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W D Erwin

Publications and source records attributed to W D Erwin.

35 records · Page 2Linked to original sources
PubMed1991

Truncation artifact: a potential pitfall in MR imaging of the menisci of the knee.

Because truncation artifacts on magnetic resonance (MR) images may be confused with meniscal tears, measures to suppress them were investigated in a human cadaver knee and prospective and retrospective studies of patients. The artifacts were most prominent when the acquisition matrix was 128 x 256 and the 128-pixel (phase-encoded) axis was in a superoinferior (SI) orientation. An anteroposterior (AP) orientation of the 128-pixel axis or use of a 256 x 256 acquisition matrix reduced the prominence of or nearly eliminated the artifacts. A review of reports of MR imaging and arthroscopic examinations of 83 knees yielded eight menisci that were falsely interpreted at MR imaging as having tears. Retrospective review of the images suggested that the errors were due to truncation artifacts in two cases. Truncation artifacts will cause relatively little difficulty if diagnostic observers are aware of their characteristics and simple steps are taken to minimize their prominence, including acquiring images in 192 x 256 or 256 x 256 matrices or AP rather than SI orientation of the phase-encoded (128-pixel) axis of 128 x 256 matrices.

Autopsy↗
PubMed1991

Alpha 2-adrenergic model of gastroparesis: validation with renzapride, a stimulator of motility.

Motility-stimulating drugs can increase gastric antral and intestinal contractions but do not usually enhance emptying unless gastroparesis is present. An alpha 2-adrenergic agonist (SC-39585A) was used to inhibit antroduodenal motility and simulate gastroparesis in dogs. SC-39585A caused dose-related inhibition of emptying of solid and liquid meals as well as the antral and duodenal motility responses to the solid meal. The motility-enhancing agent renzapride (100 micrograms/kg iv) did not enhance emptying of the solid meal under nondelayed conditions. However, at the same dose it partially reversed the delay in solid emptying but only when antroduodenal motility was incompletely (30 micrograms/kg sc) and not totally (100 micrograms/kg sc) inhibited by SC-39585A. This was done in part by antagonizing antral but not duodenal inhibition of motility. Renzapride was also effective orally in reversing the delay in solid emptying. Similarly, renzapride reversed the delay in liquid emptying caused by SC-39585A (30 micrograms/kg sc). An alpha 2-adrenergic agonist can be used to model gastroparesis in dogs by inhibiting antroduodenal motility and can also be used to examine the actions of motor stimulants, such as renzapride, which promote gastric emptying.

Adrenergic alpha-Agonists↗
PubMed1991

Multigated blood-pool imaging using heart sounds.

A method to trigger multigated blood-pool (MGBP) acquisition using both the first and second heart sound has been developed. The heart sound gating (HSG) circuitry identifies, individually, both the first (S1) and second (S2) heart sounds from their timing relationship alone, and provides two trigger points during the cardiac cycle. First heart sound gating may be performed to assess the systolic ejection portion of the cardiac cycle, with S2 gating utilized for reproduction of the diastolic filling portion of the cycle. Heart sound gating has been applied to twenty patients who underwent analysis of left ventricular function, and compared to conventional ECG-gated MGBP. Left ventricular ejection fractions calculated from MGBP studies using a first and a second heart sound trigger correlated well with conventional ECG gated acquisitions in patients adequately gated by HSG and ECG. Heart sound gating may be utilized in patients with rapidly changing heart rates, as S1 and S2 precisely define end-diastole and end-systole, respectively, and in situations when the ECG is inadequate for gating purposes.

Electrocardiography↗
PubMed1990

Harrington instrumentation and arthrodesis for idiopathic scoliosis. A twenty-one-year follow-up.

A questionnaire was sent to 206 consecutive patients who were operated on for idiopathic scoliosis by Dr. Paul R. Harrington between 1961 and 1963. Eighty-three per cent of the patients responded to the questionnaire, which consisted of five sections: demographic data, activities of daily living, back symptoms (pain and fatigue), a history of personal and family health, and a personal assessment of the back. One hundred and eleven patients also sent recent radiographs. A control group, comprising 100 individuals who did not have scoliosis and had been matched for age and sex, was given the same questionnaire. The study group had more pain in the interscapular and thoracolumbar regions compared with the control group, but there was no difference with respect to pain in the lumbosacral area or the low back. Neither pain nor fatigue was related to the type of curve, the preoperative degree of curvature, the degree of curvature as seen on the most recent radiograph, the extent of fusion into the lumbar spine, or the presence of a broken rod. Twenty-one years after the operation, the patients were functioning quite well compared with the control subjects.

Activities of Daily Living↗
PubMed1985

Dual-isotope motion correction technique for gated exercise scintigraphy.

