Proton Density-weighted Magnetic Resonance Imaging Research Articles

Combined with diffusion tensor imaging and proton density-weighted magnetic resonance imaging on the visual pathwav of central nervous system in patients with glaucoma

[Objective] To observe the changes of visual pathway of central nervous system in patients with glaucoma.[Methods] Thirty-five subjects were enrolled in this prospective study.There were seven patients of chronic primary angle-closure glaucoma with bilateral visual field defects,12 patients of primary open angle glaucoma with bilateral visual field defects,and 16 normal subjects.GE Signa HD 1.5 T magnetic resonance scanners and head eight phased array were used.The mean fractional anisotropy (FA)and the mean average diffusion coefficient (DCavg) of white matter tracts in visual pathway of bilateral optic nerve,optic chiasma,bilateral optic tract,bilateral optic radiation were measured by diffusion tensor imaging,meanwhile the white matter tracts were reconstructed by fiber tracking system,The volumes of lateral geniculate body were measured by coronal proton density-weighted magnetic resonance imaging.[Results] The differences of FA among bilateral optic nerve,optic chiasma,bilateral optic tract,bilateral optic radiation were statistically significant (F =25.985,20.626,12.262,22.399,21.708,24.994,22.774; P＜0.05).There was no difference of DCavg among bilateral optic nerve,optic chiasma,bilateral optic tract,bilateral optic radiation(F=2.097,2.178,0.530,0.983,0.608,0.866,1.504; P＞0.05).The differences of volume of lateral geniculate body among three groups were statistically significant (F=18.631,17.274; P＜0.05).[Conclusion] There is degeneration in visual pathway of central nervous system in patients with glaucoma. Key words: Glaucoma/diagnosis; Central nervous system/radionuclide imaging; Magnetic resonance imagingy

Validation of a Novel Semiautomated Segmentation Method for MRI Detection of Cartilage-Related Bone Marrow Lesions.

Objective:To determine the relationship of bone marrow lesions (BMLs) with phenomena such as clinical symptoms, histological subchondral bone damage, and development of osteoarthritis, a reliable and reproducible method to localize and quantify BMLs accurately is indispensable. Therefore, the goal of the current study was to develop and validate a novel semiautomated segmentation method based on the KNN classification technique on T2-weighted (T2w) SPIR and proton density-weighted (PDw) magnetic resonance images (MRIs), as this would provide an accurate, reliable, and reproducible tool.Materials and Methods:Twenty PDw and T2w SPIR MRIs were selected and manually segmented as a learning set for the software system. The manual segmentations were considered the gold standard. Automated segmentation based on the KNN classification technique was carried out on the same MRIs. To determine the accuracy and validity of the system, the automated segmentations were compared to the gold standard using the Dice Similarity Index (DSI).Results:The KNN classification system resulted both visually and statistically in an accurate segmentation of BMLs on T2w SPIR MRIs with an excellent mean optimal DSI of 0.702 (±0.202; range, 0.409-0.908). Elimination of specific areas smaller than 10 voxels improved the accuracy. The accuracy was independent of BML size. The segmentation of BMLs on PDw MRIs was less reliable with a mean optimal DSI of 0.536 (±0.156).Conclusion:Although the applicability of this method is limited on PDw MRIs, the KNN classification system provides an accurate, reliable, and reproducible tool for semiautomated segmentation of BMLs in T2w SPIR MRIs of the knee.

Magnetic resonance histologic correlation in rotator cuff tendons

To relate histologic changes in rotator cuff tendons to the appearance on T1-weighted as well as fat-suppressed T2-weighted and proton density-weighted magnetic resonance imaging (MRI) sequences. T1-weighted, fat-suppressed T2-weighted and fat-suppressed proton density-weighted sequences of 18 cadaveric shoulders were acquired. The supraspinatus, infraspinatus, and subscapularis tendons were evaluated histologically. Twenty-six abnormalities were found in 23 of 37 tendons. In addition, histologically normal tendon parts (n = 32), including three segments with normal histology but abnormal MR signal, considered to represent magic angle effects, were defined. All regions of interest (ROIs) were evaluated by two musculoskeletal radiologists independently and blinded to histology. In the 26 areas with anatomically intact tendons but abnormal histological findings mucoid degeneration (n = 13), chondroid metaplasia (n = 11), fatty infiltration (n = 1), and foreign-body granuloma (n = 1) after tendon suture were found. Compared to normal tendon, mucoid degeneration was hyperintense on T2-weighted fat-suppressed (P = 0.007) and on proton density-weighted fat-suppressed images (P = 0.006). Chondroid metaplasia was hyperintense compared to normal tendon in all sequences (P < 0.05). Mucoid degeneration was hypointense compared to chondroid metaplasia on T2-weighted fat-suppressed images (P = 0.038) and hypointense compared to magic angle artifacts on T1-weighted images (P = 0.046). Chondroid metaplasia of rotator cuff tendons appears to be more common than expected. Both mucoid degeneration and chondroid metaplasia may explain increased tendon signal on MR images of the rotator cuff.

