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M D Schnall

Publications and source records attributed to M D Schnall.

116 records · Page 7Linked to original sources
PubMedDate not supplied

Multicoil MR imaging of symptomatic female urethral and periurethral disease.

High-resolution magnetic resonance (MR) imaging with phased-array pelvic and endorectal coils has dramatically enhanced the ability to visualize abnormalities of the female urethra and periurethral tissues. These include developmental abnormalities (eg, urethral duplication, ectopic ureterocele), benign processes (eg, urethral diverticulum, caruncle, leiomyoma, trauma, and fistula; stress incontinence; paravaginal cyst), and malignant processes (eg, primary urethral carcinoma, secondary urethral malignancies). High-resolution MR imaging can be used to assess complications such as fistula formation and periurethral abscess, localize various entities, exclude pathologic processes whose presence could lead to an incorrect diagnosis, differentiate processes that might be confused at physical examination, and contribute to surgical planning and facilitate surgical correction.

Adolescent↗
PubMedDate not supplied

Gadolinium-enhanced ultrafast three-dimensional spoiled gradient-echo MR imaging of the abdominal aorta and visceral and iliac vessels.

Gadolinium-enhanced ultrafast three-dimensional (3D) spoiled gradient-echo magnetic resonance (MR) imaging is a noninvasive method for evaluating the abdominal aorta and the visceral and iliac vessels. With an enhanced gradient system, 20-48 sections can be obtained during a single 18-32-second patient breath hold. The 3D volume obtained from a single acquisition can be reformatted at a workstation and the vascular anatomy viewed in any projection and with a variety of section thicknesses, making this MR imaging technique particularly useful in the evaluation of aberrant arteries, vascular stenoses, aneurysms, and dissection flaps. Gadolinium-enhanced ultrafast 3D spoiled gradient-echo MR imaging has been used instead of or in addition to conventional contrast material-enhanced MR angiography in patients who have chronic symptoms of mesenteric ischemia, who have abdominal aortic aneurysms, or who are at risk for iodinated contrast material-related renal dysfunction. This technique shows great promise for accurate and noninvasive evaluation of the abdominal aorta and the visceral and iliac vessels.

Adult↗
PubMedDate not supplied

High-resolution MR imaging of the vagina.

High-resolution magnetic resonance (MR) imaging with pelvic phased-array and endoluminal coils provides information on vaginal abnormalities heretofore not available with other imaging modalities. Congenital anomalies of the vagina can result from disorders of lateral fusion of the descending müllerian ducts and ascending urogenital sinus, developmental absence of the müllerian ducts, or disorders of vertical fusion. In these conditions, MR imaging can depict the presence or absence of the vagina, cervix, and uterus and help determine whether these structures contain a septum or are duplicated or distended with blood. Gartner duct cysts and Bartholin gland cysts have the same signal intensity characteristics, but the former are located in the anterolateral aspect of the proximal third of the vagina and the latter are in the posterolateral portion of the lower vagina. Entero-, vesico-, and ureterovaginal fistulas result from obstetric and surgical trauma, radiation therapy, or inflammatory bowel disease. MR imaging has great potential for detection and characterization of these fistulas. MR imaging can be used to detect and stage primary and secondary vaginal tumors. However, neither signal intensity nor patterns of enhancement enable confident prediction of the histologic subtype of vaginal malignancy.

Adult↗
PubMedDate not supplied

Correlation of lesion appearance and histologic findings for the nodes of a breast MR imaging interpretation model.

An interpretation model for evaluating magnetic resonance (MR) images of the breast was constructed that allowed differentiation of benign from malignant palpable or mammographically visible abnormalities. Architectural features define each node of the model. Investigation was subsequently made of the histologic findings in individuals within each node and of the frequency with which each histologic finding manifested as a particular architectural feature to determine whether nodal location and specific histologic findings are mutually predictive. The strongest associations were found between fibrocystic change and smooth masses, fibroadenoma and lobulated masses with nonenhancing internal septations, invasive ductal carcinoma (with or without ductal carcinoma in situ [DCIS]) and enhancing irregular or spiculated masses, invasive tubular carcinoma or radial scar and spiculated masses, medullary or colloid carcinoma and enhancing lobulated masses, invasive lobular carcinoma and the absence of a focal mass, DCIS and ductal enhancement, and DCIS (with or without invasive ductal carcinoma) and regional enhancement. Nodal location and histologic findings proved to be mutually predictive within the model; that is, the nodal location of MR imaging features within the model can be used to predict histologic findings and vice versa.

