Purpose: Signal intensity (SI) and image contrast on postmortem magnetic resonance (MR) imaging are different from those of imaging of living bodies. We sought to suppress the SI of cerebrospinal fluid (CSF) sufficiently for fluid-attenuated inversion recovery (FLAIR) sequence in postmortem MR (PMMR) imaging by optimizing inversion time (TI). Materials and Methods: We subject 28 deceased patients to PMMR imaging 3 to 113 hours after confirmation of death (mean, 27.4 hrs.). PMMR imaging was performed at 1.5 tesla, and T1 values of CSF were measured with maps of relaxation time. Rectal temperatures (RT) measured immediately after PMMR imaging ranged from 6 to 32°C (mean, 15.4°C). We analyzed the relationship between T1 and RT statistically using Pearson’s correlation coefficient. We obtained FLAIR images from one cadaver using both a TI routinely used for living bodies and an optimized TI calculated from the RT. Results: T1 values of CSF ranged from 2159 to 4063 ms (mean 2962.4), and there was a significantly positive correlation between T1 and RT (r = 0.96, P < 0.0001). The regression expression for the relationship was T1 = 74.4 * RT + 1813 for a magnetic field strength of 1.5T. The SI of CSF was effectively suppressed with the optimized TI (0.693 * T1), namely, TI = 0.693 * (77.4 * RT + 1813). Conclusion: Use of the TI calculated from the linear regression of the T1 and RT optimizes the FLAIR sequence of PMMR imaging.
Purpose: We measured the volume of the endolymphatic space by extending a previously proposed less observer-dependent method of area quantification and compared volume measurements obtained using long (18 min, Image A) and short (8 min, Image B) scan times. Methods: We performed MR imaging of 40 ears in 20 patients with clinically suspected endolymphatic hydrops 4 hours after intravenous administration of single-dose gadolinium-based contrast material (IV-SD-GBCM). Two observers separately measured the ratio of the volume of the endolymph to that of total lymph in the cochlea and vestibule by extending the area ratio measurement method previously reported (Image A and B). The correlation between the values by Image A and B was calculated. Results: We observed a strong linear correlation between Images A and B in the cochlear images; the Pearson’s correlation coefficient (r) was 0.928 for Observer A and 0.926 for Observer B (P < 0.001, for all). A strong linear correlation was also observed in the vestibular images; the Pearson’s correlation coefficient (r) was 0.962 for Observer A and 0.968 for Observer B (P < 0.001, for all). Conclusion: Measurement of endolymphatic volume after IV-SD-GBCM may be feasible using an MR imaging protocol with a reduced scan time of 8 min. This method might facilitate greater use of endolymphatic hydrops imaging in clinical applications.
Purpose: We compared the depiction of pulsatile CSF motion obtained by 4-dimensional phase-contrast velocity mapping (4D-VM) with that by time-spatial labeling inversion pulse (time-SLIP) technique in the presence of membrane structures. Materials and Methods: We compared the 2 techniques using a flow phantom comprising tubes with and without a thin rubber membrane and applied the techniques to 6 healthy volunteers and 2 patients to analyze CSF dynamics surrounding thin membrane structures, such as the Liliequist membrane (LM), or the wall of an arachnoid cyst. Results: Phantom images exhibited propagation of the flow and pressure gradient beyond the membrane in the tube. In contrast, fluid labeled by the time-SLIP technique showed little displacement from the blockage of spin travelling by the membrane. A similar phenomenon was observed around the LM in healthy volunteers and the arachnoid cyst wall in a patient. Conclusion: Four-dimensional phase-contrast velocity mapping permitted visualization of the propagation of CSF pulsation through the intracranial membranous structures. This suggests that 4D-VM and the time-SLIP technique provide different information on flow and that both techniques are useful for classifying the pathophysiological status of CSF and elucidating the propagation pathway of CSF pulsation in the cranium.
Purpose: The role of early stage functional assessment of muscle blood flow response (MFR) by dynamic muscle blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging is unknown. We investigated the effect of smoking on vascular function according to MFR derived from dynamic muscle BOLD MR imaging during postocclusive reactive hyperemia in young smokers and nonsmokers. Methods: Sixteen healthy male volunteers (8 smokers, 8 nonsmokers; mean age, 30.4 ± 4.6 years) underwent BOLD MR imaging of the left calf muscle. During reactive hyperemia provoked by a cuff-compression technique, we measured muscle BOLD (mB) using a 3-tesla single-shot multi-echo gradient-echo echo-planar imaging sequence. The 2 key mB variables in the reactive hyperemic phase that we studied were times to half hyperemic peak (T1/2peak) and peak (TTP), each measured from cuff deflation. We used the Welch test to assess differences in these between smokers and nonsmokers. Results: T1/2peak and TTP were significantly longer in smokers (P < 0.05) in reactive hyperemia. T1/2peak was 13.8 ± 5.4 s in smokers and 7.6 ± 1.5 s in nonsmokers, and TTP was 67.5 ± 18.8 s in smokers and 45.4 ± 7.1 s in nonsmokers. Conclusion: Dynamic BOLD MR imaging of calf muscle during postocclusive reactive hyperemia demonstrated statistically significant differences in T1/2peak and TTP between young smokers and nonsmokers, indicating the presence of early stage smoking-related deterioration in MFR.