Differentiation between grade 3 and grade 4 articular cartilage defects of the knee: Fat-suppressed proton density-weighted versus fat-suppressed three-dimensional gradient-echo MRI

Fat-suppressed (FS) proton density (PD)-weighted magnetic resonance imaging (MRI) and FS three-dimensional (3D) gradient-echo imaging such as spoiled gradient-recalled (SPGR) sequence have been established as accurate methods for detecting articular cartilage defects. To retrospectively compare the diagnostic efficacy between FS PD-weighted and FS 3D gradient-echo MRI for differentiating between grade 3 and grade 4 cartilage defects of the knee with arthroscopy as the standard of reference. Twenty-one patients who had grade 3 or 4 cartilage defects in medial femoral condyle at arthroscopy and knee MRI were included in this study: grade 3, >50% cartilage defects; grade 4, full thickness cartilage defects exposed to the bone. Sagittal FS PD-weighted MR images and FS 3D gradient-echo images with 1.5 T MR images were independently graded for the cartilage abnormalities of medial femoral condyle by two musculoskeletal radiologists. Statistical analysis was performed by Fisher's exact test. Inter-observer agreement in grading of cartilage was assessed using kappa coefficients. Arthroscopy revealed grade 3 defects in 17 patients and grade 4 defects in 4 patients in medial femoral condyles. For FS 3D gradient-echo images grade 3 defects were graded as grade 3 (n=15) and grade 4 (n=2), and all grade 4 defects (n=4) were correctly graded. However, for FS PD-weighted MR images all grade 3 defects were misinterpreted as grade 1 (n=1) and grade 4 (n=16), whereas all grade 4 defects (n=4) were correctly graded. FS 3D gradient-echo MRI could differentiate grade 3 from grade 4 defects (P=0.003), whereas FS PD-weighted imaging could not (P=1.0). Inter-observer agreement was substantial (kappa=0.70) for grading of cartilage using FS PD-weighted imaging, whereas it was moderate (kappa=0.46) using FS 3D gradient-echo imaging. FS 3D gradient-echo MRI is more helpful for differentiating between grade 3 and grade 4 cartilage defects than is FS PD-weighted imaging.

Gadolinium toxicity: epidermis thickness measurement by magnetic resonance imaging at 500 MHz

Regional epidermal thickening and hair follicle width measurement by delayed gadolinium contrast magnetic resonance imaging (MRI) may assess the contrast agent gadolinium toxicity on mice skin. Delayed contrast in vivo MRI was performed in mice. Six mice skin samples were removed and exposed to a gadolinium contrast agent at different times after 2, 4, 6 and 8 h. The relaxation constants of each skin structure were measured. The thickness of the epidermis and hair follicle on follow-up ex vivo delayed-contrast MRI served as an index of gadolinium toxicity on the skin. In vivo MRI by fast low-angle shot imaging technique showed distinct skin layers. High-resolution gradient echo T1-weighted and multislice multiecho proton density-weighted MRI intensities in the epidermis and hair follicle showed a positive correlation with delayed gadolinium-enhanced MRI hyperintensities (Pearson's correlation coefficient r(2)=0.81, P<0.0001) in the excised mice skin tissues. Delayed contrast-enhanced mice skin MRI after 2-4 h showed epidermis swelling and hair follicle regions with a size measurement accuracy of 65%, a sensitivity of 95%, a specificity of 25%, a positive predictive value of 65% and a negative predictive value of 65%. Areas under the receiver operating characteristic curves by MRI were 0.92-0.94 for hair and epidermis as good discriminators. MRI visualized distinct relaxation constants of the epidermis, sebaceous gland, skin papillary and reticular dermis layers and hair follicle. Gadolinium contrast-enhanced MRI may visualize the thickening of the epidermis wall and hair follicle as an index of viable mice skin. Gadolinium enhanced the MRI visibility of skin structures. Gadolinium treatment showed skin toxicity as epidermis thickening the first time due to the undesirable use of high concentrations of gadolinium in microimaging.

