Biomedical subjects
Publications and source records attributed to V M Rao.
Castleman disease in an 11-year-old girl appeared as a neck mass that grew despite antibiotic treatment. MR showed a well-defined solid mass, isointense with muscle on short-repetition-time/short-echo-time images, with a stellate area of central hypointensity on long-repetition-time/long-echo-time images, that did not enhance with gadolinium.
OBJECTIVE: Recent studies have shown that contrast (gadopentetate dimeglumine)-enhanced magnetic resonance imaging is useful in evaluating intraocular tumors and differentiating uveal melanoma from other simulating lesions. The purpose of this study was to study prospectively the role of fat-suppression technique and gadopentetate dimeglumine-enhanced magnetic resonance imaging in the evaluation of intraocular neoplasia. PATIENTS: Forty-three uveal melanomas and 20 other simulating intraocular lesions from 63 patients were prospectively evaluated on non-contrast-enhanced and post-contrast-enhanced T1-weighted images with and without fat-suppression technique and on T2-weighted images. RESULTS: Forty-one uveal melanomas (95%) were detected with standard pulse sequences and showed the characteristic hyperintense signal on non-contrast-enhanced T1-weighted images and hypointense signal with respect to the vitreous on T2-weighted images. All 33 uveal melanomas evaluated on non-contrast-enhanced T1-weighted images with fat-suppression technique were detected on non-contrast-enhanced images with fat-suppression technique. The intensity of the signal was statistically associated with the degree of pigmentation of the tumor on T1-weighted images with fat-suppression technique (P = .03). On post-contrast-enhanced T1-weighted images with or without fat-suppression technique, the 43 uveal melanomas showed enhancement. The degree of tumor enhancement was not statistically related to the degree of tumor pigmentation or the location of the tumor. Among the other simulating intraocular lesions, choroidal metastasis, retinoblastoma, choroidal leiomyoma, and medulloepithelioma demonstrated the same features on magnetic resonance imaging studies as uveal melanoma demonstrated on non-contrast-enhanced and post-contrast-enhanced T1-weighted images with or without fat-suppression technique. In our series, choroidal hemangioma, choroidal osteoma, posterior scleritis, retinal hemangioma, and Coats' disease can be differentiated from other amelanotic intraocular tumors by their characteristics on magnetic resonance imaging studies. CONCLUSIONS: We concluded that pre-and post-contrast-enhanced T1-weighted images with fat-suppression technique are most helpful in detecting small intraocular tumors with a thickness of more than 1.8 mm and in evaluating intraocular neoplasms and simulating lesions, particularly when T2-weighted images are not available. Moreover, in juxtapapillary choroidal or retinal tumor, fat-suppression technique may help in the detection of possible optic nerve or orbital extension by improving the conspicuousness of the tumor.
Explore the source record for details and available documents.
PURPOSE: Magnetization transfer (MT) imaging enables analysis of the contribution of restricted motion protons in the macromolecular pool to magnetic resonance (MR) signal intensity. The authors undertook this study to determine whether MT ratios (MTRs) could be used to predict pathologic characteristics of head and neck neoplasms. MATERIALS AND METHODS: Fifty-four patients with pathologically proved neoplasms (squamous cell carcinomas, n = 33; non-squamous cell carcinomas, n = 11; benign masses, n = 10) underwent MT imaging. MTRs were correlated with pathologic findings. RESULTS: No statistically significant correlations were noted between MTRs and degree of differentiation, keratinization, cells per high-power field, and rate of mitosis. Statistically significant differences were found between MTRs of malignancies and muscle (P < .01), cerebrospinal fluid (P < .001), fat (P < .001), and benign neoplasms (P < .001). MTRs of muscle were higher than those of benign, squamous cell, and non-squamous cell neoplasms. CONCLUSION: MT imaging shows promise in differentiation of benign from malignant head and neck neoplasms. No statistically significant differences in MTRs were noted among malignancies.
MR appearance of two patients with large, orbital conjunctival epithelium-lined inclusion cysts are presented. Both were complications of ophthalmic surgical procedures that necessitated conjunctival incision.
High resolution thin section (1.5 mm thick) spin echo images (HRSE) with narrow bandwidth of TMJ were compared to the conventional (3 mm thick) spin echo images (CSE) in 20 symptomatic patients. Our results revealed that the disk delineation was superior with HRSE and the degree of confidence in making the diagnosis was significantly higher with HRSE than with CSE. Narrow bandwidth, high resolution spin echo technique offers better anatomic detail in the TMJ, resulting in improved degree of confidence, without penalty in additional imaging time.
