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Biomedical subjects

R B Lufkin

Publications and source records attributed to R B Lufkin.

At least 19 recordsLinked to original sources
PubMed2001

Magnetic resonance imaging--guided fine-needle aspiration biopsies of retropharyngeal lesions.

OBJECTIVE: The retropharyngeal space is a deep neck space susceptible to a host of disease processes. Surgical access to this space is technically difficult and associated with potential morbidity. An image-guided fine-needle aspiration (FNA) biopsy, if proven accurate and safe, would be of great benefit as an alternative diagnostic approach to this space. This study reports on the use of magnetic resonance imaging (MRI)--guided FNA for diagnostic evaluation of retropharyngeal lesions. Technical details of needle systems, approach to this space, and reliability of this method are described. STUDY DESIGN: This is a prospective study of 14 patients with retropharyngeal lesions who underwent MRI-guided FNA biopsy at the University of California at Los Angeles Center for the Health Sciences between October 1989 and October 1998. METHODS: A 0.2-tesla open magnet was used to obtain magnetic resonance images of each retropharyngeal lesion. After standard skin preparation a coaxial needle system was used to reach and sample the lesion. In most instances, the specimen was immediately stained and examined by a cytopathologist for adequacy before removing the patient from the scanner. RESULTS: Eleven of 14 (78%) patients had diagnostic aspirations; only 2 of these 11 patients required additional surgical biopsy for more specific histological characterization of their lesions before definitive treatment recommendations were given. All aspiration procedures were well tolerated and without any complications. CONCLUSION: We have demonstrated that MRI-guided approach to the retropharynx is feasible, safe, and sensitive enough to obviate the need for open biopsies in a large percentage of patients.

Adult↗
PubMed2000

MRI-guided needle localization in the head and neck using contemporaneous imaging in an open configuration system.

BACKGROUND: MRI-guided procedures have previously been limited by technical difficulties, including the need for MRI-compatible instruments, slow image acquisition time, and the closed nature of conventional MRI scanners. The development of open configuration MRI systems with in-room, contemporaneous imaging has greatly increased the potential for MRI-guided interventional procedures. We evaluate our clinical experience applying this technology to the head and neck. METHODS: An open design 0.2T magnet combined with an in-room monitor was used for 24 MRI-guided needle localization procedures in the head and neck. Success of the procedures was based on the ability to accurately position the instrument in the target region to allow biopsy or treatment. RESULTS: In all 24 cases placement of the instrument within the target tissue was successful. CONCLUSION: MRI-guided needle-localization procedures in an open design magnet with in-room, contemporaneous image monitoring offer advantages over previous conventional interventional MRI systems by allowing interactive guidance with near real-time imaging feedback. As a result, procedure time is reduced and accuracy of instrument positioning is increased.

Adolescent↗
PubMed1999

MRI of thermally denatured blood: methemoglobin formation and relaxation effects.

Focal regions of T1-shortening have been observed in magnetic resonance imaging (MRI)-monitored thermal ablations of perfused tissues. The aims of this study were two-fold: to find evidence for heat-induced conversion of hemoglobin (Hb) to methemoglobin (mHb), and to investigate the effects of heat treatment of in-vitro blood components upon their MR relaxation times. Spectrophotometric studies were performed to confirm the heat-induced formation of methemoglobin. Preparations of whole and fractionated blood, previously submitted to elevated temperatures of 40 degrees C to 80 degrees C, were imaged and the relaxation times were calculated. Optical absorption spectra of samples containing free Hb, heated to 60 degrees C, showed increased light absorption at 630 nm, evident of mHb presence. Short T1 values in whole blood (1.13 s) and packed red blood cell (0.65 s) compartments, heated at 60 degrees C, compared to their baseline values (1.62 s and 0.83 s, respectively), were attributed to mHb formation. In relation to MRI-guided thermal interventions, these results suggest a possible explanation for observation of hyperintense regions on T1-weighted images.

Animals↗
PubMed1997

A multimedia database system for thermal ablation therapy of brain tumors.