Patterns of White Matter Atrophy in Frontotemporal Lobar Degeneration

Structural magnetic resonance imaging (MRI) has been used to investigate the in vivo pathology of frontotemporal lobar degeneration. However, few neuroimaging studies have focused on white matter (WM) alterations in this disease. To use volumetric MRI techniques to identify the patterns of WM atrophy in vivo in 2 clinical variants of frontotemporal lobar degeneration-frontotemporal dementia (FTD) and semantic dementia-and to compare the patterns of WM atrophy with those of gray matter (GM) atrophy in these diseases. Structural MRIs were obtained from patients with FTD (n = 12) and semantic dementia (n = 13) and in cognitively healthy age-matched controls (n = 24). Regional GM and WM were classified automatically from high-resolution T1-, T2-, and proton density-weighted MRIs with Expectation-Maximization Segmentation and compared between the groups using a multivariate analysis of covariance model that included age and WM lesion volumes as covariates. Patients with FTD had frontal WM atrophy and frontal, parietal, and temporal GM atrophy compared with controls, who had none. Patients with semantic dementia had temporal WM and GM atrophy and patients with FTD had frontal GM atrophy. Adding temporal WM volume to temporal GM volume significantly improved the discrimination between semantic dementia and FTD. These results show that patients with frontotemporal lobar degeneration who are in relatively early stages of the disease (Clinical Dementia Rating score, 1.0-1.2) have WM atrophy that largely parallels the pattern of GM atrophy typically associated with these disorders.

Anatomy and MR imaging appearances of synovial plicae of the knee.

Synovial plicae are normal anatomic structures of the knee that sometimes become symptomatic. Magnetic resonance (MR) imaging and MR arthrography are useful tools in the evaluation of synovial plicae and allow differentiation of these entities from other causes of knee pain. At MR imaging, synovial plicae appear as bands of low signal intensity within the high-signal-intensity joint fluid. Gradient-echo T2-weighted and fat-suppressed T2-weighted or proton density-weighted MR images are optimal for the evaluation of plicae. Plica syndrome, the painful impairment of knee function in which the only finding that helps explain the symptoms is the presence of a thickened and fibrotic plica, should be included in the differential diagnosis of internal derangement of the knee. A diffusely thickened synovial plica, perhaps associated with synovitis or erosion of the articular cartilage of the patella or femoral condyle, in a patient with no other significant MR imaging findings suggests the diagnosis of plica syndrome. Once the diagnosis has been made, nonsurgical treatment is preferable initially. Failure of the patient to improve with conservative treatment leaves arthroscopic excision of the pathologic plica as the treatment of choice.

In vivo observation of cavitation and embolism repair using magnetic resonance imaging.

Magnetic resonance imaging (MRI) was used to noninvasively monitor the status of individual xylem vessels in the stem of an intact, transpiring grape (Vitis vinifera) plant over a period of approximately 40 h. Proton density-weighted MRI was used to visualize the distribution of mobile water in the stem and individual xylem vessels were scored as either water or gas filled (i.e. embolized). The number of water-filled vessels decreased during the first 24 h of the experiment, indicating that approximately 10 vessels had cavitated during this time. Leaf water potentials decreased from -1.25 to -2.1 MPa during the same period. Watering increased leaf water potentials to -0.25 MPa and prevented any further cavitation. Refilling of xylem vessels occurred as soon as the lights were switched off, with the majority of vessels becoming refilled with water during the first 2 to 3 h in darkness. These measurements demonstrate that MRI can be used to monitor the functional status of individual xylem vessels, providing the first method to study the process of cavitation and embolism repair in intact plants.

Value of magnetization transfer contrast as a sensitive technique to reflect histopathological changes in the white matter adjacent to the frontal horns of lateral ventricles.

The purpose of this study is to evaluate the usefulness of magnetization transfer contrast (MTC) as a technique to reflect histopathological changes in the white matter adjacent to the frontal horns of the lateral ventricles. Radiological-pathological correlation was performed in six patients who underwent Magnetic Resonance (MR) examination prior to death and in whom postmortem examinations of the brain were obtained. The extent and the severity of degeneration in the white matter adjacent to the frontal horns were evaluated histopathologically, and compared with those observed on the conventional proton density (PD) weighted MR images (Group 1). Changes in the white matter of another 35 patients were classified into three types according to the pattern of high signals adjacent to the frontal horns on conventional PD weighted MR images, and magnetization transfer ratio (MTR) in the white matter adjacent to the frontal horns was calculated from multi-slice and single-slice FSE images (Group 2). The relationship between signal intensities and MTR in the white matter adjacent to the frontal horns was evaluated. The extent of degeneration in the white matter adjacent to the frontal horns was classified into mild, moderate and severe types on the basis of stainin for myelins, axons and astrocytes. In Group 1, histopathological findings indicated a difference in severity of degeneration in the white matter adjacent to the frontal horns among the three types, while no significant differences were noted in the signals on PD weighted MR images. In Group 2, MTR showed significant differences in the signal intensities in the white matter adjacent to the frontal horns (p < 0.01) between the three types, while conventional PD weighted MR images failed to differentiate between them. In conclusion, MT imaging is a sensitive technique to evaluate the histopathological changes in the white matter adjacent to the frontal horns that cannot be detected by conventional MR imaging.