PURPOSE: To determine the incidence of a "stuck" disk and its importance in the overall scheme of internal derangement. MATERIALS AND METHODS: Magnetic resonance (MR) images of 212 temporomandibular joints (TMJs) in 106 symptomatic patients were obtained and reviewed. Image analysis included assessment of disk position; disk mobility; and degree of condylar translation, with or without disk recapture in joints with displaced disks. RESULTS: Of the 127 joints with disks in a normal position, 94 had mobile disks and 23 had stuck disks. Ten joints revealed no condylar translation, which precluded assessment of disk mobility. Of 85 joints with displaced disks, 67 joints showed mobility, with recapture in 25 and no recapture in 42. Significant correlation existed between disk mobility and degree of condylar translation (P < .001). CONCLUSION: The TMJ disk may be stuck in a normal or displaced position and limits the normal degree of condylar translation, leading to restricted jaw opening. Recognition of a stuck TMJ disk could alter patient care.
Few detailed radiologic articles treat the medial canthus as a "compartment" of the orbit. Nasal stuffiness and epiphora (excessive tearing) are frequent clinical manifestations of diseases involving the medial canthus of the orbit. Although some lesions can be adequately evaluated by clinical examination, imaging may show unsuspected deep extensions of the abnormality. CT has traditionally been the imaging method of choice because of the inherent contrast between structures in this region and its superb depiction of bone detail (Fig. 1). MR imaging can be useful in detecting subtle marrow invasion caused by lesions extending beyond the confines of the medial canthus (e.g., frontal bone, maxilla). In this pictorial essay, we illustrate the CT and MR appearances of diseases that can manifest as a medial canthal mass and provide practical differential diagnoses. Lesions can be inflammatory, neoplastic, or developmental in origin. Moreover, these lesions can result from abnormalities in the adjacent nasolacrimal apparatus, orbit, paranasal sinuses, and nasal cavity, or they can reflect an underlying systemic illness.
MR is a highly sensitive alternative to plain films, CT, and radionuclide studies for the imaging of normal and abnormal marrow and can characterize differences between fatty, fibrotic, cellular, hypercellular, and hemosiderotic marrow. MR is helpful in depicting the extent of disease and has been a useful method to follow the clinical course of many disorders. It has been found to be particularly useful in explaining the unrepresentative biopsy, as the distribution of many diseases is frequently heterogeneous as exemplified by the mixed fatty and cellular patterns of aplastic anemia, myeloma, lymphoma, and skeletal metastases. Patterns of cellular and fatty marrow in the epiphysis and apophysis after marrow reconversion were not completely understood prior to the introduction of MR scanning. Because it has the advantage of imaging the entire bone marrow compartment (unlike the situation with biopsy on aspiration), MR allows a better understanding of the distribution of skeletal disease.
A 51 year old man with biopsy proven pulmonary sarcoidosis and skin test positive for tuberculosis presented with features of an amelanotic flat choroidal mass suggestive of choroiditis. The mass enlarged despite corticosteroids and anti-tuberculous medications. A thorough systemic evaluation for possible primary tumor metastatic to the choroid was negative. Further clinical evaluation and magnetic resonance imaging suggested a diffuse primary choroidal malignant melanoma with optic nerve invasion. The eye was enucleated and the mass proved histopathologically to be a mucin secreting adenocarcinoma of unknown origin despite a repeat systemic work-up. The patient died three months after the onset of symptoms and three weeks after enucleation with diffuse metastases from an unknown primary cancer. Magnetic resonance imaging (MRI) is usually helpful in the differentiation of uveal melanoma from uveal metastasis. In this case, however, it suggested the diagnosis of a diffuse choroidal melanoma. The reason for the atypical MRI findings will be discussed.
The role of magnetic resonance imaging (MRI) in the assessment of fibrovascular ingrowth in the integrated hydroxyapatite orbital implant is evaluated. Fifteen patients who underwent enucleation and placement of a hydroxyapatite orbital implant were evaluated for degree of implant vascularity with gadolinium-DPTA-enhanced MRI with surface coil before drilling the implant. On T1-weighted images, the hydroxyapatite sphere appeared with intermediate signal. After gadolinium-DPTA administration, all patients showed an enhancement in the implant consistent with the presence of fibrovascular ingrowth. The enhancement was most notable in the peripheral portions of the sphere and was seen as early as 5 months after implantation. Comparison of gadolinium-DPTA-enhanced MRI with contrast-enhanced computed tomography, ultrasonography, and color Doppler imaging suggests that these latter techniques are not as helpful in the detection of the fibrovascular tissue in the orbital implant. Bone scan, a technique used by many surgeons, demonstrates fibrovascular ingrowth, but it is limited by its one-dimensional low-resolution image. Because of its three-dimensional capability and its highest resolution, contrast-enhanced MRI with surface coil appears to be the best imaging method for evaluating the hydroxyapatite orbital implant and its fibrovascular ingrowth.