A prototype multimedia medical database is described for supporting thermal ablation therapy of brain tumors. Its design is motivated by the major need to manage and access multimedia information on the progress and reaction of tumors to various therapy protocols. The database links images to patient data in a way that permits the use to view and query medical information using alphanumeric, temporal, and feature-based predicates. Visualization programs permit the user to view or annotate the query results in various ways. These results support the wide variety of data types and presentation methods required by neuroradiologists to manage thermal ablation therapy data. The database satisfactorily meets the requirements defined by thermal ablation therapy. A similar approach is being undertaken for supporting different therapies of other types of tumors, thus showing the generality of our approach.

Brain Neoplasms↗
PubMed1997

Interventional MRI: update.

Interventional MRI is in its early stages of development. Nevertheless, the design of new interventional MRI scanners that allow maximum direct access to the patient combined with the development of new interventional MRI pulse sequences and localization systems, means that the archetypal operating rooms of the 21st century may well contain dedicated interventional MRI units for combined radiological and surgical procedures. The present article looks at the state of interventional MRI today and looks ahead to what may be forthcoming in the not-too-distant future. After briefly discussing the instrumentation necessary for practical interventional MRI, the article will go on to describe a number of different approaches to, and clinical applications for, interventional MRI. The use of MRI in guiding and controlling tumor ablation, aspiration cytology and surgical biopsy of different body parts is described.

Animals↗
PubMed1997

Frequency-selective fat suppression MR imaging. Localized asymmetric failure of fat suppression mimicking orbital disease.

Our objectives were to further characterize an artifact related to the localized failure of the frequency-selective (FATSAT) fat suppression magnetic resonance (MR) imaging technique. We constructed two phantoms simulating human orbital anatomy and imaged them on a 1.5-T MR scanner using (FATSAT) and short T1 inversion recovery (STIR) techniques of fat suppression. The first phantom resembled orbit structural configurations; it was imaged in coronal and axial planes and in varying orientations with respect to the main magnetic field (Z axis) to study the features of the artifact and to reproduce the asymmetry seen in clinical cases. We designed the second phantom to enable quantification of the change in artifact size with change in orientation. We imaged the orbits of a normal human volunteer in similar planes and orientations, and compared the results to clinical cases demonstrating the artifact and true orbital disease. The artifact identified with localized failure of FATSAT fat suppression manifested as regions of hyperintensity maximal at fat-air interfaces, with gradual fading of the increased signal with distance from the interfaces. The artifact was most prominent when the interfaces were perpendicular to the axis of the main magnetic field (Z axis). The regions of increased brightness obscured normal orbital structures but were not associated with alterations in the geometry of these structures. Changes in orientation of the interfaces with respect to the Z axis, both in the phantoms and normal volunteer, reproduced the asymmetry of fat suppression failure seen in clinical cases. The relationship of size of the artifact to change in orientation was non-linear. The artifact was not seen on STIR images. We concluded that failure of FATSAT fat suppression may mimic orbital disease, particularly if asymmetric. As predicted by the Maxwell electromagnetism equation, slight variations in orientation of the fat-air interface to the Z axis may produce large asymmetries in fat suppression failure in the orbit. Confirmation may require either comparison with additional pulse sequences [T1-weighted spin echo (T1W SE) or STIR] or repositioning the patient's head to check for persistence of the finding with varying orientations.

Adipose Tissue↗
PubMed1997

Brain structure and function and the outcomes of treatment for depression.

BACKGROUND: Depressed patients have a variety of brain structural alterations, the most common being atrophy and deep white-matter lesions. Alterations in brain function also are common, particularly regional decreases in cerebral metabolism and perfusion. METHOD: We review here the evidence that alterations in brain structure and function may explain some of the heterogeneity in outcomes of depression. We also report initial results suggesting that measurement of brain structure and function may help to predict outcomes of treatment for depression. Brain structure was examined using three-dimensional reconstruction and volumetric analysis of magnetic resonance imaging (MRI) scans. Brain function was examined using quantitative electroencephalography (QEEG), performed at baseline and serially during the course of treatment. QEEG measures included coherence (a measure of synchronized activity between brain regions) and cordance (a measure strongly associated with regional cerebral perfusion). RESULTS: Depressed patients have been reported to have larger volumes of white-matter lesions than controls. We have found that some types of white-matter lesions are associated with lower coherence and that subjects with low coherence had significantly poorer outcomes of treatment for depression at 2-year follow-up. Depressed subjects had low cordance at baseline, which decreased further during the course of effective treatment. Subjects who did not improve had little or no change in cordance. Changes in cordance were detected prior to the onset of clinical response, with decreases seen as early as 48 hours after the initiation of treatment in subjects who showed eventual response. CONCLUSION: These preliminary results suggest that functional imaging using QEEG may be useful for assessing, and possibly predicting, outcomes of treatment for depression.

