPGR sequence were performed before and at 1, 2, 3, 4, 5, 10, 15, 20, and 30 minutes after injection of 0.05 mmol/kg of 1.0-M gadobutrol or 0.5-M gadopentetate dimeglumine. Four rabbits without tumor implantation underwent the same MR examinations. Percentage enhancement of the tumor was assessed by 2 radiologists in consensus. Three different readers without knowledge of the histopathologic results interpreted both MR images in terms of presence of tumor. Receiver operating characteristic analysis was conducted to compare the diagnostic value of both contrast agents. Sensitivities and specificities were also calculated. In addition, lesion-to-muscle contrast, degree of lesion delineation, and global preferences of the readers were determined using a scoring system. A total of 56 VX2 tumors were identified by histopathologic review. For the VX2 tumors, the percentage enhancement at each time point was consistently higher with injection of 1.0-M gadobutrol than with injection of 0.5-M gadopentetate dimeglumine (P < 0.01). The area under the receiver operating characteristic curve (Az) values for the use of 1.0-M gadobutrol-enhanced MR imaging were 0.937, 0.886, and 0.938 for readers 1, 2, and 3, respectively. The Az values for the use of 0.5-M gadopentetate dimeglumine-enhanced MR imaging were 0.908, 0.903, and 0.947. Sensitivities were 89.3%, 85.7%, and 89.3% for 1.0-M gadobutrol-enhanced MR imaging and 87.5%, 85.7%, and 89.3% for 0.5-M gadopentetate dimeglumine-enhanced MR imaging. Specificities were 87.5%, 75.0%, and 87.5% for 1.0-M gadobutrol-enhanced MR imaging and 100%, 81.3%, and 100% for 0.5-M gadopentetate dimeglumine-enhanced MR imaging. No significant differences were noted for the Az values, sensitivities, and specificities with the use of the 2 contrast agents. Lesion-to-muscle contrast, degree of lesion delineation, and global preferences of the readers were ranked significantly higher for 1.0-M gadobutrol-enhanced MR imaging in all readers (P < 0.001). Using a 3.0-T magnet, equivalent doses of 1.0-M gadobutrol-enhanced MR imaging showed a superior degree of enhancement for a VX2 tumor than 0.5-M gadopentetate dimeglumine-enhanced MR imaging, and a significant preference for readers was noted for 1.0-M gadobutrol-enhanced MR imaging.