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Biomedical subjects

R Lufkin

Publications and source records attributed to R Lufkin.

At least 19 recordsLinked to original sources
PubMed1995

Early postoperative appearance of radiofrequency lesions on magnetic resonance imaging.

Eleven patients who underwent stereotactic radiofrequency lesions in the central nervous system had magnetic resonance imaging follow-up within 72 hours of surgery to determine the early appearance of their lesions. Eight patients with severe tremor, one with chronic pain, and two with dystonia were analyzed. There were six female patients and five male patients, age 7 to 75 years (mean +/- standard deviation = 42 +/- 21). Magnetic resonance imaging was performed postoperatively at 32 +/- 25 hours (range, 3-72). Postoperative T1-weighted spin echo images demonstrated foci of iso- to hyperintensity surrounded by an edge of hypointensity, and corresponding T2-weighted images showed a lesion with three concentric zones consisting of inner hypointense, middle hyperintense, and outer hypointense zones. Gadolinium increased T1-weighted image lesion visibility, and a ring of enhancement around the zone of hypointensity was observed. Lesions could be seen as early as 3 hours after surgery. The lesions were best shown on gadolinium-enhanced T1-weighted images and on T2-weighted images. The edema surrounding the lesion increased over time, up to the 72 hours studied. These data provide important information on the development of lesion appearance, which may be applied in the development of real-time magnetic resonance imaging monitoring of radiofrequency lesion formation. This technique associated with electrophysiological response and the real-time visualization of the anatomic correlation of the probe may allow for a very precise and selected lesion in the central nervous system for the treatment of functional disorders and brain tumors.

Adolescent↗
PubMed1995

Dynamic MRI-guided interstitial laser therapy: a new technique for minimally invasive surgery.

Interstitial laser therapy (ILT) is a promising therapeutic technique in which laser energy is delivered percutaneously to various depths in tissue. In this study, the authors compared high-speed magnetic resonance imaging (MRI) of ILT in tissues during treatment with post-treatment histopathologic specimens. The use of 5-second MRI scans allowed detection of thermal damage by the 1064-nm neodymium:yttrium-aluminum-garnet laser in ex vivo liver and brain tissues. These tissues were treated by ILT with 20 W of laser output for 5 to 30 seconds via a 600-microns fiberoptic inserted 1 cm into the specimens at a power density of 7 kW/cm2 at the tip of the bare fiber. Sequential MRI measurements of lesion areas made during and after treatment were compared to measurements of laser-induced tissue damage in histopathologic sections. Fast MRI scans and tissue histology both demonstrated increased lesion size with time of ILT. Serial images obtained during ILT detected thermal changes as areas of low signal intensity that exceeded the size of the post-treatment lesions as measured on either final MRI or histology. The thermal effects detectable by these high-speed MRI sequences can be used to monitor laser-induced tissue changes during therapy, thereby providing a valuable noninvasive method for the intraoperative assessment of heat distribution during ILT.

Animals↗
PubMed1995

Preliminary experience with MR-guided thermal ablation of brain tumors.

PURPOSE: To evaluate the feasibility of a technique of MR-guided stereotactic radio frequency ablation, which was developed as a minimally invasive treatment for brain tumors, and to determine MR characteristics and sequential evolution of radio frequency lesions created to ablate brain tumors. METHODS: Fourteen lesions in 12 patients with primary and metastatic brain tumors were treated with this technique and followed for up to 10 months. The stereotactic coordinates of the tumor and the angle of the radio frequency probe were calculated on MR imaging. The radio frequency lesion was generated in the awake patient by increasing the temperature to 80 degrees C within the tumor for 1 minute. This was repeated until the entire tumor volume was destroyed. MR imaging was performed before, during, and immediately after the radio frequency procedure, and sequential MR was obtained during clinical follow-up. RESULTS: MR imaging clearly showed well-defined radio frequency lesions and provided feedback for treatment planning. The radio frequency lesion boundary was well identified as a dark signal rim on T2-weighted images and showed ring enhancement on contrast-enhanced T1-weighted images. The sequential MR imaging showed the radio frequency lesions decreased in volume in all cases, suggesting focal control. CONCLUSION: Stereotactic MR-guided radio frequency brain tumor ablation is a feasible and promising technique that can be an attractive brain tumor treatment alternative. MR provided not only accurate tumor location but also visualization of feedback of thermal tissue changes that reflected therapeutic effect.

Adenocarcinoma↗
PubMed1994

Somatosensory evoked response source localization using actual cortical surface as the spatial constraint.

We localized right median nerve somatosensory evoked responses in a normal human subject using an equivalent dipole method applied to magnetic field recordings. High resolution, 3-dimensional MRI data were used to confine source locations to the cortical surface. Results localized in Brodmann area 3b corresponding to location of hand somatosensory cortex derived from direct brain stimulation studies. The solution was unique and total computational time for an exhaustive, brute-force search was small and the results realistic due to applied anatomical constraints. This study demonstrates feasibility of accurate, non-invasive, realistic localization of dynamic human cortical function using spatial constraints provided by MRI images.

Adult↗
PubMed1992

Activity of medial mesopontine units during cataplexy and sleep-waking states in the narcoleptic dog.