In exercise multigated blood-pool imaging, significant degradation of image quality occurs as a result of patient movement under the gamma camera. Motion correction devices using centroid tracking of x-y events emanating from the organ of interest cannot be applied to blood-pool studies, because cardiac contraction and rotation masks the correctable patient motion component. We have developed a dual-isotope motion correction technique (DIMC) which utilizes a second point source of dissimilar energy (241Am) to monitor movement. Positional centroids from events incident in the 241Am window are used to develop correction coordinates which are applied to the 99mTc blood-pool events. The ability of DIMC to reduce blur due to motion has been evaluated qualitatively with phantoms and quantitatively by using spatial resolution measurements obtained from stationary line sources and from sources moving at varying rates. Based on these criteria, we have found the device to be capable of reducing over 90% of the image blur of objects moving at 5.1 cm per sec. In preliminary gated exercise studies, subjective perception of image quality was shown to be significantly improved in the DIMC corrected image, when compared to images obtained without DIMC. Improvement in image quality for exercise gated studies is of particular importance because of the low count density obtained during these procedures.

Americium↗
PubMed1980

Clinical review of patients with broken Harrington rods.

The medical records and roentgenograms of 2,016 patients who were operated on from 1961 through 1974 using Harrington spinal instrumentation were reviewed to determine the incidence, clinical significance, and management of broken distraction and compression rods. The cases were divided into two study groups. Group A includes 1,128 patients operated on from 1961 through 1968, when no autogenous iliac-bone graft material was used, and Group B includes 888 patients operated on from 1969 through 1974, when autogenous bone was used. The incidence of broken distraction rods was 12.5 per cent (141 patients) in Group A and 2.1 per cent (nineteen patients) in Group B. The age of the patient at operation was not found to be a significant factor when comparing patients with fractured rods and those with intact rods; however, preoperative curve magnitude was found to influence the incidence of rod fractures. Reinstrumentation of distraction rods was required in twenty-three patients from Group A, but no patients in Group B required reinstrumentation. Eleven patients from Group A required removal of the rods. The compression rod fractured in forty patients (3.5 per cent) in Group A and in one patient in Group B; none required reinstrumentation or rod removal. The clinical management of rod fractures must be individualized for each patient. Reinstrumentation and fusion may be indicated in patients with early rod fracture, total loss of correction, or overlapping of the rod, but not in patients experiencing little or no loss of correction and no associated symptoms.

Adolescent↗
PubMed1979

Results of Harrington instrumentation in the treatment for severe scoliosis.

Between July 1963 and December 1974, we surgically treated 207 patients who had severe scoliosis (curves greater than 90 degrees), 196 of whom were eligible for inclusion in this study. No patient was treated preoperatively with a cast or traction. Upon statistical analysis, age and preoperative curve magnitude proved to be significant variables relative to the amount of surgical correction obtained and the maintenance of that correction; sex and etiology of the scoliosis were not shown to affect either surgical outcome or maintenance of correction. A comparative analysis showed our results to be as good as those reported by others using various preoperative regimens of casting or traction or both. Therefore, we find that the preoperative application of traction to patients with severe scoliosis yields no better correction than the use of Harrington instrumentation and fusion alone.

Adolescent↗
PubMed1978

Results of reduction and stabilization of the severely fractured thoracic and lumbar spine.

From 1962 to 1976, ninety-five patients with fracture-dislocations of the spine were treated with Harrington instrumentation and fusion within ninety days of injury. This report presents the results of this procedure related to reduction, stabilization, return of neural function, and total hospital stay. Mean follow-up was twenty-one months. Reduction and stabilization were attained without a substantial number of complications, but no more return of neural function in the patients was evident than has been reported in the literature for patients treated with postural reduction and bed rest. Total hospital stay averaged 107 days from day of injury.

Adolescent↗
PubMed1976

The postoperative management of scoliosis patients treated with Harrington instrumentation and fusion.

A retrospective study of maintenance of correction as affected by modifications in the management of patients surgically treated for scoliosis showed better results in Group B than in Group A. No supplementary bone was used in the 187 patients in Group A, who were maintained recumbent for three months postoperatively and who wore an underarm body cast for six months. The 177 patients in Group B received autogenous iliac-bone grafts, were allowed to walk seven to ten days postoperatively, and wore an underarm body cast for nine months. By two years postoperatively the patients in Group A had lost an average of 8.3 degrees of correction, and the patients in Group B had lost 4.3 degrees. A pseudarthrosis developed in eight patients in Group A and in one patient in Group B.

Adolescent↗
PubMed1975

Results of Harrington instrumentation and fusion in the adult idiopathic scoliosis patient.

Between January 1961 and December 1972, 132 patients over twenty years old with idiopathic scoliosis were surgically treated using Harrington instrumentation and fusion techniques. All patients were seen by us because of curve magnitude or symptoms secondary to scoliosis. The average correction obtained at operation was 48 per cent. Twenty-four patients had early complications. Fifty-two had late complications, the most frequent of which was pseudarthrosis. The majority of patients had significant improvement in symptoms as a result of surgical correction and stabilization.

Adult↗
PubMedDate not supplied

Respiratory gating in magnetic resonance imaging: improved image quality over non-gated images for equal scan time.