Purpose: We compared gross characterization of intracranial dural arteriovenous fistulas (DAVFs) between unenhanced 3-tesla 3-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) and digital subtraction angiography (DSA). Methods: We subjected 26 consecutive patients with intracranial DAVF to unenhanced 3T 3D TOF MRA and to DSA. Two independent sets of observers inspected the main arterial feeders, fistula site, and venous drainage pattern on MRA and DSA images. Interobserver and intermodality agreements were assessed by k statistics. Results: Interobserver agreement was excellent for fistula site (κ = 0.919; 95% confidence interval [CI], 0.805 to 1.000), good for main arterial feeders (κ = 0.711; 95% CI, 0.483 to 0.984), and very good for venous drainage (κ = 0.900; 95% CI, 0.766 to 1.000). Intermodality agreement was excellent for fistula site (κ = 0.968; 95% CI, 0.906 to 1.000) and good for main arterial feeder (κ = 0.809; 95% CI, 0.598 to 1.000) and venous drainage (κ = 0.837; 95% CI, 0.660 to 1.000). Conclusion: Gross characterization of intracranial DAVF was similar for both imaging modalities, but unenhanced 3T 3D TOF MRA cannot replace DSA.
Objectives: We retrospectively compared and quantified magnetic resonance (MR) images to distinguish major histological types of uterine sarcomas and malignant and benign tumors. Methods: MR images were obtained from patients who underwent preoperative examinations. We compared 25 pathologically confirmed uterine sarcomas (8 leiomyosarcomas, 11 carcinosarcomas, 6 endometrial stromal sarcomas) with 25 uterine leiomyomas. MR findings included tumor size, location, contour, signal intensity (SI), and contrast enhancement. Analysis focused on the contrast ratio (CR) of SI in T2-weighted images for the areas of lowest, highest, and main SI of each tumor as well as the contrast-enhanced ratio (CER) for the main solid part of each tumor in contrast-enhanced T1-weighted images. We evaluated diffusion-weighted (DW) images and apparent diffusion coefficient (ADC) values in 18 tumors (4 sarcomas, 14 leiomyomas). Results: Uterine sarcomas and leiomyomas differed significantly in tumor location, contour, hemorrhaging, necrotic and cystic components, CR for the area of lowest SI (P < 0.05), CR for the area of main SI (P < 0.01), and CER (P < 0.05). Leiomyosarcomas were larger than carcinosarcomas or endometrial stromal sarcomas, and the CR for the area of lowest SI of leiomyosarcomas (P < 0.05) was significantly lower. The CER for endometrial stromal sarcomas (P < 0.05) showed the most homogeneous enhancement. Hemorrhagic or necrotic and cystic components were found more often in larger tumors, although there was no significant difference in their occurrence between sarcoma types. All uterine sarcomas showed high intensity on DW images. The ADC values were lower of uterine sarcomas than leiomyomas, although the difference was not statistically significant. Conclusion: Quantitative assessment using the CR or CER was useful for distinguishing benign and malignant uterine tumors as well as major histological types of uterine sarcomas.
Purpose: The brain produces intense heat as a result of cerebral metabolism and cerebral blood flow, and the generated heat is removed mainly through circulation of the intracranial blood vessels and cerebrospinal fluid (CSF). Because magnetic resonance (MR) images are constructed from analysis of the spin of various molecules, the diffusion coefficient can be used as a parameter that reflects the temperature of water molecules. We used diffusion-weighted imaging (DWI)-based MR imaging to measure the temperature of the CSF around the lateral ventricles in patients with idiopathic normal pressure hydrocephalus (iNPH). Methods: Our study included 33 cases of iNPH (Group N, mean age, 75.1 years) and 40 age-matched controls (Group C, mean age, 74.5 years). We calculated CSF temperature in the ventricular domain using the conversion formula to evaluate the feasibility of iNPH study. Results: The mean temperatures were significantly higher in Group N (37.6°C ± 0.4°C) than Group C (36.7°C ± 0.5°C; P < 0.01). The cut-off value of 37.2°C (more than the mean + 2 standard deviations [SD] of the values in Group C) showed sensitivity of 72.4% and specificity of 77.5% for distinguishing the 2 groups. We confirmed improved CSF temperature in the lateral ventricles in all patients examined both before and after shunting. Conclusions: Elevated ventricular temperatures in patients with iNPH (Group N) may represent a disturbance in heat balance. Our results showed that thermometry using DWI-based MR imaging can help in the noninvasive and consistent evaluation of CSF temperature and may thus provide a useful supplementary brain biomarker for iNPH.