Biopsy↗
PubMedDate not supplied

An in vitro study of magnetization transfer and relaxation rates of hematoma.

PURPOSE: To assess, in an in vitro model of acute hematoma, whether hemoglobin immobilization by clot and red cell membrane aging can account for the T2 shortening usually attributed to deoxyhemoglobin. METHODS: Clotted and heparinized blood samples were packed (100% hematocrit). The apparent magnetization transfer rate (AMTR), T1 and T2 relaxation rates of the samples, and images with a volunteer's head were obtained at 1.5 T. RESULTS: The AMTR and T1 and T2 relaxation rates were unaffected by the presence of clot. The AMTR was unaffected by red cell aging. The diamagnetic packed blood samples, which are much denser than brain, were isointense to gray matter on T2-weighted images and had about one-fifth the AMTR of white matter. CONCLUSIONS: Hemoglobin immobilization by clot structure or red cell contraction with aging is insignificant and does not contribute to the T2 shortening of acute hematoma. The low AMTR and T2 relaxation rates of diamagnetic blood appear to be caused by the mobility of hemoglobin and by the red cell's lack of immobile macromolecular structures such as those associated with nucleated brain cells.

Acute Disease↗
PubMedDate not supplied

Magnetization transfer effects in MR imaging of in vivo intracranial hemorrhage.

PURPOSE: Recent papers have hypothesized that diamagnetic effects of clotting and conformational changes in aging red blood cells immobilize the hemoglobin protein and thus are responsible for the marked hypointensity of acute hematomas on T2-weighted spin-echo MR images. To test that hypothesis, the authors evaluated 24 hemorrhagic components of intracranial hemorrhagic lesions using accepted criteria based on spin-echo images as the definitions of the stage of the hemorrhage. METHODS: As a measure of the effects of macromolecular (hemoglobin protein) immobility, magnetization transfer contrast was elicited using a pulsed saturation magnetization transfer experiment. The apparent magnetization transfer contrast (AMTC) was determined by comparing the signal intensities of saturated with unsaturated images and quantified for acute isolated hemorrhages, acute nonisolated hemorrhagic lesions, and subacute-to-chronic hemorrhages. RESULTS: The AMTC of isolated acute hemorrhage was significantly less than that of normal, white matter and gray matter, indicating the lack of significant magnetization transfer and therefore the lack of effects of restriction of hemoglobin mobility on the signal intensity of acute hemorrhage. Acutely hemorrhagic tissue (nonisolated acute hemorrhage) has significantly more AMTC than isolated acute hemorrhage, but still not exceeding that of brain parenchyma. CONCLUSION: This in vivo data concurs with in vitro data and reinforces the concept that the marked hypointensity of acute hematomas is mainly a magnetic susceptibility effect.

Adult↗
PubMedDate not supplied

The low sensitivity of fluid-attenuated inversion-recovery MR in the detection of multiple sclerosis of the spinal cord.

PURPOSE: To confirm the expected superiority of fluid-attenuated inversion-recovery (FLAIR) over conventional fast spin-echo MR imaging in the detection of multiple sclerosis (MS) of the spinal cord. METHODS: Fifteen subjects with known MS involving the spinal cord and brain were studied prospectively. The entire cord was imaged with a phased-array coil on a 1.5-T MR system. Sagittal T1-weighted and fast spin-echo proton density- and T2-weighted images were followed by fast FLAIR images. FLAIR parameters were varied to optimize lesion conspicuity with optimal inversion times (TIs) ranging from 2400 to 2600. Lesion conspicuity and detection were compared between the fast spin-echo and FLAIR images by three radiologists who reached agreement by consensus. RESULTS: The FLAIR technique effectively suppressed cerebrospinal fluid (CSF) signal and reduced CSF pulsation and truncation artifacts in all cases. Shorter imaging parameters (repetition time of 4000 to 6000, TI of 1500 to 2000) uniformly decreased lesion conspicuity in all subjects. Of 11 cord lesions in five subjects imaged with the longer parameters (repetition time of 8000 to 11,000, TI of 2400 to 2600), three were not seen on FLAIR images, four were less conspicuous on FLAIR images, and four were seen equally or better on FLAIR images. CONCLUSION: Although successful in suppressing CSF signal and reducing imaging artifacts, fast FLAIR imaging appears unreliable in the detection of MS lesions in the spinal cord.

Adult↗