Antidepressive Agents↗
PubMed1996

Functional magnetic resonance imaging reveals brain regions mediating the response to resistive expiratory loads in humans.

Obstructive lung disease is the most common form of respiratory disturbance. However, the location of brain structures underlying the ventilatory response to resistive expiratory loads is unknown in humans. To study this issue, midsagittal magnetic resonance images were acquired in eight healthy volunteers before and after application of a moderate resistive expiratory load (30 cmH2O/liter/s), using functional magnetic resonance imaging (fMRI) strategies (1.5-T magnetic resonance; repetition time: 72 ms; echo time: 45 ms; flip angle: 30 degrees; field of view: 26 cm; slice thickness: 5 mm; 128 x 256 x 1 number of excitations). Digital image subtractions and region of interest analyses revealed significant increases in fMRI signal intensity in discrete areas of the ventral medulla, ventral and dorsal pontomedullary structures, basal forebrain, and cerebellum. Upon load withdrawal, a rapid fMRI signal off-transient occurred in all activated sites. Application of an identical load immediately after recovery from the initial stimulus resulted in smaller signal increases (P < 0.02). Prolongation of load duration was associated with progressive fMRI signal decrease across activated regions. In three additional subjects, the threshold for significant MRI signal increases was established at expiratory loads > or = 15 cmH2O/liter/s and was dose dependent with increasing loads. We conclude that resistive expiratory loads > or = 15 cmH2O/liter/s elicit regional activation of discrete brain locations in humans.

Adult↗
PubMed1996

Effect of conversion from a fee-for-service plan to a capitation reimbursement system on a circumscribed outpatient radiology practice of 20,000 persons.

PURPOSE: To assess the effect of a capitation reimbursement plan with attendant changes in service arrangements on the utilization of radiologic services, financially on the payer, and on the satisfaction of patients and referring physicians. MATERIALS AND METHODS: Outpatient radiologic services for a defined population of 20,000 company employees and their dependents were converted from a point-of-service managed care plan to a capitation payment plan. Under the capitation plan, nonemergent outpatient diagnostic imaging was performed at a newly constructed imaging center staffed by general radiologists. All cross-sectional images and certain projectional studies were also over-read (read again after the initial reading by local radiologists) by subspecialists. Utilization data obtained before and after the conversion were analyzed. The financial effect on the employer and the satisfaction of patients and physicians were also assessed. RESULTS: Quality imaging services were provided under the capitation plan with financial savings by the employer. Use was higher for cross-sectional imaging, especially magnetic resonance imaging studies, and was lower for nonmammographic plain radiography. Consumer satisfaction was high. CONCLUSION: Under certain conditions, conversion to a capitation system for imaging can lead to improved quality of care and decreased overall health-care costs.

Ambulatory Care↗
PubMed1996

Interventional magnetic resonance imaging of the head and neck and new imaging techniques.

The use of magnetic resonance imaging to directly guide therapy is a new area of investigation. Clinical magnetic resonance imaging has the potential to evolve from a purely diagnostic tool into a guide for invasive procedures. The idea of using magnetic resonance to guide percutaneous biopsy developed one decade ago. Magnetic resonance-guided fine-needle aspiration for head and neck lesions has become a standard technique some institutions. Once the needle reaches a lesion in the head and neck, it is natural to explore the possibility of treatment in the same setting. The concept of interventional magnetic resonance imaging has generated interest among radiologists, surgeons, and manufacturers. This article provides an overview of interventional procedures of the head and neck and other new imaging techniques that have been developed.

Head and Neck Neoplasms↗