Search PubMed⌕ Search

Biomedical subjects

N M Hylton

Publications and source records attributed to N M Hylton.

15 recordsLinked to original sources
PubMed2026

Surgical Management of Young Women with High-Risk Breast Cancer Receiving Neoadjuvant Systemic Therapy on the I-SPY2 Trial.

BACKGROUND: Mastectomy rates in women with breast cancer are higher in younger women than in older women. The impact of this more extensive surgery on overall survival (OS) and locoregional recurrence in younger women is unknown, especially after neoadjuvant systemic therapy (NST). This study evaluated surgical management and outcomes of patients aged &#x2264; 45 versus > 45 years enrolled in multicenter NST clinical trial, I-SPY2.0 (NCT01042379, PMID 37325931). METHODS: We conducted a secondary data analysis comparing locoregional treatment in patients aged &#x2264; 45 versus > 45 years with clinical or molecular high-risk clinical stage II-III breast cancer treated from April 2010 to June 2022. Multivariate Cox proportional hazards models were used to evaluate associations between type of breast surgery with OS and locoregional recurrence-free interval by age group and tumor receptor subtype. RESULTS: Of 1737 patients, 698 (40.2%) were aged &#x2264; 45 years. There were no significant differences in patient or tumor characteristics or residual cancer burden distribution between age groups. Although breast-conserving surgery was significantly less common in younger women (36.8% vs 48.5%, p < 0.001), surgery type was not associated with OS or locoregional recurrence-free interval for patients aged &#x2264; 45 years. CONCLUSIONS: Greater extent of breast surgery was not associated with improved outcomes in women aged &#x2264; 45 years. Choice of surgical procedure in the management of breast cancer is multifactorial, but young age alone&#xa0;does not warrant mastectomy following NST.

Breast cancer↗
PubMed1994

Imaging techniques for breast MR imaging.

Specialized rf coils and pulse sequence techniques for contrast-enhanced breast imaging have been a focus of recent attention in MR imaging research. The imaging strategies for maximizing sensitivity and specificity involve trade-offs between spatial and temporal resolution. This article discusses these issues and others, such as considerations for coil design, fat suppression, patient positioning, motion artifact reduction, and methods for quantitative measurement of dynamic contrast enhancement.

Adipose Tissue↗
PubMed1992

Impact of section doubling on MR angiography.

To improve the quality of projection angiograms generated from three-dimensional magnetic resonance (MR) angiography data, the authors applied voxel shifting to create intermediate sections ("section doubling") prior to maximum intensity projection. To date, the authors have processed MR angiography studies with and without section doubling in 20 cases. Section doubling resulted in improved vessel contrast and delineation of continuity (especially of small vessels) in all cases.

Blood Vessels↗
PubMed1990

Oblique reformatting of multislice magnetic resonance images for improved visualization of coronary arteries.

A technique for reformatting multislice magnetic resonance images into arbitrary oblique planes has been developed and implemented on a Toshiba MRT-35 (formerly Diasonics MT/S) imaging system (South San Francisco, CA). This method is designed to allow the user to easily define a new plane by marking with a cursor features of interest on two or three different image levels. These features are combined in the resulting oblique image. The reformatted image can have arbitrary angulation and is created with a pixel dimension equivalent to the original data set. Resolution ranges from the original in-plane resolution to the slice thickness, depending on angulation. An improvement in signal-to-noise ratio results from the effective averaging performed by interpolation. This method is optimally used to correct for small variations in alignment, such as the positioning of the intervertebral disks. It can also be used to generate reformatted images at many different angles from a single multislice data set. This method has been applied to the particular problem of improving the presentation of coronary arteries on a conventional set of multislice spin-echo cardiac images by increasing the visible length of individual coronary segments.

Coronary Vessels↗
PubMed1988

Echo-planar pediatric imager.

Practical constraints make it difficult to build large-aperture echo-planar magnetic resonance (MR) imagers. The implementation of a pediatric imager and its performance are described. Spatial resolution and signal-to-noise levels comparable to those of 1982 state-of-the-art MR imagers have been achieved in imaging times of 0.05-0.15 seconds. T1 and T2 information are obtainable in the echo-planar mode. A major issue is that of chemical-shift displacements.

Child↗
PubMed1987

The value of relaxation times and density measurements in clinical MRI.

The hope that MRI relaxation time signatures would identify tissues, specifically, malignancies, has not been realized. This is due much less to measurement inaccuracies than to a large intrinsic variability and overlaps between malignancies and many benign pathologies. Neither has there been success in predicting relaxation times from basic tissue compositions. Nevertheless, MRI provides a qualitative measure of tissue hydration, and of flow, on the basis of relaxation times. Furthermore, pixel-by-pixel maps of relaxation times have proven useful in understanding the MRI process, in predicting the efficacy of untried techniques, and replace, in many circumstances, the need for acquisition of images with diverse sequencing parameters.