Magnetic resonance image quality is adversely affected by respiratory (RESP) motion during the scan. Respiratory gating improves magnetic resonance image (MRI) quality and removes artifacts, but has not been widely used, as RESP gating increases scan time. Our RESP-gating device was used to study scan time versus improvement in image quality using various gating modes; with and without combined electrocardiographic (ECG) gating. When RESP scans were acquired for the same time as non-gated scans, by using a wide RESP-gating window bracketing end expiration and a reduced number of pulse sequence repetitions, substantial improvement in image quality (over non-gated scans) resulted, despite the inferior statistical content of the acquisition.

Abdomen↗
PubMedDate not supplied

Biodistribution and dosimetry results from a phase III prospectively randomized controlled trial of Zevalin radioimmunotherapy for low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma.

UNLABELLED: Radiation dosimetry studies were performed in patients with non-Hodgkin's lymphoma (NHL) treated with 90Y Zevalin (90yttrium ibritumomab tiuxetan, IDEC-Y2B8) on a Phase III open-label prospectively randomized multicenter trial. The trial was designed to evaluate the efficacy and safety of 90Y Zevalin radioimmunotherapy compared to rituximab (Rituxan, MabThera) immunotherapy for patients with relapsed or refractory low-grade, follicular, or transformed NHL. An important secondary objective was to determine if radiation dosimetry prior to 90Y Zevalin administration is required for safe treatment in this patient population. METHODS: Patients randomized into the Zevalin arm were given a tracer dose of 5 mCi (185 MBq) (111)In Zevalin (111indium ibritumomab tiuxetan) on Day 0, evaluated with dosimetry, and then administered a therapeutic dose of 0.4 mCi/kg (15 MBq/kg) 90Y Zevalin on Day 7. Both Zevalin doses were preceded by an infusion of 250 mg/m(2) rituximab to clear peripheral B-cells and improve Zevalin biodistribution. Following administration of (111)In Zevalin, serial anterior and posterior whole-body scans were acquired and blood samples were obtained. Residence times for 90Y were estimated for major organs, and the MIRDOSE3 computer software program was used to calculate organ-specific and total body radiation absorbed dose. Patients randomized into the rituximab arm received a standard course of rituximab immunotherapy (375 mg/m(2) weekly x 4). RESULTS: In a prospectively defined 90 patient interim analysis, the overall response rate was 80% for Zevalin vs. 44% for rituximab. For all patients with Zevalin dosimetry data (N=72), radiation absorbed doses were estimated to be below the protocol-defined upper limits of 300 cGy to red marrow and 2000 cGy to normal organs. The median estimated radiation absorbed doses were 71 cGy to red marrow (range: 18-221 cGy), 216 cGy to lungs (94-457 cGy), 532 cGy to liver (range: 234-1856 cGy), 848 cGy to spleen (range: 76-1902 cGy), 15 cGy to kidneys (0.27-76 cGy) and 1484 cGy to tumor (range: 61-24274 cGy). Toxicity was primarily hematologic, transient, and reversible. The severity of hematologic nadir did not correlate with estimates of effective half-life (half-life) or residence time of 90Y in blood, or radiation absorbed dose to the red marrow or total body. CONCLUSION: 90Y Zevalin administered to NHL patients at non-myeloablative maximum tolerated doses delivers acceptable radiation absorbed doses to uninvolved organs. Lack of correlation between dosimetric or pharmacokinetic parameters and the severity of hematologic nadir suggest that hematologic toxicity is more dependent on bone marrow reserve in this heavily pre-treated population. Based on these findings, it is safe to administer 90Y Zevalin in this defined patient population without pre-treatment (111)In-based radiation dosimetry.

Antibodies, Monoclonal↗
PubMedDate not supplied

Quantitative gated blood pool SPECT for the assessment of coronary artery disease at rest.

BACKGROUND: Planar gated blood pool imaging (GBPI) has long proven to be useful for the noninvasive assessment of ventricular function. From a practical viewpoint, gated blood pool single photon emission computed tomography (GBPS) acquisition can be accomplished in the same time as a three-view planar series, with the benefit of a tomographic perspective that avoids chamber overlap. METHODS AND RESULTS: Quantitative gated blood pool SPECT was applied to 10 patients who underwent coronary arteriography, contrast ventriculography, and planar gated blood pool imaging. For each patient, the mid-short axis oblique slice was divided into 4 discrete segments using 4 different reference models and 2 forms of segmentation. A center of mass (counts) fixed in the end-diastolic frame and segmentation that bisected the ventricular septum proved to have the highest sensitivity and specificity for determining regional wall motion abnormalities at rest in myocardium supplied by severely diseased coronary arteries (>75 %). GBPS correctly identified 19 of 21 abnormal segments (90%), with good specificity (95%), whereas ventriculography identified 12 (57%) and planar GBPI identified 9 (43%) of the segments supplied by diseased coronaries. CONCLUSION: Quantitative GBPS appears to be a sensitive method for assessing coronary artery disease at rest in myocardium perfused by severely diseased coronary arteries.

Aged↗