Narcolepsy has been hypothesized to be a disease of rapid eye movement (REM) sleep. According to this hypothesis, cataplexy is a result of the triggering during waking of the mechanism that normally serves to suppress muscle tone in REM sleep. REM sleep control mechanisms have been localized to the pons. Narcoleptic dogs have increased numbers of cholinergic receptors in the medial pons. These findings suggest that neurons mediating the triggering of cataplexy might be located in medial pontine regions. In the present study, this hypothesis has been investigated by recording the discharge of units in the medial mesopontine region of the narcoleptic dog. Unit activity was examined in the nucleus reticularis pontis oralis, caudalis, and central gray, with each cell being recorded during both cataplexy and sleep states. Maximal discharge rates were observed, in all of these regions, during active waking states (mean rate, 45.3/sec) and REM sleep (16.0/sec), with minimal discharge rates in non-REM sleep (8.3/sec). Unit discharge was reduced in cataplexy relative to precataplexy periods. Cataplexy discharge rates were 8.3/sec, 52% of the mean REM sleep rate. Cataplexy discharge rates were also significantly lower than those at REM sleep onset. Cataplexy discharge rates were comparable to rates in quiet waking and non-REM sleep. While medial mesopontine neurons discharge at high rates in REM sleep, they have little or no activity in cataplexy. We interpret the lack of activation of medial mesopontine units in cataplexy as indicating that the characteristic phasic motor activation of REM sleep does not occur in this state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Advances in medical imaging.

The field of medical imaging, stimulated by advances in digital and communication technologies, has grown tremendously. New imaging techniques that reveal greater anatomical detail are available in most diagnostic radiology departments. We discuss vascular imaging with ultrasound, high-resolution computed tomography of the thorax, magnetic resonance imaging applications, and picture archiving and communication systems. Vascular imaging with ultrasound requires duplex and color flow Doppler, which combine gray-scale ultrasound and the Doppler phenomenon. High-resolution computed tomography modifies conventional computed tomography technology and results in images with higher spatial resolution. Magnetic resonance imaging applications for all areas of the body are being investigated and are replacing older roentgenographic techniques such as computed tomography, arthrography, myelography, and even angiography in a growing number of indications. With these new digital imaging modalities, image management has become an important consideration that can be addressed by picture archiving and communication systems.

Diagnostic Imaging↗
PubMed1990

MR of the paranasal sinuses.

The purpose of this project was to examine the anatomy and pathology of the paranasal sinuses as seen by MR imaging. This was accomplished through correlations of MR images of normal volunteers with matched cadaver whole organ cryosections. The information obtained by MRI was compared to that of plain films and CT in the detection of a variety of conditions affecting the paranasal sinuses. The majority of the pathological processes could be quite adequately imaged by T1 weighted pulsing sequences. When more tissue specific information was required in some infiltrating malignant lesions, T2 weighting pulsing sequences are quite helpful for tumors that crossed the subarachnoid space into the central nervous system or in characterizing tissues in airless sinuses. Other than the single case of osteoid osteoma where X-ray studies were superior, magnetic resonance provided equal or superior information to the X-ray examinations.

Cadaver↗
PubMed1990

The use of MRI in the identification of post-traumatic laryngeal deformities.

Suspected post-traumatic deformity of the laryngeal cartilages can be diagnosed by using current magnetic resonance imaging (MRI) scanning techniques. This is of particular aid to the clinician who is evaluating a laryngeal mass with no history of injury to the neck. Computed tomography (CT) and magnetic resonance imaging are both effective in this situation, but MRI appreciates better soft tissue contrast, and can offer coronal and sagittal views.

Aged↗
PubMed1990

Multimodality imaging of brain structures for stereotactic surgery.

An image analysis system was developed for stereotactic neurosurgery that allows the simultaneous display of brain images from different imaging devices obtained in different orientations. The system is based on a stereotactic frame and a microcomputer and features an easy user interface together with point registration and region of interest analysis in three-dimensional space. A dynamic multi-image environment allows for simultaneous display of magnetic resonance, computed tomography, digital subtraction angiography, and positron emission tomography images in multiple windows, adjusted for common coordinates with reference to stereotactic frame fiducial markers. Linkages between images allow information interchange between different modalities and different views: Points and regions defined in one image can be transferred to others, and cursor coordinates in one image can be calculated and dynamically projected in other images. Phantom studies show that the system distortions are minor and that the system is suitable for clinical use. The system provides exceptional advantages over previous imaging procedures for stereotactic surgery.

Angiography, Digital Subtraction↗
PubMed1989

Neurovascular lesions and endovascular therapy: the role of MR.

Magnetic resonance imaging (MRI) studies were performed on 27 patients with vascular lesions of the central nervous system before and after embolization with either IBCA, polyvinyl alcohol foam particles, Avitene (microfibrillar collagen) or balloons. Thirteen pial brain arteriovenous malformations (AVMs), 3 brain AV fistulas, 2 giant aneurysms, 5 dural AVMs, 1 vertebro-vertebral fistula and 3 meningiomas were studied. The pre-embolization MR demonstrated the nidus and venous drainage of all pial AVMs. MR failed to detect 3 out of 5 dural AVMs using only spin echo sequences. A draining vein alone was seen in the remaining two cases. MR was superior to CT in detecting contiguous parenchymal changes such as atrophy, reversible ischemia, and mass effect in the pre-embolization studies. Following embolization, MR demonstrated partial or complete obliteration of the vascular nidus in all 13 pial AVMs. The embolized area was seen as an area of increased signal consistent with thrombus where previously there had been signal void. Ischemic or edematous changes in the brain parenchyma following embolization were seen on MR more easily than on CT scans. MR was accurate in the assessment of aneurysm patency, degree of thrombosis and balloon position in both giant aneurysms, and AV fistulae. These MR findings had an impact on patient management. MR will be an increasingly useful tool in the diagnosis and management of a number of neurovascular diseases requiring endovascular intervention.

Arteriovenous Malformations↗