Body Water↗
PubMed1987

Partial flip angle MR imaging.

Theoretical analysis predicts that performing magnetic resonance (MR) imaging with partial (less than 90 degrees) flip angles can reduce imaging times two- to fourfold when lesions with elevated T1 values are being examined. This time savings occurs because repetition time (TR) is reduced when imaging is performed with partial flips. Partial flip MR imaging can also improve signal-to-noise ratio (S/N) in fast body imaging. For this study, analytical tools were used to predict image contrast and S/N for short TR, partial flip sequences. Experimental implementation of the short TR, partial flip sequences that analytical work had predicted would be optimal supported the analytical predictions and demonstrated their validity. Partial flip MR imaging is applicable to reducing imaging time only when the ratio of signal differences to noise exceeds threshold values in conventional MR images. Partial flip sequences can be used to advantage in MR imaging of both the head and the body, and the observed effects are predictable through theoretical analysis.

Brain↗
PubMed1986

Information processing in magnetic resonance imaging.

Techniques of image processing have been developed for the extraction of information from magnetic resonance images. The response of nuclei to a sequence of magnetic stimulations has been modeled and used to predict the effects of changing magnetic resonance parameters on signal intensity. This allows the calculation of new images from a small set of acquired data without additional acquisition. These images can be used to predict the results of new imaging techniques before actual implementation and to simulate the effects of parameter variations which are unfeasible or impractical, such as variable field strength. New forms of representation, for example, a tissue type map in which each homogeneous tissue category has been identified and labeled, can be used for more direct interpretation.

Algorithms↗
PubMed1985

Multiple spin-echo magnetic resonance imaging.

Spin-echo magnetic resonance (MR) imaging detects a variety of pathologic states with great sensitivity. A technique for producing multiple spin-echo images in multisection operation is presented. This method of intensity-image acquisition is compared with retrospective intensity-image synthesis from routine data sets. Both yield long echo time (TE) images with similar image contrast and comparable and often increased diagnostic utility. Technical and clinical considerations are addressed, including signal-to-noise levels, flow effects, and patient throughput.

Brain Diseases↗
PubMed1985

Variable magnetic resonance imaging parameters: effect on detection and characterization of lesions.

With change in the imaging technique and magnetic field strength used in magnetic resonance imaging, wide variations in the delineation of pathologic features occur. Using imaging data from patients with known pathologic conditions, we evaluated the intensity images in spin-echo and inversion-recovery imaging at varying repetition times, echo times, and inversion times over broad ranges and changing magnetic field strengths. Differences in conspicuity and the apparent size of the lesions are important to consider in diagnosing and evaluating pathologic conditions, especially when different imagers and techniques are employed.

Brain Diseases↗
PubMed1984

Signal to noise in derived NMR images.

The NMR image is dependent on multiple tissue parameters: hydrogen density, relaxation times T1 and T2, and flow. From the acquired intensity images, T1, T2, and hydrogen images may be produced. The signal/noise of these derived images is critically dependent on the choice of acquisition parameters. Using the calculated T1, T2, and hydrogen images, intensity images may be calculated at arbitrary values of TE and TR, some of which (for example, short TE or TR) may be physically unacquirable.

Brain↗
PubMedDate not supplied

NMR in experimental cerebral edema: value of T1 and T2 calculations.

In an experimental investigation, the efficacy of nuclear magnetic resonance (NMR) relaxation times in measuring brain water was studied. Cerebral edema was induced in four dogs with a freeze lesion, which was produced by contact with a steel cylinder cooled in liquid nitrogen and placed on the exposed dural surface of the brain. NMR proton imaging was performed 2, 3, 6, or 24 hr after production of the lesion, at a field strength of 0.35 T, using multiparametric spin-echo (SE) technique. The animals were sacrificed immediately after imaging, and brain samples were analyzed for water content (wet-to-dry, microgravimetry). Correlation between water content, NMR imaging, and resulting T1, T2 relaxation times and mobile proton density values calculated with SE technique was performed. Brain sample analysis showed elevation of water content in the white matter subjacent to the lesion in all four dogs, rising at least 15% in each of the animals. NMR imaging detected the freeze lesion and subjacent vasogenic edema of the white matter in all animals. The 2 sec pulse interval SE technique was most sensitive in the detection of the abnormality, and provided optimal differentiation of gray and white matter. The second echo sampling (56 msec) was most sensitive to the detection of edema. The T1 and T2 relaxation values, as well as the mobile proton density values, were elevated in the normal gray matter and in the abnormal white matter when compared with normal white matter in any given animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