Ｔ１強調ＭＲＩで円板後部組織に認められる低信号像の検討

The posterior disc attachment (PA) of the temporomandibular joint (TMJ) has relatively high signal intensity on T 1 -weighted or proton density-weighted magnetic resonance imaging (MRI). Sometimes, however, low signal intensity of the PA is observed in patients with chronic disc displacement. On the basis of previous histopathological studies, the areas of low signal intensity in the PA may be consistent with pseudodisc formation associated with fibrous metaplasia of the PA.The purpose of this study was to evaluate the relations between MR signal intensity of the PA and MRI findings, including the degree of disc displacement, disc reduction, disc shape, bone change, and condylar translation, as well as clinical findings, including the duration of symptoms, joint pain, and range of motion. The study was based on MRI of 216 TMJ in 184 patients with anterior disc displacement. The sagittal closed-mouth T 1 -weighted SE images were used to determine the presence or absence of low signal intensity in the PA.Low signal intensity in the PA was seen in 33 joints in 32 patients (15.3%). The incidence of low signal intensity was significantly higher in males (27.8%) than in females (12.8%).No statistical difference was found between anterior disc displacement with reduction (10.5%), anterior disc displacement without reduction (21.5%), and anterior disc displacement without reduction with osteoarthrosis (14.3%).Low signal intensity in the PA was seen only in moderate or severe disc displacement. Low signal intensity in the PA was not associated with specific clinical or MRI findings except for the degree of disc displacement.In conclusion, low signal intensity in the PA is directly correlated with disc displacement, and there was no apparent correlation with clinical findings. Low signal intensity of the PA is not necessarily related to adaptation of the joint in disc displacement.

Relaxornetry of Noncalcified Human Meningiomas

Resected meningiomas were examined by relaxometry and light microscopy to evaluate the potential of magnetic resonance imaging (MRI) for identifying histologic subtypes and for discriminating among benign, radiation therapy-induced, and malignant meningiomas. The magnetic field dependence of 1/T1 of water protons (nuclear magnetic relaxation dispersion [NMRD] profile) and the water content (dry weight) were measured for 67 specimens, and the data were compared with histology. Only noncalcified, nonhemorrhagic meningiomas are reported. No correlations were found between NMRD profiles, dry weight, and any histologic subtype, in contrast to an analogous study of astrocytomas. Rather, meningiomas have a broader variability of dry weight and 1/T1 than related parenchyma but a much narrower range than all grades of astrocytomas. The mean value of 1/T1, at all fields, is slightly higher in meningiomas--and the mean water content about the same--as adult cortical gray matter. Meningiomas are frequently isointense with cortex, and histologic subtypes cannot be differentiated at any magnetic field strength by MRI using only T1- or proton density-weighted MRI.

Magnetic Resonance Imaging of Orbital Lymphangioma with and without Gadolinium Contrast Enhancement

Lymphangioma is a vascular tumor of the orbit with a propensity for recurrent hemorrhage. These tumors may be difficult to diagnose in young patients who present with sudden proptosis due to hemorrhage into a previously unrecognized lesion. Magnetic resonance imaging (MRI) should be ideally suited for evaluating lymphangioma due to the unique ability of MRI to characterize hemorrhage because of the paramagnetic qualities of hemoglobin. The authors performed T1-, T2-, and proton density-weighted MRI on 12 patients with orbital lymphangioma. Six patients underwent MRI with gadolinium-DTPA contrast enhancement. The MRI studies were performed using a 1.5 Tesla super-conducting magnetic resonance unit, except for 3 early studies performed with a 0.5 Tesla unit. All studies were performed with orbital surface coil imaging. Computed tomography (CT) was performed in 10 patients. Tumor was visible on MRI in all 12 patients. Magnetic resonance imaging delineated clearly the internal structure of subacute and chronic hemorrhagic cysts, and differentiated between these tumors because of the different paramagnetic qualities of subacute hemorrhage compared to chronic hemorrhage. In two patients, MRI detected large tumor feeding vessels by the flow void phenomenon unique to MRI. Computed tomography did not detect these vessels. Gadolinium-contrasted T1-weighted MRI did not further delineate or characterize the tumor. Magnetic resonance imaging is the modality of choice for imaging orbital lymphangioma because of its unequalled differentiation of hemorrhagic cysts, and its unique ability to detect tumor feeding vessels by the flow void phenomenon.