Magnetic resonance (MR) imaging was performed in 14 patients with biopsy-proved polycythemia vera (n = 4) or myelofibrosis (n = 10) to determine whether MR imaging findings can be correlated with the clinicopathologic diagnosis and established clinical parameters of severity (serum lactate dehydrogenase [LDH] and cholesterol levels) and chronicity (spleen size). Evaluation of marrow in the proximal femurs showed that patients could be categorized into three distinct groups based on anatomic patterns of normal fatty and abnormal low-signal-intensity (non-fatty) marrow in the femoral capital epiphysis (FCE) and greater trochanter (GT). Patients with nonfatty marrow in both the FCE and GT (n = 8) had significantly higher serum LDH (P less than .02) and lower serum cholesterol (P less than .02) levels than patients with fatty marrow in at least the GT (n = 6). Splenic volume, as measured from MR images, was significantly greater in the myelofibrosis group than in the polycythemia vera group (P less than .001). MR imaging provided a better understanding of these hematologic disorders and novel parameters for classification that are different from conventional histologic and laboratory data.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A 35-year-old woman developed painful proptosis of the left eye over a period of 3 weeks. Orbital computed tomography and magnetic resonance imaging revealed a well-circumscribed superior orbital tumor with variable density. The mass was removed entirely by way of a superior orbitotomy. Histopathologically, it was found to be a neurofibroma. The patient had no clinical findings of neurofibromatosis. The presence of extensive myxomatous degeneration and the dense collection of collagen bundles in the tumor are correlated with the unusual computed tomography and magnetic resonance imaging features.
Magnetic resonance imaging of the temporomandibular joint is a topic of recent interest and has gained widespread use for the assessment of internal derangement and other temporomandibular joint-related symptoms. In this article the authors present six proven cases of pathologic abnormalities of the temporomandibular joint region that may clinically mimic internal derangement. These cases demonstrate the importance of the monitoring of studies by a radiologist and also the utility of computed tomography as an adjunctive modality. Magnetic resonance imaging and computed tomography are often complimentary in diagnosing etiologies that may mimic internal derangement. Because abnormalities other than internal derangement are often encountered during the use of magnetic resonance imaging, it is essential for the radiologist to assume an active role in monitoring such cases.
High resolution magnetic resonance imaging (MRI) with surface coil and contrast material was used to demonstrate the presence of bone in choroidal osteoma. Contrary to initial impressions, choroidal osteoma does not show typical negative image of the bone in MRI scans. The ossifying tumor of the choroid appears as a bright (hyperintense) signal on T1-weighted images and as an area of relative low intensity on T2-weighted images. On contrast T1-weighted scans, the tumor showed gadolinium-DPTA (Gd-DPTA) enhancement. These MRI findings are discussed in relation with histopathologic features of choroidal osteoma and the presence of fat marrow in the intertrabecular spaces of the bone at the level of the choroid.
In imaging small anatomical parts such as the pituitary fossa, thin sections enhance the spatial resolution. Gradient recalled images (GRASS) using three-dimensional volume data produce ultrathin contiguous sections with a high signal-to-noise ratio. In this study, conventional spin-echo magnetic resonance images (MRIs) of the pituitary fossa were compared to three-dimensional gradient recalled MRI in 5 volunteers and 10 patients suspected of having pituitary gland abnormalities. Utility of fat suppression was also assessed, along with gadolinium enhancement. Conventional spin-echo and three-dimensional spoiled GRASS images, three-dimensional spoiled GRASS images without and with fat suppression (Group II), and three-dimensional spoiled GRASS images with fat suppression before and after gadolinium enhancement were compared. Three-dimensional spoiled GRASS images provided better delineation of the pituitary fossa structures. There was differential enhancement between the normal gland and pituitary tumors. The fat suppression technique following gadolinium administration helped separate the high signal of tumor from the high signal of the clivus marrow. In conclusion, T1-weighted three dimensional gradient-echo images with fat suppression following gadolinium enhancement appear promising in evaluation.