Purpose: In the imaging of intra-axial brain tumors, we sometimes found areas of high signal intensity around the enhanced tumor lesions on arterial spin labeling (ASL) magnetic resonance (MR) imaging. We undertook this study to investigate the relationship between high signal intensity on ASL imaging outside the area of contrast enhancement (CE) and histological diagnosis of intra-axial brain tumors. Methods: We examined images from 28 consecutive patients with intra-axial brain tumors who underwent ASL and CE MR imaging–three with low grade glioma (LGG), 13 with high grade glioma (HGG), six with metastasis, and six with primary central nervous system lymphoma (PCNSL)–and divided imaging findings into an “ASL dominant” group when hyperintensity on ASL was found outside the CE area and a “CE dominant” group when hyperintensity on ASL was not found outside the area of enhancement. We then analyzed the relationship between imaging findings and the histological diagnosis of the tumors. Results: Four cases were excluded because of poor quality of ASL images, 7 cases were classified as ASL dominant, and 17 cases were classified as CE dominant. The histological diagnoses of ASL dominant cases were LGG in 3 cases, HGG in 3 cases, and PCNSL in one case. Those of CE dominant cases were HGG in 10 cases, metastasis in 5 cases, and PCNSL in 2 cases. All cases with brain metastasis were classified as CE dominant. Conclusion: The high signal intensity outside the area of contrast enhancement is probably caused by increased perfusion or vascular proliferation, which indicates the presence of glioma or PCNSL and not metastasis. This finding indicates a new utility for ASL images in the diagnosis of brain tumors as a supplement to the conventional measurement of perfusion obtained from ASL images.
Purpose: After cranioplasty with a titanium mesh, radiofrequency (RF)-shielding images appear during magnetic resonance (MR) imaging. To clarify their influence, we evaluated the effect of mesh position, phase-encoding direction, and type of coil employed. Materials and Methods: On a 1.5-tesla MR imager, we placed a titanium mesh board (100 × 100 × 0.8 mm) on the surface of a cubic phantom to mimic a human brain and used a quadrature coil and an 8-channel neurovascular coil to measure nonuniformity, signal decay ratio, and the B1 map. Results: Nonuniformity was 6.7 times higher at the quadrature head coil and 1.6 times higher at the neurovascular coil when the mesh was on the phantom’s right side or anterior to it than when it was on its superior end or absent. The profile of the signal decay ratio increased by 1.9% mm−1 from 0 to 40 mm from the mesh side to the base value at the quadrature head coil when the mesh was on the phantom’s right side and 0.9% mm−1 from 0 to 80 mm at the neurovascular coil when the mesh was on the phantom’s right side or anterior to it. The quadrature head coil showed greater incline of the profile when the mesh was on the right in coronal and axial views and no notable change in the profile in coronal and sagittal views when the mesh was on the superior end. In the B1 map, the flip angle was lower when the mesh was nearer. Conclusion: The response to the RF-shielding effect from a titanium mesh depends on the location of the mesh and the RF coil used but not on the phase-encoding direction.
Objectives: Obsessive-compulsive disorder (OCD) is one of the most debilitating psychiatric disorders, with some speculating that a reason for difficulty in its treatment might be its coexistence with autism spectrum. We investigated the tendency for autistic spectrum disorders (ASD) in patients with OCD from a neuroimaging point of view using voxel-based morphometry. Methods: We acquired T1-weighted images from 20 patients with OCD and 30 healthy controls and investigated the difference in regional volume between the groups as well as the correlation between Autism-Spectrum Quotient (AQ) scores and regional cerebral volumes of patients with OCD. Results: Volumes in the bilateral middle frontal gyri were significantly decreased in patients with OCD compared to controls. Correlational analysis showed significant positive correlations between AQ scores and regional gray matter (GM) volumes in the left dorsolateral prefrontal cortex (DLPFC) and left amygdala. Furthermore, GM volumes of these regions were positively correlated with each other. Conclusions: The positive correlation of ASD traits in patients with OCD with regional GM volumes in the left DLPFC and amygdala could reflect the heterogeneity of patient symptoms. Our results suggest that differences in GM volume might allow classification of patients with OCD for appropriate therapy based on their particular traits.
Purpose: Recent publications have reported contradictory results of pretreatment diffusion-weighted magnetic resonance imaging (DWI) for the prediction of chemoradiotherapeutic response in primary squamous cell carcinomas of the head and neck (HNSCC). Therefore, we evaluated the diagnostic performance of DWI obtained with both standard (b = 0 and 1,000 s/mm2) and high (b = 0 and 2,000 s/mm2) b-values for predicting response to induction chemotherapy in HNSCCs. Methods: For 25 patients with primary HNSCC who underwent DWI with both standard and high b-values prior to treatment, we calculated corresponding apparent diffusion coefficient (ADC) maps. Regions of interest containing the tumor were drawn on every section of ADC maps and summated to make volume-based data of the entire tumor. Histogram parameters (mean ADC, kurtosis, and skewness) were correlated with treatment response using unpaired Student t test. Univariate and multivariate analysis of the ADC parameters, patient age, sex, whole tumor volume, and T stage were also performed to predict tumor response to induction chemotherapy. Results: Response to induction chemotherapy was good in 13 of the 25 patients and poor in 12. The mean ADC values of good responders at standard b-value (ADC1000), 1.23 ± 0.34 (× 10−3 mm2/s), and high b-value (ADC2000), 0.62 ± 0.14 (× 10−3 mm2/s), were lower than those of poor responders (ADC1000, 1.32 ± 0.28 [× 10−3 mm2/s]; ADC2000, 0.76 ± 0.15 [× 10−3 mm2/s]), but significant difference was achieved only at the ADC2000 map (P = 0.02). In addition, mean tumor volume prior to treatment of good responders was smaller than that of poor responders. However, at multiple logistic regression analysis, only the mean ADC2000 value remained as a significant predictor of response to induction chemotherapy. Conclusion: DWI with high b-values (b = 0 and 2,000 s/mm2) as an assessment of ADC values may help predict tumor response to neoadjuvant chemotherapy for primary HNSCCs.
A 74-year-old woman underwent contrast-enhanced (CE) computed tomography (CT) that revealed an enlarging splenic lesion. This splenic tumor was suspected as metastasis because the patient had been diagnosed with right breast cancer with lung and right axillary lymph node metastases 4 years earlier and had undergone surgery and hormone therapy at another hospital. T2-weighted imaging of magnetic resonance (MR) imaging demonstrated the tumor with slightly high intensity with a rim of low intensity at the margin. On dynamic contrast-enhanced (DCE)-MR imaging after intravenous administration of gadolinium diethylenetriamine pentaacetic acid, delayed enhancement was observed in the center and margin of the tumor. On positron emission tomography with 2-deoxy-2-[18F] fluoro-D-glucose (FDG) integrated with CT, the tumor showed high FDG uptake. Splenic metastasis was considered based on the imaging findings, lack of inflammation on laboratory data, and clinical course, so she underwent splenectomy. Histopathologically, the tumor was encapsulated by a fibrous structure, which was depicted as the rim at the tumor margin on T2-weighted imaging and DCE-MR imaging. Immunohistochemical study allowed the diagnosis of inflammatory pseudotumor (IPT)-like follicular dendritic cell tumor (FDCT). FDCT is a primary neoplasm of lymph nodes that shows features of follicular dendritic cell differentiation, and it is rare at the spleen. Differential diagnosis is difficult between IPT-like FDCT and similar splenic tumors, such as IPT, splenic metastases, hamartoma and hemangioma. However, in addition to the enhancement pattern within a tumor on DCE-MR imaging, detection of the capsular-like rim on MR imaging might aid the diagnosis of splenic IPT-like FDCT.
We report findings of magnetic resonance imaging including susceptibility-weighted imaging (SWI) of the subacute torsion of an ovarian fibrothecoma in a patient with renal dysfunction. Although venous thrombosis within the vascular pedicle mimicked a malignant tumor, showing high signal intensity on T2-weighted images and diffusion-weighted imaging, we diagnosed ovarian torsion on SWI without the administration of contrast medium, aided by the prominent susceptibility-induced signal void caused by the thrombosis.
We constructed an arm holder for muscle exercise from a forearm-shaped plastic shell and magnetic resonance (MR) imaging position markers and determined the echo time (39 ms) for T2-weighted spin-echo MR imaging from T2 values of the exercised (50 ms) and resting (32 ms) muscle at 0.2 tesla. The smallest detectable muscle was the extensor digiti minimi muscle (cross-sectional area 25 mm2). This combination could be useful to monitor finger exercise in patients undergoing physical therapy.
Delayed-enhancement magnetic resonance imaging (DE-MRI) is reported to detect the radiofrequency (RF) ablation scar of pulmonary vein isolation. However, the precise localization of RF scar is difficult to recognize due to the poor anatomical information of the 3-dimensionally reconstructed DE-MRI. We report 2 cases in which fusion of DE-MRI and contrast-enhanced MR angiography facilitated the identification of RF scar, and we detail our fusion method.